Environment-friendly biomass fuel and preparation method thereof

Abstract

The invention relates to the technical field of fuels, and discloses an environment-friendly biomass fuel and a preparation method thereof. The environment-friendly biomass fuel is prepared from the following materials in parts by weight: 60 to 70 parts of sawdust, 25 to 35 parts of activated biochar, 15 to 20 parts of phosphoric acid activated red mud, 3 to 5 parts of waste catering grease, 2 to 4 parts of calcium lignosulphonate and 0.8 to 1.2 parts of cerium oxide. Wherein the activated biochar is prepared by soaking rice hulls in a ZnCl2 solution; the phosphoric acid activated red mud is prepared by adding dried red mud into a phosphoric acid solution. According to the environment-friendly biomass fuel and the preparation method thereof, the combustion characteristic of the environment-friendly biomass fuel is improved, and the combustion efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fuels, and in particular to an environmentally friendly biomass fuel and a preparation method thereof. Background Art

[0002] With the increasing depletion of traditional fossil fuels and the increasingly serious environmental pollution and climate change caused by their combustion, the search for alternative clean energy sources has become a critical issue in the global energy sector. Biomass energy, as a renewable carbon source, offers advantages such as abundant reserves, widespread distribution, and low pollution, and is considered a key direction for future energy restructuring. As an important application of biomass energy, the development and application of environmentally friendly biomass fuels are of great significance for alleviating the energy crisis, reducing greenhouse gas emissions, and protecting the ecological environment.

[0003] Environmentally friendly biomass fuels refer to solid, liquid, or gaseous fuels produced from biomass raw materials through physical, chemical, or biological processing. They exhibit efficient, clean combustion characteristics and have minimal environmental impact during production, use, and disposal. Biomass raw materials primarily come from agricultural waste (such as straw and rice husks), forestry waste (such as branches and bark), municipal organic waste, and livestock and poultry manure. These raw materials can be continuously regenerated through natural growth processes, resulting in a sustainable supply. Patent CN118109234A discloses a fuel composition combining municipal sludge with combustible solid waste, its preparation method, and its use. This involves the secondary utilization of solid waste, addressing municipal sludge pollution, reducing coal use, conserving resources, and reducing pollution.

[0004] Biomass absorbs carbon dioxide during its growth, and the amount of carbon dioxide released during its combustion is basically equivalent to the amount absorbed during its growth. Therefore, the combustion of biomass fuel has a carbon neutrality effect and can effectively reduce greenhouse gas emissions. At the same time, the content of elements such as sulfur and nitrogen in biomass fuel is low, and the pollutants such as sulfur dioxide and nitrogen oxides produced during combustion are relatively small, and the pollution to the environment is relatively small. Compared with traditional fossil fuels, some environmentally friendly biomass fuels have a lower calorific value, resulting in more fuel consumption during combustion to meet the same energy demand. The combustion characteristics of biomass fuels are different from those of traditional fossil fuels, such as higher ignition temperature and slower combustion speed, which may affect the normal operation and combustion efficiency of combustion equipment. Based on this, the present invention provides an environmentally friendly biomass fuel and a preparation method thereof. Summary of the Invention

[0005] The purpose of the present invention is to provide an environmentally friendly biomass fuel and a preparation method thereof, thereby improving the combustion characteristics of the environmentally friendly biomass fuel and enhancing the combustion efficiency.

[0006] On the one hand, the present invention provides an environmentally friendly biomass fuel, comprising the following materials in parts by weight: 60-70 parts of sawdust, 25-35 parts of activated biochar, 15-20 parts of phosphoric acid-activated red mud, 3-5 parts of waste cooking oil, 2-4 parts of calcium lignin sulfonate, and 0.8-1.2 parts of cerium oxide.

[0007] Furthermore, the preparation method of phosphoric acid-activated red mud includes: adding dried red mud to a phosphoric acid solution, stirring at a speed of 200-300 rpm and a temperature of 75-85°C for 2-4 hours, vacuum filtering, washing the filter cake with deionized water until neutral, and drying in an oven at 100-110°C until the moisture content is ≤5%.

