Municipal sludge-based charcoal-rare earth concentrate composite SCR catalyst and preparation method thereof

Abstract

The invention discloses a municipal sludge-based biochar-rare earth concentrate composite SCR (selective catalytic reduction) catalyst and a preparation method thereof, and belongs to the field of atmospheric pollution prevention and control technologies and solid waste resource utilization. According to the method, municipal sludge-based biochar and rare earth concentrate rich in Ce, La and Nd and having a synergistic effect are selected as raw materials; the SCR denitration catalyst is prepared by a series of methods such as sludge pyrolysis, high-energy ball milling, hydrothermal synthesis and microwave roasting. The rare earth concentrate has lattice distortion, active components are highly dispersed and embedded around a large number of nanoscale holes formed by the municipal sludge-based biochar, the prepared catalyst has high catalytic activity, good selectivity and environmental protection property, the catalyst is easy to prepare, convenient to operate and high in conversion rate, industrial production is facilitated, and the method is suitable for industrial production. A new thought is provided for high value-added resource utilization of the organic solid waste municipal sludge-based biochar.

Description

Technical Field

[0001] The present invention belongs to the fields of air pollution prevention and control technology and solid waste resource utilization. Specifically, it relates to a composite SCR catalyst based on urban sludge-based biochar and rare earth concentrate and a preparation method thereof. Background Technique

[0002] The annual output of urban sludge is increasing year by year, continuously aggravating the negative impact on the environment and potentially endangering human health. Among them, the pyrolysis and carbonization treatment of urban sludge can eliminate pathogens, parasites and reduce the mobility of heavy metal pollutants, and is expected to meet the requirements of harmlessness, stabilization, reduction and resource utilization of sludge at the same time. However, how to widely apply the solid product sludge-based biochar of the urban sludge pyrolysis and carbonization treatment in a high-value and multi-channel manner directly affects the market application prospect of this treatment process. Therefore, carrying out research on new ways for the efficient resource utilization of organic solid waste urban sludge-based biochar is one of the most urgent problems to be solved in the field of sludge pyrolysis and carbonization today.

[0003] Rare earth concentrate is mainly composed of bastnasite, fluocerite, monazite, etc. The valuable elements are enriched and the particle distribution ratio is high. It is easy to decompose a large amount of Ce oxides after roasting, providing support for rare earth concentrate as a catalytic material and having natural advantages. Therefore, carrying out green research and development on the utilization of high-value functional materials of rare earth minerals, making use of the mineral properties endowed by nature, giving full play to the role of co-associated rare earth elements, and developing new ways for the comprehensive and efficient utilization of mineral resources and constructing a green circular economy system have significant meanings. Summary of the Invention

[0004] The purpose of the present invention is to provide a composite SCR catalyst based on urban sludge-based biochar and rare earth concentrate and a preparation method thereof. Selecting urban sludge-based biochar with adsorption capacity in industrial production and rare earth concentrate rich in the synergistic action of multiple components such as Ce, La, and Nd as raw materials, and using a series of methods such as sludge pyrolysis, high-energy ball milling, hydrothermal synthesis and microwave roasting to prepare an SCR denitration catalyst. The prepared catalyst has high catalytic activity, good selectivity and environmental protection. It follows the principles of air environmental pollution prevention and control and solid waste resource utilization, and provides new ideas and scientific basis for the treatment and disposal of organic solid waste urban sludge-based biochar, the comprehensive and efficient utilization of rare earth mineral resources, and the design and research and development of SCR denitration catalysts.

[0005] The purpose of the present invention can be achieved by the following technical solutions: A preparation method of a composite SCR catalyst based on urban sludge-based biochar and rare earth concentrate, comprising the following steps: (1) Sludge pyrolysis: Selecting urban sludge for medium-temperature pyrolysis and carbonization treatment to prepare sludge-based biochar; (2) Grinding and sieving: The rare earth concentrate is mixed with sludge-based biochar in proportion and then ground and sieved successively to obtain a mixture. (3) High-energy ball milling: Ball mill the mixture. (4) Hydrothermal synthesis: The ball-milled mixture is placed in a high-temperature and high-pressure heating kettle for hydrothermal synthesis. After taking it out, the suspension is dried in a vacuum drying oven. (5) Shaping and calcination: Use microwave calcination, and the solid substance taken out is the prepared catalyst.

