A method for catalytic combustion and utilization of combustible CO in sintering flue gas

Abstract

The present invention discloses a method for catalytic combustion utilization of combustible CO in sintering flue gas, belonging to the technical field of sintering flue gas treatment. The sintering flue gas successively undergoes desulfurization, wet electrostatic precipitation and denitrification treatment and then enters the reaction tower. A CO catalytic combustor is arranged in the reaction tower, and a combustion catalyst is arranged in the CO catalytic combustor. A heat exchanger is arranged between the flue gas outlet end of the reaction tower and the flue gas inlet end before denitrification treatment, so that the flue gas after combustion by the CO combustion catalytic combustor exchanges heat with the flue gas before denitrification treatment after passing through the heat exchanger; the combustion catalyst is a catalyst obtained by compounding metal oxides of manganese and cerium and palladium metal; the present invention utilizes the photocatalytic activity of the manganese-cerium composite metal oxide, uses the manganese-cerium composite metal oxide as the combustion catalyst for CO and replaces part of the noble metal palladium, and the composite catalyst can have both low cost and good low-temperature catalytic performance.

Description

Technical Field

[0001] The present invention relates to the technical field of sintering flue gas treatment, and particularly relates to a method for catalytic combustion and utilization of combustible CO in sintering flue gas. Background Art

[0002] For the treatment of steel flue gas pollutants, the control technology of sintering flue gas nitrogen oxides has received key attention. Among the existing sintering flue gas desulfurization and denitrification technologies, the currently stable sintering flue gas desulfurization and denitrification process is the wet desulfurization + medium and high temperature SCR denitrification process. The SCR flue gas denitrification technology is that under the action of appropriate temperature and catalyst, the reducing agent (liquid ammonia, ammonia water or urea) reacts with NO in the flue gas x to carry out a reduction reaction, converting NO x into N2 and H2O, thereby achieving the purpose of NO x removal. According to the different reaction temperature ranges of the SCR catalyst, the SCR denitrification technology is divided into medium and high temperature SCR denitrification technology and low temperature SCR denitrification technology. Among them, the suitable flue gas reaction temperature for the medium and high temperature SCR denitrification catalyst is 280-410°C. Therefore, the medium and high temperature SCR denitrification process needs to heat exchange / supplement heat to raise the temperature of the low-temperature flue gas after desulfurization to reach the denitrification reaction temperature. The existing heat supplement energy medium mostly uses blast furnace gas for heat exchange / supplement heat to raise the temperature.

[0003] Using blast furnace gas for heat exchange / supplement heat has a high fuel heat supplement cost and will increase carbon emissions. It should be noted that the sintering flue gas of steel mills has a low temperature and a high oxygen content. At the same time, affected by raw materials, fuels, and carbon addition, the sintering flue gas contains a large amount of combustible component CO, and its concentration is generally 6000-12000 mg / Nm3. CO is rich in chemical energy, and the oxidation to CO2 can release a large amount of heat to raise the temperature of the flue gas. After calculation, the complete oxidation of 0.48% of CO to CO2 can raise the temperature of the flue gas by 30-45°C. If the CO in the sintering flue gas is used for catalytic oxidation instead of fuel heat supplement, not only can the purpose of pollution reduction be achieved, but also the effect of carbon reduction can be obtained.

[0004] At present, the catalytic oxidation of CO usually needs to be carried out under the action of a catalyst. However, the combustion catalysts used in the existing technology are mainly noble metals, such as palladium, ruthenium, etc. They can effectively reduce the combustion oxidation temperature of CO, but the treatment cost is relatively high. Therefore, it has important practical application significance to develop a combustion catalyst with low cost and high catalytic effect. Summary of the Invention

[0005] In view of the above problems, the present invention provides a method for catalytic combustion and utilization of combustible CO in sintering flue gas.

[0006] The purpose of the present invention is achieved by the following technical solutions:

[0007] A method for catalytic combustion utilization of combustible CO in sintering flue gas. The sintering flue gas sequentially passes through desulfurization, wet electrostatic precipitation and denitrification treatment and then enters the reaction tower. A CO catalytic combustor is arranged in the reaction tower, and a combustion catalyst is arranged in the CO catalytic combustor. A heat exchanger is arranged between the flue gas outlet end of the reaction tower and the flue gas inlet end before denitrification treatment, so that the flue gas after combustion in the CO combustion catalytic combustor exchanges heat with the flue gas before denitrification treatment after passing through the heat exchanger;

[0008] The combustion catalyst is a catalyst obtained by compounding metal oxides of manganese and cerium and palladium metal.

