Cerium-based fluorite type composite catalyst as well as preparation method and application thereof

Abstract

The invention discloses a cerium-based fluorite type composite catalyst and a preparation method and application thereof, and the preparation method specifically comprises the following steps: (1) grinding a metal oxide carrier, and drying to constant weight to obtain a carrier component; (2) dissolving cerous nitrate and metal nitrate in water to obtain a nitrate solution; and (3) adding the carrier component into the nitrate solution, stirring, adding urea, uniformly mixing, ultrasonically dispersing, heating, reacting, cooling to room temperature, centrifuging, washing, drying, grinding, calcining, cooling to room temperature, and sieving to obtain the catalyst. By means of the method, emission reduction of CO in the sintering flue gas, efficient utilization of the heat value and removal of SO2 are achieved, the rear-end SCR catalyst is well protected, and the method has remarkable industrial application prospects and economic value.

Description

Technical Field

[0001] The present invention relates to the technical field of deep treatment of sintering flue gas, and more particularly to a cerium-based fluorite-type composite catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] In the sintering process of the iron and steel industry, a large amount of air pollutants are generated, including particulate matter, sulfur dioxide (SO 2 ), nitrogen oxides (NO X ), and carbon monoxide (CO). At present, the treatment of sintering flue gas usually adopts a combined process of "dust collector + limestone-gypsum method for desulfurization + flue gas reheating device + SCR denitration" to remove particulate matter, SO 2 and NO x , but this key pollutant CO is discharged into the atmosphere without treatment (the CO content is about 5000-15000 mg / m 3 ). CO is a seriously harmful air pollutant that may cause extreme damage to the environment, vegetation, and even the life safety of animals and humans. Therefore, reducing the emission of CO not only helps enterprises achieve carbon emission reduction goals, but also creates more economic value in the carbon trading market.

[0003] In recent years, with the continuous improvement of environmental awareness and the increasing strictness of environmental protection regulations, the low-temperature and efficient removal of CO in sintering flue gas has received more and more attention. In addition, although the existing wet limestone-gypsum method for desulfurization can effectively remove SO 2 , there is still 50-100 mg / m 3 of SO 2 remaining in the atmosphere, and the presence of SO 2 will inevitably cause the SCR catalyst in the denitration system to be poisoned and inactivated, seriously affecting the denitration efficiency. Since the flue gas temperature drops to 45-60 °C after the wet desulfurization process, it usually needs to be heated to 280-410 °C by consuming a large amount of blast furnace gas before entering the SCR denitration system to meet the requirements of medium- and high-temperature SCR denitration, which undoubtedly increases the energy cost of enterprises.

[0004] According to the traditional sintering flue gas treatment process, after the sintering flue gas is treated by an electrostatic precipitator for dust removal and a wet desulfurization method with limestone-gypsum, there is still a small amount of SO 2, and a large amount of CO in the sintering flue gas is not removed, and a large amount of blast furnace gas needs to be consumed for flue gas reheating before entering the denitration system. CO has a high calorific value and significant reducibility. The combustion heat (molar calorific value) of CO is about 283 kJ / mol, and the reducibility of CO also has extensive applications in industry. Therefore, by utilizing the calorific value and reducibility of CO, not only can the CO emissions in the sintering flue gas be reduced, the energy consumption of enterprises be lowered, but also through the reduction of CO, the low-concentration SO 2 remaining after wet desulfurization can be reduced to elemental sulfur for recovery, thereby reducing the impact of SO 2 on the poisoning and inactivation of the catalyst in the subsequent denitration system.

[0005] Currently, the problem with utilizing the calorific value of CO is that the complete conversion temperature of CO is relatively high, and it needs to be heated to a relatively high temperature by a flue gas reheater (GGH) to have a high utilization efficiency for CO in the flue gas. For example, CN 116447886A uses a manganese-cerium composite metal oxide as a combustion catalyst for CO, and the complete conversion temperature of CO still needs to reach 250 °C, and the preparation process is relatively complex. In addition, regarding the impact of the residual SO 2 in the flue gas after wet desulfurization, existing research mainly focuses on optimizing the pore structure of the SCR catalyst to improve its sulfur resistance performance.

