Purification method of crude arsenic trioxide

Abstract

The invention relates to a purification method of crude arsenic trioxide, and belongs to the technical field of metallurgy. The specific process comprises the following steps: firstly, drying crude arsenic trioxide containing about 85-95% of arsenic, then conveying the dried arsenic trioxide to a full-automatic belt type electric furnace in a closed manner, extracting and volatilizing arsenic-rich flue gas into a settling chamber under negative pressure by adopting a multi-section multi-zone gradient temperature control distillation-steam slow cooling crystallization-step grade purification process, so as to obtain fine As2O3 with the purity of 99.5% or above, evaporation arsenic removal residues are returned to an oxygen pressure leaching process to recover valuable metals such as copper and lead, and tail gas subjected to sedimentation dust collection is subjected to bag dust collection treatment and is sent to a metal arsenic working procedure. The method is easy to operate, efficient and stable in purification effect and low in production cost, zero pollution and zero emission of the arsenic extraction process are achieved, the problems of purification of crude arsenic smoke dust and recovery of high-purity white arsenic in copper smelting enterprises are solved, the As2O3-1 grade arsenic trioxide product is efficiently and economically prepared in an environment-friendly and energy-saving mode, and industrial application is achieved.

Description

Technical Field

[0001] The invention relates to a method for preparing As2O3 suitable for further purifying crude arsenic trioxide (crude white arsenic 95% As2O3) produced by leaching arsenic sulfide slag, a byproduct of copper smelting, to a purity of more than 99.5%, belonging to the technical field of metallurgy. Background Art

[0002] Arsenic mostly coexists or coexists with nonferrous metal ores. With the continuous consumption of high-quality nonferrous metal concentrate resources, the proportion of high-arsenic, high-sulfur and difficult-to-treat nonferrous metal concentrates at home and abroad continues to increase. Most of the arsenic in them is ultimately produced in the form of arsenic sulfide slag. The As mass fraction in arsenic sulfide slag is as high as 10%~50%. It has high leaching toxicity and strong corrosiveness. If improperly handled, it will become the most important source of environmental pollution for my country's nonferrous metallurgical enterprises, seriously restricting their development. At the same time, arsenic sulfide slag is also an important secondary resource of arsenic, from which various arsenic-containing products can be extracted.

[0003] At present, the extraction of arsenic trioxide from arsenic-containing materials such as arsenic sulfide slag mainly adopts two major processes: pyrometallurgy and hydrometallurgy. The pyrometallurgy process mainly includes roasting in a rotary kiln, reverberatory furnace or electric furnace or smelting in a smelting furnace. The high-arsenic flue gas is collected in a condensation settling chamber and a bag filter to obtain a crude arsenic trioxide product. Although this method has low cost, simple process and mature technology, the product quality is unstable, the degree of automation is low, and it seriously pollutes the environment, which limits its industrial application. The hydrometallurgy process mainly includes two stages: selective leaching and final disposal of arsenic, which converts arsenic compounds into products mainly composed of arsenic trioxide. At present, smelting enterprises mainly use oxygen pressure leaching assisted by Cu 2+ Arsenic trioxide products are produced by displacement, arsenic sulfide and SO2 reduction, of which the As2O3 content is about 95%, and still contains a small amount of impurities such as lead, copper, antimony, bismuth, etc. Therefore, it is an urgent task for non-ferrous metallurgical enterprises to develop a safe, efficient, clean, environmentally friendly, highly automated processing technology with product purity in line with national standards. Summary of the invention

[0004] The present invention aims to overcome the deficiencies in the above existing arsenic trioxide preparation technology and provides a method for purifying crude arsenic trioxide, which directly processes the crude arsenic trioxide through a fully automatic belt electric furnace to produce an arsenic trioxide product that meets enterprise standards and has a main component greater than 99.5%.

[0005] In order to achieve the above technical purpose, the technical solution adopted by the present invention is:

[0006] 1. A method for purifying crude arsenic trioxide, characterized in that it specifically comprises the following steps:

[0007] 1) The wet crude arsenic trioxide produced in the wet process is steam dried in a dryer to remove moisture;

[0008] 2) The crude arsenic trioxide dried in step 1) is crushed, transported to the raw material bin by a buried scraper, and continuously fed to the distributor of the fully automatic belt electric furnace (steel belt furnace) by a spiral metering device. The raw materials are accurately and evenly distributed on the steel belt. The crude arsenic trioxide raw material enters the furnace with the steel belt to form a thin material layer, and is purified by multi-stage and multi-zone gradient temperature control distillation to obtain arsenic-rich flue gas and evaporation arsenic removal residue;

