Biochar SCR (Selective Catalytic Reduction) denitration catalyst as well as preparation method and application thereof

Abstract

The invention discloses a biochar SCR (Selective Catalytic Reduction) denitration catalyst. The catalyst is prepared from the following raw materials in percentage by mass: 50-70% of biochar and 30-50% of a binder, the biochar is prepared by carbonizing one or more of corn straw, wheat straw and soybean straw; the binder is one or more of phenolic resin, coal tar and starch. The invention further provides a preparation method of the catalyst, biomass is used as a raw material, and biochar is prepared through pretreatment and carbonization; the biochar and the binder are mixed according to a certain ratio, granulated and activated to prepare the biochar denitration catalyst, and the efficient purification of NOx can be realized through NH3-SCR (Selective Catalytic Reduction) at a relatively low temperature (50-150 DEG C).

Description

Technical Field

[0001] This invention relates to the field of environmentally friendly functional material preparation and application technology, specifically to the preparation of a biochar denitrification catalyst and its application in low-temperature SCR denitrification of iron and steel sintering flue gas. Background Technology

[0002] Nitrogen oxides (NOx) in sintering flue gas of iron and steel x Pollution control has always been a hot topic in the field of environmental engineering technology. NH3-Selective Catalytic Reduction (NH3-SCR) is an effective method for controlling NO pollution. x Purification technology. Currently, coal-based activated carbon, due to its certain low-temperature denitrification activity, is being used in the NO2 removal process of iron and steel sintering flue gas. x While widely used in pollution control, coal-based activated carbon denitrification suffers from high CO2 emissions due to the extensive use of coal. Under the "dual carbon" objective, the development of methods that can effectively purify NOx is crucial. x Environmentally friendly functional materials that can avoid CO2 emissions are the next generation of NO x The development trend of purification functional materials.

[0003] In recent years, research on the preparation of biochar from carbon-neutral biomass for flue gas denitrification has received widespread attention. Currently, biochar SCR denitrification catalysts generally suffer from low denitrification efficiency and low mechanical strength. By screening biomass raw materials and optimizing carbonization and activation processes, it is hoped that the SCR denitrification performance of biochar catalysts can be improved. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide a biochar denitrification catalyst prepared from natural biomass. Another technical problem to be solved by the present invention is to provide a method for preparing the catalyst. Yet another technical problem to be solved by the present invention is to provide applications of the catalyst.

[0005] The technical solution of the present invention is a biochar SCR denitrification catalyst, wherein the raw material mass ratio for preparing the catalyst is: 50-70% biochar and 30-50% binder;

[0006] The biochar is prepared by carbonization of one or more of corn stalks, wheat stalks, and soybean stalks;

[0007] The binder is one or more of phenolic resin, coal tar, and starch.

[0008] The above raw materials are mixed, granulated, dried and activated to obtain a biochar SCR denitrification catalyst.

[0009] This invention also provides a method for preparing the biochar SCR denitrification catalyst described above, the method comprising the following steps:

[0010] 1) Pretreatment: Crush the biomass raw materials;

[0011] 2) Carbonization: The biomass raw material is heated to 500-800℃ at a rate of 2-10℃ / min under N2 atmosphere or oxygen-deficient conditions and carbonized for 30-90min. The carbonized material is then pulverized to prepare biochar powder.

[0012] 3) Mixing: Biochar powder and binder are mixed in a certain mass ratio, wherein biochar accounts for 50-70% and binder accounts for 30-50%;

[0013] 4) Granulation: The mixed materials are granulated under a pressure of 0.5-5 MPa;

[0014] 5) Drying: Place the sample prepared above in an oven and dry at 50-100℃ for 4-12 hours;

[0015] 6) Activation: Under H2O and N2 atmosphere, the temperature is increased to 600-980℃ at a rate of 5-15℃ / min and activated for 30-90min to prepare biochar SCR denitrification catalyst.

[0016] According to a method for preparing a biochar SCR denitrification catalyst of the present invention, preferably, in step 1), the material is pulverized and then passed through a 60-100 mesh sieve; in step 2), the material is pulverized and then passed through an 80-150 mesh sieve. The initial raw materials are relatively coarse and do not need to be pulverized too finely. After carbonization, finer pulverization is required for uniform granulation.

