A denitrification catalyst for coal gasification slag, its preparation method and application

Abstract

The present invention provides a denitration catalyst for coal gasification slag and a preparation method thereof, belonging to the technical field of the preparation of denitration catalysts for coal gasification slag. The preparation method of the denitration catalyst for coal gasification slag disclosed by the present invention includes: mixing coal gasification slag with acetic acid solution to obtain a mixed system, standing and aging the mixed system and then heating and drying it to obtain a coal gasification slag acetic acid modified product; grinding and sieving the coal gasification slag acetic acid modified product to obtain a coal gasification slag acetic acid modified powder; calcining the coal gasification slag acetic acid modified powder to prepare an acetic acid modified denitration catalyst for coal gasification slag. The preparation method of the present invention is simple and easy to implement, with low cost, suitable for large-scale industrial batch production, and can realize the high-value reuse of solid waste coal gasification slag. After the acetic acid modification treatment proposed by the present invention, the denitration activity of the denitration catalyst for coal gasification slag is significantly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of denitration catalysts for coal gasification slag, and particularly relates to a denitration catalyst for coal gasification slag, a preparation method thereof and an application thereof. Background Art

[0002] NO x mainly comes from the combustion of fossil energy and solid waste, and is one of the main pollutants in the atmosphere, which will have an impact on human health. Coupled with the increasingly strict emission standards, the removal of NO x is extremely urgent. At present, the conventional choice for denitration technology is Selective Catalytic Reduction (SCR), and the NH3-SCR technology is mainly used. In the implementation process of the NH3-SCR technology, NH3 is required as a reducing agent, so there is a problem of NH3 escape. At the same time, the reaction by-product NH4HSO4 also has a safety risk of blocking pipelines. In addition, the vanadium-based catalyst used in this process is toxic and harmful to humans and the environment. Therefore, how to catalytically decompose NO x into environmentally harmless nitrogen and oxygen under ammonia-free conditions has gradually become a research hotspot in this technology.

[0003] Coal gasification, as the core technology of modern coal chemical industry, is an important part of promoting the green transformation of coal and carrying out clean and efficient utilization. As an efficient and environmentally friendly coal conversion technology, it has good development prospects in related industries. Coal gasification slag is a solid residue waste, which is formed during the coal gasification process and is a solid residue formed by various inorganic substances in coal and residual carbon during the physicochemical change process. Coal gasification slag is mainly amorphous vitreous, and its chemical composition mainly includes SiO2, Al2O3, CaO, Fe2O3, MgO and C, etc. Coal gasification slag can be recycled as a solid waste resource according to its own characteristics. However, at present, the main recycling ways of coal gasification slag are low-lying reclamation, mine filling or even direct stacking. These treatment ways not only have extremely low recycling value, but also will cause soil and groundwater pollution, and even damage the ecological environment and trigger disaster accidents. Therefore, finding a new recycling way for coal gasification slag and realizing the high-value utilization of coal gasification slag is not only beneficial to saving resources and protecting the environment, but also of great significance to the overall sustainable development of the coal industry.

[0004] Coal gasification slag contains abundant carbon, silicon and aluminum resources, with a huge output. It has a unique porous structure and good hydration activity. It is a natural porous material with adsorption and carrier functions. At present, the bulk high-value utilization of coal gasification slag mainly directly uses unmodified coal gasification slag as an adsorption material and catalyst carrier, while modified coal gasification slag is used as a catalyst. However, there are few relevant studies on preparing denitration catalysts from coal gasification slag. Chinese Patent No. CN113499778A discloses "A Denitration Catalyst for High-temperature Flue Gas in a Coal Gasification Slag Cement Kiln and Its Preparation Method", which dries the coal gasification slag and then activates it with ethanol, and the denitration rate can only be guaranteed when the temperature is higher than 850 °C. On the one hand, the use of absolute ethanol has the risk of explosion and fire, and the cost is relatively high; on the other hand, the long-term denitration stability of the denitration catalyst prepared by this process needs to be improved. Summary of the Invention

