JP2006021106A - Method and apparatus for desalting novel perfect total nf thermal seawater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a seawater desalting method having much higher yield and product recovery rate than commonly used thermal seawater desalting method, and a seawater desalting apparatus. <P>SOLUTION: Salt water is made to pass through a two-stage membrane nano filtration (NF2) unit, where an energy recovering turbo-charger unit is disposed between stages and, if necessary, a booster pump is added. A first water product is made by mixing NF (nano-filtration) products from the first and second stages, made from an NF unit having the booster pump between the stages, or made from an NF unit having an energy recovering pressure exchanger. The NF unit comprises two stages between which the booster pump is disposed. In the first water product, the content of ionic species is reduced, and microorganisms, particulate matter, and almost all of scale-forming hard ions are removed. The first water product is then made to pass through a thermal seawater desalting unit to generate a final second water product and a brine discharge matter. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermal seawater desalination process.

Typically, the process of the present invention using a two-stage NF ₂ initial pretreatment step performs a semi-desalting step by reducing the feed TDS by about 35-50%, but most importantly the thermal process Compared to seawater desalination, more than 80% of Ca ⁺⁺ and Mg ⁺⁺ scale-forming hard ions that restrict water recovery, and 95% of their sulfate covalent anions More, remove bicarbonate ions to about 65%. Scale forming hardness ions, in particular the removal of SO ₄ ⁼ and bicarbonate ions, a thermal unit in the hybrid, the current maximum brine temperature (top brine temperature) of 120 ° C. by conventional sole method for MSFD ( Allowing operation at a TBT much higher than the TBT) limit, allowing operation of MED or VCD or RH units at a TBT much higher than their current TBT limit of 65-70 ° C., This method provides many advantages over conventional seawater desalination methods. The method of the present invention provides not only water yield, product water recovery, and unit water cost, but also per product unit quantity equal to or less than other effective conventional seawater thermal desalination processes. It is more efficient than all conventional thermal seawater desalination methods. This method achieves 75 and 80% or higher NF product recovery from high salinity Gulf seawater (TDS≈45,000 ppm), which can be generated from SWRO or thermal units. When operating on water, approximately the same, with a total water recovery rate of over 52% for seawater feed with a TDS of 45,000 ppm and a greater water recovery rate from ocean seawater (TDS≈35,000 ppm) Product recovery is also obtained. In the case of a trihybrid, this recovery is further increased by about 8-10% when the waste from the SWRO is fed to the thermal unit, and the recovery of the triple hybrid for the gulf seawater feed. The total water recovery rate is about 60%, resulting in even greater values from ocean seawater supplies.

Highest recovery double and triple fully integrated NF-thermal seawater desalination process The term "thermal" refers to MSFD, or MED, or VCD, or a combination of conventional seawater desalination processes. Either means within a unit of a thermal steam compressor / multi-effect evaporator, also known as a reheat (RH) distillation system. The method of the present invention, all double NF ₂ - thermal type hybrid, and _NF 2 -SWRO ₂ (elimination thereof) - thermal, or _NF 2 -SWRO ₁ (elimination thereof) - all constructed from thermal Including a triple hybrid, in this case a dual fully integrated system configuration, where the combined NF ₂ products from the two NF stages constitute a make-up to the thermal unit In the case of a fully integrated triple hybrid, the reject from the SWRO ₂ second stage unit supplied with NF product, or the reject from the SWRO ₁ unit constitutes a supplement to the thermal unit To do.

The present invention provides an effective NF with the maximum possible water recovery currently available with thermal seawater desalination from pre-treated seawater feeds, or coastal well seawater feeds, or other aqueous solution feeds. _With respect to the ₂ -thermal method, the feed in this case is a high concentration of (1) TDS on the order of 20,000 to 50,000 ppm, and (2) scale-forming hard ions as shown in Table 1 (ie , SO ₄ ⁼ , Ca ⁺⁺ , Mg ⁺⁺ , and HCO ₃ ⁻ ), in addition, (3) it contains some turbidity and bacteria. This is accomplished by deploying and operating an energy recovery turbocharger between two stages of equipment with or without an NF unit and scale prevention system as two fully integrated continuous stages. . Depending on the type of NF membrane, the first stage NF unit is operated on seawater at the pressure (P) given by the pressure pump at P = 25 ± 10 bar, and the second stage is about 35 ± 10 bar at the first NF Operated on the exclusion from the stage. In this case, the pressure is increased by the energy recovered from the (second stage) reject by the turbocharger. In the case of a triple hybrid, the SWRO unit is deployed in one or two stages, with an energy recovery turbocharger before and between the one stage system, or using two or one SWRO stages. In that case, it is operated at those stages with an energy recovery PX unit.

As shown in a later section, seawater pretreatment by NF units (1) removes turbidity from seawater to prevent the occurrence of contamination and biological contamination, (2) reduces the TDS of NF products, 3) Remove scale-forming hard ions of SO ₄ ⁼ , HCO ₃ ⁻ , Mg ⁺⁺ , and Ca ⁺⁺ to prevent the formation of scale, thereby allowing a thermal unit (any of the thermal units defined above) Give results that make it possible to operate at a temperature limit much higher than the maximum brine temperature limit previously possible, eg, the TBT limit of MSFD that has been conventionally operated is 120 ° C., MED or Only 65-70 ° C for VCD or RH operation. Exclusions from SWRO units fed with NF products are characterized by many of the above quantities as NF products and are very low in concentration without turbidity, but harder at higher concentrations than in NF products. It contains ions, making it a very good and suitable supplement to a seawater thermal unit, allowing it to operate at a much higher TBT than previously possible.

With this optimal method, for example, about 25 to 35% of conventional thermal or SWRO process recovery rates when applied to Gulf or Red Sea water (TDS≈45,000 ppm) can be achieved. ₂ - it is possible to increase to approximately 70% by thermal or SWRO ₂ method. NF ₂ - The system configuration as in the case of thermal or _NF 2 -SWRO ₂ method, for example, when the Gulf seawater (feed TDS ≒ 43-45000ppm), NF ₂ - thermal or _NF 2 -SWRO ₂ units The total water recovery rate due to both is given by more than 52% compared with only 25-35% by the conventional thermal or SWRO desalting method, and the water recovery rate increases in the range of 50% -100% Which is larger than that of our fully integrated NF-SWRO method developed previously. In this case, each of NF and SWRO consisted of only one single stage without an energy recovery system [Hassan A. et al. M.M. No. 6,508,936, Jan. 21, 2003]. This optimal seawater desalination method reduces both the energy required per unit water volume and the cost of water generation.

The same additional advantages are obtained by operating the seawater desalination plant as triple NF ₂ -SWRO ₂ eliminator-thermal or NF ₂ -SWRO ₁ eliminator-thermal hybrid, where the thermal unit is SWRO It operates on replenishers made up of exclusions from the unit, the latter unit now operating on the NF product. Again, the thermal unit is currently operating at a TBT that is much higher than the conventional TBT limit. In this mode of operation, both the permeate of SWRO ₂ or SWRO ₁ and the thermal unit product distillate have drinking water quality and if the feed consists of Gulf Seawater (TDS≈45,000 ppm), about 52% or more It is produced at a higher yield and water recovery rate of about 60% or more, which is about 8-10% higher than the double hybrid ratio.

  In many countries, desalination of salt water, particularly sea water, has been considered as a fresh water source for dry coastal areas, or areas where the water source is salty or has excessive hardness. Typical areas where desalination is considered or used include the Gulf States and other Middle Eastern countries: Southern California in the United States; Mediterranean Arab countries in Libya, Algeria, and Egypt; Europe, primarily Spain, Includes Malta and Cyprus; Pacific countries in Mexico and South America. Similarly, islands with limited fresh water supplies, such as Malta, the Canary Islands, and the Caribbean, use and consider seawater desalination as a source of fresh water. Currently, fresh water from the sea accounts for over 70% of drinking water in Saudi Arabia and the Emirates. In both Kuwait and Qatar, almost 100% of drinking water is derived from desalted seawater.

  The conventional commercial SWRO desalination process pre-treats the feed, removes turbidity, primarily suspended matter and bacteria, adds a scale inhibitor, usually an acid, and then this pre-treated feed. Is passed through a SWRO membrane at a high pressure of 55-82 bar (800-1200 psi) to separate the feed stream into product (permeate) and reject (concentrate). In many older SWRO plants, another second stage salty water RO unit is deployed to reduce the salinity of the product from the first stage SWRO unit to standard drinking water salinity. This conventional method used in many plants built in the early days (until the mid-1990s) is known for the high energy required per unit of desalted water product, Low yields, typically 25% to 35% or less from Gulf Seawater using two-stage SWRO units, have been operated below that using one-stage SWRO. This low water recovery rate also applies to thermal processes such as multistage flash distillation and multi-effect distillation units that are operated on Gulf seawater. Therefore, they were economically viable only for areas where freshwater shortages were serious, energy was available, and their costs were considered low (although artificial). Desalination plants have also been used in other areas, such as California, but they are commonly used as standby or supplemental freshwater sources during drought times or when other water sources are temporarily limited or unavailable. Has been. In many areas where there is not much natural water resources available, current desalination methods use other freshwater sources such as onshore pipelines or water pipes from distant rivers and reservoirs as in Southern California. Cannot compete effectively.

  However, because oceans and oceans have vast amounts of water and direct freshwater sources (eg, island rivers, lakes, and groundwater channels) are beginning to be depleted, polluted, and reaching capacity limits, All these factors, combined with the growing population of the world without significant increases in natural water resources, has led to extensive research around the world on economic methods for desalinating salt water, especially sea water. Has been done. In fact, this research is developing towards the ultimate goal of meeting the growing demand for countries experiencing severe water shortages in the present or the future, and in a sense, the fight for water resources Where it exists, it becomes a major factor in spreading peace.

  As previously mentioned, several commercial seawater desalination methods are currently available and in use. Thermal multistage flash distillation is the main desalting method currently used worldwide. Alone, it accounts for about 41% of the global desalination capacity, whereas about 44% is produced by the reverse osmosis (RO) process. The rest (15%) has been obtained by various methods, mainly electrodialysis (ED), multi-effect distillation, and vapor compression distillation (VCD); Wangnick Klaus, 2000 IDA World Desalination Plant Inventory (2000 IDA World Desalting Plants Inventory), Report No. 16. International Desalination Association (May 2000). Saudi Arabia is the primary user of MSFD and the United States is the largest user of RO law. The MSFD, MED, RH, and VCD methods are all used exclusively in seawater desalination, while ED has been applied to salty water desalination and pure water production. However, the RO method is a diversified salt water desalination method. While it applies to both seawater (SWRO) and salty water RO (BWRO) feeds, it has traditionally been applied primarily to the production of salty, drinking and pure water. Recently, however, SWRO desalination has become more common and has been used worldwide, with plants of 39-57 million liters / day (mld) [10-15 million gallons / day (mgd)] or more. A relatively large plant is used.