[0008] Furthermore, the mass concentration of the phosphoric acid aqueous solution is 5-10%; and the usage ratio of the dried red mud to the phosphoric acid aqueous solution is 1:10-12.

[0009] Furthermore, the drying of the red mud includes drying the red mud at a temperature of 80-90° C. for 4-6 hours.

[0010] Furthermore, the preparation method of the activated biochar comprises: immersing the rice husk biochar in a ZnCl2 solution, activating it at 110-120°C for 2-4 hours, and washing it with deionized water until there is no Cl - Under nitrogen conditions, the temperature is raised to 550-650°C at a rate of 10°C / min, kept warm for 60-70 minutes, and cooled to room temperature after the reaction is completed.

[0011] Furthermore, the ZnCl2 solution is a ZnCl2 aqueous solution with a mass concentration of 10-12%, and the usage ratio of the rice husk biochar to the ZnCl2 solution is 1g:4-6mL.

[0012] Furthermore, the wood chips are wood processing waste chips, including at least one of pine wood chips, fir wood chips, poplar wood chips, and fruit wood chips.

[0013] Furthermore, the waste catering grease needs to be pretreated, and the steps include: filtering to remove solid impurities, heating to 75-85°C for sedimentation and dehydration for 1-2 hours, and then centrifuging at 3000-4000 rpm for 15-20 minutes to obtain the waste catering grease.

[0014] Furthermore, the water content of the waste catering oil is ≤5%, and the acid value is ≤5mg KOH / g.

[0015] On the other hand, the present invention provides a method for preparing an environmentally friendly biomass fuel, comprising the following steps: crushing sawdust into particles of 1-3 mm; weighing raw materials according to the formula amount, stirring and mixing activated biochar, phosphoric acid-activated red mud and cerium oxide at a speed of 100-200 r / min for 60-80 minutes to obtain a catalyst, then placing the sawdust, waste catering oil and fat and calcium lignin sulfonate in a reactor and stirring at 200-250 rpm for 40-50 minutes, introducing nitrogen to replace the air, adding a catalyst, heating to 380-450°C at 5°C / min, and carrying out a catalytic cracking reaction at 8-12 MPa for 80-100 minutes; cooling the reaction product to 80-100°C for gas-liquid-solid separation, and collecting the liquid product; and refining the liquid product to obtain the environmentally friendly biomass fuel.

[0016] The beneficial effects of the present invention are: The activated biochar and phosphoric acid-activated red mud of the present invention are modified through physical-chemical synergistic modification to construct a high specific surface area and multi-level pore structure. After the activated biochar is activated by impregnation with a ZnCl2 solution, a rich microporous-mesoporous structure is formed on the surface, which significantly improves the adsorption capacity of volatile organic compounds. At the same time, its residual carbon skeleton serves as a catalytic site, which can promote the cracking of large molecular hydrocarbons into small molecular combustible gases. The phosphoric acid-activated red mud removes alkaline oxides such as CaO and MgO in the red mud through acid leaching treatment, reducing the generation of sulfur oxides during the combustion process; at the same time, phosphate ions form phosphate complexes with iron and aluminum oxides in the red mud, enhancing the thermal stability and catalytic activity of the material. When the two work synergistically, the adsorption-cracking function of the activated biochar and the desulfurization-catalytic function of the phosphoric acid-activated red mud complement each other: the former promotes deep cracking by extending the residence time of volatiles, and the latter reduces pollutant emissions by inhibiting sulfur release and catalytic oxidation reactions, jointly improving the calorific value and combustion efficiency of the fuel.

[0017] After the waste catering oils and fats in the present invention are pre-treated by dehydration and centrifugation, the moisture content is reduced to ≤5% and the acid value is ≤5mgKOH / g, which effectively inhibits the side reactions caused by water vapor and the catalyst poisoning caused by free fatty acids during the cracking process. When the pre-treated oils and fats are co-cracked with sawdust, the long-chain fatty acid glycerides thereof are decomposed into short-chain alkanes and olefins at high temperatures, and undergo synergistic reforming reactions with the cellulose / hemicellulose cracking products in the sawdust to generate more high-value-added small molecule hydrocarbons. In addition, the low ash content of the oils and fats reduces the accumulation of inorganic salts in the cracking residues, avoids the clogging of the catalyst pores, and forms a synergistic relationship with the high porosity of the activated biochar to maintain the continuous and efficient progress of the cracking reaction. Due to the high moisture content and high acid value, unpretreated oils and fats will cause the excessive generation of CO and nitrogen oxides in the cracking gas, thereby reducing the quality of the fuel.