[0005] In order to overcome the defects existing in the above-mentioned prior art, the present invention provides a coal gasification slag denitration catalyst, its preparation method and application, so as to solve the technical problems that the solvent selected in the preparation process of the existing coal gasification slag denitration catalyst has the risk of explosion and fire, poor denitration efficiency and low stability during long-term use.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions to be realized:

[0007] The preparation method of the coal gasification slag denitration catalyst disclosed in the present invention uses coal gasification slag as a raw material, which is modified and activated by acetic acid, and then dried and calcined to prepare a coal gasification slag denitration catalyst with high catalytic activity for decomposing nitrogen oxides. The preparation method includes the following steps:

[0008] Step 1, mix the coal gasification slag with an acetic acid solution to obtain a mixed system, let the mixed system stand for aging treatment (so that acetic acid reacts with the coal gasification slag), and then perform heating and drying treatment to obtain a coal gasification slag acetic acid modified product;

[0009] Step 2, grind and screen the coal gasification slag acetic acid modified product obtained in Step 1 to obtain a coal gasification slag acetic acid modified powder;

[0010] Step 3, calcine the coal gasification slag acetic acid modified powder to obtain an acetic acid modified coal gasification slag denitration catalyst.

[0011] Preferably, in Step 1, the acetic acid solution is an acetic acid aqueous solution with a concentration of 0.5~3mol·L -1 .

[0012] Preferably, in Step 1, the coal gasification slag is coal gasification coarse slag or coal gasification fine slag; among them, the carbon content of the coal gasification coarse slag is 20%~25%, and the carbon content of the coal gasification fine slag is 40%~45%.

[0013] Furthermore, the gasification coarse slag is collected at the slag discharge port of the gasifier, accounting for 60% - 80% of the gasification slag; the gasification fine slag is mainly collected in the dust removal device, accounting for 20% - 40% of the gasification slag. Since the residence time of the gasification coarse slag in the gasifier is longer than that of the fine slag, and the incomplete combustion process is more thorough than that of the fine slag, generally the carbon content of the gasification coarse slag is relatively low, while the carbon content of the gasification fine slag is relatively high. Acetic acid has a certain corrosiveness to both the gasification coarse slag and the gasification fine slag. Therefore, mixing the gasification coarse slag and the gasification fine slag as raw materials for acetic acid modification can also improve their denitrification activity. Under the same conditions, the denitrification catalytic rate of the mixed gasification slag is between the denitrification catalytic rates of the gasification fine slag and the gasification coarse slag in this embodiment. Overall, the gasification slag modification method adopted in the present invention has no special requirements for the carbon content of the gasification slag, and can achieve the effect of improving the catalytic denitrification activity of the gasification slag.

[0014] Preferably, in step 1, the dosage ratio of the gasification slag to the acetic acid solution is (2 - 3) g : (3 - 4) mL.

[0015] Preferably, in step 1, the static aging time is 4 - 6 h, the heating and drying temperature is 60 - 80 °C, and the heating and drying time is 10 - 12 h.

[0016] Preferably, in step 2, the sieve mesh size used for sieving is 80 - 100 mesh.

[0017] Preferably, in step 3, the atmosphere for calcination treatment is selected as argon or nitrogen, the calcination treatment temperature is 500 - 600 °C, and the calcination treatment time is 4 - 6 h.

[0018] The present invention also provides a gasification slag denitrification catalyst, which is prepared by the aforementioned preparation method.

[0019] Furthermore, the specific surface area of the gasification slag denitrification catalyst is 234.73 - 291.47 S BET (m 2 / g), active component Fe element is precipitated on the surface of the gasification slag denitrification catalyst, and the content of the active component Fe element is 2 - 10 At%.

[0020] The present invention also provides the application of the aforementioned gasification slag denitrification catalyst in denitrification catalysis.

