Treatment system for arsenic sulfide slag

Abstract

The utility model relates to an arsenic sulfide slag treatment system which comprises an oxygen pressure leaching unit, a first solid-liquid separation unit, a first reaction unit, a second solid-liquid separation unit, a second reaction unit and a third solid-liquid separation unit which are communicated in sequence, a discharge hole of the third solid-liquid separation unit is communicated with the first reaction unit. According to the treatment system disclosed by the utility model, the arsenic sulfide slag can be treated in a more efficient and energy-saving manner, and harmless and resourceful treatment of the arsenic sulfide slag is realized.

Description

Technical Field

[0001] The utility model relates to a processing system for arsenic sulfide slag, belonging to the field of metallurgical equipment. Background Art

[0002] In the non-ferrous smelting industry, sulfide precipitation is a common method for treating wastewater. It can be used to remove heavy metal ions such as copper, arsenic, and antimony from wastewater, and can also be used to recover valuable metals. The smelting waste slag produced by sulfide precipitation is arsenic sulfide slag. Arsenic sulfide slag has a complex composition, containing not only valuable metals such as copper and rhenium, but also highly toxic arsenic content as high as 10-60%. If it is directly piled up without treatment, it may cause serious harm to the surrounding ecological environment. At the same time, arsenic and its compounds also have many uses. They can be used to produce herbicides and pesticides, wood preservatives, glass clarifiers and decolorizers, non-ferrous metal alloys, etc., and can also produce high-purity arsenic for application in optoelectronics and microelectronics.

[0003] Arsenic sulfide slag disposal costs approximately 20,000 yuan per ton, making it difficult and expensive to dispose of. If left untreated in the smelting system, it can lead to excessive arsenic levels on the anode plates, forcing the purification system to operate at excessive capacity. Therefore, converting arsenic sulfide-containing waste into useful arsenic products offers significant environmental benefits.

[0004] Chinese invention patent application specification CN1321200C discloses a method for separating copper, arsenic, and zinc from a sulfuric acid leachate of high-arsenic dust from copper smelting. The method involves adding a mixture of zinc sulfide and arsenic sulfide as a sulfiding agent to the sulfuric acid leachate to precipitate copper, resulting in copper slag and an arsenic precipitate solution. The arsenic precipitate solution is concentrated to an arsenic concentration of 60 to 100 g / L, cooled to room temperature, and separated into zinc sulfate heptahydrate and a crystallization mother liquor. Sulfur dioxide gas is introduced into the crystallization mother liquor to precipitate arsenic as arsenic trioxide, resulting in arsenic trioxide and an arsenic precipitate solution. A sodium sulfide aqueous solution is added to the arsenic precipitate solution to precipitate zinc and arsenic, resulting in a zinc sulfide and arsenic sulfide mixture that is then used as a sulfiding agent. Consequently, the arsenic separation requires the consumption of external reagents or gases such as sodium sulfide and sulfur dioxide.

[0005] Chinese invention patent application CN 107012340 A discloses a fully wet process for extracting arsenic from arsenic sulfide waste residue. The process involves subjecting the arsenic sulfide waste residue to oxygen pressure leaching, followed by solid-liquid separation, to produce sulfur slag and an oxygen pressure leaching solution containing pentavalent arsenic and H2SO4. The arsenic sulfide waste residue is then used as a reducing agent to reduce pentavalent arsenic, followed by solid-liquid separation, to produce a solution containing trivalent arsenic and a slag phase. The trivalent arsenic-containing solution is then cooled, crystallized, and dried to produce an arsenic white product, while the slag phase is returned to the oxygen pressure leaching process. This solution can recover arsenic from the arsenic sulfide waste residue, but it requires returning the slag phase obtained from the arsenic precipitation to the oxygen pressure leaching process, increasing the load of the oxygen pressure leaching process and limiting the amount of arsenic sulfide waste residue that can be processed per unit time, resulting in limited treatment efficiency. It also increases steam consumption during the oxidation leaching process, hindering energy conservation and cost reduction. Utility Model Content

[0006] The purpose of the utility model is to provide a more efficient arsenic sulfide slag treatment system in response to the deficiencies of the prior art.

