A process for cleaning a chromium-containing waste solution storage vessel

Abstract

A cleaning process for chromium-containing waste liquid storage containers, relating to the fields of metallurgical machinery and energy environmental protection, includes the following steps: S1, the system operation is controlled by a PLC. An industrial water valve is opened to inject a certain level of industrial water into the reaction tank. The pump from the reaction tank to the chromium-containing waste liquid storage container is turned on, injecting the solution into the chromium-containing waste liquid storage container through a solution spray pipe. Simultaneously, the pump from the chromium-containing waste liquid storage container to the reaction tank is turned on to pump the solution back into the reaction tank. Sulfuric acid and sodium metabisulfite solution are added to the reaction tank. This process is repeated for a certain period of time. Finally, after all the solution has been pumped into the reaction tank, an online hexavalent chromium detector is started to detect the hexavalent chromium content. In this invention, multiple chromium-containing waste liquid storage containers can be treated using a small amount of industrial water and chemical reagents. The hexavalent chromium content in the treated wastewater can be less than 0.05 mg / L, saving tens of times the amount of industrial water used and reducing the amount of chromium-containing wastewater treated by tens of times, thus saving treatment costs.

Description

Technical Field

[0001] This invention relates to the fields of metallurgical machinery and energy and environmental protection, and to wastewater treatment technology, more specifically to a cleaning process for chromium-containing waste liquid storage containers. Background Technology

[0002] Hexavalent chromium has a wide range of applications in metal processing and electroplating industries. During these applications, chromium-containing wastewater is inevitably generated. Some companies that use this wastewater lack the capacity or qualifications to treat it, and the resulting wastewater must be temporarily stored in specific containers and periodically transported to qualified third-party treatment facilities. These containers used for temporarily storing and transporting the chromium-containing wastewater must be replaced after a certain number of years. The replaced containers will still contain chromium-containing wastewater and sludge residue. If the chromium-containing wastewater and sludge inside are not thoroughly cleaned, these containers will be unusable.

[0003] Some manufacturers with the capacity to treat chromium-containing wastewater use large amounts of industrial water to rinse the storage containers of chromium-containing waste liquid. After rinsing, the wastewater enters the chromium-containing wastewater treatment system and is treated until the hexavalent chromium content meets the discharge requirements. This method not only wastes a lot of industrial water, but also increases the workload of the chromium-containing wastewater treatment system.

[0004] Currently, there are many methods for cleaning solution transfer containers. For example, patents with application number CN202120799856.5, entitled "Ton Barrel Cleaning System", and application number CN202120023069.1, entitled "A Chemical Ton Barrel Cleaning Device", both have similar cleaning methods for solution transfer containers. However, using similar methods to clean chromium-containing waste liquid storage containers will not only waste a lot of industrial water, but also increase the amount of wastewater to be treated. Summary of the Invention

[0005] The main technical problem solved by this invention is to provide a cleaning process for chromium-containing waste liquid storage containers, which can solve the problems in the background art mentioned above, and realize the cleaning of multiple chromium-containing waste liquid storage containers with a small amount of industrial water and treatment reagents, and make the hexavalent chromium content in the treated solution meet the discharge requirements.

[0006] The residual solution and sludge in the chromium-containing waste liquid storage container both contain hexavalent chromium. This invention involves adding a certain amount of industrial water to a reaction tank, which is then pumped into the chromium-containing waste liquid storage container. The solution in the storage container is then pumped back to the reaction tank. Sulfuric acid and sodium metabisulfite are added to the reaction tank to reduce hexavalent chromium to trivalent chromium. The solution is then circulated between the reaction tank and the chromium-containing waste liquid storage container. The amount of sulfuric acid and sodium metabisulfite added is controlled by pH value and redox potential. The hexavalent chromium content is detected using an online hexavalent chromium detector to control the cleaning endpoint. Finally, the solution is pumped back into the reaction tank, where sodium hydroxide is added to adjust the pH to alkaline, causing trivalent chromium to precipitate.

