Arsenic removal method for purifying waste acid

Abstract

The invention discloses an arsenic removal method for purifying waste acid, and belongs to the technical field of sulfuric acid preparation. The method comprises the following steps: settling wastewater, and carrying out filter pressing on slurry through a first filter press; in the first-stage reaction tank, the waste acid reacts with a desulfurizing agent from a sodium hydrosulfide preparation tank, and after the reaction is completed, the waste acid is sent to a first-stage FBL filter to be filtered; in the second-stage reaction tank, the waste acid reacts with a desulfurizing agent from the sodium hydrosulfide preparation tank, and after the reaction is completed, the waste acid is sent to a second-stage FBL filter to be filtered; the filtrate of the second-stage FBL filter is sent to a dynamic wave scrubber for recycling; a flocculating agent is added into the first-stage FBL filter and the second-stage FBL filter; tail gas of the first-stage reaction tank, the first-stage FBL filter, the second-stage reaction tank, the first-stage FBL filter and the sodium hydrosulfide preparation tank is sent to a spray tower, washing liquid containing sodium hydrosulfide and sodium sulfide in the spray tower is sent to the sodium hydrosulfide preparation tank, and sodium hydrosulfide solids are added into the sodium hydrosulfide preparation tank.

Description

Technical Field

[0001] The invention belongs to the technical field of sulfuric acid preparation, and in particular relates to a dearsenication method for purifying waste acid. Background Art

[0002] A large amount of SO2 flue gas is generated during the smelting process of metal sulfide ores. The SO2 flue gas is usually used to prepare sulfuric acid through the smelting flue gas acid-making process. In the smelting flue gas acid-making process, the flue gas purification process widely uses wet scrubbing flue gas purification technology to purify the SO2 flue gas.

[0003] For example, the patent with application number CN201310124705.X ​​discloses a medium- and low-grade heat energy recovery system in pyrite acid production, including a waste heat boiler, a cyclone dust collector, an electrostatic precipitator, a purification economizer and a purification economizer short-circuit valve, a power wave washing tower, a cooling tower, a first-level electrostatic demister, a second-level electrostatic demister, a drying tower, a converter, a heat exchanger, a conversion economizer and a conversion economizer short-circuit valve, a deaerator, a desalted water tank and a steam drum connected in series in sequence, wherein the water inlet and outlet of the purification economizer are respectively connected to the water outlet of the conversion economizer and the steam drum on the waste heat boiler; the water outlet of the deaerator is connected to the water inlet of the conversion economizer; through the connection between the purification economizer, the conversion economizer and the deaerator, the medium and low-grade heat energy generated by the purification section and the conversion section are simultaneously recovered and utilized.

[0004] A large amount of acidic wastewater will be generated after the furnace gas is treated in the dynamic wave scrubber. The acidic wastewater is usually sent to the dynamic wave scrubber for circulating spraying after the solid matter is removed. For example, the patent with application number CN201621341269.7 discloses a gas purification system for waste acid regeneration, which includes a dynamic wave scrubber, a packing tower, an electrostatic demister, a waste acid sedimentation tank and a dilute acid tank. The dynamic wave scrubber is respectively provided with an air inlet, an air outlet, a water inlet and a drain outlet. The packing tower includes a tower shell, a spray device, a pair of packings, a pair of packing support grids and a liquid distributor. The tower shell is respectively provided with an air inlet, an air outlet, a water inlet, a drain outlet and a sewage outlet. A pair of packings are respectively installed in the tower shell through the packing support grids. The liquid distributor is installed in the tower shell and is located between a pair of packings. The spray device includes a group of water spray pipes, a group of nozzles and a water inlet pipe. One end of the water spray pipe is open and the other end is open. The ends are closed, and a plurality of nozzle mounting holes are opened on the pipe wall of the water spray pipe, a group of nozzles are respectively installed on the holes, a group of water spray pipes are respectively installed in a circular array on the top of the tower shell, and the open ends of a group of water spray pipes are higher than the closed ends, the open ends of the group of water spray pipes are respectively communicated with the water outlets of the water inlet pipe, and the water inlet of the water inlet pipe is communicated with the water inlet of the tower shell; the air outlet of the power wave washing tower is communicated with the air inlet of the tower shell, the air outlet of the tower shell is communicated with the air inlet of the electrostatic precipitator, the drain outlets of the power wave washing tower and the tower shell are respectively communicated with the water inlet of the waste acid sedimentation tank, the drain outlet of the electrostatic precipitator is communicated with the water inlet of the dilute acid tank, the waste acid sedimentation tank is provided with an overflow outlet, and the waste acid sedimentation tank is communicated with the water inlet of the dilute acid tank through an overflow pipe.

