EA004968B1

EA004968B1 - Process and plant for multi-stage desalination of water

Info

Publication number: EA004968B1
Application number: EA200300493A
Authority: EA
Inventors: Пауль Майкл Уильсон; Георг Эндрью Аткинсон
Original assignee: Парсонс Бринкерхофф Лтд.; Пбс Интернэшэнэл, Инк.
Priority date: 2000-10-21
Filing date: 2001-07-18
Publication date: 2004-10-28
Also published as: GB2369783A; EA200300493A1; DZ3474A1; GB2369783B; KR100783686B1; GB0117455D0; MA25954A1; JO2223B1; EG22839A; KR20030041854A; WO2002032813A1; AU2001270867A1

Abstract

1. A process for the desalination of salt water comprising the steps of: (a.) providing a brine heater; (b.) providing at least one desalination zone comprising a condenser and means for collecting condensate from the condenser; (c.) providing a heat exchanger; (d.) supplying a feed stream comprising salt water as a coolant to the condenser to pre-heat the feed stream; (e.) supplying the pre-heated feed stream to the brine heater; (f.) supplying a first heating stream comprising steam to the brine heater further to heat the pre-heated feed stream; (g.) optionally recovering at least a portion of the first heating stream from the brine heater; (h.) supplying the heated feed stream from the brine heater to the at least one desalination zone, evaporating at least a portion of the heated feed stream in the desalination zone to provide an evaporate comprising water vapor and condensing the evaporate on the condenser in the desalination zone; (i.) recovering from the desalination zone a product stream comprising the condensate and a depleted feed stream comprising salt water; (j.) supplying as a thermal recycle stream a portion of the product stream to the heat exchanger; (k.) supplying a second heating stream, optionally comprising at least a portion of the recovered first heating stream, to the heat exchanger to heat the thermal recycle stream; and (l.) supplying the heated thermal recycle stream to the at least one desalination zone. 2. A process for the desalination of salt water comprising the steps of: (a.) providing a brine heater; (b.) providing at least one desalination zone comprising a condenser and means for collecting condensate from the condenser; (c.) providing a heat exchanger; (d.) supplying a feed stream comprising salt water as a coolant to the condenser to pre-heat the feed stream; (e.) supplying the pre-heated feed stream to the brine heater; (f.) supplying a first heating stream comprising steam to the brine heater further to heat the pre-heated feed stream; (g.) optionally recovering at least a portion of the first heating stream from the brine heater; (h.) supplying the heated feed stream from the brine heater to the at least one desalination zone, evaporating at least a portion of the heated feed stream in the desalination zone to provide an evaporate comprising water vapor and condensing the evaporate on the condenser in the desalination zone; (i.) recovering from the desalination zone a product stream comprising the condensate and a depleted feed stream comprising salt water; (j.) supplying as a thermal recycle stream a portion of the depleted feed stream to the heat exchanger; (k.) supplying a second heating stream, optionally comprising at least a portion of the recovered first heating stream, to the heat exchanger to heat the thermal recycle stream; and (1.) supplying the heated thermal recycle stream to the at least one desalination zone. 3. A process for the desalination of salt water comprising the steps of: (a.) providing a brine heater; (b.) providing at least one desalination zone comprising a condenser and means for collecting condensate from the condenser; (c.) providing a heat exchanger; (d.) supplying a feed stream comprising salt water as a coolant to the condenser to pre-heat the feed stream; (e.) supplying a first portion of the feed stream as a pre-heated feed stream to the brine heater; (f.) supplying as a thermal recycle stream a second portion of the feed stream to the heat exchanger; (g.) supplying a first heating stream comprising steam to the brine heater further to heat the pre-heated feed stream; (h.) optionally recovering at least a portion of the first heating stream from the brine heater; (i.) supplying a second heating stream, optionally comprising at least a portion of the recovered first heating stream, to the heat exchanger to heat the thermal recycle stream; (j.) supplying the heated feed stream from the brine heater and the heated thermal recycle stream from the heat exchanger to the at least one desalination zone, evaporating at least a portion of the heated feed stream and the heated thermal recycle stream in the desalination zone to provide an evaporate comprising water vapor and condensing the evaporate in the desalination zone; (k.) recovering from the desalination zone a product stream comprising the condensate and a depleted feed stream comprising salt water. 4. A process according to claim 1, wherein the heated thermal recycle stream is supplied to the condensate collecting means of the desalination zone. 5. A process according to claim 4, wherein the ratio of thermal recycle stream to condensate in the collecting means of the desalination zone is from about 0.85: 1 to about 1.15: 1. 6. A process according to any one of claims 1 to 5, wherein there is provided a plurality of desalination zones connected in series. 7. A process according to claim 6, wherein the thermal recycle stream is taken from a first desalination zone and the heated thermal recycle stream is supplied to a second desalination zone. 8. A process according to claim 7, wherein the second desalination zone is nearer in the series of desalination zones to the brine heater than is the first desalination zone. 9. A process according to claim 8, wherein the first desalination zone is maintained at a lower pressure than the second desalination zone. 10. A process according to any one of claims 1 to 9, wherein the thermal recycle stream is supplied to the heat exchanger at a pressure greater than that of the second heating stream supplied to the heat exchanger. 11. A process according to any one of claims 1 to 10, wherein the feed stream is supplied to the brine heater at a pressure greater than that of the first heating stream supplied to the brine heater. 12. A process according to any one of claims 1 to 11, wherein the temperature of the thermal recycle stream is not more than 5 degree C greater than the saturation temperature of water in the at least one desalination zone. 13. A process according to any one of claims 1 to 12, comprising recovering at least a portion of the first heating stream from the brine heater. 14. A process according to claim 13, wherein the second heating stream comprises at least a portion of the recovered first heating stream. 15. A process according to any one of claims 1 to 14, wherein a plurality of heat exchangers for heating the thermal recycle stream are provided. 16. A plant for the desalination of salt water comprising means for operating a process according to any one of claims 1 to 15.

Description

The present invention relates to a method and apparatus for the desalination of salt water, in particular, sea water.

Known desalination plants operate using a multistage flash evaporation process (MMI). Instant evaporation is a process in which water vapor evaporates from saline water and then the water vapor that forms is condensed and collected. Water can be brought to a boil, for example, by reducing the pressure. In the MMI process, salt water is successively fed to a series of flash zones and in each zone, salt-free condensate is collected.

Currently, in many regions of the world where there is a shortage of fresh water, there is a growing need for effective salt water desalination technology. The need for such technology is likely to increase significantly due to the increasing water deficit caused by global warming and the increasing demand for fresh water.

