System and method for removing saponified substances in strip steel alkali wash water

Abstract

A system for removing saponified substances in strip steel alkali wash water comprises an alkali wash water circulating tank, a defoaming tank, a reaction tank, a saponified substance precipitating agent storage tank, a saponified substance separating tank, a saponified substance dehydrator, a bag filter and a purified liquid storage tank, and is characterized in that a centrifugal defoaming machine (7) is arranged at the top of the defoaming tank (4), and a stirring motor (13) is arranged on the reaction tank (12); a saponified matter precipitating agent is added through a metering pump (15), a saponified matter skimming machine (19) is arranged at the top of the saponified matter separating tank (18), and skimmed saponified matter flows into a saponified matter dehydrator (27). The system and method for removing the saponified matter in the strip steel alkali wash water have the advantages that the foam generation amount is reduced by 5% or above, the washing water consumption after strip steel alkali wash is reduced by 10% or above, the waste alkali liquor discharge amount is reduced by 30% or above, the alkali wash water utilization rate is increased, and the industrial water consumption is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of purification of strip alkaline cleaning solution. Specifically, it is a system and method for removing saponified substances in strip alkaline cleaning solution. Background Art

[0002] After cold rolling, the surface of the strip raw material remains with rolling oil, iron powder and pollutants during the rolling process. Before annealing, the residues on the strip surface must be removed. Otherwise, carbonaceous stains will be formed during the annealing process, polluting the furnace atmosphere, furnace rolls and strip surface. Therefore, pre-annealing cleaning is an important link in the production of continuous annealing units. During the process of removing rolling oil and iron powder on the strip surface, sodium hydroxide in the alkaline cleaning solution will react with the rolling oil to produce saponified substances. An appropriate amount of saponified substances helps with degreasing of the alkaline cleaning solution. However, when excessive saponified substances exist in the alkaline cleaning solution, it will cause an increase in foam during the circulation of the alkaline cleaning solution, excessive consumption of industrial water during the water washing process after strip alkaline cleaning, and during the shutdown and maintenance of the unit, with the decrease in the temperature of the alkaline solution in the pipeline, a large amount of saponified substances will precipitate, forming a jelly-like substance with other impurities in the alkaline cleaning solution, blocking the pipeline and filter.

[0003] Currently, for the purification technology of alkaline cleaning solution, it is all about removing insoluble impurities such as grease or iron powder in the alkaline cleaning solution, or eliminating the foam in the alkaline cleaning solution. For example, in CN201910045708.1, a pickling liquor recycling system for strip steel, the method of spraying and defoaming is used to solve the problem of the influence of lye foam on the reuse of lye. In CN201720696785.X, a pickling liquor purification device for strip steel and a strip steel cleaning device including it, after removing iron powder and grease in the alkaline cleaning solution by using a high-intensity magnetic filter and a microfilter, the alkaline cleaning solution can be reused, greatly reducing the discharge amount of waste lye. In CN200910047969.3, a method and equipment for purifying pickling liquor of silicon steel, a centrifuge and a gravity settling tank are used to remove iron powder and silicon dioxide particles in the alkaline cleaning solution to prevent the pipeline of the lye circulation system from being blocked. In CN201920267709.6, an alkaline liquor purification device uses an inclined plate sedimentation tank, a microfiltration device, a press, etc. to remove suspended substances such as grease, metal powder, and scale particles in the alkaline cleaning solution, enabling the alkaline cleaning solution to be reused. The above patents can solve the defoaming of alkaline cleaning solution and the removal of insoluble impurities, but they do not involve the saponified matter in the alkaline cleaning solution. With the recycling of the alkaline cleaning solution, the content of saponified matter in the alkaline cleaning solution will gradually accumulate until it reaches saturation. After the saponified matter in the alkaline cleaning solution reaches saturation, with the progress of pickling, saponified matter is still continuously generated, and the excess saponified matter will precipitate. Along with impurities such as iron powder being filtered and removed by the alkaline cleaning solution purification system, the saponified matter in the alkaline cleaning solution is still in a saturated state. When the content of saponified matter reaches the saturation state, it will reduce the pickling efficiency. Sometimes, it is necessary to update part of the alkaline cleaning solution to improve the pickling efficiency. Therefore, whether considering reducing the foam generation amount of alkaline cleaning solution, reducing cleaning water consumption, reducing the risk of pipeline and filter blockage, or improving pickling efficiency, it is very necessary to remove the saponified matter in the alkaline cleaning solution. Summary of the Invention

[0004] The purpose of the present invention is to provide a safe and reliable system for removing saponified matter in pickling liquor of strip steel.