[0017] According to the preparation method of the biochar SCR denitrification catalyst of the present invention, preferably, the oxygen-deficient condition in step 2) is: O2 volume content of 2%-10%. Oxygen deficiency refers to a low oxygen content, mainly to consider the economics of the production process. The oxygen content here simulates the actual production conditions.

[0018] Preferably, in the H2O and N2 mixed atmosphere described in step 6), the volume content of H2O is 10-40%.

[0019] According to a method for preparing a biochar SCR denitrification catalyst of the present invention, preferably, the granulation shape in step 4) is cylindrical. Granulation is necessary. The ultimate purpose of this activated carbon is to be suitable for desulfurization and denitrification in flue gas purification processes. Powdered form would cause carbon powder agglomeration, increased temperature rise, and a risk of fire. Because activated carbon granulators can only granulate into cylindrical particles, and long-term operation has verified that filling the denitrification tower with cylindrical granular activated carbon can meet the operational requirements, it is preferred to granulate to obtain cylindrical biochar particles.

[0020] Furthermore, step 4) granulation yields cylindrical samples with a diameter of 6-10 mm and a length of 5-12 mm. This process requires particles of a specific size, resulting in lower pressure loss within the tower and controlled energy consumption.

[0021] This invention also provides the application of the above-mentioned biochar SCR denitrification catalyst in low-temperature denitrification of flue gas.

[0022] According to the present invention, the application of a biochar SCR denitrification catalyst in low-temperature flue gas denitrification preferably has the following characteristics: NO content 100-600 ppm, NH3 content 100-600 ppm, O2 content 5-15%, denitrification reaction temperature 50-150℃, and volume hourly space velocity 400-30000 h⁻¹. -1 .

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] The biochar SCR denitrification catalyst prepared by this invention has higher denitrification efficiency and mechanical strength compared with coal-based activated carbon catalysts (see Table 1). Moreover, because it uses carbon-neutral biomass raw materials, it avoids high CO2 emissions compared with the preparation of activated carbon using coal.

[0025] Table 1 Comparison of performance indicators of denitrification catalysts

[0026]

[0027] Denitrification experimental conditions: NO concentration 200 ppm, NH3 concentration 200 ppm, O2 content 5%, reaction temperature 120℃, volume hourly space velocity 2000 h⁻¹ -1 Attached Figure Description

[0028] Figure 1 This is a process flow diagram for preparing the denitrification catalyst of the present invention. Detailed Implementation

[0029] To better understand the content of this invention, the following description, in conjunction with embodiments, further illustrates the invention; however, the examples given do not limit the scope of protection of this invention.

[0030] Example 1

[0031] (1) A biochar SCR denitrification catalyst, the preparation steps of which are as follows:

[0032] 1) Pretreatment: Crush the corn stalks and pass them through a 60-mesh sieve.

[0033] 2) Carbonization: Corn stalk raw material is heated to 600℃ at a rate of 5℃ / min under N2 atmosphere and carbonized for 60min; the carbonized material is crushed and passed through a 100-mesh sieve to prepare biochar powder.

[0034] 3) Mixing: Biochar powder and binder are mixed at a mass ratio of 6:4. The binder is a mixture of phenolic resin and coal tar at a mass ratio of 3:1.

[0035] 4) Granulation: The mixed material is granulated under a pressure of 2MPa to obtain a cylindrical sample with a diameter of 10mm and a length of 12mm.

[0036] 5) Drying: Place the cylindrical sample prepared in step 4) in an oven and dry at 80°C for 8 hours.

[0037] 6) Activation: Under a mixed atmosphere of H2O and N2, the temperature was programmed to reach 800℃ at a rate of 10℃ / min, and calcined for 60 min to prepare the biochar SCR denitrification catalyst. The H2O content in the mixed atmosphere was 30%.

[0038] (2) Evaluation of SCR denitrification performance

[0039] The experimental conditions for SCR denitrification were set as follows: NO concentration 200 ppm, NH3 concentration 200 ppm, O2 content 5%, reaction temperature 50-150℃, and volume hourly space velocity (VHSV) 2000 h⁻¹. -1 The NO concentration was detected using a flue gas analyzer, and the denitrification efficiency was calculated. The compressive strength and abrasion resistance of the biochar SCR denitrification catalyst were tested using a compressive strength tester and an abrasion resistance tester, respectively. The results are shown in Table 2.