[0021] Specifically, the NO concentration in the thermal power plant is simulated at different temperatures, the flue gas concentration is set to 300 - 400 ppm, and under the principle of ensuring full contact between the flue gas and the gasification slag denitrification catalyst, the gasification slag denitrification catalyst is used for denitrification of the flue gas. Ar is the balance gas, and the gas flow rate is 80 - 100 mL·min -1, the space velocity is 30,000 - 50,000 h -1 , fully introduce flue gas into the fixed-bed reactor from room temperature. Starting from 50 °C, increase the temperature in steps of 50 °C to 600 °C, and keep the temperature at each step for 30 min to make the flue gas react fully and stably with the coal gasification slag denitration catalyst. Test the NO concentration in the outlet flue gas at different temperatures, calculate the denitration rate, and characterize the denitration performance of the coal gasification slag denitration catalyst. When the reaction temperature reaches 500 °C, use 1 mol·L -1 The denitration rate of the HAc-modified coal gasification slag denitration catalyst can reach 92.3%. When the reaction temperature reaches 550 °C, the denitration rate can reach 99.99%.

[0022] Compared with the existing inventions, the beneficial effects of the present invention are as follows:

[0023] For the preparation method of the coal gasification slag denitration catalyst disclosed in the present invention, on the one hand, low-concentration acetic acid is selected for activation treatment. The price of acetic acid is lower than that of absolute ethanol, it has less harm to equipment corrosion, and there is no potential safety hazard of flammability and explosion. In principle, acetic acid is used to etch the coal gasification slag, which makes a large number of pore structures generated in the glassy spherical shell of the coal gasification slag, increases the specific surface area of the coal gasification slag, enhances the adsorption capacity of the coal gasification slag, and also helps NO to contact with the active components more fully. During the acid etching process, the silicate shell structure of the coal gasification slag is dissolved, and the internal metal elements are dissolved out and fully exposed on the surface. On the other hand, after weak acid treatment, the present invention is further subjected to drying and calcination activation treatment, which can form stable ion pairs Fe 3+ / Fe 2+ etc. on the catalyst surface, which act as stable denitration active centers to carry out redox reactions with NO, are conducive to more full contact between the active sites and the reactants, and overall show a longer denitration activity, effectively reducing the reaction temperature window, thereby enhancing the denitration activity. From the experimental data results, the prepared denitration agent can maintain a denitration efficiency of not less than 90% for 12 hours during long-term reaction at 600 °C. The preparation method of the present invention is simple and easy to operate, with low cost, suitable for large-scale industrial batch production, and can realize the high-value reuse of solid waste coal gasification slag.

[0024] When the coal gasification slag denitration catalyst prepared by the present invention is applied to catalytic denitration, it can directly catalytically decompose and remove nitrogen oxides in the flue gas. From the experimental result data of the present invention, it can be seen that at 500 °C, the denitration rate of the 1 mol·L -1 HAc-modified coal gasification coarse slag denitration catalyst is 92.3%, and the denitration rate of the 3 mol·L -1 HAc-modified coal gasification coarse slag denitration catalyst is 99.9%, and the removal efficiency far exceeds that of the existing similar coal gasification slag denitration catalysts. Description of the Drawings

[0025] Figure 1 The N2 adsorption and desorption isotherm (left figure) and pore size distribution diagram (right figure) of the modified coal gasification coarse slag denitrification catalyst prepared in the present invention;

[0026] Figure 2 The relationship diagram of NO conversion rate and reaction temperature of the denitrification catalysts in Comparative Example 1 and Comparative Example 2 is shown to illustrate the denitrification activity of the unmodified coal gasification coarse slag denitrification catalyst and the unmodified coal gasification fine slag denitrification catalyst;

[0027] Figure 3 The relationship diagram of NO conversion rate and reaction temperature of the denitrification catalysts in Example 1 of the present invention and Comparative Example 1 is shown to illustrate the improvement of denitrification activity before and after acid treatment;

[0028] Figure 4 The XPS spectra before modification, after modification and after the denitrification reaction are shown to illustrate the influence of acid treatment and denitrification reaction on surface elements; among them, a) is the 3 mol·L -1 HAc-modified coal gasification coarse slag; b) is the 3 mol·L -1 HAc-modified coal gasification coarse slag after the denitrification reaction; c) is the unmodified coal gasification coarse slag;

[0029] Figure 5 The relationship diagram of NO conversion rate and reaction temperature of the modified coal gasification coarse slag denitrification catalysts in Example 1, Example 2, Example 3 and Example 4 of the present invention is shown to illustrate the influence of different acid treatment concentrations on the improvement of denitrification activity;

[0030] Figure 6 The relationship diagram of the catalytic NO conversion rate and reaction temperature of the coal gasification slag denitrification catalysts in Example 1 and Example 5 is shown to illustrate the influence of different carbon content raw materials after acid treatment on the improvement of denitrification activity.

