Coal gasification coarse slag loaded iron-manganese bimetallic oxide catalyst, preparation method and application thereof

Abstract

The present application belongs to the technical field of iron-manganese bimetallic oxide, and particularly relates to a coal gasification coarse slag loaded iron-manganese bimetallic oxide catalyst, a preparation method and application thereof. The metal oxide is loaded with iron metal oxide and manganese metal oxide by the coal gasification coarse slag, and the total mass of the carrier coal gasification coarse slag is taken as the basis, the loading percentage is calculated according to MnO2 and Fe2O3, the loading mass percentage of the iron-based metal oxide on the coal gasification coarse slag is 5% to 20%, and the loading mass percentage of the manganese-based metal oxide on the coal gasification coarse slag is 1% to 7%. The obtained iron-manganese bimetallic oxide denitration catalyst is low in price, excellent in activity, strong in sulfur poisoning resistance, safe, has broad application potential, and the preparation method is simple, and simultaneously realizes the reuse of the coal gasification coarse slag.

Description

Technical Field

[0001] This invention belongs to the field of iron-manganese bimetallic oxide technology, specifically relating to an iron-manganese bimetallic oxide catalyst supported on coal gasification coarse slag, its preparation method, and its application. Background Technology

[0002] Cement, as a basic building material, has long been widely used in transportation, national defense, and people's livelihood. In the cement industry, nitrogen oxide (NOx) control has become a major challenge. The cement industry mainly uses the following methods to control NOx emissions: low-NOx combustion (burner) technology, in-furnace combustion control technology, selective non-catalytic reduction (SNCR) technology, and selective catalytic reduction (SCR) technology. The first two types of denitrification technologies belong to the first category, and their advantage lies in utilizing the performance of the kiln itself and the burner to reduce NOx emissions. x The first type of denitrification technology has drawbacks, including high fuel requirements and low denitrification efficiency. The latter two types of denitrification technologies fall into the second category. SCR (Selective Catalytic Reduction) has the highest denitrification efficiency in the cement industry, effectively reducing the amount of reducing agent (ammonia water) used and significantly reducing ammonia slip. However, due to the special characteristics of cement kiln flue gas—high dust and alkali content, and even sulfur and water vapor content—the lifespan of the catalyst is affected. Seeking efficient, inexpensive, and long-lasting SCR technology is the current research direction.

[0003] Currently, cement plants primarily use vanadium (tungsten) titanium systems for SCR catalysts, specifically TiO2 (anatase) catalysts, including V2O5 / TiO2 catalysts, V2O5-WO3 / TiO2 catalysts, and V2O5-MoO3 / TiO2 catalysts. While vanadium-based catalysts exhibit good denitrification activity, V2O5 is somewhat toxic, and sulfur can cause catalyst poisoning. Furthermore, the high cost of vanadium (tungsten) titanium system catalysts limits their large-scale application.

[0004] With the increasing maturity and widespread application of coal gasification technology, the amount of coal gasification coarse slag (CGCS) produced is also continuously rising. CGCS consists of residual carbon left after incomplete gasification and molten material derived from minerals in coal. It is a waste product, and although some reuse has been achieved, current treatment methods primarily include landfilling, co-firing, and use as a building material additive. Iron and manganese, both transition metals, are characterized by variable valence states, wide availability, low price, and high efficiency. Further research is needed on how to use them as catalysts in combination with CGCS to achieve efficient and safe denitrification. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, this invention provides a coal gasification coarse slag supported iron-manganese bimetallic oxide catalyst, its preparation method, and its application. The obtained iron-manganese bimetallic oxide denitrification catalyst is inexpensive, exhibits excellent activity, strong resistance to sulfur poisoning, and is safe, possessing broad application potential. Furthermore, the method is simple to prepare and simultaneously enables the reuse of coal gasification coarse slag.

[0006] To achieve the above objectives, on the one hand, the present invention provides a coal gasification coarse slag supported iron-manganese bimetallic oxide catalyst, wherein the metal oxide is composed of iron metal oxide and manganese metal oxide supported on coal gasification coarse slag. The total mass of the coal gasification coarse slag as the support is used, and the loading percentage is calculated based on MnO2 and Fe2O3. The mass percentage of iron-based metal oxide loading on the coal gasification coarse slag is 5%-20%, and the mass percentage of manganese-based metal oxide loading on the coal gasification coarse slag is 1%-7%.

[0007] Further improvements to this scheme include a 15% mass percentage of iron-based metal oxide loading on the coarse coal gasification slag and a 5% mass percentage of manganese-based metal oxide loading on the coarse coal gasification slag.