[0006] Therefore, how to achieve the complete conversion of CO at a lower temperature while reducing the impact of SO 2 on the SCR denitration system is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a cerium-based fluorite-type composite catalyst, its preparation method and application to solve the deficiencies in the prior art.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions:

[0009] A preparation method of a cerium-based fluorite-type composite catalyst specifically includes the following steps:

[0010] (1) Grind the metal oxide carrier to make its particle size uniform, and dry it to constant weight to remove the moisture and volatile impurities on its surface, obtaining the carrier component;

[0011] (2) Dissolve cerium nitrate and metal nitrate in water to obtain a nitrate solution;

[0012] (3) Add the carrier component to the nitrate solution, stir, add urea, mix evenly, disperse ultrasonically, raise the temperature for reaction, cool to room temperature, centrifuge, wash, dry, grind, calcine, cool to room temperature, and sieve to obtain the cerium-based fluorite-type composite catalyst.

[0013] Further, in the above step (1), the metal oxide support is at least one of titanium dioxide, silicon dioxide, cobalt tetroxide, and aluminum oxide.

[0014] The beneficial effect of the above is that the selected metal oxide as the support in the present invention has a high specific surface area and pore structure, can uniformly disperse the active components, provide abundant reaction active sites, significantly improve the catalytic efficiency, and also has excellent thermal stability.

[0015] Further, in the above step (2), the metal nitrate is at least one of iron nitrate, cobalt nitrate, copper nitrate, nickel nitrate, manganese nitrate, and silver nitrate.

[0016] The beneficial effect of the above is that the selected metal nitrate in the present invention has adjustable chemical properties, redox activity, and structural advantages.

[0017] Further, in the above step (2), the mass ratio of cerium nitrate to the metal nitrate is (5 - 10):1; the mass of cerium nitrate is 40% - 60% of the mass of the metal oxide support; the dosage ratio of the metal oxide support to urea is (2 - 8) g:(20 - 80) mmol.

[0018] The beneficial effect of the above is that the present invention uses cerium nitrate to form cerium oxide on the catalyst surface. Cerium can reversibly convert between Ce 3+ and Ce 4+ , promote electron transfer by releasing oxygen vacancies, and significantly improve the redox activity of the catalyst. Urea can slowly hydrolyze in the solution to generate NH 3 , gradually increase the pH value of the reaction system, make the metal ions precipitate uniformly, help to form highly dispersed active components, and avoid particle agglomeration caused by local supersaturation; secondly, the gases (such as CO 2 , NH 3 ) generated by the decomposition of urea can form a porous structure and increase the specific surface area of the catalyst.

[0019] Further, in the above step (3), the time for ultrasonic dispersion is 30 - 60 min; the temperature for the temperature-rising reaction is 70 - 150 °C, and the time is 6 - 18 h.

[0020] The beneficial effect of the above is that the selected hydrothermal method for temperature rising in the present invention can regulate the crystal growth of the catalyst, optimize the microstructure, and enhance the active sites, realizing the precise design of the catalyst performance.

[0021] Further, in the above step (3), the heating rate of calcination is 1-5 °C / min, the temperature is 300-700 °C, and the time is 1-8 h; the drying temperature is 110-130 °C, and the time is 16-24 h; the mesh number of the sieve for sieving is 40-60 meshes.

[0022] The beneficial effects of the above further steps are as follows: The calcination selected in the present invention can remove the residual organic matter, moisture and volatile impurities of the catalyst precursor, promote the strong interaction between the metal active component and the metal oxide support, and induce the generation of oxygen vacancies and surface defects on the metal oxide support.

[0023] The present invention also claims a cerium-based fluorite-type composite catalyst prepared by the above preparation method.

