Method for removing SO2 and CO2 in flue gas

Abstract

The invention belongs to the technical field of flue gas purification, and particularly relates to a method for removing SO2 and CO2 in flue gas, which comprises the following steps: S1, selecting HA-Ca and NH4Cl as raw materials, adding water, and fully stirring and fusing to obtain a mixture of CaCl2 and HA-NH4; s2, a mixture of CaCl2 and HA-NH4 is heated and decomposed, and a mixture of HA and CaCl2 and NH3 are obtained; s3, filtering the mixture of the HA and the CaCl2 to obtain an HA precipitate and a CaCl2 solution; s4, a CaCl2 solution is introduced into the NH3 obtained in the step S2 and the flue gas containing CO2, and a mixture of NH4Cl and CaCO3 is generated; s5, filtering the mixture of the NH4Cl and the CaCO3 to obtain a CaCO3 precipitate and a NH4Cl solution; s6, NH3 obtained in S2 is added into an absorption reaction device, SO2-containing flue gas and water are introduced, and (NH4) 2SO3 is generated through a reaction; s7, (NH4) 2SO3 is subjected to oxidation, and (NH4) 2SO4 is obtained; s8, (NH4) 2SO4 and HA in the S3 are mixed to be used as the humic acid organic compound fertilizer; the method has the advantages of efficient waste gas treatment capacity, low raw material cost, simple process flow and no secondary pollution.

Description

Technical Field

[0001] The present invention belongs to the technical field of flue gas purification, and particularly relates to a method for removing SO 2 and CO 2 from flue gas. Background Art

[0002] With the acceleration of the industrialization process, the extensive use of fossil fuels has led to an increasing emission of SO 2 and CO 2 in flue gas. SO 2 is one of the main pollutants causing acid rain, while CO 2 is the main source of greenhouse gas emissions. Controlling the emissions of SO 2 and CO 2 is of great significance for protecting the global environment and the development of the national economy.

[0003] The current industrial methods for removing CO 2 from flue gas mainly include amine method and wet scrubbing technology. The methods for removing SO 2 include sodium-based dry desulfurization (SDS) technology, ammonia-based desulfurization, etc. The amine method has high removal efficiency, but high energy consumption, requires a large amount of amine absorbents, has a high operating cost, and there are problems with the recovery and regeneration of amine absorbents. The wet scrubbing technology has a mature process and is easy to operate, but the CO 2 absorption efficiency is relatively low, usually less than 10%; it requires a large amount of wastewater treatment and there is a risk of secondary pollution. The SDS technology has a simple process, no wastewater generation, and low energy consumption, but the efficiency is low and there are certain requirements for flue gas temperature and humidity. Ammonia-based desulfurization has secondary pollution (ammonia escape) and high costs. Therefore, it is difficult to achieve high-efficiency treatment technology due to high costs, and conventional methods have problems such as low efficiency and secondary pollution.

[0004] Therefore, researching and developing technologies for low-cost and high-efficiency removal of SO 2 and CO 2 from flue gas is of great significance for solving industrial flue gas pollution problems. Summary of the Invention

[0005] The present invention discloses a method for removing SO 2 and CO 2 from flue gas, mainly solving the problems of low efficiency and secondary pollution in current flue gas removal of SO 2 and CO 2 from flue gas.

[0006] To achieve the above object, the present invention provides a method for removing SO 2 and CO 2 from flue gas, comprising the following steps: S1: Select HA-Ca and NH 4 Cl as raw materials. After adding water and fully stirring and mixing, a mixture of CaCl 2 and HA-NH 4 is obtained; S2: Heat and decompose the mixture of CaCl 2 and HA-NH 4 to obtain a mixture of HA and CaCl 2 , NH 3 ; S3: Filter the mixture of HA and CaCl 2 to obtain a HA precipitate and a CaCl 2 solution; S4: Pass the CaCl 2 solution into the NH 3 obtained in S2 and the flue gas containing CO 2 to generate a mixture of NH 4 Cl and CaCO 3 ; S5: Filter the mixture of NH 4 Cl and CaCO 3 to obtain a CaCO 3 precipitate and an NH 4 Cl solution; S6: Add the NH 3 obtained in S2 into the absorption reaction device, pass in the flue gas containing SO 2 and water, and react to generate (NH 4 ) 2 SO 3 ; S7: Oxidize (NH 4 ) 2 SO 3 to obtain (NH 4 ) 2 SO 4 ; S8: Mix (NH 4 ) 2 SO 4 with the HA in S3 and use it as a humic acid organic compound fertilizer.

[0007] Preferably, the NH 4 Cl solution in S5 is reintroduced into the reaction system of HA-Ca and treated under the same reaction conditions as in S1 to achieve the recycling of the ammonium chloride solution.

[0008] Preferably, the CaCO 3 in S5 is used as a chemical raw material.

