WO2008138175A1

WO2008138175A1 - A method of high hardness and high salinity concentrated seawater as industrial circulating cooling water

Info

Publication number: WO2008138175A1
Application number: PCT/CN2007/001699
Authority: WO
Inventors: Dezhi Shao; Yanxin Wang; Jianguo Bao; Wanli Hu; Xuelv Zheng; Yingying Zhang; Shucheng Mi
Original assignee: China University Of Geosciences (Wuhan City)
Priority date: 2007-05-09
Filing date: 2007-05-25
Publication date: 2008-11-20
Also published as: CN101049985A; CN100560509C

Abstract

A method of using high hardness and high salinity concentrated seawater as industrial circulating cooling water comprises the following steps: (a) passivating pretreatment of system; (b) collecting water to removal suspended material; (c) catalytic ozonizing the water from step (b) with nanosize TiO2 /AC; (d) introducing the water from step (c) into a filter; (e) introducing the water from the preceding steps into a heat exchange system. The water from the heat exchange system will be introduced into a cooling tower and then comes back to a reservoir under the cooling tower to be a supplement to the water reduced due to evaporation.

Description

Method for concentrating seawater with high hardness and high salinity for industrial circulating cooling water

The invention provides a method for utilizing high hardness and high salinity concentrated seawater as industrial circulating cooling water, which is an ozone corrosion instead of adding a corrosion inhibitor, a scale inhibitor and a bactericidal algicide to solve the corrosion protection and knot of the system. Water-saving and environmental protection technology for scale, sterilization and algae killing. Background technique

A large number of high-salinity and high-hardness concentrated seawater produced by the use of desalination technology, there are many ways to use this part of resources: such as salt production, chlor-alkali chemical raw materials, extraction of economically valuable elements, such as potassium extraction of bromine, magnesium, Boron, uranium, gold or emissions, etc. However, in view of the concentrated water concentration of desalinated seawater currently used on a large scale, these methods are not an economically reasonable treatment method. Because the output of China's salt industry is supersaturated; the various chemicals added to the water during desalination are difficult to remove, and many of them have certain toxic effects; and the terrestrial minerals of magnesium and calcium in China are quite abundant; for a small amount of elements, In addition to the industrialization of potassium, bromine and iodine, the extraction of other trace elements does not have the value of economic extraction. Industrial cooling water accounts for about 70% of the total industrial water consumption. If high-salinity and high-hardness concentrated seawater is used as industrial circulating cooling water, due to high salinity and high hardness, there is a great problem of corrosiveness to various metals. There are still technical issues to be resolved. The seawater has high salt content and complex composition. The conductivity of seawater is only two orders of magnitude higher than that of ordinary fresh water. This determines that the resistive retardation of seawater is much smaller than that of freshwater, and seawater is more corrosive than freshwater. And the proportion of chloride in the salt content of seawater is very large, and the chlorine content of seawater is as high as 19%, so most metals such as iron, steel, cast iron, etc. cannot be in seawater. T/CN2007/001699 establishes a passive state. At the same time, there are many kinds of microorganisms and large organisms in seawater, and the content is high, which is prone to biofouling, which leads to the corrosion of microbes or the corrosion of scales. In addition, the concentration of scale ions such as Ca ²⁺ and Mg ^{2+ in} seawater is much higher than that of ordinary fresh water, and the concentration tends to increase with the concentration factor. The ordinary scale inhibitor and dispersant cannot effectively control the deposition of chemical scale. The use of concentrated seawater as circulating cooling water has more serious problems of corrosion, scaling and fouling. Seawater circulating cooling water treatment is more difficult than freshwater circulation; concentrated seawater for circulating cooling water treatment is more difficult than seawater circulation cooling.

Summary of the invention

In order to solve the problems in the above technology, the object of the present invention is to provide a method for using industrial water circulating cooling water with high hardness and high salinity to achieve high hardness and high salinity seawater, high hardness and high salinity. The wastewater is treated with three additives such as corrosion inhibitor, scale inhibitor and bactericidal algicide to save water and protect the environment.