[0024] The present invention also claims an application of the cerium-based fluorite-type composite catalyst prepared by the above preparation method in treating sintering flue gas.

[0025] A method for CO emission reduction, calorific value utilization and SO 2 reduction before a sintering flue gas denitrification system, specifically comprising the following steps: adding a CO catalytic reaction device and a sulfur capture device before the hot blast stove process before the sintering flue gas denitrification system. The CO catalytic reaction device is provided with the cerium-based fluorite-type composite catalyst prepared by the above preparation method. The sintering flue gas sequentially passes through a dust collector, a desulfurization system, a flue gas reheater 1 (using the flue gas at the outlet of the denitrification reaction tower to exchange heat with the desulfurized flue gas), a CO catalytic reaction device, a sulfur capture device, a flue gas reheater 2 (using the flue gas at the outlet of the CO catalytic reaction device to exchange heat with the flue gas at the outlet of the sulfur capture device), and is heated by a hot blast stove to the temperature required for medium-temperature denitrification in SCR and then enters the denitrification reaction tower for denitrification treatment.

[0026] Further, the above dust collector is an electrostatic precipitator; the desulfurization system adopts the wet limestone-gypsum desulfurization method; the flue gas reheater 1 and the flue gas reheater 2 are regenerative flue gas reheaters (GGH heat exchangers); the hot blast stove is an external heating furnace; the denitrification reaction tower is an SCR method denitrification reaction tower.

[0027] It can be seen from the above technical solutions that, compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. The cerium-based fluorite-type composite catalyst of the present invention selects TiO 2 , SiO 2 , Co 3 O 4 and Al 2 O 3Common metal oxides such as 2 are used as carriers, and the active components are one or more metals such as Fe, Co, Cu, Ni, Mn, Ag, and Ce. The active components account for 5wt%-15wt% of the total mass of the catalyst. This catalyst can not only efficiently convert CO in sintering flue gas at low temperatures, but also reduce SO 2 to elemental sulfur by means of heat exchange at both ends, utilize a large amount of heat energy released by the CO oxidation reaction to effectively heat the flue gas before entering the denitration system, and at the same time reduce SO 2 to avoid poisoning the subsequent SCR catalyst, thereby achieving the reduction of CO emissions in sintering flue gas, the efficient utilization of calorific value, and the removal of SO

[0029] 2. The present invention reduces the complete conversion temperature of CO with the help of a cerium-based fluorite-type composite catalyst, and at the same time reduces a small amount of residual SO 2 after wet flue gas desulfurization to elemental sulfur for recovery. It can not only greatly reduce the CO emissions in sintering flue gas, but also reduce the production cost of enterprises using blast furnace gas for heat compensation due to the heat generated by CO oxidation. Moreover, it further reduces the SO 2 concentration in the flue gas and reduces the impact of SO 2 on the subsequent SCR denitration system.

[0030] 3. The present invention realizes the complete oxidation of CO at low temperatures with a cerium-based fluorite-type composite catalyst, reducing the CO emissions in sintering flue gas.

[0031] 4. The present invention reduces the use of a large amount of blast furnace gas by using the calorific value of CO. The data of the examples show that by using the heat generated by CO oxidation in the flue gas, 1.6×10 8 m 3 of blast furnace gas can be reduced annually.

[0032] 5. The cerium-based fluorite-type composite catalyst of the present invention has a large number of oxygen vacancies and their mobility, and can convert part of the SO 2 after flue gas desulfurization into sulfur for recovery, which not only has great economic benefits, but also reduces the impact of SO 2 on the subsequent SCR catalyst. Detailed implementation manners

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] Example 1

[0035] A preparation method of a cerium-based fluorite-type composite catalyst specifically includes the following steps:

[0036] (1) Grind 4 g of titanium dioxide and dry it to constant weight to obtain a carrier component;

[0037] (2) Dissolve cerium nitrate and iron nitrate with a mass ratio of 5:1 in deionized water to obtain a nitrate solution;

