Two-alkali automatic adjusting system in chlor-alkali production

Abstract

The invention discloses an automatic two-alkali adjusting system in chlor-alkali production. The automatic two-alkali adjusting system comprises a salt dissolving tank, a baffling tank, a reaction tank, an intermediate tank, a coarse filter, an inorganic membrane filtering unit, a static mixer I, a static mixer II and a primary saline water storage tank, wherein a two-alkali instrument is arranged in the reaction tank; wherein the formula of the relationship between the excess values of sodium hydroxide and sodium carbonate and the flow values of the added sodium hydroxide and sodium carbonate is set. According to the two-alkali automatic adjusting system, a set formula is automatically judged and used according to an analysis result, and then the adjusted flow is correspondingly calculated and executed. Wherein the opening degree of the lowest alkali flow is set, unmanned operation and automatic adjustment are completely achieved through the analysis method, multi-stage linkage is arranged, and safe production is fully guaranteed; meanwhile, the stability of two alkalis in the side reaction is determined by referring to the pH value in saline water; and the excess amount of the two alkalis is finely controlled, so that the effect of saving auxiliary materials is achieved.

Description

Technical Field

[0001] This invention relates to the field of chemical production technology, and in particular to an automatic adjustment system for alkali and sodium chloride in chlor-alkali production. Background Technology

[0002] In the primary brine production process of conventional caustic soda production enterprises, the process involves electrolyzing saturated brine. Calcium and magnesium in the raw salt need to be removed by adding sodium hydroxide and sodium carbonate. To ensure complete reaction and control costs, the excess sodium hydroxide is controlled at 0.1~0.3 g / L, and sodium carbonate at 0.3~0.5 g / L. Currently, the mainstream control method relies on frontline operators adjusting the amount of sodium hydroxide and sodium carbonate added based on experience. Insufficient addition will result in excessive calcium and magnesium content in the brine, causing the process to malfunction.

[0003] During a single brine production process, desalination needs to be added again every 1.5 hours, which causes fluctuations in the concentration of calcium and magnesium ions entering the baffle tank. Summary of the Invention

[0004] The purpose of this invention is to provide an automatic adjustment system for the two alkalis in chlor-alkali production, which solves the problems of inconvenient automatic adjustment systems for the two alkalis and waste of auxiliary materials in conventional chlor-alkali production.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: This invention provides an automatic adjustment system for chlor-alkali production, comprising a salt treatment tank, a baffle tank, a reaction tank, an intermediate tank, a coarse filter, an inorganic membrane filtration unit, a static mixer I, a static mixer II, and a primary brine storage tank. The saturated brine in the salt bath overflows into the baffle tank, where sodium hypochlorite, sodium hydroxide, and sodium carbonate are added to precipitate Ca from the saturated brine. 2+ and Mg 2+ After adding the refining agent, the saturated crude brine flows into the reaction tank by gravity. In the reaction tank, sodium hypochlorite decomposes microorganisms, sodium hydroxide reacts with magnesium ions to generate magnesium hydroxide, and sodium carbonate reacts with calcium ions to generate calcium carbonate. After the refining reaction is completed, the crude brine flows into the intermediate tank by gravity. After mechanical impurities larger than 0.6 mm are intercepted by the brine coarse filter using the membrane filtration feed pump, it is then sent to the inorganic membrane filtration unit. The refined brine filtered by each stage of the inorganic membrane filtration unit is discharged into the main pipe through the permeate outlets of each stage of the inorganic membrane brine filter, and then enters static mixer one. Before entering static mixer one, sodium sulfite is added to remove free chlorine, and then the brine enters static mixer two. Before entering static mixer two, high-purity hydrochloric acid is added to adjust the pH value, and then the brine enters the primary brine storage tank and is pumped out of the boundary area by the primary brine pump. Two alkali devices are installed in the reaction tank. The formulas relating the excess values ​​of sodium hydroxide and sodium carbonate to their respective flow rates are as follows: Sodium carbonate dosage formula: Q 总碳 =Q x碳 +Q y碳 ; Sodium hydroxide dosage formula: Q NaOH =Qx+Qy; The method involves setting a minimum alkali flow rate, which allows for fully automated, unmanned operation and multi-level interlocking, ensuring safe production. It also references the pH value in the brine to indirectly reflect the stability of the two alkalis.