[0009] Preferably, the preparation method of the combustion catalyst comprises the following steps:

[0010] Weigh cerium nitrate, potassium hydroxide, potassium permanganate and palladium nitrate respectively and prepare them into solutions. First, mix the cerium nitrate solution and the potassium hydroxide solution, stir and heat up to 30-40 °C, then add the potassium permanganate solution and the palladium nitrate solution, and continue to keep warm and stir for reaction for 30-60 min. After the reaction is completed, collect the precipitate, wash it several times with deionized water, dry it in vacuum, heat the dried precipitate to 400-500 °C at a rate of 5-10 °C / min and keep it calcined for 1-2 h, cool it after calcination, and obtain the combustion catalyst.

[0011] Preferably, the combustion catalyst is supported on a porous carrier, and the preparation method of the combustion catalyst comprises the following steps:

[0012] Weigh the porous carrier and disperse it in deionized water, stir and disperse it under a protective atmosphere to obtain a dispersion. Weigh cerium nitrate, potassium hydroxide, potassium permanganate and palladium nitrate respectively and prepare them into solutions. First, mix the cerium nitrate solution and the potassium hydroxide solution and add them to the dispersion, stir and heat up to 30-40 °C, then add the potassium permanganate solution and the palladium nitrate solution, and continue to keep warm and stir for reaction for 30-60 min. After the reaction is completed, collect the precipitate, wash it several times with deionized water, dry it in vacuum, heat the dried precipitate to 400-500 °C at a rate of 5-10 °C / min and keep it calcined for 1-2 h, cool it after calcination, and obtain the combustion catalyst.

[0013] Preferably, the concentration of the cerium nitrate solution is 0.3-0.5 mol / L, the concentration of the potassium hydroxide solution is 4-8 mol / L, the concentration of the potassium permanganate solution is 0.1-0.4 mol / L, the concentration of the palladium nitrate solution is 0.2-0.3 mol / L, and the molar ratio of cerium nitrate, potassium hydroxide, potassium permanganate and palladium nitrate is (3-5):(10-12):(0.4-0.5):1.

[0014] Preferably, the porous carrier is halloysite nanotubes or porous silica.

[0015] Preferably, the porous carrier is modified porous silica, and the preparation method thereof comprises the following steps:

[0016] (1) Weigh zirconium chloride and 2-aminoterephthalic acid respectively and dissolve them in dimethylformamide solvent, add acetic acid after thorough mixing, transfer to a high-pressure reactor with a polytetrafluoroethylene liner after ultrasonic dispersion, heat to 120-140° C., and keep the temperature under autogenous pressure for 40-48 hours. After the reaction is completed, cool to room temperature, separate the precipitate, wash it with anhydrous methanol several times, and vacuum dry to obtain product A;

[0017] (2) Weighing the product A and dispersing it in deionized water, adding polyvinyl pyrrolidone, yttrium chloride and sodium iodide in sequence, transferring it into a high-pressure reactor lined with polytetrafluoroethylene after ultrasonic dispersion, heating it to 160-180° C. and keeping it warm for 1-2 hours, cooling it to room temperature after the reaction is completed, separating the precipitate and washing it with anhydrous methanol for several times, and vacuum drying it to obtain product B;

[0018] (3) Weighing ethyl orthosilicate and dissolving it in anhydrous ethanol to prepare a solution with a mass concentration of 1-2%, adding 1% deionized water by volume, adjusting the pH to acidic, adding the product B at a material-liquid ratio of 1-3 g / 100 mL, and heating to 30-40° C. and stirring to react for 4-8 hours after ultrasonic dispersion. After the reaction is completed, separating the precipitate, washing with anhydrous methanol or ethanol, and vacuum drying to obtain product C;

[0019] (4) The product C is heated to 400-500° C. at a rate of 5-10° C. / min and calcined at this temperature for 1-2 hours, and then cooled to obtain the modified porous silica.