[0040] Table 2. Denitrification efficiency and pressure and abrasion resistance values ​​of biochar SCR denitrification catalyst.

[0041]

[0042] The results in the table above show that biochar and binder can be used to prepare biochar denitrification catalysts under the method of the present invention. These catalysts can be used for denitrification under relatively low temperature conditions (50-150℃) and have high mechanical strength, meeting the application requirements for the strength of activated carbon catalysts in standards GB / T 7701.3-2008 and LY / T 3284-2021.

[0043] Example 2

[0044] (1) A biochar SCR denitrification catalyst, the preparation steps of which are as follows:

[0045] 1) Pretreatment: Crush the corn stalks and pass them through a 60-mesh sieve.

[0046] 2) Carbonization: Corn stalk raw material is heated to 700℃ at a rate of 5℃ / min under N2 atmosphere and carbonized for 40min; the carbonized material is crushed and passed through a 100-mesh sieve to prepare biochar powder.

[0047] 3) Mixing: Biochar powder and binder are mixed at a mass ratio of 6:4. The binder is a mixture of phenolic resin and coal tar at a mass ratio of 3:1.

[0048] 4) Granulation: The mixed material is granulated under a pressure of 2MPa to obtain a cylindrical sample with a diameter of 10mm and a length of 12mm.

[0049] 5) Drying: Place the cylindrical sample prepared in step 4) in an oven and dry at 80°C for 8 hours.

[0050] 6) Activation: Under a mixed atmosphere of H2O and N2, the temperature was programmed to reach 800℃ at a rate of 10℃ / min, and calcined for 60 min to prepare the biochar SCR denitrification catalyst. The H2O content in the mixed atmosphere was 30%.

[0051] (2) Evaluation of SCR denitrification performance

[0052] The experimental conditions for SCR denitrification were set as follows: NO concentration 200 ppm, NH3 concentration 200 ppm, O2 content 5%, reaction temperature 50-150℃, and volume hourly space velocity (VHSV) 2000 h⁻¹. -1 The NO concentration was detected using a flue gas analyzer, and the denitrification efficiency was calculated. The compressive strength and abrasion resistance of the biochar SCR denitrification catalyst were tested using a compressive strength tester and an abrasion resistance tester, respectively. The experimental results are shown in Table 3.

[0053] Table 3. Denitrification efficiency and pressure and wear resistance values ​​of biochar SCR denitrification catalyst.

[0054]

[0055] Compared with the biochar SCR denitrification catalyst in Example 1, the denitrification efficiency, pressure resistance, and wear resistance of the above table are slightly lower, indicating that controlling the carbonization conditions can regulate the denitrification efficiency and mechanical strength of the activated carbon catalyst.

[0056] Example 3

[0057] (1) A biochar SCR denitrification catalyst, the preparation steps of which are as follows:

[0058] 1) Pretreatment: Crush the corn stalks and pass them through a 60-mesh sieve.

[0059] 2) Carbonization: Corn stalk raw material is heated to 600℃ at a rate of 5℃ / min under N2 atmosphere and carbonized for 60min; the carbonized material is crushed and passed through a 100-mesh sieve to prepare biochar powder.

[0060] 3) Mixing: Biochar powder and binder are mixed at a mass ratio of 7:3. The binder is a mixture of phenolic resin and coal tar at a mass ratio of 1:1.

[0061] 4) Granulation: The mixed material is granulated under a pressure of 2MPa to obtain a cylindrical sample with a diameter of 10mm and a length of 12mm.

[0062] 5) Drying: Place the cylindrical sample prepared in step 4) in an oven and dry at 80°C for 8 hours.

[0063] 6) Activation: Under a mixed atmosphere of H2O and N2, the temperature was programmed to reach 800℃ at a rate of 10℃ / min, and calcined for 60 min to prepare the biochar SCR denitrification catalyst. The H2O content in the mixed atmosphere was 30%.

[0064] (2) Evaluation of SCR denitrification performance

[0065] The experimental conditions for SCR denitrification were set as follows: NO concentration 200 ppm, NH3 concentration 200 ppm, O2 content 5%, reaction temperature 50-150℃, and volume hourly space velocity (VHSV) 2000 h⁻¹. -1 The NO concentration was detected using a flue gas analyzer, and the denitrification efficiency was calculated. The compressive strength and abrasion resistance of the biochar SCR denitrification catalyst were tested using a compressive strength tester and an abrasion resistance tester, respectively. The experimental results are shown in Table 4.