[0038] (3) Add the carrier component to the nitrate solution, stir it using a magnetic stirrer, add 60 mmol of urea during the stirring process, mix evenly, ultrasonically disperse the obtained suspension for 30 min, then transfer it to a reaction kettle, raise the temperature to 120 °C in a forced-air drying oven and react for 18 h. After the reaction is completed, cool it to room temperature, separate the precipitate by a high-speed centrifuge, wash it 3 times with pure water, then put it into a forced-air drying oven and dry it at 110 °C for 24 h. Grind the obtained catalyst precursor and put it into a muffle furnace, raise the temperature to 500 °C at a rate of 1 °C / min and calcine for 2 h. After completion, naturally cool it to room temperature, and sieve the obtained powder through a 40-60 mesh sieve to obtain the cerium-based fluorite-type composite catalyst.

[0039] Example 2

[0040] A preparation method of a cerium-based fluorite-type composite catalyst specifically includes the following steps:

[0041] (1) Grind 4 g of titanium dioxide and dry it to constant weight to obtain a carrier component;

[0042] (2) Dissolve cerium nitrate and silver nitrate with a mass ratio of 6:1 in deionized water to obtain a nitrate solution;

[0043] (3) Add the carrier component to the nitrate solution, stir it using a magnetic stirrer, add 60 mmol of urea during the stirring process, mix evenly, ultrasonically disperse the obtained suspension for 30 min, then transfer it to a reaction kettle, raise the temperature to 120 °C in a forced-air drying oven and react for 18 h. After the reaction is completed, cool it to room temperature, separate the precipitate by a high-speed centrifuge, wash it 3 times with pure water, then put it into a forced-air drying oven and dry it at 110 °C for 24 h. Grind the obtained catalyst precursor and put it into a muffle furnace, raise the temperature to 500 °C at a rate of 1 °C / min and calcine for 2 h. After completion, naturally cool it to room temperature, and sieve the obtained powder through a 40-60 mesh sieve to obtain the cerium-based fluorite-type composite catalyst.

[0044] Example 3

[0045] A preparation method of a cerium-based fluorite-type composite catalyst specifically includes the following steps:

[0046] (1) Grind 4 g of titanium dioxide and dry it to constant weight to obtain the support component;

[0047] (2) Dissolve cerium nitrate and copper nitrate with a mass ratio of 5:1 in deionized water to obtain a nitrate solution;

[0048] (3) Add the support component to the nitrate solution, stir it using a magnetic stirrer, add 60 mmol of urea during the stirring process, mix evenly, ultrasonically disperse the obtained suspension for 30 min, then transfer it to a reaction kettle, raise the temperature to 120 °C in a blast drying oven and react for 18 h. After the reaction is completed, cool it to room temperature, separate the precipitate by a high-speed centrifuge, wash it 3 times with pure water, then put it into a blast drying oven and dry it at 110 °C for 24 h. Grind the obtained catalyst precursor and put it into a muffle furnace, raise the temperature to 500 °C at a rate of 1 °C / min and calcine for 2 h. After completion, naturally cool it to room temperature, and sieve the obtained powder through a 40-60 mesh sieve to obtain the cerium-based fluorite-type composite catalyst.

[0049] Example 4

[0050] A preparation method of a cerium-based fluorite-type composite catalyst specifically includes the following steps:

[0051] (1) Grind 4 g of alumina and dry it to constant weight to obtain the support component;

[0052] (2) Dissolve cerium nitrate and silver nitrate with a mass ratio of 5:1 in deionized water to obtain a nitrate solution;

[0053] (3) Add the support component to the nitrate solution, stir it using a magnetic stirrer, add 60 mmol of urea during the stirring process, mix evenly, ultrasonically disperse the obtained suspension for 30 min, then transfer it to a reaction kettle, raise the temperature to 120 °C in a blast drying oven and react for 18 h. After the reaction is completed, cool it to room temperature, separate the precipitate by a high-speed centrifuge, wash it 3 - 5 times with pure water, then put it into a blast drying oven and dry it at 110 °C for 24 h. Grind the obtained catalyst precursor and put it into a muffle furnace, raise the temperature to 500 °C at a rate of 1 °C / min and calcine for 2 h. After completion, naturally cool it to room temperature, and sieve the obtained powder through a 40-60 mesh sieve to obtain the cerium-based fluorite-type composite catalyst.

