A treatment method for improving ion exchange membrane method chlorate decomposition capacity

Abstract

The application discloses a treatment method for improving ion membrane method chlorate decomposition capacity. Chlorine-containing dilute brine, which is exchanged by a chlorate heat exchanger, is mixed with hydrochloric acid in a static mixer, and then is introduced into a chlorate decomposition tank for decomposition. The dilute brine after decomposition in the chlorate decomposition tank is pumped into a dechlorination tower by a chlorate pump. Chlorine gas generated after the decomposition of the chlorine-containing dilute brine in the chlorate decomposition tank is removed through a gas phase pipeline to a chlorine gas main pipe. In abnormal conditions, a chlorine gas removal system is used. Through process control parameter optimization adjustment of the chlorate decomposition device, adjustment of the acid adding process and operation, the chlorate content at the outlet of the chlorate decomposition tank can be reduced to below 2g / L, the decomposition rate is increased to above 90%, and the dilute brine treatment capacity is increased to 8-10m 3 / h.

Description

Technical Field

[0001] This invention relates to the chlorate production process in the industrial ion-exchange membrane caustic soda production, and in particular to a treatment method for improving the decomposition capacity of chlorate. Background Technology

[0002] In the ion-exchange membrane process for caustic soda production, the brine system operates in a recycling mode. After the electrolyzer has been running for a period of time, the chlorate content in the brine system gradually increases. To ensure that the chlorate content of the incoming brine meets process requirements and to reduce the chlorate content in the alkali, some of the chlorate in the brine system must be decomposed to maintain the chlorate content at a certain level, thereby ensuring the performance of the ion-exchange membrane and maintaining high current efficiency. In the anode system of the electrolyzer, while chlorine gas reacts with sodium ions to produce chlorate, chloride ions also migrate from the anode chamber to the cathode chamber and react with sodium hydroxide to produce chlorate, causing the chlorate content in the liquid alkali to rise.

[0003] The current problem is:

[0004] 1. The decomposition rate of the chlorate decomposition tank is <80%.

[0005] 2. The average outlet flow rate of chlorate was 5.127 m³. 3 The flow rate fluctuates significantly. According to chlor-alkali industry standards, the amount of chlorate decomposition should generally be about 1 / 20 to 1 / 10 of the total brine flow rate to meet chlorate decomposition requirements. Currently, the total brine flow rate is approximately 140-160 m³ / h. 3 / h, the chlorate decomposition rate should be 7-16m³. 3 / h, the chlorate decomposition rate did not meet the requirements.

[0006] 3. The brine treated by the chlorate decomposition unit enters the dechlorination system, which serves to add acid before dechlorination. Increasing the amount of brine in the chlorate decomposition unit will lower the pH before dechlorination and increase material consumption. Summary of the Invention

[0007] The purpose of this invention is to provide a treatment method that, without disrupting the original recycling model, reduces the amount of hydrochloric acid used, increases the processing capacity of the chlorate decomposition device, stabilizes the chlorate content in the brine system and liquid alkali, and improves product quality, thereby enhancing the chlorate decomposition capacity of the ion-exchange membrane method.

[0008] To achieve the above objectives, this invention proposes a treatment method for improving the chlorate decomposition capacity of ion-exchange membrane methods. The method aims to overcome the shortcomings of existing technologies and achieve improved chlorate decomposition capacity, comprising the following steps:

[0009] Step 1: The chlorinated brine that has been heated by the chlorate heat exchanger is mixed with the hydrochloric acid solution in a static mixer and then fed into the chlorate decomposition tank for decomposition.

[0010] Step 2: The brine produced after decomposition in the chlorate decomposition tank is pumped into the dechlorination tower via a chlorate pump;

[0011] Step 3: The chlorine gas produced after the chlorine-containing brine is decomposed in the chlorate decomposition tank is sent to the chlorine main pipeline via the gas phase pipeline.

[0012] Furthermore, in step 1, the chlorinated brine is passed through a chlorate heat exchanger to raise the temperature to 95-98°C, and then mixed thoroughly with a 31wt% hydrochloric acid solution in a static mixer before entering the chlorate decomposition tank.

[0013] Furthermore, a temperature sensor is installed on the outlet pipeline of the static mixer in step 1.

[0014] Furthermore, a temperature sensor is installed on the chlorate decomposition tank in step 1.

[0015] Furthermore, in step 1, the liquid level in the chlorate decomposition tank is controlled at 1.9–2.0 m.

[0016] Furthermore, in step 2, the acidity of the dilute brine solution at the outlet of the chlorate decomposition tank is 0.30-0.40 mol / L.

[0017] Furthermore, in step 2, the chlorate decomposition tank outlet contains dilute brine (ClO). 3- The content should be controlled at ≤2.0mg / L.