[0008] On the other hand, the present invention provides a method for preparing the above-mentioned coal gasification coarse slag supported iron-manganese bimetallic oxide catalyst, including the following preparation steps: (1) Firstly, the coal gasification coarse slag is dried, crushed and sieved to obtain coal gasification coarse slag particles, which serve as catalyst carriers;

[0009] (2) The coarse coal gasification slag particles obtained in step (1) are mixed with Fe(NO3)3 precursor solution and Mn(NO3)2 solution, stirred and dried, and then placed in a furnace for calcination in air atmosphere to obtain a supported iron-manganese bimetallic oxide catalyst.

[0010] In a further improvement to this scheme, the calcination temperature is 400℃-600℃, preferably 550℃.

[0011] Further improvements to this scheme include the following preparation steps:

[0012] (1) First, the coarse coal gasification slag is dried in an oven at 105℃ for 12 hours, crushed, and passed through a 40-60 mesh square hole sieve to obtain coarse coal gasification slag particles, which are used as catalyst carriers.

[0013] (2) Weigh 3.7950g of ferric nitrate nonahydrate Fe(NO3)3·9H2O solid powder and 1.029g of 50wt.% Mn(NO3)2 aqueous solution and pour them into a beaker. Add an appropriate amount of deionized water, stir, and let stand for 2h to obtain a mixed solution (the concentration of Fe(NO3)3 and Mn(NO3)2 mixed solution is not required here. The amount of deionized water added later will not affect the final performance. As long as the dissolution is complete, drying can be carried out later). Weigh 5g of the coal gasification coarse slag particles from step (1) and mix them with the mixed solution. Stir mechanically for 3h, dry in a forced-air drying oven at 80℃ for 5h, and then dry at 110℃ for 12h. Place the dried particles in a tube furnace. In the process, the temperature was raised at a rate of 10℃ / min, and the catalyst was calcined at 550℃ in air for 3 hours. After natural cooling to room temperature, the catalyst preparation was completed. Using the coal gasification slag as the total mass, and the loading percentages as MnO2 and Fe2O3, a composite supported catalyst with a mass fraction of 15% Fe-based oxide catalyst and 5% Mn-based oxide catalyst was obtained. The corresponding mass fraction of iron-manganese-based bimetallic oxide catalyst was prepared by weighing ferric nitrate nonahydrate Fe(NO3)3·9H2O and Mn(NO3)2 solution.

[0014] In addition, the present invention provides the application of iron-manganese bimetallic oxide loaded on coal gasification coarse slag in the field of denitrification, preferably, the denitrification temperature is 150℃-350℃, and more preferably 250℃.

[0015] A further improvement to this scheme is that, at a denitrification temperature of 150℃-250℃, the volumetric space velocity is 5000 h⁻¹. -1 -25000h -1 .

[0016] A further improvement to this scheme is that when the denitrification temperature is 150℃-250℃, the ammonia-nitrogen ratio is taken as 1.0-1.2.

[0017] A further improvement to this scheme is that the O2 concentration is 3% ± 1%, preferably 3%.

[0018] The beneficial effects of this invention are as follows:

[0019] (1) The catalysts obtained through bimetallic loading exhibit superior performance compared to monometallic supported catalysts. CGCS-15Fe5Mn demonstrates better performance than CGCS-15Fe and CGCS-5Mn in terms of denitrification activity, N2 selectivity, and resistance to sulfur poisoning, confirming the significant interaction between the two metals. Tests revealed that the optimal calcination temperature for CGCS-15Fe5Mn is 550℃, with an optimal denitrification temperature window of 250℃, exhibiting excellent medium- and low-temperature activity. This is because the addition of Mn increases the dispersion of the active components, and the synergistic effect of the two metals greatly enhances the medium- and low-temperature activity of the catalyst.

[0020] (2) The present invention realizes the reuse of coal gasification coarse slag. The pore structure of coal gasification coarse slag (CGCS) is well preserved, and the active components are effectively loaded onto CGCS. Moreover, the prepared CGCS-15Fe5Mn catalyst has good thermal stability and its performance will not change due to changes in thermal stability within the test temperature range.

[0021] (3) This invention is suitable for actual factory applications. It studies the effects of reaction space velocity (GHSV), oxygen concentration, ammonia-nitrogen molar ratio, etc. on CGCS-15Fe5Mn and determines the optimal conditions. The test conditions are selected based on the relevant parameters of the actual cement industry, which makes it practical.

[0022] (4) The present invention uses iron and manganese-based metal oxides, which are simple to prepare, low in cost, safe to use, and suitable for large-scale applications. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 Denitrification activity test flowchart;

[0025] Figure 2 Denitrification activity of CGCS-15Fe under different Mn loadings;

[0026] Figure 3 Denitrification efficiency of CGCS-xFe with different Fe-based oxide loadings;

[0027] Figure 4 Denitrification efficiency of CGCS-xMn with different Mn-based oxide loadings;

[0028] Figure 5 The denitrification activity of CGCS-15Fe5Mn at different calcination temperatures (a) (the five vertical bars in each group correspond to 150℃, 200℃, 250℃, 300℃, and 350℃ from left to right) and test temperatures (b) (the five vertical bars in each group correspond to 400℃, 450℃, 500℃, 550℃, and 600℃ from left to right).