[0005] Since SO2 flue gas contains a large amount of harmful impurities, such as arsenic. These harmful impurities are deposited in the circulating washing water during the washing process, and the circulating washing water forms acidic wastewater due to the absorption of SO2 in the flue gas. In order to reduce the damage of harmful ions to the purification process, this part of the acidic wastewater needs to be discharged from the acid production system regularly. Since it contains a large number of harmful impurities, the acidic wastewater cannot be recycled and reused, and direct discharge will cause environmental pollution, so it is necessary to remove the arsenic in it. Summary of the invention

[0006] The main equation of this patent is: 6NaHS+4HAsO2+3H2SO4→2As2S3↓+3Na2SO4+8H2O 3Na2S+2HAsO2+3H2SO4→As2S3↓+3Na2SO4+4H2O 2NaHS+H2SO4→2H2S↑+Na2SO4 H2S+NaOH→NaHS+H2O H2S+2NaOH→Na2S+2H2O H2SO4+2NaOH→Na2SO4+2H2O.

[0007] Among them, sodium hydrosulfide is unstable under acidic conditions and will produce hydrogen sulfide gas. This patent absorbs hydrogen sulfide gas and uses it as a dearsenicizing agent, so the instability in acid is not a disadvantage in this patent. In addition, the purity requirement of sodium hydrosulfide in this patent is not high.

[0008] The solution of this patent is: An embodiment of the present invention provides a method for purifying waste acid and removing arsenic, the method comprising: S1: The wastewater from the power wave scrubber is settled, the clear liquid is sent to the power wave scrubber for reuse, the sludge is filtered through the first filter press 1, and the filtrate is sent to the primary reaction tank 3 as waste acid; S2: In the primary reaction tank 3, the waste acid reacts with the desulfurizing agent from the sodium hydrosulfide preparation tank 17, and the amount of the desulfurizing agent is 0.9-1.1 times the theoretical value based on sodium hydrosulfide. After the reaction is completed, it is sent to the primary FBL filter 5 for filtration. After the filtration is completed, the filtrate is sent to the secondary reaction tank 6; S3: In the secondary reaction tank 6, the waste acid reacts with the desulfurizing agent from the sodium hydrosulfide preparation tank 17, and the amount of the desulfurizing agent is 0.25-0.40 times the theoretical value based on sodium hydrosulfide. After the reaction is completed, it is sent to the secondary FBL filter 8 for filtration; S4: sending the filtrate from the secondary FBL filter 8 to the power wave scrubber for reuse; Adding flocculants to the primary FBL filter 5 and the secondary FBL filter 8, wherein the amount of the flocculants is 0.2-2.0 g / ton of waste acid; The tail gas from the primary reaction tank 3, the primary FBL filter 5, the secondary reaction tank 6, the primary FBL filter 5 and the sodium hydrosulfide configuration tank 17 is sent to the spray tower 16, in which the sodium hydroxide solution is used for spraying, and the washing liquid containing sodium hydrosulfide and sodium sulfide in the spray tower 16 is sent to the sodium hydrosulfide configuration tank 17, and sodium hydrosulfide solid is added to the sodium hydrosulfide configuration tank 17.