[0006] In this embodiment, the formula for sodium carbonate dosage is: Q 总碳 =Q x碳 +Q y碳 ; Q x碳 =Q 当 - ; Q y碳 =Q 钙 0.4 Z 分 Q 钙 =

[0007] Note: Q 当 : Current flow rate; X 两 The two alkali meters display the following values; X 设 : Indicator setting value; Q 粗 : Coarse saline flow rate; w 碳 : Sodium carbonate concentration; ρ 碳 Specific gravity of sodium carbonate solution; Z 变 Variable coefficients (Z) 变 :X 两 -X 设 (Absolute value) less than 0.1 is taken as 1; 0.2 is taken as 1.5; 0.3 is taken as 2; 0.4 is taken as 2.5; 0.5 is taken as 10); m 上 W is the weight of salt applied in one application. 钙 This represents the percentage of calcium impurities in the raw salt. Z 分 The function is to add time-varying control (see the table below);

[0008] Q x碳 Calculate the required flow rate of sodium carbonate based on the data from the two alkali analyzers; Q y碳To address the fluctuations caused by adding salt every 1.5 hours, the sodium carbonate flow rate is adjusted to offset the amount added at the corresponding time. Sodium hydroxide dosage formula: Q NaOH =Qx+Qy; Qx=Q 当 - ; Qy=Q 钙 0.7 Z 分 Q 碱 = ; Note: Q 当 X represents the current flow rate measured by the flow meter. 两 The values ​​displayed on the two alkali analyzer; X 设 Set a value for the indicator; Q 粗 The flow rate of the crude brine; w 碱 ρ represents the concentration of sodium hydroxide. 碱 The specific gravity of 32% caustic soda solution; Z 变 For (│X) 两 -X 设 | Less than 0.1, take 1; 0.2, take 1.5; 0.3, take 2; 0.4, take 2.5; 0.5, take 10); W 镁 This refers to the magnesium content in the raw salt; w 碱 The concentration of the liquid alkali; ρ 碱 Z represents the density of the liquid alkali. 分 This represents the time-corresponding proportion; Q NaOH Q is the instantaneous flow rate of sodium hydroxide added; x Calculate the required flow rate of sodium hydroxide based on the data from the two alkali analyzers; Q y To address the fluctuations caused by adding salt over 1.5 hours, the sodium hydroxide flow rate was adjusted to offset the amount added at the corresponding time.

[0009] Furthermore, in this embodiment, the inorganic membrane filtration unit adopts a three-stage series "cross-flow" filtration method. The coarse brine solution is first sent to the first-stage filtration component of the inorganic membrane brine filter by the membrane filtration circulation pump for filtration. The concentrate from the first-stage filtration component enters the second-stage filtration component for filtration, and the concentrate from the second-stage filtration component enters the third-stage filtration component for filtration.

[0010] Furthermore in this embodiment, a small portion of the concentrated brine flowing out of the concentrated liquid outlet of the inorganic membrane brine filter is discharged to the external mud tank according to the proportion and concentration, while the remainder returns to the filter circulation tank and mixes with the coarse brine sent by the membrane filter feed pump to adjust the solid-liquid ratio of the feed liquid. This mixture then enters the inlet of the membrane filter circulation pump to control the solid content of the concentrated liquid and ensure the flow rate on the membrane surface. Finally, it returns to the inorganic membrane brine filter for internal circulation filtration via the membrane filter circulation pump.

[0011] Furthermore, in this embodiment, after prolonged operation, the inorganic membrane brine filter may experience changes in flux and a decrease in filtration capacity due to fouling on the membrane surface. Therefore, membrane regeneration is necessary to restore the membrane flux and bring the filtration capacity back to its initial state. Regeneration methods include physical backwashing and chemical cleaning. Physical backwashing involves using filtered refined brine pressurized with compressed air in a backwash tank to backwash the membrane surface. Chemical cleaning uses 10%–15% hydrochloric acid to thoroughly clean the membrane surface and fully restore the filtration flux.

[0012] Compared with the prior art, the beneficial technical effects of the present invention are as follows: In this invention, the automatic adjustment system for the two alkalis automatically determines the use of a set formula based on the analysis results, then calculates and executes the adjusted flow rate. The system sets a minimum alkali flow rate, and this analysis method achieves completely unmanned operation and automatic adjustment. Furthermore, it incorporates multi-level interlocking to fully guarantee safe production. Simultaneously, it references the pH value of the brine to indirectly reflect the stability of the two alkalis, and it precisely controls the excess of the two alkalis, thereby saving on auxiliary materials. Attached Figure Description

[0013] The present invention will be further described below with reference to the accompanying drawings.