[0029] Figure 6 N2 selectivity of CGCS-15Fe, CGCS-5Mn and CGCS-15Fe5Mn;

[0030] Figure 7 Stability of CGCS-15Fe5Mn (a) and resistance to SO2 poisoning (b);

[0031] Anti-poisoning test of CGCS-15Fe at different test temperatures (c); Anti-sulfur poisoning test of CGCS-5Mn at 200℃ (d);

[0032] Figure 8 XRD patterns of CGCS-15Fe with different Mn loadings;

[0033] Figure 9 XRD patterns of CGCS-15Fe5Mn at different calcination temperatures;

[0034] Figure 10 SEM images of CGCS-15Fe5Mn at different magnifications: (a)-(f) correspond to magnifications of 100x, 500x, 1000x, 2000x, 5000x and 10000x, respectively;

[0035] Figure 11 EDS spectrum of CGCS-15Fe5Mn;

[0036] Figure 12 TG curves of CGCS and CGCS-15Fe5Mn;

[0037] Figure 13 H2-TPR spectra of CGCS and catalysts;

[0038] Figure 14 The six types of hysteresis loop diagrams classified by IUPAC (a) and the isothermal adsorption curves of catalysts with different loadings (b);

[0039] Figure 15 The denitrification efficiency of CGCS-15Fe5Mn at 150℃ and 250℃ as a function of space velocity;

[0040] Figure 16 The denitrification efficiency of CGCS-15Fe5Mn at 150℃ and 250℃ varies with the ammonia-nitrogen ratio;

[0041] Figure 17 The denitrification efficiency of CGCS-15Fe5Mn at 200℃, 250℃ and 300℃ varies with oxygen concentration;

[0042] In the diagram, 1 is the NO tube, 2 is the O2 tube, 3 is the NH3 tube, 4 is the Ar tube, 5 is the SO2 tube; 6 is the proton flow meter; 7 is the gas mixing device; 8 is the quartz tube; 9 is the tubular resistance furnace; 10 is the thermocouple; 11 is the flue gas analyzer; and 12 is the temperature controller. Detailed Implementation

[0043] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0044] The process flow of the catalyst activity evaluation device is as follows: Figure 1 As shown, a continuous fixed-bed catalytic reactor was used, with NH3 as the reducing agent, to test the selective catalytic reduction performance of the prepared catalyst for NO.

[0045] After being depressurized by a pressure reducing valve, the five gases enter the gas mixing device at a set flow rate via a proton flow meter, and the catalyst is filled into a quartz tube. Quartz wool is placed on both sides of the catalyst to prevent it from being carried away by the gas flow. A temperature control device works in conjunction with the tube furnace to control the temperature. The reacted gases flow through a phosphoric acid washing bottle to remove moisture and excess NH3, and then enter a flue gas analyzer until venting is complete. The flow rates are: O2 30 ml / min, NO 25 ml / min, NH3 25 ml / min, Ar 170 ml / min, total flow rate 250 ml / min, catalyst loading 1.5 ml, and space velocity 10000 h⁻¹. -1 During the experiment, each temperature window was maintained for 20 minutes.

[0046] Denitrification efficiency (η%) and nitrogen selectivity (S) N2 These are two important indicators for evaluating the denitrification performance of catalysts.

[0047]

[0048]

[0049] In the above two formulas, η represents the NO conversion rate (%), and C NO.in and C NO，out These represent the inlet and outlet concentrations of NO (ppm) and C, respectively. NH3,in C NO2,out C N2O,out These represent the inlet concentration (ppm) of NH3, and the outlet concentrations (ppm) of NO2 and N2O, respectively. N2 Represents nitrogen selectivity (%).

[0050] All raw materials used in this invention are commercially available. Manganese nitrate is from Maclean's reagent, and ferric nitrate is from Sinopharm Chemical Reagent Co., Ltd. Both are of analytical grade. The gases used in the experiment are from Anqiu Heng'an Gas Factory.

[0051] Analysis of the main chemical composition of CGCS shows that the coarse coal gasification slag is mainly composed of SiO2, Al2O3, CaO, Fe2O3 and residual carbon. Among them, CGCS(Ⅰ) has a higher loss on ignition, which is because it has a large amount of residual carbon and a rich carbon skeleton structure, which also meets the requirements of catalyst support: porous and large specific surface area.