[0066] Table 4. Denitrification efficiency and pressure and abrasion resistance values ​​of biomass-based activated carbon SCR denitrification catalyst.

[0067]

[0068] Compared with the biochar SCR denitrification catalyst in Example 1, the denitrification efficiency of the above table is not significantly different, but the pressure resistance and wear resistance are significantly reduced; indicating that controlling the amount of binder added and the mixing ratio of different types of binders is mainly beneficial to regulating the mechanical strength of the biochar denitrification catalyst.

[0069] Example 4

[0070] (2) A biochar SCR denitrification catalyst, the preparation steps of which are as follows:

[0071] 1) Pretreatment: Crush the corn stalks and pass them through a 60-mesh sieve.

[0072] 2) Carbonization: Corn stalk raw material is heated to 600℃ at a rate of 5℃ / min under N2 atmosphere and carbonized for 60min; the carbonized material is crushed and passed through a 100-mesh sieve to prepare biochar powder.

[0073] 3) Mixing: Biochar powder and binder are mixed at a mass ratio of 6:4. The binder is a mixture of phenolic resin and coal tar at a mass ratio of 3:1.

[0074] 4) Granulation: The mixed material is granulated under a pressure of 2MPa to obtain a cylindrical sample with a diameter of 10mm and a length of 12mm.

[0075] 5) Drying: Place the cylindrical sample prepared in step 4) in an oven and dry at 80°C for 8 hours.

[0076] 6) Activation: Under a mixed atmosphere of H2O and N2, the temperature was programmed to reach 800℃ at a rate of 10℃ / min, and calcined for 60 min to prepare the biochar SCR denitrification catalyst. The H2O content in the mixed atmosphere was 10%.

[0077] (2) Evaluation of SCR denitrification performance

[0078] The experimental conditions for SCR denitrification were set as follows: NO concentration 200 ppm, NH3 concentration 200 ppm, O2 content 5%, reaction temperature 50-150℃, and volume hourly space velocity (VHSV) 2000 h⁻¹. -1 The NO concentration was detected using a flue gas analyzer, and the denitrification efficiency was calculated. The compressive strength and abrasion resistance of the biochar SCR denitrification catalyst were tested using a compressive strength tester and an abrasion resistance tester, respectively. The experimental results are shown in Table 5.

[0079] Table 5. Denitrification efficiency and pressure and abrasion resistance values ​​of biochar SCR denitrification catalyst.

[0080]

[0081] The results in the table above show that the denitrification efficiency and mechanical strength of the biochar SCR denitrification catalyst decreased compared with those in Example 1, indicating that controlling the activation atmosphere can regulate the denitrification efficiency and mechanical strength of the biochar denitrification catalyst.

[0082] Example 5

[0083] (3) A biochar SCR denitrification catalyst, the preparation steps of which are as follows:

[0084] 1) Pretreatment: Crush the corn stalks and pass them through a 60-mesh sieve.

[0085] 2) Carbonization: Corn stalk raw material is heated to 600℃ at a rate of 5℃ / min under N2 atmosphere and carbonized for 60min; the carbonized material is crushed and passed through a 100-mesh sieve to prepare biochar powder.

[0086] 3) Mixing: Biochar powder and binder are mixed at a mass ratio of 6:4. The binder is a mixture of phenolic resin and coal tar at a mass ratio of 3:1.

[0087] 4) Granulation: The mixed material is granulated under a pressure of 2MPa to obtain a cylindrical sample with a diameter of 10mm and a length of 12mm.

[0088] 5) Drying: Place the cylindrical sample prepared in step 4) in an oven and dry at 80°C for 8 hours.

[0089] 6) Activation: Under a mixed atmosphere of H2O and N2, the temperature was programmed to reach 920℃ at a rate of 5℃ / min, and calcined for 45 min to prepare the biochar SCR denitrification catalyst. The H2O content in the mixed atmosphere was 30%.

[0090] (2) Evaluation of SCR denitrification performance

[0091] The experimental conditions for SCR denitrification were set as follows: NO concentration 200 ppm, NH3 concentration 200 ppm, O2 content 5%, reaction temperature 50-150℃, and volume hourly space velocity (VHSV) 2000 h⁻¹. -1 The NO concentration was detected using a flue gas analyzer, and the denitrification efficiency was calculated. The compressive strength and abrasion resistance of the biochar SCR denitrification catalyst were tested using a compressive strength tester and an abrasion resistance tester, respectively. The experimental results are shown in Table 6.