[0007] To solve the above-mentioned technical problems, according to one aspect of the present invention, more specifically, a cleaning process for a chromium-containing waste liquid storage container includes the following steps:

[0008] S1. The system is controlled by a PLC. The industrial water valve is opened to inject a certain level of industrial water into the reaction tank. The pump from the reaction tank to the chromium-containing waste liquid storage container is turned on, and the solution is injected into the chromium-containing waste liquid storage container through the solution spray pipe. At the same time, the pump from the chromium-containing waste liquid storage container to the reaction tank is turned on to pump the solution back to the reaction tank. Sulfuric acid and sodium metabisulfite solution are added to the reaction tank. After repeated cleaning for a certain period of time, the solution is finally pumped into the reaction tank. The hexavalent chromium online detector is started to detect the hexavalent chromium content. If the hexavalent chromium content meets the emission requirements, the chromium-containing waste liquid storage container is replaced. After cleaning several chromium-containing waste liquid storage containers, the sodium hydroxide dosing pump is turned on to adjust the pH value of the solution to alkaline. After reacting for a period of time, the reaction tank drain valve is opened to discharge the solution into the wastewater treatment system.

[0009] S2. The pump from the reaction tank to the chromium-containing waste liquid storage container and the pump from the chromium-containing waste liquid storage container to the reaction tank are turned on at the same time. If the liquid level in the chromium-containing waste liquid storage container reaches the high level of the high and low level switch of the chromium-containing waste liquid storage container, the pump from the reaction tank to the chromium-containing waste liquid storage container is turned off. When the liquid level drops to the low level, the pump from the reaction tank to the chromium-containing waste liquid storage container is turned on.

[0010] S3. The sulfuric acid dosing pump on the sulfuric acid storage tank is controlled by a pH meter inside the reaction vessel.

[0011] S4. The sodium metabisulfite dosing pump on the sodium metabisulfite solution storage tank inside the reaction vessel is controlled by an ORP detector to start and stop.

[0012] S5. After both the sulfuric acid dosing pump and the sodium metabisulfite dosing pump have stopped dosing for 30-60 minutes, turn on the online hexavalent chromium detector containing solution pretreatment to detect the hexavalent chromium content.

[0013] After the S6 hexavalent chromium content test meets the standard, replace the chromium-containing waste liquid storage container;

[0014] S7. After cleaning 5 to 10 chromium-containing waste liquid storage containers, turn on the sodium hydroxide dosing pump and stop the sodium hydroxide dosing pump on the sodium hydroxide solution storage tank when the pH meter reading is greater than a certain value of 7.0 to 9.0.

[0015] S8. After adjusting the pH in the reaction tank, react for 30-60 minutes, then open the drain valve of the reaction tank to discharge the solution into the wastewater treatment system.

[0016] Furthermore, in step S3, the sulfuric acid dosing pump is turned on when the pH value is set to be greater than a certain value between 1.80 and 2.10 in the PLC, and is turned off when the pH value is set to be less than a certain value between 1.60 and 1.80.

[0017] Furthermore, in step S4, the PLC is set to start the sodium metabisulfite dosing pump when the ORP value is greater than a certain value of 300-450mV, and to stop the sodium metabisulfite dosing pump when it is less than that value.

[0018] Furthermore, a reaction tank level gauge is installed on the reaction tank.

[0019] The beneficial effects of the cleaning process for chromium-containing waste liquid storage containers of the present invention are as follows:

[0020] In this invention, multiple chromium-containing waste liquid storage containers can be treated using a small amount of industrial water and chemical reagents. After treatment, the hexavalent chromium content in the wastewater can be less than 0.05 mg / L, which can save tens of times the amount of industrial water used and reduce the amount of chromium-containing wastewater treated by tens of times. This can save treatment costs and reduce the operating load of wastewater treatment equipment. This invention is simple to implement and easy to apply. Attached Figure Description

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and specific implementation methods.

