A method for the collaborative resource utilization of carbon dioxide and sulfur dioxide in flue gas

Abstract

The present invention relates to a method for the collaborative resource utilization of carbon dioxide and sulfur dioxide in flue gas. The method includes: (1) using an absorbent solution containing potassium iodide to absorb carbon dioxide and sulfur dioxide in the flue gas, controlling the pH of the solution to be 5.0 - 9.0 to obtain a mixed solution; (2) irradiating the mixed solution obtained in step (1) with ultraviolet light to achieve the collaborative resource utilization of carbon dioxide and sulfur dioxide, wherein carbon dioxide is reduced to formic acid and sulfur dioxide is converted to sulfuric acid. The present invention provides a method for the collaborative resource utilization of CO2 and SO2 in flue gas. It has high efficiency in reducing CO2 to formic acid and converting SO2 to H2SO4, mild reaction conditions, without the need for high temperature and high pressure, and without the addition of an external electron / proton sacrificial agent, and is a resource utilization technology with practical application prospects.

Description

Technical Field

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

[0002] As important components in the flue gas of thermal power plants, metal smelters and cement plants, the large emissions of carbon dioxide and sulfur dioxide will cause serious environmental pollution problems such as the greenhouse effect, frequent extreme weather and acid rain. With the development of global warming and "low-carbon economy", such problems have attracted extensive attention from scientific researchers.

[0003] Resource utilization is the best way to solve such problems. CO2 reduction is the main way for CO2 resource utilization. Among the reduction products of CO2, the least number of protons and electrons need to be transferred to generate formic acid. And formic acid is an excellent liquid hydrogen storage fuel and biochemistry raw material, which is widely used in many fields. Traditional CO2 reduction methods mainly include electrochemical method, photocatalytic method and thermochemical method, etc. 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), resulting in problems such as harsh reaction conditions, low efficiency and poor selectivity in the reduction of CO2 to produce HCOOH by traditional methods. The resource utilization ways of SO2 mainly include: oxidation to produce acid, reduction to elemental sulfur and synthesis of organic molecules through organic reactions, etc. However, these processes usually require the addition of catalysts, sacrificial agents, oxidants and reductants, etc. Therefore, the CO2 and SO2 resource utilization systems usually have problems such as high cost, low efficiency caused by competitive side reactions and harsh reaction conditions caused by high reaction energy barriers. Summary of the Invention

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

[0005] The present invention provides a method for the synergistic resource utilization of carbon dioxide and sulfur dioxide in flue gas, including the following steps:

[0006] (1). Absorb carbon dioxide and sulfur dioxide in the flue gas with an absorption solution containing potassium iodide, control the pH of the solution to be 5.0 - 9.0, and obtain a mixed solution;

[0007] (2) The mixed solution obtained in step (1) is irradiated with ultraviolet light to achieve the synergistic resource utilization of carbon dioxide and sulfur dioxide. Among them, carbon dioxide is reduced to formic acid, and sulfur dioxide is converted to H2SO4.

[0008] In some embodiments of the present invention, in step (1), CO2 and SO2 in the flue gas are important components in the flue gas of coal-fired power plants, metal smelters, cement plants, etc.

[0009] In some embodiments of the present invention, in step (1), the absorption liquid further includes a strong base solution, and the strong base solution includes sodium hydroxide solution and / or potassium hydroxide solution.

[0010] 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). Exemplarily, it can be 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, etc.

[0011] 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. Exemplarily, 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.

[0012] In some embodiments of the present invention, in step (1), the concentration of potassium iodide in the absorption liquid is 1 to 3 mM.

[0013] In some embodiments of the present invention, in step (1), the concentration of [SO2] in the mixed solution is 10 to 50 mM. Exemplarily, it can be 10 mM, 20 mM, 30 mM, 40 mM, 50 mM, etc. The [SO2] includes SO2 and its derivative HSO3 - , SO3 2- .

[0014] In some embodiments of the present invention, in step (1), the concentration of [SO2] in the mixed solution is 40 to 50 mM.

[0015] In some embodiments of the present invention, in step (1), the pH value is 5.5 to 7.5. Exemplarily, it can be 5.5, 6.0, 7.0, 7.5, etc.

[0016] In some embodiments of the present invention, in step (2), the time of ultraviolet light irradiation is 2 h to 10 h.

[0017] In some embodiments of the present invention, in step (2), the wavelength of the ultraviolet light in the ultraviolet light irradiation is 254 nm.