[0018] The beneficial effects of this invention are as follows: This invention provides a treatment method for improving the decomposition capacity of chlorate via ion-exchange membrane technology. The process and operation are simple, and it has the following advantages compared to traditional processes:

[0019] The chlorate decomposition capacity ranges from 2.5 to 6.0 m. 3 / h increased to 8.0~10.0m 3 / h, the chlorate decomposition rate is increased from ≤80% to ≥90%, and the chlorate content in the treated brine is <2.0g / L. Ultimately, this significantly reduces the maintenance and replacement costs of the equipment and pipelines in the alkali evaporation system, while also reducing the occurrence of electrolytic side reactions and improving the current efficiency of the electrolytic cell. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the process and production equipment used in the method for improving the decomposition capacity of chlorate using the ion-exchange membrane method according to the present invention.

[0021] Appendix Figure 2 This is a graph showing the inlet flow rate data of the chlorate decomposition tank during the statistical period.

[0022] Appendix Figure 3Chlorate exports during the statistical period (ClO) 3- Content data chart.

[0023] Appendix Figure 4 This is a graph showing chlorate acidity data during the statistical period.

[0024] Figure 1 In the diagram: 1 is the hydrochloric acid control valve; 2 is the steam control valve; 3 is the chlorate heat exchanger; 4 is the static mixer; 5 is the temperature sensor; 6 is the chlorate decomposition tank; 7 is the online acid concentration meter; 8 is the chlorate pump; 9 is the outlet control valve; and 10 is the dechlorination tower.

[0025] A is the chlorine main pipe;

[0026] B is the overall manager in charge of pest control;

[0027] C is the hydrochloric acid input terminal;

[0028] D is the steam input terminal;

[0029] E is a chlorinated dilute saline solution. Detailed Implementation

[0030] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments.

[0031] See attached document Figure 1 The purpose of this invention is to provide a method for improving the decomposition capacity of chlorate via ion-exchange membrane without disrupting the existing recycling model, thereby reducing hydrochloric acid usage, increasing the processing capacity of the chlorate decomposition device, stabilizing the chlorate content in the brine system and liquid alkali, and improving product quality. This method includes the following steps:

[0032] Step 1: The chlorine-containing brine E, which has been heated by the chlorate heat exchanger 3, is mixed with the hydrochloric acid solution in the static mixer 4 and then enters the chlorate decomposition tank 6 for decomposition. The flow rate of the chlorine-containing brine E is determined by the liquid level in the chlorate decomposition tank 6, and the flow rate of the hydrochloric acid is determined by the acidity of the brine at the outlet of the chlorate decomposition tank 6.

[0033] Step 2: The brine after decomposition in the chlorate decomposition tank 6 is pumped into the dechlorination tower 10 via the chlorate pump 8. The flow rate of the decomposed brine is determined by the acidity of the dechlorination system.

[0034] Step 3: After the chlorine-containing brine E is decomposed in the chlorate decomposition tank 6, the chlorine gas produced is sent to the chlorine main pipe A via the gas phase pipeline. In case of abnormality, the chlorine gas is sent to the pest control system via the pest control main pipe B.

[0035] Furthermore, step 1 includes a steam input terminal D, which is connected to one of the inlets of the chlorate heat exchanger 3. The steam input terminal D is used to input working steam into the chlorate heat exchanger 3, enabling the chlorate heat exchanger 3 to meet the heating operation requirements of the chlorinated brine E.

[0036] Furthermore, in step 1, the chlorinated brine E enters the chlorate heat exchanger 3 through another inlet, where the temperature is increased to 95-98°C. Then, it is mixed thoroughly with a 31wt% hydrochloric acid solution in a static mixer 4 before entering the chlorate decomposition tank 6.

[0037] Furthermore, in step 1, the steam input terminal D is equipped with a steam control valve 2, which is used to control the steam supply to the chlorate heat exchanger 3. A temperature sensor 5 is installed on the outlet pipeline of the static mixer 4, and the temperature sensor 5 is signal-connected to the steam control valve 2, so that the steam input terminal D can adjust the steam supply rate and steam supply quantity to the chlorate heat exchanger 3 according to the outlet temperature of the static mixer 4.

[0038] Furthermore, in step 1, the liquid level in the chlorate decomposition tank 6 is controlled at 1.9–2.0 m.

[0039] Furthermore, in step 1, the chlorate decomposition tank 6 is equipped with a remote thermometer, which controls the temperature to above 90°C, in order to monitor the temperature of the chlorate decomposition tank 6 and ensure that the chlorinated brine E is always at the optimal reaction temperature in the chlorate decomposition tank 6.

[0040] Furthermore, in step 2, the outlet of the chlorate decomposition tank 6 contains dilute brine ClO. 3- The content should be controlled at ≤2.0mg / L.