[0006] Preferably, in step (1), the medium-temperature pyrolysis carbonization temperature is 450 °C to 600 °C, and the time is 0.5 to 1 h.

[0007] Preferably, in step (2), the doping amount of the rare earth concentrate is 10% to 50% of the mass of the sludge-based biochar, and the sieving mesh number is 300 to 325.

[0008] Preferably, in step (3), 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 15:1 to 30:1, the rotation speed is selected as 500 r / min to 1500 r / min, and the transmission ratio of revolution to rotation is 1:2 to 1:3.

[0009] Preferably, in step (4), the hydrothermal synthesis temperature is 120 °C to 150 °C, and 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.

[0010] Preferably, in step (5), the calcination temperature is 350 °C to 400 °C, the time is 20 to 30 min, and the heating rate is 20 °C / min to 25 °C / min.

[0011] An SCR catalyst prepared by the method for preparing the above-mentioned urban sludge-based biochar-rare earth concentrate composite SCR catalyst.

[0012] The prepared catalyst can be applied to catalytic denitrification. Specifically, an application of the above SCR catalyst, under the condition that NH 3 and NO are 1:1, with O 2 and N 2 for balancing use, and the above SCR catalyst is used as a flue gas denitrification catalyst.

[0013] The beneficial effects of the present invention: The present invention selects urban sludge-based biochar with adsorption capacity in industrial production and rare earth concentrates rich in Ce, La, Nd and other multi-component synergistic effects as raw materials, and prepares an SCR denitration catalyst by a series of methods such as sludge pyrolysis, high-energy ball milling, hydrothermal synthesis and microwave calcination. The lattice of the rare earth concentrate is distorted, and the active components are highly dispersed and embedded around a large number of nanoscale pores formed by the urban sludge-based biochar. The prepared catalyst has high catalytic activity, good selectivity and environmental protection. The catalyst of the present invention is simple to prepare, convenient to operate and has a high conversion rate, which is beneficial to industrial production, provides a new idea for the high-value resource utilization of organic solid waste urban sludge-based biochar, and breaks the limitations of its traditional utilization methods. 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 a 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 200 °C to 250 °C reaches more than 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described below with reference to the accompanying drawings.

[0015] Figure 1 is the process flow chart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] 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 work shall fall within the protection scope of the present invention. Example 1

[0017] A composite SCR catalyst of urban sludge-based biochar-rare earth concentrate. Exemplarily, the rare earth concentrate uses Bayan Obo rare earth concentrate as the raw material. As Figure 1 shown, it includes the following steps: (1) The pyrolysis carbonization temperature of urban sludge is 450 °C to 600 °C, and the time is 0.5 to 1 h; (2) The doping amount of rare earth concentrate is 10% to 50% of the urban sludge-based biochar, and the selected mesh number is 300 to 325; (3) The high-energy ball milling time is 1.5 to 2 h, the ball-to-material ratio is 15:1, the rotation speed is selected as 1200 r / min, and the transmission ratio of revolution to rotation is 1:2; (4) The hydrothermal synthesis temperature is 120 °C to 150 °C, the time is 2 to 3 h, the drying temperature is 100 °C, and the time is 8 h; (5) The microwave calcination temperature is 350 °C to 400 °C, the time is 20 to 30 min, the heating rate is 20 °C / min, and the solid substance taken out is the prepared catalyst.

[0018] For the NO x emission of traditional coal-fired power plants, the selective catalytic reduction technology is one of the most effective means for NO x removal, and the catalyst is the core of this technology. Due to the optimal denitration temperature window of traditional vanadium-based catalysts being in the medium and high temperature range, it is difficult to apply to many industries with medium and low temperature requirements. In addition, the environmental problems of the subsequent treatment of waste vanadium-based catalysts have emerged year by year. Therefore, the research and development of non-vanadium-based low-temperature SCR catalysts remains one of the research hotspots in this field.