[0031] Figure 7 The relationship diagram of NO conversion rate and reaction time of Example 4 during long-term reaction at 500 °C is shown to illustrate the stability of the coal gasification slag denitrification catalyst of the present invention during long-term denitrification reaction. Detailed implementation manners

[0032] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0033] It should be noted that the terms "first", "second", etc. in the description, claims and the above-mentioned drawings of the present invention are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0034] The present invention will be further described in detail below with reference to the accompanying drawings:

[0035] In this specification, when "normal temperature" and "room temperature" are used, the temperature can be 10~25 °C.

[0036] The present invention provides a gasification slag denitrification catalyst, its preparation method and application. This method uses gasification slag as a raw material, and after acetic acid modification treatment, the internal active components are exposed to generate the activity of directly catalytically decomposing NO at medium temperature, and a gasification slag denitrification catalyst, that is, an acetic acid-modified gasification slag denitrification catalyst (hereinafter referred to as HAc-modified gasification coarse / fine slag denitrification catalyst in the following examples) is prepared, wherein the carbon content is 20%~50%, the iron content is 3%~10%, and the aluminosilicate content is 30%~50%.

[0037] Specifically, the preparation method of the gasification slag denitrification catalyst disclosed in the present invention includes the following steps:

[0038] Step 1, mixing the gasification slag with an acetic acid solution to obtain a mixed system, standing and aging the mixed system and then heating and drying to obtain a gasification slag acetic acid modification product;

[0039] Step 2, grinding and sieving the gasification slag acetic acid modification product to obtain a gasification slag acetic acid modification powder;

[0040] Step 3, calcining the gasification slag acetic acid modification powder to prepare an acetic acid-modified gasification slag denitrification catalyst, that is, an HAc-modified gasification slag denitrification catalyst.

[0041] In step 1 of the present invention, the gasification slag modification process uses acid treatment (such as acetic acid, HCl, HNO3, etc.), which not only helps to increase the pore structure on the surface of the vitreous shell of the gasification slag, but also further destroys its aluminosilicate shell structure, enabling the internal active Fe to dissolve out. However, acidic substances with different pH values have different corrosiveness to the structure of the gasification slag. Excessive corrosion will cause its original structure to be damaged, resulting in the metal compounds formed after calcination being wrapped inside and unable to form fully exposed catalytic active sites.

[0042] Preferably, the present invention selects an acetic acid aqueous solution with a concentration of 0.5 - 3 mol·L -1 .

[0043] Specifically, the laboratory preparation process includes:

[0044] Step 1, weigh the gasification slag, place it in an oven to dry thoroughly, then put it into a beaker, and add an acetic acid solution with a concentration of 0.5 - 3 mol·L -1 dropwise to the gasification slag until the liquid just submerges all the gasification slag, stir to make it fully mixed to obtain a mixed system; let the mixed system stand and age for 4 - 6 h, then put it into the oven and dry at 60 - 80 °C for 10 - 12 h to obtain a gasification slag acetic acid modified product;

[0045] Preferably, in this process, it is optimal when the gasification slag is the gasification coarse slag with a low carbon content, and the concentration of the acetic acid solution is 3 mol·L -1 .

[0046] Step 2, grind and sieve the gasification slag acetic acid modified product to obtain a gasification slag acetic acid modified powder;

[0047] Step 3, put the above gasification slag acetic acid modified powder into a vacuum tube furnace, and under an argon or nitrogen atmosphere, heat it to 500 - 600 °C and calcine for 4 - 6 h, and then cool to obtain an HAc modified gasification slag denitration catalyst.

