Arsenic-containing flue gas purification and arsenic resource high-value recovery process

Abstract

The invention discloses an arsenic-containing flue gas purification and arsenic resource high-value recovery process which comprises the following steps: step 1, flue gas pretreatment: removing large-particle smoke dust through a dust remover; 2, waste heat recovery, wherein the high-temperature flue gas is introduced into a waste heat boiler to recover flue gas waste heat; 3, spray cooling: introducing the flue gas into a spray tower, reversely atomizing, spraying water, absorbing heat, and condensing to form crystals; step 4, crystal stripping: scraping, stripping and collecting the crystals through a mechanical scraper device to obtain coarse arsenic trioxide crystals; step 5, settling and slow cooling: pouring the residual gaseous arsenic trioxide into a cooling settling tank by a negative pressure fan for slow cooling settling; step 6, dissolving and recrystallizing: adding deionized water into the crystal, heating for dissolving, filtering the solution after impurity precipitation, carrying out solid-liquid separation, cooling and recrystallizing to obtain a high-purity arsenic trioxide crystal; according to the arsenic trapping device, efficient trapping of arsenic is achieved through crystallization on the wall of the spray tower and slow cooling of the settling tank, crystals are stripped in real time through the mechanical scraper, and the stubborn disease that equipment is scaled and blocked is radically treated.

Description

Technical Field

[0001] This invention relates to the field of equipment technology, and in particular to a process for purifying arsenic-containing flue gas and recovering high-value arsenic resources. Background Technology

[0002] Arsenic is a toxic element widely found in non-ferrous metal ores. During pyrometallurgical processes, arsenic enters the flue gas as gaseous arsenic trioxide. Arsenic-containing flue gas not only poses a serious threat to the atmospheric environment but also wastes arsenic resources. Therefore, developing technologies that can effectively purify flue gas and achieve high-value recovery of arsenic resources is crucial. Arsenic-containing waste gas mainly originates from multiple industrial production sectors, including but not limited to the metallurgical industry: particularly in the smelting of non-ferrous metals such as copper, lead, and zinc, arsenic is often present in the ores, releasing large amounts of arsenic-containing waste gas upon heating; the semiconductor manufacturing industry: the use of arsenic compounds as dopants in semiconductor chip manufacturing may generate arsenic-containing waste gas, such as arsine; pesticide and chemical production: the production and application of some arsenic-containing pesticides, as well as the manufacturing of chemical products, may generate arsenic-containing waste gas; and coal combustion: coal contains trace amounts of arsenic, which can be converted into a gaseous form and released into the atmosphere during combustion. The arsenic compounds in these waste gases are highly toxic, and long-term exposure can have serious effects on human health, including damage to the skin, liver, kidneys, and nervous system, and an increased risk of cancer.

[0003] Currently, the treatment of arsenic-containing flue gas mainly includes dry, semi-dry, and wet processes. Dry processes primarily use high-temperature electrostatic precipitators and bag filters to capture arsenic-containing dust, which is then treated separately. While simple, this method suffers from low arsenic recovery rates and difficulty in effectively separating arsenic from other heavy metals, resulting in low-purity arsenic products that cannot be utilized for high-value purposes and can only be disposed of as hazardous waste in landfills, posing a significant environmental risk. Wet processes are currently widely used, using water or alkaline solutions to wash the flue gas, allowing gaseous arsenic oxides to be absorbed into the liquid phase. Existing wet processes easily generate large amounts of difficult-to-treat arsenic-containing wastewater, posing a risk of secondary pollution, and the arsenic product purity is low. Dry dust removal technology, on the other hand, has low capture efficiency for gaseous arsenic and limited recovery rates. Existing technologies generally suffer from problems such as difficulty in balancing arsenic recovery rates and product purity, system blockage due to arsenic crystallization, high risk of secondary pollution, and low resource utilization. Therefore, this invention proposes a process for arsenic-containing flue gas purification and high-value arsenic resource recovery to address the problems existing in the prior art. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to propose a process for purifying arsenic-containing flue gas and recovering arsenic resources at a high value. This process achieves efficient arsenic recovery through two-stage collection: crystallization on the spray tower wall and slow cooling in a settling tank. Real-time crystal removal via mechanical scrapers fundamentally solves the persistent problem of scaling and clogging in traditional condensation equipment, ensuring continuous and stable operation. Through purification steps involving dissolution, filtration, and programmed cooling recrystallization, impurities such as metal oxides are effectively removed, successfully converting low-value arsenic-containing flue ash into high-purity arsenic trioxide that can be directly utilized as a resource, thus achieving a balance between pollution control and high-value resource recovery.