[0020] Preferably, in step (1), the mass ratio of the zirconium chloride to the 2-aminoterephthalic acid and the acetic acid is 1:(0.75-0.8):(12-14).

[0021] Preferably, the mass ratio of the product A in step (2) to the polyvinyl pyrrolidone, yttrium chloride and sodium iodide is 10:(12-15):(0.15-0.2):(5.5-5.8).

[0022] Preferably, the heat exchanger is a GGH heat exchanger.

[0023] Preferably, the reaction tower is an SCR denitration reaction tower.

[0024] The beneficial effects of the present invention are:

[0025] (1) In the present invention, a combustion catalyst is installed in the original denitration reactor. After the flue gas at the outlet of the denitration reactor exchanges heat with the flue gas before the denitration reactor, the temperature of the flue gas before the denitration reactor can be increased by about 15°C, reducing the consumption of blast furnace gas by nearly 50%. The heat supply form of the flue gas before the denitration reactor is transformed from hot blast stove heating to direct combustion heating by a burner. The direct combustion heating by the burner can combust and consume 5-8% of the combustible CO in the sintering flue gas, thereby saving the consumption of blast furnace gas.

[0026] (2) The present invention utilizes the photocatalytic activity of manganese-cerium composite metal oxides. The manganese-cerium composite metal oxides are used as the combustion catalyst for CO. By improving its combustion catalytic performance through photocatalytic activity and reducing the combustion temperature, it can be used to replace part of the noble metal palladium. When it is combined with palladium metal, it can have both low cost and good low-temperature catalytic performance. Among them, cerium oxide, as a promoter, can efficiently and rapidly transport active oxygen to the palladium component, thereby improving the catalytic performance. The present invention also uses the redox reaction between the reducing Ce(OH)3 and the oxidizing MnO4 - / Pd 2+ in the aqueous phase through a self-redox reaction to prepare a uniformly dispersed composite catalyst and improve the catalytic performance. Further, the present invention also uses a porous carrier to load the composite catalyst prepared by the self-redox reaction and in-situ uniformly coat it on the surface of the porous carrier to form an assembled structure, which can further improve the combustion catalytic performance and catalytic stability of the catalyst. Furthermore, the present invention also uses modified silica as the carrier material to achieve the efficient catalysis of CO. Specifically, the present invention uses yttrium-doped UiO-66 metal-organic framework material as a template to in-situ generate a layer of silica coating on the surface, and then heat-treat the yttrium-containing metal-organic framework wrapped with mesoporous silica to obtain yttrium-stabilized zirconia-modified silica with a multi-level pore structure. As a porous carrier with a high specific surface area, the yttrium-zirconium solid superacid loaded on it can efficiently catalyze the oxidation of CO, greatly improving its combustion catalytic performance. Specific Embodiments

[0027] The present invention will be further described in conjunction with the following embodiments.

[0028] Example 1

[0029] A method for catalytic combustion utilization of combustible CO in sintering flue gas. The sintering flue gas passes through desulfurization, wet electrostatic precipitation and denitration treatments in sequence and then enters the reaction tower. A CO catalytic burner is arranged in the reaction tower, and a combustion catalyst is arranged in the CO catalytic burner. A heat exchanger is arranged between the flue gas outlet end of the reaction tower and the flue gas inlet end before denitration treatment, so that the flue gas after combustion in the CO combustion catalytic burner exchanges heat with the flue gas before denitration treatment after passing through the heat exchanger.

[0030] The combustion catalyst is a catalyst obtained by compounding metal oxides of manganese and cerium and palladium metal;

[0031] The heat exchanger is a GGH heat exchanger;

[0032] The reaction tower is an SCR method denitration reaction tower;

[0033] The preparation method of the combustion catalyst includes the following steps:

[0034] Weigh cerium nitrate, potassium hydroxide, potassium permanganate and palladium nitrate respectively, and prepare them into solutions respectively. The concentration of the cerium nitrate solution is 0.4 mol / L, the concentration of the potassium hydroxide solution is 6 mol / L, the concentration of the potassium permanganate solution is 0.2 mol / L, and the concentration of the palladium nitrate solution is 50 mg / mL. First, mix the cerium nitrate solution and the potassium hydroxide solution, stir and heat up to 30 °C, then add the potassium permanganate solution and the palladium nitrate solution. The mixing volume ratio of the cerium nitrate solution, the potassium hydroxide solution, the potassium permanganate solution and the palladium nitrate solution is 10:2:2:5. Continue to keep warm and stir for reaction for 30 min. After the reaction is completed, collect the precipitate, wash it several times with deionized water, and dry it in vacuum. Heat the dried precipitate to 450 °C at a rate of 5-10 °C / min and keep it calcined for 2 h. After calcination, cool it to obtain the combustion catalyst.

