Method for controlling and separating arsenic and valuable metals in smelting flue gas

Abstract

The application relates to a method for regulating and separating arsenic and valuable metals in smelting flue gas, and belongs to the field of clean production technology. After chalcopyrite powder is mixed into smelting flue gas, on one hand, metal oxides are converted into sulfates, and on the other hand, formed arsenate can be dissociated, arsenic is volatilized in the form of As2O3, and metals are converted into corresponding sulfates and oxides to return to a smelting system, formation of arsenate in the flue gas is inhibited, the purpose of separating arsenic and valuable metals is achieved, and the efficiency of dry collection of As2O3 in the flue gas is improved. Formation of arsenic-containing dust is reduced, and production cost of a smelting enterprise is saved.

Description

Technical Field

[0001] This invention relates to the field of clean production technology, and in particular to a method for regulating and separating arsenic and valuable metals in smelting flue gas. Background Technology

[0002] my country boasts the world's largest non-ferrous metal smelting capacity and output, making non-ferrous metals a crucial pillar of the national economy. During mineral formation, arsenic often coexists with copper, lead, and zinc minerals. Due to its volatility, high concentrations of arsenic enter the smelting flue gas during the smelting process, primarily in the form of arsenic trioxide. Arsenic in the flue gas not only affects the catalytic conversion system in subsequent acid production processes but also serves as a significant source of atmospheric arsenic pollutants. Therefore, its effective purification is crucial for air pollution control and the green development of the smelting industry.

[0003] Currently, arsenic removal from flue gas in smelting enterprises mainly involves two processes: wet and dry. In the wet process, after initial purification of arsenic-containing flue gas using waste heat recovery and electrostatic precipitators, dilute sulfuric acid, which has high solubility for arsenic, is sprayed through a spray tower to induce arsenic into the liquid phase. The purified, high-concentration SO2 flue gas is then sent to an acid production plant. Finally, the arsenic-containing waste acid is precipitated as sulfide to obtain hazardous solid waste, arsenic sulfide slag. In the dry process, smelting flue gas from the furnace opening recovers waste heat through a waste heat boiler, lowering the temperature to approximately 380–400°C. Subsequently, most of the particulate matter is removed by an electrostatic precipitator. Then, the flue gas, after condensation in an evaporative cooler, is rapidly cooled to 130–150°C, achieving rapid condensation of arsenic into particulate matter, which is finally collected as pure As2O3 by a bag filter. The wet process produces a large amount of waste acid with a high arsenic concentration (0.5–20 g / L), requiring significant investment and complex technology. Dry arsenic recovery processes are characterized by short flow rates, high removal and recovery efficiencies, and the ability to directly recover arsenic and valuable metals. From a resource utilization perspective, dry arsenic recovery processes have potential advantages. However, the formation of arsenate during flue gas condensation inhibits the efficient recovery of arsenic in dry processes. Currently, CN104451167 A discloses a method that utilizes spraying, air cooling, and other methods to perform multi-stage cooling of arsenic-containing flue gas, condensing the arsenic in the flue gas, and then using a bag filter to collect the arsenic. CN103961790 B discloses a method that uses small droplets generated by airflow and liquid flow to spray into high-temperature arsenic-containing flue gas to cool the flue gas, causing As₂O₃ to condense into solid particles, which are then collected by an arsenic recovery system.

[0004] These methods focus on the condensation and capture of gaseous arsenic. However, during flue gas condensation, components such as copper, lead, and zinc react with As₂O₃ to form arsenates, thus failing to solve the problem of separating arsenic from valuable metals. Therefore, suppressing the formation of arsenates in flue gas through phase regulation is key to achieving the separation and recovery of arsenic from valuable metals. Summary of the Invention

[0005] To address the problem of difficulty in separating arsenic from arsenic in existing dry arsenic recovery technologies due to arsenate formation, this invention proposes a method for regulating and separating arsenic from valuable metals in smelting flue gas. This method inhibits the formation of arsenates to achieve the separation of As2O3 from valuable metals. After separation, arsenic is captured in the form of As2O3 by existing dry arsenic recovery equipment, while the metals are directly returned to the smelting system in the form of sulfates or oxides. This significantly reduces the generation of arsenic-containing flue gas and saves production costs for enterprises.

[0006] A method for controlling and separating arsenic and valuable metals in smelting flue gas includes: adding chalcopyrite powder to the smelting flue gas for phase control of arsenic, inhibiting the formation of arsenate to separate arsenic and valuable metals, wherein the amount of chalcopyrite powder added is 2% to 70% of the total mass of arsenic and valuable metals.

[0007] Preferably, the amount of chalcopyrite powder added is 60-70% of the total mass of arsenic and valuable metals.

[0008] Preferably, the particle size of the chalcopyrite powder is <0.5 mm.