[0005] To achieve the objectives of this invention, the invention is implemented through the following technical solution: a process for purifying arsenic-containing flue gas and recovering high-value arsenic resources, comprising the following steps: Step 1: Flue gas pretreatment, where high-temperature arsenic-containing flue gas is passed through a dust collector to remove large particulate dust. Step 2: Waste heat recovery. High-temperature flue gas is introduced into a waste heat boiler to recover waste heat from the flue gas. Step 3: Spray cooling. The flue gas that has absorbed residual heat in step 2 is passed into a spray tower and sprayed with water in a reverse atomization to absorb heat, so that the gaseous arsenic trioxide in the flue gas condenses into crystals on the inner wall of the spray tower. Step 4: Crystallization and peeling. The crystals condensed in Step 3 are scraped, peeled off and collected by a mechanical scraper device installed on the inner wall of the spray tower to obtain crude arsenic trioxide crystals. Step 5: Slow cooling and settling. The residual gaseous arsenic trioxide is poured into the cooling settling tank by a negative pressure fan for slow cooling and settling. Step 6: Dissolve and recrystallize. Pour the stripped crystals into a sealed reaction vessel, add deionized water, and heat to dissolve. This dissolves the arsenic trioxide in the crystals and precipitates the metal oxide impurities. After the impurities precipitate, filter the solution to separate the solid and liquid phases, then cool and recrystallize to obtain high-purity arsenic trioxide crystals.

[0006] A further improvement is that in step two, the high-temperature flue gas exchanges heat with the water in the waste heat boiler through pipelines, absorbing the waste heat of the flue gas and cooling it to 380-400℃.

[0007] The further improvement is that the spray water pressure in step three is 0.4 MPa, the water mist particle size is less than 30 μm, and the flue gas cooling temperature is reduced from 380℃ to 120-140℃.

[0008] A further improvement is that the gap between the mechanical scraper device in step four and the inner wall of the spray tower is 0.5-2mm.

[0009] A further improvement is that in step five, the temperature of the flue gas in the cooling settling tank is slowly reduced to 110°C.

[0010] A further improvement is that: in step five, the cooling settling tank is provided with an outer jacket, and a cooling medium circulates within the jacket.

[0011] The further improvement is that the solid-liquid ratio of crystallization to deionized water in step six is ​​1:3-1:10 (w / v), and the cooling rate of the cooling recrystallization is 0.1-0.5℃ / min.

[0012] The beneficial effects of this invention are as follows: This invention combines the advantages of direct product recovery in dry processes and deep purification in water processes through an integrated dry-wet process. Specifically: 1. High-efficiency arsenic recovery is achieved through two-stage collection: crystallization on the spray tower wall and slow cooling in the settling tank; 2. Real-time crystal stripping by mechanical scrapers fundamentally solves the problem of scaling and clogging in traditional condensation equipment, ensuring continuous and stable operation; 3. Through purification steps of dissolution, filtration, and programmed cooling recrystallization, impurities such as metal oxides are effectively removed, successfully converting low-value arsenic-containing flue dust into high-purity arsenic trioxide that can be directly utilized as a resource, achieving a unity of pollution control and high-value resource utilization. Attached Figure Description

[0013] Figure 1 This is a flowchart of the steps of the present invention; Figure 2 This is a process flow diagram of the present invention. Detailed Implementation