Seawater desalination must take into account the important properties of seawater itself: (1) species, concentration, and total hard ions, (2) salinity [ion content, total dissolved solids (TDS)], And (3) the presence of turbids, suspended particles and microorganisms as well as other large particles. These properties hinder desalination equipment and determine plant performance (product: yield, recovery, and quality). In particular, hard ions that can only be slightly dissolved give a limit of 25% to 35% or less to the conventional seawater desalination methods, such as freshwater yield values expected from Gulf and Red Sea seawater. As shown in FIG. 1, the seawater desalination method is a separation / concentration method, whether it is a membrane type or a thermal type, and the supply stream is separated into a fresh water product stream and a reject stream with clean drinking water quality. Excluded streams contain high concentrations of contaminants TDS and hard ions, leading to four main problems that occur in seawater desalination processes. These problems are summarized in Figure 2 along with their causes: (1) scale formation, (2) large energy consumption, (3) contamination, (4) increased corrosion. Hard ions have very low solubility, and CaSO ₄ solubility decreases with increasing processing temperature, so increasing the concentration of hard ions in salt water can cause a variety of conventional seawater desorption, whether thermal or membrane. The recovery rate of demineralized water by the salt method is extremely limited (25 to 35% or less).

  This application refers to water referred to as “saline”, which is seawater from the sea, such as seawater from the Gulf, Red Sea, Mediterranean, and oceans, water from various salt lakes and ponds. , Including water from very salty water sources, brines, other surface and ground water sources including ionic inclusions, which are classified as “salt water” as shown in Table 1. ing. Saline can generally be considered water having a salt content of TDS ≧ 20,000 ppm or more. Of course, sea water has the greatest potential as a source of drinking water, so this application focuses on sea water desalination. However, all sources of high salinity, especially hard water, should be considered within the scope of the present invention, and focusing on seawater is for simplicity and limitation. It should be understood that this should not be considered.

  As mentioned earlier, the performance and product recovery of seawater desalination plants (thermal and SWRO plants) are severely limited by the three problems mentioned earlier, all of which are the quality of seawater and its material content. (1) Turbidity, (2) TDS, and (3) Total hard ions in the water feed. If turbidity is present in the feed, it is particularly trapped on the membrane, leading to membrane contamination. Biological contamination occurs when bacteria are also present in the feed along with turbidity, ie total suspended solids (TSS) that nourish the bacteria. In RO, the feed osmotic pressure increases with TDS. From the RO principle, the applied pressure is: (1) partial and needs to be used to exceed the osmotic pressure, and (2) the rest of this applied pressure defined as true pressure (Pnet) Only the pressure that pushes the permeate (product) through the membrane. The lower the osmotic pressure by reducing the feed TDS, the greater the true pressure, and thus the greater the amount of permeate that is forced through the membrane, which also means higher quality products. Provides the additional advantage that arises in (Fig. 3).

  A high content of hard ions that are only slightly soluble in the feed is the biggest obstacle limiting fresh water recovery. This is because increasing the recovery rate beyond the solubility limit of hard ions will cause a more severe scale formation effect and a sharp decline in plant performance. However, scale formation has a more severe effect on the thermal process than occurs with SWRO processes operated at ambient temperature. Since the solubility of calcium sulfate decreases as the operating temperature increases, calcium sulfate deposition becomes a more serious problem for the thermal process than for the SWRO process and becomes significantly larger at higher temperatures.

  In short, the scale formation of seawater desalination plants, together with their large energy consumption and pollution, constitutes three main problems of seawater desalination. Corrosion is the fourth major problem of seawater desalination, and the occurrence of corrosion increases with increasing chloride content and salinity in seawater. The first main object of the present invention is to provide an efficient thermal seawater desalination treatment and method that not only solves these problems, but also results in the establishment of an optimal high efficiency thermal seawater desalination method and apparatus. There is to develop.

Increasing the water recovery rate of a SWRO or thermal seawater desalination plant would reduce unit water generation costs. This is because this unit cost is calculated by dividing the total water production cost by the amount of product. As the water recovery rate increases, the amount of product increases and the unit water cost simply decreases. In the present invention, pretreated seawater feed by NF ₂ film method, as already mentioned above, takes out the hardness ions to restrict the product recovery therefrom. Furthermore, the amount of hard ions that are also contained in the reject from the SWRO ₂ unit operated on the feed consisting of the NF product is very low. In order to increase NF product recovery and plant yield from SWRO or thermal units, the NF unit is operated in two stages. In this manner, the double _NF 2 -SWRO ₂ or NF ₂ - not only SWRO ₂ or thermal unit in thermal, triple _NF 2 -SWRO ₂ elimination product - yield and water from thermal unit of the thermal type Both recovery rates increase to 70-80% for Gulf Seawater (TDS = 43-45000 ppm) and even more for Ocean Seawater Feed (TDS = 35000 ppm). As previously mentioned, the increased water recovery rate according to the present invention is a major advantage of the system of the present invention. This in-development efficiency and water recovery rate outperforms all conventional thermal seawater desalination processes and raises the optimum thermal process TBT limit to values much higher than currently possible with conventional thermal processes. can outside, also thermal unit water recovery from seawater feed increases to the optimal dual NF ₂ - thermal and _NF 2 -SWRO ₂ (elimination thereof) - thermal, or _NF 2 -SWRO ₁ ( Exclusions)-Efforts have been made to develop thermal desalination methods.

  The main objective of the present invention is to maximize plant yield and product water recovery to a much higher yield and product recovery than currently achieved by any of the conventional thermal seawater desalination processes. There is to do.

  This is achieved by combining conventional seawater desalination methods (membrane or thermal) and NF membrane pretreatment together. The following thermal hybrid combination of NF and conventional thermal seawater desalination is encompassed by the present invention:

(1) NF ₂ - thermal (thermal unit, MSFD, or MED, or VCD, or can be RH) of the dual system hybrid (Figure 4).
₍₂₎ NF 2 -SWRO ₂ (elimination thereof) - thermal or _NF 2 -SWRO ₁ (elimination thereof) - thermal triple mechanism hybrid (Fig. 5).
Here, NF ₂ and SWRO ₂ represent two-stage NF and SWRO units, respectively, and each has an energy recovery turbocharger between those stages. The SWRO unit can consist of a single stage high pressure allowable SWRO membrane unit up to 90 bar, with an energy recovery turbocharger or PX first placed between it and the high pressure pump membrane assembly.

However, the dual NF ₂ -SWRO ₂ that can be formed according to the present invention is filed concurrently with this patent application, including only the claims for the dual NF ₂ -SWRO ₂ or NF ₂ -SWRO ₁ hybrid. In another patent application. And NF ₂ -SWRO _2, NF _{2 -} for effects of NF ₂ pretreatment for both thermal are similar, discussion and conclusion are given in both applications, identity and redundancy in some surface It is clear that they are legitimate. However, since one of them is a membrane type while the other is a thermal desalination process, they have been filed separately.

  Traditionally, various types of filtration or flocculation and filtration systems have been used to treat water and other liquid solutions and suspensions to remove particulate matter (Table 2). Addition of scale inhibitors is used to help prevent scale formation. However, despite this conventional pretreatment to remove turbidity and the addition of scale inhibitors to prevent scale formation, freshwater recovery rates are, for example, conventional demineralized bay SWRO (TDS≈45,000 ppm). ) Is still limited to 25 to 35% or less.

  Recent work to remove fine particles with particle sizes smaller than 2 μm uses microfiltration (MF) or ultrafiltration (UF). Low pressure reverse osmosis (LPRO) or salty water RO (BWRO) membranes (see below) have also been used prior to SWRO pretreatment. MF membrane treatment is used to remove particles having a particle size in the range of 0.08 to 2.0 μm. The UF membrane method is more effective in removing finer particles having a particle size in the range of 0.01 to 0.2 μm and a molecular weight (MW) in the range of 10,000 g / mol or more. Both the MF and UF membrane methods are genuine filtration methods, and the separation of the particles is done only by particle size, not by their ionic properties. Furthermore, both MF and UF membranes have their own characteristic pore size and separation limit. These two membrane filtration methods are effective in keeping the feed clean by removing turbidity and bacteria, and as such, can eliminate membrane contamination, including biological contamination, during plant operation. They are very effective pretreatment methods to prevent. The pretreatment method by MF and UF filtration is significantly different from the RO pretreatment. As already mentioned, unlike the MF and UF membrane methods that do not separate or eliminate ions from solution or seawater, the RO method has a particle size of 0.001 μm or less and a molecular weight of 200 g / mol or less. This is a pressure difference method for separating all ionic particles having. In addition, these highly airtight SWRO membranes require operation at high pressures on the order of 50-80 bar, compared to operation at low pressures of only about 5-10 bar in the MF and UF processes. And

Compared to other membrane separation methods, the NF membrane method falls between the separation range of RO and UF, and has a particle size in the range of 0.01 to 0.001 μm and a molecular weight of 200 g / mol or more. Suitable for separation. However, unlike either UF or RO, NF works by three principles: elimination of neutral particles by particle size, elimination of ionic substances by electrostatic interaction with negatively charged membranes; Rautenbach Other, Desalination, 77: 73-84 (1990). Furthermore, the operation of the NF membrane is governed in part by the osmotic pressure principle (see US Pat. No. 6,508,936). For these reasons, as shown in a later section, an NF membrane is more or less free of all divalent or monovalent ions to the same extent RO is a monovalent such as Na ⁺ , Cl ^−, etc. Rather than excluding ions, it differs in that it has a much greater exclusion with respect to divalent ions such as SO ₄ ⁼ , HCO ₃ ⁻ , Ca ⁺⁺ , and Mg ⁺⁺ scale-forming hard ions. NF has been used in Florida to process salty hard water to produce potable water. The NF method has also been used to remove colored turbids and dissolved organics from drinking water; Duran et al., Desalination, 102: 27-34 (1995) and Fu et al., Desalination. , 102: 24-56 (1995). NF has been used in other applications to treat salt solutions and landfill leachate; Linde et al., Desalination, 103: 223-232 (1995); injected into offshore oil wells Removal of sulfate from seawater; Ikeda et al., Desalination, 68: 109 (1988); Aksia Serch Baker, Filtration and Separation (June, 1997). As shown below, the NF seawater membrane pretreatment is performed at a much lower pressure, typically 10-25 bar, than the SWRO membrane operation (typically 55-82 bar, ie 800-1200 psi). .

In addition to the above use of the NF method, it has also been used in the treatment of various seawater and aqueous solutions. As mentioned above, the NF membrane of US Pat. No. 4,723,603 is used to remove sulfate from seawater, but it still has a high sodium chloride content and is Used to form a perforated slurry, this method prevents barium sulfate scale formation. US Pat. No. 5,458,781 discloses an aqueous solution containing bromide and one or more polyvalent anions in two streams, one bromide-rich stream and the second in a polyvalent anion. NF separation is described in a rich stream. Although further treatment with RO has been suggested to bring the bromide rich stream to bromide concentrations used in industrial applications, nothing has been done. EPO Notice No. 0914260 (03,06,97) passes seawater through three flat membrane cells of a polyvinyl alcohol polyamide nanofilter (NF membrane) to remove sulfate ions, and then passes the filtered water through an RO membrane. Thus, by removing SO ₄ ⁼ , a method has been proposed to solve the problem of improving the concentration rate while suppressing the deposition of scale (but no further details of the study are given).