In order to achieve the above object, the technical solution of the present invention is to provide a method for utilizing high hardness and high salinity concentrated seawater for industrial circulating cooling water, the method comprising the following steps: equipment for corrosion and scaling in a cooling system Washed with a cleaning agent and passivated with a passivating agent;

b. Collecting water and sinking

High hardness and high salinity seawater (Pomeranian has reached about 10, hardness is

20000-70000mg/L) Remove suspended matter and collect it in the reservoir under the cooling tower;

c active treatment 01699 The storage tank under the cooling tower is equipped with a layer of activated carbon loaded with nanometer Ti0 ₂ with a thickness of 600mm. It is equipped with an ozone aeration system or a mixed jet system to catalyze the oxidation of ozone to make C0D 60mg/L in water. ; 0 ₃ 0. 05-0. 20 mg/L; D0^2. 0 mg/L; d.

The water in the step c is filtered into the filter, and the concentration of the ozone in the filtered water is maintained at 0. 05-0. 2mg / L, when less than 0. 05mg / L additional ozone; e. heat Exchange

The treated water enters the heat exchange system, and the water from the heat exchange system enters the cooling tower for cooling and returns to the reservoir below the cooling tower. In the cooling process of the cooling tower, the above water needs to supplement the water evaporated in the cooling process, and the added amount is balanced with the evaporation amount. The effect of the invention is that the treatment method is used without rust inhibitor, corrosion inhibitor and bactericidal algaecide, and the total hardness of the treated water is as high as 4000-40000 mg/L, and the chloride is as high as

30000-120000mg / L, the corrosion rate of carbon steel, copper alloy, stainless steel equipment is: 0. 13 gall / a, 0. 03mm / a _o This method is applicable to all industries industrial circulating cooling water process, It is equivalent to saving about 50% of fresh water for the entire city. Other technologies that contain high salinity and high hardness industrial wastewater can also be used as industrial circulating cooling water. Therefore, zero discharge and zero drainage can be achieved. Realize water conservation and protect the environment. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process flow diagram of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention utilizes high hardness and high salinity concentrated seawater working with the present invention in conjunction with the accompanying drawings and embodiments. The method of circulating cooling water is explained. The reaction mechanism of the method for using the high hardness and high salinity concentrated seawater as the industrial circulating cooling water according to the invention is generally considered according to the role of ozone in the industrial circulating water of fresh water:

1. Ozone is a kind of oxidizing agent with strong oxidizing ability. It can directly oxidize unsaturated fatty acids, enzymes and proteins that make up cells, and oxidize macromolecular organic substances into small inorganic molecules, thus playing a good role in bactericidal and algae-killing;

2, mainly due to ozone can oxidize the organic matter in the scale layer matrix, so that the structure of the dirt becomes loose, easy to peel off from the pipe wall and fall off, thereby playing a role of scale inhibition;

3. Ozone can form a layer of Y-Fe ₂ 0 ₃ oxide film on the metal surface, which increases the corrosion resistance of the metal and reduces the corrosion rate.

4, the application of nano-scale Ti0 ₂ activated carbon is to reduce the energy consumption of ozone, in order to better play the role of sterilization and algae reduction and reduce COD. As shown in FIG. 1, the method for treating industrial circulating cooling water using high hardness and high salinity concentrated seawater comprises the following steps:

Passivation pretreatment

The equipment and pipelines that have been corroded and scaled in the cooling system are cleaned with a cleaning agent, and passivated with tap water containing a passivating agent for 24 hours to passivate. The passivating agent used is a commercially available prepreg agent such as a tungsten type, a phosphorus type or a molybdenum type.

b. Collecting water and sinking T/CN2007/001699 will be concentrated seawater after seawater desalination or other concentrated high salinity high hardness brackish water, industrial wastewater (Pomeranian has reached about 10, hardness is 20000-70000mg / L, its hardness to include Calcium carbonate meter 100-250mg/L) The suspended matter is removed and collected in a reservoir under the cooling tower. In the process of removing suspended solids, microfiltration equipment such as ceramic stainless steel, fiber bundle or membrane filtration is used. The high-hardness and high-salinity seawater described in this step includes high-hardness and high-salt concentrated seawater and high-hardness and high-salt industrial wastewater after desalination.

c. Active treatment

The storage tank under the cooling tower is filled with a nanometer-sized Ti0 ₂ activated carbon with a thickness of about 600 mm, and is equipped with an ozone aeration system for catalytic ozonation to make C0D 60rag/L in water; 0 ₃ 0. 05-0. 20 rag/L; D0^2. 0 mg/l, the nano-sized Ti0 ₂ activated carbon in this step accelerates ozone and photocatalytic oxidation, sterilizes algae, decomposes aquatic organisms and other organic substances, which is beneficial to increase ozone oxidation. Ability, energy saving.