[0054] Example 5

[0055] A preparation method of a cerium-based fluorite-type composite catalyst specifically includes the following steps:

[0056] (1) Grind 4 g of alumina and dry it to constant weight to obtain the support component;

[0057] (2) Dissolve cerium nitrate and copper nitrate with a mass ratio of 5:1 in deionized water to obtain a nitrate solution;

[0058] (3) Add the carrier component to the nitrate solution, stir using a magnetic stirrer, add 60 mmol of urea during the stirring process, mix evenly, ultrasonically disperse the resulting suspension for 30 min, then transfer it to a reaction kettle, raise the temperature to 120 °C in a forced-air drying oven and react for 18 h. After the reaction is completed, cool it to room temperature, separate the precipitate by a high-speed centrifuge, wash it 3 - 5 times with pure water, then place it in a forced-air drying oven and dry it at 110 °C for 24 h. Grind the obtained catalyst precursor and put it into a muffle furnace, raise the temperature to 500 °C at a rate of 1 °C / min and calcine for 2 h. After completion, naturally cool it to room temperature. Sieve the obtained powder through a 40 - 60 mesh sieve to obtain the cerium-based fluorite-type composite catalyst.

[0059] Example 6

[0060] A preparation method of a cerium-based fluorite-type composite catalyst specifically includes the following steps:

[0061] (1) Grind 4 g of silicon dioxide and dry it to a constant weight to obtain the carrier component;

[0062] (2) Dissolve cerium nitrate and silver nitrate with a mass ratio of 5:1 in deionized water to obtain a nitrate solution;

[0063] (3) Add the carrier component to the nitrate solution, stir using a magnetic stirrer, add 60 mmol of urea during the stirring process, mix evenly, ultrasonically disperse the resulting suspension for 30 min, then transfer it to a reaction kettle, raise the temperature to 120 °C in a forced-air drying oven and react for 18 h. After the reaction is completed, cool it to room temperature, separate the precipitate by a high-speed centrifuge, wash it 3 - 5 times with pure water, then place it in a forced-air drying oven and dry it at 110 °C for 24 h. Grind the obtained catalyst precursor and put it into a muffle furnace, raise the temperature to 500 °C at a rate of 1 °C / min and calcine for 2 h. After completion, naturally cool it to room temperature. Sieve the obtained powder through a 40 - 60 mesh sieve to obtain the cerium-based fluorite-type composite catalyst.

[0064] Example 7

[0065] A preparation method of a cerium-based fluorite-type composite catalyst specifically includes the following steps:

[0066] (1) Grind 4 g of silicon dioxide and dry it to a constant weight to obtain the carrier component;

[0067] (2) Dissolve cerium nitrate and iron nitrate with a mass ratio of 5:1 in deionized water to obtain a nitrate solution;

[0068] (3) Add the carrier component to the nitrate solution, stir it using a magnetic stirrer, add 60 mmol of urea during the stirring process, mix evenly, transfer the obtained suspension into a reaction kettle after ultrasonic dispersion for 30 min, heat it to 120 °C in a forced-air drying oven for reaction for 18 h, cool it to room temperature after the reaction is completed, separate the precipitate by a high-speed centrifuge, wash it with pure water 3 - 5 times, then put it into a forced-air drying oven and dry it at 110 °C for 24 h. Grind the obtained catalyst precursor and put it into a muffle furnace, heat it to 500 °C at a rate of 1 - 5 °C / min for calcination for 2 h, and then naturally cool it to room temperature after completion. Sieve the obtained powder through a 40 - 60 mesh sieve to obtain the cerium-based fluorite-type composite catalyst.