[0005] Another purpose of the present invention is to provide a safe and reliable method for removing saponified matter in pickling liquor of strip steel.

[0006] To achieve the above purposes, the technical solution of the present invention is as follows: A system for removing saponified matter in pickling liquor of strip steel, including an alkaline cleaning solution circulation tank and a saponified matter precipitant storage tank, is characterized in that: The top of the alkaline cleaning solution circulation tank is provided with a foam overflow port, and the bottom is provided with a first switching valve. The foam overflow port is communicated with the top foam inlet of the defoaming tank through a pipeline. The top of the defoaming tank is also provided with a centrifugal defoaming machine, which is electrically connected to a foam level switch. The bottom of the defoaming tank is filled with a second switching valve, and the second switching valve is connected to a first lifting pump. The first lifting pump is communicated with the bottom of the reaction tank through a pipeline; the outlet end of the first switching valve is communicated with the outlet end of the second switching valve through a heat exchanger; The bottom of the saponified product precipitant storage tank is communicated with the reaction tank provided with a stirring motor at the top through a metering pump; the bottom of the reaction tank is communicated with a saponified product separation tank through a second lifting pump. The top of the saponified product separation tank is provided with a saponified product skimmer, and the upper part of the saponified product separation tank is provided with a saponified product outlet and an alkaline solution overflow port. The alkaline solution overflow port enters an intermediate water tank through a pipeline. The intermediate water tank is communicated with a third lifting pump through an intermediate water tank level gauge. The third lifting pump is connected to a bag filter. The outlet end of the bag filter is connected to a purified liquid storage tank. The purified liquid storage tank is provided with a purified liquid storage tank level gauge. The bottom of the purified liquid storage tank is provided with an alkaline cleaning solution return pump, and the alkaline cleaning solution return pump returns to the alkaline cleaning solution circulation tank through a loop; Among them: the saponified product outlet is communicated with a saponified product dehydrator, and the saponified product dehydrator is communicated with a saponified product storage tank.

[0007] The system for removing saponified products from strip alkaline cleaning solution of the present invention can also be further realized by adopting the following technical measures.

[0008] In the aforementioned system for removing saponified products from strip alkaline cleaning solution, the defoaming tank is provided with a defoaming tank level gauge.

[0009] In the aforementioned system for removing saponified products from strip alkaline cleaning solution, stirring blades are provided in the reaction tank.

[0010] In the aforementioned system for removing saponified products from strip alkaline cleaning solution, the reaction tank is a reaction tank with a conical bottom.

[0011] In the aforementioned system for removing saponified products from strip alkaline cleaning solution, the bottom of the reaction tank is provided with a reaction tank level gauge.