[0041] Furthermore, in step 2, the acidity of the dilute brine solution at the outlet of the chlorate decomposition tank 6 is 0.30-0.40 mol / L.

[0042] Furthermore, in step 2, an online pH meter 7 is installed on the outlet pipeline of the chlorate decomposition tank 6, and a hydrochloric acid control valve 1 is installed at the hydrochloric acid input end C. The online pH meter 7 is connected to the hydrochloric acid control valve 1 by signal, and the hydrochloric acid flow rate is controlled according to the value measured by the online pH meter 7.

[0043] Furthermore, in step 2, a chlorate pump 8 is installed between the chlorate decomposition tank 6 and the dechlorination tower 10, and an outlet control valve 9 is installed on the outlet pipeline of the chlorate pump 8. The online pH meter 7 is connected to the outlet control valve 9 by signal, and the flow rate of the decomposed brine entering the dechlorination tower is controlled according to the value measured by the online pH meter 7.

[0044] Furthermore, in step 3, when the chlorine-containing brine E just begins to decompose, if the content of the decomposed chlorine gas is <95% v / v, it is removed from the chlorine removal system by the main chlorine removal pipe B. After the device is running stably, samples are continuously taken, and the purity of the chlorine gas is ≥95% v / v. The decomposed chlorine gas then enters the chlorine main pipe A.

[0045] Appendix Figure 2 The lowest inlet flow rate of the chlorate decomposition tank during the statistical period was 8.16 m³ / s. 3 / h, maximum 9.29m 3 / h, average 8.70m 3 The flow rate is increasing by 1 / h, and as the chlorate decomposition system operates stably, the overall flow rate shows an upward trend.

[0046] Appendix Figure 3 During the statistical period, chlorate exports ClO 3- The content ranged from a minimum of 0.4 g / L to a maximum of 1.92 g / L, with an average of 1.07 g / L. Most of the data were concentrated between 0.7 and 1.5 g / L, and all data were ≤2.0 g / L.

[0047] Appendix Figure 4 During the statistical period, the lowest chlorate acidity was 0.3039 mol / L, the highest was 0.3996 mol / L, and the average was 0.3495 mol / L. Most values ​​were concentrated between 0.32 and 0.37 mol / L, and all data were between 0.30 and 0.40 mol / L.

[0048] The above description represents preferred embodiments of the present invention. It should be noted that this description is not exhaustive or does not limit the present invention to the disclosed forms. For those skilled in the art, various improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are intended to better illustrate the principles and practical applications of the present invention and to enable those skilled in the art to understand the present invention and design various embodiments with various modifications suitable for specific purposes.

Claims

1. A treatment method for improving the decomposition capacity of chlorate via ion-exchange membrane process, characterized in that: The process for producing chlorate by decomposition includes the following steps: Step 1: The chlorinated brine that has been heated by the chlorate heat exchanger is mixed with the hydrochloric acid solution in a static mixer and then fed into the chlorate decomposition tank for decomposition. Step 2: The brine produced after decomposition in the chlorate decomposition tank is pumped into the dechlorination tower via a chlorate pump; Step 3: The chlorine gas produced after the chlorine-containing brine is decomposed in the chlorate decomposition tank is sent to the chlorine main pipeline via the gas phase pipeline.

2. The treatment method for improving the chlorate decomposition ability of the ion-exchange membrane method according to claim 1, characterized in that: In step 1, the chlorinated brine is heated to 95-98°C by a chlorate heat exchanger and then mixed thoroughly with a 31wt% hydrochloric acid solution in a static mixer before entering the chlorate decomposition tank.

3. The treatment method for improving the chlorate decomposition ability of the ion-exchange membrane method according to claim 2, characterized in that: A temperature sensor is installed on the outlet pipeline of the static mixer in step 1.

4. The treatment method for improving the chlorate decomposition ability of the ion-exchange membrane method according to claim 2, characterized in that: A temperature sensor is installed on the chlorate decomposition tank in step 1.

5. The treatment method for improving the chlorate decomposition ability of the ion-exchange membrane method according to claim 1, characterized in that: In step 1, the liquid level in the chlorate decomposition tank is controlled at 1.9–2.0 m.

6. The treatment method for improving the chlorate decomposition ability of the ion-exchange membrane method according to claim 1, characterized in that: In step 2, the acidity of the dilute brine solution at the outlet of the chlorate decomposition tank is 0.30-0.40 mol / L.

7. The treatment method for improving the chlorate decomposition ability of the ion-exchange membrane method according to claim 1, characterized in that: In step 2, the brine ClO at the outlet of the chlorate decomposition tank... 3- The content should be controlled at ≤2.0mg / L.

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