[0019] Therefore, in the second aspect of the embodiments of the present invention, an application of the above catalyst is provided. Under the condition that the ratio of NH 3 to NO is 1:1, with O 2 and N 2 used for balancing, the catalyst is used as a flue gas denitration catalyst.

[0020] The specific embodiment 1 of the above preparation method and its application is as follows: (1) The pyrolysis carbonization temperature of urban sludge is 450 °C, and the time is 0.75 h; (2) The doping amount of rare earth concentrate is 20% of the urban sludge-based biochar, and the selected mesh number is 300; (3) The high-energy ball milling time is 2 h, the ball-to-material ratio is 15:1, the rotation speed is selected as 1200 r / min, and the transmission ratio of revolution to rotation is 1:2; (4) The hydrothermal synthesis temperature is 130 °C, the time is 2.5 h, the drying temperature is 100 °C, and the time is 8 h; (5) The microwave calcination temperature is 400 °C, the time is 20 min, the heating rate is 20 °C / min, and the solid substance taken out is the prepared catalyst.

[0021] The denitration experiment is carried out with the prepared catalyst: Under the condition that the ratio of NH 3 to NO is 1:1, O 2 is introduced, and N 2 is used for balancing. The denitration rate of the obtained catalyst can reach 55% in the range of 200 °C to 250 °C. Example 2

[0022] This example provides a preparation method and an application of an urban sludge biochar-based SCR catalyst, The said 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 urban sludge is 450 °C, and the time is 0.75 h; (2) The doping amount of rare earth concentrate is 30% of the urban sludge-based biochar, and the selected mesh number is 300; (3) The high-energy ball milling time is 2 h, the ball-to-material ratio is 30:1, the rotation speed is selected as 500 r / min, and the transmission ratio of revolution to rotation is 1:3; (4) The hydrothermal synthesis temperature is 130 °C, the time is 2.5 h, the drying temperature is 90 °C, and the time is 10 h; (5) The microwave roasting temperature is 400 °C, the time is 20 min, the heating rate is 22 °C / min, and the solid substance taken out is the prepared catalyst.

[0023] 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 67% in the range of 200 °C to 250 °C. Example 3

[0024] This example provides a preparation method and application of an urban sludge biochar-based SCR catalyst, 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 doping amount of rare earth concentrate is 40% of the urban sludge-based biochar, and the selected mesh number is 300; (3) The high-energy ball milling time is 2 h, the ball-to-material ratio is 22:1, the rotation speed is selected as 1500 r / min, and the transmission ratio of revolution to rotation is 1:2.5; (4) The hydrothermal synthesis temperature is 130 °C, the time is 2.5 h, the drying temperature is 120 °C, and the time is 9 h; (5) The microwave roasting temperature is 400 °C, the time is 20 min, the heating rate is 24 °C / min, and the solid substance taken out is the prepared catalyst.

[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 80% in the range of 200 °C to 250 °C. Example 4

[0026] This example provides a preparation method and application of an urban sludge biochar-based SCR catalyst, 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 municipal sludge is 450 °C and the time is 0.75 h; (2) The doping amount of rare earth concentrate is 50% of the municipal sludge-based biochar, and the selected mesh number is 300; (3) The high-energy ball milling time is 2 h, the ball-to-material ratio is 18:1, the rotation speed is selected as 1300 r / min, and the transmission ratio of revolution to rotation is 1:2; (4) The hydrothermal synthesis temperature is 130 °C, the time is 2.5 h, the drying temperature is 80 °C, and the time is 8 h; (5) The microwave roasting temperature is 400 °C, the time is 20 min, the heating rate is 25 °C / min, and the solid substance taken out is the prepared catalyst.

[0027] The prepared catalyst is used for denitrification experiments: Under the condition that NH 3 and NO are 1:1, O 2 is introduced, and N 2 is used for balancing. The denitrification rate of the obtained catalyst can reach 91% in the range of 200 °C to 250 °C.