Desalination technologies using multistage flash evaporation are currently used on an industrial scale to supply fresh water in arid regions of the world where access to brackish and / or seawater is available. However, the capital and operating costs of installations of this type are high, mainly due to the large volume of water required to carry out the process and the energy costs required to evaporate large volumes of water vapor at a sufficiently high rate. In order to reduce energy consumption to a minimum, the MMI technology was used on an industrial scale in conjunction with power units in order to use the generated thermal energy.

Despite the increase in the energy efficiency of desalination plants, there is still a need to create an improved method and device for desalination of salt water, which will increase energy efficiency and, thus, reduce costs and reduce damage to the environment due to the operation of known desalination plants.

With such methods of desalination, low specific steam consumption is required for the desalination process in order to minimize the energy consumed from the fuel, as well as to produce energy and water at minimal cost.

In accordance with the present invention, a method for the desalination of salt water is proposed, comprising the following steps:

a) providing a means for heating the brine;

b) providing at least one desalination zone comprising a condenser and a device for collecting condensate from the condenser;

c) provision of a heat exchanger;

) supplying a feed stream consisting of salt water as a coolant to a condenser for preheating the feed stream;

e) supplying a preheated feed stream to a brine heating device;

ί) supplying the first heating stream to the brine heating device for additional heating of the pre-heated feed stream;

d) selectively removing at least part of the first heating stream from the brine heating device;

11) supplying the heated feed stream from the brine heating device to at least one desalination zone, evaporating at least a portion of the heated feed stream in the desalination zone in order to produce steam containing steam, and condensing steam on the condenser in the desalination zone;

) removing from the desalination zone a stream of product containing condensate and a waste feed stream containing salt water;

_)) feeding part of the product stream to the heat exchanger as a heat recycle stream;

k) supplying a second heating stream, optionally including at least a portion of the extracted first heating stream, to a heat exchanger for heating the heat recycle stream; and

l) feeding the heated thermal recycle stream to at least one desalination zone.

The method according to the present invention allows to increase the thermal efficiency of the desalination process in comparison with the efficiency of the known desalination plants. The supply of a heated thermal recycle stream to the desalination zone is an effective means of returning thermal energy (which could otherwise be wasted) to the desalination zone, thereby reducing the total energy consumption required for the operation of the plant.

In another method according to the present invention, the heat recirculation can be achieved by the spent feed stream rather than the product stream. The feed stream for heat recycling can be removed from the desalination zone. Thus, in accordance with the invention, another method for the desalination of salt water is proposed, comprising the following steps:

a) providing a means for heating the brine;

c) provision of a heat exchanger;

d) supplying a feed stream consisting of salt water as a coolant to a condenser for a pre-feed heating stream;

e) supplying a preheated feed stream to a brine heating device;

11) supplying the heated feed stream from the brine heating device to at least one desalination zone, evaporating at least a portion of the heated feed stream in the desalination zone in order to produce steam consisting of water vapor, and condensing the steam on the condenser in the desalination zone;

) removing from the desalination zone a stream of product containing condensate and a waste stream containing salt water;

k) feeding a second heating stream, selectively consisting of at least a portion of the selected first heating stream, to a heat exchanger for heating the heat recycle stream; and

l) feeding the heated thermal recycle stream to at least one desalination zone.

In addition, (or also) the thermal recycle stream can be removed from the feed stream before it is fed to the brine heating device. Accordingly, according to the present invention, there is also provided a method for desalination of salt water, comprising the following steps:

a) providing a means for heating the brine;

b) providing at least one desalination zone comprising a condenser and a device for collecting condensate from the condenser,

c) provision of a heat exchanger;

d) supplying a feed stream consisting of salt water as a coolant to a condenser for preheating the feed stream;

e) feeding the first part of the feed stream as a pre-heated feed stream to a brine heating device;

) supplying the second part of the feed stream as the heat flow of the recirculating product to the heat exchanger;

d) the supply of the first heating stream in the device for heating the brine for additional heating of the pre-heated feed stream;

1) selectively removing at least a portion of the first heating stream from the brine heating device;

) feeding the second heating stream, selectively including at least a portion of the selected first heating stream, to a heat exchanger for heating the heat recycle stream;

_)) supplying a heated feed stream from a device for heating brine and a heated heat recycle stream from a heat exchanger to at least one desalination zone, evaporating at least part of the heated feed stream and a heated heat recycle stream in the desalination zone in order to produce steam that includes water steam, and steam condensation in the desalination zone;

K) extraction from the desalination zone of the product stream, including condensate, and the remaining feed stream, including salt water

If at stage _) there is more than one desalination zone, then the desalination zone, to which the heated feed stream and the heated recycle stream are respectively supplied, may be the same zone or another zone.

In accordance with the method of desalination according to the present invention provides a significant increase in the energy efficiency of known desalination plants, such as installations MMI. The method of desalination according to the present invention consists in heating the salt water and then in the instantaneous evaporation of the heated salt water in the desalination zone.

It is preferable to create several consecutive desalination zones, thereby ensuring consistent instantaneous evaporation of salt water as it passes through a series of desalination zones. Preferably, in several successive desalination zones, a lower pressure is consistently maintained. In each desalination zone, instantly evaporating steam condenses on a condenser and collects condensate. The condenser preferably includes at least one pipe through which the refrigerant flows, and the collection device includes a tray for fresh water in which the condenser pipe is located. In this case, the fresh water tray connects all the desalination zones, and the resulting water is cascaded from one stage to another along with the raw material flow, and at each stage instantaneous evaporation occurs, and water from the vapor generated by instant evaporation is regenerated in the tray.

Preferably, the first heating stream supplied to the brine heating device comprises steam. Steam may be supplied from a connected steam generator.

In accordance with the method of the present invention, a single heat exchanger can be used to heat the heat recycle stream. Alternatively, several heat exchangers may be used. In this case, if necessary, several heat exchangers can be connected in series or in parallel.

Preferably, the refrigerant supplied to the condenser tubes is an unheated feed stream. The feed stream, as such, may include makeup water, for example, seawater and recycled product from the desalination zone. In this case, the condensation tubes in each section of the desalination zone are cooled by recirculation and / or additional supply of the feed stream flowing through the zones in the direction opposite to the feed stream subjected to flash evaporation. Thus, preheating of the recirculating feed stream occurs prior to its supply to the brine heating device. After passing through the brine heating device, the feed stream is fed through a control valve for instant evaporation in the first desalination zone. Using a control valve, the feed pressure is preferably maintained above the vapor pressure in the device for heating the brine in order to prevent boiling up of the feed stream inside the heat exchange zone, as well as to avoid possible leakage of steam into the feed stream, since the steam can be contaminated with toxic chemicals used for the treatment of boiler water. Otherwise, this would lead to contamination of the water obtained at the MMI installation, if leakages from the pipes of the brine heating device occur.