[0007] The technical solutions adopted in this utility model are as follows:

[0008] A system for treating arsenic sulfide slag comprises an oxygen pressure leaching unit, a first solid-liquid separation unit, a first reaction unit, a second solid-liquid separation unit, a second reaction unit and a third solid-liquid separation unit, which are connected in sequence. The first reaction unit and the second reaction unit are respectively provided with a sulfide inlet, and the discharge port of the third solid-liquid separation unit is connected to the first reaction unit.

[0009] Thus, the arsenic sulfide slag to be treated and sulfuric acid solution (other acid solutions that can meet the requirements of oxygen pressure leaching reaction, such as hydrochloric acid, nitric acid, etc.), oxygen, etc. can be input into the oxygen pressure leaching unit. Through the oxygen pressure leaching reaction, the valence state of the arsenic element in the arsenic sulfide slag is increased to +5, and enters the leachate in the form of H3AsO4, while other impurities such as Fe will enter the leaching slag in the form of arsenic ice iron; then, the leachate and the leaching slag are separated by the first solid-liquid separation unit; after the leachate rich in H3AsO4 enters the first reaction unit, it reacts with the arsenic sulfide slag and other arsenic precipitants added through the sulfide inlet and the arsenic precipitate returned from the third solid-liquid separation unit, and the +2-valent arsenic in the arsenic sulfide slag and the arsenic precipitate will react with the +5-valent arsenic in the leachate to generate H3AsO3 precipitate with arsenic in the +3-valent state (which can be further decomposed into A s2O3, H2O); the slurry after the reaction in the first reaction unit enters the second solid-liquid separation unit for solid-liquid separation to obtain crude arsenic trioxide and a first-stage arsenic precipitation liquid; then, the first-stage arsenic precipitation liquid enters the second reaction unit and reacts with an arsenic precipitation agent such as arsenic sulfide slag added through the sulfide inlet, so that the remaining +5-valent arsenic in the first-stage arsenic precipitation liquid is converted into +3-valent arsenic and enters the slag phase; then, solid-liquid separation is performed in the third solid-liquid separation unit to obtain a second-stage arsenic precipitation liquid and an arsenic precipitation slag rich in +3-valent arsenic. At this time, the arsenic content in the second-stage arsenic precipitation liquid is already quite low, and it can be further open-circuited (such as further reduction and arsenic removal) or returned to the oxygen pressure leaching unit for reuse. The arsenic precipitation slag returns to the first reaction unit to recover the +3-valent arsenic therein, and the residual arsenic sulfide therein participates in the first-stage arsenic precipitation process to be more fully utilized. In summary, the utility model does not need to return the arsenic precipitation slag to the oxygen pressure leaching unit, which can reduce the processing load of the oxygen pressure leaching unit and make it dedicated to the oxygen pressure leaching of arsenic sulfide slag, which helps to improve the processing efficiency and reduce energy consumption such as steam; moreover, by performing two-stage arsenic precipitation reactions in the first reaction unit and the second reaction unit and returning the second-stage arsenic precipitation slag to the first reaction unit, a higher arsenic recovery rate can be guaranteed.

[0010] Furthermore, during operation, the amount of arsenic sulfide added to the first reaction unit is controlled not to be excessive so as to reduce the impurity content in the subsequent crude arsenic trioxide; the amount of arsenic sulfide added to the second reaction unit is controlled to be sufficient or excessive to ensure sufficient precipitation of As2O3. The excess As2S2 contained in the second-stage arsenic precipitation slag can be returned and used as an arsenic precipitant for the first-stage arsenic precipitation reaction to increase the arsenic precipitation rate and can still be effectively utilized.

