SCR (Selective Catalytic Reduction) denitration catalyst based on solid waste sludge doped tailings as well as preparation method and application of SCR denitration catalyst

Abstract

The invention discloses an SCR (Selective Catalytic Reduction) denitration catalyst based on solid waste sludge doped tailings as well as a preparation method and application thereof. The method comprises the following steps: (1) activating urban solid waste sludge-based biochar by adopting a ZnCl2 impregnation method, and acidifying rare earth tailings by utilizing a hydrochloric acid and citric acid mixed solution; (2) mixing the activated urban solid waste sludge-based biochar and the acidified rare earth tailings in proportion, and sequentially grinding, sieving and ball-milling to obtain a mixture; (3) putting the mixture into a high-temperature and high-pressure heating kettle for hydrothermal synthesis, and drying turbid liquid in a vacuum drying oven after the reaction is finished; and (4) roasting by using a muffle furnace, and taking out a solid substance, namely the prepared catalyst. According to the scheme, the composite SCR denitration catalyst with high catalytic activity and high selectivity is prepared by resource utilization of solid waste municipal sludge and waste rare earth tailings after mineral separation treatment, and the purpose of treating waste with waste is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical fields of air pollution prevention and control and solid waste resource utilization. Specifically, it relates to an SCR denitration catalyst based on solid waste sludge doped with tailings, a preparation method thereof, and an application thereof. Background Art

[0002] The components of urban sludge are complex, containing a large number of harmful and difficult-to-degrade pollutants such as microplastics, heavy metals, and bacteria. If not properly treated, it will seriously pollute groundwater and damage the soil environment. Among them, toxic substances such as heavy metals and pathogens will cause secondary pollution, seriously endangering human health and living environment. Therefore, how to effectively, economically and reasonably treat and dispose of urban sludge with complex components has become one of the key problems that need to be solved most in the field of environmental pollution prevention and control.

[0003] In the process of rare earth mining, the solid waste after beneficiation treatment, due to its low grade and difficult extraction, cannot be economically and effectively re-extracted and utilized. The tailings may contain toxic substances and heavy metals. A large amount of them are buried in the open spaces of the mine, accompanied by the risk of environmental pollution. If not properly treated, it will have a serious impact on the ecological environment. Therefore, under the dual-carbon background of increasingly strict environmental protection requirements, how to further explore the value of rare earth tailings and comprehensively utilize them with high value has always been one of the hot research topics in the rare earth mining field. Summary of the Invention

[0004] The purpose of the present invention is to provide an SCR denitration catalyst based on solid waste sludge doped with tailings, a preparation method thereof, and an application thereof. After the urban solid waste sludge is selected for medium-temperature pyrolysis, ZnCl 2 is used to impregnate and activate the pyrolysis carbonized solid product, sludge-based biochar, and a mixed pickling solution of hydrochloric acid and citric acid is prepared to perform surface modification on rare earth tailings containing Fe, Ca, O, and a small amount of rare earth elements. After the modified urban solid waste sludge-based biochar and rare earth tailings are dried, they are mixed in proportion and subjected to a series of methods such as high-energy ball milling, hydrothermal synthesis, and muffle furnace roasting to prepare a composite SCR denitration catalyst. It follows the principle of solid waste resource utilization, achieves the purpose of treating waste with waste, and breaks the limitations of the comprehensive and efficient utilization of solid waste sludge and tailings resources.

[0005] The purpose of the present invention can be achieved by the following technical solutions: A preparation method of an SCR denitration catalyst based on solid waste sludge doped with tailings, comprising the following steps: (1) Using the ZnCl 2 impregnation method to activate the urban solid waste sludge-based biochar, and acidifying the rare earth tailings with a mixed solution of hydrochloric acid and citric acid; (2) Mix the activated municipal solid waste sludge-based biochar and acidified rare earth tailings in proportion, and then grind, sieve, and ball mill them in sequence to obtain a mixture. (3) Place the mixture in a high-temperature and high-pressure heating autoclave for hydrothermal synthesis. After the reaction, dry the suspension in a vacuum drying oven. (4) Roast using a muffle furnace, and the solid substance taken out is the prepared catalyst.

[0006] Preferably, in step (1), the municipal solid waste sludge-based biochar is prepared by pyrolytic carbonization of solid waste sludge, and the pyrolytic carbonization temperature is 450°C to 600°C, and the time is 0.5 to 1 h.

[0007] Preferably, in step (1), the activation temperature is 450°C to 500°C, and the time is 1.5 to 2 h.

[0008] Preferably, in step (1), the molar ratio of hydrochloric acid to citric acid in the mixed solution is 1:5 to 1:10, and the stirring reaction time for preparation is 24 to 48 h.