[0009] Further, in step S2, the reaction liquid is first sent to the primary mixer 4 to mix with the flocculant, and then sent to the primary FBL filter 5 for filtration; in step S3, the reaction liquid is first sent to the secondary mixer 7 to mix with the flocculant, and then sent to the secondary FBL filter 8 for filtration.

[0010] Furthermore, the arsenic removal method for purifying waste acid provided by the present invention also includes: S5: collecting the filter residues from the primary FBL filter 5 and the secondary FBL filter 8, and then filtering the filter residues through the second filter press 12, and the filtrate is sent to the power wave scrubber for reuse.

[0011] Among them, the filtrate of the second filter press 12 in the embodiment of the present invention is output to the second filtrate tank 13, the filtrate of the secondary FBL filter 8 and the filtrate of the second filtrate tank 13 are collected by the clear acid storage tank 9 and then sent to the dynamic wave scrubber for reuse, and the filter residue of the secondary FBL filter 8 is collected by the second mud pool 11 and then sent to the second filter press 12; the exhaust gas from the second filtrate tank 13, the clear acid storage tank 9 and the second mud pool 11 is sent to the spray tower 16.

[0012] Wherein, the method adopts a waste acid purification device, which includes a settler, a first mud pool, a first filter press 1, a first filtrate tank 2, a primary reaction tank 3, a primary mixer 4, a primary FBL filter 5, a secondary reaction tank 6, a secondary mixer 7, a secondary FBL filter 8, a flocculant configuration tank 10, a second mud pool 11, a second filter press 12, a second filtrate tank 13, a clear acid storage tank 9, a sodium hydroxide configuration tank 14, a fan 15, a spray tower 16, a sodium hydrosulfide configuration tank 17 and a sodium hydrosulfide dosing tank 18; the washing liquid outlet of the power wave scrubber, the settler, the first mud pool, the first filter press 1, the first filtrate tank 2, the primary reaction tank 3, the primary mixer 4, the primary FBL filter 5, the secondary reaction tank 6, the secondary mixer 7, the secondary FBL filter 8, the clear acid storage tank 9 and the water replenishment port of the power wave scrubber are connected in sequence through a pipeline; the clear liquid outlet of the settler The second mud pool 11, the second filter press 12, the second filtrate tank 13 and the clear acid storage tank 9 are connected in sequence through pipelines; the sodium hydrosulfide dosing tank 18 is connected to the primary reaction tank 3 and the secondary reaction tank 6 through pipelines, the flocculant configuration tank 10 is connected to the primary mixer 4 and the secondary mixer 7 through pipelines, and the residue outlets of the primary FBL filter 5 and the secondary FBL filter 8 are both connected to the second mud pool 11 through pipelines; the tail gas outlets of the primary reaction tank 3, the primary FBL filter 5, the secondary reaction tank 6, the secondary FBL filter 8, the clear acid storage tank 9, the second mud pool 11, the second filtrate tank 13, the sodium hydrosulfide configuration tank 17 and the sodium hydrosulfide dosing tank 18 are all connected to the air inlet of the spray tower 16 through pipelines with fans 15; the sodium hydroxide configuration tank 14 is connected to the liquid inlet of the spray tower 16 through pipelines.

[0013] Specifically, the concentration of sodium hydroxide in the sodium hydroxide preparation tank 14 is 2-8 wt %. The technical solution provided by the embodiment of the present invention has the following beneficial effects: (1) Sodium hydrosulfide is used as the arsenic removal agent. Compared with sodium sulfide (which emits odor when exposed to air), it is more stable and safer and will introduce less sodium ions; (2) The treatment effect is good. The arsenic content of the treated dilute acid is reduced to below 0.3 mg / L, and the solid content is less than 0.4%, which has a good purification effect on sulfur dioxide flue gas.

[0014] (3) Low cost. The treatment cost of one ton of dilute acid is about RMB 20 per ton.