  As shown in FIG. 6, the first person to apply NF pretreatment to SWRO and other seawater thermal (MSFD, MED, VCD) desalination methods, first in the pilot plant and demonstration desalination plant stages, In US Pat. No. 6,508,936, Hassan A. et al. M.M. Hassan et al., “Desalination and Water Reuse, Four Seasons”, published May-June (1998) Vol. 8/1, 54-59, and September-October (1998), Vol. 8/2, 35-45: Desalination, 118: 35-51 (1998); Desalination, 131: 157-171 (2000); Proceedings of the International Conference on Desalination and Water Reuse (San Diego) (1999) Best IDA thermal award for salt) and many other publications.

  This new NF-SWRO desalination process was first developed in a pilot plant and proved successful in solving the major problems previously mentioned for conventional seawater desalination processes by: (1) prevention of SWRO membrane contamination, (2) prevention of plant scale formation, and (3) not only significantly increasing plant productivity and improving SWRO product quality both in yield and recovery. Reduce both energy requirements and cost per unit water product. As shown in FIG. 6, a similar advantage was obtained by connecting the NF membrane unit and the thermal desalting MSFD unit as a double hybrid desalting unit. Similarly, as shown in the same drawing, the SWRO reject is used as a supplemental feed to the MSFD unit because the hard material has been removed from the reject in the SWRO unit to which the NF product is supplied. Has been successful. In both the double NF-MSF hybrid and the NF-SWRO (exclusion) -MSF triple hybrid, the MSF unit is operated for the first time even at a maximum brine temperature (TBT) of 120 ° C. and later with scale inhibitors. Without operating at higher TBT up to 130 ° C., but did not form scales in high yields up to 70% -80% (see previous paragraph literature).

  If the MSFD unit of FIG. 6 is replaced by either a MED, or VCD, or RH type thermal unit, the same argument applies, and in either case, the unit is a NF or Operating with replenishment of NF product or SWRO exclusion from the SWRO unit. In order to avoid the formation of scale on the surface of the evaporation tube through which steam passes, the operation of a single-operated MED, or VCD, or RH unit is limited to a TBT limit of the order of 70 ° C. or less. . NF products, or exclusions from SWRO units, or mixtures of NF products and SWRO exclusions from SWRO units that have been manipulated for that NF product, as shown in FIG. Either operation can operate with TBT much higher than their current TBT limit, and can obtain significant gains in both distillate yield and recovery. Under these replenishment conditions, for example, the MED unit operates safely at TBT> 70 ° C., eg, 80-120 ° C. or higher, without the risk of scale generation and without the addition of scale inhibitors. be able to.

This dual NF-SWRO desalination process, when the combined NF / SWRO units were each operated in a single stage, was further commissioned in 1986, a commercial scale plant, as shown in FIG. The existing Umm Lujj SWRO plant was applied to one SWRO train 100, capacity 2203 m ³ / d (582,085 gpd). The plant was converted from a single SWRO desalination process to a new dual NF-SWRO desalination process by introducing NF pretreatment and semi-desalination units in front of existing SWRO units (Fig. 7). A picture of the actual NF plant is shown in FIG. 8, where the front unit of the picture is an NF unit that is fully integrated with the SWRO unit at the back of the picture. The second line in the same plant, the train 200, is similar in design and manufacture to the train 100, but continued to operate in a single SWRO mode. Before establishing the operating parameters for a large NF-SWRO plant before changing the plant to the dual NF-SWRO method, the design and operation of the NF-SWRO plant using a demonstration unit similar to the new NF-SWRO plant. The method was tested. From the results of this experiment, the NF recovery rate in the train 100NF-SWRO was fixed to 65% (Fig. 9), and then successfully operated with the demonstration mobile pilot unit for 2 months with the NF product recovery rate of 70%. Hassan A. M.M. Others, Proceedings of IDA International Conference on Desalination (Bahrain) October 2001, Abstract, p. See 193-194.

The ion exclusion rate and the total hardness of scale-forming hard ions of SO ₄ ⁼ , Mg ⁺⁺ , Ca ⁺⁺ , HCO ₃ ⁻ of the NF unit of Train 100 are 99.9%, 98%, 92%, 56%, And 97% (FIG. 10). This very large hard ion rejection rate is compared to an exclusion rate of only 24% for monovalent Cl ⁻ ions and 38% rejection rate for TDS ions, and the TDS of about 45,460 seawater feed is , Reduced to 28,260 in the NF product (FIG. 10).

The results obtained from the operation of this commercial SWRO unit of a novel dual NF-SWRO desalting hybrid show a significantly improved product over that (SWRO unit) operation in the conventional commercial SWRO desalination process. The production rate and recovery rate are shown. The productivity of the train 100 operated in the NF-SWRO mode is 130 m ³ / hour from the supply of NF product, which is 234 m ³ / hour of seawater feed in one conventional SWRO operation. Compared to a production rate of 91.8 m ³ / hour when operated at 360 m ³ / hour, an increase in train production rate of 42%. Furthermore, the 56% recovery rate of a SWRO unit in a double NF-SWRO operation is twice that of 28% when it (SWRO unit) is operated in a single mode. The same trend is also observed when the permeate production and recovery of NF-SWRO train 100 are compared to the results obtained from SWRO train 200, with 1.5: 1.0 and 56 for SWRO units, respectively. %: The ratio is 23.5%, and the former is better than the latter train operation (FIG. 11). Also, compared to operation with the conventional SWRO method, the train 100 operation of the dual NF-SWRO hybrid significantly reduces energy consumption and cost per unit production (m ³ ) by 23% and 46 or more, respectively. Yes. Compared to the SWRO operation, the expected savings in both energy consumption / m ³ and cost per unit water produced by the NF-SWRO method are 39% and 68%, respectively. Furthermore, line conversion from SWRO to NF-SWRO operation can be done quickly and at a relatively low cost.

  US Pat. No. 6,190,556 B1 (February 20, 2001) describes a beverage from an aqueous supply such as seawater using a pressurized vessel designed for low pressure operation (250-350 psi). An apparatus and method for producing water is described, in which both NF and RO membranes are placed with an NF membrane member upstream of the RO membrane member. The seawater feed is first sent through the vessel and processed at this low pressure through NF to remove the hard material, but is only flushed unaffected through the RO membrane area. The NF product collected in a specially designed mechanism is later sent through the same vessel at the same pressure using the same pump, reducing its osmotic pressure and desalting through the RO membrane. Can do.

  Some other patents use an RO module prior to the SWRO module for SWRO desalination. U.S. Pat. No. 4,341,629 (July 1982) describes a method using cellulose acetate with 90% ion rejection first and then cellulose triacetate with 98% ion rejection. Is described. The invention of U.S. Pat. No. 4,156,645 (May 1979) has an ion rejection rate of 50-75% in two successive separate stages, each with its own high pressure pump. A fresh water recovery process is proposed that uses a SWRO hermetic membrane to treat the product from the loose RO membrane it has and operates at a low pressure of P = 300-400 psi. In EPO 6,120,810, a loose RO membrane unit is used before an airtight membrane unit, each unit being operated separately and having its own high pressure pump. U.S. Pat. No. 5,238,574 describes a method and apparatus for treating water with a plurality of RO membranes and then producing water and salts with an evaporation mechanism. U.S. Pat. No. 4,036,685 also produces high quality permeate removed from the first RO cartridge, while at the same time from the next two cartridges in series with the first RO cartridge. A method and apparatus for producing a low quality permeate by combining the products is described.

  From the discussions and results above, in addition to other pretreatments, very special functions, i.e. hard materials and shared ions, to a much greater extent than the rejection rate for monovalent ions (in Umm Lujj plant). (See Figure 10), stressing that NF is designed to perform the ability to eliminate at much lower pressures than those required by SWRO or RO methods as previously described. Can do. These facts characterize this extraordinary pretreatment and separate its function from the other previously shown water separation membrane methods, ie MF, UF and RO. Because of this property, the nanofiltration, loose reverse osmosis, and low pressure reverse osmosis used in the above-mentioned patents, ie, SWRO membranes that receive RO, loose RO, and LPRO pretreatment feeds, are considered the same in the art. It should be noted that not. In fact, the nanofiltration (NF) pretreatment of seawater feeds that allow those skilled in the art to remove hards and, as a result, produce drinking water from SWRO without forming scales with high recovery rates, We have and have recognized this fact that reverse osmosis (RO) or loose membrane reverse osmosis (LMRO) is not operationally or functionally equivalent. The references cited below highlight the differences:

1. Bequet et al., Desalination, 131; 299-305 (2000).
2. Bisconer, “Explore the Capabilities of Nano- and Ultrafiltration”, Water Technology, March 1998, (2 pages; page numbers not stated).
3. Kodak, “Nanofiltration for Professional Motion Imaging”, On-Line Technical Support paper, pp, 1-6 (1994-2000).
4). Linde et al., Desalination, 130; 223-232 (1995) (abstract only).
5. Nicolaisen, “Nanofiltration-Where does it Belong in the Larger Picture”, pages 1-7, “Desal-5” membrane product Product technical bulletin for "Desal-5" membrane products; Desalination Systems, Inc. (December 1994).
6). Scott Handbook of Industrial Membrane, 1995 (page 46).

  As Vis Corner admits, in this field, RO and NF can be considered “cousins” and the membranes used look the same, but in practice they are “clearly different” "I have a separate function." Among the important differences between NF and RO (BWRO, loose RO, and LPRO), NF gives a significantly larger rejection rate of hard ionic species at a much larger total product stream bundle than RO. It is clear from the above literature that this is actually observed in the Umm Lujj NF-SWRO experiment. This further provides a much greater feed quality improvement. See Hassan et al. And FIG. In particular, although Nicolaicen (1994) sometimes misrepresents various terms in the art, those skilled in the art will exclude di- and tri-anionic species at least particularly greater than the exclusion of NaCl. Not only does it point out that it recognizes the clear superiority of NF to RO in that it has a much larger (NF membrane) flux than the flux of RO membranes. I want. Furthermore, it has greater tolerance to turbid contamination than SWRO membranes. Others make the same point by recognizing that the RO flux is low compared to the NF flux and that a much greater pressure with a much larger membrane surface area is required in the RO than in the NF membrane. ing. These facts have been observed in the above commercial experiment of NF-SWRO operation in the Umm Lujj plant train 100, where each NF module consists of almost three SWRO modules (one module contains six membrane members). A single pressure vessel fitted with a feed. In order to have a real effect, the RO unit requires a finer feed pretreatment than the NF membrane process in the removal of solid particles.

SWRO membranes are the most airtight desalination membranes and are characterized by their large salt (all ions) rejection. SWRO membranes are operated at a high pressure, 55-82 bar depending on the membrane type, and their flow rates are low, so the SWRO method requires a large number of SWRO membranes to produce a large amount of water. Because of all these factors, the cost of water production by the SWRO method is considered the highest among all other membrane desalination methods. On the other hand, the NF membrane is operated at a much lower pressure and has a large flow rate. Most importantly, however, as noted above, they are characterized by great specificity for the elimination of scale-forming hard ions (SO ₄ ⁻ , Ca ⁺⁺ , Mg ⁺⁺ , HCO ₃ ⁻ ). See literature given earlier by Hassan et al.