[0022] Figure 1 This is a process flow diagram of the cleaning process for the chromium-containing waste liquid storage container of the present invention.

[0023] In the diagram: 1. Chromium-containing waste liquid storage container; 2. Reaction tank; 3. Sodium metabisulfite solution storage tank; 4. Sulfuric acid storage tank; 5. Sodium hydroxide solution storage tank; 6. Online hexavalent chromium detector with solution pretreatment; 7. ORP detector; 8. pH meter; 9. Industrial water valve; 10. Sodium metabisulfite dosing pump; 11. Sulfuric acid dosing pump; 12. Sodium hydroxide dosing pump; 13. Pump from reaction tank to chromium-containing waste liquid storage container; 14. Pump from chromium-containing waste liquid storage container to reaction tank; 15. Reaction tank drain valve; 16. Reaction tank level gauge; 17. High and low level switch for chromium-containing waste liquid storage container; 18. Solution injection pipe. Detailed Implementation

[0024] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the present application can be combined with each other.

[0025] Example 1

[0026] A steel company's silicon steel semi-organic coating unit stores chromium-containing coating waste liquid in 1 cubic meter ton containers, which are then transported to a third party for treatment. The hexavalent chromium content in the remaining solution in the ton containers ranges from 2195 to 4005 mg / L, and the hexavalent chromium content in the remaining sludge is 1.53 g / kg. This technical solution is used to clean the ton containers.

[0027] S1. The sulfuric acid dosing pump 11 in reaction tank 2 is controlled by pH meter 8. When the pH value is greater than 1.95, the sulfuric acid dosing pump 11 is turned on and when the pH value is less than 1.80, the sulfuric acid dosing pump 11 is turned off.

[0028] S2. The sodium metabisulfite dosing pump 10 in reaction vessel 2 is controlled by ORP detector 7. When the ORP value is greater than 400mV, the sodium metabisulfite dosing pump 10 is turned on and when the ORP value is less than 400mV, the sodium metabisulfite dosing pump 10 is turned off.

[0029] S3. After both the sulfuric acid dosing pump 11 and the sodium metabisulfite dosing pump 10 have stopped dosing for 30 minutes, turn on the online hexavalent chromium detector 6 containing solution pretreatment to detect the hexavalent chromium content.

[0030] S4. After the hexavalent chromium content test met the standard, replace the chromium-containing waste liquid storage container 1. After cleaning the 7 ton drums according to the above procedure, the hexavalent chromium test result was 0.013 mg / L.

[0031] S5. Turn on sodium hydroxide dosing pump 12 and stop it when the pH meter reading is greater than 8.0.

[0032] S6. After adjusting the pH in the reaction tank, react for 30 minutes, then open the drain valve 15 of the reaction tank to discharge the solution into the wastewater treatment system.

[0033] After cleaning the chromium-containing waste liquid tanks stored at the plant using this technical solution, the hexavalent chromium content in the treated solution is less than 0.005 mg / L, which meets the hexavalent chromium emission standards implemented in this region in accordance with GB13456-2012.

[0034] Example 2

[0035] A steel company's scrapped chromium plating solution was stored in a 1-cubic-meter tonne container and transported to a third party for disposal. The hexavalent chromium content in the remaining solution in the tonne container ranged from 86,000 to 122,000 mg / L. There was no sludge residue in the tonne container. This technical solution was used to clean the tonne container.

[0036] S1. The sulfuric acid dosing pump 11 in reaction tank 2 is controlled by pH meter 8. When the pH value is greater than 1.90, the sulfuric acid dosing pump 11 is turned on and when the pH value is less than 1.70, the sulfuric acid dosing pump 11 is turned off.

[0037] S2. The sodium metabisulfite dosing pump 10 in reaction vessel 2 is controlled by ORP detector 7. When the ORP value is greater than 420mV, the sodium metabisulfite dosing pump 10 is turned on and when the ORP value is less than 420mV, the sodium metabisulfite dosing pump 10 is turned off.