[0009] Preferably, in step (2), the doping amount of rare earth tailings is 50% to 100% of the mass of the municipal solid waste sludge-based biochar, and the selected mesh number is 140 to 230.

[0010] Preferably, in step (2), the ball milling is carried out in a planetary ball mill, the ball milling time is 1.5 to 2 h, the ball-to-material ratio is 20:1, the rotation speed is selected as 1200 r / min, and the transmission ratio of revolution to rotation is 1:2.

[0011] Preferably, in step (3), the hydrothermal synthesis temperature is 120°C to 150°C, the time is 2 to 3 h, the drying temperature is 80°C to 120°C, and the time is 8 h to 10 h.

[0012] Preferably, in step (4), the roasting temperature is 450°C to 600°C, the time is 2 to 3 h, and the heating rate is 20°C / min to 25°C / min.

[0013] An SCR catalyst is prepared by using the preparation method of an SCR denitration catalyst based on solid waste sludge doped with tailings.

[0014] An SCR catalyst prepared by the preparation method of an SCR denitration catalyst based on solid waste sludge doped with tailings is applied to catalytic denitration.

[0015] The beneficial effects of the present invention: In the present invention, after selecting the solid waste sludge from a municipal wastewater treatment plant for medium-temperature pyrolysis, ZnCl 2The pyrolytic carbonized solid product sludge-based biochar is treated by the impregnation activation method to increase its specific surface area, and a mixed solution of hydrochloric acid and citric acid is prepared to perform surface modification on rare earth tailings containing Fe, Ca, O, and a small amount of rare earth elements, promoting the formation of iron oxides and improving the dissolution distribution of active components in rare earth tailings. After the modification treatment, the raw material municipal solid waste sludge-based biochar and rare earth tailings are dried and mixed in proportion, and then a series of methods such as high-energy ball milling, hydrothermal synthesis, and muffle furnace calcination are carried out in sequence to prepare a composite SCR denitration catalyst, which has good catalytic activity. At the same time, the solid waste municipal sludge and the waste rare earth tailings after beneficiation treatment are efficiently utilized resourcefully, achieving the purpose of treating waste with waste, and providing new ideas and scientific basis for the treatment and disposal of the solid waste municipal sludge and rare earth tailings, breaking the limitations of the multi-channel comprehensive utilization of these two types of solid waste resources. The gas introduced is NH 3 and NO in a 1:1 ratio, and O 2 is simultaneously introduced, and N 2 is used as the balance gas to carry out the NH 3 -SCR denitration performance experiment. The denitration rate of the catalyst obtained within the reaction temperature range of 300°C to 350°C reaches more than 85%. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below with reference to the accompanying drawings.

[0017] Figure 1 It is a process flow chart for preparing an SCR denitration catalyst based on solid waste sludge doped with tailings according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0019] A method for preparing an SCR denitration catalyst based on solid waste sludge doped with tailings, as Figure 1 shown, includes the following steps: (1) The pyrolysis carbonization temperature of municipal sludge is 450°C to 600°C, and the time is 0.5 to 1 h; (2) The activation temperature of ZnCl 2 is 450°C to 500°C, and the time is 1.5 to 2 h; (3) The molar ratio of hydrochloric acid and citric acid in the prepared mixed solution is 1:5 to 1:10, and the stirring reaction time for preparation is 24 to 48 h; (4) The doping amount of rare earth tailings is 50% - 100% of the municipal solid waste sludge-based biochar, and the selected mesh number is 140 - 230; (5) The high-energy ball milling time is 1.5 - 2 h, the ball-to-material ratio is 20:1, the rotation speed is selected as 1200 r / min, and the transmission ratio of revolution to rotation is 1:2; (6) The hydrothermal synthesis temperature is 120 °C - 150 °C, the time is 2 - 3 h, the drying and baking temperature is 100 °C, and the time is 8 h; (7) The muffle furnace roasting temperature is 450 °C - 600 °C, the time is 2 - 3 h, and the heating rate is 25 °C / min.

[0020] An application of an SCR denitration catalyst based on solid waste sludge doped with tailings, under the condition that the ratio of NH 3 and NO is 1:1, using O 2 and N 2 for balancing, the catalyst is used as a flue gas denitration catalyst.