Not only their main different properties, quality, and characteristics between SWRO and NF membranes, but also the ability to distinguish NF from other RO membranes, including the above-mentioned loose RO or low pressure RO membranes, one dual NF -Complete integration of NF and SWRO membrane, or NF and thermal method, as a SWRO operating method, or as a triple hybrid composed of NF-thermal method, or NF-SWRO (exclusion) -thermal method. The advantages are certainly obtained by Hassan A. M.M. U.S. Pat. No. 6,508,936, as successfully performed first on a pilot plant scale (see FIG. 6) and then on a commercial plant scale (see FIGS. 7 and 8). . However, this is done by using not only each of the NF and SWRO units, but also a thermal unit in one step. As shown below, each of the NF and SWRO units is operated in a dual NF ₂ -SWRO ₂ set in two stages with a turbocharger placed between the two stages to recover energy from the brine By doing so, a greater advantage is seen. This highly optimized and well-designed dual NF (two stage) -SWRO (two stage) configuration shown in FIG. 12 for the proposed Red Sea SWRO plant has a feed rate of about 316 m ³ / hour and about A yield of 170.0 m ³ / hr (1.08 mgd), an optimal seawater desalination method, increasing both plant production rate and yield and water recovery rate, producing freshwater units from the sea Not only does it provide an economically efficient SWRO desalination operation by lowering the energy requirements and costs of it, but it effectively outperforms what can be predicted by conventional, conventional seawater desalination methods. . The method further of the present invention NF ₂ - thermal and _NF 2 -SWRO ₂ (elimination thereof) - also be further applied to a thermal operation (Fig. 4 and 5), in this case, the thermal unit MSFD, or It may be MED, VCD, or RH, SWRO ₁ is composed of one SWRO unit operated at P≈75 ± 10 bar using a high pressure tolerant SWRO membrane (P≈84 bar).

The above optimum NF (2 stages) -SWRO (2 stages) and double and triple NF ₂ - thermal seawater desalination system, conventionally, including methods described in U.S. Pat. No. 6,190,556B1 Not only are they completely different from the law, they are far superior to them in terms of process efficiency and economy. For example, the NF-SWRO system described in US Pat. No. 6,190,556 B1 (February 20, 2001) has both NF and SWRO members placed in the same pressurized container. However, it is operated at the same but lower pressure of 17-25 bar (250-350 psi) using a single pressure pump. In this system, the operation is first started by collecting sufficient NF product, after which the collected NF product is placed in a specially designed and controlled holding tank and under pressure (250-350 psi). Low pressure) through the SWRO membrane, producing a product of questionable quality mainly due to the SWRO low pressure. More importantly, if the NF membrane is operated for some time, it can be left idle during the next SWRO operation, or vice versa, to partially utilize the NF or SWRO membrane. It is that. In contrast, in all components and units according to the present application, FN ₂ -thermal, with or without SWRO combination, or NF (two-stage) -SWRO (two-stage) double and triple hybrids are completely This fact has resulted in a higher plant production rate. In addition, the two-stage configuration provides sufficient high pressure for the second stage feed, particularly for the first and second stage SWRO units of the hybrid, again in this US Pat. No. 6,190,556 B1. Giving a higher plant production rate with a much higher product quality than that obtained from the use of the specification. To produce the same amount of water on a commercial scale by the two methods, the latter method requires more capital investment and more equipment than the method given here (optimal method). And

  Therefore, it produces economically fresh water from salt water, especially sea water, in a good yield, effectively and efficiently addresses the problems mentioned above, ie removes hard substances and turbidity from such salt water, The ability to obtain an optimal thermal seawater desalination process that reduces total dissolved solids with increased plant production rates and economic efficiency, including low energy consumption per unit water product and low water costs, is virtually worldwide. It will be of interest to people inside, especially those who need fresh water from the sea, but can't. Use of thermal MSFD, or MED, or RH, or rejects from SWRO units fed with NF product, or replenishment to VCD plants, or the use of NF (two-stage) pretreatment methods can also be used. A salt unit will give a similar gain, resulting in a huge improvement in the efficiency of all these seawater thermal desalination plants.

SUMMARY OF THE INVENTION By combining two substantially different water film and thermal methods represented by the configurations given in FIGS. 4 and 5 in a manner not previously performed, special emphasis is placed on seawater. Demineralize salt water to produce high quality fresh water, including drinking water, in very high yields per unit product equal to or better than the conventional thermal desalination process with much lower efficiency We have invented an optimal thermal seawater desalination method that generates energy consumption. To achieve this objective, as part of the triple hybrid process, each of the NF and SWRO units of FIG. 5 is arranged in two stages, with an energy recovery turbocharger between them, or high pressure tolerance up to 90 bar. A single stage SWRO with a membrane operated energy recovery TC or PX system is used to operate with NF and SWRO membrane selectivity for the methods described below and in the previous section. This approach not only improves product quality and increases product yield and production rate from each stage, but also the optimal NF ₂ -SWRO ₂ or NF ₂ -SWRO ₁ portion of the process: The ratio of the conventional single SWRO process has the net effect of reducing energy consumption per unit water product at a ratio of about 0.445: 1 and reducing cost per unit water product. In this method, two-step nanofiltration as a first desalting step is synergistically combined with (1) a thermal desalination unit of MSFD, MED, VCD, or RH to produce an NF ₂ -thermal hybrid (Figure 4) or (2) synergistically combined with a two-stage SWRO ₂ unit or a one-stage SWRO ₁ unit to form a beverage product and an exclusion, the latter being NF-SWRO (exclusion)- A thermal triple hybrid (see Figure 5) combined with it constitutes a supplement to the thermal unit (MSFD, or MED, or VCD, or RH), giving a fully integrated desalination system, Allows salt water (especially seawater) to be efficiently and economically high quality freshwater, significantly more than the yields obtained with conventional thermal seawater desalination methods alone or in combination so far known or described Big good Converted in good yield. Thus, individual processes are known separately and such processes have been described individually in combination with other methods for different purposes, but are due to different stages and configurations, As discussed above, the method of the present invention has not previously been known or conceived by those skilled in the art, and compared with the conventional method and apparatus, the salt water desalination obtained by this method. There is nothing in the prior art that suggests that all the forms (membrane type or thermal type) of this type provide surprising and unique great improvements and great system efficiency.

  Thus, in a broad aspect, the present invention provides for the recovery of energy between hard scale-forming ionic species, microorganisms, particulate matter, and large amounts of total dissolved solids to two-stage nanofiltration, during those stages. Place turbocharger and refill with pressure increasing pump as needed, not only the content of the hard ionic species is dramatically reduced, but also has a TDS content significantly lower than seawater Forming a first high recovery, low energy consuming NF water product from which microorganisms or particulate matter have been completely removed, after which the first water combined with the NF products from the two NF stages The product is passed through the next MSFD, or MED, or VCD, or RH seawater desalination unit, which is much lower than the salinity of the rejected product (blowdown) (Figure 4) and has a drinking water quality salt Salt equal to degrees In desalination processes comprises generating a second water product (distillate) having.

Even in the case of the second broad aspect, the present invention provides a two-stage NF (NF ₂ ) membrane containing saline containing hard scale-forming ionic species, microorganisms, and particulate matter as claimed in claim 1. A first water product with a reduced content of ionic species, microorganisms or particulate matter is formed from the combined product of the two NF stages through the treatment unit, after which The first water product is passed in the next two stages SWRO (SWRO ₂ ) through those stages with energy recovery TC between those stages, optionally supplemented with a pressure increase pump, from the two SWRO stages. From the combined products, the third water product, which is a beverage quality low energy consuming SWRO water product with reduced salinity, and increased salinity but very hard scale forming ions Lower fourth excretion Forming a scavenging product, after which the SWRO exclusion product is passed through an MSFD, or MED, or VCD, or RH seawater distillation unit, with a salinity equal to the salinity of the drinking water, A desalination process comprising forming a second water product (distillate) having a salinity much lower than that.

Both the first and second aspects constitute the basis for an optimal thermal seawater desalination process, which is the subject of this patent application including the following seawater thermal desalination hybrid:
1. NF (two-stage) -MSFD, or NF (two-stage) -MED, or NF (two-stage) -VCD, or NF (two-stage) -RH,
1. Double NF-thermal, or NF (two-stage) -SWRO ₂ (exclusion) -MSFD, or NF (two-stage) -SWRO ₂ (exclusion) -MED, or NF (two-stage) -SWRO ₂ (exclusion) -VCD, or NF ( two steps) -SWRO ₂ (elimination thereof)-RH,
Thermal - triplet _NF 2 -SWRO ₂ of.

  Here, in the double hybrid, the NF product constitutes the thermal unit supplement, whereas in the triple hybrid system, the reject from the one or two stage SWRO constitutes the supplement to the thermal unit. .

Further, the NF unit configured as shown in FIGS. 4 and 5 is composed of two NF units (NF ₂ ) in which an energy recovery TC is arranged between the stages. A salinity recovery PX with a two-stage NF unit with a pump can likewise be replaced. In the same way, a two-stage SWRO (SWRO ₂ ) with energy recovery TC between the stages is achieved by a one-stage SWRO ₁ with an energy recovery PX unit operated with a high pressure (P≈84 bar) tolerant SWRO membrane. Can be replaced.

  The method easily and economically produces a significant reduction in the properties of salt water (especially sea water) and produces good fresh water, including drinking water. Typically, the treatment of this two-stage NF product according to the present invention, with respect to the properties of the seawater feed, reduces the calcium and magnesium cation content on the order of 75% to over 95%, 90-99.9%. This order of sulfate reduction, pH reduction of about 0.4-0.5, and total dissolved solids content (TDS) reduction of about 30-50%. On the other hand, the product from the SWRO unit has drinking water quality, but the drinking water product from the MSFD, MED, or VCD, or RH unit is supplied with NF product or NF product. Distillate when operated by a supplement consisting of SWRO exclusion from the SWRO unit.

  Drawings are graphs or process diagrams relating to data given in the text. A more detailed description of the drawings will be found in the discussion of data.

Detailed Description and Preferred Embodiments Optimal seawater desalination of the present invention will be best understood by first considering the various components and properties of salt water, particularly sea water. As mentioned earlier, seawater has a high hard substance concentration due to the presence of high TDS, scale-forming hard ions Ca ⁺⁺ , Mg ⁺⁺ , SO ₄ ⁼ , and HCO ₃ ⁻ at relatively high concentrations. And having varying degrees of turbidity due to the presence of particulate matter, macro and micro organisms, and a pH of about 8.2. Many of the problems with seawater desalination limitations and their effects are related to the quality of these seawaters and the fact that they contain foreign material. Seawater typically has a cation content on the order of 1.2% to 1.7%, of which about 900-2100 ppm are “hard” cations, ie calcium and magnesium cations. The anion content of scale-forming hard ions, ie, sulfates and bicarbonates, is about 1.2% to 2.8%, and the pH is about 7.9 to 8.2. Typically, there may be a wider range for one or more of these properties, with total dissolved solids on the order of 1.0% to 5.0%, generally 3.0% to 5.0%. May constitute the content. However, it will be appreciated that these components and properties vary throughout the world's oceans and oceans. For example, a small closed sea with a hot climate usually has a higher salinity (ion content) than the high seas region, for example, a bay-to-ocean seawater composition as shown in Table 1.

