Method for low-temperature electric field enhanced selective adsorption of selenium and mercury

Abstract

The present application belongs to the technical field of waste resource utilization, and particularly relates to a method for selectively adsorbing selenium and mercury by low-temperature electric field strengthening. The method provided by the present application can efficiently reduce and selectively deeply adsorb selenium and mercury, remove selenium and mercury in smelting flue gas of an oxygen-rich side-blown furnace after waste heat recovery and denitration and dust removal, has a high comprehensive recovery rate of selenium and mercury, does not produce waste residue, and can continuously produce. The present application uses sulfur dioxide as a reducing agent to reduce selenium and its compounds in smelting flue gas of an oxygen-rich side-blown furnace after waste heat recovery and denitration and dust removal, selectively adsorbs under a high-voltage electric field, and forms a selenium and mercury-containing product layer at an anode. The present application uses an electric field to adsorb selenium and mercury, does not need to consume additional adsorption materials, has a simple process, low cost, and good economic benefits. The present application uses an electric field adsorption process to avoid the entry of selenium and mercury into a downstream acid-making system, thereby reducing the impurity content in finished sulfuric acid, enabling tail gas to be discharged in compliance with standards, and having good environmental benefits.

Description

Technical Field

[0001] This invention belongs to the field of waste resource utilization technology, specifically relating to a method for selective adsorption of selenium and mercury by low-temperature electric field enhancement. Background Technology

[0002] Currently, the main processing techniques for extracting selenium and mercury from selenium- and mercury-containing hazardous waste are pyrometallurgical and hydrometallurgical methods.

[0003] The pyrometallurgical process utilizes the volatility of selenium and mercury in hazardous waste during high-temperature roasting. The selenium and mercury are volatilized, condensed, and enriched. Then, calcium oxide is used to fix the enriched flue dust, removing mercury. The mercury volatilizes as mercury vapor, while the selenium reacts with calcium oxide to form calcium selenite, which remains in the selenium-fixing slag, thus achieving the separation of selenium and mercury. The pyrometallurgical process has high raw material adaptability, but the recovery rate of selenium and mercury is low.

[0004] Hydrometallurgical processes include potassium chlorate / hydrochloric acid leaching, sodium chlorate / sulfuric acid leaching, and sodium sulfide / sodium hydroxide leaching. The potassium chlorate / hydrochloric acid and sodium chlorate / sulfuric acid leaching methods convert selenium and mercury in selenium- and mercury-containing solid waste into soluble selenite and mercuric chloride, which are then sequentially reduced to obtain elemental selenium and mercury. The sodium sulfide / sodium hydroxide leaching method first neutralizes the acidic sludge to neutral, then uses sodium sulfide as the leaching agent, followed by displacement and reduction to achieve the extraction and separation of selenium and mercury. Hydrometallurgical processes offer high selenium and mercury leaching rates and low energy consumption, but generate large amounts of waste residue such as gypsum slag.

[0005] Chinese patent CN114622097A discloses a method for value-added treatment of acid sludge, comprising four steps: lead value-added, mercury value-added, selenium value-added, and tailings treatment. It employs wet and pyrometallurgical processes to treat mercury-containing acid sludge, achieving safe disposal while separating lead, selenium, and mercury. Both high-lead slag and crude selenium can be valued, increasing the mercury valuation factor, thus achieving value-added treatment of hazardous acid sludge. This invention features a short lead-mercury-selenium separation process, and the lead-containing slag after mercury and selenium extraction can be directly returned to the system; however, the recovery rate is low. Summary of the Invention

[0006] The purpose of this invention is to provide a method for selective adsorption of selenium and mercury using a low-temperature electric field enhanced by the method. The method provided by this invention has a high selenium and mercury recovery rate and does not generate waste residue.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for selective adsorption of mercury selenide using a low-temperature electric field enhanced by the following steps:

[0009] After the smelting flue gas from the oxygen-enriched side-blown furnace, which has undergone waste heat recovery and denitrification and dust removal, is cooled, a high-voltage electric field is applied to obtain a selenium-mercury product layer at the anode.