[0014] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0015] In the copper smelting industry, the treatment of arsenic-containing flue gas has always been a key focus and challenge in the environmental protection field. Arsenic, as a highly toxic element, readily volatilizes into flue gas during high-temperature smelting processes, severely polluting the atmosphere and posing a potential threat to human health. With increasingly stringent environmental regulations, copper smelting companies are exploring efficient and economical technologies for treating arsenic-containing flue gas to achieve green production and sustainable development. During copper smelting, the flue gas generated by smelting furnaces, converters, and refining furnaces typically reaches temperatures between 350-550℃, with dust content as high as 20-50 g / m³, and arsenic primarily in the form of gaseous arsenic trioxide, with concentrations reaching 50-150 mg / m³. This combination of high temperature, high dust, and high arsenic levels places extremely high demands on flue gas treatment equipment. While traditional wet scrubbing technology can remove some arsenic compounds, it easily generates large amounts of arsenic-containing acid, increasing the risk of secondary pollution; dry dust removal technology is difficult to effectively capture gaseous arsenic, resulting in limited treatment effectiveness. In the treatment of arsenic-containing flue gas from copper smelting, the application of intelligent control systems has become crucial for improving treatment efficiency. A copper smelting company has implemented a DCS (Distributed Control System) to monitor flue gas temperature, flow rate, concentration, and other parameters in real time. The system automatically adjusts reagent dosage and fan frequency based on changes in operating conditions to ensure optimal system performance. The treatment of arsenic-containing flue gas from copper smelting is moving towards synergistic treatment and resource utilization. On the one hand, by developing composite reagents and processes, the simultaneous removal of pollutants such as arsenic, sulfur, and fluorine can be achieved, improving treatment efficiency. On the other hand, research on the resource utilization of arsenic will be strengthened, converting recovered arsenic compounds into high-value-added products such as glass clarifying agents and semiconductor materials, achieving a win-win situation for both economic and environmental benefits.

[0016] Based on this, according to Figure 1 , Figure 2 As shown, this embodiment of the invention provides a process for purifying arsenic-containing flue gas and recovering high-value arsenic resources, including the following steps: Step 1: Flue gas pretreatment. High-temperature arsenic-containing flue gas is passed through a dust collector to remove large particulate matter. The high-temperature filter element in the dust collector first removes most of the large particulate matter, providing a relatively clean gas source for subsequent waste heat recovery and arsenic recovery processes, and preventing dust from causing wear and blockage to the equipment. The dust collector preferably uses a high-temperature resistant metal bag filter or a ceramic fiber bag filter to adapt to high-temperature flue gas conditions above 350℃ and effectively remove large particulate matter.

[0017] Step two: Waste heat recovery. High-temperature flue gas is introduced into a waste heat boiler to recover its waste heat. Inside the boiler, the high-temperature flue gas exchanges heat with water through pipes, absorbing the waste heat and cooling to 380-400℃. This recovery of flue gas heat for power generation achieves cascaded energy utilization and creates stable temperature inlet conditions for the subsequent spray cooling, effectively preventing premature condensation of arsenic trioxide within the boiler tubes.

[0018] Step 3: Spray cooling. The flue gas, after absorbing residual heat in Step 2, is passed into a spray tower for counter-current atomization and water spraying to absorb heat. This causes gaseous arsenic trioxide in the flue gas to condense into crystals on the inner wall of the spray tower. The spray water pressure is 0.4 MPa, the water mist particle size is less than 30 μm, and the flue gas temperature is reduced from 380℃ to 120-140℃. Through full contact between the water mist and the high-temperature flue gas, a vigorous heat and mass exchange occurs. The rapid cooling brings the gaseous arsenic trioxide to a supersaturated state, and with the metal inner wall of the spray tower as a condensation nucleus, it preferentially condenses and grows on its surface to form a solid crystal layer of a certain thickness. The formed crystals are denser and easier to peel off, avoiding the formation of fine-particle arsenic bloom.

[0019] Step four, crystallization and peeling: A mechanical scraper device installed on the inner wall of the spray tower scrapes, peels off, and collects the crystals that condensed in Step three, obtaining crude arsenic trioxide crystals. The gap between the mechanical scraper device and the inner wall of the spray tower is 0.5 mm. A rotating scraper removes the arsenic trioxide crystals adhering to the inner wall, and the scraped-off flaky or blocky crude arsenic trioxide crystals fall to the bottom of the tower and are periodically discharged. This physical peeling method solves the problem of scaling and cleaning the heat exchange surface in traditional condensation technology, ensuring the long-term stable operation of the system.

[0020] Step 5: Slow cooling and settling. Residual gaseous arsenic trioxide is poured into the cooling settling tank by a negative pressure fan for slow cooling and settling; the temperature of the flue gas slowly decreases to 110°C inside the cooling settling tank. The cooling settling tank has an outer jacket, within which a cooling medium circulates.

