Spent acid sulfidation treatment method

Abstract

This invention belongs to the field of smelting, specifically relating to a method for treating smelting waste acid by sulfidation, including the following steps: (1) Sulfidation: After mixing the waste acid and sulfiding agent, the mixture enters a pipeline reactor for sulfidation reaction. The reaction temperature is 30-50℃, and the residence time in the pipeline reactor is 3-10 min; (2) Hydrogen sulfide desorption: After the sulfidation reaction, the reaction liquid is desorbed under negative pressure to obtain sulfidated liquid and desorbed gas; (3) Hydrogen sulfide absorption: First, the waste acid is used to absorb the hydrogen sulfide in the desorbed gas, and then liquid alkali is used to absorb the residual hydrogen sulfide. In the above scheme, the sulfidation reaction is carried out in a pipeline reactor, which not only ensures sufficient contact and thorough reaction between the waste acid and the sulfiding agent, but also avoids the defect of hydrogen sulfide escaping. After the reaction, the hydrogen sulfide in the liquid is released under negative pressure, and most of the hydrogen sulfide is absorbed by the waste acid. The residual waste acid is absorbed by liquid alkali, which greatly reduces the consumption of liquid alkali and reduces production costs.

Description

Technical Field

[0001] This invention belongs to the field of metallurgy, and specifically relates to a method for treating sulfidation of smelting waste acid. Background Technology

[0002] Currently, copper smelting enterprises treat purified waste acid by adding the waste acid and sulfiding agent from the bottom of the reaction tank. Under the stirring action of a stirring paddle, the two are mixed and undergo a sulfidation reaction, thereby removing most heavy metals such as copper and arsenic from the waste acid. After the sulfidation reaction, the liquid overflows into a flow channel and is then transported to a thickener for solid-liquid separation, achieving the goal of removing heavy metals such as copper and arsenic.

[0003] Traditional vulcanization processes use reaction tanks with gaps in the agitator and observation ports. Excess hydrogen sulfide generated during the vulcanization reaction can easily escape from these gaps, polluting the atmosphere in the vulcanization work area and endangering the health of the workers.

[0004] In traditional reaction tank stirring sulfidation process, the waste acid and sulfiding agent cannot be fully mixed and reacted in the reaction tank. The arsenic content in the arsenic filtrate after the thickener overflows is still maintained at 20-50 mg / L, which cannot achieve deep arsenic removal.

[0005] Hydrogen sulfide gas that escapes from equipment such as reaction tanks, thickeners, and filtrate tanks during the sulfidation reaction is absorbed into the scavenging tower by a scavenging fan under negative pressure. Since a large amount of hydrogen sulfide is produced during the reaction, a large amount of liquid alkali is required for absorption. The exhaust gas can only be discharged after the hydrogen sulfide meets the standards, and the cost of using liquid alkali is high. Summary of the Invention

[0006] The purpose of this invention is to provide a method for treating polluted acid by sulfurization, which optimizes the sulfurization reaction site and guides the hydrogen sulfide direction under negative pressure to prevent hydrogen sulfide from escaping.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for treating waste acid by sulfurization, comprising the following steps:

[0008] (1) Sulfurization: After the waste acid and sulfiding agent are mixed, they enter the pipeline reactor for sulfidation reaction. The reaction temperature is 30-50℃ and the residence time in the pipeline reactor is 3-10 min.

[0009] (2) Hydrogen sulfide desorption: After the reaction liquid after the sulfidation reaction is desorbed under negative pressure, the sulfidation liquid and the desorbed gas are obtained;

[0010] (3) Hydrogen sulfide absorption: First, use dirty acid to absorb the hydrogen sulfide in the desorbed gas, and then use liquid alkali to absorb the residual hydrogen sulfide.

[0011] Specifically, in step (1), the sulfiding agent is sodium hydrosulfide with a mass concentration of 5-20%; in order to make the sulfidation reaction more complete, the sulfiding agent is in excess in the mixture of dirty acid and sulfiding agent.

