A device for removing arsenic from waste acid suitable for large sulfuric acid systems

Abstract

This utility model discloses a waste acid arsenic removal device suitable for large-scale sulfuric acid systems, comprising a NaHS storage tank, a NaHS high-level tank, a waste acid raw material storage tank, a sulfidation reaction tank, a sulfidation thickener, a filtrate tank, a purging tower, a NaOH circulation tank, and a plate and frame filter press. The outlet of the NaHS storage tank is connected to the NaHS high-level tank, and the inlet of the NaHS storage tank is connected to a NaHS solution addition pipe. The NaHS high-level tank is sequentially connected to the sulfidation reaction tank, the sulfidation thickener, and the filtrate tank. The outlet of the waste acid raw material storage tank is connected to the sulfidation reaction tank, and the inlet of the waste acid raw material storage tank is connected to a waste acid discharge pipe from the purification system. The gas outlets of the sulfidation reaction tank and the sulfidation thickener are connected to the purging tower via pipelines. The purging tower is circulated and connected to the NaOH circulation tank. A discharge port is provided at the top of the purging tower, and the bottom sedimentation end of the sulfidation thickener is connected to the plate and frame filter press via pipelines. This utility model utilizes the arsenic removal effect of sodium hydrosulfide to complete the arsenic removal process. It is simple to operate and applicable even with large fluctuations in arsenic content, significantly improving the arsenic removal efficiency of waste acid.

Description

Technical Field

[0001] This utility model relates to the field of waste acid and wastewater treatment technology, and in particular to a waste acid arsenic removal device suitable for large-scale sulfuric acid systems. Background Technology

[0002] In the sulfuric acid production process, the purification and washing liquid contains soluble impurities such as arsenic, fluorine, and chlorine, with arsenic content generally being high. It also contains dissolved sulfur trioxide and some sulfur dioxide, resulting in generally high acidity. Therefore, this portion of the purification and washing liquid that is periodically discharged is called waste acid. The treatment process for waste acid involves removing heavy metal ions such as arsenic, copper, lead, zinc, and cadmium, especially arsenic. Arsenic in waste acid exists in the form of arsenic acid and arsenous acid, with concentrations ranging from several thousand milligrams per liter. Most arsenic compounds are highly toxic and can harm the surrounding environment and human health. Traditional iron-salt neutralization methods cannot treat high concentrations of arsenic to meet environmental emission standards. Therefore, in the waste acid treatment process, a device must be installed before the iron-salt neutralization process to purify and remove arsenic from the waste acid, and this device needs to be able to handle situations with large fluctuations in arsenic content. Utility Model Content

[0003] To solve the above-mentioned technical problems, this utility model designs a waste acid arsenic removal device suitable for large-scale sulfuric acid systems. It can utilize the arsenic removal effect of sodium hydrosulfide in conjunction with the device provided by this utility model to complete the arsenic removal process. It is simple to operate and can also be applied to situations where the arsenic content fluctuates greatly, which can greatly improve the arsenic removal effect of waste acid.

[0004] The present invention adopts the following technical solution: An arsenic removal device for waste acid in a large-scale sulfuric acid system includes a NaHS storage tank, a NaHS high-level tank, a waste acid raw material storage tank, a sulfidation reaction tank, a sulfidation thickener, a filtrate tank, a purging tower, a NaOH circulation tank, and a plate and frame filter press. The outlet of the NaHS storage tank is connected to the NaHS high-level tank, and the inlet of the NaHS storage tank is connected to a NaHS solution addition pipe. The NaHS high-level tank is sequentially connected to the sulfidation reaction tank, the sulfidation thickener, and the filtrate tank. The outlet of the waste acid raw material storage tank is connected to the sulfidation reaction tank, and the inlet of the waste acid raw material storage tank is connected to a waste acid discharge pipe from the purification system. The gas outlets of the sulfidation reaction tank and the sulfidation thickener are connected to the purging tower via pipelines. The purging tower is circulated and connected to the NaOH circulation tank. An outlet is provided at the top of the purging tower, and the sedimentation end at the bottom of the sulfidation thickener is connected to the plate and frame filter press via pipelines.