In accordance with one of the preferred methods, condensation tubes in the coldest stage of the MMI installation, in the heat removal section, are cooled by circulating seawater to remove used heat from the cycle and increase the production of fresh water to the maximum level. For recirculation through the installation of a cooled feed stream as a result of instantaneous evaporation, powerful pumps are used at the stage with minimal pressure. The resulting water is replaced by the feed coming from the seawater outlet pipe and supplied from the heat removal stage, which has the highest temperature, which passes deaeration and returns to the lowest pressure stage. The concentration of the recirculating and / or feed flow is regulated by continuously blowing a small amount of brine from the stage with the lowest pressure to the seawater drain line.

At each stage of instantaneous evaporation of the feed stream, the formation of some non-condensable gases can occur. These gases can be removed through a system of vents and vacuum ejectors in order to prevent a decrease in the efficiency of the condensation surfaces of the stages due to their isolation with such gases, which leads to a decrease in the performance of the MMI unit. Similar systems in the brine heating device ensure the maintenance of heat transfer efficiency by removing non-condensable gases. The use of such systems provides an extremely low level of dissolved gases in the resulting water and the second heating stream.

The design of desalination plants MMI includes other options for creating a scheme for each stage of heat exchange and desalination and the choice of several stages, forming part of the entire installation. The direction of movement of the feed stream undergoing instantaneous evaporation may be parallel to the flow of the recirculating and / or feed flow, which is the so-called long-tube design, or it may be perpendicular to this flow, representing the so-called cross-flow design. The number of steps in the desalination plant is not limited. For example, in accordance with the method of the present invention, the installation may include about 20 or more desalination zones, with the capacitors in the first consecutive zones being cooled by the supply stream, which is subsequently heated in each zone as it moves to the device to heat the brine, and the condensers last zones are cooled with cold sea water to ensure maximum condensation.

Heat exchanger tubes can be made of any acceptable material, for example, nickel silver, brass, titanium and stainless steel of various grades and specifications to ensure resistance to chemically aggressive hot seawater flowing at the rate necessary to maintain optimum heat transfer. It is necessary to prevent scale buildup.

Heat transfer surface forming insoluble minerals from hot seawater by metered delivery of chemicals and circulation of soft rubber spheres in the water flow. The choice of pipe diameter is limited by such methods of mechanical cleaning, limiting the optimization of heat exchange efficiency and costs. In addition, chemical cleaning methods can be used.

In the well-known MMI installations, the surface area of the heat exchanger tubes in each step and the number of steps determine the amount of steam needed to produce a unit of product produced by the MMI installation. A significant increase in the heat transfer surface is necessary to reduce the specific steam consumption, for example, to achieve a 5% reduction in the specific steam consumption, it is necessary to increase the heat transfer surface by 15%, which will lead to significant additional costs.

Known installations include a device for heating brine, which uses thermal energy of low-pressure saturated steam and temperature (usually the saturation temperature does not exceed 115 ° C) for heating the feed stream before the process of instant evaporation in the first stage of the MMI installation. Water condensed in the device for heating the brine from the supplied steam is pumped to the steam-generating unit at a temperature close to the saturation temperature of the steam in the device for heating the brine.

According to the method of the present invention, the first heating stream may include steam from the steam generator installation, in which case, in accordance with the method of the invention, an additional step of utilizing the second heating stream from the heat exchanger and returning the recovered stream to the steam generator may be included. In this case, the temperature of the condensate returned to the steam generator installation determines the lowest temperature to which the installation can cool the flue gases. In practical heat recovery steam generators, the difference in the range of 15-20 ° C between flue gases and the temperature of the water of the returned condensate is standard. As a result, the temperature of the flue gases in this type of plants for the production of energy and water exceeds 130 ° C. In those cases, if gas is used as fuel in such installations for the production of energy and water, the temperature of the flue gases below 100 ° C would be acceptable, but at a higher temperature of water in the return pipe. A higher temperature of the flue gases leads to a decrease in the efficiency of using thermal energy in the whole process, as a result of which a few percent increase in the amount of heat supplied is required, which leads to significant costs and fuel consumption during the entire service life of the installation.

Thus, in accordance with the method of the present invention, a method is proposed for increasing energy efficiency in a desalination plant and a combined energy and multistage desalination plant. According to the method of the present invention, an energy and desalination plant is proposed with a reduced consumption of fuel energy with a relatively slight increase in the total cost. The present invention provides a reduction in steam consumption by the MMI desalination plant for a given fresh water production, while reducing the power, size and cost of the steam generating plant and any associated steam turbines, steam pipelines, valves and supporting structures. In accordance with the method of the present invention, steam consumption is reduced by installing an MMI without increasing the number of stages in an MMI installation or changing the technical requirements for heat transfer surfaces in an MMI installation. In accordance with the method of the present invention, steam consumption is reduced at lower costs than with other options for increasing the heat transfer surface or the number of stages. The present invention only slightly changes the operation of the MMI installation, the design of which can be modified as standard for mounting connections for the heat flow of the recirculating product and heat exchanger connections in the exhaust pipe of the second heating stream, or the exhaust pipe. Thus, the present invention can be easily used in existing installations MMI with minimal modifications. The heat exchanger in the second heating stream has a small surface area required to achieve the required benefits and, in the case when the produced water is used as the heat flow of the recycled product, the heat exchanger can be made of cheaper and more technologically advanced materials that are not resistant to seawater, since the water flowing through the internal and external circuits of the heat exchanger is fresh water containing only a small amount of dissolved oxygen. The present invention avoids any possible contamination of the produced water with toxic chemicals to treat the boiler in the second heating stream by insulating the condensate from the produced water even if the heat exchanger tubes fail by creating a higher pressure of the produced water in the heat exchanger compared to the pressure in the device for heating the brine before recirculation of the produced water in the MMI installation is ensured. In accordance with the present invention, a heat flow of the recirculating product is proposed that does not affect the operation of the MMI installation, with the exception of steam consumption. Stopping or failure of any part of the auxiliary water circuit only affects steam consumption and does not adversely affect the continuity of production of the MMI installation, which is often an important requirement.