[0009] Preferably, the reaction temperature is 400–800℃. The reaction temperature can be understood as the temperature at which the smelting flue gas reacts with the chalcopyrite powder. In actual production, the temperature of the directly emitted smelting flue gas is above 1000℃. After waste heat recovery, the temperature is adjusted to below 800℃, allowing it to react directly with the chalcopyrite powder, thereby achieving phase control of arsenic.

[0010] Preferably, the reaction temperature is 600–700°C.

[0011] The key technology of this invention lies in utilizing the reaction of sulfides and metal oxides in flue gas, along with the resulting arsenates, under appropriate temperature conditions. On one hand, the metal oxides are converted into sulfates to inhibit further reaction with As₂O₃. On the other hand, the sulfides dissociate the already formed arsenates, selectively converting arsenic into volatile arsenic trioxide, thus achieving the separation of arsenic trioxide from valuable metals. In a smelting atmosphere of 400–800°C, the following reactions mainly occur to regulate the separation of arsenic from valuable metals using chalcopyrite powder:

[0012] 7CuFeS2+CuO+28O2(g)=8CuSO4+Fe2(SO4)3+Fe3O4+Fe2O3+3SO2(g)

[0013] 7CuFeS2+Cu3(AsO4)2+28O2=10CuSO4+As2O3(g)+Fe2O3+Fe3O4+Fe2(SO4)3+SO2(g)

[0014] As can be seen from the above reaction, copper is mainly converted into stable metal sulfates, while iron is converted into oxides and sulfates, thereby inhibiting the formation of arsenate and achieving the separation of arsenic trioxide from valuable metals.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] This invention regulates the phase composition of arsenic in smelting flue gas by using chalcopyrite powder, inhibiting the formation of arsenates and achieving the separation of arsenic from valuable metals in smelting flue gas. Combined with existing dry arsenic removal equipment, it can significantly improve the arsenic recovery rate, reduce the generation of arsenic-containing dust, and save production costs for enterprises. Attached Figure Description

[0017] Figure 1 This is a diagram showing the separation effect of arsenic and valuable metals under different chalcopyrite dosages in Example 1.

[0018] Figure 2 This is a diagram showing the separation effect of arsenic and valuable metals at different temperatures in Example 2.

[0019] Figure 3 This is a diagram showing the separation effect of arsenic and valuable metals under different atmospheres in Example 3.

[0020] Figure 4 This is a diagram showing the separation effect of arsenic and valuable metals under different O2 and SO2 ratios in Example 3.

[0021] Figure 5 This is a diagram showing the separation effect of arsenic and different valuable metals under the control of chalcopyrite in Example 4.

[0022] Figure 6 This is a comparison chart showing the effect of using chalcopyrite and a reference regulator to control the separation of arsenic and valuable metals in flue gas under the same temperature and atmosphere. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to specific embodiments and accompanying drawings. It should be noted that the reagents, raw materials, instruments, and equipment involved in the present invention are all commercially available products.

[0024] Example 1

[0025] The separation of arsenic and valuable metals in smelting flue gas was regulated under different chalcopyrite dosages. In this example, the mass ratio of CuO to As₂O₃ was 2:1, and the gaseous components in the constant smelting flue gas were 20% O₂, 25% SO₂, 10% CO₂, and 45% N₂. The reaction was carried out at 600℃ for 60 minutes, and the reaction tail gas was discharged after two stages of washing. Figure 1 As shown, the separation rate of arsenic from valuable metals increases with the increase of chalcopyrite addition (2%–70%), and finally reaches a peak at 70% (92.9%).

[0026] Example 2

[0027] Arsenic separation from valuable metals was regulated in chalcopyrite smelting flue gas at different temperatures. The constant gaseous composition of the smelting flue gas was 20% O2, 25% SO2, 10% CO2, and 45% N2, with a CuO to As2O3 mass ratio of 2:1. The chalcopyrite additive dosage was 60%, and the reaction time was 60 minutes. The tail gas was discharged after two-stage washing. Figure 2 As shown, the separation rate of arsenic from valuable metals increases with increasing temperature in the range of 400–700℃, reaching 52.7% at 400℃ and peaking at 90.4% at 700℃, which is 1.7 times that at 400℃. When the temperature is further increased to 800℃, the separation rate of arsenic from valuable metals decreases to 86.7%.

[0028] Example 3

[0029] The separation of arsenic from valuable metals in smelting flue gas was controlled by chalcopyrite under different atmospheres. Specifically, chalcopyrite was used to inhibit the reaction between As₂O₃ and metal oxides in flue gas at high temperatures under different atmospheres to separate arsenic. In this example, the mass ratio of CuO to As₂O₃ was 2:1, the dosage of chalcopyrite as the control agent was 60%, the reaction was carried out at 600℃ for 60 min, and the reaction tail gas was discharged after two-stage washing. N₂ was used as the equilibrium gas in the reaction atmosphere, and the separation effect of arsenic from valuable metals was determined under different compositions and ratios of O₂, SO₂, and CO₂ atmospheres.