[0014] Figure 1 This is a schematic diagram of the automatic adjustment system for the two alkalis in chlor-alkali production according to the present invention. Detailed Implementation

[0015] refer to Figure 1 This embodiment discloses an automatic adjustment system for chlor-alkali production, comprising a brine tank, a baffle tank, a reaction tank, an intermediate tank, a coarse filter, an inorganic membrane filtration unit, a static mixer I, a static mixer II, and a primary brine storage tank; the specific process flow is described below: Dechlorinated brine, recovered brine, and low-nitrate brine from outside the boundary area enter the distribution tank and are pumped to the brine heat exchanger for heating. The heated brine enters the brine tank and overflows into the brine desalination tank after saturation. In the brine tank, refining agents sodium hypochlorite, sodium hydroxide, and sodium carbonate are added. The saturated crude brine after adding the refining agents flows by gravity into the reaction tank. In the reaction tank, sodium hypochlorite decomposes microorganisms, sodium hydroxide reacts with magnesium ions to produce magnesium hydroxide, and sodium carbonate reacts with calcium ions to produce calcium carbonate. After the refining reaction is completed, the crude brine flows by gravity into the intermediate tank and is then sent to the inorganic membrane filtration unit after mechanical impurities larger than 0.6 mm are removed by the brine coarse filter using a membrane filtration feed pump.

[0016] The inorganic membrane filtration unit employs a three-stage series "cross-flow" filtration method. The coarse brine feed solution is first fed into the primary filtration module of the inorganic membrane brine filter via a membrane filtration circulation pump. The concentrate from the primary module then enters the secondary filtration module, and finally, the concentrate from the secondary filtration module enters the tertiary filtration module. A small portion of the concentrated brine flowing from the tertiary filtration module is discharged to an external sludge tank according to a specific ratio and concentration. The remainder returns to the filtration circulation tank and mixes with the coarse brine from the membrane filtration feed pump to adjust the solid-liquid ratio of the feed solution. This mixture then enters the inlet of the membrane filtration circulation pump, controlling the solid content of the concentrate and ensuring the membrane surface flow rate. Finally, it returns to the inorganic membrane brine filter via the membrane filtration circulation pump for further filtration. The refined brine filtered by each stage of the filter assembly is discharged from the permeate outlet of each stage of the inorganic membrane brine filter and enters the main pipe, then enters the first static mixer. Before entering the first static mixer, sodium sulfite is added to remove free chlorine and then enters the second static mixer. Before entering the second static mixer, high-purity hydrochloric acid is added to adjust the pH value and then enters the primary brine storage tank, and is pumped out of the boundary area by the primary brine pump.

[0017] The inorganic membrane filtration unit adopts a three-stage series "cross-flow" filtration method. The coarse brine feed solution is first sent to the first-stage filtration component of the inorganic membrane brine filter by the membrane filtration circulation pump for filtration. The concentrate from the first-stage filtration component enters the second-stage filtration component for filtration, and the concentrate from the second-stage filtration component enters the third-stage filtration component for filtration.

[0018] A small portion of the concentrated brine flowing from the outlet of the inorganic membrane brine filter is discharged to the external mud tank according to the proportion and concentration. The rest returns to the filter circulation tank and mixes with the coarse brine sent by the membrane filter feed pump to adjust the solid-liquid ratio of the feed liquid. It then enters the inlet of the membrane filter circulation pump to control the solid content of the concentrated liquid and ensure the flow rate on the membrane surface. Finally, it returns to the inorganic membrane brine filter for internal circulation filtration via the membrane filter circulation pump.

[0019] After prolonged operation, inorganic membrane brine filters may experience flux changes and decreased filtration capacity due to membrane surface fouling. Membrane regeneration is necessary to restore flux and return filtration capacity to its initial state. Regeneration methods include physical backwashing and chemical cleaning. Physical backwashing involves using pressurized compressed air in a backwash tank to backwash the membrane surface with filtered refined brine. Chemical cleaning uses 10-15% hydrochloric acid to thoroughly clean the membrane surface and fully restore filtration flux.

[0020] The reaction tank is equipped with two alkali meters for detecting the concentrations of sodium hydroxide and sodium carbonate. As a preferred option, the formula for sodium carbonate dosage is: Q 总碳 =Q x碳 +Q y碳 ; Q x碳 =Q 当 - ; Q y碳 =Q 钙 0.4 Z 分 Q 钙 = ; Note: Q 当 : Current flow rate; X 两 The two alkali meters display the following values; X 设 : Indicator setting value; Q 粗 : Coarse saline flow rate; w 碳 : Sodium carbonate concentration; ρ 碳 Specific gravity of sodium carbonate solution; Z 变 Variable coefficients (Z) 变 :X 两 -X 设 (Absolute value) less than 0.1 is taken as 1; 0.2 is taken as 1.5; 0.3 is taken as 2; 0.4 is taken as 2.5; 0.5 is taken as 10); m 上 W is the weight of salt applied in one application. 钙 This represents the percentage of calcium impurities in the raw salt. Z 分 The function is to add time-varying control (see the table below);