[0021] Step Six: Dissolution and Recrystallization. The stripped crystals are poured into a sealed reactor, and deionized water is added and heated to dissolve the arsenic trioxide in the crystals. Heating and stirring at 60-95℃ ensures the arsenic trioxide fully dissolves into the aqueous phase. Impurities such as metal oxides, which are insoluble in hot water, precipitate. After precipitation, the solution is filtered to separate the solid and liquid phases, followed by cooling and recrystallization to obtain high-purity arsenic trioxide crystals. The solid-liquid ratio of crystals to deionized water is 1:5 (w / v), and the cooling rate for recrystallization is 0.5℃ / min. The arsenic trioxide-rich solution is separated from the insoluble impurities by filtration. The resulting clear filtrate is transferred to a programmed cooling crystallizer for slow recrystallization. This method is beneficial for producing large, uniform, and high-purity arsenic trioxide crystals.

[0022] In this arsenic-containing flue gas purification and high-value arsenic resource recovery process, the high-temperature arsenic-containing flue gas undergoes pretreatment in a dust collector with a built-in high-temperature dust removal filter to remove large particles of dust and protect subsequent equipment. Next, the flue gas enters a waste heat boiler, where it is cooled through heat exchange, recovering waste heat for power generation and creating stable conditions for subsequent steps. Subsequently, the cooled flue gas enters a spray tower from the top, where it comes into full contact with counter-current high-pressure fine water mist and is rapidly cooled to 120-140°C, causing gaseous arsenic trioxide to condense on the inner wall of the tower, forming a dense, easily peelable crystal layer. A rotating mechanical scraper device scrapes off and collects the crystals, solving the problem of scaling and clogging. The collected coarse crystals are dissolved in deionized water at a fixed solid-liquid ratio in a closed reaction vessel, allowing arsenic trioxide to enter the solution while metal oxide impurities precipitate. After filtration and separation, the filtrate undergoes slow, programmed cooling and recrystallization to finally obtain a high-purity arsenic trioxide product. Meanwhile, the residual flue gas after spraying enters a jacketed cooling settling tank under negative pressure for slow cooling, further recovering residual arsenic vapor and ensuring a high recovery rate.

[0023] Example 1 A process for purifying arsenic-containing flue gas and recovering high-value arsenic resources includes the following steps: Step 1, flue gas pretreatment: The high-temperature arsenic-containing flue gas (copper smelting flue gas, arsenic content of 21.05%) is first passed through the high-temperature dust removal filter element in the dust collector to remove most of the large particulate dust carried in it.

[0024] Step 2, Waste Heat Recovery: The high-temperature flue gas after the removal of large particulate matter is cooled down to below 400℃ by exchanging heat with water in the waste heat boiler through pipelines.

[0025] Step 3: Spray cooling. The flue gas, after absorbing residual heat in Step 2, is passed into a spray tower for counter-current atomization and water spraying to absorb heat. This causes gaseous arsenic trioxide in the flue gas to condense into crystals on the inner wall of the spray tower. The spray water pressure is 0.4 MPa, the water mist particle size is less than 30 μm, and the flue gas cooling temperature is reduced from 380℃ to 120-140℃. Through full contact between the water mist and the high-temperature flue gas, a vigorous heat and mass exchange occurs. The rapid cooling causes the gaseous arsenic trioxide to reach a supersaturated state, and with the metal inner wall of the spray tower as a condensation nucleus, it preferentially condenses and grows on its surface to form a solid crystal layer of a certain thickness. The formed crystals are denser and easier to peel off, avoiding the formation of fine-particle arsenic frost. The wastewater generated during the spray cooling process, which may contain trace amounts of heavy metals, is introduced into a wastewater tank for centralized sedimentation treatment after spraying. Once the wastewater meets the standards, it is reused or discharged to avoid secondary pollution.

[0026] Step four, crystallization and peeling: A mechanical scraper device installed on the inner wall of the spray tower scrapes, peels off, and collects the crystals that condensed in Step three, obtaining crude arsenic trioxide crystals. The gap between the mechanical scraper device and the inner wall of the spray tower is 0.5 mm. A rotating scraper removes the arsenic trioxide crystals adhering to the inner wall, and the scraped-off flaky or blocky crude arsenic trioxide crystals fall to the bottom of the tower and are periodically discharged. This physical peeling method solves the problem of scaling and cleaning the heat exchange surface in traditional condensation technology, ensuring the long-term stable operation of the system.