[0015] (4) There is no hydrogen sulfide emission and there is basically no odor on site. Sodium hydrosulfide is stable under alkaline conditions in the spray tower and no hydrogen sulfide is generated during the spraying process.

[0016] (5) The processing process is simple, the FBL filter can automatically discharge slag, and the labor intensity is low.

[0017] (6) The amount of arsenic-containing waste slag is small, and the transportation cost and use cost are low. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow chart of a method for purifying waste acid and removing arsenic provided by an embodiment of the present invention; Figure 2 It is a principle block diagram of a waste acid purification device in an embodiment of the present invention; Figure 3 Schematic diagram of the structure of the waste acid purification device in the embodiment of the present invention.

[0019] In the figure: 1 the first filter press, 2 the first filtrate tank, 3 the primary reaction tank, 4 the primary mixer, 5 the primary FBL filter, 6 the secondary reaction tank, 7 the secondary mixer, 8 the secondary FBL filter, 9 the clear acid storage tank, 10 the flocculant preparation tank, 11 the second mud tank, 12 the second filter press, 13 the second filtrate tank, 14 the sodium hydroxide preparation tank, 15 the fan, 16 the spray tower, 17 the sodium hydrosulfide preparation tank, 18 the sodium hydrosulfide dosing tank, 19 the first sulfide delivery pump, 20 the second sulfide delivery pump, 21 the flocculant pump, 22 the clear acid delivery pump, 23 the filtrate delivery pump, 24 the filter press pump, 25 the liquid alkali delivery pump, 26 the sodium hydrosulfide delivery pump, 27 the sulfide agent dosing pump, and 28 the circulation pump. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0021] Example 1 See also Figure 2-3Embodiment 1 provides a waste acid purification device, which includes a settler, a first mud pool, a first filter press 1, a first filtrate tank 2, a primary reaction tank 3, a primary mixer 4, a primary FBL filter 5, a secondary reaction tank 6, a secondary mixer 7, a secondary FBL filter 8, a flocculant preparation tank 10, a second mud pool 11, a second filter press 12, a second filtrate tank 13, a clear acid storage tank 9, a sodium hydroxide preparation tank 14, a fan 15, a spray tower 16, a sodium hydrosulfide preparation tank 17, and a sodium hydrosulfide dosing tank 18. The first filtrate tank 2 is lower than the first filter press 1, the second filtrate tank 13 is lower than the second filter press 12, the primary reaction tank 3 is lower than the primary mixer 4, the primary mixer 4 is higher than the primary FBL filter 5, the secondary mixer 7 is higher than the secondary FBL filter 8, the primary reaction tank 3 is lower than the primary FBL filter 5, and the secondary reaction tank 6 is lower than the secondary FBL filter 8. The washing liquid outlet of the power wave scrubber, the settler, the first mud pool, the first filter press 1, the first filtrate tank 2, the primary reaction tank 3, the primary mixer 4, the primary FBL filter 5, the secondary reaction tank 6, the secondary mixer 7, the secondary FBL filter 8, the clear acid storage tank 9 and the water supply port of the power wave scrubber are connected in sequence through pipelines. The clear liquid outlet of the settler is connected to the water supply port of the power wave scrubber through a pipeline with a pump. The second mud pool 11, the second filter press 12, the second filtrate tank 13 and the clear acid storage tank 9 are connected in sequence through pipelines. The sodium hydrosulfide dosing tank 18 is connected to the primary reaction tank 3 and the secondary reaction tank 6 through pipelines, the flocculant configuration tank 10 is connected to the primary mixer 4 and the secondary mixer 7 through pipelines, and the residue outlets of the primary FBL filter 5 and the secondary FBL filter 8 are both connected to the second mud pool 11 through pipelines. The tail gas outlets of the primary reaction tank 3, the primary FBL filter 5, the secondary reaction tank 6, the secondary FBL filter 8, the clear acid storage tank 9, the second mud pool 11, the second filtrate tank 13, the sodium hydrosulfide preparation tank 17 and the sodium hydrosulfide dosing tank 18 are all connected to the air inlet of the spray tower 16 through a pipeline with a fan 15. The sodium hydroxide preparation tank 14 is connected to the liquid replenishment port of the spray tower 16 through a pipeline with a pump. Specifically, a first sulfide delivery pump 19 is provided on the pipeline between the primary reaction tank 3 and the primary mixer 4 in the embodiment of the present invention. A second sulfide delivery pump 20 is provided on the pipeline between the secondary reaction tank 6 and the secondary mixer 7. The flocculant configuration tank 10 is connected to the primary mixer 4 and the secondary mixer 7 through a pipeline with a flocculant pump 21. The clear acid storage tank 9 is connected to the water replenishment port of the power wave scrubber through a pipeline with a clear acid delivery pump 22. The second filtrate tank 13 is connected to the clear acid storage tank 9 through a pipeline with a filtrate delivery pump 23. The second mud pool 11 is connected to the second filter press 12 through a pipeline with a filter press pump 24. The sodium hydroxide configuration tank 14 is connected to the water replenishment port of the spray tower 16 through a pipeline with a liquid alkali delivery pump 25. The sodium hydrosulfide configuration tank 17 is connected to the sodium hydrosulfide dosing tank 18 through a pipeline with a sodium hydrosulfide delivery pump 26. The sodium hydrosulfide dosing tank 18 is connected to the primary reaction tank 3 and the secondary reaction tank 6 through a pipeline with a sulfide agent dosing pump 27. The bottom of the spray tower 16 is connected to the inlet of the circulation pump 28; the outlet of the circulation pump 28 is divided into two outputs, one is connected to the nozzle of the spray tower 16 through a pipeline (to achieve circulating spraying), and the other is connected to the sodium hydrosulfide configuration tank 17 through a pipeline (output after the washing liquid reaches a certain density or pH value).