[0012] A method for removing saponified products from strip alkaline cleaning solution, which operates based on PLC control, is characterized by including the following steps: a. The foam in the alkaline cleaning solution circulation tank flows into the defoaming tank through the foam overflow port and the defoaming tank foam inlet. A foam level switch is provided at the top of the defoaming tank 4 and is interlocked with the centrifugal defoaming machine. When the foam level reaches the height of the bottom inlet of the centrifugal defoaming machine of 500 - 500 mm, the centrifugal defoaming machine is started. When the foam level is as low as the height of the bottom inlet of the centrifugal defoaming machine of 300 - 600 mm, the operation of the centrifugal defoaming machine is stopped; b. The defoaming tank is equipped with a liquid level gauge interlocked with the first switching valve and the second switching valve. When the liquid level gauge reaches 60 - 80%, the second switching valve and the first lift pump are opened. When the liquid level in the defoaming tank is lower than 5 - 30%, the second switching valve is closed, and at the same time, the first switching valve is opened, so that the defoamed lye in the defoaming tank and part of the alkaline washing circulating liquid enter the reaction tank. The reaction tank is provided with a reaction tank liquid level gauge interlocked with the second switching valve and the first lift pump. When the reaction tank liquid level reaches 60 - 80%, the second switching valve and the first lift pump are closed; c. The alkaline washing circulating liquid enters the heat exchanger after passing through the first switching valve, and after reducing the temperature of the alkaline washing liquid to 10 - 30°C, it enters the reaction tank; d. A stirring motor is arranged on the top of the reaction tank. After step b is completed, the stirring motor and the metering pump are started, and the saponified matter precipitant is added quantitatively; e. The reaction tank liquid level gauge is interlocked with the second lift pump, the saponified matter skimmer and the saponified matter dehydrator. After step c is completed, the second lift pump, the saponified matter skimmer and the saponified matter dehydrator are started. When the reaction tank liquid level is 5 - 10%, the second lift pump, the saponified matter skimmer and the saponified matter dehydrator stop running. During the process, the saponified matter floats on the liquid surface of the saponified matter separation tank. Under the action of the saponified matter skimmer, the saponified matter and a small amount of alkaline washing liquid flow into the saponified matter dehydrator through the saponified matter outlet together. The dehydrated saponified matter falls into the saponified matter storage tank, and the alkaline washing liquid flows into the purified liquid storage tank; f. During the operation of step d, the separated alkaline washing liquid flows into the intermediate water tank through the alkaline liquid overflow port. The intermediate water tank is equipped with a liquid level gauge interlocked with the third lift pump. When the liquid level reaches 70 - 90%, the third lift pump is started, and the alkaline washing liquid is pumped into the bag type filter to filter out a small amount of insoluble substances in the alkaline washing liquid and then flows into the purified liquid storage tank. When the liquid level of the intermediate water tank ( 22 ) is lower than 5 - 20%, the third lift pump stops running; g. The purified liquid storage tank is equipped with a liquid level gauge interlocked with the alkaline washing liquid reflux pump. When the liquid level in the purified liquid storage tank reaches 60 - 80%, the alkaline washing liquid reflux pump is started to pump the purified alkaline washing liquid back to the alkaline washing liquid circulation tank. When the liquid level in the purified liquid storage tank is 5 - 20%, the alkaline washing liquid reflux pump stops running; h. The saponified matter precipitant is a mixed solution of NaOH, Na₂CO₃ and Na₃PO₄. The content of NaOH is 0 - 50%, the content of Na₂CO₃ is 0 - 30%, and the content of Na₃PO₄ is 0 - 15%. The saponified matter precipitant is added according to the treatment volume of the alkaline washing liquid, and the addition amount is 2 - 50%; i. The solution in the reaction tank is pumped into the saponified matter separation tank through the second lift pump. After the saponified matter separation tank satisfies a solution residence time of 1 - 3 h, it flows out through the overflow port to the intermediate water tank.

[0013] The method for removing saponified matter from strip steel alkaline washing liquid of the present invention can also be further realized by adopting the following technical measures.

[0014] The foregoing method, wherein the stirring motor is controlled by a frequency converter.

[0015] The foregoing method, wherein in step d, the stirring motor stirs at a speed of 100 - 200 r / min for 10 - 60 min, and then stirs at a speed of 5 - 30 r / min for 30 - 240 min.

[0016] The foregoing method, wherein in step i, the saponified matter skimmer arranged at the top of the saponified matter separation tank rotates at a speed of 2 - 10 r / min.

[0017] The foregoing method, wherein the filtration accuracy of the bag filter is 1 - 20 μm.

[0018] The foregoing method, wherein the saponified matter dehydrator is a vacuum belt filter or a spiral press filter.