[0009] Preferably, in S1, HA-Ca and NH4 The mass ratio of Cl is 1:1 to 1:3.

[0010] Preferably, the volume percentage content of CO in the S6 and S8 2 is 5% to 20%, and the volume percentage content of SO 2 is 0.01% to 0.5%.

[0011] The technical solution provided by the present invention has at least the following technical effects: Calcium humate and ammonium chloride are converted into ammonium humate and calcium chloride under the action of water. The mixture of ammonium humate and calcium chloride decomposes after heating to produce humic acid, calcium chloride and ammonia gas, and the ammonia gas is subsequently collected. Through the filtration operation, humic acid and calcium chloride solution are separated. After the calcium chloride solution absorbs carbon dioxide in the flue gas, it reacts with ammonia gas to form light calcium carbonate and ammonium chloride solution. At the same time, the collected ammonia gas is used to absorb sulfur dioxide in the flue gas, and then ammonium sulfite is formed. Ammonium sulfite is converted into ammonium sulfate and humic acid through an oxidation reaction, and these substances can be used as fertilizers. This process has high-efficiency waste gas treatment ability, low raw material cost, simple process flow, and no secondary pollution.

[0012] The generated ammonium chloride solution can be effectively recovered and reused in the reaction system of calcium humate. The generated light calcium carbonate can be used as an important chemical raw material in the paper industry, rubber industry and plastic industry, so as to realize the recycling and conservation of resources. It not only improves production efficiency, but also helps to reduce the generation of industrial waste. Brief Description of the Drawings

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0014] Figure 1 It is a process flow diagram for removing SO 2 and CO 2 from the flue gas in the embodiment of the present invention. Detailed Embodiments

[0015] The following will describe in detail the embodiments of the present invention. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below by referring to the drawings are exemplary and are intended to explain the embodiments of the present invention, and should not be construed as a limitation of the present invention.

[0016] Example 1: As shown in Figure 1 the following, this example discloses a method for removing SO 2 and CO 2 from flue gas, which includes the following steps: S1: Select HA-Ca (calcium humate) and NH 4 Cl (ammonium chloride) as raw materials. The mass ratio of HA-Ca (calcium humate) to NH 4 Cl (ammonium chloride) is 1:1. After adding water and fully stirring and mixing, the addition amount of water is in a mass ratio of 5:1 to the solid mixture of HA-Ca (calcium humate) and NH 4 Cl (ammonium chloride), obtaining a mixture of calcium chloride CaCl 2 and HA-NH 4 (ammonium humate).

[0017] The chemical reaction formula is: HA-Ca + NH 4 Cl + H 2 O → HA-NH 4 + CaCl 2 ; S2: Heat and decompose the mixture of CaCl 2 and HA-NH 4 to obtain a mixture of HA (humic acid) and CaCl 2 , and NH 3 The chemical reaction formula is: ; S3: Filter the mixture of HA and CaCl 2 to obtain HA precipitate and CaCl 2 solution; S4: Pass the CaCl 2 solution into the NH 3 obtained in S2 and the flue gas containing CO 2 . The concentration of the CaCl 2 solution is 1.1%. The molar ratio of NH 3 , CO 2 to the CaCl 2 solution is 2:1:1. The concentration of CO 2 in the flue gas is 20%, generating a mixture of NH 4 Cl and CaCO 3 ; The chemical reaction formula is: NH 3 + H 2 O + CaCl 2 + CO 2 →CaCO 3 ↓ + NH 4 Cl; S5: Filter the mixture of NH 4 Cl and CaCO 3 to obtain CaCO 3 precipitate and NH 4 Cl solution; the NH 4 Cl solution can be re-introduced into the reaction system of HA-Ca and treated under the same reaction conditions as in S1 to achieve the recycling of ammonium chloride solution. CaCO 3 can be used as a chemical raw material and applied to industries such as the paper industry, rubber industry, and plastic industry; S6: Add the NH 3 obtained in S2 into the absorption reaction device, and introduce flue gas containing SO 2 and water. The molar ratio of the introduced NH 3 to SO 2 in the flue gas is 2:1, and the concentration of SO 2 in the flue gas is 2000 ppm. React to generate (NH 4 ) 2 SO 3 ; The chemical reaction equation is: NH 3 + SO 2 + H 2 O →(NH 4 ) 2 SO 3 ; S7: Add (NH 4 ) 2 SO 3 to the jet oxidizer for oxidation to obtain (NH 4 ) 2 SO 4 ; The chemical reaction equation is: (NH 4 ) 2 SO 3 + O 2 →(NH 4 ) 2 SO 4 ; S8: Mix (NH 4 ) 2 SO 4 with HA in S3 and use it as a humic acid organic compound fertilizer.