[0021] Q x碳 Calculate the required flow rate of sodium carbonate based on the data from the two alkali analyzers; Q y碳 To address the fluctuations caused by adding salt every 1.5 hours, the sodium carbonate flow rate is adjusted to offset the amount added at the corresponding time. Sodium hydroxide dosage formula: Q NaOH =Qx+Qy; Qx=Q 当 - ; Qy=Q 钙 0.7 Z 分 Q 碱 = ; Note: Q 当 X represents the current flow rate measured by the flow meter. 两 The values ​​displayed on the two alkali analyzer; X 设 Set a value for the indicator; Q 粗 The flow rate of the crude brine; w 碱 ρ represents the concentration of sodium hydroxide. 碱 The specific gravity of 32% caustic soda solution; Z 变 For (│X) 两 -X 设 | Less than 0.1, take 1; 0.2, take 1.5; 0.3, take 2; 0.4, take 2.5; 0.5, take 10); W 镁 This refers to the magnesium content in the raw salt; w 碱 The concentration of the liquid alkali; ρ 碱 Z represents the density of the liquid alkali. 分 This represents the time-corresponding proportion; Q NaOH Q is the instantaneous flow rate of sodium hydroxide added; x Calculate the required flow rate of sodium hydroxide based on the data from the two alkali analyzers; Q y To address the fluctuations caused by adding salt over 1.5 hours, the sodium hydroxide flow rate was adjusted to offset the amount added at the corresponding time.

[0022] In practice, the frequency of salting was adjusted, the salting time was shortened, and the salt layer was ensured to be above the water surface. Secondly, the temperature and source of the brine were adjusted to ensure the stability of the two alkalis in the brine and the constant temperature. Thirdly, the quality of the raw salt products from the raw salt manufacturers was investigated, and raw salt with relatively stable calcium and magnesium content was selected.

[0023] Application examples Actual calculations based on the current scale of the company's factory: Compared to existing sodium carbonate, this reduces the concentration by 0.1 g / L, and the production flow rate is 300 m³ / L. 3 / h, sodium carbonate is currently priced at 1300 yuan per ton; therefore, the annual savings would be 0.1. 300 twenty four 330 (working days) / 1000 1300 = 308880 yuan.

[0024] Compared to existing sodium hydroxide usage, it can be reduced by 0.1 g / L, and the flow rate during production is 300 m³ / L. 3 The current price of 32% caustic soda solution is 860 yuan per ton. Therefore, by reducing the amount of sodium hydroxide used, the annual savings would be 0.1 yuan. 300 twenty four 330 (working days) / 1000 / 0.32 860 = 638,550 yuan.

[0025] A total of 947,130 yuan can be saved.

[0026] Taking sodium carbonate as an example:

[0027] The solution in this embodiment is relatively more traditional than adding excessive sodium carbonate, which can significantly reduce the amount of sodium carbonate added.

[0028] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An automatic adjustment system for alkali and sodium chloride in chlor-alkali production, characterized in that: It includes a salt treatment tank, a baffle tank, a reaction tank, an intermediate tank, a coarse filter, an inorganic membrane filtration unit, a static mixer I, a static mixer II, and a primary brine storage tank; The saturated brine in the salt bath overflows into the baffle tank, where sodium hypochlorite, sodium hydroxide, and sodium carbonate are added to precipitate Ca from the saturated brine. 2+ and Mg 2+ After adding the refining agent, the saturated crude brine flows into the reaction tank by gravity. In the reaction tank, sodium hypochlorite decomposes microorganisms, sodium hydroxide reacts with magnesium ions to generate magnesium hydroxide, and sodium carbonate reacts with calcium ions to generate calcium carbonate. After the refining reaction is completed, the crude brine flows into the intermediate tank by gravity. After mechanical impurities larger than 0.6 mm are intercepted by the brine coarse filter using the membrane filtration feed pump, it is then sent to the inorganic membrane filtration unit. The refined brine filtered by each stage of the inorganic membrane filtration unit is discharged into the main pipe through the permeate outlets of each stage of the inorganic membrane brine filter, and then enters static mixer one. Before entering static mixer one, sodium sulfite is added to remove free chlorine, and then the brine enters static mixer two. Before entering static mixer two, high-purity hydrochloric acid is added to adjust the pH value, and then the brine enters the primary brine storage tank and is pumped out of the boundary area by the primary brine pump. Two alkali devices are installed in the reaction tank. The formulas relating the excess values ​​of sodium hydroxide and sodium carbonate to their respective flow rates are as follows: Sodium carbonate dosage formula: Q 总碳 =Q x碳 +Q y碳 ; Sodium hydroxide dosage formula: Q NaOH =Qx+Qy; By setting a minimum alkali flow rate, this analytical method achieves fully unmanned operation and automatic adjustment, and is equipped with multi-level interlocking to ensure safe production; at the same time, it indirectly reflects the stability of the two alkalis by referring to the pH value of the brine.