[0027] Step 5: Slow cooling and settling. Residual gaseous arsenic trioxide is poured into the cooling settling tank by a negative pressure fan for slow cooling and settling; the temperature of the flue gas slowly decreases to 110°C inside the cooling settling tank. The cooling settling tank has an outer jacket, within which a cooling medium circulates.

[0028] Step Six: Dissolution and Recrystallization. The stripped crystals are poured into a sealed reactor, and deionized water is added and heated to dissolve the arsenic trioxide in the crystals. Heating and stirring at 80°C ensures the arsenic trioxide fully dissolves into the aqueous phase. Impurities such as metal oxides, which are insoluble in hot water, precipitate. After precipitation, the solution is filtered to separate the solid and liquid phases, followed by cooling and recrystallization to obtain high-purity arsenic trioxide crystals. The solid-liquid ratio of crystals to deionized water is 1:5 (w / v), and the cooling rate for recrystallization is 0.5°C / min. Filtration separates the arsenic trioxide-rich solution from the insoluble impurities. The resulting clear filtrate is transferred to a programmed cooling crystallizer for slow recrystallization.

[0029] The analysis showed that the purity of the arsenic trioxide crystals was 99.95%, and the recovery rate was 93.4%.

[0030] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for purifying arsenic-containing flue gas and recovering high-value arsenic resources, characterized in that, Includes the following steps: Step 1: Flue gas pretreatment, where high-temperature arsenic-containing flue gas is passed through a dust collector to remove large particulate dust. Step 2: Waste heat recovery. High-temperature flue gas is introduced into a waste heat boiler to recover waste heat from the flue gas. Step 3: Spray cooling. The flue gas that has absorbed residual heat in step 2 is passed into a spray tower and sprayed with water in a reverse atomization to absorb heat, so that the gaseous arsenic trioxide in the flue gas condenses into crystals on the inner wall of the spray tower. Step 4: Crystallization and peeling. The crystals condensed in Step 3 are scraped, peeled off and collected by a mechanical scraper device installed on the inner wall of the spray tower to obtain crude arsenic trioxide crystals. Step 5: Slow cooling and settling. The residual gaseous arsenic trioxide is poured into the cooling settling tank by a negative pressure fan for slow cooling and settling. Step 6: Dissolve and recrystallize. Pour the stripped crystals into a sealed reaction vessel, add deionized water, and heat to dissolve. This dissolves the arsenic trioxide in the crystals and precipitates the metal oxide impurities. After the impurities precipitate, filter the solution to separate the solid and liquid phases, then cool and recrystallize to obtain high-purity arsenic trioxide crystals.

2. The process for purifying arsenic-containing flue gas and recovering high-value arsenic resources according to claim 1, characterized in that: In step two, the high-temperature flue gas absorbs the waste heat of the flue gas and cools down to 380-400℃ by exchanging heat with the water in the waste heat boiler through pipelines.

3. The process for purifying arsenic-containing flue gas and recovering high-value arsenic resources according to claim 1, characterized in that: In step three, the spray water pressure is 0.4 MPa, the water mist particle size is less than 30 μm, and the flue gas cooling temperature is reduced from 380℃ to 120-140℃.

4. The process for purifying arsenic-containing flue gas and recovering high-value arsenic resources according to claim 1, characterized in that: The gap between the mechanical scraper device in step four and the inner wall of the spray tower is 0.5-2mm.

5. The process for purifying arsenic-containing flue gas and recovering high-value arsenic resources according to claim 1, characterized in that: In step five, the temperature of the flue gas in the cooling settling tank is slowly reduced to 110°C.

6. The process for purifying arsenic-containing flue gas and recovering high-value arsenic resources according to claim 1, characterized in that: In step five, the cooling settling tank is provided with an outer jacket, and a cooling medium circulates within the jacket.

7. The process for purifying arsenic-containing flue gas and recovering high-value arsenic resources according to claim 1, characterized in that: In step six, the solid-liquid ratio of crystallization to deionized water is 1:3-1:10 (w / v), and the cooling rate of the cooling recrystallization is 0.1-0.5℃ / min.

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