[0011] Optionally, during treatment, the arsenic sulfide slag is ground until more than 90 wt % of the particles have a mesh size of less than 100 mesh, so as to facilitate leaching reaction and arsenic precipitation reaction.

[0012] Optionally, the main components of the arsenic sulfide slag are calculated in percentage by mass as follows: Cu 0.05-12, Pb 0.05-10, Zn 0.05-10, As 10-60, S 10-55, with the unit being %.

[0013] Preferably, the reaction temperature in the oxygen pressure leaching unit is controlled to be 90-110°C, the leaching pressure is 0.5-0.8 MPa, and the reaction time is 2-4 hours. Preferably, the mass ratio of arsenic sulfide to sulfuric acid solution in the arsenic sulfide slag is 1:2-7, and the concentration of the sulfuric acid solution is 100-200 g / l.

[0014] Optionally, a first storage tank connected to the liquid outlet of the first solid-liquid separation unit is further included, and a first pump is provided between the outlet of the first storage tank and the first reaction unit. This can serve as a buffer for the leachate and facilitate process adjustment and coordination between the functional units.

[0015] Optionally, a second storage tank connected to the liquid outlet of the second solid-liquid separation unit is included, and a second pump is provided between the outlet of the second storage tank and the second reaction unit. This can serve as a buffer for the liquid after the arsenic precipitation, facilitating the connection and coordination between the second solid-liquid separation unit and the second reaction unit.

[0016] Optionally, a slurry mixing tank connected to the discharge port of the third solid-liquid separation unit is included, and a third pump is provided between the outlet of the slurry mixing tank and the first reaction unit. This can buffer and slurry the secondary arsenic precipitation residue, facilitate its transportation and return, and further help improve the reaction efficiency after return.

[0017] Optionally, the oxygen pressure leaching unit includes an oxygen pressure leaching tank, a flash tank and an adjusting tank which are connected in sequence, and the discharge port of the adjusting tank is connected to the first solid-liquid separation unit.

[0018] Optionally, a first stirring mechanism is provided in the first reaction unit, thereby improving the reaction efficiency.

[0019] Optionally, a second stirring mechanism is provided in the second reaction unit, thereby improving the reaction efficiency.

[0020] Optionally, the solid-liquid separation unit is a filter press.

[0021] Compared with the prior art, the utility model has the following advantages:

[0022] (1) The treatment system of the present invention can treat arsenic sulfide slag more efficiently and energy-efficiently, thereby achieving harmless and resource-based treatment of arsenic sulfide slag.

[0023] (2) In the two-stage arsenic precipitation stage, the utility model can obtain relatively pure crude arsenic trioxide by controlling the amount of arsenic sulfide slag and other arsenic precipitation agents added in the first reaction unit, while the arsenic precipitation slag in the second reaction unit has a higher arsenic sulfide content and can be returned to the first reaction unit as an arsenic precipitation agent, effectively reducing the arsenic content in the liquid after arsenic precipitation, and the arsenic precipitation rate can reach more than 87.25%.

[0024] (3) The treatment system of the present invention first performs a pressurized and heated leaching process through an oxygen pressure leaching unit. The leaching rate of As is high and can reach more than 98.68%. Then, through two-stage arsenic precipitation, arsenic sulfide and the like are used to react with the +5-valent arsenic in the solution. The direct recovery rate of As can reach more than 80%. After the second-stage arsenic precipitation, the liquid contains only about 20g / L of arsenic.

[0025] (4) The treatment system of the present invention utilizes the neutralization reaction of arsenic, and the treatment process is short. While realizing the resource utilization and harmlessness of arsenic, it also achieves the purpose of high efficiency and energy saving.

[0026] (5) The processing system of the utility model has the advantages of high resource utilization, low production cost, stable technical indicators, good production environment, and simple process flow.