Heat recovery from the second heating stream in the heat exchanger can be maximized by using a heat exchanger with a low log-average temperature difference (CPT). In cases where the thermal recycle stream contains the produced water, the pure water used in the heat exchange process allows the use of a plate-shaped heat exchanger in order to achieve high heat exchange efficiency with low CPT at an economically advantageous price. In other embodiments, the tubular heat exchanger of small dimensions, having an acceptable surface area, provides effective heat recovery. The optimal range of CPT for the heat exchanger is from 3 to 20 ° C.

The heat exchanger may be located on the outside of the brine heating device, with the recovered first heating stream (which may be condensate) being withdrawn or pumped into the heat exchanger as a second heating stream in whole or in part. The second heating stream may contain hot water from other sources or from other devices used in the process. Alternatively, the heat exchanger may be combined with a device for heating the brine in an acceptable package. The internal layout does not require the installation of pipe connections and a separate housing for the heat exchanger, thereby simplifying the design and installation of the installation.

The movement of the thermal recycle stream relative to the second heating stream affects the heat recovery from the second heating stream. The ratio of these flows is preferably in the range from 0.5 to 1.15, more preferably from 0.7 to 1.15, and most preferably in the range from 0.85 to 1.15.

In cases where the thermal recirculated flow is supplied from the desalination zone, the degree of discharge from the zone determines the minimum temperature of the second heating stream in the return pipeline. When using more than one desalination zone, as is the case with the preferred method in accordance with the invention, the minimum point for selection is the desalination zone of the MMI installation with minimal pressure. The maximum point is the next stage at which the pressure is lower than at the stage to which the heat flux of the recirculating product returns. Selecting a thermal recycle stream from a higher pressure stage allows to increase the minimum temperature of the second heating stream in the return pipeline, which may be an advantage in optimizing the efficiency and cost of the combined energy and water desalination plant, although this reduces the efficiency of steam consumption by the MMI unit.

In accordance with the preferred method of the invention in which several desalination zones are used, the MMI installation zone to which the thermal recycle stream is returned affects the efficiency of heat transfer to the desalination zone. The optimum stage operates at a pressure below the pressure of saturated steam of water, corresponding to the temperature of the heat recycle stream.

It is desirable to prevent the second heating stream from mixing, which may be contaminated with chemical impurities for treating the boiler water, with the thermal recycle stream. The heat exchanger ensures the separation of these streams under normal conditions. Separation can be ensured even if there is a leak in the heat exchanger, if the pressure in the heat recycle loop is maintained above the pressure in the second heat flow path. This can be achieved using a device for maintaining pressure, installed on the maximum pressure of the device for heating the brine in the heat recycle loop between the outlet of the heat exchanger and the outlet for the circulating flow in the MMI installation. This device may be a control valve and monitoring equipment connected to it, or it may be a spillway in a tank connected to a recirculation stage and located in a water circuit at a height sufficient to ensure that the sum of pressure of the recirculation stage and static pressure water below the edge of the weir always exceeded the pressure of the brine heating device.

The invention is described in more detail with reference to the following drawings, in which FIG. 1 is a block diagram of a known multi-stage flash evaporation desalination plant;

FIG. 2 - the first cross section of a known installation of MMI with a flow in two directions;

FIG. 2a shows a second cross section along the line A-A in FIG. 2;

FIG. 3 is a block diagram of a desalination plant for multi-stage flash evaporation, intended for operation in accordance with the first method of the present invention;

FIG. 4 is a cross-sectional view illustrating one example of a structure for withdrawing produced water from a tray as a heat recycle stream;

FIG. 5 is one example of an external heat exchanger arrangement;

FIG. 6 shows another example of the arrangement of a heat exchanger inside a device for heating brine;

FIG. 7 - the design of the pipeline connection to return recycled high-temperature heat recirculating flow in a stage with a higher temperature;

FIG. 8 is a block diagram of a desalination installation of multi-stage flash evaporation, having a design for operation in accordance with the second and third method of the present invention;

FIG. 9 is another example of piping connections for collecting spent feed for thermal recycling;

FIG. 10 - external location of the heat exchanger during recirculation of the feed stream;

FIG. 11 is a structure for returning a high temperature recycled feed stream to a higher temperature stage.

A block diagram of a multi-stage desalination process is shown in FIG. 1. The preheated recirculated feed stream is heated in device 1 to heat the brine before it is supplied through valve 3 to maintain pressure for instant evaporation in the first desalination stage. The feed stream undergoes instantaneous evaporation passing through a series of desalination zones 4, while the steam condenses on tubes 5 cooled by recirculating and feed feed. The resulting water is collected in tray 6 and its sequential instantaneous evaporation occurs between the steps up to the heat removal stage 7. The desalination zones can be equipped with several cascaded heat removal stages. The recirculation of the feed stream is carried out by means of pumps 8 through desalination zones and heat removal stages.

Non-condensable gases are removed, successively pass through the steps and extracted using an ejector 9 from the lowest pressure stage equipped with a condenser 10 cooled by seawater. The condensation sections of the heat removal steps are cooled by seawater 11. The return of warm seawater is used to ensure the cycle through the deaerator 12 and make-up pump 13.

FIG. 2 and 2a shows the appearance of the desalination stage of the known installation MMI. The feed stream is fed to the stage through the weir 14. The steam is distilled off under vacuum, passes through the steam trap pads 15 and is condensed on a bundle of pipes 16 cooled by the feed stream. The resulting water is collected in the tray 17 and flows into the tray 18, from which it flows through the weir into the tray of the next stage. Non-condensable gases released from the instantly evaporating feed stream are discharged through the vent pipe 19 to the ejector system.

FIG. 3 shows the MWI cycle modified in accordance with the present invention when the produced water is used as a thermal recycle stream. Condensate from the brine heating device 1 'flows through the heat exchanger 147 before it is returned to the steam generator. Part of the water produced is recycled by taking it out of the water desalination stage of the MMI 3 'installation with a lower pressure. This water is pumped through the pump 145 to the secondary circuit of the heat exchanger 147. Flow from the heat exchanger outlet is pressurized using the valve 150 to maintain pressure, or the weir device 151 (with the alternative pipes shown in dashed lines) before it is returned to step tray with a higher pressure desalination zone 121 installation MMI.

FIG. 4 shows the connection to the channel 18 for transporting the produced water to the hot condensate well 20, from which the produced water is drained.

FIG. 5 shows a diagram of a device 126 for heating brine, located above the ground level and adjacent to the desalination section of the MMI 120 installation. The heat exchanger 147 has the shape of a tubular heat exchanger 21, is located at ground level, adjacent to the device 126 for heating the brine, and is connected to a well using pipes for hot condensate 22 of the second heating stream, while the second heating stream flows through the casing of the heat exchanger before it is discharged into the associated steam generator (not shown in Fig.). Heat recycle stream from the desalination zone with a relatively lower pressure is supplied through the pipe to the end 146 of the heat exchanger 147 and is heated by passing through the heat exchanger 147 and then through the pipe into the pipe 148 to the water tray of the desalination zone with a relatively higher pressure. The plate-frame heat exchanger is mounted in a similar way.

