Method for reducing content of organic carbon in saline water

Abstract

The invention discloses a process device and method for reducing the content of organic carbon in saline water, and belongs to the technical field of TOC control in the ionic membrane alkali production industry, the method is applied to reducing the content of organic carbon in saline water, continuous and stable operation is performed for 3 months, and the content of organic carbon in saline water is reduced by treating the organic carbon in the saline water. The content of organic carbon in the saline water is reduced from about 50ppm to below 10ppm, the TOC of the saline water is always qualified, the voltage of the electrolytic cell is not obviously increased, and the reduction amplitude of the current efficiency is obviously slowed down. The addition amount of non-dechlorinated light salt brine is obviously reduced, free chlorine residues in the brine are reduced, the addition amount of sulfite is synchronously reduced, and the production cost is obviously reduced. Meanwhile, the operation is simple, only a small amount of steam is added for use, and due to the fact that the adding amount of the non-dechlorinated light salt brine is reduced on site, emitted chlorine is reduced, and the environment is obviously improved. According to the implementation of the method, great production benefits are created, the production cost of ionic membrane alkali production is reduced in a disguised manner, the production level is improved, and the product competitiveness of companies is enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of TOC control in ion membrane alkali production industry, and specifically relates to a process device and method for reducing the organic carbon content in brine. Background Art

[0002] TOC is a general term for organic carbon. The control index of TOC in brine in the ion membrane alkali production process is required to be less than 10ppm. Too high a content of organic pollutants in the brine feed will have an adverse effect on the performance of the ion membrane and the electrolyzer. The main effects are: TOC reduces the effective area of ​​the membrane and the cell voltage increases; TOC causes the ion membrane to swell and intermittently dehydrate, while reducing the ability to block anions and reducing the current efficiency of the membrane. Long-term dehydration of the membrane will also cause a permanent decrease in the current efficiency; TOC causes the chlorine-hydrogen pressure in the electrolyzer to fluctuate, and for a long time, it will form pinholes in the membrane and reduce the product quality; TOC will destroy the ion membrane structure, causing irreversible damage to the ion membrane and shortening the service life of the membrane; TOC covers the anode coating impermeably, reducing the active area of ​​the anode, increasing the cell voltage and worsening the current distribution; it can also cover the anode coating permeably, limiting the chloride ions from approaching the anode, increasing the production of oxygen, causing the anode coating to fail prematurely and shortening the service life of the anode; TOC reactants (chlorocarbon compounds) in the electrolyzer will cover the electrode surface, causing the decomposition voltage to increase and the power consumption to increase; TOC will reduce the purity of chlorine and the current efficiency.

[0003] At present, in the process of ion membrane alkali salt water treatment, chlorine-containing light salt water is added to decompose organic carbon. When the quality of raw salt is poor and the TOC content is seriously exceeded, simply adding chlorine-containing salt water cannot effectively remove the high content of organic carbon. In current production, the TOC content in the purchased raw salt is as high as 200ppm, and the TOC of the salt water entering the tank is about 50ppm. The serious TOC exceeds the standard, resulting in an increase in the cell voltage, a rapid decrease in current efficiency, severe bubbling at the cathode outlet, and damage to the cathode coating. Therefore, in order to effectively reduce the TOC of the brine, protect the electrolytic cell from damage, reduce the cell voltage, improve the current efficiency, and achieve comprehensive technological progress in effective production and product quality assurance, it is necessary to provide a new process device and method for reducing the organic carbon content in brine, so research on this is imminent. Summary of the invention

[0004] The purpose of the present invention is to provide a process device and method for reducing the organic carbon content in brine in view of the existing problems.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for reducing the organic carbon content in salt water comprises the following steps:

[0007] S1, transport the brine to the brine heat exchanger through the brine pump, heat it to 90°C and then send it to the brine tank;

[0008] S2, add industrial salt to the salt tank to dissolve, the dissolved brine enters the baffle tank, and the undechlorinated brine flows from the high-level tank into the baffle tank by gravity, and the flow is adjusted by the regulating valve;

[0009] The mixed brine enters the reaction tank for reaction;

[0010] S3. A compressed air distribution pipeline is provided at the bottom of the reaction tank, and compressed air is bubbled to fully mix and react the free chlorine and organic carbon;

[0011] S4. The reacted brine is pumped into a brine cooler through a membrane filtration feed pump, and circulating water is introduced to cool the brine. After the brine is cooled to 60° C., it is sent to an inorganic membrane filter for filtration.