[0021] The specific implementation of the above preparation method and its application is as follows: Example 1

[0022] (1) The pyrolysis carbonization temperature of urban sludge is 450 °C, and the time is 0.75 h; (2) The activation temperature of ZnCl 2 is 500 °C, and the time is 2 h; (3) The molar ratio of hydrochloric acid and citric acid in the prepared mixed solution is 1:5, and the stirring reaction time for preparation is 48 h; (4) The doping amount of rare earth tailings is 50% of the municipal solid waste sludge-based biochar, and the selected mesh number is 200; (5) The high-energy ball milling time is 2 h, the ball-to-material ratio is 20:1, the rotation speed is selected as 1200 r / min, and the transmission ratio of revolution to rotation is 1:2; (6) The hydrothermal synthesis temperature is 150 °C, the time is 2 h, the drying and baking temperature is 100 °C, and the time is 8 h; (7) The muffle furnace roasting temperature is 500 °C, the time is 2 h, and the heating rate is 25 °C / min.

[0023] The denitration experiment was carried out with the prepared catalyst: under the condition that the ratio of NH 3 and NO is 1:1, introducing O 2 , and using N 2 for balancing, the denitration rate of the obtained catalyst can reach 42% in the range of 300 °C - 350 °C. Example 2

[0024] This example provides a preparation method and an application of an SCR denitration catalyst based on solid waste sludge doped with tailings, The preparation method and its application are the same as those in Example 1, and the specific implementation is as follows: (1) The pyrolysis carbonization temperature of municipal sludge is 450 °C, and the time is 0.75 h; (2) ZnCl 2 The activation temperature is 500 °C, and the time is 2 h; (3) The molar ratio of hydrochloric acid and citric acid to prepare the mixed solution is 1:5, and the stirring reaction time for preparation is 48 h; (4) The doping amount of rare earth tailings is 60% of the municipal solid waste sludge-based biochar, and the selected mesh number is 200; (5) The high-energy ball milling time is 2 h, the ball-to-material ratio is 20:1, the rotation speed is selected as 1200 r / min, and the transmission ratio of revolution to rotation is 1:2; (6) The hydrothermal synthesis temperature is 150 °C, the time is 2 h, the drying temperature is 100 °C, and the time is 8 h; (7) The calcination temperature in the muffle furnace is 500 °C, the time is 2 h, and the heating rate is 25 °C / min.

[0025] The prepared catalyst is used for denitrification experiments: Under the condition that the ratio of NH 3 and NO is 1:1, O 2 is introduced, and N 2 is used for balancing. The denitrification rate of the obtained catalyst can reach 51% in the range of 300 °C to 350 °C. Example 3

[0026] This example provides a preparation method and application of an SCR denitrification catalyst based on solid waste sludge doped with tailings, The preparation method and its application are the same as those in Example 1, and the specific implementation is as follows: (1) The pyrolysis carbonization temperature of municipal sludge is 450 °C, and the time is 0.75 h; (2) ZnCl 2 The activation temperature is 500 °C, and the time is 2 h; (3) The molar ratio of hydrochloric acid and citric acid to prepare the mixed solution is 1:5, and the stirring reaction time for preparation is 48 h; (4) The doping amount of rare earth tailings is 80% of the municipal solid waste sludge-based biochar, and the selected mesh number is 200; (5) The high-energy ball milling time is 2 h, the ball-to-material ratio is 20:1, the rotation speed is selected as 1200 r / min, and the transmission ratio of revolution to rotation is 1:2; (6) The hydrothermal synthesis temperature is 150 °C, the time is 2 h, the drying temperature is 100 °C, and the time is 8 h; (7) The calcination temperature in the muffle furnace is 500 °C, the time is 2 h, and the heating rate is 25 °C / min.

[0027] The denitrification experiment was carried out with the prepared catalyst: Under the condition that the ratio of NH 3 to NO is 1:1, O 2 was introduced, and N 2 was used for balancing. The denitrification rate of the obtained catalyst can reach 71% in the range of 300 °C to 350 °C. Example 4

[0028] This example provides a preparation method and application of an SCR denitrification catalyst based on solid waste sludge doped with tailings. The described preparation method and application are the same as those in Example 1, and the specific implementation is as follows: (1) The pyrolysis carbonization temperature of urban sludge is 450 °C, and the time is 0.75 h; (2) The activation temperature of ZnCl 2 is 500 °C, and the time is 2 h; (3) The molar ratio of hydrochloric acid and citric acid in the prepared mixed solution is 1:5, and the stirring reaction time for preparation is 48 h; (4) The doping amount of rare earth tailings is 100% of the urban solid waste sludge-based biochar, and the selected mesh number is 200; (5) The high-energy ball milling time is 2 h, the ball-to-material ratio is 20:1, the rotation speed is selected as 1200 r / min, and the transmission ratio of revolution to rotation is 1:2; (6) The hydrothermal synthesis temperature is 150 °C, the time is 2 h, the drying and baking temperature is 100 °C, and the time is 8 h; (7) The calcination temperature in the muffle furnace is 500 °C, the time is 2 h, and the heating rate is 25 °C / min.