[0022] The settler in the embodiment of the present invention is an inclined tube settler. Agitators are provided in the first mud pool, the primary reaction tank 3, the secondary reaction tank 6, the flocculant preparation tank 10, the second mud pool 11, the sodium hydroxide preparation tank 14 and the sodium hydrosulfide preparation tank 17. The first filter press 1 and the second filter press 12 are plate and frame filter presses.

[0023] Example 2 Example 2 provides a waste acid purification device, the structure of which is basically the same as that of Example 1. This example discloses the specifications and parameters of some structures, as shown in Table 1: Table 1

[0024] Example 3 See also Figure 1 Embodiment 3 provides a method for purifying waste acid and removing arsenic, using the waste acid purification device disclosed in Embodiment 1 or 2, the method comprising: S1: The wastewater from the power wave scrubber is settled, the clear liquid is sent to the power wave scrubber for reuse, the sludge is filtered through the first filter press 1, and the filtrate is sent to the primary reaction tank 3 as waste acid.

[0025] S2: In the primary reaction tank 3, the waste acid reacts with the desulfurizer from the sodium hydrosulfide preparation tank 17. The amount of the desulfurizer (including sodium hydrosulfide and sodium sulfide) is 0.9-1.1 times the theoretical value based on sodium hydrosulfide. After the reaction is completed, the reaction liquid is sent to the primary mixer 4 to be mixed with the flocculant, and then sent to the primary FBL filter 5 for filtration. After the filtration is completed, the filtrate is sent to the secondary reaction tank 6.

[0026] S3: In the secondary reaction tank 6, the waste acid reacts with the desulfurizer from the sodium hydrosulfide preparation tank 17, and the amount of the desulfurizer is 0.25-0.40 times the theoretical value based on sodium hydrosulfide. The reaction liquid is sent to the secondary mixer 7 to mix with the flocculant, and then sent to the secondary FBL filter 8 for filtration.

[0027] S4: The filtrate from the secondary FBL filter 8 is sent to the power wave scrubber for reuse.