[0018] In the present invention, cerium oxide is used as an oxygen storage catalyst. 3+ / Ce 4+ The redox cycle realizes the dynamic regulation of oxygen in the combustion process: in the oxygen-deficient region, CeO2 releases lattice oxygen to promote the deep oxidation of incomplete combustion products such as CO and hydrocarbons; in the oxygen-rich region, Ce 3+ Oxidized to Ce 4+ It also absorbs excess oxygen and inhibits thermal NO caused by local overheating. x In addition, the abundant oxygen vacancies on the surface of CeO2 can adsorb SO2 and NO x , through catalytic oxidation, it is converted into SO3 and NO2, and then reacts with alkaline oxides such as MgO in phosphoric acid activated red mud to form stable sulfate / nitrate, which is fixed in the ash, significantly reducing the emission of gaseous pollutants. x Large amounts of emissions due to insufficient oxidation indicate that its oxidation catalysis is a key link in achieving clean combustion.

[0019] In the present invention, activated biochar, phosphoric acid-activated red mud and cerium oxide constitute a three-way catalytic system, which realizes efficient fuel conversion through a multi-stage reaction path of "adsorption-cracking-oxidation". The microporous structure of activated biochar preferentially adsorbs large molecular hydrocarbons, and its surface acidic sites such as -COOH and -OH catalyze the breakage of CC bonds; Fe2O3 / Al2O3 in phosphoric acid-activated red mud acts as a Lewis acid center to further catalyze the cracking reaction, while its phosphate groups combine with sulfur compounds to form stable salts, inhibiting the release of SO2; cerium oxide promotes the complete oxidation of small molecular hydrocarbons through oxygen vacancies, reducing the formation of carbon deposits. When the three act synergistically, the cracking-desulfurization function of activated biochar and phosphoric acid-activated red mud provides reactants such as CO and uncracked hydrocarbons for the deep oxidation of cerium oxide, while the oxidation products of cerium oxide such as CO2 and H2O reduce the temperature of the cracking zone through the dilution effect, inhibiting the formation of tar caused by secondary cracking. Unactivated biochar or untreated red mud will destroy this synergistic system, resulting in insufficient cracking or uncontrolled sulfur release.

[0020] The temperature, pressure and heating rate of the catalytic cracking reaction in the present invention achieve a balance between cracking depth and product selectivity by affecting the diffusion of reactants and the exposure of catalyst active sites. High temperature and high pressure conditions enhance the diffusion rate of volatiles in the catalyst pores and promote the adsorption and cracking of macromolecular hydrocarbons. At the same time, slow heating in a nitrogen atmosphere avoids coke deposition caused by local overheating and maintains the continuous activity of the catalyst. If the biochar or red mud is not activated, its low porosity and weak catalytic activity will lead to a decrease in the cracking reaction rate and an increase in uncracked components. Insufficient oil pretreatment or lack of cerium oxide will increase side reactions or insufficient oxidation, which will damage the calorific value and environmental performance of the product. The coordinated optimization of process parameters and component modification is the core guarantee for achieving efficient and clean combustion of fuels. DETAILED DESCRIPTION

[0021] The following is a clear and complete description of the technical solution of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0022] It should be noted that the red mud in the present invention was purchased from Shandong Aluminum Co., Ltd. To better illustrate the technical solution of the present invention, the sawdust in the examples and comparative examples of the present invention is poplar processing waste, but is not limited to poplar processing waste, and also includes at least one of pine sawdust, fir sawdust, and fruit sawdust.