2. The automatic adjustment system for chlor-alkali production according to claim 1, characterized in that: Q x碳 =Q 当 - ; Q y碳 =Q 钙 0.4 Z 分 ;Q 钙 = 3. Notes: Q 当 : Current flow rate; X 两 The two alkali meters display the following values; X 设 : Indicator setting value; Q 粗 : Coarse saline flow rate; w 碳 : Sodium carbonate concentration; ρ 碳 Specific gravity of sodium carbonate solution; Z 变 Variable coefficients (Z) 变 :X 两 -X 设 (Absolute value) Less than 0.1 is assigned 1; 0.2 is assigned 1.5; 0.3 is assigned 2; 0.4 is taken as 2.5; 0.5 is taken as 10); m 上 W is the weight of salt applied in one application. 钙 This represents the percentage of calcium impurities in the raw salt. Z 分 The function is to add time-varying control (see the table below); 4.Q x碳 Calculate the required flow rate of sodium carbonate based on the data from the two alkali analyzers; Q y碳 To address the fluctuations caused by adding salt every 1.5 hours, the sodium carbonate flow rate was adjusted to offset the amount added at the corresponding time.

5. The automatic adjustment system for chlor-alkali production according to claim 1, characterized in that: Qx=Q 当 - ; Qy=Q 钙 0.7 Z 分 ;Q 碱 = ; Note: Q 当 X represents the current flow rate measured by the flow meter. 两 The values ​​displayed on the two alkali analyzer; X 设 Set a value for the indicator; Q 粗 The flow rate of the crude brine; w 碱 ρ represents the concentration of sodium hydroxide. 碱 The specific gravity of 32% caustic soda solution; Z 变 For (│X) 两 -X 设 | Less than 0.1 is assigned 1; 0.2 is assigned 1.5; 0.3 is assigned 2; 0.4 is taken as 2.5; 0.5 is taken as 10); W 镁 This refers to the magnesium content in the raw salt; w 碱 ρ is the concentration of the liquid alkali; 碱 Z represents the density of liquid alkali. 分 This represents the time-corresponding proportion; Q NaOH Q is the instantaneous flow rate of sodium hydroxide added; x Calculate the required flow rate of sodium hydroxide based on the data from the two alkali analyzers; Q y To address the fluctuations caused by adding salt over 1.5 hours, the sodium hydroxide flow rate was adjusted to offset the amount added at the corresponding time.

6. The automatic adjustment system for chlor-alkali production according to claim 1, characterized in that: The inorganic membrane filtration unit adopts a three-stage series "cross-flow" filtration method. The coarse brine feed solution is first sent to the first-stage filtration component of the inorganic membrane brine filter by the membrane filtration circulation pump for filtration. The concentrate from the first-stage filtration component enters the second-stage filtration component for filtration, and the concentrate from the second-stage filtration component enters the third-stage filtration component for filtration.

7. The automatic adjustment system for chlor-alkali production according to claim 1, characterized in that: A small portion of the concentrated brine flowing from the outlet of the inorganic membrane brine filter is discharged to the external mud tank according to the proportion and concentration. The rest returns to the filter circulation tank and mixes with the coarse brine sent by the membrane filter feed pump to adjust the solid-liquid ratio of the feed liquid. It then enters the inlet of the membrane filter circulation pump to control the solid content of the concentrated liquid and ensure the flow rate on the membrane surface. Finally, it returns to the inorganic membrane brine filter for internal circulation filtration via the membrane filter circulation pump.

8. The automatic adjustment system for chlor-alkali production according to claim 1, characterized in that: After prolonged operation, inorganic membrane brine filters may experience changes in flux and a decrease in filtration capacity due to membrane surface fouling. Membrane regeneration is necessary to restore flux and return filtration capacity to its initial state. Regeneration methods include physical backwashing and chemical cleaning. Physical backwashing involves using filtered refined brine pressurized with compressed air in a backwash tank to reverse-flush the membrane surface. Chemical cleaning uses 10%–15% hydrochloric acid to thoroughly clean the membrane surface and fully restore filtration flux.

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