[0009] 3) The arsenic-rich flue gas obtained in step 2) is subjected to slow cooling and crystallization. The arsenic vapor is introduced into 8-stage (1#~8#) cooling and settling chambers in sequence through the negative pressure fan of the exhaust section between the two evaporation sections, and is transported to the rotary vibrating screen for screening and grading through a scraper. Qualified products are packaged to obtain refined As2O3 products. If the density is unqualified, it enters the mobile silo and is sent to the metal arsenic process. The evaporation and arsenic removal residue enters the residue cleaning area with the steel belt and returns to the oxygen pressure leaching process to recover valuable metals such as copper and lead. The volatile tail gas from the sedimentation and dust collection is further dedusted by the bag filter and enters the absorption tower for adsorption to meet the standards before being discharged;

[0010] Furthermore, in step 1), the dryer adopts steam drying, the steam temperature is controlled at 120-150° C., the steam pressure is 0.3-0.5 MPa, and the water content of crude arsenic trioxide is less than 1%;

[0011] Furthermore, the crude arsenic trioxide in step 1) includes the following main components in terms of mass percentage (%): As2O3: 85-95, Sb≤1, Cu≤0.8, Zn≤0.1, Pb≤0.6, Fe≤0.5, Bi≤0.6, H2O≤20;

[0012] Furthermore, in step 2), the multi-stage multi-zone gradient temperature-controlled distillation is divided into an evaporation stage, a heating stage and an exhaust stage. The temperature of the heating stage (1-3 zones) is rapidly heated to 650-680°C; the evaporation stage is divided into an evaporation stage 1 (4-8 zones) and an evaporation stage 2 (9-11 zones). The temperature of the evaporation stage 1 is maintained at 680-750°C to control the material to be fully evaporated. The evaporation stage 2 is a cooling zone, and the arsenic removal slag is gradiently cooled to 500-550°C; the exhaust stage temperature is controlled at 350-400°C; and the furnace temperature uniformity is controlled to ±10°C.

[0013] Furthermore, in step 3), the settling cooling temperature is reduced to <150°C;

[0014] Furthermore, in step 3), the inlet temperature of the bag dust collecting bag chamber is controlled to be 100-120°C;

[0015] Furthermore, the refined As2O3 in step 3) includes the following main components in terms of mass percentage (%): As2O3≥99.5, Sb≤0.1, Cu≤0.005, Zn≤0.001, Pb≤0.001, Fe≤0.002, Bi≤0.001.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1) The present invention develops a technology for purifying arsenic-containing dust, solves the problem of crude arsenic pollution and purification in copper smelting enterprises, and realizes the efficient and comprehensive recovery and utilization of arsenic resources;

[0018] 2) The present invention develops a safe and efficient closed conveying technology, which solves the problems of short-process low-cost crude arsenic dust conveying, easy adhesion and clogging of pipelines by conveyed materials, and low production flexibility;

[0019] 3) Based on the traditional distillation and purification technology, the present invention innovatively uses a multi-stage and multi-zone gradient temperature-controlled distillation-steam slow cooling crystallization-tiered purification process to solve the problems of poor operating environment, imprecise temperature control, and a large number of co-volatile impurities in traditional reverberatory furnaces and rotary kilns, thereby ensuring the purity of arsenic trioxide products and realizing industrial application.

[0020] The method of the present invention is suitable for further purification of arsenic-rich smoke containing 85-95% of As2O3 in large-scale recovery and treatment, and synthesizes refined As2O3 products with a main component greater than 99.5%. The whole process is simple to operate, the purification effect is efficient and stable, the production cost is low, and zero pollution and zero emission of the arsenic extraction process are achieved. It has strong industrial operability and is effective in removing trace arsenic impurity elements. Impurity elements such as copper, antimony, bismuth, zinc, and iron can be reduced to a considerable level, which solves the problem of purifying crude arsenic smoke and recovering high-purity white arsenic in copper smelting enterprises, and realizes industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The figure is a process flow chart for purifying crude arsenic trioxide according to the present invention. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings of the present invention. It should be clearly pointed out that the protection scope of the present invention is not limited to the following specific embodiments.

