A sintering flue gas single-stage treatment method

Abstract

This invention discloses a one-stage treatment method for sintering flue gas; the reactor used includes a heat exchanger, a hot blast furnace, and a reaction device; the heat exchanger is provided with an inlet channel and an outlet channel. The heat exchanger is used to exchange the heat of the gas passing through the outlet channel to the inlet channel. The inlet channel of the heat exchanger, the hot blast furnace, the reaction device, and the outlet channel of the heat exchanger are connected in sequence. The reaction device is equipped with a Ce-Mn-based catalyst. The temperature of the input sintering flue gas is 160℃~220℃; the volume ratio of nitrogen oxides to carbon monoxide is 1:(10~20); and the gas hourly space velocity is 50000h. ‑1 ~60000h ‑1 This invention achieves multifunctional coupling of catalytic units through a single-stage synergistic catalysis process, completing the removal of CO and nitrogen oxides (NOx) from sintering flue gas in the same reactor. x The treatment of sintering flue gas reduces the cost of sintering flue gas treatment.

Description

Technical Field

[0001] This invention belongs to the field of environmental catalysis technology, specifically relating to a one-stage treatment method for sintering flue gas. Background Technology

[0002] Among current CO purification technologies, catalytic oxidation is widely recognized by researchers as a highly efficient, energy-saving, and pollution-free method. However, CO-SCR (Selective Catalytic Oxidation of CO) in industrial flue gas currently faces challenges in terms of low-temperature performance. In industrial applications, increasing the flue gas temperature through heat exchangers, flue gas recirculation sintering (FGCS), or flue gas recirculation (FGR) can achieve high N2 selectivity and NO conversion rates. However, these methods require additional equipment, which exacerbates cost issues. Therefore, developing catalysts with high activity and low-temperature N2 selectivity is essential.

[0003] Sintering flue gas purification technologies mainly include activated carbon method, low-temperature oxidation-absorption, and semi-dry desulfurization + medium-low temperature SCR denitrification. Among them, "semi-dry desulfurization + medium-low temperature SCR denitrification" has gradually become the mainstream technology for sintering flue gas purification due to its advantages such as good stability and high purification efficiency. Existing medium-low temperature SCR denitrification processes use a CO catalytic unit at the front end of the process, achieving total heat transfer through two-stage series catalysis; however, this process is costly. Therefore, it is necessary to achieve a process that enables multi-pollutant synergistic catalysis to achieve cascaded heat transfer. In the new process, the hot blast stove only needs to be started at full load when the clean gas system is turned on. After the system stabilizes, the blast furnace gas consumption can be significantly reduced, and the hot blast stove can even be shut down. Compared to the two processes, the one-stage synergistic catalysis achieves multi-functional coupling of the catalytic unit, which is more in line with the development trend of "multi-pollutant synergistic control" and low-energy consumption operation.

[0004] Among numerous catalytic materials, Mn-based materials have been widely used for CO removal due to their oxygen storage capacity in the lattice and high lattice oxygen mobility. Bimetallic catalysts can further enhance the redox performance of the Mn-based material surface. The addition of Ce has great potential to change the crystal structure and valence state of MnOx; Ce substitution for Mn helps to enhance lattice oxygen activity and promote the reactivity of the CO oxidation reaction. Several methods for preparing Mn / Ce solid solutions have been proposed, such as impregnation, sol-gel, co-precipitation, hydrothermal, and ion exchange methods. Different preparation methods affect the formation of the solid solution and exhibit different catalytic oxidation performances.

[0005] Currently, many researchers focus on the catalytic performance of CO-SCR catalysts under anaerobic conditions, with limited research on CO-SCR under aerobic conditions. Therefore, developing highly efficient CO-SCR catalysts under aerobic conditions, especially those with low reduction temperatures and strong O2 resistance, is crucial for promoting its large-scale industrial application. As the core component of CO-SCR technology, the catalyst's catalytic performance directly impacts the overall denitrification efficiency of the SCR system. Investigating the metal's loading state, the properties of the support, and the interaction between the metal and the support is also extremely important for catalytic performance.

[0006] Based on past engineering practice, oxygen in flue gas significantly inhibits the CO-SCR activity of catalysts, and both noble metal and non-noble metal catalysts are greatly affected by oxygen in the flue gas. O2 competes with NO for active sites, leading to a decrease in catalytic activity. Since the presence of oxygen in industrial flue gas is unavoidable, improving the oxygen resistance of catalysts in the industrial application of CO-SCR technology is essential. Summary of the Invention

[0007] The purpose of this invention is to provide a one-stage treatment method for sintering flue gas.

