A method for removing SO2 and CO2 from flue gas

Abstract

The present invention belongs to the technical field of flue gas purification, and particularly relates to a method for removing SO2 and CO2 from flue gas, comprising the following steps: S1: Using HA-Ca and NH4Cl as raw materials, fully stirring and mixing them with water 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 NH3 obtained in S2 into the CaCl2 solution, and passing flue gas containing CO2 to generate a mixture of NH4Cl and CaCO3; S5: Filtering the mixture of NH4Cl and CaCO3 to obtain CaCO3 precipitate and NH4Cl solution; S6: Adding the NH3 obtained in S2 into the absorption reaction device, passing flue gas containing SO2 and water, and reacting to generate (NH4)2SO3; S7: Oxidizing (NH4)2SO3 to obtain (NH4)2SO4; S8: Mixing (NH4)2SO4 with HA in S3 and using it as a humic acid organic compound fertilizer; it has high-efficiency 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 SO2 and CO2 from flue gas. Background Art

[0002] With the acceleration of the industrialization process, the extensive use of fossil fuels has led to a continuous increase in the emissions of SO2 and CO2 in flue gas. SO2 is one of the main pollutants causing acid rain, while CO2 is the main source of greenhouse gas emissions. Controlling the emissions of SO2 and CO2 is of great significance for protecting the global environment and the development of the national economy.

[0003] The current industrial methods for removing CO2 from flue gas mainly include amine method removal, wet scrubbing technology, etc. The methods for removing SO2 include sodium-based dry desulfurization (SDS) technology, ammonia-based desulfurization, etc. The amine method removal technology 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 simple operation, but the CO2 absorption efficiency is relatively low, usually less than 10%; it needs to treat a large amount of wastewater and there is a risk of secondary pollution. The SDS technology has a simple process, no wastewater generation, and low energy consumption, but low efficiency and has certain requirements for flue gas temperature and humidity. Ammonia-based desulfurization has secondary pollution (ammonia escape) and high costs. Therefore, high-efficiency treatment technologies are difficult to achieve due to high costs, and conventional methods have problems such as low efficiency and secondary pollution.

[0004] Therefore, researching and developing technologies for removing SO2 and CO2 from flue gas with low cost and high efficiency is of great significance for solving industrial flue gas pollution problems. Summary of the Invention

[0005] The present invention discloses a method for removing SO2 and CO2 from flue gas, mainly solving the problems of low efficiency and secondary pollution in current flue gas removal of SO2 and CO2.

[0006] To achieve the above object, the present invention provides a method for removing SO2 and CO2 from flue gas, including the following steps:

[0007] S1: Select HA-Ca and NH4Cl as raw materials, add water and stir well to obtain a mixture of CaCl2 and HA-NH4;

[0008] S2: Heat and decompose the mixture of CaCl2 and HA-NH4 to obtain a mixture of HA and CaCl2, and NH3;

[0009] S3: Filter the mixture of HA and CaCl2 to obtain HA precipitate and CaCl2 solution;

[0010] S4: Introduce the NH3 obtained in S2 into the CaCl2 solution, and introduce the flue gas containing CO2 to generate a mixture of NH4Cl and CaCO3;

[0011] S5: Filter the mixture of NH4Cl and CaCO3 to obtain CaCO3 precipitate and NH4Cl solution;

[0012] 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;

[0013] S7: Oxidize (NH4)2SO3 to obtain (NH4)2SO4;

[0014] S8: Use the mixture of (NH4)2SO4 and HA in S3 as humic acid organic compound fertilizer.

[0015] Preferably, the NH4Cl 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 ammonium chloride solution.

[0016] Preferably, the CaCO3 in S5 is used as a chemical raw material.

[0017] Preferably, the mass ratio of HA-Ca to NH4Cl in S1 is 1:1 to 1:3.

[0018] Preferably, the volume percentage content of CO2 in S4 is 5% - 20%, and the volume percentage content of SO2 in S6 is 0.01% - 0.5%.

[0019] The technical solution provided by the present invention has at least the following technical effects:

[0020] 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, generating humic acid, calcium chloride and ammonia, and the ammonia 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 to generate light calcium carbonate and ammonium chloride solution. At the same time, the collected ammonia is used to absorb sulfur dioxide in the flue gas to form ammonium sulfite. 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 ability, low raw material cost, simple process flow, and no secondary pollution.

[0021] 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. This not only improves production efficiency but also helps reduce the generation of industrial waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] 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-described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0023] Figure 1 It is a flowchart of the method for removing SO2 and CO2 from flue gas in the embodiments of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] 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 throughout. The embodiments described below with reference 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.