[0052] Table 1. Analysis of the main chemical composition of CGCS

[0053]

[0054] Example 1: Effect of different Mn loadings on CGCS-15Fe

[0055] The preparation method is as follows:

[0056] (1) First, the coarse coal gasification slag is dried in an oven at 105℃ for 12 hours, crushed, and passed through a 40-60 mesh square hole sieve to obtain coarse coal gasification slag particles, which are used as catalyst carriers.

[0057] (2) Weigh out 3.7950g of ferric nitrate nonahydrate Fe(NO3)3·9H2O solid powder and 1.029g of... 50 wt.% of Mn(NO3)2 aqueous solution was poured into a beaker, deionized water was added, the mixture was stirred and allowed to stand for 2 h to obtain a mixed solution. 5 g of the coal gasification coarse slag particles from step (1) were weighed and mixed with the mixed solution. The mixture was mechanically stirred for 3 h, dried in a forced-air drying oven at 80 °C for 5 h, and then dried at 110 °C for 12 h. The dried particles were placed in a tube furnace and calcined at 550 °C in air atmosphere for 3 h at a heating rate of 10 °C / min. After natural cooling to room temperature, the catalyst preparation was completed. Based on the total mass of the coal gasification coarse slag support, the loading percentage was calculated as MnO2 and Fe2O3 to obtain a composite supported catalyst with a mass fraction of 15% Fe-based oxide and 5% Mn-based oxide. The corresponding mass fraction of iron-manganese bimetallic oxide catalyst was prepared by weighing ferric nitrate nonahydrate Fe(NO3)3·9H2O and Mn(NO3)2 solution.

[0058] Using CGCS-15Fe as a baseline, with the Fe loading constant and the Mn loading at 1%, 3%, 5%, and 7%, the overall effect of different Mn loadings on the catalyst was explored. Figure 2The figure shows the denitrification activity of CGCS-15Fe under different Mn loadings. As can be seen from the figure, at 150℃, the denitrification efficiency varies significantly due to different loadings, ranging from 55% to 85%. At 200℃, the denitrification efficiency improves but the difference narrows, ranging from 65% to 90%. At 250℃, all catalysts exhibit the highest denitrification efficiency. Among them, CGCS-15Fe5Mn reaches the highest denitrification activity of 93.4%. Above 250℃, the denitrification efficiency shows a decreasing trend and the difference becomes smaller. With increasing loading, the denitrification efficiency shows a trend of first increasing and then decreasing. The denitrification efficiency reaches its highest when the Mn loading reaches 5%. When the Mn loading reaches 7%, the denitrification efficiency begins to decrease. (Comprehensive comparison) Figure 3 (Denitrification efficiency of CGCS-15Fe) and Figure 4 (Denitrification efficiency of CGCS-5Mn) At 150℃, the denitrification efficiency of CGCS-15Fe5Mn is higher than that of CGCS-15Fe. The optimal denitrification temperature window of the latter is around 300℃, while that of CGCS-5Mn is around 200℃. The addition of Mn effectively lowers the optimal denitrification temperature. In summary, the denitrification efficiency of CGCS-15Fe is significantly improved after loading Mn, and the catalyst exhibits higher low-temperature activity. Denitrification activity: CGCS-15Fe5Mn > CGCS-5Mn > CGCS-15Fe.

[0059] Example 2: Effect of different calcination temperatures on CGCS-15Fe5Mn

[0060] As shown in Example 1, catalysts with different Mn loadings exhibit different denitrification activities, with CGCS-15Fe5Mn showing the best denitrification efficiency. The preparation conditions were calcination at 550°C for 3 hours in air. To explore the effect of different calcination temperatures on the denitrification performance of CGCS-15Fe5Mn, five temperature windows (400°C, 450°C, 500°C, 550°C, and 600°C) were set for calcination, all under the same air atmosphere for 3 hours. Figure 5The denitrification efficiency of CGCS-15Fe5Mn at different calcination and testing temperatures is shown in the figure. As can be seen from the figure, the catalysts calcined at five different temperatures all exhibited good denitrification activity. Comparing the samples calcined at 450℃, 500℃, and 550℃, the denitrification efficiency was not significantly different, indicating a wider denitrification range. However, the CGCS-15Fe5Mn calcined at 550℃ showed the best denitrification efficiency. The results indicate that 550℃ is the optimal calcination temperature for CGCS-15Fe5Mn. When testing CGCS-15Fe5Mn at different temperatures, it was found that its activity increased with increasing temperature up to 250℃, and then decreased thereafter; this trend was followed for all five calcination temperatures. The order of highest activity at these temperatures was: CGCS-5Mn > CGCS-15Fe5Mn > CGCS-15Fe. The addition of Mn effectively lowered the denitrification temperature of CGCS-15Fe, improved its low-temperature activity, broadened its denitrification temperature range, and also prevented further NO production from NH3 oxidation at high temperatures.