[0019] After adopting the above technical solution, the system and method for removing saponified matter in strip steel alkaline cleaning solution of the present invention have the following advantages: 1. Effectively reduce the saponified matter in the solution formed after the foam breaks in the defoaming system and the saponified matter in the alkaline cleaning circulating liquid when entering the defoaming system of the alkaline cleaning liquid circulation system; 2. Can continuously keep the saponified matter in the alkaline cleaning liquid in an unsaturated state, the foam generation amount is reduced by more than 5%, and the water consumption for cleaning the strip steel after alkaline cleaning is reduced by more than 10%; 3. The discharge amount of waste alkaline liquid is reduced by more than 30%, improving the utilization rate of the alkaline cleaning liquid and reducing the industrial water consumption. Description of the Drawings

[0020] Figure 1 It is a process flow chart of the strip steel alkaline cleaning liquid foam elimination and saponified matter removal system according to the embodiment of the present invention.

[0021] In the figure: 1. Alkaline cleaning liquid circulation tank; 2. Foam overflow port; 3. First switching valve; 4. Defoaming tank; 5. Defoaming tank foam inlet; 6. Foam level switch; 7. Centrifugal defoaming machine; 8. Defoaming tank liquid level gauge; 9. Second switching valve; 10. Heat exchanger; 11. First lift pump; 12. Reaction tank; 13. Stirring motor; 14. Saponified matter precipitant storage tank; 15. Metering pump; 16. Reaction tank liquid level gauge; 17. Second lift pump; 18. Saponified matter separation tank; 19. Saponified matter skimmer; 20. Saponified matter outlet; 21. Alkaline liquid overflow port; 22. Intermediate water tank; 23. Intermediate water tank liquid level gauge; 24. Third lift pump; 25. Bag filter; 26. Purified liquid storage tank; 27. Saponified matter dehydrator; 28. Saponified matter storage tank; 29. Purified liquid storage tank liquid level gauge; 30. Alkaline cleaning liquid reflux pump. Detailed Embodiments

[0022] The present invention will be further described in detail below with reference to the embodiments and their accompanying drawings.

[0023] Example 1 A continuous annealing unit adopts a method and system for removing saponified substances from strip steel pickling solution according to the present invention. Due to the large amount of foam generated in the unit, the defoaming machine operates frequently, and there is a large amount of solution after defoaming, a defoaming tank with an effective volume of 6.5 m³ is set up. Only the saponified substances in the foam generated from the pickling circulating solution need to be removed, and it is implemented according to the technical scheme of the present invention: A foam high and low level switch (6) is set at the top of the defoaming tank (4). The height of the high level probe from the bottom inlet of the centrifugal defoaming machine (7) is 100, and the height of the low level probe from the bottom inlet of the centrifugal defoaming machine (7) is 400 mm. When the foam height reaches the high level, the centrifugal defoaming machine (7) is started, and when it runs to the low level, the centrifugal defoaming machine (7) stops running.

[0024] A differential pressure liquid level gauge (not shown in the figure) is set at the bottom of the defoaming tank (4) and interlocked with the first lift pump (11). The high liquid level is set at 80% of the effective height of the tank body, and the low liquid level is set at 10%. When the high liquid level is reached, the first lift pump (11) is started, and when the low liquid level is reached, the first lift pump (11) stops running. About 4.5 m³ of solution is pumped into the reaction tank (12), and the flow rate of the first lift pump (11) is 12 m³ / h.

[0025] 3) After the first lift pump (11) stops running, start the stirring motor (13) and the metering pump (15), quantitatively add 450 L of saponified substance precipitant, stir with the stirring paddle at a speed of 150 r / min for 30 min, and then stir at a speed of 5 r / min for 60 min.

[0026] 4) Under the condition of continuous stirring at a speed of 5 r / min, start the second lift pump (17), the saponified substance skimmer (19) and the saponified substance dehydrator (27). When the value of the differential pressure liquid level gauge (not shown in the figure) installed at the bottom of the reaction tank (12) reaches 5%, stop the second lift pump (17), the saponified substance skimmer (19) and the saponified substance dehydrator (27) from running.

[0027] 5) The flow rate of the second lift pump (17) is 2.4 m³ / h, and the effective volume of the saponified substance separation tank (18) is 4.1 m³ 6) A differential pressure liquid level gauge (not shown in the figure) is set in the intermediate water tank (22). When the liquid level reaches 90%, start the third lift pump (24) to pump the pickling solution into the bag filter (25) with a filtration accuracy of 5 μm, and stop the third lift pump (24) when the liquid level reaches 5%.