[0027] (6) The treatment system of the present invention can be used to treat arsenic sulfide slag produced by sewage and waste acid treatment, and can also be used to treat solids or liquids containing arsenic, copper, lead, zinc, etc. and arsenic sulfide slag produced during the non-ferrous metal smelting process. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a simplified structural diagram of the arsenic sulfide slag treatment system of Example 1 of the present invention.

[0029] In the figure, 1-oxygen pressure leaching tank, 2-flash tank, 3-adjusting tank, 4-first solid-liquid separation unit, 5-first storage tank, 6-first reaction unit, 7-second solid-liquid separation unit, 8-second storage tank, 9-second reaction unit, 10-third solid-liquid separation unit, 11-slurry mixing tank, 12-first pump, 13-second pump, 14-third pump, 15-fourth pump, 16-fifth pump. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments. It should be noted that the embodiments and features of the embodiments of the present invention may be combined unless they conflict. For ease of description, the words "upper," "lower," "left," and "right" appear below merely to indicate the directions of upper, lower, left, and right in the accompanying drawings and do not limit the structure.

[0031] Example 1

[0032] See also Figure 1 A system for treating arsenic sulfide slag comprises an oxygen pressure leaching unit, a fourth pump, a first solid-liquid separation unit, a first reaction unit, a second solid-liquid separation unit, a second reaction unit, a fifth pump and a third solid-liquid separation unit connected in sequence, wherein the first reaction unit and the second reaction unit are respectively provided with a sulfide inlet, and the discharge port of the third solid-liquid separation unit is connected to the first reaction unit.

[0033] The treatment system further includes a first storage tank connected to the liquid outlet of the first solid-liquid separation unit, a second storage tank connected to the liquid outlet of the second solid-liquid separation unit, and a slurry mixing tank connected to the discharge port of the third solid-liquid separation unit. A first pump is provided between the outlet of the first storage tank and the first reaction unit, a second pump is provided between the outlet of the second storage tank and the second reaction unit, and a third pump is provided between the outlet of the slurry mixing tank and the first reaction unit. The oxygen pressure leaching unit includes an oxygen pressure leaching tank, a flash tank, and an adjusting tank connected in sequence. The discharge port of the adjusting tank is connected to the first solid-liquid separation unit. A first stirring mechanism is provided in the first reaction unit. A second stirring mechanism is provided in the second reaction unit. Each solid-liquid separation unit is a filter press.

[0034] The arsenic sulfide slag described in Table 1 was treated using the above treatment system.

[0035] Table 1 Main components of arsenic sulfide slag produced in wastewater treatment of a smelting enterprise

[0036]

[0037] The specific processing process is as follows:

[0038] (1) The arsenic sulfide slag described in Table 1 was ground to a particle size of less than 100 mesh. The arsenic sulfide slag was then mixed with the liquid after the second stage arsenic precipitation at a liquid-solid mass ratio of 7:1 to prepare a slurry. Sulfuric acid was added to make the initial concentration of sulfuric acid in the reaction system 100 g / L. The mixture was then fed into an oxygen pressure leaching tank and heated to a reaction temperature of 100°C using steam. Oxygen-enriched air was introduced and the leaching pressure was controlled at 0.8 MPa. After reacting for 2 hours, the mixture was filtered through the first solid-liquid separation unit to obtain an oxygen pressure leaching solution and oxygen pressure leaching residue. The oxygen pressure leaching residue was sent to sulfur flotation or directly used for batching. After heated oxygen pressure leaching, the arsenic leaching rate reached 96.12%. Most of the As in the raw material entered the solution, while Pb, Fe, etc. remained in the leaching residue. The arsenic concentration in the oxygen pressure leaching solution was increased to above 80 g / L.