[0061] Example 3: N2 selectivity of CGCS-15Fe5Mn

[0062] N2 selectivity is a crucial indicator for evaluating denitrification catalysts, playing a vital role in their design and application. Comparing unsupported iron-based and manganese-based catalysts, it's evident that the N2 selectivity of unsupported iron-based catalysts is lower than that of unsupported manganese-based catalysts. This is primarily due to the irregular surface structure or structural defects in the latter, resulting in a greater variety of defect sites. After single-metal loading with CGCS, the N2 selectivity of iron-based catalysts significantly improves, while that of manganese-based catalysts shows a decreasing trend.

[0063] Figure 6 The N2 selectivity of CGCS-15Fe, CGCS-5Mn, and CGCS-15Fe5Mn was evaluated, primarily by comparing the N2 selectivity under single-metal and bimetallic loading. As shown in the figure, within the temperature range of 150℃-250℃, the N2 selectivity of CGCS-15Fe5Mn remained almost constant, indicating a wide temperature window and good low-temperature N2 selectivity. The N2 selectivity of CGCS-5Mn generally showed a decreasing trend, while that of CGCS-15Fe showed an increasing trend. In summary, the overall N2 selectivity ranking is as follows: CGCS-15Fe5M > CGCS-5M > CGCS-15Fe. Example 4: Catalyst Cyclic Stability and Sulfur Poisoning Resistance Tests.

[0064] As shown above, the CGCS-15Fe5Mn catalyst exhibits excellent denitrification activity and N2 selectivity. However, from a practical application perspective, is it worthwhile to reuse it? If applied in the cement industry, powdered catalysts can only be injected into process pipelines or enter the kiln system along with raw materials and fuels; therefore, reusability becomes a crucial cost control indicator. Three cyclic stability tests were conducted on CGCS-15Fe5Mn, each lasting 60 minutes at a chamber temperature of 250℃. Figure 7 (a) It can be seen that after three cycles of testing for a total of 3 hours, the denitrification efficiency was basically stable in the first two cycles, at around 93%, and slightly decreased in the third cycle. The overall cycle stability was good, and it can be reused.

[0065] Considering that cement kiln flue gas contains varying concentrations of SO2, and that sulfides mainly originate from raw materials, fuels, or solid (liquid) waste (co-processed in cement kilns), any SO2 released from the low-temperature zone that is not ultimately eliminated will be released into the atmosphere. Therefore, the catalyst for cement kilns must be designed to withstand sulfur poisoning. Figure 7 (b) shows the SO2 poisoning experiment of CGCS-15Fe5Mn, with an SO2 gas concentration of 500 ppm. However, at 250℃, the denitrification efficiency dropped from 93% to a minimum of approximately 45%, a reduction of half. After stopping the SO2 supply, its denitrification activity recovered somewhat, increasing by about 10%, and slightly improved over time, but did not return to its initial state. When the test temperature was 300℃, the denitrification activity decreased over time, but the decrease was relatively small, from about 90% to about 60%, and the decrease was slightly slower. After stopping the SO2 supply, its denitrification activity recovered to about 75% over time. Figures c and d show that within the optimal denitrification temperature window, the sulfur poisoning resistance time of CGCS-15Fe5Mn is significantly improved compared to CGCS-15Fe and CGCS-5Mn.

[0066] Example 5: Characterization Results and Analysis of the Catalyst

[0067] (1) XRD analysis of CGCS-15FexMn

[0068] To investigate the effect of Mn addition on the catalyst phase composition, phase analysis was performed on four catalysts with different Mn loadings. Figure 8It is known that when the Mn loading is less than 5%, almost no related diffraction peaks of the metal oxides are observed; when the Mn loading is 7%, the denitrification efficiency decreases, mainly because various active components occupy the vacancies on the CGCS surface, and even agglomerate on the CGCS surface, blocking the pores, covering and reducing the number of active sites, thus reducing the denitrification activity. Therefore, within a certain range, the addition of Mn can improve the denitrification activity. On the one hand, the addition of Mn greatly improves the dispersibility of iron-manganese oxides, thereby increasing the number of active sites. The improvement in denitrification activity by a single metal oxide is limited, while the performance of the composite catalyst is significantly improved. The active components are highly dispersed or exist in an amorphous state on the catalyst surface. The addition of Mn promotes better dispersion of Fe, and the synergistic effect makes the two metal active components highly dispersed on the support surface. The increased dispersion promotes the formation of amorphous metal oxides and also improves the low-temperature activity of the catalyst. Fe₂O₃ diffraction peaks appeared when CGCS was nearly saturated with 15% Fe, while Fe₂O₃ diffraction peaks also appeared when the Mn loading reached 7%, indicating that excessive Mn is actually detrimental to the dispersion of the active components. On the other hand, the improvement in denitrification activity is due to the formation of new species by the iron-manganese complex.