[0010] Preferably, the voltage of the high-voltage electric field is 60-70kV, the current is 150-200mA, and the temperature inside the field is 35-55℃.

[0011] Preferably, the final cooling temperature is 35–55°C.

[0012] Preferably, the negative pressure at the inlet of the high-voltage electric field of the oxygen-enriched side-blown furnace smelting flue gas after waste heat recovery and denitrification and dust removal is -4000 to -7000 Pa, and the pressure difference between the negative pressure at the inlet of the high-voltage electric field and the negative pressure at the outlet of the high-voltage electric field is 200 to 300 Pa.

[0013] Preferably, the flow rate of the oxygen-enriched side-blown furnace smelting flue gas after waste heat recovery and denitrification / dust removal is 7000–15000 m³ / h. 3 / h, the operating gas velocity in the high-voltage electric field is 0.5~1.5m / s.

[0014] Preferably, the oxygen-enriched side-blown furnace smelting flue gas after waste heat recovery and denitrification and dust removal includes elemental selenium, mercuric oxide, mercury, mercuric sulfate, selenium dioxide, selenic acid, selenite, moisture, sulfur dioxide, sulfur trioxide and sulfuric acid.

[0015] Preferably, the volume concentration of sulfur dioxide in the oxygen-enriched side-blown furnace smelting flue gas after waste heat recovery and denitrification is 6.0-7.5%, and the total mercury concentration is 50-300 mg / m³. 3 The total selenium concentration is 80–400 mg / m³. 3 .

[0016] Preferably, after obtaining the selenium-mercury product layer, a post-processing is further included, wherein when the thickness of the selenium-mercury product layer reaches 1 to 10 mm, the selenium-mercury product layer is sequentially subjected to high-pressure water washing and separation.

[0017] Preferably, the device for applying the high-voltage electric field includes an anode tube bundle and an cathode; the anode tube bundle is a carbon fiber reinforced composite material; and the cathode is a serrated Hastelloy alloy and a PP weight.

[0018] Preferably, the dust concentration at the inlet of the high-voltage electric field of the oxygen-enriched side-blown furnace smelting flue gas after waste heat recovery and denitrification is not higher than 400 mg / m³. 3 The dust concentration at the high-voltage electric field outlet is less than 10 mg / m³. 3 .

[0019] This invention provides a method for the selective adsorption of selenium and mercury using a low-temperature electric field enhanced by the process. The method efficiently reduces and selectively and deeply adsorbs selenium and mercury, removing them from the flue gas of an oxygen-enriched side-blown furnace after waste heat recovery and denitrification / dust removal. The overall recovery rate of selenium and mercury is high, with both selenium and mercury recovery rates exceeding 98%. No waste residue is generated, and continuous production is possible. This invention utilizes sulfur dioxide as a reducing agent to reduce selenium and its compounds in the flue gas of an oxygen-enriched side-blown furnace after waste heat recovery and denitrification / dust removal. Selenium and mercury are selectively adsorbed under a high-voltage electric field, forming a selenium- and mercury-containing product layer at the anode. This invention employs electric field adsorption of selenium and mercury, eliminating the need for additional adsorption materials. The process is simple, low-cost, and offers good economic benefits. Furthermore, the electric field adsorption process prevents selenium and mercury from entering the downstream sulfuric acid production system, thereby reducing the impurity content in the finished sulfuric acid and ensuring that the exhaust gas meets emission standards, resulting in significant environmental benefits.

[0020] This invention employs an oxygen-enriched side-blown process to treat hazardous waste containing selenium and mercury. Although some selenium and mercury are recovered from the flue gas of the oxygen-enriched side-blown furnace after denitrification, electrostatic dust removal, and desulfurization during production, the removal rate of selenium and mercury in the ultrafine dust state is low. This invention solves the problem of adsorption and recovery of ultrafine selenium and its compounds and mercury and its compounds by selectively reducing and adsorbing selenium and mercury through electric field enhancement. It deeply removes selenium and mercury before acid production, thereby reducing the impurity content in sulfuric acid. Detailed Implementation

[0021] This invention provides a method for selective adsorption of mercury selenide using a low-temperature electric field enhanced by the following steps:

[0022] After the smelting flue gas from the oxygen-enriched side-blown furnace, which has undergone waste heat recovery and denitrification and dust removal, is cooled, a high-voltage electric field is applied to obtain a selenium-mercury product layer at the anode.