[0028] 7) A differential pressure liquid level gauge (not shown in the figure) is provided for the purified liquid storage tank (26). When the liquid level of the purified liquid storage tank (26) reaches 80%, the caustic wash liquor reflux pump (30) is started to pump the purified caustic wash liquor back to the caustic wash liquor circulation tank (1), and the operation of the caustic wash liquor reflux pump (30) is stopped when the liquid level of the purified liquid storage tank (26) is 5%.

[0029] 8) The component contents of the saponified matter precipitant are as follows: the content of NaOH is 15%, the content of Na2CO3 is 5%, and the content of Na3PO4 is 5%. 9) The rotation speed of the saponified matter skimmer (19) is 4.5 r / min.

[0030] 10) The saponified matter dehydrator (27) is a vacuum belt filter.

[0031] After adopting the technical solution of the present invention, after 6 months of continuous operation, the unit removes about 110 kg of saponified matter in the caustic wash liquor per day on average. The start-up frequency of the centrifugal defoamer is extended from an average of 4 minutes and 25 seconds to 5 minutes and 4 seconds. The foam generation amount is reduced by 14.7%. The amount of cleaning water used after strip caustic washing is reduced by 12.5%. The discharge amount of waste caustic liquor is reduced by about 35.5%. No pipeline blockage problem occurs during the unit maintenance process.

[0032] Example 2 For a cold rolling tin plating unit, the electrolytic caustic wash circulating liquid adopts a method and system for removing saponified matter from strip caustic wash liquor of the present invention. Due to the small amount of foam generated and less solution after defoaming, a defoaming tank with an effective volume of 2 m³ is set. The saponified matter in the foam generated by the caustic wash circulating liquid and the saponified matter in part of the caustic wash liquor are removed simultaneously. Implement according to the technical solution of the present invention: A foam high and low liquid level switch (6) is provided at the top of the defoaming tank (4). The height of the high liquid level probe from the bottom inlet of the centrifugal defoamer (7) is 50, and the height of the low liquid level probe from the bottom inlet of the centrifugal defoamer (7) is 400 mm. When the foam height reaches the high liquid level, the centrifugal defoamer (7) is started and stops running when it reaches the low liquid level.

[0033] A differential pressure liquid level gauge (not shown in the figure) is provided at the bottom of the defoaming tank (4) and interlocked with the first switching valve (3) and the second switching valve (9). When the liquid level gauge reaches 85%, the second switching valve (9) and the first lift pump (11) are opened. When the liquid level of the defoaming tank (4) is lower than 10%, the second switching valve (9) is closed, and at the same time, the first switching valve (3) is opened. When the liquid level of the reaction tank (12) reaches 80%, the second switching valve (9) and the first lift pump (11) are closed. The effective volume of the reaction tank (12) is 5 m³. About 1.5 m³ of solution is pumped in from the defoaming tank (4), and about 2.5 m³ of solution is pumped in from the caustic wash liquor circulation tank (1). The flow rate of the first lift pump (11) is 12 m³ / h.

[0034] 3) After the first lift pump (11) stops running, start the stirring motor (13) and metering pump (15), quantitatively add 400 L of saponified product precipitant, stir with the stirring paddle at a speed of 150 r / min for 20 min, and then stir at a speed of 5 r / min for 60 min.

[0035] 4) Under the state of continuous stirring at a speed of 5 r / min, start the second lift pump (17), saponified product skimmer (19) and saponified product dehydrator (27), and stop the operation of the second lift pump (17), saponified product skimmer (19) and saponified product dehydrator (27) when the value of the differential pressure liquid level gauge (not shown in the figure) installed at the bottom of the reaction tank (12) reaches 5%.

[0036] 5) The flow rate of the second lift pump (17) is 2.4 m³ / h, and the effective volume of the saponified product separation tank (18) is 4.1 m³ 6) A differential pressure liquid level gauge (not shown in the figure) is set in the intermediate water tank (22). When the liquid level reaches 90%, start the third lift pump (24), pump the alkali cleaning solution into the bag filter (25) with a filtration accuracy of 5 μm, and stop the operation of the third lift pump (24) when the liquid level reaches 5%.