FIG. 6 shows the design of the device 126 for heating the brine, in the case of which a heat exchanger 147 'is located. The tube bundle is located inside the outer tubular casing, directing the second heating flow from the heat exchanger inlet 23 to the outlet 24, from which the second heating flow flows through the pipes through the casing of the device for heating the brine. The recirculated heat recycle is recycled to the heat exchanger through the discharge tube from the end 146 'of the second heating stream, while the high-temperature heat recycle product is fed through the pipe from the opposite end 148' to the return pipe and then to the tray.

FIG. 7 shows a pipe connection through which the hot water product returns to the tray 25 of the feed stream of the high-temperature stage of the MMI device. Received recirculating water is fed through an external connecting pipe 154 to the distribution well and weir 151 or to the sprinkler, from which it is discharged above the level of water produced in the tray.

FIG. 8 shows a modified MMI cycle in accordance with the present invention, in which the feed stream is recycled. Condensate from the brine heating device 1 ', to which hot water is added from the heat cycle 154', flows through the heat exchanger before it is returned to the steam generator (not shown in the figure). Partial recirculation of the feed stream from the desalination stage 3 'is carried out either by taking a stage with a lower pressure from the feed channel and further pumping it, or by taking a stage from the main recycle and / or feed stream between the sets of stage condensation pipes. compounds are shown by a dotted line.

Regardless of the way the feed stream is taken from the lower pressure stage, it is piped to the secondary circuit of the heat exchanger. The flow from the exhaust pipe of the secondary circuit of the heat exchanger is supplied under pressure using a valve 150 'to maintain pressure before it is returned to the channel 149' of the supply stream of the stage with a higher pressure of the desalination section of the MMI

FIG. 9 shows another variant of the selection of the feed stream from the desalination stage of the MMI installations. The feed stream is taken from the feed stream channel 26 through the hot condensate well 27. In accordance with another option, the feed stream is taken from the main ring pipe for the recycle or feed stream or from the pipes 28 connected to it.

FIG. 10 is a diagram of a device 29 for heating brine, located above ground level and placed near the desalination section of the MMI unit 30. The multi-pass shell-and-tube heat exchanger 31 is located at ground level next to the device for heating brine, and from it liquid is pumped into the second condensate well 32 heating flow. In this case, the condensate flows alternately through the passages of each casing of the heat exchanger before it is diverted to the steam generator (not shown in Fig.). The cooled recirculating feed stream is fed through a pipeline into the tubular circuit of the first stroke of the heat exchanger adjacent to the condensate outlet pipe 33, and, leaving the outlet of the last stroke of the tubular loop of the heat exchanger 34, is fed into the return port to the feed flow channel.

FIG. 11 shows the return pipe for feeding the feed stream to the feed channel 35. Using a sprinkler or distribution well 36, the high-temperature feed stream returns to the channel and is distributed over part of the width of the feed channel.

It should be understood that the design of the installation, the piping of control valves, pumps, exhaust valves, flow regulators and other elements of the standard equipment shown are given only as examples, and that the method and apparatus of the present invention are not limited to the above construction.

The following is a more specific description of the invention with reference to the following examples. Example 1 shows a method in accordance with the present invention, in which a portion of the produced water is recycled as a heat stream of recycled product.

Example 1

As seen in FIG. 3, the flow of seawater is supplied to pipeline 100 at a flow rate of 6638.9 kg / s and at a temperature of 35 ° C. Salinity of sea water is 4.45%. A portion of the seawater flowing through conduit 100 is supplied to conduit 101 as the refrigerant of the air ejector 102. The air ejector / condenser 102 is installed in the pipeline 103 to which a mixture of water vapor and non-condensable gases (mainly air) discharged with an extractor is fed 104 from step 105 heat removal. Non-condensable gases are discharged into conduit 106a, and any residual condensable materials are diverted from the air ejector / condenser 102 to conduit 106. In this example, the flow rate of seawater in conduit 101 is 250 kg / s.

The remaining seawater from the pipeline 100 (at a flow rate of 6388.9 kg / s) is supplied to the pipeline 107 as a coolant of the heat removal stage 105. The cooling sea water in the pipeline 107 is heated, passing through the heat removal stage 105, to a temperature of 42.68 ° C, and a part of it (at a flow rate of 1819.5 kg / s) is supplied to the pipeline 108 as make-up water. The remainder of the seawater in the pipeline 107 is discharged from the installation through the pipeline 109.

Make-up seawater in conduit 108 passes through deaerator 110. Exhaust air is returned via conduits 111, 112 and 113 to extractor 104, and then via conduit 103 to ejector / condenser 102.

The deaerated make-up seawater is drained from deaerator 110 through conduit 114 and pumped by pump 115 to conduit 116 and mixed in conduit 117 with recirculating brine flow from conduit 143. In this example, the combined feed and recycle flow flows through conduit 117 at a flow rate of 6194.4 kg / c at a temperature of 42.057 ° C and a salinity of 6.28%.

The combined make-up and recycle stream in conduit 117 is the feed stream.

The feed stream through conduit 117 is supplied as a refrigerant to condenser tubes 118 in the desalination zone 119. The desalination zone 119 is the last in a series of desalination zones. FIG. 3, the first desalination zone in the row is designated 120, the second desalination zone in the row is 121, and the dividing lines 122 indicate the presence of other similar desalination zones not actually shown in FIG. 3

The feed stream passing through the tubes 118 of the condenser is supplied to the tubes 123 of the condenser of the desalination zone 121, and then to the tubes 124 of the condenser of the desalination zone 120. The preheated feed stream passes through conduit 125 at a temperature of 102.829 ° C and is fed to the device 126 for heating the brine. The device 126 for heating the brine is installed on the pipeline 127, through which steam is supplied at a flow rate of 76.356 kg / s, a temperature of 130 ° C and a pressure of 2 bar. The heated feed stream is supplied from the device 126 to heat the brine through the pipeline 128 and through the flow regulator 129 at a temperature of 110 ° C and a pressure of 2 bar. The heated feed stream through line 128 is fed to the first desalination zone 120.