[0012] Preferably, the brine heat exchanger described in step S1 is heated by steam.

[0013] Preferably, the outlet pipe of the salt water pump enters the salt water heat exchanger, the outlet of the salt water heat exchanger enters the salt pool, the salt pool flows into the reaction pool through the baffle groove, and the undechlorinated brine is connected to the baffle groove through a pipe.

[0014] Preferably, a compressed air distribution pipe is inserted into the reaction pool, the reaction pool flows into the middle pool, the membrane filtration feed pump inlet is inserted into the middle pool, the membrane filtration feed pump outlet is connected to the brine cooler via a pipe, and the brine cooler outlet is connected to the inorganic membrane filter.

[0015] Preferably, the brine heat exchanger and brine cooler are both provided with steam or circulating water temperature control regulating valves.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. In the process of heating the brine, the steam valve opening is increased to increase the temperature of the brine. After the temperature of the brine is increased, in the reaction tank, high temperature is more conducive to the reaction of free chlorine and organic carbon, accelerates the decomposition of organic carbon, and can make free chlorine fully react, reduce the subsequent sulfite consumption, and prevent free chlorine from being brought to the resin tower to damage the resin; air is bubbling into the reaction tank, on the one hand, free chlorine and organic carbon are fully mixed, on the other hand, the oxygen content is increased, so that organic matter is more easily decomposed, and air bubbling can take away organic carbon decomposition products, accelerating the decomposition of organic carbon. A brine cooler is added at the outlet of the membrane feed pump, and circulating water is used to cool the brine so that its temperature reaches a suitable tank inlet temperature.

[0018] 2. The system structure of the present invention is simple, the cost investment is small, and automatic control and continuous production can be realized;

[0019] 3. The existing process adds a large amount of undechlorinated light brine, and the residual free chlorine content in the brine is high. A large amount of sulfite needs to be added later to neutralize the free chlorine. The present invention increases the temperature of the brine and blows air into it to increase the decomposition rate of inorganic carbon, effectively reducing the TOC content in the brine. The amount of undechlorinated light brine added is reduced, and the amount of sulfite added is reduced, which saves production costs and improves the safety and stability of electrolytic production.

[0020] 4. The present invention does not discharge waste water or waste residue, produces a small amount of carbon dioxide, and the discharge of the three wastes meets environmental protection requirements; it not only improves economic benefits, but also improves environmental benefits.

[0021] 5. The method of the present invention is applied to reduce the organic carbon content in brine, and the process is continuously and stably operated for 3 months. By treating the organic carbon in the brine, the organic carbon content in the brine is reduced from about 50ppm to below 10ppm, the brine TOC is always qualified, the electrolytic cell voltage does not rise significantly, and the current efficiency decreases significantly. The amount of undechlorinated light brine added is significantly reduced, the residual free chlorine in the brine is reduced, the amount of sulfite added is reduced synchronously, and the production cost is significantly reduced. At the same time, the operation is simple, and only a small amount of steam is added. Due to the reduction in the amount of undechlorinated light brine added on site, the chlorine gas emitted is reduced, and the environment is significantly improved. The implementation of this invention has created great production benefits, reduced the production cost of ion membrane alkali in disguised form, improved the production level, and enhanced the company's product competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a process flow chart for reducing the organic carbon content in brine. DETAILED DESCRIPTION

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Example 1

[0025] like Figure 1 The method for reducing the organic carbon content in salt water of the present invention comprises the following steps:

[0026] S1, transport the brine to the brine heat exchanger through the brine pump, heat it to 90°C and then send it to the brine tank;

[0027] S2, add industrial salt to the salt tank to dissolve, the dissolved brine enters the baffle tank, and the undechlorinated brine flows from the high-level tank into the baffle tank by gravity, and the flow is adjusted by the regulating valve;

[0028] The mixed brine enters the reaction tank for reaction;

[0029] S3. A compressed air distribution pipeline is provided at the bottom of the reaction tank, and compressed air is bubbled to fully mix and react the free chlorine and organic carbon;

[0030] S4. The reacted brine is pumped into a brine cooler through a membrane filtration feed pump, and circulating water is introduced to cool the brine. After the brine is cooled to 60° C., it is sent to an inorganic membrane filter for filtration.