[0038] S3. After both the sulfuric acid dosing pump 11 and the sodium metabisulfite dosing pump 10 have stopped dosing for 60 minutes, turn on the online hexavalent chromium detector 6 containing solution pretreatment to detect the hexavalent chromium content.

[0039] S4. After the hexavalent chromium content test meets the standard, replace the chromium-containing waste liquid storage container 1. After cleaning 5 ton drums according to the above procedure, the hexavalent chromium test result is 0.033 mg / L.

[0040] S5. Start the sodium hydroxide dosing pump 12 and stop it when the pH meter reading is greater than 8.5.

[0041] S6. After adjusting the pH in the reaction tank, react for 60 minutes, then open the drain valve 15 of the reaction tank to discharge the solution into the wastewater treatment system.

[0042] After cleaning the chromium-containing waste liquid tanks stored in the plant using this technical solution, the hexavalent chromium content in the treated solution is less than 0.05 mg / L, which meets the hexavalent chromium emission standard implemented in this region in accordance with GB13456-2012.

[0043] The working process of this invention is as follows:

[0044] S1. The system is controlled by a PLC. Industrial water valve 9 is opened to inject industrial water to a certain level into reaction tank 2. The pump 13 from the reaction tank to the chromium-containing waste liquid storage container is turned on, and the solution is injected into the chromium-containing waste liquid storage container 1 through the solution spray pipe 18. At the same time, the pump 14 from the chromium-containing waste liquid storage container to the reaction tank is turned on to pump the solution back to reaction tank 2. Sulfuric acid and sodium metabisulfite solution are added to reaction tank 2. After repeated cleaning for a certain period of time, the solution is finally pumped into reaction tank 2. The hexavalent chromium online detector 6 is started to detect the hexavalent chromium content. If the hexavalent chromium content meets the discharge requirements, the chromium-containing waste liquid storage container 1 is replaced. After cleaning several chromium-containing waste liquid storage containers 1, the sodium hydroxide dosing pump is turned on to adjust the pH value of the solution to alkaline. After reacting for a period of time, the reaction tank drain valve 15 is opened to discharge the solution into the wastewater treatment system.

[0045] S2. The pump 13 from the reaction tank to the chromium-containing waste liquid storage container and the pump 14 from the chromium-containing waste liquid storage container to the reaction tank are turned on at the same time. If the liquid level in the chromium-containing waste liquid storage container 1 reaches the high level of the high / low level switch 17 of the chromium-containing waste liquid storage container, the pump 13 from the reaction tank to the chromium-containing waste liquid storage container is turned off. When the liquid level drops to the low level, the pump 13 from the reaction tank to the chromium-containing waste liquid storage container is turned on.

[0046] S3. The sulfuric acid dosing pump 11 on the sulfuric acid storage tank 4 is controlled by pH meter 8 in reaction tank 2. When the pH value is set to be greater than a certain value of 1.80 to 2.10 in PLC, the sulfuric acid dosing pump 11 is turned on and when the pH value is set to be less than a certain value of 1.60 to 1.80, the sulfuric acid dosing pump 11 is turned off.

[0047] S4. The sodium metabisulfite dosing pump 10 on the sodium metabisulfite solution storage tank 3 is controlled by the ORP detector 7 in the reaction tank 2. The PLC is set to start when the ORP value is greater than a certain value of 300-450mV, and to stop when it is less than that value.

[0048] S5. When both the sulfuric acid dosing pump 11 and the sodium metabisulfite dosing pump 10 have stopped dosing for 30-60 minutes, turn on the online hexavalent chromium detector 6 containing solution pretreatment to detect the hexavalent chromium content.

[0049] S6. After the hexavalent chromium content test meets the standard, replace the chromium-containing waste liquid storage container 1.

[0050] S7. After cleaning 5 to 10 chromium-containing waste liquid storage containers 1, turn on the sodium hydroxide dosing pump 12 and stop the sodium hydroxide dosing pump 12 on the sodium hydroxide solution storage tank 5 when the pH meter 8 detects a value greater than 7.0 to 9.0.