[0023] This embodiment provides a method for purifying crude arsenic trioxide, comprising the following steps:

[0024] Embodiment 1:

[0025] 1) The wet crude arsenic trioxide produced by the wet process of arsenic sulfide slag is steam dried in a dryer to remove moisture;

[0026] 2) The crude arsenic trioxide dried in step 1) is crushed, transported to the raw material bin by a buried scraper, and continuously fed to the distributor of the fully automatic belt electric furnace (steel belt furnace) by a spiral metering device. The raw materials are accurately and evenly distributed on the steel belt. The crude arsenic trioxide raw material enters the furnace with the steel belt to form a thin material layer, and is purified by multi-stage and multi-zone gradient temperature control distillation to obtain arsenic-rich flue gas and evaporation arsenic removal residue;

[0027] 3) The arsenic-rich flue gas obtained in step 2) is subjected to slow cooling and crystallization. The arsenic vapor is introduced into the 8-stage cooling and settling chamber in sequence through the negative pressure fan of the exhaust section between the two evaporation sections, and is transported to the rotary vibrating screen for screening and grading by a scraper. The qualified products are packaged to obtain refined As2O3 products. The evaporation and arsenic removal residues enter the residue cleaning area with the steel belt and return to the oxygen pressure leaching process to recover valuable metals such as copper and lead. The volatile tail gas from the sedimentation and dust collection is further dedusted by the bag filter and enters the absorption tower for adsorption to meet the standards before being discharged;

[0028] In step 1), the crude arsenic trioxide is steam dried, the steam temperature is controlled at 140° C., the steam pressure is 0.4 MPa, the water content of the crude arsenic trioxide is less than 1%, and the ICP component test results (%) of the crude arsenic trioxide are shown in Table 1;

[0029] Table 1 ICP component test results of crude arsenic trioxide in Example 1 (%)

[0030]

[0031] Step 2) In the multi-stage multi-zone gradient temperature-controlled distillation heating section, the temperature is quickly heated to 680°C, the temperature of the first evaporation section is maintained at 680°C, the second evaporation section is a cooling zone, the arsenic removal slag is gradiently cooled to 500°C, the temperature of the exhaust section is controlled at 380°C, and the furnace temperature uniformity is controlled at ±10°C;

[0032] Step 3) the sedimentation cooling temperature is reduced to 120°C;

[0033] Step 3) The inlet temperature of the bag dust collecting bag chamber is controlled at 110°C;

[0034] Step 3) Collect refined As2O3 from 8-stage sedimentation chambers 1# to 8#, and detect to obtain an arsenic trioxide product containing more than 99.5% As2O3 (reaching the national standard "Arsenic Trioxide" GB26721-2011) As2O3-1 grade standard). The ICP test results of the refined As2O3 are shown in Table 3.

[0035] Table 2 ICP composition test results of refined As2O3 in 1#~8# sedimentation chambers in Example 1 (%)

[0036]

[0037] Embodiment 2:

[0038] 1) The wet crude arsenic trioxide produced by the wet process of arsenic sulfide slag is steam dried in a dryer to remove moisture;

[0039] 2) The crude arsenic trioxide dried in step 1) is crushed, transported to the raw material bin by a buried scraper, and continuously fed to the distributor of the fully automatic belt electric furnace (steel belt furnace) by a spiral metering device. The raw materials are accurately and evenly distributed on the steel belt. The crude arsenic trioxide raw material enters the furnace with the steel belt to form a thin material layer, and is purified by multi-stage and multi-zone gradient temperature control distillation to obtain arsenic-rich flue gas and evaporation arsenic removal residue;

[0040] 3) The arsenic-rich flue gas obtained in step 2) is subjected to slow cooling and crystallization. The arsenic vapor is introduced into the 8-stage cooling and settling chamber in sequence through the negative pressure fan of the exhaust section between the two evaporation sections, and is transported to the rotary vibrating screen for screening and grading by a scraper. The qualified products are packaged to obtain refined As2O3 products. The evaporation and arsenic removal residues enter the residue cleaning area with the steel belt and return to the oxygen pressure leaching process to recover valuable metals such as copper and lead. The volatile tail gas from the sedimentation and dust collection is further dedusted by the bag filter and enters the absorption tower for adsorption to meet the standards before being discharged;

[0041] In step 1), the crude arsenic trioxide is steam dried, the steam temperature is controlled at 140° C., the steam pressure is 0.4 MPa, the water content of the crude arsenic trioxide is less than 1%, and the ICP component test results (%) of the crude arsenic trioxide are shown in Table 3;

[0042] Table 3 ICP component test results of crude arsenic trioxide in Example 2 (%)

[0043]

[0044] Step 2) In the multi-stage multi-zone gradient temperature-controlled distillation heating section, the temperature is quickly heated to 680°C, the temperature of the first evaporation section is maintained at 680°C, the second evaporation section is a cooling zone, the arsenic removal slag is gradiently cooled to 520°C, the temperature of the exhaust section is controlled at 360°C, and the furnace temperature uniformity is controlled at ±10°C;