[0008] This invention provides a one-stage treatment method for sintering flue gas, employing a one-stage co-processing reactor comprising a heat exchanger, a hot blast furnace, and a reaction apparatus. The heat exchanger is equipped with an inlet channel and an outlet channel. The heat exchanger is used to exchange heat from the gas passing through the outlet channel to the inlet channel. The inlet channel of the heat exchanger, the hot blast furnace, the reaction apparatus, and the outlet channel of the heat exchanger are sequentially connected. The reaction apparatus contains a Ce-Mn-based catalyst.

[0009] The one-stage treatment method for sintering flue gas includes the following steps:

[0010] Step 1: Introduce the sintering flue gas to be treated into the inlet channel of the heat exchanger; the gas volume hourly space velocity is 50,000 h⁻¹. -1 ~60000h -1 The hot blast furnace is started, heating the flue gas to 160℃~220℃ before it is introduced into the reaction device; NO in the sintering flue gas x It reacts with CO to produce CO2 and N2. The reaction releases heat, causing the temperature of the sintering flue gas to rise. The volume ratio of nitrogen oxides to carbon monoxide in the sintering flue gas reaches 1:(10–20), and the oxygen content in the sintering flue gas reaches 0.2 vol%–0.4 vol%.

[0011] Step 2: The gas output from the reaction apparatus is discharged after passing through the outlet channel of the heat exchanger. The heat exchanger absorbs the heat from the gas and transfers it to the sintering flue gas in the inlet channel. The heat exchanger heats the sintering flue gas in the inlet channel to 160℃~220℃ before the hot blast furnace is shut off. Afterward, the heat released by the CO reaction is transferred to the input gas through the heat exchanger, compensating for the inlet temperature requirements of the original reaction.

[0012] Preferably, the volume ratio of nitrogen oxides to carbon monoxide in the sintering flue gas input to the heat exchanger is 1:10.

[0013] Preferably, the temperature of the sintering flue gas input into the reaction device is 165°C, and the gas hourly space velocity is 60,000 h⁻¹. -1 .

[0014] Preferably, the Ce-Mn-based catalyst is doped with metal atoms; the metal atoms are Ni, Cu, Fe or Co.

[0015] Preferably, the metal atoms doped on the Ce-Mn-based catalyst are Ni.

[0016] Preferably, the preparation process of the Ce-Mn-based catalyst is as follows:

[0017] Step (1): Preparation of CeO2 support

[0018] Step (2): Impregnate CeO2 support (0.5g-1g) in an aqueous solution of Mn(NO3)3·4H2O (0.5-1.0mol / L) and a precursor solution of dopant M (0.01mol / L-0.05mol / L); stir the impregnated solution until dry and then calcine to obtain Mn / Ce catalyst doped with dopant M.

[0019] As a preferred embodiment, the process of preparing CeO2 support in step (1) is as follows: NaOH solution is added to Ce(NO3)3 solution until the pH value of the mixture is 9; the mixture is stirred to make a precipitate appear in the solution, and the precipitate is washed with deionized water until the pH value of the precipitate is lower than 7.5; the precipitate is dried and then calcined to obtain CeO2 support.

[0020] Preferably, in step (1), the concentration of the NaOH solution is 1 mol / L, and the stirring time is 90 min.

[0021] Preferably, in step (1), the precipitate is dried using a vacuum drying oven at a temperature of 80°C.

[0022] Preferably, in step (1), the calcination temperature is 250°C and the calcination time is 4 hours.

[0023] Preferably, in step (2), the precursor solution of dopant M is one of the aqueous solutions of Co(NO3)2.6H2O, Ni(NO3)2.6H2O, Cu(NO3)2.3H2O, and Fe(NO3)3.9H2O.

[0024] Preferably, in step (2), the stirring temperature is 60℃~80℃; the calcination temperature is 350℃-450℃; and the calcination time is 3-4 hours.

[0025] Preferably, in step (2), the mass percentage of manganese in the obtained Mn / Ce catalyst is 5%, and the mass percentage of the loading of dopant M is 10%.

[0026] The beneficial effects of this invention are:

[0027] 1. This invention achieves multifunctional coupling of catalytic units through a single-stage synergistic catalysis, completing the removal of CO and nitrogen oxides (NOx) from sintering flue gas in the same reactor. x The treatment of sintering flue gas reduces the cost of sintering flue gas treatment.

[0028] 2. This invention realizes the cascade transfer of heat energy. The hot air furnace only needs to provide heat at the beginning of the reaction. After the system stabilizes, the hot air furnace can be shut down, saving costs and conforming to the development trend of "multi-pollution synergistic control" and low-energy operation.

