Method for synergetic resource utilization of carbon dioxide and sulfur dioxide in flue gas

Abstract

The invention relates to a method for synergetic resource utilization of carbon dioxide and sulfur dioxide in flue gas. The method comprises the following steps: (1) absorbing carbon dioxide and sulfur dioxide in flue gas by using absorption liquid containing potassium iodide, and controlling the pH value of the solution to be 5.0-9.0 to obtain a mixed solution; (2) the mixed solution obtained in the step (1) is subjected to ultraviolet irradiation, collaborative resource utilization of carbon dioxide and sulfur dioxide is achieved, carbon dioxide is reduced into formic acid, and sulfur dioxide is converted into sulfuric acid. The invention provides a method for synergetic resource utilization of CO2 and SO2 in flue gas. The method has the advantages of high efficiency of formic acid production through CO2 reduction and H2SO4 production through SO2 conversion, mild reaction conditions, no need of high temperature and high pressure, and no need of additional electron / proton sacrificial agent, and is a recycling technology with practical application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of resource utilization of carbon dioxide and sulfur dioxide, and in particular to a method for coordinated resource utilization of carbon dioxide and sulfur dioxide in flue gas. Background Art

[0002] Carbon dioxide and sulfur dioxide are important components of flue gas from thermal power plants, metal smelters and cement plants. Their large-scale emissions can lead to serious environmental pollution problems such as greenhouse effect, frequent extreme weather and acid rain. With global warming and the development of the "low-carbon economy", such problems have attracted widespread attention from scientific researchers.

[0003] Resource utilization is the best way to solve such problems. CO2 reduction is the main way to CO2 resource utilization. Among the reduction products of CO2, the least protons and electrons need to be transferred to generate formic acid. And formic acid is an excellent liquid hydrogen storage fuel and biochemical raw material, and is widely used in many fields. Traditional CO2 reduction methods mainly include electrochemical method, photocatalytic method and thermochemical method. CO2 reduction must go through two steps: single electron activation and protonation. However, CO2 has extremely strong stability, and its activation process has an extremely high energy barrier (750 kJ / mol), which leads to the traditional method of reducing CO2 to produce HCOOH. There are problems such as harsh reaction conditions, low efficiency and poor selectivity. SO2 resource utilization pathways mainly include: oxidation acid production, reduction to elemental sulfur and synthesis of organic molecules through organic reactions. However, these processes usually require the addition of catalysts, sacrificial agents, oxidants and reductants. Therefore, CO2 and SO2 resource systems usually have problems such as high cost, low efficiency due to competitive side reactions and harsh reaction conditions due to high reaction energy barriers. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for the coordinated resource utilization of carbon dioxide and sulfur dioxide in flue gas. The present invention uses SO2 and / or its derivatives, which are common components in flue gas, as electron donors to reduce CO2 to produce HCOOH, and SO2 is converted into H2SO4, thereby realizing the resource utilization of CO2 and SO2 in flue gas simultaneously. The method can achieve efficient reduction of carbon dioxide and generate formic acid with high selectivity; sulfur dioxide is converted into sulfuric acid, the only product.

[0005] The present invention provides a method for synergistic resource utilization of carbon dioxide and sulfur dioxide in flue gas, comprising the following steps: (1) Using an absorption liquid containing potassium iodide to absorb carbon dioxide and sulfur dioxide in the flue gas, controlling the pH of the solution to 5.0 to 9.0, and obtaining a mixed solution; (2) The mixed solution obtained in step (1) is irradiated with ultraviolet light to achieve the coordinated resource utilization of carbon dioxide and sulfur dioxide, wherein the carbon dioxide is reduced to formic acid and the sulfur dioxide is converted into H2SO4.

[0006] In some embodiments of the present invention, in step (1), CO2 and SO2 in the flue gas are important components of flue gas from coal-fired power plants, metal smelters, cement plants, etc.

[0007] In some embodiments of the present invention, in step (1), the absorption liquid further includes a strong alkali solution, and the strong alkali solution includes a sodium hydroxide solution and / or a potassium hydroxide solution.