[0035] Example 2

[0036] A method for catalytic combustion utilization of combustible CO in sintering flue gas. The sintering flue gas passes through desulfurization, wet electrostatic precipitation and denitration treatment in sequence and then enters the reaction tower. A CO catalytic combustor is arranged in the reaction tower, and a combustion catalyst is arranged in the CO catalytic combustor. A heat exchanger is arranged between the flue gas outlet end of the reaction tower and the flue gas inlet end before denitration treatment, so that the flue gas after combustion in the CO combustion catalytic combustor exchanges heat with the flue gas before denitration treatment after passing through the heat exchanger;

[0037] The combustion catalyst is a catalyst obtained by compounding metal oxides of manganese and cerium and palladium metal;

[0038] The heat exchanger is a GGH heat exchanger;

[0039] The reaction tower is an SCR method denitration reaction tower;

[0040] The preparation method of the combustion catalyst includes the following steps:

[0041] Weigh the halloysite nanotubes and disperse them in deionized water at a solid-liquid ratio of 10 g / 100 mL to obtain a dispersion; weigh cerium nitrate, potassium hydroxide, potassium permanganate and palladium nitrate respectively and prepare them into solutions, wherein the concentration of the cerium nitrate solution is 0.4 mol / L, the concentration of the potassium hydroxide solution is 6 mol / L, the concentration of the potassium permanganate solution is 0.2 mol / L, and the concentration of the palladium nitrate solution is 50 mg / mL; first mix the cerium nitrate solution and the potassium hydroxide solution and add them to the The dispersion is stirred and heated to 30°C, and then potassium permanganate solution and palladium nitrate solution are added, wherein the mixing volume ratio of the cerium nitrate solution, potassium hydroxide solution, potassium permanganate solution and palladium nitrate solution is 10:10:2:2:5, and the reaction is continued by keeping warm and stirring for 30 minutes. After the reaction is completed, the precipitate is collected, washed with deionized water for several times, and vacuum dried. The dried precipitate is heated to 450°C at a rate of 5-10°C / min and kept warm for calcination for 2 hours, and cooled after calcination to obtain the combustion catalyst.

[0042] Example 3

[0043] A method for utilizing combustible CO in sintering flue gas through catalytic combustion, wherein the sintering flue gas is sequentially subjected to desulfurization, wet electrostatic precipitator and denitration treatment and then enters a reaction tower, wherein a CO catalytic burner is arranged in the reaction tower, wherein a combustion catalyst is arranged in the CO catalytic burner, and a heat exchanger is arranged between a flue gas outlet end of the reaction tower and a flue gas inlet end before denitration treatment, so that the flue gas after combustion in the CO combustion catalyst passes through the heat exchanger and exchanges heat with the flue gas before denitration treatment;

[0044] The combustion catalyst is a catalyst obtained by compounding metal oxides of manganese and cerium and palladium metal;

[0045] The heat exchanger is a GGH heat exchanger;

[0046] The reaction tower is an SCR denitration reaction tower;

[0047] The preparation method of the combustion catalyst is the same as that of Example 2, except that the halloysite nanotubes are replaced by an equal amount of modified porous silica. The preparation method of the modified porous silica comprises the following steps:

[0048] (1) Weigh zirconium chloride and 2-aminoterephthalic acid respectively and dissolve them in dimethylformamide solvent, add acetic acid after fully mixing, transfer to a high-pressure reactor with a polytetrafluoroethylene liner after ultrasonic dispersion, heat to 120-140° C., and keep the temperature under autogenous pressure for 40-48 hours. After the reaction is completed, cool to room temperature, separate the precipitate, wash it with anhydrous methanol several times, and vacuum dry to obtain product A; wherein the mass ratio of the zirconium chloride to the 2-aminoterephthalic acid and the acetic acid is 1:0.77:12;