[0012] In step (2), after the hydrogen sulfide is desorbed under negative pressure, the sulfided liquid enters the thickener for solid-liquid separation to remove the sulfide precipitate. To further reduce the emission of hydrogen sulfide, the process of the sulfided liquid entering the thickener and the thickener are also sealed and a negative pressure environment is provided. In step (3), the waste acid that has absorbed hydrogen sulfide is returned to step (1) for recycling.

[0013] In the above scheme, the sulfidation reaction is carried out in a pipeline reactor, which not only ensures sufficient contact and thorough reaction between the waste acid and the sulfiding agent, but also prevents the generated hydrogen sulfide from escaping from the reaction vessel and causing pollution. After the reaction, the hydrogen sulfide in the liquid is released under negative pressure, and most of the hydrogen sulfide is absorbed by the waste acid. The remaining waste acid is absorbed by liquid alkali, which greatly reduces the consumption of liquid alkali and lowers production costs. The entire scheme is simple to operate, requires minimal equipment investment, and has virtually no hydrogen sulfide leakage throughout the process, making it environmentally friendly. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the waste acid treatment system in a specific embodiment of the present invention. Detailed Implementation

[0015] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings.

[0016] A method for treating polluted acid by sulfurization includes the following steps:

[0017] Step 1: The waste acid and the sulfurizing agent sodium hydrosulfide are both pumped into the mixer 10 by a centrifugal pump for mixing, and then enter the pipeline reactor 20 for efficient and complete sulfurization reaction.

[0018] Step 2: After the sulfidation reaction, the liquid enters the sulfidation liquid desorption tower 30. After the hydrogen sulfide is removed under negative pressure, the sulfidation liquid enters the thickener through a flow channel for solid-liquid separation to remove heavy metals such as copper and arsenic. The hydrogen sulfide collected under negative pressure in the flow channel and thickener is then fed into the absorption tower 40.

[0019] Step 3: The removed hydrogen sulfide gas enters the absorption tower 40 through the outlet 32 ​​at the top of the desorption tower 30, and comes into contact with the sprayed waste acid. Most of the hydrogen sulfide is absorbed by the waste acid. The gas after being absorbed by the waste acid enters the purging tower 60, where the remaining hydrogen sulfide is absorbed by liquid alkali, and the tail gas is discharged in compliance with standards.

[0020] The above-mentioned acid sulfidation can be carried out in the following treatment system:

[0021] A waste acid sulfidation treatment system includes a pipeline reactor 20 whose reaction liquid inlet 21 is connected to a waste acid storage tank A and a sulfidizing agent storage tank B, and whose reaction liquid outlet 22 is connected to the inlet pipe 31 of a nozzle inside a desorption tower 30. The top outlet 32 ​​of the desorption tower 30 is connected to the air inlet 41 at the bottom of an absorption tower 40. The absorption tower 40 is equipped with a spray unit connected to the waste acid storage tank A, and the top exhaust port 42 of the absorption tower 40 is connected to the air supply pipe 61 of a pest control tower 60. In actual production, the pipeline reactor uses a DN150 chemical-grade UPVC pipe, with a 4F expansion joint installed in the middle of the pipe.

[0022] The residence time in the pipeline reactor mentioned above is 3–10 minutes, which is the time from when the mixture of waste acid and sulfurizing agent enters the reaction liquid inlet 21 of the pipeline reactor 20 until the reaction liquid flows out of the reaction liquid outlet 22 of the pipeline reactor 20. In simpler terms, the residence time is the time from when the reaction liquid begins to enter the pipeline reactor 20 until when the reaction liquid begins to flow out of the pipeline reactor 20.

[0023] A mixer 10 is installed upstream of the pipeline reactor 20. The inlet 11 of the mixer 10 is connected to the waste acid storage tank A and the sulfurizing agent storage tank B, and the outlet 12 is connected to the reaction liquid inlet 21 of the pipeline reactor 20. A pressure gauge is installed on the waste acid pipeline inlet of the mixer 10, and a check valve is installed on the sulfurizing agent pipeline. The waste acid delivery flow rate is controlled by a flow meter + automatic valve. The amount of sulfurizing agent added is controlled by a flow meter + automatic valve + ORP electrode. The sulfurizing agent is added stably and continuously at a certain flow rate. The automatic valve provides micro-control to adjust the amount added, and the ORP electrode monitors the degree of sulfurization reaction.