[0018] The flue gas reacts with the absorbent, and the reaction time is 15 minutes. After detection, the SO 2 removal efficiency is 94%, and the CO 2 removal efficiency is 87%.

[0019] Example 2: AsFigure 1 As shown in the figure, this embodiment discloses a method for removing SO2 and CO2 from flue gas, which includes the following steps: S1: Select HA-Ca (calcium humate) and NH 4 Cl (ammonium chloride) as raw materials. The mass ratio of HA-Ca (calcium humate) to NH 4 Cl (ammonium chloride) is 1:2. After adding water and fully stirring and mixing, the addition amount of water is 8:1 with the mass of the solid mixture of HA-Ca (calcium humate) and NH 4 Cl (ammonium chloride) to obtain a mixture of calcium chloride CaCl 2 and HA-NH 4 (ammonium humate).

[0020] The chemical reaction formula is: HA-Ca + NH 4 Cl + H 2 O → HA-NH 4 + CaCl 2 ; S2: Heat and decompose the mixture of CaCl 2 and HA-NH 4 to obtain a mixture of HA (humic acid) and CaCl 2 and NH 3 The chemical reaction formula is: ; S3: Filter the mixture of HA and CaCl 2 to obtain a HA precipitate and a CaCl 2 solution; S4: Pass the CaCl 2 solution into the NH 3 obtained in S2 and the flue gas containing CO 2 . The concentration of the CaCl 2 solution is 1.1%. The molar ratio of NH 3 , CO 2 to the CaCl 2 solution is 2:1:1. The concentration of CO 2 in the flue gas is 15% to generate a mixture of NH 4 Cl and CaCO 3 ; The chemical reaction formula is: NH 3 + H 2 O + CaCl 2 + CO 2 →CaCO 3 ↓ + NH 4 Cl; S5: Mix NH 4 Cl and CaCO 3The mixture is filtered to obtain CaCO 3 The precipitate and NH 4 Cl solution; the NH 4 Cl solution can be re-introduced into the reaction system of HA-Ca and treated under the same reaction conditions as S1 to realize the recycling of the ammonium chloride solution. CaCO 3 can be used as a chemical raw material and applied to industries such as the paper industry, rubber industry, and plastic industry; S6: Add the NH 3 obtained in S2 into the absorption reaction device, introduce flue gas containing SO 2 and water. The molar ratio of the introduced NH 3 to SO 2 in the flue gas is 2:1, and the concentration of SO 2 in the flue gas is 1500 ppm. React to generate (NH 4 ) 2 SO 3 ; The chemical reaction formula is: NH 3 + SO 2 + H 2 O →(NH 4 ) 2 SO 3 ; S7: Add (NH 4 ) 2 SO 3 to the jet oxidizer for oxidation to obtain (NH 4 ) 2 SO 4 ; The chemical reaction formula is: (NH 4 ) 2 SO 3 + O 2 →(NH 4 ) 2 SO 4 ; S8: Mix (NH 4 ) 2 SO 4 with HA in S3 and use it as a humic acid organic compound fertilizer.

[0021] The flue gas temperature is 45°C and the flow rate is 1.5 m / s. The adsorbent is loaded into the adsorption tower, and the flue gas passes through the adsorbent layer with a reaction time of 12 minutes. The SO 2 removal efficiency is 96%, and the CO 2 removal efficiency is 89%.

[0022] Example 3: As Figure 1 shown, this example discloses a method for removing SO in flue gas2 and CO 2 The method includes the following steps: S1: Select HA-Ca (calcium humate) and NH 4 Cl (ammonium chloride) as raw materials. The mass ratio of HA-Ca (calcium humate) to NH 4 Cl (ammonium chloride) is 1:3. After adding water and fully stirring and mixing, the addition amount of water and the mass ratio of the solid mixture of HA-Ca (calcium humate) and NH 4 Cl (ammonium chloride) is 10:1, obtaining a mixture of calcium chloride CaCl 2 and HA-NH 4 (ammonium humate).