[0049] (2) Weigh the product A and disperse it in deionized water. Then, successively add polyvinylpyrrolidone, yttrium chloride, and sodium iodide. After ultrasonic dispersion, transfer it to a high-pressure reactor with a polytetrafluoroethylene liner. Heat it to 160 - 180 °C and keep it warm for reaction for 1 - 2 h. After the reaction is completed, cool it to room temperature naturally. Separate the precipitate and wash it several times with anhydrous methanol, and then dry it under vacuum to obtain product B. Among them, the mass ratio of the product A to the polyvinylpyrrolidone, yttrium chloride, and sodium iodide is 10:14:0.156:5.6;

[0050] (3) Weigh tetraethyl orthosilicate and dissolve it in anhydrous ethanol to prepare a solution with a mass concentration of 1.2%. Add 1% deionized water by volume fraction, adjust the pH to 4 - 5, and add the product B according to the material-liquid ratio of 1.5 g / 100 mL. After ultrasonic dispersion, heat it to 30 - 40 °C and keep it warm and stir for reaction for 5 h. After the reaction is completed, separate the precipitate, wash it with anhydrous ethanol, and dry it under vacuum to obtain product C;

[0051] (4) Heat the product C to 450 °C at a rate of 5 - 10 °C / min and keep it warm and calcine for 1.5 h. After cooling, the modified porous silica is obtained.

[0052] Example 4

[0053] A method for catalytic combustion utilization of combustible CO in sintering flue gas. The sintering flue gas successively passes through desulfurization, wet electrostatic precipitation, and denitrification treatments and then enters the reaction tower. A CO catalytic combustor is arranged in the reaction tower, and a combustion catalyst is arranged in the CO catalytic combustor. A heat exchanger is arranged between the flue gas outlet end of the reaction tower and the flue gas inlet end before denitrification treatment, so that the flue gas after combustion in the CO combustion catalytic combustor exchanges heat with the flue gas before denitrification treatment after passing through the heat exchanger;

[0054] The combustion catalyst is a catalyst obtained by compounding metal oxides of manganese and cerium and palladium metal;

[0055] The heat exchanger is a GGH heat exchanger;

[0056] The reaction tower is an SCR method denitrification reaction tower;

[0057] The preparation method of the combustion catalyst is the same as that in Example 2, except that the halloysite nanotubes are replaced with an equal amount of porous silica. The preparation method of the porous silica includes the following steps:

[0058] Weigh tetraethyl orthosilicate and dissolve it in absolute ethanol to prepare a solution with a mass concentration of 1.2%. Add 1% deionized water by volume fraction, adjust the pH to 4 - 5, disperse it by ultrasonic wave, then heat it up to 30 - 40 °C and keep stirring for reaction for 5 h. After the reaction is completed, separate the precipitate, wash it with absolute ethanol, dry it in vacuum, then heat it up to 450 °C at a rate of 5 - 10 °C / min and keep calcining for 1.5 h, and cool it to obtain the product.

[0059] Example 5

[0060] A combustion catalyst for CO, and the catalyst is palladium metal.

[0061] Experimental Example

[0062] Measure the catalytic performance of the combustion catalysts described in Examples 1 - 5 under natural light conditions in a simulated fixed - bed reactor. The inner diameter of the quartz tube reactor is 4 cm, and the outer diameter is 4.3 cm. The catalyst is placed inside the quartz tube reactor, and a thermocouple is set at the position of the catalyst for temperature measurement. The catalyst filling amount is 5 g (excluding the mass of the porous support). The mixed gas consists of CO (V% = 2.5%), O2 (V% = 3%), and N2 (V% = 94.5%). Measure the CO conversion rate at different temperatures, and the measurement results are as follows:

[0063]