One major problem of seawater desalination is the high TDS of the seawater feed, especially in the case of the SWRO process. The osmotic pressure of the feed increases as the TDS of the feed increases. Given a given applied pressure P _appl , this increase in osmotic pressure (Pπ) of about 0.7 bar per 1000 ppm TDS increase reduces the resulting pressure P _net :
P _net = P _appl −Pπ (1)
_Where P _net is the pressure that pushes water through the RO membrane to produce a permeate stream. In order to increase P _net and thus increase the permeate stream, a high applied pressure is required as long as the membrane strength can be tolerated. The effect of feed TDS variation on osmotic pressure and P _net pressure with the SWRO method at a temperature of 25 ° C. and an applied pressure of 60 bar and a final brine TDS of 66,615 ppm has been shown previously in FIG. Effective applied pressure to extrude the water through the membrane is represented by the area shaded in P _{net Non,} it decreases as the feed TDS increases. Since the permeate stream through the membrane is directly proportional to the water driving pressure P _net , the reduction of the seawater feed TDS by the method of the present invention not only reduces energy waste but also increases the fresh water permeate through the membrane. . As illustrated below, the reduction in energy requirements per unit water product due to the reduction in feed TDS in this case, which would increase the P _net and SWRO unit osmotic flow, is the main gain obtained by the method of the present invention. This is an advantageous effect.

  Similarly, the turbidity (reflecting total suspended solids and microorganisms) of small areas such as the ocean or ocean, where the desalination plant draws its seawater feed, reflects the organism and particulate matter. Depending on local concentrations, such concentrations within the same sea can often change with weather, climate and / or topographical changes. Typical values are shown in Table 1 for typical high sea water, Mediterranean, and closed “bay sea” (sometimes referred to as “ocean water” and “gulf water”, respectively) in the future. The seawater fluctuation between water is illustrated. “Ocean water” is often taken as the basis for standard (usual) seawater properties, but for the purposes of the discussion here, the components and properties of oceans and seas around the world are substantially It will be appreciated that these local variations, which are similar everywhere and can occur, are well understood and understood by those skilled in the art. Thus, the present invention described herein is useful in virtually any map location, and the following description of operations relating to gulf water or ocean water is not intended to be limiting, but merely considered as examples. It should be.

  The presence of particulate matter (macroparticles), microorganisms (eg, bacteria), and macro-organisms (purple oysters, barnacles, seaweeds) will remove them from the feed to both SWRO and thermal desalination plants. I need. The removal of turbidity and fine particles, usually defined as total suspended solids, from the feed intended for the SWRO plant was essential, but was not always required in the thermal process. It has become most necessary to remove chlorine from the feed to chlorine sensitive NF and SWRO membranes.

As already shown repeatedly, the third major problem inherent in all conventional desalination methods is the high content of hard ions in seawater, which is more thermal than the membrane method. Has a major negative effect. Since all desalting processes are operated to extract fresh water from salt water, salt and hard ions are left in the brine, giving the effect of increasing both the brine TDS and hard matter concentration. This is illustrated in FIG. Since hard ions are only slightly soluble in seawater, they usually deposit in the form of scales in desalination equipment, such as pipes, membranes, etc. For example, the water recovery rate is limited to a low value of 25 to 35% or less, and 30 to 40% in ocean seawater. Depending on the conditions in which the desalting process is operated, two types of scale forms occur: an alkaline soft scale mainly composed of CaCO ₃ and Mg (OH) ₂ and mainly CaSO ₄ , CaSO ₄ .H ₂ O, and CaSO _4. It is a non-alkaline hard scale composed of 2H ₂ O. The latter form becomes worse as the temperature increases. This is because the solubility of CaSO ₄ decreases as the solution temperature increases. Traditionally, in thermal desalination plants such as MSFD or other MED plants, acids and other anti-scale additives are generally added to the feed water, and in the case of MSFD, at a brine temperature of 90-120 ° C, the MED In the case of a plant, the process operation is limited so as not to cause scale formation at a brine temperature of 65 ° C. However, nevertheless, freshwater product recovery was as low as 25% to 35% as a fraction of product to replenish the feed from Gulf seawater. At higher operating temperatures, ion exchange was required to remove SO ₄ ⁼ or Ca ⁺⁺ and obtain higher water recovery. Similarly, in SWRO operations, scale inhibitors have also been commonly added to prevent membrane or plant scale formation, but again, for example, in the case of Gulf seawater, the water recovery rate by conventional methods is still about It was limited to 25 to 35% or less. In addition, the scale inhibitor is usually returned to the marine environment, as part of a brine discard, or during a descaling operation. Such materials are usually pollutants in the marine environment and should be avoided as such.

  These problems during seawater desalination and the measures used to mitigate them, along with the quality requirements for the feed to the SWRO plant when taking the feed from the high seas (surface) intake, Table 2 has already been summarized and given. The two-stage NF feed pretreatment method used with or without a suitable scale inhibitor in the present invention can efficiently and economically remove turbids, hard ions and reduce TDS. The process of the present invention can be carried out with higher NF product recovery than would be expected with the conventional process, and therefore the process of the present invention is conventional and other conventional seawater desalination processes. It will be understood that this provides a significant improvement. In addition, the removal of hard ions helps to increase recovery in all types of seawater desalination methods (membrane or thermal).

Briefly, the optimal seawater thermal desalination process of the present invention significantly reduces hards, lowers TDS and removes turbidity from the feed in the membrane process step, thereby eliminating energy and chemical consumption. Reduce the volume, increase the water recovery rate, and reduce the production cost of fresh water from seawater. This is achieved by a unique combination of NF and SWRO or thermal desalination unit as a dual or triple hybrid system, as already explained in the previous section, as shown by way of example in FIG. Each of the two-stage NF and SWRO units with an energy recovery turbocharger between stages, or a combination of two-stage NF and MSFD, MED, or VCD, or RH (FIG. 4), or alternatively, FIG. As shown in Figure ₃ , triple NF (two-stage)-SWRO2 (exclusion)-achieved by the combination of NF, SWRO and thermal as a thermal formula, which is further improved by additional combinations with media filtration Depending on the quality of the feed, with or without agglomeration, or by using an underground water intake such as a coastal well to collect seawater, or The use of pre-treatment with F or UF membrane can be improved.

  Nanofiltration, SWRO, and various thermal seawater desalination are all widely described in the literature and have become the commercial facility for each source. Thus, a detailed description of each stage, equipment and materials used herein, and various operating parameters need not be given in detail here. As a typical example of a comprehensive description of the literature, ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY for nanofiltration by Kirk-Othmer, 21: 327-328 (No. 4th edition: 1991); 303-327; and RO for McKetta et al., ENCYCLOPEDIA OF CHEMICAL PROCESSING AND DESIGN, 16: 198-224 (1982), and Corbitt. ), STANDARD HANDBOOK OF ENVIRNMENTAL ENGINEERING, 5-146 to 5-151.

  By describing and understanding the basic concepts of NF, SWRO, and thermal units, NF can be coupled to SWRO and fully integrated in two stages for each of NF and SWRO, or for example MSFD The details of the progress of the research conducted in the combined and fully integrated NF two-stage can best be understood by referring to experimental studies conducted on a pilot plant scale. A schematic process diagram formed as an NF-SWRO method by one single stage NF combined in one single stage SWRO is given in FIG. The method consists of a pre-treatment seawater supply system usually consisting of a dual media filter and subsequent fine sand filter, 5μ cartridge filter, feed tank, two-stage NF unit, and two-stage SWRO unit. The particle size of the sand in the sand filter can be varied and is usually on the order of 0.3 to 1.0 mm. The pre-treatment part of this system is incorporated into this new invention, but is double NF (two stage) -thermal or NF (two stage) -SWRO (two stage) thermal (FIGS. 4 and 5). Is not shown. This filtration step is excluded from the method when the seawater feed is taken from an efficiently made coastal well or from microfiltration (MF) or ultrafiltration (UF) membrane pretreatment. The

  In commercial SWRO or NF plants, membrane members are usually arranged in series as six members per pressurized vessel. This type of membrane configuration has become a preferred configuration in many commercial NF and SWRO plants worldwide. This is also the array of NF and SWRO members used in the dual NF-SWRO operation in the commercial Umm Lujj SWRO plant shown in FIGS. In order to establish the performance of six members within one pressurized vessel, the demonstration unit can replace two members instead of six members (8 ″ × 40 ″) per pressurized vessel, as shown in FIG. It was constructed using three pressurized vessels each fitted with an NF member (8 ″ × 40 ″). The performance of each of the two members in the first: second: third pressurization vessel was as shown in the same figure and had the following ratio.

From a feed of 11.95 m ³ / h with an applied pressure of 25 bar and T = 30 ° C. and a TDS of 45,000 ppm:
Product logistics 4.61: 3.3: 1.32 Total: 9.28m ³ / hr Product recovery rate 38%: 28%: 11% Total recovery rate: 78%
Product TDS 28,000: 35,000: 40,000 Combined product: 32,270 ppm
For each vessel, product recovery was calculated as the ratio of NF product to total feed 11.95 m ³ / hour. As shown in the same figure, the two elements in the third container are highly stressed; they have a feed of only 3.99 m ³ / hour with TDS = 69,100 ppm, ie For the first two parts, for example, 1/3 of the feed at 11.95 m ³ / hour is received at P = 24 bar, which is higher to overcome the increase in the third container part feed osmotic pressure. When pressure was required for their operation, TDS = 45,000 ppm seawater was supplied at P = 25 bar.