The first desalination zone 120 includes a lower zone 130 for receiving an instantly evaporating brine, a desiccant 131, through which the steam obtained by instantaneous evaporation of the brine passes before it is condensed on pipes 124 and will be collected in freshwater trays 132. Brine subjected to flash evaporation and the produced water are cascaded through desalination zones through parallel pipelines 133 and 134, respectively. After leaving the last desalination zone 119 brine is supplied via pipeline 135 to the level 105 of the heat removal. The resulting water is fed through pipelines 136 and 136a into the tray 137 for collecting the produced water of the heat removal stage 105.

Like the desalination zones, the heat removal stage 105 may include several successively located similar zones.

In the heat removal stage 105, seawater supplied through conduit 107 is used as a refrigerant, and the final product collected in tray 137 is supplied via conduit 138 to the storage tank. The brine remaining in step 105 of heat removal is discharged through conduit 139, and its part is recycled further by pump 140 via conduits 141 and 143 as a recycle stream and fed to conduit 117. The remaining portion is pumped through pump 140 via conduit 141 and conduit 142.

From the last desalination zone 119, the heat flow of the recirculating product is discharged in accordance with the present invention. A portion of the produced water from conduit 136 (flow rate 76 kg / s in this example) is diverted using recirculation pump 145 to conduit 144 and conduit 146 at a temperature of 48.20 ° C and salinity of 0%. The heat recycle stream that passes through conduit 146 is fed to heat exchanger tubes 147 and then through pipelines 148 and 149 to the freshwater tray of the desalination zone 121. The heated heat recycle stream is supplied under pressure using valve 150 to maintain pressure in this example. In another embodiment, shown by the dotted line in FIG. 3, the spillway device 151 may be used to maintain the pressure of the heated thermal recycle stream.

The heating stream is fed through pipelines 152 and 153 to heat exchanger 147 from the bottom of the device 126 for brine heating. In accordance with another embodiment, the heating stream from an external source (for example, a steam generator installation) may be supplied via conduit 154. Steam or hot water is discharged from the system via conduit 155.

In tab. 1 shows a number of parameters in accordance with this example 1 in each of the 20 steps of the method of steps in accordance with the method of the present invention. In this case, at least 20 steps include a device for heating the brine, 16 desalination zones and 3 stages of heat removal. Below are the measured parameters:

And - the temperature of the feed stream (in ° C) at the entrance to each stage;

B - temperature of the feed stream (in ° C) at the outlet of each stage;

C is the flow rate of the feed stream passing through each stage (kg / s);

Ό is the brine flow rate (kg / s) subjected to instantaneous evaporation withdrawn from each stage;

P - pressure (absolute value in bar) in each stage;

t is the productivity (kg / s) of each step in the production of fresh water;

M - total capacity (kg / s) after the release of the final product at each successive stage.

Table 1

Stage Temperature is roughly Brine temperature outlet cable cooling flow in a tubular loop Consumption of brine subjected to instantaneous evaporation from each stage Stage pressure Produce-telnost Aggregate BUT AT WITH ϋ R t M WITH WITH kg / s kg / s bar kg / s kg / s Us goi 102.83 110, 00 6194.4 6194, 4 1, 668 0 0 heating brine one 98.97 102.83 6194.4 6153.2 1,210 41.15 41.15 2 95.11 98.97 6194.4 6112.9 1,059 40.37 1 157.52 3 91.27 95.1 6194.4 6073.1 0.924 39.80 197.32 four 87.41 91.27 6194.4 6033.1 0, 802 39.97 237.29 five 83.56 87.41 6194.4 5993.7 0.659 39.38 276.67 6 79.72 83.56 6194.4 5954.9 0.601 38.83 315.49 7 75.90 79.72 6194.4 5916,8 0.519 38,10 353.60 eight 72.08 75.90 6194.4 5878.9 0.446 37.90 391.50 9 68.26 72.08 6194.4 5842.0 0.382 36.90 428.4 ten 64.49 68.26 6194.4 5806.1 0.328 35.91 464.31 eleven 60.61 64.49 6194.4 5769.4 0.278 36,69 501.00 12 56,72 60.61 6194.4 5733.1 0.235 36.32 537.32 13 52.94 56,72 6194.4 5698.4 0.198 34.70 572.02 14 49.32 52.94 6194.4 5665,5 0.168 32.87 604.89 15 45.60 49.32 6194.4 5630.3 0.140 35.19 640.08 sixteen 42.06 45.60 6194.4 5597.8 0,117 32.55 672.63 17 39, 94 42.68 6388.9 5571.5 0,102 26.25 622.88 18 37.38 39.94 6388.9 5547.3 0.089 24.23 647.11 nineteen 35.00 37.38 6388.9 5524.9 0.078 22.36 669.47

In general, in this example, the coefficient of performance (kilogram of the final product (fresh water) produced per kilogram of steam fed into the system) is 8.795. A process plant operating in accordance with this example is capable of producing 12.75 million British gallons of fresh water per day (approximately 60 million liters of water per day)

Example 2

As seen in FIG. 8, the flow of sea water is fed through the pipeline 100 'at a flow rate of 6638.9 kg / s and a temperature of 35 ° C. Salinity of sea water is 4.45%. A portion of the seawater supplied through conduit 100 'is supplied as refrigerant via conduit 101' to air ejector 102 '. An air ejector / condenser 102 ′ is installed on conduit 103 ′, while a mixture of water vapor and non-condensable gases (mainly air) is discharged by means of an extractor 104 ′ from a heat removal stage 105 ′. Non-condensable gases are fed to conduit 106a ', and any residual condensable materials are drained from the air ejector / condenser 102' to conduit 106 '. In this example, the flow rate of seawater in pipeline 101 'is 250 kg / s.

The remaining seawater from the pipeline 100 '(at a flow rate of 6388.9 kg / s) is fed through the pipeline 107' as a refrigerant to the heat removal stage 105 '. The cooling sea water in the pipeline 107 'is heated, passing through the heat removal stage 105', to a temperature of 42.68 ° C, and part of this water (at a flow rate of 1822 kg / s) is supplied to the pipeline 108 'as make-up water. The remaining sea water in the pipeline 107 'is discharged from the installation through the pipeline 109'.

Make-up seawater is supplied to conduit 108 'via deaerator 110'. Exhaust air is returned through pipelines 111 ', 112' and 113 'to extractor 104', and then via pipeline 103 'to air ejector / condenser 102'.

Deaerated make-up seawater is supplied from deaerator 110 'to conduit 114' and then pumped by pump 115 'to conduit 116' and mixed in conduit 117 'with a recirculating brine flow from conduit 143'. In this example, the flow rate of the combined make-up and recirculating flow in the pipeline 117 'is 6194.4 kg / s at a temperature of 42.057 ° C and a salinity of 6.28%.