[0064] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention, rather than limiting the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for catalytic combustion and utilization of combustible CO in sintering flue gas, characterized in that, The sintering flue gas is sequentially treated with desulfurization, wet electrostatic precipitator and denitrification before entering the reaction tower. A CO catalytic burner is arranged in the reaction tower. A combustion catalyst is arranged in the CO catalytic burner. A heat exchanger is arranged between the flue gas outlet end of the reaction tower and the flue gas inlet end before denitrification treatment, so that the flue gas after combustion in the CO combustion catalyst exchanges heat with the flue gas before denitrification treatment after passing through the heat exchanger. The combustion catalyst is a catalyst obtained by compositely loading metal oxides of manganese and cerium and palladium metal on a porous carrier; the preparation method thereof comprises the following steps: Weigh the porous carrier and disperse it in deionized water, stir and disperse it under a protective atmosphere to obtain a dispersion, weigh cerium nitrate, potassium hydroxide, potassium permanganate and palladium nitrate respectively, and prepare them into solutions respectively, first mix the cerium nitrate solution and the potassium hydroxide solution and add them to the dispersion, stir and heat to 30-40° C., then add the potassium permanganate solution and the palladium nitrate solution, continue to stir and react for 30-60 minutes, collect the precipitate after the reaction is completed, wash it with deionized water several times, and vacuum dry it, heat the dried precipitate to 400-500° C. at a rate of 5-10° C. / min and heat it for 1-2 hours, cool it after calcination, and obtain the combustion catalyst; The porous carrier is modified porous silica, and its preparation method comprises the following steps: (1) Weigh zirconium chloride and 2-aminoterephthalic acid respectively and dissolve them in dimethylformamide solvent, add acetic acid after thorough mixing, transfer to a high-pressure reactor with a polytetrafluoroethylene liner after ultrasonic dispersion, heat to 120-140° C., and keep the temperature under autogenous pressure for 40-48 hours. After the reaction is completed, cool to room temperature, separate the precipitate, wash it with anhydrous methanol several times, and vacuum dry to obtain product A; (2) Weighing the product A and dispersing it in deionized water, adding polyvinyl pyrrolidone, yttrium chloride and sodium iodide in sequence, transferring it into a high-pressure reactor lined with polytetrafluoroethylene after ultrasonic dispersion, heating it to 160-180° C. and keeping it warm for 1-2 hours, cooling it to room temperature after the reaction is completed, separating the precipitate and washing it with anhydrous methanol for several times, and vacuum drying it to obtain product B; (3) Weighing ethyl orthosilicate and dissolving it in anhydrous ethanol to prepare a solution with a mass concentration of 1-2%, adding 1% deionized water by volume, adjusting the pH to acidic, adding the product B at a material-liquid ratio of 1-3 g / 100 mL, and heating to 30-40° C. and stirring to react for 4-8 hours after ultrasonic dispersion. After the reaction is completed, separating the precipitate, washing with anhydrous methanol or ethanol, and vacuum drying to obtain product C; (4) The product C is heated to 400-500° C. at a rate of 5-10° C. / min and calcined at this temperature for 1-2 hours, and then cooled to obtain the modified porous silica.

2. The method for catalytic combustion utilization of combustible CO in sintering flue gas according to claim 1, characterized in that, The concentration of the cerium nitrate solution is 0.3 - 0.5 mol / L, the concentration of the potassium hydroxide solution is 4 - 8 mol / L, the concentration of the potassium permanganate solution is 0.1 - 0.4 mol / L, the concentration of the palladium nitrate solution is 0.2 - 0.3 mol / L, and the molar ratio of cerium nitrate, potassium hydroxide, potassium permanganate and palladium nitrate is (3 - 5):(10 - 12):(0.4 - 0.5):

1.

3. A method for catalytic combustion and utilization of combustible CO in sintering flue gas according to claim 1, characterized in that, In step (1), the mass ratio of zirconium chloride, 2-aminoterephthalic acid and acetic acid is 1:(0.75 - 0.8):(12 - 14).

4. A method for catalytic combustion utilization of combustible CO in sintering flue gas according to claim 1, characterized in that, In step (2), the mass ratio of product A, polyvinylpyrrolidone, yttrium chloride and sodium iodide is 10:(12 - 15):(0.15 - 0.2):(5.5 - 5.8).

5. A method for catalytic combustion utilization of combustible CO in sintering flue gas according to claim 1, characterized in that, The heat exchanger is a GGH heat exchanger.

6. A method for catalytic combustion utilization of combustible CO in sintering flue gas according to claim 1, characterized in that, The reaction tower is an SCR denitration reaction tower.

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