[0023] Example 1 This embodiment provides an environmentally friendly biomass fuel, comprising the following materials in parts by weight: 65 parts sawdust, 30 parts activated biochar, 18 parts phosphoric acid-activated red mud, 4 parts waste cooking oil, 3 parts calcium lignin sulfonate, and 1 part cerium oxide; Among them, the waste catering grease needs to be pretreated, including the following steps: filtering to remove solid impurities, heating to 80°C for sedimentation and dehydration for 1.5 hours, and then centrifuging at 3500 rpm for 18 minutes to obtain the waste catering grease; the final water content is 5wt% and the acid value is 5mg KOH / g; Among them, the preparation method of phosphoric acid-activated red mud includes: drying the red mud at a temperature of 85°C for 5 hours to obtain dried red mud, adding 10g of dried red mud to 110g of 8% phosphoric acid aqueous solution, stirring at a speed of 250rpm and a temperature of 80°C for 3 hours, vacuum filtering, washing the filter cake with deionized water until neutral, and drying in an oven at 105°C to a moisture content of 5wt%.

[0024] The preparation method of activated biochar includes: immersing 100g of rice husk biochar in 500mL of 11% ZnCl2 aqueous solution, activating at 115℃ for 3h, and washing with deionized water until there is no Cl2. - Under nitrogen conditions, the temperature was raised to 600°C at a rate of 10°C / min, kept at this temperature for 65 min, and cooled to room temperature after the reaction was completed.

[0025] The preparation method of environmentally friendly biomass fuel comprises the following steps: crushing sawdust into particles with an average particle size of 2 mm, weighing raw materials according to a formula, stirring and mixing activated biochar, phosphoric acid-activated red mud and cerium oxide at a speed of 150 r / min for 70 minutes to obtain a catalyst, then placing the sawdust particles, waste catering oil and fat and calcium lignin sulfonate in a reactor and stirring at 220 rpm for 45 minutes, introducing nitrogen to replace the air, adding a catalyst, heating to 410°C at a speed of 5°C / min, and performing a catalytic cracking reaction at 10 MPa for 90 minutes; cooling the reaction product to 90°C for gas-liquid-solid separation, and collecting a liquid product; refining the liquid product, dehydrating it through a 3Å molecular sieve column at a temperature of 60°C to a water content of 0.37%, and then filtering it through a silica gel column with a silica gel: oil = 1:0.2 to remove polar impurities to obtain the environmentally friendly biomass fuel.

[0026] Example 2 This embodiment provides an environmentally friendly biomass fuel, comprising the following materials in parts by weight: 60 parts sawdust, 25 parts activated biochar, 15 parts phosphoric acid-activated red mud, 3 parts waste cooking oil, 2 parts calcium lignin sulfonate, and 0.8 parts cerium oxide; Among them, the waste catering grease needs to be pretreated, including the following steps: filtering to remove solid impurities, heating to 80°C for sedimentation and dehydration for 1.5 hours, and then centrifuging at 3500 rpm for 18 minutes to obtain the waste catering grease; the final water content is 5wt% and the acid value is 5mg KOH / g; Among them, the preparation method of phosphoric acid-activated red mud includes: drying the red mud at a temperature of 80°C for 4 hours to obtain dried red mud, adding 10g of dried red mud to 100g of a 5% phosphoric acid aqueous solution, stirring at a speed of 200rpm and a temperature of 75°C for 2 hours, vacuum filtering, washing the filter cake with deionized water until neutral, and drying in an oven at 100°C to a moisture content of 5wt%.

[0027] The preparation method of activated biochar includes: immersing 100g of rice husk biochar in 400mL of 10% ZnCl2 aqueous solution, activating at 110℃ for 2h, and washing with deionized water until there is no Cl2. - Under nitrogen conditions, the temperature was raised to 550°C at a rate of 10°C / min, kept warm for 60 min, and cooled to room temperature after the reaction was completed.