In order to remove this large stress on the last two members in the third container, or a part thereof, and increase the efficiency of the NF process, the present invention uses the configuration shown in FIG. 4 for the NF unit. In this configuration, the NF process was performed in two stages with an energy recovery turbocharger placed between them. This configuration has two functions: it increases the product stream and water recovery and reduces the energy consumption per unit water product, as will be shown later. The ratio of the number of members in the first: second NF stage was set to a ratio of about 2: 1. In addition, with this configuration, at a first stage NF recovery of about 50%, each member in the first and second NF stages receives approximately the same amount of feed, and the second stage member is the first stage NF. Received almost the same amount of feed as was sent to the part, but received a higher amount of feed when the SWRO recovery for the first stage was lower than 50%. The first stage in which seawater was supplied at P = 25 ± 10 bar consists of two parallel NF blocks by way of example, where one block is a number arranged in parallel according to seawater feed quality (TDS). Each of the pressurized containers was provided with four NF elements. If the feed TDS was of ocean quality or less, a total of 5-6 members could be used in one pressurized vessel. On the other hand, the second stage has one NF block with about half the number of modules in the first stage block. All modules are arranged in parallel, each consisting of one pressurized vessel fitted with a 4NF member. The first and second stage NF members may be of the same type as long as they can withstand high pressures up to 35 ± 10 bar, or the second stage NF member may be replaced by the first stage NF member. Choose to have a higher pressure tolerance up to 45 bar, higher than the allowable pressure. The second stage NF unit is fed with the combined reject from the first stage module after increasing its pressure from 25 ± 10 bar to 35 ± 10 bar by a turbocharger. If necessary, the second stage pressure can be further increased (added) by using a pressurized pump that can receive the first stage rejection after being increased by the turbocharger, as shown in FIGS. Pressure) and raise it further to the desired pressure value. The turbocharger pressure increase (ΔP) is equal to the following (Pump Enguneering, Inc. Manual # 299910):
ΔP _tc = (nte) (R _r ) (P _r −P _c ) (2)
nte = hydraulic energy transfer efficiency R _r = ratio of brine flow to supply to turbocharger vs. feed stream P _r = brine pressure to turbocharger C _c = brine pressure exiting turbocharger

  For example, in the case shown in FIG. 12, ΔP calculated for the SWRO unit is equal to 37.5 bar (0.65 × 0.65 × 83 = 37.5 bar).

  The configuration of NF (two stages) -SWRO (two stages) is illustrated in FIG. The NF unit consists of a high-pressure pump so as to apply a pressure of up to 25 ± 10 bar to the first stage NF unit, which unit consists of two modules arranged in parallel. As previously mentioned, one module consists of one pressurized vessel containing four NFs of 8 ″ × 40 ″ membrane members or other sized membrane members. While NF membranes may be in the form of spirals, hollow microfibers, tubes, or plates, almost all commercial NF membranes are thin film composites that are spirally shaped. Made from a nanocellulose polymer having a rolled form. The polymer is of the usually hydrophobic type with negatively charged groups, as described, for example, by Raman et al., Chem. Eng. Progress. 7 (1): 58 (1988). . The seawater feed is fed to the first stage module at ambient seawater temperature and their combined pressure exclusion is illustrated in FIG. 10 to the next second stage module with four NF members per module. As shown, it is supplied after increasing its pressure to 35 ± 5 bar by a turbocharger fixed between the two stages. If necessary, a pressure pump can raise the pressure above 40 bar. The number of modules in the second NF stage is about 1/2 or approximately equal to their number in the first NF stage. The seawater feed pretreatment unit has the same parts and configuration as the feed pretreatment shown in FIG. Alternatively, direct feed from coastal wells can be used without the need for a pretreatment unit or from MF or UF membrane pretreatment.

  Combined NF products from the first and second NF stages are (1) sent to a SWRO unit with one high pressure pump giving a pressure of 50 ± 10 bar, and (2) arranged in parallel, conventional SWRO The type of membrane used in the plant, e.g. Toyobo or Toray or Hydranautics, or Filmmec, or sent to the first stage SWRO consisting of a block of modules consisting of DuPont membranes, (3) Pass the pressure exclusion collected from the first stage SWRO module through a turbocharger and increase its pressure to about 85 ± 5 bar, then the pressure exclusion (4) the second stage SWRO unit Each module is fitted with one to four SWRO members of high pressure acceptable brine conversion, eg Toray 820BMC or equivalent SWRO membrane. SWRO supplied to one unit made up of a block of modules consisting of vessels. By using a turbocharger, if necessary, the pressure can be increased to 90 bar by using a pressure pump. SWRO exclusions that collect the combined products from the two SWRO stages and consist of a final product with drinking water quality, but with dramatically reduced hard matter, as illustrated in FIG. Used as a supplement to the thermal unit.

  The configuration of the MSFD unit can be exemplified as an example of the configuration of another thermal desalination unit in double and triple hybrids. The MSFD unit consists of three regions: (1) heating region, (2) flash and heat recovery (HRC) region, and (3) heat rejection (HRJ) region + other ancillary members: deaerator, brine circulation (BR ) Pump or the like (see the configuration of the MSF pilot plant shown in FIG. 6 as an example). Commercial MSF plants have the same layout but a much larger number of stages for flash and heat recovery areas of 10-20 or more stages. In the heating zone, steam from the boiler or low-pressure steam from the generator heats the seawater that has passed through the salt water heating vessel in a group of tubes and returns the aggregates of that flow to the boiler. The heated seawater flows into the first stage vessel in the flash heat recovery area, where ambient pressure is controlled to flash the heated seawater (boiling vigorously at the explosion rate). Only a small percentage of the heated water is converted to water vapor, which releases latent heat and condenses on the tubes, heating the water in the heat exchanger tubes through that stage. The agglomerated vapor is collected as a distillate fresh water vapor product, while brine (seawater with a high salt concentration) flows to a second stage that operates under a lower ambient pressure than the first stage. The process of flushing, steam agglomeration, and the flow of brine to the next stage is repeated through the various heat recovery stages, after which the brine from the final stage is passed to the heat rejection stage where it is cooled, and so on. Later, a portion is discharged as a concentrated brine blowdown (BB) and the remaining portion is recycled back to the evaporation process through the flash and heat recovery zones.

As illustrated in FIG. 4 (NF ₂ -thermal case) and FIG. 5 (NF ₂ -SWRO ₂ (exclusion) -thermal case), in this case, for example, the thermal unit is MSFD or MED, Or a VCD, or RH unit, which receives the NF product or SWRO reject, or a combination thereof as a supplement, which is separated into product (distillate) and brine blowdown. Similarly, the same discussion applies to any of the thermal desalination units in FIG. 5 where the thermal unit is either MSFD, MED, or VCD, or any other seawater thermal desalination unit of RH. Can be extended. The performance of the thermal unit depends on the operating conditions without adding a TBT limit to it with conventional thermal methods. MSF units are currently free of scale-forming hard ions (especially sulfate and bicarbonate ions that can be completely eliminated by NF pretreatment or reduced to very low concentration levels). In the case of MSFD, it is possible to operate at a TBT far above their limit of 120 ° C., and in the case of MED, or VCD, or RH units, a TBT far above the limit of about 70 ° C. .

Field work on commercially available NF membranes conducted at our R & D illustrates that they differ significantly in performance and can be classified into more or less three groups: The “A” group is an NF membrane with an airtight structure characterized by having a high rejection rate but a low permeate flow (flux), whereas the “C” group is a large flow and mild The “B” group has good balanced performance in terms of permeate flow and ion exclusion (Hussan et al., Proceedings of IDA International Conference on Desalination, 1999 10). Moon). Almost all NF membranes have an excellent sulfate rejection rate of over 90% and a good bicarbonate rejection rate, which can be combined with the acid-pretreatment of the feed to the NF ₂ unit, or the NF product. It can be further reduced to an acceptable level by post-processing. However, ^{they, Ca ++, Mg ++, Cl} -, and are different in exclusion of TDS (Figure 14). As a result of this study, the “B” group of membranes has been successfully used in the dual NF-SWRO operation of the Umm Lujj SWRO plant (Hussan et al. Moon). The same type of NF “B” group and / or selected NF membranes of “C” group, in the present invention, in the first stage of the plant of the present invention in the configuration of NF and SWRO as shown in FIGS. Used in NF containers. “B” group type membranes with membranes with higher pressure tolerance are used in the second stage NF unit.

As illustrated previously, by using a demonstration plant consisting of three pressurized vessels, each containing two NF8 ″ × 40 ″ membrane members of the “B” group of NF membranes, P = 25 bar, about 12 m ^3. A product recovery rate of 66% from the first and second module members was achieved at a feed rate of / hour and T = 30 ° C. (FIG. 13). In replicates, only about 62% recovery was achieved when operating the same four members with the same NF membrane at a feed rate of 8 m ³ / hour, P = 24 bar, and T = 28 ° C. (FIG. 15). About 5.1~5.2m ³ / NF product stream time is obtained from feed 8m ³ / time, NF supply amount, as long as the temperature and that the pressure is kept constant, the first stage NF unit A product recovery of about 62% was maintained, giving them consistency in product conductivity (FIG. 15). Control of the feed temperature up to about 35 ° C can be achieved by replacing some warm seawater (43 ° C) used to cool the MSF distillate in the heat rejection zone of the MSF unit with the appropriate seawater portion (18-25 ° C). ) And mixing (see FIG. 6). The NF unit performance variation along with the feed temperature variation is clearly illustrated in FIG. 15 for the case where the NF unit is operated with only the seawater feed (18-25 ° C.) without this mixing step.

As shown in FIG. 3, the removal rates of the scale-forming hard ions of SO ₄ ⁼ , Mg ⁺⁺ , Ca ⁺⁺ , and CHO ₃ ⁻ by the NF member of the first container are 99.9, 98.3, and 96, respectively. The hard ion rejection by the same type of NF membrane member in the second container was 99.9, 98.3, 96, and 78%, while .8 and 84.4%. In some experiments, no SO ₄ ⁼ ions were detected in the product of the NF member in the first and second vessels. The scale forming hard ion rejection of SO ₄ ⁼ , Mg ⁺⁺ , and total hard ions (for Ca ⁺⁺ and Mg ⁺⁺ ) greater than 98% is almost the same as that of the NF member product in the first and second containers. It is recognized that the same is true for the Ca ⁺⁺ ion rejection rate. However, there is a difference in the rejection rate of HCO ₃ ⁻ between the NF members of containers 1 and 2 (Table 3), which is due to the acid / post-treatment of the NF product or to the pre-treatment region of FIG. It is possible to reduce the level to a desired level by controlling. The NF hard ion exclusion rate established in this experiment is similar to that previously achieved in the Umm Lujj plant where six NF members of the same type are placed in one pressurized vessel (FIG. 10). The product water recovery compared to the feed at about 8 m ³ / hour is 36.3% and 25.6% for the front part of the first and second pressure vessels, and from the four parts The total was about 62%.

Compared to the excellent rejection of the NF membrane for hard ions, the rejection of monovalent Cl ^- ions is only 35.6 and 23.8% for the NF members of containers 1 and 2, respectively. The TDS ion rejection rates are 42.7 and 31.4%, respectively, and the exclusion by NF is much greater for covalent hard ions than for monovalent ions, but RO (BWRO, SWRO, LPRO, and Loose RO) supports the previous argument that more or less monovalent and covalent ions have the same exclusion rate.

From the above results, as shown in FIG. 16, the performance of NF depends on the operating conditions of applied pressure, operating temperature, supply flow (quantity) and quality (TDS). By controlling these operating conditions, a recovery rate of about 62% or more can be obtained from the first NF stage in the NF pretreatment unit having the configuration shown in FIGS. 4 and 5 as already established. You can conclude that Furthermore, if it is supplied from the NF first stage reject to the second stage in the same figure, a recovery rate of about 35% can be easily obtained, and the total recovery rate from the two stages should be 75%. I was able to. When the first stage was operated at 25 bar and a recovery rate of 62% and the second stage was operated at a recovery rate of 40%, a total recovery of 77% was achieved from the two-stage NF unit in the pilot plant. The feed consisted of Gulf seawater, TDS≈45,000 ppm. As was done with the 77% recovery above, increasing the pilot plant feed from 8 m ³ / hr to 9 m ³ / hr and maintaining the same pressure of 25 bar, the NF product recovery is 80% Rose. This recovery can be achieved by adding an appropriate scale inhibitor to the feed from an NF (two-stage) unit operated with Gulf Seawater (TDS 45,000 ppm), even at slightly higher recovery values. Obtainable. As stated previously, this is compared to the 70% NF product recovery obtained from six components placed in series in the same pressurized vessel at the Umm Lujj plant (Hussan A. et al. M. Others, Proceedings of IDA International Conference on Desalination, Bahrain, March 2002).