[0028] S5: collecting the filter residues from the primary FBL filter 5 and the secondary FBL filter 8, and then filtering the filter residues through the second filter press 12, and the filtrate is sent to the power wave scrubber for reuse.

[0029] Flocculants are added to the primary FBL filter 5 and the secondary FBL filter 8, and the amount of the flocculants is 0.2-2.0 g / ton of waste acid. The filtrate of the second filter press 12 is output to the second filtrate tank 13, and the filtrate of the secondary FBL filter 8 and the filtrate of the second filtrate tank 13 are collected by the acid cleaning storage tank 9 and then sent to the power wave scrubber for reuse, and the filter residue of the secondary FBL filter 8 is collected by the second mud pool 11 and then sent to the second filter press 12.

[0030] Among them, the tail gas from the primary reaction tank 3, the primary FBL filter 5, the secondary reaction tank 6, the primary FBL filter 5, the sodium hydrosulfide configuration tank 17, the second filtrate tank 13, the clean acid storage tank 9 and the second mud pool 11 is sent to the spray tower 16, in which the sodium hydroxide solution is used for spraying, and the washing liquid containing sodium hydrosulfide and sodium sulfide of the spray tower 16 (concentration requirements, the hydrogen sulfide content of the gas output by the spray tower 16 meets the emission standards) is sent to the sodium hydrosulfide configuration tank 17, and sodium hydrosulfide solid is added to the sodium hydrosulfide configuration tank 17.

[0031] Specifically, the concentration of sodium hydroxide in the sodium hydroxide preparation tank 14 is 2-8 wt %.

[0032] Example 4 Example 4 provides a method for purifying waste acid and removing arsenic, using the waste acid purification device disclosed in Example 2, the method comprising: S1: The wastewater from the power wave scrubber is settled, the clear liquid is sent to the power wave scrubber for reuse, the sludge is filtered through the first filter press 1, and the filtrate (arsenic content is 493 mg / L, solid content is 0.62%) is sent to the primary reaction tank 3 as waste acid. The acid sludge produced by the filter press contains more iron elements and can be sent to the ironmaking unit.

[0033] S2: In the primary reaction tank 3, the waste acid reacts with the desulfurizer from the sodium hydrosulfide preparation tank 17. The amount of the desulfurizer is 0.95 times the theoretical value based on sodium hydrosulfide. After the reaction is completed, the reaction liquid is sent to the primary mixer 4 to be mixed with the flocculant. The amount of the flocculant is 0.6g / ton of waste acid, and then sent to the primary FBL filter 5 for filtration. After the filtration is completed, the filtrate is sent to the secondary reaction tank 6.

[0034] S3: In the secondary reaction tank 6, the waste acid reacts with the desulfurizer from the sodium hydrosulfide preparation tank 17, and the amount of the desulfurizer is 0.38 times the theoretical value based on sodium hydrosulfide. After the reaction is completed, the reaction liquid is sent to the secondary mixer 7 to be mixed with the flocculant, and the amount of the flocculant is 0.4g / ton of waste acid, and then sent to the secondary FBL filter 8 for filtration.

[0035] S4: The filtrate from the secondary FBL filter 8 is sent to the clear acid storage tank 9, and the clear liquid from the clear acid storage tank 9 is sent to the power wave scrubber for reuse.

[0036] S5: collecting the filter residues from the primary FBL filter 5 and the secondary FBL filter 8, and then filtering the filter residues through the second filter press 12, and the filtrate is sent to the clear acid storage tank 9. The filter residues contain more arsenic compounds, and are sent to a specially qualified unit for treatment.

[0037] Among them, the tail gas from the primary reaction tank 3, the primary FBL filter 5, the secondary reaction tank 6, the primary FBL filter 5, the sodium hydrosulfide preparation tank 17, the second filtrate tank 13, the clean acid storage tank 9 and the second mud pool 11 is sent to the spray tower 16, and a sodium hydroxide solution (with a concentration of 3.75wt%) is used for spraying in the spray tower 16. The washing liquid containing sodium hydrosulfide and sodium sulfide in the spray tower 16 is sent to the sodium hydrosulfide preparation tank 17, and sodium hydrosulfide solid is added to the sodium hydrosulfide preparation tank 17.