[0029] The denitrification experiment was carried out with the prepared catalyst: Under the condition that the ratio of NH 3 to NO is 1:1, O 2 was introduced, and N 2 was used for balancing. The denitrification rate of the obtained catalyst can reach 86% in the range of 300 °C to 350 °C.

[0030] In the technical solution of the present invention, after selecting the sludge from the urban sewage treatment plant for medium-temperature pyrolysis, the ZnCl 2 impregnation activation method is used to treat the pyrolyzed and carbonized solid product sludge-based biochar to increase its specific surface area, and a mixed solution of hydrochloric acid and citric acid is prepared to perform surface modification on the rare earth tailings containing Fe, Ca, O and a small amount of rare earth elements, promote the formation of iron-based oxides, improve the dissolution and distribution of active components in the rare earth tailings. After the modified raw material urban solid waste sludge-based biochar and rare earth tailings are dried, they are mixed in proportion and successively subjected to a series of methods such as high-energy ball milling, hydrothermal synthesis and muffle furnace calcination to prepare a composite SCR denitrification catalyst, which has good catalytic activity. The introduced gas is NH in a 1:1 ratio.3 and NO are simultaneously introduced into O 2 , N 2 is used as a balance gas to conduct the NH 3 -SCR denitration performance experiment. The denitration rate of the catalyst obtained within the reaction temperature range of 300 °C to 350 °C reaches more than 85%. In addition, the solid waste municipal sludge and the waste rare earth tailings after ore dressing treatment are efficiently utilized in a resourceful way, achieving the purpose of treating waste with waste, providing new ideas and scientific basis for the treatment and disposal of the solid waste municipal sludge and rare earth tailings, and breaking through the limitations of the multi-channel comprehensive utilization of these two types of solid waste resources.

[0031] The above specific implementation part has specifically introduced the analysis method involved in the present invention. It should be noted that the above introduction is only to help those skilled in the art better understand the method and idea of the present invention, rather than a limitation on the relevant content. Without departing from the principle of the present invention, those skilled in the art can also make appropriate adjustments or modifications to the present invention, and the above adjustments and modifications should also fall within the protection scope of the present invention.

Claims

1. A method for preparing an SCR denitration catalyst based on solid waste sludge doped with tailings, characterized in that: The steps include: (1) The municipal solid waste sludge-based biochar was activated by ZnCl2 impregnation method, and the rare earth tailings were acidified by a mixed solution of hydrochloric acid and citric acid; (2) adding the activated municipal solid waste sludge-based biochar and the acidified rare earth tailings in proportion, grinding, sieving and ball milling in sequence to obtain a mixture; (3) placing the mixture in a high-temperature and high-pressure heating kettle for hydrothermal synthesis, and drying the suspension in a vacuum drying oven after the reaction is completed; (4) Calcination in a muffle furnace to obtain the solid material, which is the prepared catalyst.

2. The method according to claim 1, characterized in that In step (1), the municipal solid waste sludge-based biochar is prepared by pyrolysis and carbonization of solid waste sludge, and the pyrolysis and carbonization temperature is 450° C. to 600° C., and the time is 0.5 to 1 h.

3. The method according to claim 1, characterized in that In step (1), the activation temperature is 450°C to 500°C, and the activation time is 1.5 to 2 hours.

4. The method according to claim 1, characterized in that: In step (1), the molar ratio of hydrochloric acid to citric acid in the mixed solution is 1:5 to 1:10, and the stirring reaction time is configured to be 24 to 48 hours.

5. The method according to claim 1, characterized in that: In step (2), the rare earth tailings are added in an amount of 50% to 100% of the mass of the municipal solid waste sludge-based biochar, and the selected mesh size is 140 to 230.

6. The method according to claim 1, characterized in that In step (2), the ball milling is carried out in a planetary ball mill, the ball milling time is 1.5 to 2 hours, the ball-to-material ratio is 20:1 to 40:1, the rotation speed is selected to be 1000 r / min to 2000 r / min, and the transmission ratio of revolution to rotation is 1:1 to 1:

3.

7. The method according to any one of claims 1 to 6, characterized in that: In step (3), the hydrothermal synthesis temperature is 120°C to 150°C, the time is 2 to 3 hours, and the drying temperature is 80°C to 120°C, the time is 8 hours to 10 hours.

8. The method according to claim 7, characterized in that In step (4), the calcination temperature is 450°C to 600°C, the time is 2 to 3 hours, and the heating rate is 20°C / min to 25°C / min.

9. An SCR catalyst, characterized in that: The method is prepared by any one of claims 1 to 8.

10. The SCR catalyst according to claim 9 is used for catalytic denitration.

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