d. Filter

The water treated in step c is filtered into the filter, and the fiber bundle filter is used to backflush every 8 hours, and the recoil is simultaneously compressed air, and the recoil time is about ten minutes. At the same time, the concentration of ozone in the filtered water is maintained at 0. 05-0. 2rag / L, when less than 0. 05mg / L, add ozone to 0. 05-0, 2mg / L.

e. heat exchange, the treated water enters the heat exchange system, the water from the heat exchange system is then cooled into the cooling tower and returned to the reservoir under the cooling tower. During the cooling of the cooling tower, there will be A part of the water is evaporated, and the treated domestic water (middle water) can be replenished into the volatilized portion, and the added amount is balanced with the evaporation amount. Example:

1. In the workshop of Tianjin Yihua Chemical Plant, firstly, the equipment and pipeline of the heat exchange system (all materials are carbonaceous) are circulated for 24 hours with tap water containing sodium molybdate (about 20mg/L) passivation agent. Passivation

2. The salt content of industrial wastewater in a plant is as high as 10-20Be ', and the content of main components is as follows: Collected in the reservoir under the cooling tower;

3. A storage tank containing nano-scale Ti0 ₂ (thickness about 600mm) is installed in the reservoir under the cooling tower, and an ozone aeration system is installed; catalytic ozone oxidation reaction is carried out to make C0D 60mg/L in water; 0 ₃ 0. 05-0. 20mg/L _; D0 2. 0mg/L.

4. The water treated in step 3 is filtered into a fiber bundle filter;

5至 0. 2mg / L; 5, the concentration of the ozone in the water was monitored at 0. 05- 0. 2mg / L;

6. Enter the heat exchange system;

7. The water from the heat exchange system is cooled by the cooling tower and returned to the reservoir below the cooling tower.

8. The treated water will volatilize part of the cooling tower during the cooling process, adding “middle water after domestic sewage treatment”, the amount of addition is controlled by the water level of the reservoir; Water" (usually fresh water) sprayed from the top of the cooling tower;

9. Cycle through steps 2-8;

10. The fiber bundle filter used in the filtration is backflushed once every 8 hours, and the recoil is simultaneously compressed air, and the recoil time is about ten minutes;

11. The recoil water enters the sludge concentration tank of the domestic sewage treatment facility and is treated regularly;

12, passivation cycle depending on the concentration of ferrous ions in the water (generally stable at 0. 03mg / L) is higher than 0. 04mg / L when the operation is stopped, the domestic water used (middle water) is added to the volatilized part, rinse The hot swap system can be restarted.

Claims

Claim

1. A method for cooling ice by industrial circulation using high hardness and high salinity concentrated seawater, the method comprising the following steps.

Passivation pretreatment

The equipment that has been corroded and fouled in the cooling system is washed with a cleaning agent and is passivated with a passivating agent;

b. Collecting water and sinking

c. Active treatment

The storage tank under the cooling tower is equipped with a layer of activated carbon loaded with nanometer Ti02 with a thickness of 600mm, and is equipped with an ozone aeration system or a mixed jet system for catalytic ozonation to make COD 60mg/L in water; 0 ₃ 0. 05 0. 20 mg / L; D0 ^ 2. 0 mg / L; d. Filtration.

The temperature of the water in the filtered water is adjusted to 0. 05- 0. 2m _g /L, when less than 0. 05mg / L, add ozone; e Heat exchange

The treated water enters the heat exchange system, and the water from the heat exchange system enters the cooling tower for cooling and returns to the reservoir below the cooling tower. In the cooling process of the cooling tower, the above water needs to supplement the water evaporated in the cooling process, and the added amount is balanced with the evaporation amount.

The processing method according to claim 1, wherein the passivating agent is a commercially available phosphorus-based, molybdenum-based or tungsten-based inorganic type pre-forming agent.

The processing method according to claim 1, wherein in the step b, the high-hardness and high-salinity seawater comprises a desalted high-hardness and high-salt-concentrated seawater and a high-hardness and high-salt industrial wastewater.