[0069] Performance test

[0070] 1. Catalyst activity evaluation

[0071] Put the cerium-based fluorite-type composite catalysts prepared in Examples 1 - 7 into the catalyst activity evaluation device. The flue gas consists of 10000 ppm CO, 5% O 2 , 50 ppm SO 2 and N 2 in a balanced composition, with a flue gas flow rate of 400 mL / min. Test its CO conversion rate and SO 2 conversion rate.

[0072] The results are shown in Table 1.

[0073] Table 1 CO conversion rate and SO 2 conversion rate of the cerium-based fluorite-type composite catalysts in Examples 1 - 7

[0074] Cerium-based fluorite-type composite catalyst Complete oxidation temperature point of CO / °C <![CDATA[SO 2 Conversion rate / %]]> Example 1 180 45.5 Example 2 120 39.8 Example 3 140 42.1 Example 4 150 33.2 Example 5 145 30.3 Example 6 180 38.6 Example 7 160 32.8

[0075] As can be seen from Table 1, the cerium-based fluorite-type composite catalysts in Examples 1 - 7 significantly reduce the oxidation temperature point of CO, achieve complete oxidation of low-temperature CO, and reduce the emission of CO in the sintering flue gas; at the same time, they also significantly improve the SO 2 conversion rate, further reduce the SO 2 concentration in the flue gas, and reduce the impact of SO 2 on the subsequent SCR denitration system.

[0076] 2. CO emission reduction, calorific value utilization, and SO 2 reduction test before the sintering flue gas denitration system

[0077] A CO catalytic reaction device and a sulfur capture device are added before the hot blast stove process in front of the sintering flue gas denitration system. Among them, the CO catalytic reaction device is equipped with the cerium-based fluorite-type composite catalyst prepared in Example 2. The sintering flue gas passes through the electrostatic precipitator, the wet limestone-gypsum desulfurization system, GGH heat exchanger 1, the CO catalytic reaction device, the sulfur capture device, GGH heat exchanger 2, and the external heating furnace in sequence, and is heated to the temperature required for medium and high temperature denitration in SCR and then enters the SCR method denitration reaction tower for denitration treatment.

[0078] Set the sintering flue gas volume Q to 800,000 m 3 / h, the CO content in the flue gas is 10,000 mg / m 3 , and the combustion heat (molar calorific value) of carbon monoxide is about 283 kJ / mol. After the sintering flue gas is dust-removed by the electrostatic precipitator and desulfurized by the wet limestone-gypsum method, the flue gas temperature is 50 °C, and the SO 2 content is 50 mg / m 3 . After being heated to 100 °C by GGH heat exchanger 1, it enters the CO catalytic reaction device. Assume that the temperature of the SCR method denitration reaction tower is 300 °C, the specific heat capacity of the flue gas Cp = 1.1 kJ / (m 3 ·°C), the efficiency of GGH heat exchanger 1 and GGH heat exchanger 2 is 100%, and the calorific value of blast furnace gas H = 3500 kJ / m 3 .

[0079] The energy change ΔE required for flue gas heating = 1.1×(300 - 100) = 220 kJ / m 3 ;

[0080] The required blast furnace gas volume V 1 =(Q×ΔE) / H = 50285.71 m 3 / h;

[0081] The mass M of CO 1 = 800000×10000 / 106 = 8000 kg;

[0082] The conversion rate of the catalyst to SO 2 is 40%, and the SO 2 content = 50×(1 - 40%) = 30 mg / m 3 ;

[0083] The oxidation efficiency of the catalyst to CO reaches more than 80%, and 80% is taken.

[0084] The heat released by catalytic oxidation of CO W = 8000×80%×1000 / 28×283 = 64685.7 MkJ / h;

[0085] Equivalent to blast furnace gas V 2= 64685.7 × 1000 / 3500 = 18481.6 m 3 。

[0086] Then about M blast furnace gas can be saved in one year 2 = 18481.6 × 24 × 365 = 1.6 × 10 8 m 3 ;

[0087] The flue gas temperature can be increased by about T = 64685.7 × 1000 / (1.1 × 800000) = 73.51 °C.