[0051] S8. After adjusting the pH in the reaction tank, react for 30-60 minutes, then open the drain valve 15 of the reaction tank to discharge the solution into the wastewater treatment system.

[0052] All electrical components mentioned in this article are real-world electrical components.

[0053] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention are also within the protection scope of the present invention.

Claims

1. A cleaning process for chromium-containing waste liquid storage containers, characterized in that, Includes the following steps: S1. The system is controlled by PLC. The industrial water valve (9) is opened to inject a certain level of industrial water into the reaction tank (2). The pump (13) from the reaction tank to the chromium waste liquid storage container is opened. The solution is injected into the chromium waste liquid storage container (1) through the solution spray pipe (18). At the same time, the pump (14) from the chromium waste liquid storage container to the reaction tank is opened to pump the solution back to the reaction tank (2). Sulfuric acid and sodium metabisulfite solution are added to the reaction tank (2). After repeated cleaning for a certain period of time, the solution is finally pumped into the reaction tank (2). The hexavalent chromium online detector (6) is started to detect the hexavalent chromium content. If the hexavalent chromium content meets the discharge requirements, the chromium waste liquid storage container (1) is replaced. After cleaning several chromium waste liquid storage containers (1), the sodium hydroxide dosing pump is turned on to adjust the pH value of the solution to alkaline. After reacting for a period of time, the reaction tank drain valve (15) is opened to discharge the solution into the wastewater treatment system. S2. The pump (13) from the reaction tank to the chromium-containing waste liquid storage container and the pump (14) from the chromium-containing waste liquid storage container to the reaction tank are turned on at the same time. If the liquid level in the chromium-containing waste liquid storage container (1) reaches the high level of the high and low liquid level switch (17) of the chromium-containing waste liquid storage container, the pump (13) from the reaction tank to the chromium-containing waste liquid storage container is turned off. When the liquid level drops to the low level, the pump (13) from the reaction tank to the chromium-containing waste liquid storage container is turned on. S3. The sulfuric acid dosing pump (11) on the sulfuric acid storage tank (4) is started and stopped by pH meter (8) inside the reaction tank (2); S4. The sodium metabisulfite dosing pump (10) on the sodium metabisulfite solution storage tank (3) is started and stopped by the ORP detector (7) inside the reaction tank (2); S5. When both the sulfuric acid dosing pump (11) and the sodium metabisulfite dosing pump (10) stop dosing for 30-60 minutes, turn on the online hexavalent chromium detector (6) containing solution pretreatment to detect the hexavalent chromium content. S6. After the hexavalent chromium content test meets the standard, replace the chromium-containing waste liquid storage container (1); S7. After cleaning 5 to 10 chromium-containing waste liquid storage containers (1), turn on the sodium hydroxide dosing pump (12) and stop the sodium hydroxide dosing pump (12) on the sodium hydroxide solution storage tank (5) when the pH meter (8) detects a value greater than 7.0 to 9.

0. S8. After adjusting the pH in the reaction tank, react for 30-60 minutes, then open the drain valve (15) of the reaction tank to discharge the solution into the wastewater treatment system.

2. The cleaning process for a chromium-containing waste liquid storage container according to claim 1, characterized in that, In step S3, the sulfuric acid dosing pump (11) is turned on when the pH value is set to be greater than a certain value of 1.80 to 2.10 in the PLC, and the sulfuric acid dosing pump (11) is turned off when the pH value is set to be less than a certain value of 1.60 to 1.

80.

3. The cleaning process for a chromium-containing waste liquid storage container according to claim 1, characterized in that, In step S4, the sodium metabisulfite dosing pump (10) is turned on when the ORP value is greater than a certain value of 300-450mV in the PLC, and is turned off when the ORP value is less than that value.

4. The cleaning process for a chromium-containing waste liquid storage container according to claim 1, characterized in that, The reaction vessel (2) is equipped with a reaction vessel level gauge (16).

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