[0028] This application aims to explore the preparation of a composite SCR denitrification catalyst with simple operation, high conversion rate and environmental friendliness using municipal sludge-based biochar and rare earth concentrate as raw materials. The technical solution of the present invention selects municipal sludge-based biochar with adsorption capacity in industrial production and rare earth concentrate rich in the synergistic effect of multiple components such as Ce, La, and Nd as raw materials, and preferably Bayan Obo rare earth concentrate as raw material. Under the combined action of sludge pyrolysis, high-energy ball milling, hydrothermal synthesis and microwave roasting, a large number of nanoscale pores are formed between the municipal sludge-based biochar and the rare earth concentrate, and the active crystal planes of the rare earth concentrate are fully exposed and the crystal lattice is distorted. The active components are highly dispersed and embedded around these pores, giving full play to the synergistic effect of multiple components of the sludge-based biochar and the rare earth concentrate. The prepared SCR denitrification catalyst has high catalytic activity, good selectivity and environmental friendliness. It follows the principles of prevention and control of atmospheric environmental pollution and resource utilization of solid waste, providing new ideas and scientific basis for the treatment and disposal of organic solid waste municipal sludge-based biochar, the comprehensive and efficient utilization of rare earth mineral resources, and the design and research and development of SCR denitrification catalysts.

[0029] The above specific implementation part specifically introduces 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 a municipal sludge-based biochar-rare earth concentrate composite SCR catalyst, characterized in that: The steps include: (1) Sludge pyrolysis: Municipal sludge is subjected to medium-temperature pyrolysis and carbonization treatment to prepare sludge-based biochar; (2) Grinding and sieving: The rare earth concentrate is mixed with the sludge-based biochar in proportion, and then ground and sifted in sequence to obtain a mixed material; (3) high energy ball milling: ball milling the mixture; (4) Hydrothermal synthesis: The ball-milled mixture is placed in a high-temperature and high-pressure heating kettle for hydrothermal synthesis. After being taken out, the suspension is dried in a vacuum drying oven; (5) Forming Calcination: Use microwave calcination to take out the solid material, which is the prepared catalyst.

2. The method for preparing a municipal sludge-based biochar-rare earth concentrate composite SCR catalyst according to claim 1, characterized in that: In step (1), the medium-temperature pyrolysis carbonization temperature is 450° C. to 600° C., and the time is 0.5 to 1 h.

3. The method for preparing a municipal sludge-based biochar-rare earth concentrate composite SCR catalyst according to claim 1, characterized in that: In step (2), the rare earth concentrate is added in an amount of 10% to 50% of the mass of the sludge-based biochar, and the sieve mesh number is 300 to 325.

4. The method for preparing a municipal sludge-based biochar-rare earth concentrate composite SCR catalyst according to claim 1, characterized in that: In step (3), 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 15:1 to 30:1, the rotation speed is selected to be 500 r / min to 1500 r / min, and the transmission ratio of revolution to rotation is 1:2 to 1:

3.

5. The method for preparing a municipal sludge-based biochar-rare earth concentrate composite SCR catalyst according to claim 1, characterized in that: In step (4), the hydrothermal synthesis temperature is 120°C to 150°C, and the time is 2 to 3 hours; the drying temperature is 80°C to 120°C, and the time is 8 hours to 10 hours.

6. A method for preparing a municipal sludge-based biochar-rare earth concentrate composite SCR catalyst according to any one of claims 1 to 5, characterized in that: In step (5), the calcination temperature is 350°C to 400°C, the calcination time is 20 to 30 minutes, and the heating rate is 20°C / min to 25°C / min.

7. An SCR catalyst, characterized in that: The method is prepared by any one of claims 1 to 6.

8. An SCR catalyst prepared according to the method according to any one of claims 1 to 6, used for catalytic denitration.

9. The use according to claim 8, characterized in that: Under the condition that NH3 and NO are 1:1, O2 and N2 are used for balance, and the SCR catalyst is used as a flue gas denitration catalyst.

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