Method for deeply purifying and removing impurities before flue gas desulfurization of industrial furnace

Abstract

The invention discloses a method for deeply purifying and removing impurities before flue gas desulfurization of an industrial furnace, which comprises the following steps: introducing sulfur-containing flue gas subjected to dust removal treatment into a wet washing tower; washing the sulfur-containing flue gas with a soluble metal salt solution to form a dilute sulfuric acid solution containing metal salt as an absorption solution; the obtained absorption liquid is in contact with the treated flue gas to be hydrolyzed, arsenic chloride, hydrogen chloride and lead chloride in the flue gas are converted into arsenate, lead ions and chloride ion soluble salt, the arsenate and metal cations in the absorption liquid are subjected to insoluble arsenate precipitation, and the treated flue gas is the purified and impurity-removed high-sulfur flue gas. By means of the method, arsenic, volatile inorganic matter and other pollutants in the sulfur-containing flue gas can be effectively removed and prevented from entering a subsequent desulfurization system, and the concentration of arsenic, chlorine and other pollutants in desulfurization products is effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of flue gas impurity removal, and particularly relates to a method for deep purification and impurity removal before flue gas desulfurization of an industrial furnace. BACKGROUND

[0002] In the production process of industrial furnaces such as metallurgy and chemical industry, a large amount of high-sulfur flue gas is generated due to the oxidation of sulfide minerals; in a high-temperature atmosphere, arsenic, lead, chlorine and other substances in the material volatilize into the flue gas of the industrial furnace, and then sublimate to form heavy metal smoke particles containing arsenic, lead and the like as the temperature decreases, and volatile inorganic pollutants such as hydrogen chloride, arsenic chloride and lead chloride are formed by reaction with chlorine. Because the flue gas of the industrial furnace contains a high concentration of sulfur dioxide and heavy metals such as arsenic and lead, it needs to be treated for pollution control.

[0003] Traditional flue gas desulfurization is mostly ammonia desulfurization and calcium desulfurization. The gaseous pollutants in high-sulfur flue gas sublimate to form particulate matter as the temperature decreases, and the desulfurization pretreatment mostly adopts bag dust removal, electrostatic dust removal and the like, which can achieve efficient capture, collection and removal of particulate matter. However, volatile inorganic substances (hydrogen chloride, arsenic chloride, lead chloride, nitrogen oxides, sulfur dioxide, carbon dioxide and the like) in the flue gas cannot be effectively removed by traditional bag dust removal and electrostatic dust removal, resulting in that volatile inorganic salts, heavy metals such as arsenic and lead enter the desulfurization gypsum or ammonium sulfate, and the inorganic salt impurities and heavy metals in the desulfurization gypsum / by-product ammonium sulfate are high. After the flue gas of a non-ferrous metallurgical fuming furnace is subjected to bag dust removal, the arsenic content in the desulfurization gypsum can reach 2-5%, which is listed as a hazardous solid waste for special supervision, and seriously restricts the subsequent treatment and resource utilization of the desulfurization gypsum.

[0004] Because of the high concentration of heavy metals such as arsenic and lead in the desulfurization gypsum of the flue gas of the industrial furnace, the cost of hazardous solid waste treatment of the enterprise is high, the environmental risk of stacking and storage and transportation is large, and the sustainable development of the enterprise is seriously restricted.

[0005] Therefore, it is necessary to develop a method for deep purification and impurity removal before flue gas desulfurization of an industrial furnace. SUMMARY

[0006] In order to solve the technical problem that volatile inorganic substances in the flue gas are difficult to remove in the prior art, and heavy metals such as arsenic and lead enter the subsequent process, the purpose of the present application is to provide a method for deep purification and impurity removal before flue gas desulfurization of an industrial furnace, which can effectively remove pollutants such as lead, arsenic and volatile inorganic substances in the sulfur-containing flue gas, avoid their entering the subsequent desulfurization system, and effectively reduce the concentration of pollutants such as arsenic and chlorine in the desulfurization product.

[0007] The purpose of the present application is achieved by including the following steps: (1) introducing the sulfur-containing flue gas after dust removal treatment into a wet scrubber; (2) washing the sulfur-containing flue gas with a soluble metal salt solution to form a dilute sulfuric acid solution containing metal salts as the absorption liquid; (3) contacting the absorption liquid obtained in step (2) with the flue gas treated in step (2) to undergo hydrolysis, and converting arsenic chloride, hydrogen chloride, and lead chloride in the flue gas into arsenate, lead ions, and chloride ions, and precipitating insoluble arsenate salts from the arsenate and metal cations in the absorption liquid, so that the treated flue gas is high-sulfur flue gas after impurity removal.

[0008] Preferably, the metal cations in the soluble metal salt solution in step (2) include one or more of iron ions, copper ions, lead ions, and zinc ions, and the mass concentration of the solution is 0.1% to 50%.

[0009] Preferably, the soluble metal salt solution in step (2) is supplemented with an oxidizing agent during use, the oxidizing agent is hydrogen peroxide and / or ozone, and the concentration of the oxidizing agent is 1 mg / L to 500 mg / L.