[0023] In this invention, the oxygen-enriched side-blown furnace smelting flue gas after waste heat recovery and denitrification preferably includes elemental selenium, mercury oxide, mercury, mercury sulfate, selenium dioxide, selenic acid, selenite, moisture, sulfur dioxide, sulfur trioxide, and sulfuric acid; the volume concentration of sulfur dioxide in the oxygen-enriched side-blown furnace smelting flue gas after waste heat recovery and denitrification is preferably 6.0-7.5%, more preferably 6.5-7.2%, and even more preferably 6.8-7.0%, and the total mercury concentration (mercury and its compounds) is preferably 50-300 mg / m³. 3 More preferably 100–250 mg / m³ 3 More preferably 150–200 mg / m³ 3 The total selenium concentration (selenium and its compounds) is preferably 80–400 mg / m³. 3 More preferably 160–300 mg / m³ 3 More preferably 220–270 mg / m³ 3 .

[0024] In this invention, the flow rate of the oxygen-enriched side-blown furnace smelting flue gas after waste heat recovery and denitrification / dust removal is preferably 7000–15000 m³ / h. 3 / h, more preferably 9000~13000m 3 / h, further preferably 10000~11000m 3 The operating gas velocity within the high-voltage electric field is preferably 0.5–1.5 m / s, more preferably 0.7–1.2 m / s, and even more preferably 0.9–1.1 m / s.

[0025] In this invention, the negative pressure at the inlet of the high-voltage electric field of the oxygen-enriched side-blown furnace smelting flue gas after waste heat recovery and denitrification and dust removal is preferably -4000 to -7000 Pa, more preferably -4500 to -6500 Pa, and even more preferably -5000 to -6000 Pa. The pressure difference between the negative pressure at the inlet of the high-voltage electric field and the negative pressure at the outlet of the high-voltage electric field is preferably 200 to 300 Pa, more preferably 220 to 280 Pa, and even more preferably 240 to 260 Pa.

[0026] In this invention, the dust concentration at the inlet of the high-voltage electric field of the oxygen-enriched side-blown furnace smelting flue gas after waste heat recovery and denitrification is preferably not higher than 400 mg / m³. 3 More preferably not exceeding 300 mg / m 3 Further optimization of 200mg / m 3 The dust concentration at the outlet of the high-voltage electric field is preferably below 10 mg / m³. 3 More preferably below 7 mg / m 3 Further preferred concentrations are below 5 mg / m³. 3 The total demisting and dust removal efficiency is preferably not less than 99%, and more preferably not less than 99.5%.

[0027] In this invention, the final cooling temperature is preferably 35–55°C, more preferably 40–50°C, and even more preferably 45°C. This invention cools the flue gas from an oxygen-enriched side-blown furnace, after waste heat recovery and denitrification / dust removal, to the target temperature through cooling.

[0028] In this invention, the voltage of the high-voltage electric field is preferably 60-70 kV, more preferably 62-68 kV, and even more preferably 64-66 kV; the current of the high-voltage electric field is preferably 150-200 mA, more preferably 170-190 mA, and even more preferably 180 mA; the temperature of the high-voltage electric field is preferably 35-55°C, more preferably 40-50°C, and even more preferably 45°C. By setting the high-voltage electric field at the above-mentioned temperatures, this invention ensures that the temperature of the cooled oxygen-enriched side-blown furnace smelting flue gas remains constant at the target temperature, which is beneficial for the high-voltage electric field to adsorb selenium and mercury from the oxygen-enriched side-blown furnace smelting flue gas.