[0069] Generally, crystalline materials exhibit different crystal forms (and even amorphous states) at different temperatures, and these different crystal structures display different properties. Experiments have shown that CGCS loaded with different metals exhibits different activities, and different calcination temperatures also show differences in activity. The XRD patterns of CGCS-15Fe5Mn at different calcination temperatures are shown below. Figure 9 As shown in the figure, no obvious diffraction peaks of metal oxide crystals were found in the catalysts at the five calcination temperatures. Analysis showed that the metal oxides were distributed on the support in a highly dispersed or amorphous state, forming a mixed crystal structure of oxides such as MnO2 and Mn2O3.

[0070] (2) SEM-EDS analysis of CGCS-15Fe5Mn

[0071] CGCS has a porous structure, which determines its adsorption capacity. Whether it can maintain the integrity of the pores after being loaded with 15Fe5Mn and calcined needs further verification. Figure 10The surface morphology of CGCS loaded with 15Fe5Mn is shown. It can be observed that the surface exhibits granular and molten-like morphologies, with a largely intact pore structure. The molten state represents the original state of inorganic matter, unaffected by calcination, while the granular morphology consists of Fe and Mn metal oxides. A comparison of EDS spectra before and after loading reveals that before loading, CGCS contains elements such as Si, Al, Ca, K, Na, Ti, Mn, Cl, and C, consistent with XRF chemical analysis results. After loading, microscopic features and composition are observed. Compared to CGCS, the Fe and Mn elemental peaks on the CGCS surface are significantly enhanced, and metal oxides are abundant on the CGCS surface, indicating that both metals are loaded onto the CGCS in large quantities, which explains the improved denitrification activity.

[0072] (3) TG analysis of CGCS-15Fe5Mn

[0073] To investigate the thermal stability of CGCS and CGCS-15Fe5Mn, thermogravimetric analysis was performed on both samples under an oxygen atmosphere. The results are as follows: Figure 12 As shown in the figure, CGCS begins to lose mass at approximately 500℃, with some residual carbon beginning to oxidize, and trace amounts of inorganic matter also decomposing. Within the test temperature range (150℃-450℃), the properties of CGCS remain relatively stable.

[0074] (4) H2-TPR analysis of different catalysts

[0075] Hydrogen-programmed temperature reduction (H2-TPR) testing is used to investigate the reduction performance of catalysts, revealing the reduction characteristics of active components on the catalyst surface and measuring the reduction of the catalyst by H2 at different temperatures. It reflects the ease of reduction of oxygen species on the catalyst surface, which is crucial for evaluating catalyst activity and selectivity. It also analyzes the properties of the catalyst's active sites. Different valence states of metal oxides exhibit different reduction peaks during the reduction process. This allows for the determination of the composition and state of the active sites on the catalyst surface. Figure 13 The H2-TPR spectra of different catalysts show that CGCS and CGCS-1Fe exhibit no reduction peaks, indicating almost no reducing ability. This is partly due to the inherent physicochemical properties of CGCS, and partly because the 1% Fe loading is too low to significantly impact the overall reduction performance. CGCS-15Fe, however, shows a distinct reduction peak around 500℃, indicating that Fe is reduced to Fe2+ at this temperature. 2+ Therefore, the single short peak appearing near 500℃ should be Fe. (3+n)+ To Fe 2+deThe reduction of CGCS-15Fe5Mn differs from CGCS-15Fe in two ways: firstly, its reduction peak is stronger, and secondly, the reduction peak shifts towards lower temperatures compared to CGCS-15Fe. In summary, the addition of Mn not only increases the reduction strength of CGCS-15Fe5Mn but also enables it to exhibit reduction properties at lower temperatures.

[0076] (5) BET analysis of different catalysts

[0077] Gas adsorption is an important test method for characterizing porous solids and powders. To explore the interaction between the prepared catalyst and the adsorbent, as well as the pore size distribution of the catalyst itself, isothermal adsorption / desorption experiments were conducted on catalysts with different loadings. The results are as follows: Figure 14 As shown.

[0078] Depend on Figure 14 It can be seen that within the relative pressure range of 0 to 0.2, the adsorption capacity of the three catalysts for N2 significantly increases with the gradual increase of relative pressure, exhibiting a strong adsorption effect, indicating that the tested samples have a microporous structure. When the relative pressure continues to rise to the range of 0.2 to 0.9, the growth rate of adsorption slows down relatively, indicating that there are a certain number of mesoporous structures inside the catalyst. Compared with CGCS-15Fe and CGCS-5Mn, CGCS-15Fe5Mn has a stronger adsorption capacity at the same relative pressure, indicating that the two metal oxides are well dispersed on the surface of CGCS after simultaneous loading, and the two metals work synergistically, which is better than loading a single metal oxide. At the same time, hysteresis loops can be observed in the isotherms of all three catalysts. By comparing with the classical adsorption isotherms, this type of hysteresis loop conforms to the characteristics of the fourth type of hysteresis loop. This type of adsorbent exists in a mixed form of micropores and mesopores, and also exists in solid materials with narrow slit pores, indicating that its pore structure is irregular.