The complete integration of the NF ₂ stage and the thermal unit can be illustrated by sending all of the NF ₂ product of FIG. 4 to the thermal unit, previously operating on the NF product at 120 ° C. TBT. A distilled water recovery rate of 65-75% was obtained from the MSF pilot plant unit (Hassan et al., Desalination, 118 (1998) p. 35-51). Later, recovery rates higher than 70% were obtained in the same pilot plant. The same distillate recovery ratio of about 71% was obtained when the thermal unit (MSFD) of FIG. 4 was operated with a TBT of about 125 ° C. for a replenishment consisting of NF product. The total expected distillation product obtained with an initial seawater feed rate of 316 m ³ / h into the dual NF-thermal system is 170 m ³ / h with a total recovery of 54% (FIG. 4).

As illustrated in the configuration shown in FIG. 5, triple recovery NF ₂ -SWRO ₂ (exclusion) -thermal operation achieves a better recovery rate, in which case a total recovery rate of about 60% or more is achieved. Can be achieved. As shown in the same figure, the SWRO unit is also operated in two stages with a turbocharger placed between the dual NF-SWRO desalination systems. This is extremely feasible and applicable when considering the use of a SWRO high-pressure membrane developed later. At the SWRO pilot plant level, if the plant is operated on an NF product at an applied pressure of 50 bar, a water recovery rate of 60% is achieved, and at an applied pressure of 70 bar, it rises to 80% recovery rate (Figure 17). Similarly, a water recovery of 56-58% was achieved with the Umm Lujj SWRO train 100 operated on the NF product in only one step (see previous literature by Hassan et al.).

As shown in FIG. 5, assuming the first stage SWRO water recovery ratio of 52%, a total 19,500m ³ / day can be achieved by the first stage NF product feed rate of 37,500m ³ / day In contrast, only 6480 m ³ / day is obtained by the second stage SWRO at a water recovery of 36% and a pressure of about 92 bar, with a feed of NF product from 37,500 m ³ / day to 25,980 m ³ Total SWRO product water / day, or total SWRO recovery for those stages is 69% or more. Because of the very low hard ion content and the high pressure applied to the second SWRO stage, a recovery rate higher than 71% is expected from the two-stage SWRO unit. This brings the total end product recovery of the total NF (two stage) -SWRO (two stage) desalted hybrid to about 52% (0.75 × 0.69).

Furthermore, by using the SWRO reject in the above case as a supplement to the thermal unit (see FIG. 5), water recovery in the form of a distillate can be achieved up to 70% of the SWRO reject. However, the SWRO exclusion from the second stage is about 91,900 ppm, making it difficult to achieve 70% recovery from the thermal unit. To solve this problem and to limit the thermal unit blowdown to an acceptable TDS level of 140,000 ppm which has been proven in pilot plants without experimental scale formation, the SWRO unit from this case Exclusion 11,625 m ³ / day is mixed with 37,500 m ³ / day NF product as shown in FIG. 5, and the combined mixture of 49,125 m ³ / day is used as a supplement to the thermal unit. To do. Again, the total distillate is 33,895 m ³ / day with 69% recovery as thermal unit recovery from this SWRO reject + NF product mixture, SWRO permeate + thermal unit distillate. The total output of the triple hybrid unit composed of 59,775 m ³ / day with a total plant water recovery of about 60%. Thus, operating a desalination plant in a triple hybrid configuration increases plant drinking water recovery to about 60%, compared to only 52% by using two NF thermal configurations. The operation of increasing the thermal unit maximum brine temperature increases both the output specific gain (GOR) and the performance ratio (PR), which reduces the energy consumption and lowers the water production costs, as shown in FIG. Results.

In addition to the benefits of lowering energy requirements per unit water product and water costs and increasing plant production rates, both water flow rate and product recovery, this optimal dual NF ₂ − Thermal and NF ₂ -SWRO ₂ (exclusion) -thermal, or alternatively, NF ₂ -SWRO ₁ (exclusion) -thermal seawater desalination is a thermal desalination unit (MSFD or MED, Or VCD, or RH), the following advantages are obtained:

  (1) Due to the significant reduction of hard material, and consequently the reduction or absence of scale formation, to the feed to the SWRO or thermal desalination process as was done in conventional systems to prevent scale formation There is no longer a need to add scale-inhibiting chemicals. Of course, this is an important advantage from an environmental point of view. This is because such chemicals are no longer discarded into the marine environment, or into landfill sludge or water tanks.

  (2) Furthermore, due to the high purity of the NF product in that it does not contain suspended solids or bacteria, the pressure differential (ΔP) through the SWRO membrane remains very low, thus the SWRO membrane. Is not contaminated. This not only extends the life of the SWRO membrane (when used in a triple hybrid), but also continues to maintain high efficiency membrane performance without frequent cleaning.

(3) SWRO that has been conventionally operated due to the high quality of the SWRO product produced by using this dual NF ₂ -SWRO ₂ method as part of a triple hybrid thermal system, ie, drinking water quality A second stage RO unit, as is normally done in plants, is unnecessary, in which case this second stage is required to produce good quality water with TDS <500 ppm. Furthermore, the mixing of permeate and distillate gives the acceptability of high TDS permeate and again allows for extended life of the SWRO membrane.

(4) NF ₂ -SWRO ₂ (exclusion) —One main advantage of the triple hybrid of the present invention of the thermal method is that the quality of the SWRO exclusion is good, which is converted to thermal seawater desalination. Qualify as a supplement to the plant. As shown in Table 4, besides the high transparency due to the absence of suspended solids and bacteria, the scale-forming hard ions it contains, SO ₄ ⁼ , Mg ⁺⁺ , Ca ⁺⁺ , and HCO ₃ ⁻ The concentration of is low.

  When each of NF and SWRO is operated in two stages, the further usefulness of this product in a NF-SWRO (exclusion) -MSDD, or MED, or VCD, or RH triple hybrid desalination system is Increase the total water recovery of the process.

(5) Energy consumption for the method of the invention (only the membrane part) / product m ³ : this NF ₂ -SWRO ₂ (exclusion) -thermal formula: energy consumption for a conventional SWRO million gallon plant / m ³ has a ratio of 0.44: 1. The energy consumption (KW hour / m ³ ) of the method of the present invention for the NF ₂ -SWRO ₂ portion of the triple hybrid is approximately 44% of the value required for a conventional SWRO system operated without NF pretreatment. It is. The energy requirement was calculated according to Equation 3:
Energy (KW hour / m ³ ) = [Q _f . _{H f ρ / 366Q p e]} (3)
In the formula:
- Q _f and _{Q p} is the amount of each feed and product (unit, ^{m 3} / h).
-H is the pressure head (unit, m).
-Ρ is the density of seawater (1.03).
-E is the pump efficiency (≈0.85).

  See Water Treatment Handbook, 5th Edition, 1979, Halsted Press Book, John Wiley & Sons Publisher. “Pump Handbook” 2nd edition, Igor J.M. Karassik Willian C.I. Krutzsch, Warren H. Franchen (Warren H. Franser) and Joseph P. See also Joseph P. Messina, McGraw Hill Publisher, International Publishing, Industrial Engineerirg Series.

To further illustrate the advantages of the present invention, a fully integrated optimal dual NF (two stage) -thermal plant design for the production of Gulf Seawater feed, TDS 45,000 ppm, million US gallons per day (mgd) Was used to simulate a commercial plant. Gulf water NF recovery was set to 75%, and with TBT ≧ current limits, the operated thermal unit recovery was set to 72%, but higher distillate recovery of over 80% was achieved. Table 5 illustrates the many advantages over conventional thermal methods that can be obtained in recovery by applying the optimal NF (two-stage) -thermal seawater desalination method of the present invention. The amount of reject (brine) is also small. With a distillate recovery of 35%, this million US gallon / day plant supplement by conventional thermal method is 451.4 m at a feed ratio of 1: 0.65, 54% recovery. ³ / hr, compared to only 292.6 m ³ / hr in the NF ₂ -thermal method. Trihybrid construction of NF ₂ -SWRO 2 _- by thermal or is the same as shown in Table 5, it is possible to achieve even higher total water recovery rate than that. This is because the triple hybrid configuration achieves a higher recovery than that achieved by the double hybrid NF ₂ -thermal formula. As mentioned earlier, when SWRO exclusion is supplemented to one of the various thermal units of MSFD, MED, or VCD, or RH, higher amounts in the form of distillate and SWRO permeate Water can be recovered.

  In summary, the present optimal method of the present invention has a much higher efficiency than the conventional thermal or SWRO seawater desalination process operated alone. Furthermore, many of these advantages are not limited to application to the desalination of Gulf Seawater (TDS 45,000 ppm). Higher NF, thermal, and SWRO product recovery rates are achieved when the process is applied to desalination of ocean seawater (TDS 35,000 ppm) as well as a total recovery of about 65% or more with the dual hybrid. be able to. The amount of energy required, as well as the amount of feed and rejects, is expected to be significantly lower in the case of demineralization of the ocean seawater feed than in the case of desalination of the gulf seawater feed. This is mainly because higher NF product recovery rates of about 80% or more are obtained, especially when a suitable scale inhibitor is added to the NF unit feed.

Although not explicitly described above, it is clear that there are many aspects of the present invention that clearly fall within the spirit and scope of the present invention. Therefore, the above description should be considered as exemplary only, and the actual scope of the present invention should be determined only from the appended claims. As shown in FIG. 12, a similar claim can be made for making the NF product from the two-stage NF unit a feed to the two-stage SWRO ₂ , but the claims of the present invention are: the thermal unit MSFD, or MED, or VCD, or optimal dual NF (2 stages) when it is possible to RH - thermal, and triple _NF 2 -SWRO ₂ (elimination thereof) - thermal seawater desalination Limited to law only.