[0029] In this invention, the device for applying a high-voltage electric field preferably includes an anode tube bundle and an cathode; the anode tube bundle is preferably a carbon fiber reinforced composite material; the cathode is preferably a serrated Hastelloy alloy and a PP weight. In this invention, under the action of a high-voltage electric field, the gas surrounding the cathode ionizes to produce negative gas ions, which combine with selenium and mercury-containing droplets and dust particles, thereby charging the droplets and dust particles. The charged selenium and mercury-containing droplets and dust particles, under the action of the electric field, rapidly reach the inner wall of the anode tube bundle and release their charge, forming a selenium-mercury-containing product layer on the inner wall of the anode tube bundle.

[0030] In this invention, the device for applying the high-voltage electric field is preferably an electrostatic precipitator; the electrostatic precipitator is preferably equipped with an insulating box. This invention utilizes an electrostatic precipitator to adsorb selenium and mercury-containing flue gas from an oxygen-enriched side-blown furnace, obtaining flue gas after the removal of selenium and mercury.

[0031] In this invention, after obtaining the selenium-mercury-containing product layer, post-processing is preferably included. The post-processing is preferably performed by sequentially subjecting the selenium-mercury-containing product layer to high-pressure water washing and separation when the thickness of the selenium-mercury-containing product layer reaches 1-10 mm. This invention separates the selenium-mercury-containing products stripped off by high-pressure water washing, extracting elemental selenium and mercury. The process generates no waste residue, produces high-purity products, and has high separation efficiency.

[0032] In this invention, the preferred thickness of the selenium-mercury product layer is 1 to 10 mm, more preferably 2 to 9 mm, and even more preferably 3 to 8 mm.

[0033] In this invention, the selenium-mercury product is preferably subjected to pressure filtration after high-pressure water rinsing; the pore size of the pressure filter is preferably 600-1000 mesh, more preferably 700-900 mesh, the pressure is preferably 0.3-0.9 MPa, more preferably 0.4-0.8 MPa, and the pressure holding time is preferably 0.5-12 h, more preferably 1-10 h.

[0034] To further illustrate the present invention, the following detailed description of the embodiments is provided in conjunction with the present invention, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0035] Example 1

[0036] After waste heat recovery and denitrification / dust removal, the temperature of the flue gas from the oxygen-enriched side-blown furnace is reduced to 45℃, and the flue gas flow rate is 11000 m³ / h. 3 / h, SO2 concentration range 6.0%, total mercury concentration range 70mg / m³ 3 Total selenium concentration range 230 mg / m³ 3 Inlet dust concentration ≤340mg / m³ 3 The dust concentration at the outlet is less than 7 mg / m³. 3 ;

[0037] The electrostatic precipitator operates at an electric field voltage of 60kV and a current of 150mA. The flue gas inlet negative pressure is -5800Pa, the equipment pressure difference is 250Pa, and the operating gas velocity is 1.0m / s. The total demisting and dust removal efficiency is greater than or equal to 99%. A selenium-mercury product layer is obtained, which is washed with high-pressure water, collected, filtered, and separated to obtain the selenium-mercury product. Its selenium mass content is 73.99%, mercury content is 19.44%, and moisture content is 23.56%. The mercury recovery rate is 99%, and the selenium recovery rate is 99%.

[0038] Example 2

[0039] After waste heat recovery and denitrification / dust removal, the temperature of the flue gas from the oxygen-enriched side-blown furnace is reduced to 45℃, and the flue gas flow rate is 11000 m³ / h. 3 / h, SO2 concentration range 6.5%, total mercury concentration range 180mg / m³ 3 Total selenium concentration range 90 mg / m³ 3 Inlet dust concentration ≤310mg / m³ 3 The dust concentration at the outlet is less than 5 mg / m³. 3 ;

[0040] The electrostatic precipitator operates at an electric field voltage of 65kV and a current of 180mA. The flue gas inlet negative pressure is -5800Pa, the equipment pressure difference is 200Pa, and the operating gas velocity is 1.2m / s. The total demisting and dust removal efficiency is greater than or equal to 99%. A selenium-mercury product layer is obtained, which is washed with high-pressure water, collected, filtered, and separated to obtain the selenium-mercury product. Its selenium mass content is 28.20%, mercury content is 53.05%, and moisture content is 36.35%. The mercury recovery rate is 99%, and the selenium recovery rate is 98%.