[0037] 7) A differential pressure liquid level gauge (not shown in the figure) is set in the purified liquid storage tank (26). When the liquid level of the purified liquid storage tank (26) reaches 80%, start the alkali cleaning solution reflux pump (30), pump the purified alkali cleaning solution back to the alkali cleaning solution circulation tank (1), and stop the operation of the alkali cleaning solution reflux pump (30) when the liquid level of the purified liquid storage tank (26) is 5%.

[0038] 8) The component contents of the saponified product precipitant are: the content of NaOH is 10%, and the content of Na3PO4 is 5%; 9) The rotation speed of the saponified product skimmer (19) is 4.5 r / min.

[0039] 10) The saponified product dehydrator (27) is a vacuum belt filter.

[0040] After adopting the technical solution of the present invention, after 6 months of continuous operation, the unit removes about 20 kg of saponified products in the alkali cleaning solution per day on average. The start-up frequency of the centrifugal defoamer is extended from an average of 20 min to 24 min, the foam generation amount is reduced by 20%, the cleaning water consumption after strip steel alkali cleaning is reduced by 15.3%, the waste alkali solution discharge amount is reduced by about 38.7%, and no pipeline blockage problem occurs during the unit maintenance process.

[0041] The present invention has substantial features and remarkable technical progress. The system and method for removing saponified substances in the strip alkaline cleaning solution of the present invention are based on the fact that during the alkaline cleaning process of the strip, sodium hydroxide in the degreasing agent will undergo a saponification reaction with some of the grease on the strip surface to generate saponified substances. Saponified substances are a kind of surfactant and have an emulsifying effect on grease. Therefore, during the process of removing saponified substances from the alkaline cleaning solution, it is not necessary to remove all saponified substances, only partial removal is required to reduce the content of saponified substances in the alkaline cleaning solution. The strip alkaline cleaning solution circulation system generally is equipped with a defoaming system and an alkaline cleaning solution purification system. The foam generated in the alkaline cleaning solution overflows to the defoaming system, and the alkaline cleaning solution is pumped into the alkaline cleaning solution purification system through a pump. The alkaline cleaning solution defoaming system can be divided into chemical defoaming and mechanical defoaming. The alkaline cleaning solution purification system is to filter and remove insoluble impurities such as grease and iron powder in the alkaline cleaning solution. Chemical defoaming is to add a defoaming agent to the alkaline cleaning solution to reduce the surface tension of the foam and achieve the purpose of defoaming. However, excessive addition of the defoaming agent will increase the difficulty of strip cleaning. A large amount of foam will be generated during the recycling process of the alkaline cleaning solution. The content of saponified substances in the foam is higher than that in the alkaline cleaning solution, and the content of saponified substances in the solution generated after mechanical defoaming of the foam is also higher than that in the alkaline cleaning solution. The system and method for removing saponified substances in the strip alkaline cleaning solution of the present invention mainly aim to remove saponified substances from the alkaline cleaning solution in the defoaming system. During the foam accumulation process, saponified substances can also be directly removed from the alkaline cleaning circulating solution. The alkaline cleaning solution after removing saponified substances and the alkaline cleaning solution purified by the alkaline cleaning solution purification system return to the alkaline cleaning solution circulation system together. Such a treatment method can not only reduce the adverse effects caused by excessive saponified substances on production, but also retain the emulsifying effect of saponified substances on grease.

[0042] The above embodiments are only for illustrating the present invention and not for limiting it. Those skilled in the relevant technical fields can make various transformations or changes without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also belong to the scope of the present invention and should be defined by each claim.