[0028] The preparation method of environmentally friendly biomass fuel comprises the following steps: crushing sawdust into particles with an average particle size of 1 mm, weighing raw materials according to the formula amount, stirring and mixing activated biochar, phosphoric acid-activated red mud and cerium oxide at a speed of 100 / min for 60 minutes to obtain a catalyst, then placing the sawdust particles, waste catering oil and fat and calcium lignin sulfonate in a reactor and stirring at 200 rpm for 40 minutes, introducing nitrogen to replace the air, adding the catalyst, heating to 380°C at 5°C / min, and performing a catalytic cracking reaction at 8MPa for 80 minutes; cooling the reaction product to 80°C for gas-liquid-solid separation, and collecting the liquid product; refining the liquid product, dehydrating it through a 3Å molecular sieve column at a temperature of 60°C to a water content of 0.31%, and then filtering it through a silica gel column with a silica gel: oil = 1:0.2 to remove polar impurities to obtain the environmentally friendly biomass fuel.

[0029] Example 3 This embodiment provides an environmentally friendly biomass fuel, comprising the following materials by weight: 70 parts sawdust, 35 parts activated biochar, 20 parts phosphoric acid-activated red mud, 5 parts waste cooking oil, 4 parts calcium lignin sulfonate, and 1.2 parts cerium oxide; Among them, the waste catering grease needs to be pretreated, including the following steps: filtering to remove solid impurities, heating to 80°C for sedimentation and dehydration for 1.5 hours, and then centrifuging at 3500 rpm for 18 minutes to obtain the waste catering grease; the final water content is 5wt% and the acid value is 5mg KOH / g; Among them, the preparation method of phosphoric acid-activated red mud includes: drying the red mud at a temperature of 90°C for 6 hours to obtain dried red mud, adding 10g of dried red mud to 120g of a 10% phosphoric acid aqueous solution, stirring at a speed of 300rpm and a temperature of 85°C for 4 hours, vacuum filtering, washing the filter cake with deionized water until neutral, and drying in an oven at 110°C to a moisture content of 5wt%.

[0030] The preparation method of activated biochar includes: immersing 100g of rice husk biochar in 600mL of 12% ZnCl2 aqueous solution, activating at 120℃ for 4h, and washing with deionized water until there is no Cl2. - Under nitrogen conditions, the temperature was raised to 650°C at a rate of 10°C / min, kept at this temperature for 70 min, and cooled to room temperature after the reaction was completed.

[0031] The preparation method of environmentally friendly biomass fuel comprises the following steps: crushing sawdust into particles with an average particle size of 2 mm, weighing raw materials according to a formula, stirring and mixing activated biochar, phosphoric acid-activated red mud and cerium oxide at a speed of 200 r / min for 80 minutes to obtain a catalyst, then placing the sawdust particles, waste catering oil and fat and calcium lignin sulfonate in a reactor and stirring at 250 rpm for 50 minutes, introducing nitrogen to replace the air, adding a catalyst, heating to 450°C at a speed of 5°C / min, and performing a catalytic cracking reaction at 12 MPa for 100 minutes; cooling the reaction product to 100°C for gas-liquid-solid separation, and collecting a liquid product; refining the liquid product, dehydrating it through a 3Å molecular sieve column at a temperature of 60°C to a water content of 0.29%, and then filtering it through a silica gel column with a silica gel: oil ratio of 1:0.2 to remove polar impurities to obtain the environmentally friendly biomass fuel.

[0032] Example 4 This embodiment provides an environmentally friendly biomass fuel, comprising the following materials by weight: 60 parts sawdust, 35 parts activated biochar, 15 parts phosphoric acid-activated red mud, 5 parts waste cooking oil, 2 parts calcium lignin sulfonate, and 1.2 parts cerium oxide; Among them, the waste catering grease needs to be pretreated, including the following steps: filtering to remove solid impurities, heating to 80°C for sedimentation and dehydration for 1.5 hours, and then centrifuging at 3500 rpm for 18 minutes to obtain the waste catering grease; the final water content is 5wt% and the acid value is 5mg KOH / g; Among them, the preparation method of phosphoric acid-activated red mud includes: drying the red mud at a temperature of 80°C for 6 hours to obtain dried red mud, adding 10g of dried red mud to 100g of a 10% phosphoric acid aqueous solution, stirring at a speed of 200rpm and a temperature of 85°C for 2 hours, vacuum filtering, washing the filter cake with deionized water until neutral, and drying in an oven at 110°C to a moisture content of 5wt%.