[0025] Example 1: As Figure 1 shown, this embodiment discloses a method for removing SO2 and CO2 from flue gas, including the following steps:

[0026] S1: Select HA-Ca (calcium humate) and NH4Cl (ammonium chloride) as raw materials. The mass ratio of HA-Ca (calcium humate) to NH4Cl (ammonium chloride) is 1:1. After adding water and fully stirring and mixing, the addition amount of water to the mass ratio of the solid mixture of HA-Ca (calcium humate) and NH4Cl (ammonium chloride) is 5:1 to obtain a mixture of calcium chloride CaCl2 and HA-NH4 (ammonium humate). The chemical reaction formula is:

[0027] ;

[0028] S2: Heat and decompose the mixture of CaCl2 and HA-NH4 to obtain a mixture of HA (humic acid) and CaCl2, and NH3

[0029] The chemical reaction formula is:

[0030] ;

[0031] S3: Filter the mixture of HA and CaCl₂ to obtain HA precipitate and CaCl₂ solution;

[0032] S4: Pass the NH₃ obtained in S2 into the CaCl₂ solution, and pass the flue gas containing CO₂. The concentration of the CaCl₂ solution is 1.1%, the molar ratio of NH₃, CO₂ to the CaCl₂ solution is 2:1:1, the concentration of CO₂ in the flue gas is 20%, and a mixture of NH₄Cl and CaCO₃ is formed;

[0033] The chemical reaction formula is:

[0034] ;

[0035] S5: Filter the mixture of NH₄Cl and CaCO₃ to obtain CaCO₃ precipitate and NH₄Cl solution; The NH₄Cl solution can be reintroduced into the HA-Ca reaction system and treated under the same reaction conditions as in S1 to achieve the recycling of the ammonium chloride solution. CaCO₃ can be used as a chemical raw material and applied to industries such as the paper industry, rubber industry, and plastic industry;

[0036] S6: Add the NH₃ obtained in S2 to the absorption reaction device, pass the flue gas containing SO₂ and water. The molar ratio of the introduced NH₃ to SO₂ in the flue gas is 2:1, and the concentration of SO₂ in the flue gas is 2000 ppm, and (NH₄)₂SO₃ is formed by reaction;

[0037] The chemical reaction formula is:

[0038] ;

[0039] S7: Add (NH₄)₂SO₃ to the jet oxidizer for oxidation to obtain (NH₄)₂SO₄;

[0040] The chemical reaction formula is:

[0041] ;

[0042] S8: Mix (NH₄)₂SO₄ with HA in S3 and use it as a humic acid organic compound fertilizer.

[0043] The flue gas reacts with the absorbent, and the reaction time is 15 minutes. After detection, the SO₂ removal efficiency is 94%, and the CO₂ removal efficiency is 87%.

[0044] Example 2: As Figure 1 shown, this example discloses a method for removing SO₂ and CO₂ from flue gas, including the following steps:

[0045] S1: Select HA-Ca (calcium humate) and NH4Cl (ammonium chloride) as raw materials. The mass ratio of HA-Ca (calcium humate) to NH4Cl (ammonium chloride) is 1:2. After adding water and fully stirring and mixing, the addition amount of water to the mass ratio of the solid mixture of HA-Ca (calcium humate) and NH4Cl (ammonium chloride) is 8:1 to obtain a mixture of calcium chloride CaCl2 and HA-NH4 (ammonium humate).

[0046] The chemical reaction formula is:

[0047] ;

[0048] S2: Heat and decompose the mixture of CaCl2 and HA-NH4 to obtain a mixture of HA (humic acid) and CaCl2, and NH3

[0049] The chemical reaction formula is:

[0050] ;

[0051] S3: Filter the mixture of HA and CaCl2 to obtain HA precipitate and CaCl2 solution;

[0052] S4: Pass the CaCl2 solution into the NH3 and flue gas containing CO2 obtained in S2. The concentration of the CaCl2 solution is 1.1%. The molar ratio of NH3, CO2 to the CaCl2 solution is 2:1:1. The concentration of CO2 in the flue gas is 15% to generate a mixture of NH4Cl and CaCO3;

[0053] The chemical reaction formula is:

[0054] ;

[0055] S5: Filter the mixture of NH4Cl and CaCO3 to obtain CaCO3 precipitate and NH4Cl solution; The NH4Cl 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. CaCO3 can be used as a chemical raw material and applied to industries such as the paper industry, rubber industry, and plastic industry;

[0056] S6: Add the NH3 obtained in S2 to the absorption reaction device, pass in the flue gas containing SO2 and water. The molar ratio of the passed-in NH3 to SO2 in the flue gas is 2:1. The concentration of SO2 in the flue gas is 1500 ppm, and the reaction generates (NH4)2SO3;

[0057] The chemical reaction formula is:

[0058] ;

[0059] S7: Add (NH4)2SO3 to the jet oxidizer for oxidation to obtain (NH4)2SO4;

[0060] The chemical reaction equation is:

[0061] ;

[0062] S8: Mix (NH4)2SO4 with HA in S3 for use as a humic acid organic compound fertilizer.