[0023] The chemical reaction formula is: HA-Ca + NH 4 Cl + H 2 O → HA-NH 4 + CaCl 2 ; S2: Heat and decompose the mixture of CaCl 2 and HA-NH 4 to obtain a mixture of HA (humic acid) and CaCl 2 and NH 3 The chemical reaction formula is: ; S3: Filter the mixture of HA and CaCl 2 to obtain a HA precipitate and a CaCl 2 solution; S4: Pass the CaCl 2 solution into the NH 3 obtained in S2 and the flue gas containing CO 2 . The concentration of the CaCl 2 solution is 1.1%. The molar ratio of NH 3 , CO 2 to the CaCl 2 solution is 2:1:1. The concentration of CO 2 in the flue gas is 10%, generating a mixture of NH 4 Cl and CaCO 3 ; The chemical reaction formula is: NH 3 + H 2 O + CaCl 2 + CO 2 → CaCO 3 ↓ + NH 4 Cl; S5: The NH 4 Cl and CaCO 3The mixture is filtered to obtain CaCO 3 precipitate and NH 4 Cl solution; the NH 4 Cl solution can be reintroduced into the reaction system of HA-Ca and treated under the same reaction conditions as in S1 to achieve the recycling of the ammonium chloride solution. CaCO 3 can be used as a chemical raw material and applied to industries such as the paper industry, rubber industry, and plastic industry; S6: Add the NH 3 obtained in S2 into the absorption reaction device, introduce flue gas containing SO 2 and water. The molar ratio of the introduced NH 3 to SO 2 in the flue gas is 2:1, and the concentration of SO 2 in the flue gas is 1000 ppm. React to generate (NH 4 ) 2 SO 3 ; The chemical reaction formula is: NH 3 + SO 2 + H 2 O →(NH 4 ) 2 SO 3 ; S7: Add (NH 4 ) 2 SO 3 to the jet oxidizer for oxidation to obtain (NH 4 ) 2 SO 4 ; The chemical reaction formula is: (NH 4 ) 2 SO 3 + O 2 →(NH 4 ) 2 SO 4 ; S8: Mix (NH 4 ) 2 SO 4 with HA in S3 and use it as a humic acid organic compound fertilizer.

[0024] The flue gas temperature is 40°C and the flow rate is 1.2 m / s. The adsorbent is loaded into the adsorption tower, and the flue gas passes through the adsorbent layer with a reaction time of 10 minutes. The SO 2 removal efficiency is 95%, and the CO 2 removal efficiency is 92%.

[0025] In summary, in the present invention, calcium humate and ammonium chloride are converted into ammonium humate and calcium chloride under the action of water. The mixture of ammonium humate and calcium chloride decomposes after heating to produce humic acid, calcium chloride and ammonia gas, and the ammonia gas is subsequently collected. Through filtration operation, humic acid and calcium chloride solution are separated. After the calcium chloride solution absorbs carbon dioxide in the flue gas, it reacts with ammonia gas to form light calcium carbonate and ammonium chloride solution. At the same time, the collected ammonia gas is used to absorb sulfur dioxide in the flue gas, and then ammonium sulfite is formed. Ammonium sulfite is converted into ammonium sulfate and humic acid through oxidation reaction, and these substances can be used as fertilizers. This process has high-efficiency waste gas treatment capacity, low raw material cost, simple process flow, and no secondary pollution.

[0026] The generated ammonium chloride solution can be effectively recovered and reused in the reaction system of calcium humate. The produced light calcium carbonate can be used as an important chemical raw material in the paper industry, rubber industry and plastic industry, thus realizing the recycling and conservation of resources. It not only improves production efficiency, but also helps to reduce the generation of industrial waste.

[0027] The above disclosure of the embodiments is only for the purpose of better implementing the present invention, and is not used to limit the present invention. Any modifications, equivalent replacements and improvements made on the basis and within the scope of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for removing SO2 and CO2 from flue gas, characterized in that: The steps include: S1: HA-Ca and NH4Cl are selected as raw materials, water is added and stirred thoroughly to obtain a mixture of CaCl2 and HA-NH4; S2: heating and decomposing the mixture of CaCl2 and HA-NH4 to obtain a mixture of HA and CaCl2 and NH3; S3: filtering the mixture of HA and CaCl2 to obtain HA precipitate and CaCl2 solution; S4: passing the CaCl2 solution into the NH3 and CO2-containing flue gas obtained in S2 to generate a mixture of NH4Cl and CaCO3; S5: filtering the mixture of NH4Cl and CaCO3 to obtain CaCO3 precipitate and NH4Cl solution; S6: Add the NH3 obtained in S2 to the absorption reaction device, introduce the flue gas containing SO2 and water, and react to generate (NH4)2SO3; S7: oxidizing (NH4)2SO3 to obtain (NH4)2SO4; S8: Mix (NH4)2SO4 with HA in S3 and use it as humic acid organic compound fertilizer.

2. The method for removing SO2 and CO2 from flue gas according to claim 1, characterized in that: The NH4Cl solution in S5 is reintroduced into the reaction system of HA-Ca and treated under the same reaction conditions as S1 to achieve the recycling of the ammonium chloride solution.

3. The method for removing SO2 and CO2 from flue gas according to claim 1, characterized in that: The CaCO3 in S5 is used as a chemical raw material.

4. The method for removing SO2 and CO2 from flue gas according to claim 1, characterized in that: The mass ratio of HA-Ca to NH4Cl in the S1 is 1:1 to 1:

3.

5. The method for removing SO2 and CO2 from flue gas according to claim 1, characterized in that: The volume percentage of CO2 in S6 and S8 is 5% to 20%, and the volume percentage of SO2 is 0.01% to 0.5%.

Images