[0005] Preferably, the vulcanization reaction tank includes a primary vulcanization reaction tank and a secondary vulcanization reaction tank, the vulcanization thickener includes a primary vulcanization thickener and a secondary vulcanization thickener, and the filtrate tank includes a primary filtrate tank and a secondary filtrate tank. The primary vulcanization reaction tank, the primary vulcanization thickener, and the primary filtrate tank are connected in sequence, and the secondary vulcanization reaction tank, the secondary vulcanization thickener, and the secondary filtrate tank are connected in sequence. The primary vulcanization reaction tank is connected to the waste acid stock solution storage tank and the sodium hydrosulfide high-level tank, and the secondary vulcanization reaction tank is connected to the primary filtrate tank.

[0006] Preferably, the NaOH circulation tank is connected to a water supply pipe and a NaOH addition tank.

[0007] Preferably, an H2S fan is installed on the gas outlet end of the sulfurization reaction tank and the sulfurization thickener, and on the pipeline connecting the purging tower.

[0008] Preferably, the NaHS solution is added automatically, and the addition is automatically controlled by the oxidation-reduction potential (ORP) values ​​at the outlets of the two sulfidation reaction tanks. The range of the ORP values ​​at the outlets of the two sulfidation reaction tanks corresponds to the ORP values ​​corresponding to the titration results of the effluent from the two-stage sulfidation reaction tanks titrated with NaHS solution. The titration results ensure that the first-stage filtrate titration produces residue while the second-stage filtrate titration is residue-free.

[0009] Preferably, the filtrate output end of the plate and frame filter press is connected to the filtrate tank via a pipeline.

[0010] Preferably, the NaHS storage tank is embedded in the ground, with the top of the tank flush with the ground, and a liquid level sensor is installed inside the NaHS storage tank.

[0011] Preferably, the vulcanization reaction tank and the top of the vulcanization thickener are equipped with a negative pressure pipe to absorb the escaping H2S gas.

[0012] Preferably, the NaHS high-level tank is located at the highest point of the entire device and is connected to the vulcanization reaction tank via pipes and an automatic addition valve.

[0013] The beneficial effects of this utility model are: This utility model utilizes the arsenic removal effect of sodium hydrosulfide in conjunction with the device provided by this utility model to complete the arsenic removal process. Moreover, this utility model is simple to operate and can be applied even when the arsenic content fluctuates greatly, which can greatly improve the arsenic removal effect of waste acid. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of this utility model; In the diagram: 1. NaHS storage tank, 2. NaHS high-level tank, 3. Waste acid raw material storage tank, 4. Primary sulfidation reaction tank, 5. Primary sulfidation thickener, 6. Primary filtrate tank, 7. Secondary sulfidation reaction tank, 8. Secondary sulfidation thickener, 9. Secondary filtrate tank, 10. H2S fan, 11. Pest control tower, 12. NaOH circulation tank, 13. Plate and frame filter press. Detailed Implementation

[0015] The technical solution of this utility model will be further described in detail below through specific embodiments and with reference to the accompanying drawings: Example: Figure 1 As shown, a waste acid arsenic removal device suitable for large-scale sulfuric acid systems includes a NaHS storage tank 1, a NaHS high-level tank 2, a waste acid raw material storage tank 3, a primary sulfidation reaction tank 4, a primary sulfidation thickener 5, a primary filtrate tank 6, a secondary sulfidation reaction tank 7, a secondary sulfidation thickener 8, a secondary filtrate tank 9, an H2S fan 10, a scavenging tower 11, a NaOH circulation tank 12, and a plate and frame filter press 13.

[0016] The outlet of the NaHS storage tank is connected to the high-level NaHS tank, and the inlet of the NaHS storage tank is connected to the NaHS solution addition pipe. The high-level NaHS tank is sequentially connected to the primary sulfidation reaction tank 4, the primary sulfidation thickener 5, the primary filtrate tank 6, the secondary sulfidation reaction tank 7, the secondary sulfidation thickener 8, and the secondary filtrate tank 9. The outlet of the waste acid raw material storage tank is connected to the sulfidation reaction tank, and the inlet of the waste acid raw material storage tank is connected to the waste acid discharge pipe from the purification system. The gas outlets of the primary sulfidation reaction tank 4, the primary sulfidation thickener 5, the secondary sulfidation reaction tank 7, and the secondary sulfidation thickener 8 are connected to the purifying tower via pipelines and the H2S fan 10. The purifying tower is circulated and connected to the NaOH circulation tank. An outlet is set at the top of the purifying tower. The NaOH circulation tank is connected to the water supply pipe and the NaOH addition tank. The bottom sedimentation ends of the primary sulfidation thickener 5 and the secondary sulfidation thickener 8 are connected to the plate and frame filter press via pipelines. The filtrate output end of the plate and frame filter press is connected to the primary filtrate tank 6 and the secondary filtrate tank 9 via pipelines.