[0079] Example 6: Effect of different space velocities (GHSV) on denitrification activity

[0080] Gas hourly space velocity (GHSV) refers to the amount of gas passing through a unit volume of catalyst bed per unit time. The unit is typically the reciprocal of time, h. -1 For NH3-SCR, it is a typical gas-solid heterogeneous reaction. Different space velocities mean different contact times between the reactant gas and the catalyst. The higher the space velocity, the shorter the contact time between the gas and the catalyst, and theoretically the faster the catalyst is consumed, and vice versa. Therefore, examining the effect of space velocity on the catalyst is an important application indicator. If the catalyst still has high activity at high space velocities, it means that the amount of catalyst used can be reduced to achieve the same denitrification efficiency, effectively reducing costs.

[0081]

[0082] Where GHSV is the volumetric space velocity, Vq represents the mixed gas flow rate in ml / min, and Vc represents the catalyst volume in ml. Five space velocities were designed for testing CGCS-15Fe5Mn at 5000 h⁻¹. -1 10000h -1 15000h -1 20000h -1 and 25000h -1 To maintain the accuracy and consistency of the gas path, the space velocity was changed by altering the catalyst volume, while keeping the gas flow rate constant. This was used to observe changes in denitrification efficiency at test temperatures of 150℃ and 250℃.

[0083] The denitrification efficiency of CGCS-15Fe5Mn at 150℃ and 250℃ as a function of space velocity is as follows: Figure 15 As shown in the figure, at both test temperatures, the denitrification activity decreases with increasing space velocity, and the trend is basically the same. However, at 150℃, the denitrification efficiency decreases from a maximum of 86% to 75%; at 250℃, the denitrification efficiency decreases from a maximum of 95% to 89%, a smaller decrease than at 250℃. This is mainly because at high space velocities, the amount of gas flowing through a unit volume of catalyst per unit time increases, and the contact time between the flue gas and the catalyst is shortened, meaning a shorter reaction time, leading to a decrease in efficiency. As the temperature increases, the effect of space velocity on the catalyst decreases slightly.

[0084] Example 7: Effect of different ammonia-nitrogen ratios on denitrification activity

[0085] In this SCR denitrification reaction, NH3 is the reducing agent, and the ammonia-to-nitrogen ratio (molar ratio, NH3 / NO ratio) plays a crucial role in the entire SCR reaction. To investigate the effect of different ammonia-to-nitrogen ratios on the denitrification activity, the effects of seven ammonia-to-nitrogen ratios (0.2, 0.4, 0.6, 0.8, 1.0, 1.2, and 1.4) were tested at 150℃ and 250℃. During the tests, the total gas flow rate was kept constant at 250 ml / min, and the space velocity was 10000 h⁻¹. -1 Ar, as a balancing gas, is used to change the concentration of NH3 by adjusting the input volume of NH3 gas, thereby achieving different ammonia-nitrogen ratios.

[0086] The denitrification efficiency of CGCS-15Fe5Mn at 150℃ and 250℃ varies with the ammonia-nitrogen ratio as follows: Figure 16As shown in the figure, CGCS-15Fe5Mn exhibits similar trends at both test temperatures. Within a certain NH3 / NO range (0-1), the denitrification activity rapidly increases with the increase of the ammonia-nitrogen ratio. However, once the ammonia-nitrogen ratio reaches 1.0, the increase in denitrification activity slows down. As the ammonia-nitrogen ratio continues to increase, the denitrification efficiency tends to stabilize and hardly changes. This is mainly because NH3 forms adsorbed NH3 on the CGCS-15FeMn surface before reacting with NO. Therefore, with an increase in the amount of NH3 introduced, more NH3 is adsorbed on the catalyst surface, and the amount of NO reacting with it also increases, leading to improved denitrification efficiency. When the NH3 / NO ratio is higher than 1.0, there is too much NH3. The excess cannot be adsorbed on the catalyst surface to react with NO, resulting in limited improvement in denitrification efficiency, which tends to plateau. Further increases in the NH3 / NO ratio lead to excess NH3, causing ammonia escape and increased denitrification costs. The escaped NH3 also becomes a new pollutant in the atmosphere. In summary, to ensure denitrification efficiency and reduce ammonia escape... In practical applications, an ammonia-nitrogen ratio between 1.0 and 1.2 is more suitable.