[0048] Test the above-prepared HAc modified gasification slag denitration catalyst in the denitration catalytic reaction. The specific method of the experimental operation includes:

[0049] Step 1, weigh 0.3 - 0.4 g of the HAc modified gasification slag denitration catalyst and place it in the middle part of a corundum tube with a corundum tube diameter of 100 - 1000 mm, and fix both ends of the solid powder with quartz wool.

[0050] Step 2, heat the corundum tube to 50 - 600 °C, and introduce NO gas with a concentration of 300 ppm into it, using Ar gas as the carrier gas, with a gas flow rate of 60 - 100 mL·min -1 , and connect the tail gas outlet to a flue gas analyzer.

[0051] The present invention will be further described below in conjunction with embodiments, but the present invention is not limited to the following embodiments:

[0052] Example 1

[0053] 1 mol·L -1 Preparation of 1 mol·L HAc modified coal gasification coarse slag denitrification catalyst:

[0054] Weigh 10 g of coal gasification coarse slag and put it into a beaker. Add 1 mol·L -1 acetic acid solution until the liquid surface just submerges all the solids. Set the magnetic stirrer speed at 400 rpm, stir for 40 min, let it stand at room temperature for 4 h, dry it at 70 °C for 11 h. Put the dried product into a quartz crucible, place it in a vacuum tube furnace, under the condition of 600 °C, introduce Ar, calcine for 4 h, and then cool it to room temperature in an Ar environment. The obtained solid is sieved through a 100-mesh sieve and collected, named 1 mol·L -1 HAc modified coal gasification coarse slag denitrification catalyst.

[0055] Example 2

[0056] 0.5 mol·L -1 Preparation of 0.5 mol·L HAc modified coal gasification coarse slag denitrification catalyst:

[0057] Weigh 12 g of coal gasification coarse slag and put it into a beaker. Add 0.5 mol·L -1 acetic acid solution until the liquid surface just submerges all the solids. Set the magnetic stirrer speed at 500 rpm, stir for 35 min, let it stand at room temperature for 5 h, dry it at 60 °C for 12 h. Put the dried product into a quartz crucible, place it in a vacuum tube furnace, under the condition of 600 °C, introduce N2, calcine for 4 h, and then cool it to room temperature in an N2 environment. The obtained solid is sieved through a 100-mesh sieve and collected, named 0.5 mol·L -1 HAc modified coal gasification coarse slag denitrification catalyst.

[0058] Example 3

[0059] 2 mol·L -1 Preparation of 2 mol·L HAc modified coal gasification coarse slag denitrification catalyst:

[0060] Weigh 15 g of coal gasification coarse slag and put it into a beaker. Add 2 mol·L -1Acetic acid solution was added until the liquid surface just submerged all the solids. The magnetic stirrer was set at a rotation speed of 600 rpm and stirred for 30 min. It was left standing at room temperature for 4 h and dried at 80 °C for 10 h. The dried product was placed in a quartz crucible and put into a vacuum tube furnace. Under the condition of 500 °C, Ar was introduced and calcined for 6 h. Then it was cooled to room temperature in an Ar atmosphere. The obtained solid was collected after passing through an 80-mesh sieve and named 2 mol·L -1 HAc-modified coal gasification coarse slag denitration catalyst.

[0061] Example 4

[0062] 3 mol·L -1 Preparation of 3 mol·L HAc-modified coal gasification coarse slag denitration catalyst:

[0063] Weigh 10 g of coal gasification coarse slag and put it into a beaker. Add 3 mol·L -1 acetic acid solution until the liquid surface just submerged all the solids. The magnetic stirrer was set at a rotation speed of 500 rpm and stirred for 40 min. It was left standing at room temperature for 6 h and dried at 60 °C for 12 h. The dried product was placed in a quartz crucible and put into a vacuum tube furnace. Under the condition of 600 °C, Ar was introduced and calcined for 5 h. Then it was cooled to room temperature in an Ar atmosphere. The obtained solid was collected after passing through a 100-mesh sieve and named 3 mol·L -1 HAc-modified coal gasification coarse slag denitration catalyst.