The combined feed and recycle stream in conduit 117 'will now be denoted by the term “feed stream”.

The feed stream through conduit 117 'is supplied as a refrigerant to condenser tubes 118' in the desalination zone 119 '. Desalination zone 119 'is the last in a number of desalination zones. FIG. 8, the first desalination zone in the row is designated 120 ′, the second desalination zone in the row is 121 ′, and the dividing lines 122 ′ indicate the presence of other similar desalination zones not actually shown in FIG. eight.

The feed flow of raw materials passing through the tubes 118 'of the condenser is supplied to the tubes 123' of the condenser of the desalination zone 121 ', and then to the tubes 124' of the condenser of the desalination zone 120 '. The preheated feed stream passes through conduit 125 'at a temperature of 102.807 ° C and is fed to the device 126' to heat up the brine. The device 126 'for heating the brine is installed in the pipeline 127', through which steam is supplied at a flow rate of 76.597 kg / s, a temperature of 130 ° C and a pressure of 2 bar. The heated feed stream is supplied from the device 126 'for heating the brine through the pipeline 128' and through the flow regulator 129 'at a temperature of 110 ° C and a pressure of 2 bar. The heated feed stream through conduit 128 'is fed to the first desalination zone 120'.

The first desalination zone 120 ′ includes the lower zone 130 ′ for receiving an instantly evaporating brine, a desiccant 131 ′, through which the steam from the instant evaporation of the brine passes, before it is condensed on the pipes 124 ′ and will be collected in fresh trays 132 ′ water. Brine subjected to flash evaporation and the produced water are cascaded through desalination zones through parallel pipelines 133 'and 134', respectively. After exiting the last desalination zone 119 ′, brine is supplied via conduit 135 ′ to step 105 ′ of heat removal. The produced water is supplied via conduit 136 'to tray 137' to collect the produced water at heat removal stage 105 '.

In step 105 'of heat removal, seawater fed through conduit 107' is used as a refrigerant, and the final product collected in tray 137 'is supplied via conduit 138' to the storage tank. The brine remaining in stage 105 'of heat removal is discharged through conduit 139', and part of it is recycled further by means of pump 140 'through conduits 141' and 143 'as a recycle stream and fed to conduit 117'. The remainder is pumped by pump 140 ′ through conduit 141 ′ and conduit 142 ′.

From the last desalination zone 119 ′, the heat flow of the recirculating product is diverted in accordance with the present invention. Part of the brine in the desalination zone 119 '(in this example, the flow rate is 85.49 kg / s) is diverted to the pipeline 144' (shown by the dotted line in Fig. 8, since Fig. 8 also shows another variant of thermal recycling, which will be described in example 3) using a recirculation pump 145 'and in the pipeline 146' at a temperature of 49.89 ° C and a salinity of 6.94%. The thermal recycle stream supplied through conduit 146 ′ passes through conduit 146a ′ and is supplied to heat exchanger tubes 147 ′ and further via conduits 148 ′ and 149 ′ to the lower part of the desalination zone 121 ′. The heated thermal recycle stream is supplied under pressure through a valve 150 'to maintain pressure in this example.

The heating stream is fed through pipelines 152 'and 153' to heat exchanger 147 'from the bottom of the device 126' to heat up the brine. In accordance with another embodiment, a heating stream from an external source (for example, a steam generator installation) may be supplied via a conduit 154 '. Steam or hot water is discharged from the system through pipelines 154 'and 155'.

In tab. 2 shows a number of parameters in accordance with this example 2 in each of the 20 steps of the steps method in accordance with the method of the present invention. In this example, 20 steps include a device for heating the brine, 16 desalination zones and 3 stages of heat removal. Below are the measured parameters:

B - temperature of the feed stream (in ° C) at the outlet of each stage;

C is the flow rate of the feed stream passing through each stage (kg / s);

P - pressure (absolute value in bar) in each stage;

t is the productivity (kg / s) of each step in the production of fresh water,

table 2

Stage brine tour The temperature of the brine in the wire Coolant flow rate in a tubular loop subject to instantaneous evaporation Pressure Cinizoli- performance last word steps degrees BUT AT WITH ABOUT R t m WITH with kg / s kg / s bar kg / s kg / s Ustnagreva I 102.81 110.00 6194.4 6194.4 1,669 0 0 98.94 102.81 6194.4 6153.1 1,210 41.30 41.30 2 95.08 98.94 6194.4 6197.4 1,057 40.20 82.50 3 91.25 95.08 6194.4 6157.1 0.923 40.25 122.75 four 87.39 91.25 6194.4 6116.7 0.801 40.44 163.18 five 83.55 87.39 6194.4 6076.9 0.694 38.85 203.03 6 79.71 83.55 6194.4 6037.6 0.601 39.29 242.32 7 75.91 79.71 6194.4 5999.0 0.519 38.57 280,89 eight 72.08 75.91 6194.4 5960.6 0.446 38.37 319.26 9 68.27 72.08 6194.4 5923.3 0, 383 37.37 356.63 ten 64.50 68.27 6194.4 5886.9 0.328 36.35 392.98 eleven 60.63 64.50 6194.4 5849.8 0.278 37.15 430.13 12 56.73 60.63 6194.4 5812.9 0.235 36.81 466.94 13 52.96 56.73 6194.4 5777,6 0.196 35.16 502,10 14 49,34 52.96 6194.4 5744.5 0.168 32.28 535.39 15 45.61 49,34 6194.4 5708,8 0.140 35.65 571.04 sixteen 42.07 45.61 6194.4 5675,8 0.118 33.01 604.05 17 39.96 42.70 6389.9 5564.1 0,102 26.30 630.35 18 37.39 39.96 6388.9 5639.8 0.089 24.26 654.61 nineteen 35.00 37.39 6388.9 5517.4 0.078 22.39 677.00

In general, in this example, the coefficient of performance (kilogram of the final product (fresh water) produced per kilogram of steam fed into the system) is 8.865. A process plant operating in accordance with this example is capable of producing 12.90 million British gallons of fresh water per day (approximately 60 million liters of water per day).

Example 3

Example 3 is similar to example 2. However, in accordance with FIG. 8, the heat recycle stream from the desalination zone 119 'is not taken as part of the instantly evaporating brine in this zone, but as a feed stream (brine) in the condenser tubes 118'. The heat recycle stream is withdrawn in line 144 (shown by the dotted line in Fig. 8 to illustrate that it is an alternative option to take back the recycle product from the instantly evaporating brine in the water pipe 144 ', as described in Example 2). Then, the recycle stream is fed to conduit 146a ′ and further according to the scheme as described in Example 2.