[0030] like Figure 3 As shown, different atmospheric conditions affected the ability of chalcopyrite to control the separation of arsenic from valuable metals. Nitrogen (100% N2), SO2 (25% SO2 + 75% N2), and CO2 (10% CO2 + 90% N2) atmospheres were favorable for controlling the separation of arsenic from valuable metals in chalcopyrite, with separation rates of 95.6%, 97.9%, and 95.1%, respectively. The addition of oxygen inhibited the separation of arsenic from valuable metals in chalcopyrite, with separation rates of 81.2%, 89.7%, and 88.2% for the three oxygen-containing atmospheres: 20% O2 + 80% N2, 20% O2 + 25% SO2 + 55% N2, and 20% O2 + 25% SO2 + 10% CO2 + 45% N2, respectively.

[0031] like Figure 4 As shown in Figure a, with a constant smelting flue gas composition of 25% SO2, 10% CO2, and N2 as the equilibrium gas, the separation rate of arsenic and valuable metals regulated by chalcopyrite significantly decreases with increasing O2 concentration (0%–50%). Without O2, the separation rate of arsenic and valuable metals is 98.8%. At a 50% O2 concentration, the separation rate decreases to 38.4%.

[0032] like Figure 4As shown in b, with a constant gaseous composition of 20% O2, 10% CO2, and N2 as the equilibrium gas in the smelting flue gas, the separation rate of arsenic and valuable metals regulated by chalcopyrite increases with increasing SO2 concentration (0%–55%). Without SO2, the separation rate is 86.9%. At a SO2 concentration of 55%, the separation rate increases to 90.7%.

[0033] Example 4

[0034] Chalcopyrite was used to regulate the separation of arsenic from different valuable metals. The gaseous components of the smelting flue gas were 20% O2, 25% SO2, 10% CO2, and 45% N2. The mass ratio of CuO, PbO, ZnO, and As2O3 was 2:1. The dosage of chalcopyrite as the regulator was 60%. The reaction was carried out at 600℃ for 60 minutes, and the tail gas was discharged after two stages of scrubbing. Figure 5 As shown, after chalcopyrite regulation, the separation rates of arsenic from copper, lead, and zinc were 88.2%, 90.1%, and 92.3%, respectively, indicating that chalcopyrite can effectively regulate the separation of the three valuable metals from arsenic.

[0035] Comparative Example 1

[0036] FeS was used to regulate and separate arsenic from valuable metals in smelting flue gas, with an addition amount of 60%, and the mass ratio of CuO to As₂O₃ was 2:1. Other reaction conditions were the same as in Example 4. Figure 6 As shown, chalcopyrite (88.2%) is about 1.9 times more effective than FeS (46.2%) in controlling the separation of arsenic and valuable copper in flue gas, indicating that chalcopyrite is significantly superior to FeS.

[0037] Comparative Example 2

[0038] CuS was used to regulate and separate arsenic from valuable metals in smelting flue gas, with an addition amount of 60%. The mass ratio of CuO to As₂O₃ was 2:1, and other reaction conditions were the same as in Example 4. Figure 6 As shown, chalcopyrite (88.2%) is about 2.3 times more effective than CuS (38.8%) in controlling the separation of arsenic and valuable metals in flue gas, indicating that chalcopyrite is significantly superior to CuS.

[0039] Comparative Example 3

[0040] (NH4)2SO4 was used to control and separate arsenic from valuable metals in smelting flue gas, with an addition amount of 60%, a CuO to As2O3 mass ratio of 2:1, and other reaction conditions consistent with Example 4. Figure 6 As shown, (NH4)2SO4 (77.4%) was less effective than chalcopyrite (88.2%) in controlling the separation of arsenic from valuable metals, while chalcopyrite was significantly better than (NH4)2SO4.

[0041] This invention verifies, through experiments simulating smelting flue gas, that chalcopyrite powder can regulate the phase composition of arsenic in smelting flue gas and inhibit the formation of arsenates.

[0042] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for regulating and separating arsenic from valuable metals in smelting flue gas, characterized in that, include: Chalcopyrite powder is added to smelting flue gas to regulate the phase composition of arsenic, inhibit the formation of arsenate to separate arsenic and valuable metals. Arsenic is captured in the form of As2O3 by existing dry arsenic collection equipment. The amount of chalcopyrite powder added is 2% to 70% of the total mass of arsenic and valuable metals. The valuable metals are copper, lead, and zinc. The reaction temperature is 400-800℃. The particle size of the chalcopyrite powder is <0.5mm.

2. The method for regulating and separating arsenic and valuable metals in smelting flue gas according to claim 1, characterized in that, The amount of chalcopyrite powder added is 60-70% of the total mass of arsenic and valuable metals.

3. The method for regulating and separating arsenic and valuable metals in smelting flue gas according to claim 2, characterized in that, The reaction temperature is 600~700℃.

Images