[0041] Example 3

[0042] After waste heat recovery and denitrification / dust removal, the temperature of the flue gas from the oxygen-enriched side-blown furnace is reduced to 45℃, and the flue gas flow rate is 11000 m³ / h. 3 / h, SO2 concentration range 7%, total mercury concentration range 50mg / m³ 3 Total selenium concentration range 360 ​​mg / m³ 3 Inlet dust concentration ≤430mg / m³ 3 The dust concentration at the outlet is less than 5 mg / m³. 3 ;

[0043] The electrostatic precipitator operates at an electric field voltage of 65kV and a current of 180mA. The flue gas inlet negative pressure is -5800Pa, the equipment pressure difference is 300Pa, and the operating gas velocity is 1.6m / s. The total demisting and dust removal efficiency is greater than or equal to 99%. A selenium-mercury product layer is obtained, which is washed with high-pressure water, collected, filtered, and separated to obtain the selenium-mercury product. Its selenium mass content is 46.56%, mercury content is 6.25%, and moisture content is 51.80%. The mercury recovery rate is 98%, and the selenium recovery rate is 99%.

[0044] As can be seen from the above embodiments, the method provided by the present invention efficiently reduces and selectively and deeply adsorbs selenium and mercury, removing selenium and mercury from the oxygen-enriched side-blown furnace smelting flue gas after waste heat recovery and denitrification and dust removal. The comprehensive recovery rate of selenium and mercury is high, no waste residue is generated, no additional adsorption materials are required, the cost is low, and it has good economic and environmental benefits.

[0045] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for selectively adsorbing mercury selenide using a low-temperature electric field enhanced by the following steps: After the smelting flue gas from the oxygen-enriched side-blown furnace, which has undergone waste heat recovery and denitrification and dust removal, is cooled, a high-voltage electric field is applied to obtain a selenium-mercury product layer at the anode. The voltage of the high-voltage electric field is 60~70kV, the current is 150~200mA, and the temperature inside the field is 35~55℃. The oxygen-enriched side-blown furnace smelting flue gas after waste heat recovery and denitrification and dust removal includes elemental selenium, mercuric oxide, mercury, mercuric sulfate, selenium dioxide, selenic acid, selenite, moisture, sulfur dioxide, sulfur trioxide and sulfuric acid. The sulfur dioxide volume concentration in the flue gas from the oxygen-enriched side-blown furnace, after waste heat recovery and denitrification / dust removal, is 6.0-7.5%, and the total mercury concentration is 50-300 mg / m³. 3 The total selenium concentration is 80~400 mg / m³ 3 ; The device for applying a high-voltage electric field includes an anode tube bundle and an cathode; the anode tube bundle is a carbon fiber reinforced composite material. The cathode is a serrated Hastelloy alloy and a PP weight.

2. The method according to claim 1, characterized in that, The final temperature of the cooling is 35~55℃.

3. The method according to claim 1, characterized in that, The negative pressure at the inlet of the high-voltage electric field of the oxygen-enriched side-blown furnace smelting flue gas after waste heat recovery and denitrification and dust removal is -4000~-7000Pa, and the pressure difference between the negative pressure at the inlet of the high-voltage electric field and the negative pressure at the outlet of the high-voltage electric field is 200~300Pa.

4. The method according to claim 1 or 3, characterized in that, The flow rate of the oxygen-enriched side-blown furnace smelting flue gas after waste heat recovery and denitrification / dust removal is 7000~15000 m³ / h. 3 / h, the operating gas velocity in the high-voltage electric field is 0.5~1.5m / s.

5. The method according to claim 1, characterized in that, After obtaining the selenium-mercury product layer, a post-processing is also included, wherein when the thickness of the selenium-mercury product layer reaches 1~10mm, the selenium-mercury product layer is sequentially subjected to high-pressure water washing and separation.

6. The method according to claim 1 or 3, characterized in that, The dust concentration at the high-voltage electric field inlet of the oxygen-enriched side-blown furnace smelting flue gas after waste heat recovery and denitrification is no higher than 400 mg / m³. 3 The dust concentration at the high-voltage electric field outlet is less than 10 mg / m³. 3 .