[0018] In the present invention, the method uses an absorption liquid to simultaneously absorb CO2 and SO2 in flue gas. After being absorbed, SO2 can be converted into its derivative Na2SO3. Na2SO3 and KI can generate hydrated electrons that can activate CO2 under ultraviolet light irradiation. H + / H2O and / or HSO3 - in the system can provide protons for the carbon dioxide reduction process. During the reaction process, CO2 is activated to CO2 ·- , and then a sufficient proton source protonates it to highly selectively generate HCOOH. SO2 is converted into H2SO4, and KI can be recycled with the participation of SO2. In the experiment, the CO2 conversion rate was 99.88% after 4 h of reaction, and the HCOOH selectivity was 96.58%; SO2 and its derivatives were converted into H2SO4, and the conversion rate after 4 h was 87.26%. The concentration of KI in the system remained almost unchanged. In the simulated flue gas experiment, the system could continuously produce formic acid.

[0019] The above technical solution of the present invention has the following advantages compared with the prior art:

[0020] 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.

[0021] 2. This method has mild reaction conditions, does not require high temperature and high pressure, and does not require an external electron / proton sacrificial agent.

[0022] 3. The CO2 conversion rate of this method is as high as 99.88%, and the formic acid selectivity in the product is as high as 96.58%.

[0023] 4. The only product of SO2 conversion by this method is H2SO4. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to make the content of the present invention easier to be clearly understood, the following further details the present invention according to specific embodiments of the present invention in combination with the drawings, wherein,

[0025] Figure 1 is the detection result of the reaction solution in Example 1 of the present invention; wherein, (a) is a performance comparison diagram of formic acid production by reducing CO2 in the SO2 + KI system, and (b) is a diagram of the concentration changes of SO3 2- / SO4 2- and I - in the system during the reaction process;

[0026] Figure 2Detection results of the reaction solution in Example 2 of the present invention; among them, (a) shows the influence of different concentrations of KI and (b) shows the influence of different concentrations of [SO2] on the reduction of CO2 to formic acid in the system;

[0027] Figure 3 Detection result diagram of the reaction solution in Example 3 of the present invention;

[0028] Figure 4 Detection result diagram of the concentration of carbon dioxide reduction products in the reaction solution in Example 4 of the present invention;

[0029] Figure 5 Simulation flue gas absorption and conversion device diagram of the present invention; where 1. N2, 2. SO2, 3. CO2, 4. O2, 5. NO, 6. Cylinder pressure reducing valve, 7. Flowmeter, 8. Gas mixing device, 9. Total gas mixing valve, 10. Gas heater, 11. Photoreactor, 12. Bubble distribution plate, 13. Magnetic stirrer, 14. Ultraviolet lamp, 15. Tail gas absorption device;

[0030] Figure 6 Diagram of the formic acid and sulfuric acid production in the simulated flue gas absorption and conversion system in Example 5 of the present invention. Detailed implementation manners

[0031] The present invention will be 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 be able to implement it, but the exemplified embodiments are not intended to limit the present invention.

[0032] Example 1: Reduction of CO2 to HCOOH by the SO2 + KI system

[0033] Verify the feasibility and performance of the synergistic resource utilization of the reduction of CO2 to HCOOH by the SO2 and KI system and the production of H2SO4 from SO2. High-purity SO2 and CO2 are selected as reaction gases, and under the irradiation of a 254 nm ultraviolet lamp, the yields of HCOOH and SO4 2- are measured. The steps are as follows:

[0034] (1) CO2 is introduced into 400 mL of deionized water at 25 °C for 30 minutes (the saturated concentration of CO2 under this condition is 33 mM). Appropriate amounts of NaOH and KI are added, and their concentrations are 100 mM and 2.5 mM respectively. High-purity SO2 is introduced, and the gas flow rate is controlled at 100 mL / min. The concentration of [SO2] (including SO2 and its derivatives HSO3 - and SO3 2- ) in the solution is measured by ion chromatography. When the concentration of [SO2] reaches 50 mM, the gas supply is stopped. And the pH is adjusted to 6.5 using NaOH / H2SO4 solution.

[0035] (2) Irradiate the solution obtained in step (1) with a 254 nm ultraviolet light source for 10 h. At the same time, use circulating cooling water at 25 °C to maintain the temperature of the reaction solution, and use a magnetic stirrer to stir the reaction solution to make it mix evenly at a rotation speed of 500 rpm. At the same time, use the single systems of SO2 and KI as control experiments respectively.

[0036] (3) Detect the carbon dioxide conversion rate, formic acid selectivity and SO2 conversion rate of the system. The experimental results are as Figure 1 shown. The carbon dioxide conversion rate of the system is 99.88% after reacting for 4 h, and the formic acid selectivity is 96.58%, which is significantly better than the single SO2 or KI system; SO2 is converted into H2SO4, and the conversion rate is 87.26% after 4 h. The concentration of KI in the system remains almost unchanged and there is no need to add it repeatedly.