[0087] Example 8: Effect of different oxygen concentrations on denitrification activity

[0088] Currently, the reducing agent used in the SCR denitrification process in the cement industry is NH3. Regardless of whether it is high temperature and high dust or medium temperature and medium dust, ammonia water is atomized by high-pressure compressed air and injected into the system. Under the action of a catalyst, NO reacts with NH3 in a chemical reaction, as shown in the following equation:

[0089]

[0090] Of the three equations above, the denitrification reaction is mainly represented by equation (5.2), because over 96% of the NOx produced by cement plants is NO, with a small portion being NO2. It can be seen that equation (5.2) requires a large amount of O2, indicating that O2 plays a crucial role in the SCR denitrification reaction. In the absence of O2, equation (5.3) relies on the lattice O on the catalyst surface to participate in the reaction, but the difficulty of the reaction in equation (5.3) is far greater than that in equation (5.2). The participation of O2 can greatly improve denitrification efficiency, but is a higher oxygen concentration always better? Referring to several SCR denitrification methods and their temperature ranges in cement plants, they are generally between 200℃ and 330℃ (i.e., from the C1 outlet to the raw material mill). Therefore, this section sets three temperature ranges of 200℃, 250℃, and 300℃ to examine the change in denitrification efficiency with temperature under different oxygen contents. During the test, the total gas flow rate was kept constant at 250 ml / min, the catalyst loading was constant, the carrier gas was Ar, and the NO and NH3 concentrations were 500 ppm. The concentration of O2 was controlled by adjusting the flow rate, with six operating conditions: 0%, 1%, 2%, 3%, 4%, and 5%. The results are as follows... Figure 17As shown, at 0% O2, a certain denitrification efficiency of approximately 25% is achieved at all three temperatures, indicating that the lattice oxygen on the catalyst surface participates in the reaction. With increasing O2 concentration, the denitrification efficiency rapidly increases, indicating that O2 adsorbed on the catalyst surface actively participates in the denitrification reaction. When the O2 concentration reaches 3%, the denitrification efficiency almost plateaus, and further increasing the O2 concentration has little promoting effect on the reaction; therefore, a 3% O2 ​​concentration is suitable.

[0091] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the invention should also be covered within the protection scope of the invention. Therefore, the protection scope of the invention should be determined by the scope of the claims.

Claims

1. The application of a coal gasification coarse slag supported iron-manganese bimetallic oxide catalyst in the field of denitrification, characterized in that: The metal oxide consists of iron and manganese metal oxides loaded on coal gasification coarse slag, with the total mass of the carrier coal gasification coarse slag as the total mass, and the loading percentages are calculated as MnO2 and Fe2O3. The mass percentage of iron-based metal oxide loading on the coarse coal gasification slag is 15%, and the mass percentage of manganese-based metal oxide loading on the coarse coal gasification slag is 5%. The preparation method of the catalyst includes the following preparation steps: (1) First, the coarse coal gasification slag is dried, crushed and sieved to obtain coarse coal gasification slag particles, which are used as catalyst carriers; (2) The coarse coal gasification slag particles obtained in step (1) are mixed with Fe(NO3)3 precursor solution and Mn(NO3)2 solution, stirred and dried, and then placed in a furnace and calcined in air atmosphere to obtain a supported iron-manganese bimetallic oxide catalyst; The calcination temperature is 400°C-600°C; The denitrification temperature is 150℃-250°C.

2. The application according to claim 1, characterized in that, The catalyst is prepared by the following steps: (1) First, the coarse coal gasification slag is dried in an oven at 105°C for 12 hours, crushed, and passed through a 40-60 mesh square hole sieve to obtain coarse coal gasification slag particles, which are used as catalyst carriers. (2) Weigh 3.7950 g of ferric nitrate nonahydrate Fe(NO3)3·9H2O solid powder and 1.029 g of 50wt.% Mn(NO3)2 aqueous solution and pour them into a beaker. Add deionized water, stir, and let stand for 2 h to obtain a mixed solution. Weigh 5 g of the coal gasification coarse slag particles from step (1) and mix them with the mixed solution. Stir mechanically for 3 h, dry in a forced-air drying oven at 80°C for 5 h, and then dry at 110°C for 12 h. Place the dried particles in a tube furnace, heat at a rate of 10°C / min, and calcine at 550°C in an air atmosphere for 3 h. After naturally cooling to room temperature, the catalyst preparation is complete. With the coal gasification coarse slag as the total mass, and the loading percentage calculated as MnO2 and Fe2O3, a composite supported catalyst with 15% mass fraction of Fe-based oxide and 5% mass fraction of Mn-based oxide is obtained.

3. The application according to claim 1, characterized in that: Volume hourly space velocity is 5000 h -1 -25000 h -1 .

4. The application according to claim 1, characterized in that: The ammonia-nitrogen ratio is set between 1.0 and 1.

2.

5. The application according to claim 1, characterized in that: The O2 concentration is 3% ± 1%.

Images