[0010] Preferably, the pH of the soluble metal salt solution in step (2) is controlled to be 0 to 7.

[0011] Preferably, the wet scrubber is a bubble column, a sieve tray column, a packed column, or a spray tower.

[0012] Preferably, step (3) removes the precipitates in the absorption liquid by solid-liquid separation, and the solid-liquid separation is one or more of gravity sedimentation, centrifugation, and filtration.

[0013] Preferably, step (3) removes the heavy metal ions in the absorption liquid by a chemical precipitation method, a metal displacement method, or an electrodeposition method.

[0014] Advantages of the present application: 1. After the high-sulfur flue gas containing heavy metals in an industrial furnace is washed with a soluble salt solution, sulfur dioxide in the flue gas is absorbed by the soluble salt solution to form an acidic solution; gaseous pollutants such as arsenic chloride, lead chloride, and hydrogen chloride in the flue gas undergo hydrolysis after contacting the acidic absorption liquid to convert into soluble salts such as arsenate, lead ions, and chloride ions, thereby realizing the absorption and removal of volatile pollutants in the flue gas; arsenate and iron ions or copper ions in the absorption liquid precipitate insoluble arsenate salts, which are then removed by solid-liquid separation. 2. The flue gas treated by the method of the present application mainly contains sulfur dioxide, which is removed by entering a subsequent desulfurization system, and the content of impurities such as heavy metals in the obtained desulfurization gypsum or ammonium sulfate is significantly reduced, thereby greatly reducing the environmental risk of solid waste. DETAILED DESCRIPTION

[0015] The present application is further described below with reference to examples, but is not limited in any way by the examples, and any modification or substitution based on the teaching of the present application is within the protection scope of the present application.

[0016] Example 1 A lead-zinc smelting enterprise uses a fuming furnace to smelt sulfide minerals, and the flue gas generated still contains pollutants such as sulfur dioxide, arsenic chloride, lead chloride, and hydrogen chloride after bag + electrostatic dust removal. The method of deep purification and impurity removal before flue gas desulfurization of the industrial furnace of the present embodiment is implemented, including the following steps: (1) introducing the dust removal treated sulfur-containing flue gas into the spray tower; (2) configuring a soluble metal salt solution containing zinc sulfate and lead sulfate, the zinc sulfate solution has a mass concentration of 0.1-5% and a pH of 0-3; washing the sulfur-containing flue gas with the soluble metal salt solution to form a dilute sulfuric acid solution containing metal salts as the absorption liquid; (3) contacting the absorption liquid obtained in step (2) with the flue gas treated in step (2) to undergo hydrolysis, and the arsenic chloride, hydrogen chloride, and lead chloride in the flue gas are converted into arsenate, lead ions, and chloride ions soluble salt; adding hydrogen peroxide to the solution, with a concentration of 50-200 mg / L; the arsenate in the solution reacts with the zinc and lead ions in the absorption liquid to form zinc arsenate and lead arsenate precipitates.

[0017] (4) The treated flue gas is high-sulfur flue gas after purification and impurity removal, the precipitates in the absorption liquid are removed by gravity settling, and the heavy metal ions in the absorption liquid are removed by chemical precipitation; After detection, the contents of arsenic and lead in the tail gas after purification treatment are less than 0.4 and 1 mg / m³ respectively, the removal rate of hydrogen chloride is more than 20%, and the amount of arsenic and lead and the content of chloride salt entering the subsequent flue gas desulfurization system are effectively reduced.

[0018] Example 2 A tin smelting enterprise uses an austenite furnace to smelt sulfide minerals, and the flue gas generated still contains pollutants such as sulfur dioxide, arsenic chloride, and hydrogen chloride after bag dust removal. The method of the present embodiment is implemented, and the method of deep purification and impurity removal before flue gas desulfurization of the industrial furnace of the present embodiment is based on Example 1, and the difference from Example 1 is: step (1) uses a bubble tower; step (2) configures a soluble metal salt solution containing iron sulfate, copper sulfate, zinc sulfate, and lead sulfate, the solution has a mass concentration of 5-20% and a pH of 1-4, and ozone is added to the solution, with a concentration of 1-100 mg / L; step (3) forms iron arsenate precipitate, which is removed by centrifugation, and the heavy metal ions in the absorption liquid are removed by metal displacement; After detection, the content of arsenic in the tail gas after purification treatment is less than 2 mg / m³, and the removal rate of hydrogen chloride is more than 20%, effectively reducing the amount of arsenic and chlorine entering the subsequent flue gas desulfurization system.