[0029] 3. This invention provides a method for preparing Ce-Mn-based catalysts, constructing a mixed catalytic reaction system with Mn / Ce multi-element active centers for medium- and low-temperature CO-SCR and oxidation / reduction dual sites, providing a reliable, stable, and efficient catalyst for the synergistic control and treatment of NO and CO in flue gas. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the Ce-Mn-based catalyst performance testing device used in Example 1 of the present invention.

[0031] Figure 2 This is a schematic diagram of the structure of the single-stage co-processing reactor used in Embodiment 2 of the present invention.

[0032] Figure 3 The graph shows the effect of changes in O2 content in flue gas on the NO conversion rate of the M-Mn / Ce catalyst prepared in Example 1.

[0033] Figure 4 For M-Mn / Ce catalyst at NO:CO = 1:6 and WHSV = 60000h -1 The following is a performance index graph; where (A) is NO conversion rate, (B) is CO conversion rate, and (C) is N2 selectivity.

[0034] Figure 5 For M-Mn / Ce catalyst at NO:CO = 1:10 and WHSV = 60000h -1 The following is a performance index graph; where (A) is NO conversion rate, (B) is CO conversion rate, and (C) is N2 selectivity. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings.

[0036] Example 1

[0037] A method for preparing a Ce-Mn-based catalyst is as follows:

[0038] Step 1: Preparation of CeO2 support by precipitation method

[0039] Ce(NO3)3·6H2O was selected as the precursor and dissolved in deionized water by stirring for 1-2 hours to obtain a Ce(NO3)3 solution. NaOH solution was added to the Ce(NO3)3 solution until the pH of the resulting mixture reached 9. The mixture was stirred until a precipitate formed. The precipitate was washed with deionized water until its pH was below 7.5. The precipitate was dried overnight in a vacuum drying oven and then calcined in air.

[0040] In this embodiment, the concentration of NaOH solution was 1 mol / L, the stirring time was 90 min, the temperature in the drying oven was 80℃, the calcination temperature was 250℃, and the calcination time was 4 hours.

[0041] Step 2: Preparation of M-Mn / Ce catalyst by impregnation method

[0042] Aqueous solutions of the metal precursors Mn(NO3)3·4H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Cu(NO3)2·3H2O, and Fe(NO3)3·9H2O were impregnated onto a CeO2 support. The solutions were stirred at 60-80℃ until dry, and then calcined in air at 350-450℃ for 3-4 h to obtain catalysts Ni-Mn / Ce, Cu-Mn / Ce, Fe-Mn / Ce, and Co-Mn / Ce, respectively.

[0043] In this embodiment, the CeO2 support was 6.5 g, the stirring temperature was 70 °C, the calcination temperature was 450 °C, and the calcination time was 4 h. The loading of manganese dopant was fixed at 5% by weight, and the loading of M was fixed at 10% by weight, with the loaded metal forming a monolayer coating.

[0044] Example 2

[0045] like Figure 2As shown, a one-stage treatment method for sintering flue gas is implemented using the catalyst described in Example 1 in conjunction with a one-stage co-process reactor. This one-stage co-process reactor includes a heat exchanger 8, a hot blast furnace 9, and a reaction device 10. The heat exchanger 8 is provided with an inlet channel and an outlet channel. The heat exchanger 8 is used to exchange the heat of the gas passing through the outlet channel to the inlet channel, thereby absorbing the thermal energy of the gas after the reaction to provide thermal energy for denitrification. The inlet channel of the heat exchanger 8, the hot blast furnace 9, the reaction device 10, and the outlet channel of the heat exchanger (8) are connected sequentially. The reaction device 10 is equipped with a Ce-Mn-based catalyst for treating CO and NO in the flue gas. x The coordinated reaction proceeds. Hot blast stove 9 is used to provide heat energy at the start of the reaction.

[0046] The specific process for synergistic control of CO and NO using the Ce-Mn-based catalyst described in Example 1 is as follows:

[0047] The Ce-Mn-based catalyst from Example 1 was added to the reactor 10 of the one-stage co-process reactor, and flue gas at 90°C was continuously introduced into the reactor. The hot blast furnace 9 was started to heat the flue gas, raising its temperature to 180°C upon entering the reactor 10. The CO and NO in the flue gas... x The reaction can proceed in a concerted manner under the action of a Ce-Mn-based catalyst. During the concerted reaction, heat energy is released, raising the temperature of the post-reaction gas to 200°C. Heat exchanger 8 absorbs the heat energy from the post-reaction gas, lowering its temperature to 135°C. After the reaction stabilizes, the hot air furnace 9 is shut off. The heat released from the CO reaction and the heat obtained by heat exchanger 8 through heat exchange provide the heat energy for denitrification, compensating for the high-temperature conditions required by the original reaction.