Cited Reference 4,036,685 9/1977 Bray
4,156,645 5/1979 Bray 4,341,629 7/1982 Uhlinger
5,238,574 8/1993 Kawashima, others 6,190,556B1 20/2/2001 Erlinger
6,508,936 1/203 Hassan
4,723,603 2/1998 Plummer
5,458,781 10/1995 Lin
EPO 09141260 03/6/1997 Tanaguchi, others

FIG. 1 shows turbidity, bacteria, hard ions, and TDS in the seawater desalination process that separates the feed into product and reject, various seawater desalination (thermal or membrane) processes. It is a graph which shows the density | concentration about. FIG. 2 is a graph of the main problems of various seawater desalination methods. FIG. 3 is a graph showing the effect of seawater feed TDS on osmotic pressure and the true effective pressure [Pnet] that pushes permeate through the membrane. Figure 4 shows a turbocharger energy recovery system placed during a stage coupled to a MSFD, MED, or VCD, or RH thermal unit, where the NF product constitutes a supplement to the thermal unit It is a typical process figure which shows the structure of NF pre-processing unit operated in two steps. FIG. 5 shows a NF and SWRO unit in two stages with an energy recovery turbocharger placed between the stages when the SWRO reject constitutes a supplement to the MSFD, MED, or VCD, or RH thermal unit. FIG. 3 is a schematic process diagram of a triple hybrid thermal desalination system using the FIG. 6 shows dual NF-MSFD, dual NF-SWRO, and NF in an NF-seawater desalination (SWRO and MSF) pilot plant, where each of the NF and SWRO units constitutes only one stage. It is a typical process figure showing composition of a triple hybrid by SWRO (exclusion) and MSF. Figure 7 shows a commercial Umm Lujj SWRO plant (a) SWRO configuration of a plant built in 1986 (Train 200), (b) Conversion to NF-SWRO system (NF and SWRO each in one stage) And is a schematic process diagram for an NF-SWRO configuration (train 100) operated in September 2000. FIG. FIG. 8 is a photograph showing a Umm Lujj NF-SWRO plant (train 100) converted to a new dual NF-SWRO hybrid desalination system in September 2000, with the installed NF unit coupled to it in the front The back of the photo is connected to the SWRO unit. FIG. 9 is a graph showing the performance of the NF membrane unit in the Umm Lujj NF-SWRO train 100 with a fixed NF product recovery of 65%. FIG. 10 shows the composition of the NF product and seawater feed of the same seawater feed to the NF unit, scale-forming hard ions (SO ₄ ⁼ , Ca ⁺⁺ , Mg ⁺⁺ , HCO ₃ ⁻ ), Cl ^- and focus on the content of TDS, illustrates with rejection of those ions by NF membrane (%). FIG. 11 is a graph showing the performance and operating conditions for the SWRO unit train 100 in the fully integrated NF-SWRO system shown in FIG. 7, product versus train 200 (SWRO) with train 100 (NF-SWRO). The observed ratio of product from is about 1.4 to 1.6: 1. FIG. 12 is a schematic process diagram for an optimal fully integrated seawater desalination process of the present invention having NF (two-stage) -SWRO (two-stage) with a turbocharger placed between two stages in each of the NF and SWRO units. It is. FIG. 13 is a process diagram showing the performance of an NF member using a pilot plant with three different pressurized vessel configurations, each being a pressurized vessel containing two NF8 ″ × 40 ″ members. FIG. 14 shows the concentrations of hard ions (Ca ⁺⁺ , Mg ⁺⁺ ), SO ₄ ⁼ , and HCO ₃ ⁻ , total hard material, TDS, and Cl ⁻ in NF products from seawater and its different NF membranes. It is a graph to show. FIG. 15 is a graph plotting NF performance as a first NF stage vs. operation time (9000 hours) using two pressurized vessels arranged in series, each containing two NF members. . FIG. 16 shows the NF unit performance of product (a) flow rate, (b) recovery rate, and (c) conductivity measured under various operating conditions of pressure, temperature, feed flow rate, and feed TDS. FIG. FIG. 17 shows the performance of SWRO unit (each of NF and SWRO consists of only one stage) with and without NF seawater pretreatment ((a) flow rate of permeate, (b) recovery rate) And (c) Conductivity] is a graph plotted against applied pressure. FIG. 18 shows that increasing the thermal unit (MSFD) brine operating temperature increases both production rate gain (GOR) and performance ratio (PR), in addition to reducing energy (E) consumption. FIG.

Claims (23)

Brine containing high concentrations of hard scale-forming ionic species, microorganisms, particulate matter and high concentrations of total dissolved solids into a two-stage membrane nanofiltration (NF ₂ ) unit and energy recovery turbocharger during those stages A (TC) unit is placed and replenished with a pressure pump as needed to form a first water product from the combined NF product of the first and second NF stages, or said stage Generating the first product from an NF unit having a pressure pump in between, wherein the first water product is generated from an NF unit with an energy recovery pressure exchanger (PX). On the other hand, the NF unit itself consists of two stages and a pressure pump disposed between the stages, in which case the first water product has a reduced content of the ionic species. A process in which microorganisms, particulate matter and most scale-forming hard ions are removed therefrom, and then the first water product is passed through a thermal seawater desalination unit to produce a final second water production. Optimal desalination method and apparatus comprising the steps of producing a product (distillate) and a brine discharge (blowdown). Seawater containing a high concentration of hard scale-forming ionic species, microorganisms or particulate matter and total dissolved solids is passed through a two-stage membrane nanofiltration (NF ₂ ) unit according to claim 1 and the ionic species Producing a first water product in which the content of (TDS) is reduced and microorganisms, particulate matter and most scale-forming hard ions are removed;
Thereafter, the first water product is passed through a one-stage or two-stage seawater reverse osmosis unit, where the one-stage SWRO comprises an energy recovery PX unit and a high-pressure permissible membrane (P = 84 bar). While the two-stage SWRO unit has an energy recovery TC from brine, as shown in FIG. 5, and the drinking water quality third water product (permeate) and salinity increase However, the hard material forms a dramatically reduced quaternary water product exclusion, and then the quaternary water product exclusion is passed through a thermal desalination unit to improve drinking water quality. A desalting process comprising forming a second water product (distillate) and a brine discharge blowdown.   The thermal distillation unit comprises a multi-stage flash distillation (MSFD) unit or a multi-effect distillation (MED) unit or a vapor compression distillation (VCD) unit, or a vapor compression multi-effect evaporator thermal reheating (RH) unit. Item 3. A desalting method according to Item 1 or 2. Has a double fully integrated NF ₂ unit with energy recovery PX or TC system, where the first NF stage has a high pressure pump and NF unit and produces NF under a pressure (P) of 25 ± 10 bar And the NF reject constitutes a feed to the second stage NF after passing it through a turbocharger unit or a pressurized pump or a combination thereof. The optimal desalination method and apparatus according to claim 1 or 2, wherein the product from the NF unit constitutes the first water product together with the NF product from the first NF stage.   The first SWRO stage has a high-pressure pump and sends feed to the SWRO unit at P = 60 ± 10 bar, from which it produces SWRO product and reject stream, said SWRO reject stream being a turbocharger or pressurized pump or The energy recovered from the second SWRO stage reject through this combination increases its pressure to 85 ± 10 bar, after which it is fed to the second stage SWRO unit for drinking water quality 3. The optimum desalting method and apparatus of claim 2 that forms a third SWRO product and a fourth SWRO exclusion. The SWRO ₁ unit has a high-pressure pump and sends it to a high-pressure permissive membrane up to 84 bar at a pressure of P = 75 ± 10 bar, a part of the feed to the SWRO membrane (first part) is their product (permeate ), The first portion of this pump pressurized (P = 75 ± 10 bar) NF product, the second portion of the NF product equal to the SWRO ₁ exclusion, and the second portion through the PX unit. were mixed and then, the PX unit raises the pressure so that at all equal to the SWRO ₁ unit brine (PX) pressure in the first part by recovered energy (P = 75 ± 10 bar), SWRO ₁ 3. The feed as a unit, wherein the combined NF product of the same pressure produces a drinking water quality third water permeate product and a reject as a fourth water product reject. of Suitable desalting method and apparatus. Medium to high product stream and large scale-forming hard ion exclusion rate: using NF membranes with an exclusion rate of over 90% for SO ₄ ⁼ and an exclusion rate on the order of 60-98% for other hard ions, 3. The optimum desalination system according to claim 1 or 2, wherein the second stage NF membrane is characterized by a large product stream and a high rejection rate and has a high pressure tolerance up to 40 bar and above.   A turbocharger alone, or in combination with a pressure pump, or the pressure pump itself, capable of receiving a high pressure feed, will reduce the pressure of the feed to the second NF stage from 25 ± 10 bar to 35 ± 10 bar or The optimum desalination system according to claim 1 or 2, which can be increased further.   A turbocharger alone, or in combination with a pressure pump, or the pressure pump itself, capable of receiving a high pressure feed, will reduce the pressure of the feed to the second SWRO stage from 60 ± 10 bar to 85 ± 10 bar or The optimum desalination system according to claim 2, which can be increased further.   First-stage SWRO, a commercial SWRO membrane of the kind used in conventional one-stage SWRO plants, has a high salt rejection of over 99.0% and can withstand pressures up to over 70 bar. The optimum desalination system according to claim 2, wherein higher quality membranes are used, while high pressure tolerant SWRO membranes up to 90 ± 10 are used in the second stage SWRO.   The optimum desalination system according to claim 2, wherein the first and second stage SWRO use pressurized vessels capable of withstanding pressures up to 70 and 100 bar, respectively.   The optimal desalination system according to claim 1 or 2, wherein the salt water includes seawater.   12. The optimum desalination system according to claim 11, wherein the seawater has a total dissolved solids content on the order of 2.0% to 5.0%.   The seawater solution has a cation content of the order of 1.2% to 1.7%, an anion content of the order of 2.2% to 2.8%, and a pH of the order of 7.9 to 8.2. 12. An optimum desalination system according to claim 11, having a total dissolved solids content on the order of 2.0% to 5.0%.   14. The optimum desalination system of claim 13, further having a cation content comprising 700-2200 ppm calcium and magnesium cations. Regarding the properties of seawater, the content of calcium, magnesium, sulfate and bicarbonate ions is reduced to the order of 63% to 99% by NF ₂ units, and the total dissolved solids content is reduced by about 30% to 50%. The optimum desalting system according to claim 11 or 13.   The optimum desalination system according to claim 1 or 2, wherein the nanofiltration unit is operated at a temperature on the order of 15 ° C to 40 ° C.   The optimum desalination system according to claim 2, wherein the seawater reverse osmosis unit is operated at a temperature on the order of 15 ° C to 40 ° C.   The MSFD thermal unit is operated at a maximum brine temperature (TBT) ≧ 120 ° C. to 160 ° C., while the MED or VCD or RH type thermal unit is operated at TBT ≧ 70 ° C. to 120 ° C., The optimum desalination system according to claim 1 or 2.   The desalination process according to claim 1, wherein the second water product comprises drinking water and the product recovery ratio to seawater feed is on the order of 54% or more.   The third water product contains drinking water (SWRO permeate) and its product recovery is on the order of 69% relative to the amount of NF product it receives as a feed with a TDS of about 28,500 ppm. 3. A desalination process according to claim 2, wherein there is an increase as feed TDS decreases.   The combined total water product with drinking water quality is equal to the sum of both the second and third water products, and its total drinking water recovery is on the order of 60% or more, and its value is 3. A desalination process according to claim 2, which is greater than any conventional thermal seawater desalination recovery rate for seawater feed with TDS = 45,000 ppm.   The desalination method according to claim 1 or 2, wherein seawater is sent to the NF unit with or without a suitable scale inhibitor.

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