[0088] In summary, the desulfurized sintering flue gas enters the CO catalytic reaction device after being preheated by the GGH heat exchanger, oxidizes most of the CO in the sintering flue gas, and releases a large amount of heat, causing the temperature of the sintering flue gas to rise by about 73 °C, greatly reducing the use of blast furnace gas in industry.

[0089] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a cerium-based fluorite-type composite catalyst, characterized in that: The specific steps include: (1) grinding the metal oxide support and drying to constant weight to obtain a support component; (2) dissolving cerium nitrate and metal nitrate in water to obtain a nitrate solution; (3) adding the carrier component to the nitrate solution, stirring, adding urea, uniformly mixing, ultrasonically dispersing, heating to react, cooling to room temperature, centrifuging, washing, drying, grinding, calcining, cooling to room temperature, and sieving to obtain the cerium-based fluorite composite catalyst.

2. The method for preparing a cerium-based fluorite-type composite catalyst according to claim 1, characterized in that: In step (1), the metal oxide carrier is at least one of titanium dioxide, silicon dioxide, cobalt trioxide and aluminum oxide.

3. The method for preparing a cerium-based fluorite-type composite catalyst according to claim 1, characterized in that: In step (2), the metal nitrate is at least one of ferric nitrate, cobalt nitrate, copper nitrate, nickel nitrate, manganese nitrate and silver nitrate.

4. The method for preparing a cerium-based fluorite-type composite catalyst according to claim 1, characterized in that: In step (2), the mass ratio of the cerium nitrate to the metal nitrate is (5-10):1; the mass of the cerium nitrate is 40%-60% of the mass of the metal oxide support; and the usage ratio of the metal oxide support to urea is (2-8) g:(20-80) mmol.

5. The method for preparing a cerium-based fluorite-type composite catalyst according to claim 1, characterized in that: In step (3), the ultrasonic dispersion time is 30-60 minutes; the temperature of the temperature-raising reaction is 70-150° C., and the time is 6-18 hours.

6. The method for preparing a cerium-based fluorite-type composite catalyst according to claim 1, characterized in that: In step (3), the heating rate of the calcination is 1-5°C / min, the temperature is 300-700°C, and the time is 1-8h; the temperature of the drying is 110-130°C, and the time is 16-24h; the mesh size of the sieving is 40-60 mesh.

7. A cerium-based fluorite-type composite catalyst prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the cerium-based fluorite composite catalyst prepared by the preparation method according to any one of claims 1 to 6 in treating sintering flue gas.

9. A method for reducing CO emissions and utilizing calorific value and reducing SO2 before a sintering flue gas denitrification system, characterized in that: Specifically, the method comprises the following steps: adding a CO catalytic reaction device and a sulfur capture device before the hot blast furnace process before the sintering flue gas denitrification system, wherein the CO catalytic reaction device is provided with a cerium-based fluorite-type composite catalyst prepared by the preparation method according to any one of claims 1 to 6, and the sintering flue gas passes through a dust collector, a desulfurization system, a flue gas reheater 1, a CO catalytic reaction device, a sulfur capture device, a flue gas reheater 2, and a hot blast furnace in sequence, and is heated to the temperature required for SCR medium and high temperature denitrification, and then enters a denitrification reaction tower for denitrification treatment.

10. The method for reducing CO emissions, utilizing calorific value and reducing SO2 before the sintering flue gas denitration system according to claim 9, characterized in that: The dust collector is an electrostatic precipitator; the desulfurization system adopts wet limestone-gypsum desulfurization; the flue gas reheater 1 and the flue gas reheater 2 are rotary flue gas reheaters; the hot blast furnace is an external heating furnace; and the denitrification reaction tower is an SCR denitrification reaction tower.