[0017] The reaction involves using approximately 30% liquid NaHS to react with waste acid from a sulfuric acid purification system. This waste acid contains heavy metal ions such as arsenic, copper, lead, zinc, and cadmium. The arsenic content varies considerably depending on the composition of the smelted ore powder, ranging from 200 mg / L to 30,000 mg / L. The reaction principle is as follows: 2NaHS + H2SO4== 2H2S↑+ Na2SO4 Cu 2+ +H₂S→CuS↓+2H + 2HAsO2+ 3H2S == As2S3↓+ 4H20 Waste acid from the waste acid stock solution storage tank is pumped to the primary sulfidation reaction tank using a waste acid stock solution pump. In the primary sulfidation reaction tank, under acidic conditions, NaHS solution from the high-level tank reacts with the waste acid to generate As₂S₃ precipitate. This precipitate then flows from the top into the primary sulfidation thickener via a chute for settling. The supernatant flows to the primary filtrate tank, while the bottom sludge is pumped to a plate and frame filter press for pressing. The pressed filter cake is then dried. The waste acid in the primary filtrate tank is then sent to the secondary sulfidation reaction tank for a secondary reaction. The supernatant flows from the top into the secondary sulfidation thickener for settling. The supernatant flows to the secondary filtrate tank and is then sent to the wastewater treatment process for neutralization using a lime-ferrous sulfate method. The bottom sludge is sent to the pressing unit. After treatment by sulfidation, the arsenic content in the waste acid is between 0-30 mg / L, ensuring an arsenic removal rate of over 99.9%. The sulfidated liquid from the waste acid treatment process is first neutralized with limestone slurry in a gypsum reaction tank to remove most of the sulfuric acid, producing gypsum. The supernatant (post-gypsum liquid) with a pH of 1-3 is then subjected to two stages of neutralization and aeration oxidation to further remove acid, arsenic, and heavy metal ions, resulting in reclaimed water with a pH of 7-9, which is then recycled into the reclaimed water system, reducing the arsenic content in the wastewater to below 0.5 mg / L.

[0018] Multi-stage sulfidation reaction tanks, sulfidation thickeners, and filtrate tanks can improve the production efficiency of arsenic removal from waste acid and ensure the effectiveness of arsenic removal treatment through sulfidation.

[0019] Furthermore, in the waste acid process, NaHS solution is added to the primary and secondary sulfidation reaction tanks via an automatically regulating pneumatic valve. The addition amount is automatically controlled based on the oxidation-reduction potential (ORP) values ​​at the outlets of the two sulfidation reaction tanks. The optimal millivolt setting for the ORP is determined by titrating the effluent from both sulfidation reaction tanks with NaHS solution. The millivolt setting of the ORP meter is then adjusted based on the titration results. The titration result must show residue in the primary filtrate and no residue in the secondary filtrate to ensure the effective sulfidation treatment of the waste acid. When the primary filtrate is free of residue: if the liquid levels in subsequent tanks are low, the outlet valve of the primary reaction tank waste acid stock solution pump is opened wider to increase the amount of waste acid stock solution added. If the primary reaction tank stock solution addition is already at its maximum, or if the liquid levels in subsequent tanks are high, the primary ORP setting is increased to decrease the primary NaHS addition amount. When the secondary filtrate shows residue: the secondary ORP setting is first decreased to increase the secondary NaHS addition amount. If the secondary ORP is already set low, then lower the primary ORP setting while ensuring there is residue in the primary filtrate to increase the amount of primary NaHS added. When the primary filtrate level is low, adjustment can also be made by reducing the amount of waste acid added to the secondary reaction tank. The primary and secondary ORP settings are 0-200mV (normal operation is automatic; in special circumstances, manual adjustment is required; the increment or decrement of the ORP millivolt value should not be too large, at a rate of 5 millivolts). Control equipment includes: an ORP value display, an ORP analyzer, an automatic arsenic removal agent addition valve (pneumatic valve), and a waste acid DCS control system.