[0064] Example 5

[0065] 1 mol·L -1 Preparation of 1 mol·L HAc-modified coal gasification fine slag denitration catalyst:

[0066] Weigh 15 g of coal gasification fine slag and put it into a beaker. Add 1 mol·L -1 acetic acid solution until the liquid surface just submerged all the solids. The magnetic stirrer was set at a rotation speed of 600 rpm and stirred for 30 min. It was left standing at room temperature for 5 h and dried at 60 °C for 10 h. The dried product was placed in a quartz crucible and put into a vacuum tube furnace. Under the condition of 600 °C, N2 was introduced and calcined for 4 h. Then it was cooled to room temperature in an N2 atmosphere. The obtained solid was collected after passing through a 90-mesh sieve and named 1 mol·L -1 HAc-modified coal gasification fine slag denitration catalyst.

[0067] The following describes the comparative example of preparing unmodified coal gasification slag denitration catalyst.

[0068] Comparative Example 1

[0069] Preparation of unmodified coal gasification coarse slag denitration catalyst

[0070] Weigh 4 g of raw coal gasification slag, place it in a quartz crucible, put it into a vacuum tube furnace, under the condition of 500 °C, introduce Ar, after calcination for 5 h, cool it to room temperature in an Ar environment, and collect the obtained solid after passing through a 100-mesh sieve, named as unmodified raw coal gasification slag denitration catalyst.

[0071] Comparative Example 2

[0072] Prepare unmodified fine coal gasification slag denitration catalyst

[0073] Weigh 4 g of raw coal gasification slag, place it in a quartz crucible, put it into a vacuum tube furnace, under the condition of 500 °C, introduce N2, after calcination for 6 h, cool it to room temperature in an N2 environment, and collect the obtained solid after passing through a 100-mesh sieve, named as unmodified fine coal gasification slag denitration catalyst.

[0074] Taking the unmodified raw coal gasification slag denitration catalyst prepared in Comparative Example 1 as an example, the pore size distribution test was carried out with the acetic acid-modified raw coal gasification slag denitration catalyst prepared in the embodiment of the present invention, and the results are shown in Table 1 below:

[0075] Table 1

[0076]

[0077] It can be seen that with the increase of acetic acid concentration, the specific surface area, average pore size and pore volume of the raw coal gasification slag all increase. It shows that after the surface is etched by acetic acid, new pore structures are formed, and these pore structures are beneficial to the escape of metal substances, the formation of active sites and the adsorption of more gases.

[0078] Figure 1 For 3mol·L -1 The N2 adsorption and desorption isotherm and pore size distribution curve of the HAc-modified raw coal gasification slag denitration catalyst show that the N2 adsorption and desorption isotherm is an S-shaped curve, and there is a hysteresis loop when P / P0>0.43, belonging to the II / IV mixed adsorption isotherm, indicating that there are both macropores and mesopores in the modified coal gasification slag.

[0079] The following describes the method and results of the denitration performance test of the acetic acid-modified coal gasification slag denitration catalyst prepared in the embodiment of the present invention and the unmodified coal gasification slag denitration catalyst in the comparative example.

[0080] 1. The test conditions are as follows:

[0081] Dosage of coal gasification slag denitration catalyst: 0.3 g; particle size: 80-100 mesh; flue gas concentration: NO 300 ppm; carrier gas: Ar; gas velocity: 80mL·min -1 ; space velocity: 30000h -1 .

[0082] 2. Performance test results

[0083] The denitrification activity test results of Comparative Example 1 and Comparative Example 2 are as follows Figure 2 shown. It can be seen from Figure 2 that the denitrification activity of the unmodified coal gasification coarse slag denitrification catalyst without modification treatment is relatively low. Specifically, for the unmodified coal gasification fine slag denitrification catalyst, the denitrification rate is 21.4% at the catalytic reaction temperature of 500 °C, 31.5% at 550 °C, and 34.8% at 600 °C; for the unmodified coal gasification coarse slag denitrification catalyst, the denitrification rate is 22.9% at the catalytic reaction temperature of 500 °C, 26.5% at 550 °C, and 33.1% at 600 °C. This shows that the unmodified coal gasification slag denitrification catalyst has a certain denitrification activity, but it cannot meet the requirement of complete denitrification.