[0037] Example 2: Reduction of CO2 to produce HCOOH by the SO2 + KI system at different [SO2] and KI concentrations

[0038] (1) Introduce CO2 into 400 mL of deionized water at 25 °C for 30 minutes (the saturated concentration of CO2 under this condition is 33 mM). Add NaOH and KI so that their concentrations are in the ranges of 0 - 100 mM and 0 - 5 mM respectively. Introduce high-purity SO2, control the gas flow rate at 100 mL / min, and use ion chromatography to measure the [SO2] (including SO2 and its derivatives HSO3 - 、SO3 2- ) concentration in the solution. Stop ventilation when the [SO2] concentration reaches the required experimental concentration. Use NaOH / H2SO4 solution to adjust the pH to 6.5.

[0039] (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, and use a magnetic stirrer to stir the reaction solution to make it mix evenly at a rotation speed of 500 rpm. Detect the formic acid production and carbon dioxide conversion rate of the system. The experimental results are as Figure 2 shown. When the [SO2] concentration is fixed at 50 mM, when the KI concentrations are 2.0 mM, 2.5 mM and 3.0 mM, the formic acid production effect of the system is better. The formic acid productions after 4 h are 31.09 mM, 32.56 mM and 32.67 mM respectively, and the carbon dioxide conversion rates are 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 formic acid production effect of the system is better. The formic acid production after 4 h is 32.56 mM, and the carbon dioxide conversion rate is 98.67%.

[0040] Example 3: Reduction of CO2 to produce HCOOH by the SO2 + KI system under different pH conditions.

[0041] (1) 25 °C, 400 mL of deionized water was purged with CO2 for 30 minutes (the saturated concentration of CO2 under this condition was 33 mM). Appropriate amounts of NaOH and KI were added, with their concentrations being 100 mM and 2.5 mM respectively. High-purity SO2 was purged, controlling the gas flow rate at 100 mL / min. The [SO2] (including SO2 and its derivative HSO3 - and SO3 2- ) concentration in the solution was measured using ion chromatography. When the [SO2] concentration reached 50 mM, the gas purging was stopped. The pH was adjusted to 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 9.0 using NaOH / H2SO4 solution.

[0042] (2) The solution obtained in step (1) was irradiated with a 254 nm ultraviolet light source for 10 h. A 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 make it evenly mixed, with a rotation speed of 500 rpm. The formic acid production and CO2 conversion rate of the system were detected. The experimental results are as Figure 3 shown. The system had better formic acid production effect at pH 5.5 - 7.5.

[0043] Example 4

[0044] The other products in the reaction solution after 4 h of reaction in step (2) of Example 1 were detected and analyzed. The detection results are as Figure 4 shown. The selectivity of formic acid in the products was as high as 96.39%, and the selectivities of by-products such as methanol, oxalic acid, acetic acid, and ethanol were 1.98%, 1.48%, 0.11%, and 0.04% respectively. In addition, only trace amounts of gas products such as CO and CH4 were detected.

[0045] Example 5: Simulating the system to simultaneously absorb carbon dioxide and sulfur dioxide in actual flue gas and realize their resource utilization

[0046] The simulated flue gas device is as Figure 5 shown. The flow rates of N2, CO2, SO2, O2, and NO were controlled at 700 mL / min, 100 mL / min, 20 mL / min, 50 mL / min, and 10 mL / min respectively. The flow rate of the mixed gas was controlled at 600 - 800 mL / min, and it was continuously introduced into 400 mL of an aqueous solution containing 2.5 mM KI and 100 mM NaOH, and irradiated with a 254 nm ultraviolet light source for 10 h. At the same time, a 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 make it evenly mixed, with a rotation speed of 500 rpm. The results are as Figure 6 shown. After the simulated device ran for 4 h, the formic acid production of the system was 6.69 mM, the sulfuric acid production was 53.98 mM, and the system could continuously produce formic acid and sulfuric acid.

[0047] Obviously, the above embodiments are merely examples for clear illustration and are not limitations on the implementation manners. For those of ordinary skill 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 enumerate all implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. A method for the collaborative resource utilization of carbon dioxide and sulfur dioxide in flue gas, characterized in that, It includes the following steps: (1) Absorb carbon dioxide and sulfur dioxide in flue gas with an absorbent containing potassium iodide, and control the pH of the solution to be 5.0 - 9.0 to obtain a mixed solution; (2) Irradiate the mixed solution obtained in step (1) with ultraviolet light to achieve the synergistic resource utilization of carbon dioxide and sulfur dioxide. Among them, carbon dioxide is reduced to formic acid, and sulfur dioxide is converted to H2SO4.

2. The method according to claim 1, wherein In step (1), the absorbent further includes a strong base solution, and the strong base solution includes sodium hydroxide solution and / or potassium hydroxide solution.

3. The method according to claim 2, wherein The molar ratio of potassium iodide to strong base in the absorbent is (1:20) - (1:100).

4. The method according to claim 1, wherein In step (1), the concentration of potassium iodide in the absorbent 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 absorbent 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 - 50 mM.

7. The method according to claim 1, wherein 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 - 7.

5.

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

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

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