[0048] Example 3

[0049] Comparison of the catalytic effects of different M-Mn / Ce catalysts prepared in Example 1 and selection of treatment parameters for the one-stage treatment process of sintering flue gas described in Example 2.

[0050] This embodiment utilizes, as Figure 1The Ce-Mn-based catalyst performance testing device shown is used to test the catalytic effect. The device includes a gas distribution system, an analysis system, and a reaction system. The gas distribution system includes four standard steel cylinders, a mixing tank 3, a mass flow meter 6, and a quartz tube fixed-bed reactor 7. The four standard steel cylinders respectively store CO, NO, N2, and O2, and are connected to the mass flow meter 6 via pressure reducing valves. The mass flow meter 6 can individually control the flow rate of different gases emitted from each cylinder. Catalytic activity tests under different operating conditions are conducted by adjusting the opening and closing of the corresponding gas paths in different cylinders and by controlling the flow rate. The reaction system includes a preheating tank 4, a heating furnace 5, and the quartz tube fixed-bed reactor 7. The heating furnace 5 is equipped with thermocouples to monitor the temperature. Quartz wool is filled at both the inlet and outlet of the quartz tube fixed-bed reactor 7 to prevent catalyst particles from clogging the gas pipeline. The analysis system includes a gas chromatograph 1 and a flue gas analyzer 2. The gas chromatograph 1 detects and records CO and CO2 in the flue gas at the reactor outlet, while the flue gas analyzer 2 detects the content of NO, NOx, CO, and O2 in the reactor outlet.

[0051] The gas distribution system uses 6mm stainless steel pipes. The quartz tube fixed bed reactor 7 has an inner diameter of 8mm, an outer diameter of 12mm, and a length of 485mm.

[0052] The testing process is as follows:

[0053] Ni-Mn / Ce, Cu-Mn / Ce, Fe-Mn / Ce, and Co-Mn / Ce catalysts with particle sizes of 40-60 mesh were selected and added to the apparatus of Example 1. N2 from a standard steel cylinder was introduced into the apparatus to purge the catalyst surface and reaction system pipelines. After half an hour, the preset CO and NO gas flow rates were turned on, and the gas concentrations were allowed to stabilize. Then, the heating system of the apparatus was turned on, and the heating furnace 5 was heated to the experimental temperature. After the temperature of the heating furnace 5 was maintained at the required temperature for 20 minutes, a performance test experiment was conducted. A flue gas analyzer 2 was used to analyze the NO and NO concentrations in the simulated flue gas at the outlet and bypass of the heating furnace 5. x Gas chromatograph 1 detects and records CO, CO2, etc.

[0054] from Figure 3It can be seen that when 0.2 vol% O2 is introduced into the feed gas, the NO conversion rate shows a decreasing trend and remains basically stable after 20 min. Specifically, the Ni-Mn / Ce conversion rate decreases by approximately 7%, the Cu-Mn / Ce conversion rate decreases by 15%, and the NO conversion rates of Fe-Mn / Ce and Co-Mn / Ce directly drop below 10%. When 0.4 vol% O2 is added, the NO conversion rate continues to decrease, with Ni-Mn / Ce and Cu-Mn / Ce conversion rates decreasing rapidly within 20 min, remaining at 45% and 15%, respectively. When the O2 concentration increases to 0.6 vol%, the NO conversion rates of the four catalysts, from highest to lowest, are Ni-Mn / Ce (30.6%), Cu-Mn / Ce (13.3%), Fe-Mn / Ce (5.4%), and Co-Mn / Ce (1.5%). The Ni-doped Mn / Ce catalyst exhibits higher antioxidant properties in the CO-SCR reaction. Even in the presence of 0.2 vol% O2, the NO conversion rate can still remain stable at over 85%.

[0055] Figure 4 For M-Mn / Ce catalysts at NO:CO = 1:6 and WHSV (gas hourly space velocity) = 60000 h⁻¹ -1 The test results of the CO catalytic reduction of NO at low temperatures are as follows. When the CO concentration increases exponentially and there is no O2 in the system, CO cannot be fully oxidized at low temperatures, resulting in low conversion efficiency. At 200℃, all four catalysts only achieve about 25% conversion. Conversely, for NO conversion, with increasing temperature, the Ni-Mn / Ce catalyst achieves a higher NO reaction temperature window than the other three catalysts, reaching 100% conversion at 160℃. The Co-Mn / Ce catalyst exhibits the worst NO low-temperature reaction rate, with only about 30% at 140℃. Overall, in... Figure 4 In (A), when the NO:CO ratio in the system is 1:6, the NO conversion rate is the highest after Ni doping.