[0084] The denitrification activity test results of Example 1 and Comparative Example 1 are as follows Figure 3 shown. It can be seen from Figure 3 that the 1 mol·L -1 HAc-modified coal gasification coarse slag denitrification catalyst prepared in Example 1 of the present invention greatly improves the denitrification activity of the coal gasification coarse slag. The 1 mol·L -1 HAc-modified coal gasification coarse slag denitrification catalyst can reach a denitrification rate of 92.3% when the reaction temperature reaches 500 °C, 99.99% when the reaction temperature reaches 550 °C, and 99.99% when the temperature reaches 600 °C.

[0085] The XPS (X-ray photoelectron spectroscopy) spectra before and after modification treatment and after the denitrification reaction are as follows Figure 4 shown. XPS is a high-sensitivity ultra-trace surface element composition analysis technology. According to the area integration ratio of the XPS surface photoelectron spectrum, the content of Fe element on the surface after modification can be determined to be 2 - 10 At%.

[0086] As shown in Figure 4 a), b) and c) therein, it can be seen that after acid treatment modification, a response peak of Fe2p appears at the binding energy of 706.7 eV, which proves that Fe element appears on the surface of the denitrification catalyst after acid treatment. After the denitrification reaction, the intensity of the Fe peak weakens, which proves that Fe element can participate in the oxidation-reduction process of NO. This shows that the reason for the improvement of denitrification activity after acetic acid modification is that Fe element dissolves out on the surface and participates in the denitrification reaction.

[0087] The denitrification activity test results of Example 1, Example 2, Example 3 and Example 4 are as follows Figure 5 shown. It can be seen from Figure 5It can be seen that as the acetic acid concentration for treating the gasification slag increases, the activity of the modified gasification coarse slag denitration catalyst at 500 °C is higher than that of the 2 mol·L -1 modified gasification coarse slag denitration catalyst, and the denitration activity of the 1 mol·L -1 HAc modified gasification coarse slag denitration catalyst and the 1 mol·L -1 HAc modified gasification coarse slag denitration catalyst is significantly improved. At a reaction temperature of 500 °C, the denitration rate reaches 99.9%, indicating that high-concentration acetic acid treatment can better etch the vitreous gasification slag shell and expose the internal active components, resulting in better denitration activity at high reaction temperatures. However, excessive acetic acid concentration treatment will increase costs and equipment requirements, so it is more beneficial to use an appropriate acetic acid concentration for the reaction.

[0088] The denitration activity test results of Example 1 and Example 5 are as Figure 6 shown. It can be Figure 6 seen that when using gasification coarse slag and gasification fine slag with different carbon contents as raw materials for acid treatment, the denitration activity improvement of the gasification coarse slag with a lower carbon content after acetic acid treatment is greater than that of the gasification fine slag with a higher carbon content. At 500 °C, the denitration rate of the 1 mol·L - 1 HAc HAc modified gasification coarse slag denitration catalyst is 92.3%, while the denitration catalytic rate of the 1 mol·L -1 HAc modified gasification fine slag denitration catalyst is 57.8%, which proves that the gasification coarse slag with a lower carbon content is more conducive to the direct catalytic denitration reaction, and also indicates that the gasification slag denitration catalyst of the present invention can be prepared industrially and used as a denitration catalyst for catalytic removal of nitrogen oxides in flue gas.

[0089] The long-term reaction activity of the 3 mol·L -1 HAc modified gasification coarse slag denitration catalyst prepared in Example 4 at 500 °C is as Figure 7 shown. It can be Figure 7 seen that when the temperature is maintained at 500 °C, the denitration activity of the 3 mol·L -1 HAc modified gasification coarse slag denitration catalyst shows a relatively slow downward trend with the extension of time. At 12 h of reaction, the denitration activity of this catalyst still reaches 90%, still maintaining high-efficiency denitration, indicating its excellent stability.