[0019] Example 3 A pyrite acid-making enterprise uses a fluidized bed boiler to smelt sulfide minerals. The flue gas produced still contains pollutants such as sulfur dioxide, arsenic chloride, and hydrogen chloride after bag dust removal. According to the method of the present embodiment, the method for deep purification and impurity removal before flue gas desulfurization of industrial furnaces and kilns in the present embodiment is based on Example 1, and the difference from Example 1 is that: step (1) uses a packed tower; step (2) configures a soluble metal salt solution containing ferric sulfate, the solution mass concentration is 0.5-20%, and the pH is 1-3.5. Hydrogen peroxide is added to the solution, and the concentration is 200-500 mg / L; step (3) forms ferric arsenate precipitate, the precipitate is removed by filtration, and the heavy metal ions in the absorption solution are removed by electrodeposition; After detection, the arsenic content in the tail gas after purification treatment is less than 1 mg / m³, and the removal rate of hydrogen chloride is more than 20%, effectively reducing the amount of arsenic and chlorine entering the subsequent flue gas desulfurization system.

[0020] Example 4 A copper smelting enterprise uses an Isa furnace to smelt sulfide minerals. The flue gas produced still contains pollutants such as sulfur dioxide, arsenic chloride, and hydrogen chloride after bag- electrostatic dust removal. According to the method of the present embodiment, the method for deep purification and impurity removal before flue gas desulfurization of industrial furnaces and kilns in the present embodiment is based on Example 1, and the difference from Example 1 is that: step (1) uses a sieve plate tower; step (2) configures a soluble metal salt solution containing copper sulfate, ferric sulfate, and zinc sulfate, the solution mass concentration is 10-50%, and the pH is 1-7. Hydrogen peroxide and ozone are added to the solution, and the concentration is 50-400 mg / L; step (3) forms copper arsenate, ferric arsenate, and zinc arsenate precipitate, the precipitate is removed by filtration, and the heavy metal ions in the absorption solution are removed by electrodeposition; After detection, the arsenic content in the tail gas after purification treatment is less than 0.8 mg / m³, and the removal rate of hydrogen chloride is more than 30%, effectively reducing the amount of arsenic and chlorine entering the subsequent flue gas desulfurization system.

[0021] Example 5 A coal chemical enterprise using high-sulfur and high-arsenic coal as raw material, the flue gas produced still contains pollutants such as sulfur dioxide, arsenic chloride, and hydrogen chloride after bag- electrostatic dust removal. According to the method of the present embodiment, the method for deep purification and impurity removal before flue gas desulfurization of industrial furnaces and kilns in the present embodiment is based on Example 1, and the difference from Example 1 is that: step (1) uses a packed tower; step (2) configures a soluble metal salt solution containing ferric sulfate, the solution mass concentration is 10-30%, and the pH is 3-5. Hydrogen peroxide and ozone are added to the solution, and the concentration is 250-500 mg / L; step (3) forms ferric arsenate precipitate, the precipitate is removed by filtration, and the heavy metal ions in the absorption solution are removed by electrodeposition; The arsenic content in the tail gas after the purification treatment is less than 0.4 mg / m³, and the hydrogen chloride removal rate is more than 30%, so that the amount of arsenic and chlorine entering the subsequent flue gas desulfurization system is effectively reduced.

Claims

1. A method for deep purification and impurity removal of industrial furnace flue gas before desulfurization, characterized in that The method comprises the following steps: (1) introducing the dust-removed sulfur-containing flue gas into a wet scrubbing tower; (2) washing the sulfur-containing flue gas with a soluble metal salt solution to form a dilute sulfuric acid solution containing metal salt as an absorbent; (3) contacting the absorbent obtained in step (2) with the flue gas treated in step (2) to cause hydrolysis, and converting arsenic chloride, hydrogen chloride and lead chloride in the flue gas into soluble salts of arsenate, lead ion and chloride ion, and precipitating insoluble arsenate salt by the reaction between the arsenate and metal cations in the absorbent, so that the treated flue gas is high-sulfur flue gas purified and impurity-removed.

2. The method of deep purification and impurity removal before FGD of industrial furnace flue gas according to claim 1, characterized in that The metal cations in the soluble metal salt solution in step (2) include one or more of iron, copper, lead and zinc ions, and the mass concentration of the solution is 0.1% to 50%.

3. The method of deep purification and impurity removal before FGD of industrial furnace flue gas according to claim 1, characterized in that The soluble metal salt solution in step (2) is supplemented with an oxidant during use, the oxidant is hydrogen peroxide and / or ozone, and the concentration of the oxidant is 1 mg / L to 500 mg / L.

4. The method of deep purification and impurity removal prior to FGD of industrial furnace flue gas as claimed in claim 1, wherein The pH of the soluble metal salt solution in step (2) is controlled to be 0 to 7.

5. The method of deep purification and impurity removal prior to FGD of industrial furnace flue gas as claimed in claim 1, wherein The wet scrubbing tower is a bubble tower, sieve plate tower, packed tower or spray tower.

6. The method of deep purification and impurity removal prior to FGD of industrial furnace flue gas as claimed in claim 1 wherein Step (3) removes the precipitate in the absorbent by solid-liquid separation, which is one or more of gravity sedimentation, centrifugation and filtration.

7. The method of deep purification and impurity removal prior to FGD of industrial furnace flue gas as claimed in claim 1 wherein Step (3) removes the heavy metal ions in the absorbent by chemical precipitation, metal displacement or electrodeposition.