In tab. 3 shows a number of parameters in accordance with this example 3 in each of the 20 stages in accordance with the method of the present invention. In this example, 20 steps include a device for heating the brine, 16 desalination zones and 3 stages of heat removal. Below are the measured parameters:

B - temperature of the feed stream (in ° C) at the outlet of each stage;

C is the flow rate of the feed stream passing through each stage (kg / s);

P - pressure (absolute value in bar) in each stage;

t is the productivity (kg / s) of each step in the production of fresh water;

Table 3

Consumption of passol, subject to instantaneous evaporation, discharged

- BUT AT WITH ABOUT R t kg / s _M _ kg / s WITH WITH kg / s kg / s bar Device 102.80 110.00 6121.45 6121.45 1.665 0 0 heating brine one 98.91 102.80 6121.45 6080.4 1,209 41.05 41.05 95.03 98.91 6121.45 6112,5 1,056 40.83 81.87 91.17 95.03 6121.45 6072.5 0,920 40.02 ^ 21.89 87.29 91.17 6121.45 6032.4 0.798 40.15 162.04 83.43 87.29 6121.45 5992,8 0,691 39.53 201.57 6 79.58 83.43 6121.45 5953.9 0.598 38.94 240.51 7 75.77 79.58 6121.45 5915.7 0.515 38.18 278.69 eight 71.94 75.77 6121.45 5877.8 0.445 37.95 316.64 9 68.12 71.94 6121.45 5840.8 0.380 36.92 353.56 ten 64.35 68.12 6121.45 5804.9 0.325 35.89 389.45 eleven 60.48 64.35 6121.45 5768.3 0.276 36.62 426.07 '2 56.60 60.48 6121.45 5733.1 0.233 36.28 462.35 ^ 13 52.84 56.60 6121.45 5697.4 0.197 34.62 496.97 14 49.23 52.84 6121.45 5664.7 0.167 32.75 529.72 15 145.52 49.23 6121.45 5629,6 0.139 35.05 564.77 sixteen 42.00 45.52 6121.45 5597.2 0,117 32.43 597.20 1 7 39.90 42.61 6388.9 5571.2 0.101 26.03 623.23 18 37.37 39.90 6388.9 5547.1 0.088 24.03 647.26 ΐ ^one '! 35.00 37.37 6388.9 5524.9 0.078 22.19 669.45

In general, in this example, the coefficient of performance (kilogram of the final product (fresh water) produced per kilogram of steam fed into the system) is 8.868. A process plant operating in accordance with this example is capable of producing 12.75 million British gallons of fresh water per day (approximately 60 million liters of water per day).

Claims

CLAIM

1. The method of desalination of salt water, comprising the following steps:

a) providing a means for heating the brine;

b) providing at least one desalination zone comprising a condenser and means for collecting condensate from the condenser;

c) provision of a heat exchanger;

e) supplying a preheated feed stream to a brine heating device;

) supplying the first heating stream containing steam to a device for heating the brine for further heating the preheated feed stream;

d) selective use of at least part of the first heating stream from the brine heating device;

.)) feeding a portion of the product stream to the heat exchanger as a heat recycle stream;

k) feeding a second heating stream, optionally comprising at least a portion of the selected first heating stream, to a heat exchanger to heat the heat recycle stream; and

l) feeding the heated thermal recycle stream to at least one desalination zone.

2. The method of desalination of salt water, comprising the following steps:

a) providing a means for heating the brine;

c) provision of a heat exchanger;

) supplying a feed stream consisting of salt water as a coolant to a condenser for preheating the stream;

e) supplying a preheated feed stream to a brine heating device;

d) selective selection of at least part of the first heating stream from the device for heating the brine;

1) supplying the heated feed stream from the brine heating device to at least one desalination zone, evaporating at least a portion of the heated feed stream in the desalination zone in order to produce steam consisting of water vapor, and condensing the steam on the condenser in the desalination zone;

) withdrawing from the desalination zone a stream of product containing condensate and a waste feed stream containing salt water;

_)) feeding part of the spent feed stream to the heat exchanger as the heat flow of the recirculating product;

l) feeding the heated thermal recycle stream to at least one desalination zone.

3. The method of desalination of salt water, comprising the following steps:

a) providing a means for heating the brine;

c) provision of a heat exchanger;

b) supplying a feed stream consisting of salt water as a coolant to a condenser for preheating the feed stream;

d) the supply of the first heating stream containing steam, in a device for heating the brine for further heating the pre-heated feed stream;

11) selectively selecting at least a portion of the first heating stream from the brine heating device;

_)) supplying the heated feed stream from the brine heating device and the heated heat recycle stream from the heat exchanger to at least one desalination zone, evaporating at least part of the heated feed stream and the heated heat recycle stream in the desalination zone in order to produce steam including water steam, and steam condensation in the desalination zone;

K) selection from the desalination zone of the product stream, including condensate, and the waste feed stream, including salt water.

4. The method according to claim 1, characterized in that the heat recycle stream is fed to a device for collecting condensate from the desalination zone.

5. The method according to claim 4, characterized in that the ratio of heat recycle stream to condensate in the desalination device collection device is from about 0.85: 1 to about 1.15: 1.

6. A method according to any one of claims. 1-5, characterized in that there are several series-connected desalination zones.

7. The method according to claim 6, characterized in that the heat recirculating stream is discharged from the first desalination zone, and the heated heat recirculation stream is fed to the second desalination zone.

8. The method according to claim 7, characterized in that the second desalination zone is located closer in a number of desalination zones to the device for heating the brine than the first desalination zone.

9. The method according to claim 8, characterized in that a lower pressure is maintained in the first desalination zone compared with the second desalination zone.

10. The method according to any one of claims 1 to 9, characterized in that the heat recycle stream is fed to the heat exchanger under pressure exceeding the pressure of the second heating stream supplied to the heat exchanger.

11. The method according to any one of claims 1 to 10, characterized in that the feed stream is supplied to the device for heating the brine under pressure exceeding the pressure of the first heating stream supplied to the device for heating the brine.

12. The method according to any one of claims 1 to 11, characterized in that the temperature of the heat recycle stream does not exceed by more than 5 ° C the water saturation temperature in at least one desalination zone.

13. The method according to any one of claims 1 to 12, including the selection of at least part of the first heating stream from the device for heating the brine.

14. The method according to p. 13, characterized in that the second heating stream contains at least part of the selected first heating stream.

15. The method according to any one of claims 1 to 14, characterized in that there are many heat exchangers for heating the thermal recycle stream.

16. Installation for desalination of salt water, comprising means for controlling the method according to any one of claims 1 to 15.