[0008] In some embodiments of the present invention, the molar ratio of potassium iodide to strong base in the absorption liquid is (1:20) to (1:100). For example, it can be 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, etc.

[0009] In some embodiments of the present invention, in step (1), the concentration of potassium iodide in the absorption liquid is greater than 0 and less than or equal to 5 mM. For example, it can be 1 mM, 1.5 mM, 2 mM, 2.5 mM, 3 mM, 3.5 mM, 4 mM, 4.5 mM, 5 mM, etc.

[0010] In some embodiments of the present invention, in step (1), the concentration of potassium iodide in the absorption liquid is 1-3 mM.

[0011] In some embodiments of the present invention, in step (1), the concentration of [SO2] in the mixed solution is 10-50 mM, illustratively, it can be 10 mM, 20 mM, 30 mM, 40 mM, 50 mM, etc. The [SO2] includes SO2 and its derivative HSO3 - 、SO3 2- .

[0012] In some embodiments of the present invention, in step (1), the concentration of [SO2] in the mixed solution is 40-50 mM.

[0013] In some embodiments of the present invention, in step (1), the pH value is 5.5 to 7.5. For example, it can be 5.5, 6.0, 7.0, 7.5, etc.

[0014] In some embodiments of the present invention, in step (2), the ultraviolet light irradiation time is 2h~10h.

[0015] In some embodiments of the present invention, in step (2), the wavelength of the ultraviolet light in the ultraviolet light irradiation is 254 nm.

[0016] In the present invention, the method uses an absorption liquid to simultaneously absorb CO2 and SO2 in the flue gas. SO2 can be converted into its derivative Na2SO3 after being absorbed. Na2SO3 and KI can generate hydrated electrons that can activate CO2 under ultraviolet light. + / H2O and / or HSO3 - It can provide protons for the carbon dioxide reduction process. During the reaction, CO2 is activated to CO2 ·- , then sufficient proton sources protonate it, and HCOOH is generated with high selectivity. SO2 is converted into H2SO4, and KI can be recycled with the participation of SO2. In the experiment, after 4 hours of reaction, the CO2 conversion rate was 99.88%, and the HCOOH selectivity was 96.58%; SO2 and its derivatives were converted into H2SO4, and the conversion rate was 87.26% in 4 hours. The KI concentration in the system remained almost unchanged. In the simulated flue gas experiment, the system was able to continuously produce formic acid.

[0017] The above technical solution of the present invention has the following advantages compared with the prior art: 1. This method can simultaneously realize the resource utilization of carbon dioxide and sulfur dioxide in the flue gas of thermal power plants, metal smelters, and cement plants. Carbon dioxide is reduced to formic acid and sulfur dioxide is converted into sulfuric acid.

[0018] 2. The reaction conditions of this method are mild, and no high temperature or high pressure is required, and no external electron / proton sacrificial agent is required.

[0019] 3. The CO2 conversion rate of this method is as high as 99.88%, and the selectivity of formic acid in the product is as high as 96.58%.