Claims

1. A system for removing saponified substances in strip steel alkaline cleaning solution, comprising an alkaline cleaning solution circulation tank (1), an antifoaming tank (4), a reaction tank (12), a saponified substance precipitant storage tank (11), a saponified substance separation tank (18), a saponified substance dehydrator (27), a bag filter (25) and a purified liquid storage tank (26), characterized in that: The top of the alkaline cleaning solution circulation tank (1) is provided with a foam overflow port (2), and the bottom is provided with a first switching valve (3). The foam overflow port (2) is communicated with the foam inlet (5) at the top of the antifoaming tank (4) through a pipeline. The top of the antifoaming tank (4) is also provided with a centrifugal antifoaming machine (7). The centrifugal antifoaming machine (7) is electrically connected to a foam level switch (6). The bottom of the antifoaming tank (4) is filled with a second switching valve (9). The second switching valve (9) is connected to a first lift pump (11). The first lift pump (11) is communicated with the bottom of the reaction tank (12) through a pipeline; the outlet end of the first switching valve (3) is communicated with the outlet end of the second switching valve (9) through a heat exchanger (10); The bottom of the saponified substance precipitant storage tank (14) is communicated with the reaction tank (12) provided with a stirring motor (13) through the top of a metering pump (15); the bottom of the reaction tank (12) is communicated with the saponified substance separation tank (18) through a second lift pump (17). The top of the saponified substance separation tank (18) is provided with a saponified substance skimmer (19). The upper part of the saponified substance separation tank (18) is provided with a saponified substance outlet (20) and an alkaline liquid overflow port (21). The alkaline liquid overflow port (21) enters an intermediate water tank (22) through a pipeline. The intermediate water tank (22) is communicated with a third lift pump (24) through an intermediate water tank level gauge (23). The third lift pump (24) is communicated with the bag filter (25). The outlet end of the bag filter (25) is connected to the purified liquid storage tank (26). The purified liquid storage tank (26) is provided with a purified liquid storage tank level gauge (29). The bottom of the purified liquid storage tank (26) is provided with an alkaline cleaning solution reflux pump (30). The alkaline cleaning solution reflux pump (30) returns to the alkaline cleaning solution circulation tank (1) through a loop; Wherein: the saponified substance outlet (20) is communicated with the saponified substance dehydrator (27), and the saponified substance dehydrator is communicated with the saponified substance storage tank (28); The outlet end pipeline of the sewage discharge valve at the bottom of the saponified substance precipitation tank (18) is communicated with the outlet end pipeline of the liquid discharge valve at the bottom of the intermediate water tank (22).

2. The saponified matter removal system in the strip steel caustic cleaning solution according to claim 1, wherein The antifoaming tank (4) is provided with a foam level switch (6) and an antifoaming tank level gauge (8).

3. The saponified product removal system in the strip steel caustic cleaning solution according to claim 1, characterized in that, The reaction tank (12) is provided with stirring blades inside.

4. The saponified matter removal system in the strip steel caustic cleaning solution according to claim 1, wherein The reaction tank (12) is a reaction tank with a conical bottom.

5. The saponified substance removal system in the strip steel caustic cleaning solution according to claim 1, characterized in that, The bottom of the reaction tank (12) is provided with a reaction tank level gauge (16).