[0038] The arsenic content of the clear liquid in the clear acid storage tank 9 is 0.21 mg / L, the solid content is 0.37%, and the sulfuric acid system operates normally.

[0039] The processing cost of the method of this patent is calculated as follows: Processing capacity: 60m 3 / d (measured by dilute acid in the first filtrate tank), the arsenic content in the dilute acid is about 500 mg / L (on average).

[0040] Cost of reagents: Sodium hydrosulfide at 2,500 yuan / ton, sodium hydroxide at 2,000 yuan / ton, flocculant at 20,000 yuan / ton, water at 2 yuan / ton, electricity at 0.6 yuan / kWh, and 330 days a year.

[0041] The arsenic content is reduced to 0.3 mg / L, the dosage of sodium hydrosulfide is 1.20-1.33 times the theoretical value (the maximum value is taken), the purity of sodium hydrosulfide is 70%, and the dosage of sodium hydrosulfide is: 60*500*1.33*(56 / 75)*(3 / 2)*330*10 -6 ÷0.7=21.07 tons / year, the cost of sodium hydrosulfide is: 0.25*21.07=52,700 yuan / year. The amount of flocculant used: 60*330*10 -6 = 0.02 tons, the cost of flocculant is: 2*0.02=0.04 million yuan / year. The cost of sodium hydroxide is omitted in detail in this embodiment.

[0042] Electricity bill: The power used is about 60KW, and the car is driven for 6 hours a day. The annual electricity bill is: 60*6*330*0.6=71,200 / year.

[0043] Labor cost: The process is relatively simple, about RMB 200,000.

[0044] Maintenance cost: The equipment is relatively simple, about 50,000 yuan / month.

[0045] Total cost: 145,000 (costs of reagents, raw materials, electricity, etc.) + 200,000 + 50,000 = 395,000. The treatment cost of each ton of dilute acid is about 20 yuan / ton (corresponding to a sulfuric acid output of 500,000 tons / year).

[0046] Sulfide slag output: 60*1.0*(246 / 56)*(1 / 3)*330*10 -6 = 31 tons / year (on a dry basis).

[0047] The "first" and "second" in this embodiment are only used for distinction and have no other special meaning. In this embodiment, the pipelines between the structures are provided with pumps, valves or flow meters as required.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for purifying waste acid by removing arsenic, characterized in that: The method comprises: S1: The wastewater from the power wave scrubber is settled, the clear liquid is sent to the power wave scrubber for reuse, the sludge is filtered through the first filter press (1), and the filtrate is sent to the primary reaction tank (3) as waste acid; S2: In the primary reaction tank (3), the waste acid reacts with the desulfurizing agent from the sodium hydrosulfide preparation tank (17), and the amount of the desulfurizing agent is 0.9-1.1 times the theoretical value based on sodium hydrosulfide. After the reaction is completed, it is sent to the primary FBL filter (5) for filtration. After the filtration is completed, the filtrate is sent to the secondary reaction tank (6); S3: In the secondary reaction tank (6), the waste acid reacts with the desulfurizing agent from the sodium hydrosulfide preparation tank (17), and the amount of the desulfurizing agent is 0.25-0.40 times the theoretical value based on sodium hydrosulfide. After the reaction is completed, it is sent to the secondary FBL filter (8) for filtration; S4: sending the filtrate from the secondary FBL filter (8) to the power wave scrubber for reuse; Adding a flocculant to the primary FBL filter (5) and the secondary FBL filter (8), wherein the amount of the flocculant is 0.2-2.0 g / ton of waste acid; The tail gas from the primary reaction tank (3), the primary FBL filter (5), the secondary reaction tank (6), the primary FBL filter (5) and the sodium hydrosulfide preparation tank (17) is sent to a spray tower (16), a sodium hydroxide solution is used for spraying in the spray tower (16), a washing liquid containing sodium hydrosulfide and sodium sulfide in the spray tower (16) is sent to the sodium hydrosulfide preparation tank (17), and sodium hydrosulfide solid is added to the sodium hydrosulfide preparation tank (17).