[0039] (2) The oxygen pressure leaching solution is input into the first reaction unit, and arsenic sulfide slag and second-stage arsenic precipitation slag are added. The reaction temperature is controlled at 70°C, and the initial liquid-solid mass ratio is 5:1. After reacting for 2 hours, the temperature is reduced and filter press is performed to obtain crude arsenic trioxide and a first-stage arsenic precipitation liquid; then, the first-stage arsenic precipitation liquid is input into the second reaction unit, and arsenic sulfide slag is added. The initial liquid-solid mass ratio is controlled at 4:1. After reacting for 4 hours, the temperature is reduced and filter press is performed to obtain a second-stage arsenic precipitation slag and a second-stage arsenic precipitation liquid (containing about 20 g / L of arsenic).

[0040] Comparative Example 1

[0041] Example 1 was repeated, except that the treatment system of Comparative Example 1 did not include the second reaction unit and the third solid-liquid separation unit. The arsenic content of the precipitated liquid obtained by the first stage arsenic precipitation was about 30 g / L.

[0042] Comparative Example 2

[0043] Example 1 was repeated, except that the treatment system of Comparative Example 1 did not include the second reaction unit and the third solid-liquid separation unit, and the amount of arsenic sulfide slag added to the first reaction unit was the same as the total amount of arsenic sulfide slag added to the first and second reaction units in Example 1. The resulting crude arsenic trioxide contained 20 wt% sulfur.

[0044] By comparison, using only one stage of arsenic precipitation and not adding enough arsenic sulfide slag will result in excessively high arsenic content in the post-precipitation solution, causing more arsenic ions to enter the process cycle with the solution, resulting in wasteful production capacity. Adding too much arsenic sulfide slag to the first reaction unit will result in excessive impurities in the arsenic trioxide product, increasing the burden on subsequent processing steps. The present treatment system uses a two-stage arsenic precipitation process and returns the second-stage arsenic precipitation slag to the first reaction unit, which can promote the arsenic precipitation reaction, increase the arsenic sedimentation rate, and reduce the impurity content in the arsenic sulfide.

[0045] The contents described in the above embodiments should be understood as these embodiments are only used to more clearly illustrate the present invention, and are not used to limit the scope of the present invention. After reading the present invention, various equivalent modifications to the present invention made by those skilled in the art fall within the scope defined by the claims attached to this application.

Claims

1. A system for treating arsenic sulfide slag, characterized in that: The method comprises an oxygen pressure leaching unit, a first solid-liquid separation unit, a first reaction unit, a second solid-liquid separation unit, a second reaction unit and a third solid-liquid separation unit which are connected in sequence. The first reaction unit and the second reaction unit are respectively provided with a sulfide inlet. The discharge port of the third solid-liquid separation unit is connected to the first reaction unit.

2. The arsenic sulfide slag treatment system according to claim 1, characterized in that: It also includes a first storage tank connected to the liquid outlet of the first solid-liquid separation unit, and a first pump is provided between the outlet of the first storage tank and the first reaction unit.

3. The arsenic sulfide slag treatment system according to claim 1, characterized in that: It also includes a second storage tank connected to the liquid outlet of the second solid-liquid separation unit, and a second pump is provided between the outlet of the second storage tank and the second reaction unit.

4. The treatment system for arsenic sulfide slag according to claim 1, characterized in that: It also includes a slurry adjustment tank connected to the discharge port of the third solid-liquid separation unit, and a third pump is provided between the outlet of the slurry adjustment tank and the first reaction unit.

5. The arsenic sulfide slag treatment system according to any one of claims 1 to 4, characterized in that: The oxygen pressure leaching unit comprises an oxygen pressure leaching tank, a flash tank and an adjusting tank which are connected in sequence, and the discharge port of the adjusting tank is connected to the first solid-liquid separation unit.

6. The arsenic sulfide slag treatment system according to any one of claims 1 to 4, characterized in that: A first stirring mechanism is provided in the first reaction unit.

7. The arsenic sulfide slag treatment system according to any one of claims 1 to 4, characterized in that: A second stirring mechanism is provided in the second reaction unit.

8. The arsenic sulfide slag treatment system according to any one of claims 1 to 4, characterized in that: The solid-liquid separation unit is a filter press.

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