[0063] The flue gas temperature is 45 °C and the flow rate is 1.5 m / s. The adsorbent is loaded into the adsorption tower, the flue gas passes through the adsorbent layer, and the reaction time is 12 minutes. The SO2 removal efficiency is 96%, and the CO2 removal efficiency is 89%.

[0064] Example 3: As Figure 1 shown, this example discloses a method for removing SO2 and CO2 from flue gas, including the following steps:

[0065] S1: Select HA-Ca (calcium humate) and NH4Cl (ammonium chloride) as raw materials. The mass ratio of HA-Ca (calcium humate) to NH4Cl (ammonium chloride) is 1:3. After adding water and fully stirring and mixing, the water addition amount is 10:1 with the mass of the solid mixture of HA-Ca (calcium humate) and NH4Cl (ammonium chloride) to obtain a mixture of calcium chloride CaCl2 and HA-NH4 (ammonium humate).

[0066] The chemical reaction equation is:

[0067] ;

[0068] S2: Heat and decompose the mixture of CaCl2 and HA-NH4 to obtain a mixture of HA (humic acid) and CaCl2, and NH3

[0069] The chemical reaction equation is:

[0070] ;

[0071] S3: Filter the mixture of HA and CaCl2 to obtain HA precipitate and CaCl2 solution;

[0072] S4: Pass the CaCl2 solution into the NH3 and CO2-containing flue gas obtained in S2. The concentration of the CaCl2 solution is 1.1%, and the molar ratio of NH3, CO2 to the CaCl2 solution is 2:1:1. The concentration of CO2 in the flue gas is 10% to generate a mixture of NH4Cl and CaCO3;

[0073] The chemical reaction equation is:

[0074] ;

[0075] S5: Filter the mixture of NH₄Cl and CaCO₃ to obtain CaCO₃ precipitate and NH₄Cl solution; the NH₄Cl 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 ammonium chloride solution, and CaCO₃ can be used as a chemical raw material; it is applied to industries such as the paper industry, rubber industry, and plastic industry;

[0076] S6: Add the NH₃ obtained in S2 into the absorption reaction device, introduce flue gas containing SO₂ and water, the molar ratio of the introduced NH₃ to SO₂ in the flue gas is 2:1, the concentration of SO₂ in the flue gas is 1000 ppm, and react to generate (NH₄)₂SO₃;

[0077] The chemical reaction formula is: ;

[0078] S7: Add (NH₄)₂SO₃ into the jet oxidizer for oxidation to obtain (NH₄)₂SO₄;

[0079] The chemical reaction formula is: ;

[0080] S8: Mix (NH₄)₂SO₄ with HA in S3 and use it as a humic acid organic compound fertilizer.

[0081] The flue gas temperature is 40°C and the flow rate is 1.2 m / s. Load the adsorbent into the adsorption tower, the flue gas passes through the adsorbent layer, and the reaction time is 10 minutes. The SO₂ removal efficiency is 95%, and the CO₂ removal efficiency is 92%.

[0082] 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, and the ammonia 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 to generate light calcium carbonate and ammonium chloride solution. At the same time, the collected ammonia is used to absorb sulfur dioxide in the flue gas to form ammonium sulfite. 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 capacity, low raw material cost, simple process flow, and no secondary pollution.

[0083] The generated ammonium chloride solution can be effectively recovered and reused in the reaction system of calcium humate, and the produced light calcium carbonate can be used as an important chemical raw material in the paper industry, rubber industry, and plastic industry, thereby realizing the recycling and conservation of resources. It not only improves production efficiency but also helps to reduce the generation of industrial waste.

[0084] The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. 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, It includes the following steps: S1: Select HA-Ca and NH4Cl as raw materials. After adding water and fully stirring and mixing them, a mixture of CaCl2 and HA-NH4 is obtained; S2: Heat and decompose the mixture of CaCl2 and HA-NH4 to obtain a mixture of HA and CaCl2, and NH3; S3: Filter the mixture of HA and CaCl2 to obtain a HA precipitate and a CaCl2 solution; S4: Pass the NH3 obtained in S2 into the CaCl2 solution, and pass the flue gas containing CO2 to generate a mixture of NH4Cl and CaCO3; S5: Filter the mixture of NH4Cl and CaCO3 to obtain a CaCO3 precipitate and an NH4Cl solution; S6: Add the NH3 obtained in S2 into the absorption reaction device, pass the flue gas containing SO2 and water, and react to generate (NH4)2SO3; S7: Oxidize (NH4)2SO3 to obtain (NH4)2SO4; S8: Mix (NH4)2SO4 with HA in S3 and use it as a humic acid organic compound fertilizer.

2. The method for removing SO2 and CO2 from flue gas according to claim 1, characterized in that, Reintroduce the NH4Cl solution in S5 into the reaction system of HA-Ca, and process it according to the same reaction conditions as in S1 to realize 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, Use the CaCO3 in S5 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 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 content of CO2 in S4 is 5% to 20%, and the volume percentage content of SO2 in S6 is 0.01% to 0.5%.

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