[0092] Table 6. Denitrification efficiency and pressure and abrasion resistance values ​​of biochar SCR denitrification catalyst.

[0093]

[0094] The results in the table above show that the denitrification efficiency and mechanical strength of the biochar SCR denitrification catalyst decreased compared with those in Example 1, indicating that controlling the activation temperature and time can regulate the denitrification efficiency and mechanical strength of the biochar denitrification catalyst.

[0095] Comparative Example 1

[0096] Only the corn stalks described in this application are added, and the mixture is processed according to the pretreatment, carbonization, mixing, granulation, drying, and activation conditions of Example 1.

[0097] Comparative Example 2

[0098] Only one type of commercial coal-based activated carbon is used.

[0099] Comparative Example 3

[0100] Only one type of commercial coconut shell-based activated carbon is used.

[0101] The activated carbon catalysts obtained above were all tested under the SCR denitrification experimental conditions of Example 1. The denitrification efficiency results are shown in Table 7, and the intensity results are shown in Table 8.

[0102] Table 7 Comparison of denitrification efficiency between comparative examples and Example 1

[0103]

[0104] Table 8 Comparison of strength values ​​between the comparative example and Example 1

[0105]

[0106]

[0107] The results in the table above show that the biochar SCR denitrification catalyst prepared in this invention has higher denitrification efficiency at lower temperatures (50-150℃) compared with other denitrification catalysts, and also has higher mechanical strength, which can meet the requirements of the application strength standards for activated carbon catalysts (GB / T 7701.3-2008 and LY / T 3284-2021).

Claims

1. A biochar SCR denitrification catalyst, characterized in that: The raw material mass ratio for preparing this catalyst is: 50-70% biochar and 30-50% binder; The biochar is prepared by carbonization of one or more of corn stalks, wheat stalks, and soybean stalks; The binder is one or more of phenolic resin, coal tar, and starch.

2. The method for preparing the biochar SCR denitrification catalyst according to claim 1, characterized in that: The method includes the following steps: 1) Pretreatment: Crush the biomass raw materials; 2) Carbonization: The biomass raw material is heated to 500-800℃ at a rate of 2-10℃ / min under N2 atmosphere or oxygen-deficient conditions and carbonized for 30-90min. The carbonized material is then pulverized to prepare biochar powder. 3) Mixing: Biochar powder and binder are mixed in a certain mass ratio, wherein biochar accounts for 50-70% and binder accounts for 30-50%; 4) Granulation: The mixed materials are granulated under a pressure of 0.5-5 MPa; 5) Drying: Place the sample prepared above in an oven and dry at 50-100℃ for 4-12 hours; 6) Activation: Under H2O and N2 atmosphere, the temperature is increased to 600-980℃ at a rate of 5-15℃ / min and activated for 30-90min to prepare biochar SCR denitrification catalyst.

3. The method for preparing a biochar SCR denitrification catalyst according to claim 2, characterized in that: Step 1) involves pulverizing the material and then passing it through a 60-100 mesh sieve; Step 2) involves pulverizing the material and then passing it through an 80-150 mesh sieve.

4. The method for preparing a biochar SCR denitrification catalyst according to claim 2, characterized in that: The oxygen-deficient conditions described in step 2) are: O2 volume content of 2%-10%; in the mixed atmosphere of H2O and N2 described in step 6), the volume content of H2O is 10-40%.

5. The method for preparing a biochar SCR denitrification catalyst according to claim 2, characterized in that: In step 4), the granulation shape is cylindrical.

6. The method for preparing a biochar SCR denitrification catalyst according to claim 2, characterized in that: Step 4) granulation yields cylindrical samples with a diameter of 6-10 mm and a length of 5-12 mm.

7. The application of the biochar SCR denitrification catalyst according to claim 1 in low-temperature denitrification of flue gas.

8. The application of a biochar SCR denitrification catalyst according to claim 7 in low-temperature flue gas denitrification, characterized in that: The NO content is 100-600 ppm, the NH3 content is 100-600 ppm, the O2 content is 5-15%, the denitrification reaction temperature is 50-150℃, and the volume hourly space velocity is 400-30000 h⁻¹. -1 .

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