[0031] The brine heat exchanger is heated by steam.

[0032] The outlet pipeline of the salt water pump enters the salt water heat exchanger, the outlet of the salt water heat exchanger enters the salt pool, the salt pool flows into the reaction pool through the baffle groove, and the undechlorinated brine is connected to the baffle groove through the pipeline.

[0033] A compressed air distribution pipeline is inserted into the reaction pool, the reaction pool flows into the middle pool, the membrane filtration feed pump inlet is inserted into the middle pool, the membrane filtration feed pump outlet is connected to the brine cooler through a pipeline, and the brine cooler outlet is connected to the inorganic membrane filter.

[0034] The brine heat exchanger and brine cooler are both provided with steam or circulating water temperature control regulating valves.

[0035] It also includes pressure gauges, thermometers, regulating valves, liquid level gauges, as well as steam and circulating water lines.

[0036] The salt water pump, salt water heat exchanger, salt water tank, brine tank, high-level tank, reaction tank, intermediate tank, membrane filtration feed pump, brine cooler, and inorganic membrane filter described above all adopt devices in the art or existing devices, or devices that can achieve corresponding functions.

[0037] According to the above treatment method, the organic carbon content in the brine is reduced, and the process is continuously and stably operated for 3 months. By treating the organic carbon in the brine, the organic carbon content in the brine is reduced from about 50ppm to below 10ppm, the brine TOC is always qualified, the electrolytic cell voltage does not rise significantly, and the current efficiency decreases significantly. The amount of undechlorinated light brine added is significantly reduced, the residual free chlorine in the brine is reduced, the amount of sulfite added is reduced synchronously, and the production cost is significantly reduced. At the same time, the operation is simple, and only a small amount of steam is added. Due to the reduction in the amount of undechlorinated light brine added on site, the chlorine gas emitted is reduced, and the environment is significantly improved. The implementation of this invention has created great production benefits, reduced the production cost of ion membrane alkali in disguised form, improved the production level, and enhanced the company's product competitiveness.

[0038] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for reducing the organic carbon content in brine, characterized in that: The steps include: S1, transport the brine to the brine heat exchanger through the brine pump, heat it to 90°C and then send it to the brine tank; S2, add industrial salt to the salt tank to dissolve, the dissolved brine enters the baffle tank, and the undechlorinated brine flows from the high-level tank into the baffle tank by gravity, and the flow is adjusted by the regulating valve; The mixed brine enters the reaction tank for reaction; S3. A compressed air distribution pipeline is provided at the bottom of the reaction tank, and compressed air is bubbled to fully mix and react the free chlorine and organic carbon; S4. The reacted brine is pumped into a brine cooler through a membrane filtration feed pump, and circulating water is introduced to cool the brine. After the brine is cooled to 60° C., it is sent to an inorganic membrane filter for filtration.

2. A method for reducing the organic carbon content in brine according to claim 1, characterized in that: The brine heat exchanger described in step S1 is heated by steam.

3. A method for reducing the organic carbon content in brine according to claim 2, characterized in that: The outlet pipeline of the salt water pump enters the salt water heat exchanger, the outlet of the salt water heat exchanger enters the salt pool, the salt pool flows into the reaction pool through the baffle groove, and the undechlorinated brine is connected to the baffle groove through the pipeline.

4. A method for reducing the organic carbon content in brine according to claim 3, characterized in that: A compressed air distribution pipeline is inserted into the reaction pool, the reaction pool flows into the middle pool, the membrane filtration feed pump inlet is inserted into the middle pool, the membrane filtration feed pump outlet is connected to the brine cooler through a pipeline, and the brine cooler outlet is connected to the inorganic membrane filter.

5. A method for reducing the organic carbon content in brine according to claim 4, characterized in that: The brine heat exchanger and brine cooler are both provided with steam or circulating water temperature control regulating valves.

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