6. A method for removing saponified matter in the strip steel caustic cleaning solution as described in claim 1, characterized in that, Including the following steps: a. The foam in the alkaline cleaning solution circulation tank passes through the foam overflow port (2) and flows into the antifoaming tank (4) through the foam inlet (5) of the antifoaming tank. A foam level switch at the top of the antifoaming tank (4) is interlocked with the centrifugal antifoaming machine (7). When the foam level reaches the bottom inlet height of the centrifugal antifoaming machine (7) of 500 - 500 mm, the centrifugal antifoaming machine (7) is started. When the foam level is as low as the bottom inlet height of the centrifugal antifoaming machine (7) of 300 - 600 mm, the operation of the centrifugal antifoaming (7) machine is stopped; b. The defoaming tank (4) is equipped with a liquid level gauge that is interlocked with the first switching valve (3) and the second switching valve (9). When the liquid level gauge reaches 60 - 80%, the second switching valve (9) and the first lift pump (11) are opened. When the liquid level in the defoaming tank (4) is lower than 5 - 30%, the second switching valve (9) is closed, and at the same time, the first switching valve (3) is opened, so that the defoamed lye in the defoaming tank (4) and part of the caustic washing circulating liquid enter the reaction tank (12). A reaction tank liquid level gauge (16) is provided at the bottom of the reaction tank (12) and is interlocked with the second switching valve (9) and the first lift pump (11). When the liquid level in the reaction tank (12) reaches 60 - 80%, the second switching valve (9) and the first lift pump (11) are closed; c. The caustic washing circulating liquid enters the heat exchanger (10) after passing through the first switching valve (3), and after reducing the temperature of the caustic washing liquid to 10 - 30°C, it enters the reaction tank (12); d. A stirring motor (13) is provided on the top of the reaction tank (12). After step b is completed, the stirring motor (13) and the metering pump (15) are started to quantitatively add the saponified matter precipitant; e. The reaction tank liquid level gauge (16) is interlocked with the second lift pump (17), the saponified matter skimmer (19), and the saponified matter dehydrator (27). After step c is completed, the second lift pump (17), the saponified matter skimmer (19), and the saponified matter dehydrator (27) are started. When the liquid level in the reaction tank (12) is 5 - 10%, the operation of the second lift pump (17), the saponified matter skimmer (19), and the saponified matter dehydrator (27) is stopped. During the process, the saponified matter floats on the liquid surface of the saponified matter separation tank (18). Under the action of the saponified matter skimmer (19), the saponified matter and a small amount of caustic washing liquid flow into the saponified matter dehydrator (27) through the saponified matter outlet together. The dehydrated saponified matter falls into the saponified matter storage tank (28), and the caustic washing liquid flows into the purified liquid storage tank (26); f. During the operation of step d, the separated caustic washing liquid flows into the intermediate water tank (22) through the caustic liquid overflow port (21). The intermediate water tank (22) is equipped with a liquid level gauge (23) that is interlocked with the third lift pump (24). When the liquid level reaches 70 - 90%, the third lift pump (24) is started to pump the caustic washing liquid into the bag filter (25). After filtering out a small amount of insoluble substances in the caustic washing liquid, it flows into the purified liquid storage tank (26). When the liquid level in the intermediate water tank (22) is lower than 5 - 20%, the operation of the third lift pump (24) is stopped; g. The purified liquid storage tank (26) is equipped with a liquid level gauge (29) that is interlocked with the caustic washing liquid reflux pump (30). When the liquid level in the purified liquid storage tank (26) reaches 60 - 80%, the caustic washing liquid reflux pump (30) is started to pump the purified caustic washing liquid back to the caustic washing liquid circulation tank (1). When the liquid level in the purified liquid storage tank (26) is 5 - 20%, the operation of the caustic washing liquid reflux pump (30) is stopped; h. The saponified matter precipitant is a mixed solution of NaOH, Na₂CO₃, and Na₃PO₄. The content of NaOH is 0 - 50%, the content of Na₂CO₃ is 0 - 30%, and the content of Na₃PO₄ is 0 - 15%; The saponified matter precipitant is added according to the treatment volume of the caustic washing liquid, and the addition amount is 2 - 50%; i. The solution in the reaction tank is pumped into the saponified product separation tank (18) by the second lift pump (17). After the solution stays in the saponified product separation tank (18) for 1 to 3 hours, it flows out through the overflow port to the intermediate water tank (22).

7. The method for removing saponified matter in strip steel caustic cleaning solution according to claim 6, characterized in that, The stirring motor (13) is controlled by a frequency converter.

8. The method for removing saponified substances in the strip caustic cleaning solution according to claim 6, characterized in that, In step d, the stirring motor (13) stirs at a speed of 100 to 200 r / min for 10 to 60 minutes, and then stirs at a speed of 5 to 30 r / min for 30 to 240 minutes.

9. The method for removing saponified matter in the strip steel caustic cleaning solution according to claim 6, characterized in that, In step i, the saponified product skimmer (19) arranged at the top of the saponified product separation tank (18) rotates at a speed of 2 to 10 r / min.

10. The method for removing saponified substances in the strip steel caustic cleaning solution according to claim 6, characterized in that, The filtration accuracy of the bag filter (25) is 1 to 20 μm.

11. The method for removing saponified matter in strip steel caustic cleaning solution according to claim 6, characterized in that, The saponified product dehydrator (27) is a vacuum belt filter or a spiral filter press.

12. A method for removing saponified substances in the strip alkali cleaning solution as described in claim 6, characterized in that, The control method uses a PLC control circuit.

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