[0056] Figure 5 For M-Mn / Ce catalyst at NO:CO = 1:10 and WHSV = 60000h -1 Test results of CO catalytic reduction of NO at 200℃. M-Mn / Ce catalysts doped with different metals (Ni, Cu, Fe, Co) all achieved complete NO conversion below 200℃. Ni-Mn / Ce exhibits excellent low-temperature CO-SCR activity, achieving a 90% conversion rate at 165℃ under NO:CO = 1:10 conditions.

Claims

1. A one-stage treatment method for sintering flue gas; characterized in that: The single-stage co-reactor includes a heat exchanger (8), a hot air furnace (9), and a reaction device (10); the heat exchanger (8) is provided with an inlet channel and an outlet channel; the heat exchanger (8) is used to exchange the heat of the gas passing through the outlet channel to the inlet channel; the inlet channel of the heat exchanger (8), the hot air furnace (9), the reaction device (10), and the outlet channel of the heat exchanger (8) are connected in sequence; the reaction device (10) is filled with a Ce-Mn based catalyst; The Ce-Mn-based catalyst is doped with metal atoms; the metal atoms doped with the Ce-Mn-based catalyst are Ni. The preparation process of the Ce-Mn-based catalyst is as follows: Step (1): Preparation of CeO2 support Step (2): The CeO2 support is impregnated with an aqueous solution of Mn(NO3)3 4H2O and a precursor solution of dopant M; the impregnated solution is stirred until dry and then calcined to obtain a Mn / Ce catalyst doped with dopant M; The one-stage treatment method for sintering flue gas includes the following steps: Step 1: Adjust the composition of the sintering flue gas to achieve a volume ratio of nitrogen oxides to carbon monoxide of 1:(10-20) and an oxygen content of 0.2 vol% to 0.4 vol%. Step 2: Introduce the sintering flue gas obtained in Step 1 into the inlet channel of the heat exchanger (8); the gas volume space velocity is 50000 h⁻¹. -1 ~60000 h -1 The hot blast furnace (9) is started, and the flue gas is heated to 160℃~220℃ and then introduced into the reaction device (10); NO in the sintering flue gas x It reacts in concert with CO; Step 3: The gas output from the reaction device (10) is discharged after passing through the outlet channel of the heat exchanger (8); the heat exchanger (8) absorbs the heat of the gas and transfers the heat to the sintering flue gas in the inlet channel; the heat exchanger (8) can heat the sintering flue gas in the inlet channel to 160℃~220℃, and then the hot blast furnace (9) is turned off.

2. A one-stage treatment method for sintering flue gas according to claim 1; characterized in that: The volume ratio of nitrogen oxides to carbon monoxide in the sintering flue gas input to the heat exchanger is 1:

10.

3. A one-stage treatment method for sintering flue gas according to claim 1; characterized in that: The temperature of the sintering flue gas input to the reactor is 165℃, and the gas hourly space velocity is 60,000 h⁻¹. -1 .

4. A one-stage treatment method for sintering flue gas according to claim 1; characterized in that: The process of preparing CeO2 support in step (1) is as follows: NaOH solution is added to Ce(NO3)3 solution until the pH value of the mixture is 9; the mixture is stirred to make a precipitate appear in the solution, and the precipitate is washed with deionized water until the pH value of the precipitate is lower than 7.5; the precipitate is dried and then calcined to obtain CeO2 support.

5. A one-stage treatment method for sintering flue gas according to claim 4; characterized in that: In step (2), the precursor solution of dopant M is one of the aqueous solutions of Co(NO3)2.6H2O, Ni(NO3)2.6H2O, Cu(NO3)2.3H2O, and Fe(NO3)3.9H2O.

6. A one-stage treatment method for sintering flue gas according to claim 4; characterized in that: In step (2), the stirring temperature is 60℃~80℃; the calcination temperature is 350℃-450℃; and the calcination time is 3-4 hours.

7. A one-stage treatment method for sintering flue gas according to claim 4; characterized in that: In step (2), the mass percentage of manganese in the obtained Mn / Ce catalyst is 5%, and the mass percentage of the loading of dopant M is 10%.

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