[0090] In summary, the present invention utilizes the unique silicon-aluminum-based glassy spherical shell structure of coal gasification slag and the characteristic of containing some iron, and uses acetic acid with different concentrations for etching, which can generate more pore structures on the surface of coal gasification slag, expose the internal iron active components, and then generate more catalytic active centers. The denitrification catalyst of coal gasification slag modified by this method can directly catalyze the decomposition of nitrogen oxides into non-toxic nitrogen and oxygen under the reaction conditions without using ammonia as a reducing agent. This modification method is green and environmentally friendly, and the modification process is simple. It can not only transform the "solid waste" into a high-value catalyst, but also be used to treat air pollutants.

[0091] From the perspective of principle, the innovation points of the present invention are elaborated and summarized as follows: The present invention performs acid etching on the surface of coal gasification slag through acetic acid to generate more pore structures, and during the acid etching, Fe2O3 in the structure of coal gasification slag will dissolve from the inside of the glassy spherical shell to the catalyst surface to form Fe 3+ ions. Due to the weak acid corrosion of acetic acid on the structure of coal gasification slag, the specific surface area of coal gasification slag becomes larger after modification, generating more pore structures, which is beneficial to adsorb more nitrogen oxides. After calcination treatment at 500-600 °C in an argon / nitrogen environment, the residual carbon in the coal gasification slag will react with Fe 3+ to undergo a carbothermal reaction to form a stable ion pair Fe 3+ / Fe 2+ , which acts as a denitrification active center to undergo a redox reaction with NO, thereby enhancing the denitrification activity and long-term denitrification stability. The denitrification catalyst of coal gasification slag prepared by the present invention can maintain a denitrification efficiency of not less than 90% for 12 h at 500-600 °C, and has long-term denitrification stability.

[0092] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0093] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention fall within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a denitration catalyst for coal gasification slag, characterized in that, It includes the following steps: Step 1, mix the coal gasification slag with acetic acid solution to obtain a mixed system, let the mixed system stand for aging and then heat and dry it to obtain the acetic acid modified product of the coal gasification slag; the acetic acid solution is an aqueous acetic acid solution with a concentration of 0.5~3 mol·L -1 and the dosage ratio of the coal gasification slag to the acetic acid solution is (2~3) g:(3~4) mL; The coal gasification slag is the coal gasification coarse slag or the coal gasification fine slag; among them, the carbon content of the coal gasification coarse slag is 20% - 25%, and the carbon content of the coal gasification fine slag is 40% - 45%; Step 2: Grind and screen the acetic acid modified product of the coal gasification slag to obtain the acetic acid modified powder of the coal gasification slag; Step 3: Calcinate the acetic acid modified powder of the coal gasification slag to prepare the acetic acid modified coal gasification slag denitration catalyst; among them, the atmosphere for the calcination treatment is selected from argon or nitrogen, the temperature for the calcination treatment is 500 - 600 °C, and the time for the calcination treatment is 4 - 6 h.

2. The preparation method of the gasification slag denitration catalyst according to claim 1, characterized in that, In Step 1, the time for static aging is 4 - 6 h, the temperature for heating and drying is 60 - 80 °C, and the time for heating and drying is 10 - 12 h.

3. The preparation method of the gasification slag denitration catalyst according to claim 1, characterized in that, In Step 2, the mesh size of the sieve used for the screening treatment is 80 - 100 meshes.

4. The coal gasification slag denitration catalyst prepared by the preparation method of the coal gasification slag denitration catalyst according to any one of claims 1 - 3.

5. The denitrification catalyst for coal gasification slag according to claim 4, characterized in that, The denitration catalyst of the coal gasification slag has a porous structure, and the specific surface area S BET is 234.73 - 291.47 m 2 / g. The active component Fe element precipitates on the surface of the porous structure, and the atomic percentage of the active component Fe element is 2% - 10%.

6. The application of the coal gasification slag denitration catalyst according to claim 4 or 5 in catalytic denitration.

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