[0020] 4. The only product of SO2 conversion in this method is H2SO4. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein: Figure 1 The test results of the reaction solution in Example 1 of the present invention; wherein (a) is a performance comparison diagram of the SO2+KI system reducing CO2 to produce formic acid, and (b) is a comparison diagram of the SO3 in the system during the reaction. 2- / SO4 2- and I - Concentration variation graph; Figure 2 The test results of the reaction solution in Example 2 of the present invention are shown in FIG. 1 , wherein (a) is a graph showing the effect of different concentrations of KI and (b) is a graph showing the effect of different concentrations of [SO2] on the reduction of CO2 to produce formic acid in the system; Figure 3This is a graph showing the detection results of the reaction solution in Example 3 of the present invention; Figure 4 This is a graph showing the results of detecting the concentration of carbon dioxide reduction products in the reaction solution in Example 4 of the present invention; Figure 5 The diagram of the simulated flue gas absorption and conversion device of the present invention; wherein, 1. N2, 2. SO2, 3. CO2, 4. O2, 5. NO, 6. gas cylinder pressure dividing valve, 7. flow meter, 8. gas mixing device, 9. mixed gas main valve, 10. gas heater, 11. photoreactor, 12. bubble distribution plate, 13. magnetic stirrer, 14. ultraviolet lamp, 15. tail gas absorption device; Figure 6 This is a diagram of the formic acid and sulfuric acid production of the simulated flue gas absorption conversion system in Example 5 of the present invention. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0023] Example 1: SO2+KI system reduces CO2 to produce HCOOH Verify the feasibility and performance of the synergistic resource utilization of CO2 reduction to HCOOH and SO2 to H2SO4 by SO2 and KI system. High-purity SO2 and CO2 were used as reaction gases, and the HCOOH and SO4 were measured under 254 nm ultraviolet light. 2- The steps are as follows: (1) CO2 was passed through 400 mL of deionized water at 25 °C for 30 minutes (the saturated concentration of CO2 under this condition was 33 mM). Appropriate amounts of NaOH and KI were added, with the concentrations of 100 mM and 2.5 mM, respectively. High-purity SO2 was passed through at a controlled gas flow rate of 100 mL / min, and [SO2] (including SO2 and its derivative HSO3 - 、SO3 2- ) concentration, and stop aeration when the [SO2] concentration reaches 50 mM. Use NaOH / H2SO4 solution to adjust the pH to 6.5.

[0024] (2) Irradiate the solution obtained in step (1) with a 254 nm ultraviolet light source for 10 h. Use circulating cooling water at 25°C to maintain the temperature of the reaction solution. Use a magnetic stirrer to stir the reaction solution to mix it evenly at a speed of 500 rpm. At the same time, use SO2 and KI single systems as control experiments.

[0025] (3) The carbon dioxide conversion rate, formic acid selectivity and SO2 conversion rate of the detection system are as follows: Figure 1As shown in the figure, the carbon dioxide conversion rate of the system is 99.88% after 4 hours of reaction, and the formic acid selectivity is 96.58%, which is significantly better than the single SO2 or KI system; SO2 is converted to H2SO4 with a conversion rate of 87.26% after 4 hours. The KI concentration in the system remains almost unchanged and no repeated addition is required.

[0026] Example 2: SO2+KI system reduces CO2 to produce HCOOH at different [SO2] and KI concentrations (1) CO2 was passed through 400 mL of deionized water at 25 °C for 30 minutes (the saturated concentration of CO2 under this condition is 33 mM). NaOH and KI were added to keep their concentrations in the range of 0-100 mM and 0-5 mM, respectively. High-purity SO2 was passed through at a controlled gas flow rate of 100 mL / min, and [SO2] (including SO2 and its derivative HSO3 - 、SO3 2- ) concentration, and stop aeration when the [SO2] concentration reaches the required concentration for the experiment. Use NaOH / H2SO4 solution to adjust the pH to 6.5.

[0027] (2) Irradiate the solution obtained in step (1) with a 254 nm ultraviolet light source for 10 h. Use 25°C circulating cooling water to maintain the temperature of the reaction solution, and use a magnetic stirrer to stir the reaction solution to mix it evenly at a speed of 500 rpm. The formic acid production and CO2 conversion rate of the system were tested. The experimental results are as follows: Figure 2 As shown, when the [SO2] concentration is fixed at 50 mM, when the KI concentration is 2.0 mM, 2.5 mM and 3.0 mM, the system has a better formic acid production effect, and the formic acid production in 4 hours is 31.09 mM, 32.56 mM and 32.67 mM, respectively, and the CO2 conversion rate is 94.21%, 98.67% and 99.00%, respectively; when the KI concentration is fixed at 2.5 mM, when the [SO2] concentration is 50 mM, the system has a better formic acid production effect, and the formic acid production in 4 hours is 32.56 mM, and the CO2 conversion rate is 98.67%.

[0028] Example 3: SO2+KI system reduces CO2 to produce HCOOH under different pH conditions.