[0024] The negative pressure port 33 at the lower part of the desorption tower 30 and the exhaust port 42 at the top of the absorption tower 40 are both connected to the negative pressure fan 50. The negative pressure fan 50 is connected downstream to the air supply pipe 61 of the pest control tower 60. The resin packing inside the desorption tower 30 and the absorption tower 40 is made of vinyl resin. The spray pipes inside the towers have 2cm round holes on both sides and at the bottom, with spray liquid evenly distributed at 10cm intervals. The packing is ∅80PP Heil rings, and the packing layer height is 1.5m.

[0025] The lower part of the absorption tower 40 is provided with an acid discharge port 43, which is connected to the waste acid storage tank A or the liquid inlet 11 of the mixer 10. The gas outlet end of the gas supply pipe 61 of the decontamination tower 60 containing liquid alkali is submerged below the liquid alkali surface; the discharge port 34 at the lower part of the desorption tower 30 is connected to the thickener via a flow channel; the thickener and subsequent equipment for storing filtrate collect the escaping gas and then introduce it into the desorption tower 30; a negative pressure valve is provided between the negative pressure port 33 in the lower part of the desorption tower 30 and the negative pressure fan 50; finally, the gas discharged from the decontamination tower 60 meets the emission standards and can be directly discharged into the atmosphere.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1. The pipeline reactor sulfidation reaction system is completely closed, with no hydrogen sulfide gas escaping from the site, thus improving the operating environment for on-site employees.

[0028] 2. By adding hydrogen sulfide in excess and providing sufficient residence time in the pipeline reactor, the reaction proceeds efficiently and fully, achieving deep removal of heavy metals such as copper and arsenic from the waste acid, with the arsenic content in the arsenic filtrate being less than 5 mg / L.

[0029] 3. The desulfurizer addition control method has been changed from automatic valve addition based on ORP fluctuations to automatic valve addition based on flow rate fluctuations, with the reaction degree monitored on-site by the ORP electrode. The control method is more optimized, achieving continuous and stable addition of desulfurizer.

[0030] 4. The hydrogen sulfide collected under negative pressure in the filtrate desorption tower, filtrate tank, and thickener reacts again with the sulfided liquid and is desorbed, then enters the hydrogen sulfide absorption tower where it is fully absorbed by the waste acid. This results in a lower hydrogen sulfide content in the inlet gas of the purging tower compared to the sulfidation reaction in the reaction tank, reducing the amount of liquid alkali used. Practical statistics show that the waste acid in the 40 stages of the absorption tower achieves an absorption rate of over 80% for hydrogen sulfide in the incoming gas.

Claims

1. A method for treating waste acid by sulfurization, comprising the following steps: (1) Sulfurization: After the waste acid and sulfiding agent are mixed, they enter the pipeline reactor for sulfidation reaction. The reaction temperature is 30-50℃ and the residence time in the pipeline reactor is 3-10 min. (2) Hydrogen sulfide desorption: After the reaction liquid after the sulfidation reaction is desorbed under negative pressure, the sulfidation liquid and the desorbed gas are obtained; (3) Hydrogen sulfide absorption: First, use dirty acid to absorb the hydrogen sulfide in the desorbed gas, and then use liquid alkali to absorb the residual hydrogen sulfide.

2. The spent acid sulfidation treatment method of claim 1, wherein: In step (1), the sulfiding agent is sodium hydrosulfide with a mass concentration of 5-20%.

3. The spent acid sulfidation treatment method of claim 1, wherein: In step (1), the sulfurizing agent is in excess in the mixture of dirty acid and sulfurizing agent.

4. The method for treating waste acid by sulfurization according to claim 1, characterized in that: In step (2), after the hydrogen sulfide is desorbed under negative pressure, the sulfided liquid enters a thickener for solid-liquid separation to remove the sulfided precipitate.

5. The method for treating waste acid by sulfurization according to claim 1, characterized in that: In step (3), the waste acid that has absorbed hydrogen sulfide is returned to step (1) for recycling.

6. The method for treating waste acid by sulfurization according to claim 4, characterized in that: The gas emitted from the thickener and subsequent filtrate storage equipment is collected and then transported to step (3) for processing.

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