2. The method for purifying waste acid according to claim 1, characterized in that: In step S2, the reaction liquid is first sent to the primary mixer (4) to be mixed with the flocculant, and then sent to the primary FBL filter (5) for filtration; in step S3, the reaction liquid is first sent to the secondary mixer (7) to be mixed with the flocculant, and then sent to the secondary FBL filter (8) for filtration.

3. The method for purifying waste acid according to claim 1, characterized in that: The method further comprises: S5: collecting the filter residues from the primary FBL filter (5) and the secondary FBL filter (8), and then filtering the filter residues through the second filter press (12), and sending the filtrate to the power wave scrubber for reuse.

4. The method for purifying waste acid according to claim 3, characterized in that: The filtrate of the second filter press (12) is output to the second filtrate tank (13), the filtrate of the secondary FBL filter (8) and the filtrate of the second filtrate tank (13) are collected through the clear acid storage tank (9) and then sent to the dynamic wave scrubber for reuse, the filter residue of the secondary FBL filter (8) is collected through the second mud pool (11) and then sent to the second filter press (12); the tail gas of the second filtrate tank (13), the clear acid storage tank (9) and the second mud pool (11) is sent to the spray tower (16).

5. The method for purifying waste acid according to claim 3, characterized in that: The method is carried out by using a waste acid purification device, wherein the waste acid purification device comprises a settler, a first mud pool, a first filter press (1), a first filtrate tank (2), a primary reaction tank (3), a primary mixer (4), a primary FBL filter (5), a secondary reaction tank (6), a secondary mixer (7), a secondary FBL filter (8), a flocculant preparation tank (10), a second mud pool (11), a second filter press (12), a second filtrate tank (13), a clear acid storage tank (9), a sodium hydroxide preparation tank (14), and a fan. (15), a spray tower (16), a sodium hydrosulfide preparation tank (17) and a sodium hydrosulfide dosing tank (18); the washing liquid outlet of the power wave scrubber, a settler, a first mud pool, a first filter press (1), a first filtrate tank (2), a primary reaction tank (3), a primary mixer (4), a primary FBL filter (5), a secondary reaction tank (6), a secondary mixer (7), a secondary FBL filter (8), a clear acid storage tank (9) and a water supply port of the power wave scrubber are connected in sequence through pipelines; the clear liquid outlet of the settler The pump is connected to the water supply port of the power wave scrubber through a pipeline; the second mud pool (11), the second filter press (12), the second filtrate tank (13) and the clear acid storage tank (9) are connected in sequence through pipelines; the sodium hydrosulfide dosing tank (18) is connected to the primary reaction tank (3) and the secondary reaction tank (6) through pipelines, the flocculant configuration tank (10) is connected to the primary mixer (4) and the secondary mixer (7) through pipelines, and the filter residue outlets of the primary FBL filter (5) and the secondary FBL filter (8) are connected to the primary FBL filter (5) and the secondary FBL filter (8) through pipelines. The exhaust gas outlets of the primary reaction tank (3), the primary FBL filter (5), the secondary reaction tank (6), the secondary FBL filter (8), the clear acid storage tank (9), the second mud tank (11), the second filtrate tank (13), the sodium hydrosulfide preparation tank (17) and the sodium hydrosulfide dosing tank (18) are all connected to the air inlet of the spray tower (16) through a pipeline with a fan (15); the sodium hydroxide preparation tank (14) is connected to the liquid replenishment port of the spray tower (16) through a pipeline.

6. The method for removing arsenic from waste acid according to claim 5, characterized in that: The concentration of sodium hydroxide in the sodium hydroxide preparation tank (14) is 2-8 wt%.

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