[0029] (1) CO2 was passed through 400 mL of deionized water at 25 °C for 30 minutes (the saturated concentration of CO2 under this condition was 33 mM). Appropriate amounts of NaOH and KI were added, with the concentrations of 100 mM and 2.5 mM, respectively. High-purity SO2 was passed through at a controlled gas flow rate of 100 mL / min, and [SO2] (including SO2 and its derivative HSO3 - 、SO3 2-) concentration, and aeration was stopped when the [SO2] concentration reached 50 mM. The pH was adjusted to 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, and 9.0 using NaOH / H2SO4 solution.

[0030] (2) Irradiate the solution obtained in step (1) with a 254 nm ultraviolet light source for 10 h. Use 25°C circulating cooling water to maintain the temperature of the reaction solution, and use a magnetic stirrer to stir the reaction solution to mix it evenly at a speed of 500 rpm. The formic acid production and CO2 conversion rate of the system were tested. The experimental results are as follows: Figure 3 As shown, the system has a better effect of producing formic acid when the pH is 5.5-7.5.

[0031] Example 4 The other products in the reaction solution after 4 hours of reaction in step (2) of Example 1 were detected and analyzed. The detection results are as follows: Figure 4 As shown in the figure, the selectivity of formic acid in the product is as high as 96.39%, and the selectivity of by-products such as methanol, oxalic acid, acetic acid, and ethanol are 1.98%, 1.48%, 0.11%, and 0.04%, respectively. In addition, only trace amounts of gaseous products such as CO and CH4 were detected.

[0032] Example 5: Simulation system simultaneously absorbs carbon dioxide and sulfur dioxide in actual flue gas and realizes their resource utilization Smoke simulation device such as Figure 5 As shown, the flow rates of N2, CO2, SO2, O2, and NO were controlled to be 700 mL / min, 100 mL / min, 20 mL / min, 50 mL / min, and 10 mL / min, respectively. The mixed gas flow rate was controlled to be 600-800 mL / min, and it was continuously passed into a 400 mL aqueous solution containing 2.5 mM KI and 100 mM NaOH, and irradiated with a 254 nm ultraviolet light source for 10 hours. At the same time, 25°C circulating cooling water was used to maintain the temperature of the reaction solution, and a magnetic stirrer was used to stir the reaction solution to mix evenly, with a rotation speed of 500 rpm. The results are shown in Figure 6 As shown, after the simulation device was run for 4 hours, the formic acid production of the system was 6.69 mM, the sulfuric acid production was 53.98 mM, and the system was able to continuously produce formic acid and sulfuric acid.

[0033] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for synergistic resource utilization of carbon dioxide and sulfur dioxide in flue gas, characterized in that: The following steps are involved: (1) Using an absorption liquid containing potassium iodide to absorb carbon dioxide and sulfur dioxide in the flue gas, controlling the pH of the solution to 5.0-9.0, and obtaining a mixed solution; (2) The mixed solution obtained in step (1) is irradiated with ultraviolet light to achieve the coordinated resource utilization of carbon dioxide and sulfur dioxide, wherein the carbon dioxide is reduced to formic acid and the sulfur dioxide is converted into H2SO4.

2. The method according to claim 1, characterized in that In step (1), the absorption liquid also includes a strong alkaline solution, and the strong alkaline solution includes a sodium hydroxide solution and / or a potassium hydroxide solution.

3. The method according to claim 2, characterized in that The molar ratio of potassium iodide to strong base in the absorption liquid is (1:20) to (1:100).

4. The method according to claim 1, characterized in that In step (1), the concentration of potassium iodide in the absorption liquid is greater than 0 and less than or equal to 5 mM.

5. The method according to claim 1, characterized in that In step (1), the concentration of potassium iodide in the absorption liquid is 1-3 mM.

6. The method according to claim 1, characterized in that In step (1), the concentration of [SO2] in the mixed solution is 10~50mM.

7. The method according to claim 1, characterized in that In step (1), the concentration of [SO2] in the mixed solution is 40-50 mM.

8. The method according to claim 1, characterized in that In step (1), the pH value is 5.5 to 7.

5.

9. The method according to claim 1, characterized in that: In step (2), the ultraviolet light irradiation time is 2h~10h.

10. The method according to claim 1, characterized in that In step (2), the wavelength of the ultraviolet light in the ultraviolet light irradiation is 254 nm.

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