[0020] Furthermore, the sodium hydrosulfide storage tank is embedded underground, with its top flush with the ground, and is equipped with a level sensor to monitor the remaining amount. The sodium hydrosulfide high-level tank is located at the highest point and is connected to the sulfidation reaction tank via pipes and an automatic addition valve. The raw material storage tank is connected to the sulfidation reaction tank via pipes. The tops of the sulfidation reaction tank, sulfidation thickener, and filtrate tank are equipped with negative pressure pipes to absorb the escaping H2S gas. An H2S blower sends the escaping H2S gas to the scavenging tower via pipes. The scavenging tower absorbs the H2S gas through sprayed NaOH solution. A NaOH circulation tank sends NaOH to the scavenging tower via a pump. The scavenging tower is connected to the sodium hydroxide circulation tank for reuse.

[0021] The above-described embodiments are merely preferred solutions of this utility model and are not intended to limit this utility model in any way. Other variations and modifications are possible without departing from the technical solutions described in the claims.

Claims

1. A waste acid arsenic removal device suitable for large-scale sulfuric acid systems, characterized in that, It includes a NaHS storage tank, a NaHS high-level tank, a waste acid stock solution storage tank, a sulfidation reaction tank, a sulfidation thickener, a filtrate tank, a purging tower, a NaOH circulation tank, and a plate and frame filter press. The outlet of the NaHS storage tank is connected to the NaHS high-level tank, and the inlet of the NaHS storage tank is connected to the NaHS solution addition pipe. The NaHS high-level tank is sequentially connected to the sulfidation reaction tank, the sulfidation thickener, and the filtrate tank. The outlet of the waste acid stock solution storage tank is connected to the sulfidation reaction tank, and the inlet of the waste acid stock solution storage tank is connected to the waste acid discharge pipe from the purification system. The gas outlets of the sulfidation reaction tank and the sulfidation thickener are connected to the purging tower through pipelines. The purging tower is circulated and connected to the NaOH circulation tank. An outlet is set at the top of the purging tower, and the sedimentation end at the bottom of the sulfidation thickener is connected to the plate and frame filter press through pipelines.

2. The arsenic removal device for waste acid in a large-scale sulfuric acid system according to claim 1, characterized in that, The vulcanization reaction tank includes a primary vulcanization reaction tank and a secondary vulcanization reaction tank; the vulcanization thickener includes a primary vulcanization thickener and a secondary vulcanization thickener; the filtrate tank includes a primary filtrate tank and a secondary filtrate tank. The primary vulcanization reaction tank, the primary vulcanization thickener, and the primary filtrate tank are connected in sequence, as are the secondary vulcanization reaction tank, the secondary vulcanization thickener, and the secondary filtrate tank. The primary vulcanization reaction tank is connected to the waste acid stock solution storage tank and the sodium hydrosulfide high-level tank, and the secondary vulcanization reaction tank is connected to the primary filtrate tank.

3. The arsenic removal device for waste acid in a large-scale sulfuric acid system according to claim 1, characterized in that, The NaOH circulation tank is connected to the water supply pipe and the NaOH addition tank.

4. The arsenic removal device for waste acid in a large-scale sulfuric acid system according to claim 1, characterized in that, An H2S fan is installed on the gas outlet end of the sulfurization reaction tank and the sulfurization thickener, and on the pipeline connecting the purging tower.

5. The arsenic removal device for waste acid in a large-scale sulfuric acid system according to claim 1, characterized in that, The filtrate output end of the plate and frame filter press is connected to the filtrate tank via a pipeline.

6. The arsenic removal device for waste acid in a large-scale sulfuric acid system according to claim 1, characterized in that, The NaHS storage tank is embedded in the ground, with the top of the tank flush with the ground. A liquid level sensor is installed inside the NaHS storage tank.

7. The arsenic removal device for waste acid in a large-scale sulfuric acid system according to claim 1, characterized in that, The vulcanization reaction tank has a negative pressure pipe at the top of the vulcanization thickener to absorb the escaping H2S gas.

8. The arsenic removal device for waste acid in a large-scale sulfuric acid system according to claim 1, characterized in that, The NaHS high-level tank is located at the highest point of the entire device and is connected to the vulcanization reaction tank via pipes and an automatic addition valve.

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