[0045] Step 3) the sedimentation cooling temperature is reduced to 130°C;

[0046] Step 3) The inlet temperature of the bag dust collecting bag chamber is controlled at 110°C;

[0047] Step 3) Collect the refined As2O3 from the 8-stage sedimentation chambers from 1# to 8#, and test to obtain an arsenic trioxide product containing more than 99.5% As2O3 (reaching the national standard "Arsenic Trioxide" GB26721-2011) As2O3-1 grade standard). The ICP test results of the refined As2O3 are shown in Table 4:

[0048] Table 4 ICP composition test results of refined As2O3 in 1#~8# sedimentation chambers in Example 2 (%)

[0049]

[0050] Finally, it should be pointed out that: although the above embodiments have illustrated the technical solutions of the present invention, they are not limited thereto. Those skilled in the art should understand that various changes, modifications, and substitutions can be made without departing from the principles of the present invention, but these improvements should also be regarded as the protection scope of the present invention.

Claims

1. A method for purifying crude arsenic trioxide, characterized in that: The specific steps include: 1) The wet crude arsenic trioxide produced in the wet process is steam dried in a dryer to remove moisture; 2) The crude arsenic trioxide dried in step 1) is crushed, transported to the raw material bin by a buried scraper, and continuously fed to the distributor of the fully automatic belt electric furnace (steel belt furnace) by a spiral metering distribution device. The raw materials are accurately and evenly distributed on the steel belt. The crude arsenic trioxide raw material enters the furnace with the steel belt to form a thin material layer, and is purified by multi-stage and multi-zone gradient temperature control distillation to obtain arsenic-rich flue gas and evaporation arsenic removal residue; 3) The arsenic-rich flue gas obtained in step 2) is subjected to slow cooling and crystallization. The arsenic vapor is introduced into the 8-stage cooling and settling chamber in sequence through the negative pressure fan of the exhaust section between the two evaporation sections, and is transported to the rotary vibrating screen for screening and grading by the scraper. The qualified products are packaged to obtain refined As2O3 products. If the density is unqualified, it enters the mobile silo and is sent to the metal arsenic process. The evaporation and arsenic removal residue enters the residue cleaning area with the steel belt and returns to the oxygen pressure leaching process to recover valuable metals such as copper and lead. The volatile tail gas from the sedimentation and dust collection is further dedusted by the bag filter and enters the absorption tower for adsorption to meet the standards before being discharged.

2. The method for purifying crude arsenic trioxide according to claim 1, characterized in that: Step 1) The dryer uses steam drying, the steam temperature is controlled at 120-150° C., the steam pressure is 0.3-0.5 MPa, and the water content of the crude arsenic trioxide is less than 1%.

3. The method for purifying crude arsenic trioxide according to claim 1, characterized in that: Step 1) The crude arsenic trioxide comprises the following main components in terms of mass percentage (%): As2O3: 85-95, Sb≤1, Cu≤0.8, Zn≤0.1, Pb≤0.6, Fe≤0.5, Bi≤0.6, H2O≤20.

4. The method for purifying crude arsenic trioxide according to claim 1, characterized in that: Step 2) The multi-stage and multi-zone gradient temperature-controlled distillation is divided into an evaporation section, a heating section and an exhaust section. The temperature of the heating section (zones 1 to 3) is rapidly heated to 650 to 680°C; the evaporation section is divided into an evaporation section 1 (zones 4 to 8) and an evaporation section 2 (zones 9 to 11). The temperature of the evaporation section 1 is maintained at 680 to 750°C to ensure that the material is fully evaporated; the evaporation section 2 is a cooling zone, and the arsenic removal slag is gradiently cooled to 500 to 550°C; the temperature of the exhaust section is controlled at 350 to 400°C, and the furnace temperature uniformity is controlled to ±10°C.

5. The method for purifying crude arsenic trioxide according to claim 1, characterized in that: Step 3) the sedimentation cooling temperature is reduced to <150°C.

6. The method for purifying crude arsenic trioxide according to claim 1, characterized in that: Step 3) The inlet temperature of the bag dust collecting chamber is controlled at 100-120°C.

7. The method according to claim 1, characterized in that Step 3) The refined As2O3 comprises the following main components in terms of mass percentage (%): As2O3≥99.5, Sb≤0.1, Cu≤0.005, Zn≤0.001, Pb≤0.001, Fe≤0.002, Bi≤0.

001.

8. The method according to claim 1, characterized in that: Step 3) The inlet temperature of the bag dust collecting chamber is controlled at 100-120°C.

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