[0033] The preparation method of activated biochar includes: immersing 100g of rice husk biochar in 400mL of 12% ZnCl2 aqueous solution, activating at 110℃ for 4h, and washing with deionized water until there is no Cl2. - Under nitrogen conditions, the temperature was raised to 550°C at a rate of 10°C / min, kept at this temperature for 70 min, and cooled to room temperature after the reaction was completed.

[0034] The preparation method of environmentally friendly biomass fuel comprises the following steps: crushing sawdust into particles with an average particle size of 1 mm, weighing raw materials according to a formula, stirring and mixing activated biochar, phosphoric acid-activated red mud and cerium oxide at a speed of 100 r / min for 80 minutes to obtain a catalyst, then placing the sawdust particles, waste catering oil and fat and calcium lignin sulfonate in a reactor and stirring at 200 rpm for 50 minutes, introducing nitrogen to replace the air, adding a catalyst, heating to 380°C at 5°C / min, and performing a catalytic cracking reaction at 12 MPa for 80 minutes; cooling the reaction product to 100°C for gas-liquid-solid separation, and collecting a liquid product; refining the liquid product, dehydrating it through a 3Å molecular sieve column at a temperature of 60°C to a water content of 0.35%, and then filtering it through a silica gel column with a silica gel: oil ratio of 1:0.2 to remove polar impurities to obtain the environmentally friendly biomass fuel.

[0035] Comparative Example 1 Different from Example 1, the activated biochar in this comparative example was replaced by original rice husk biochar of equal mass, which was not impregnated with ZnCl2 and subjected to high temperature treatment.

[0036] Comparative Example 2 Different from Example 1, the raw materials in this comparative example did not contain activated biochar.

[0037] Comparative Example 3 The difference from Example 1 is that in this comparative example, the phosphoric acid-activated red mud is replaced by an equal mass of unactivated red mud.

[0038] Comparative Example 4 Different from Example 1, the raw materials in this comparative example do not contain phosphoric acid-activated red mud.

[0039] Comparative Example 5 Different from Example 1, the waste grease in this comparative example was not pretreated, and the original waste catering grease that had not been filtered / dehydrated / centrifuged was used, with an acid value of 20 mg KOH / g and a water content of 15%.

[0040] Comparative Example 6 Different from Example 1, the raw materials in this comparative example do not contain cerium oxide.

[0041] Calorific value: tested in accordance with GB / T 384-1981 standard.

[0042] Combustion efficiency: Weigh 1.0 g of the fuel from the Examples / Comparative Examples and place it in a quartz boat. Raise the temperature at 10°C / min to 850°C. Start timing when the temperature reaches 850°C (t=0). Record the sample mass (mt) every 30 seconds. Burnout is considered complete when the mass change rate is less than 0.1% / min for three consecutive times. Record the time. Pollutant emission test: Flue gas analyzer (Testo 350) online monitoring of CO emission concentration (ppm), NO x Emission concentration (ppm), SO2 emission concentration (ppm).

[0043] Table 1 Test results Group Calorific value (MJ / kg) Burnout time (min) CO emission concentration (ppm) <![CDATA[SO2 emission concentration (ppm)]]> <![CDATA[NO x Emission concentration (ppm)]]> Example 1 40.2 17.8 79 30 105 Example 2 39.3 19.5 98 42 125 Example 3 39.8 18.2 85 35 112 Example 4 39.5 20.1 105 48 135 Comparative Example 1 38.3 25.6 185 68 180 Comparative Example 2 37.7 28.3 220 85 205 Comparative Example 3 39.1 23.2 150 210 160 Comparative Example 4 38.5 32.5 255 320 240 Comparative Example 5 36.8 35.7 380 55 285 Comparative Example 6 39.1 19.2 305 38 195 According to the foregoing, Examples 1-4 of the present invention enhance the porosity and catalytic activity by activating biochar; phosphoric acid activates red mud for effective desulfurization and catalytic cracking; oil pretreatment reduces combustion byproducts; and cerium oxide promotes full oxidation and reduces CO emissions, thereby achieving high calorific value, efficient combustion, and ultra-low emissions.

[0044] In comparison example 1, the calorific value decreased by 4.7%, the burnout time increased by 44%, and the emission concentration increased by 134-126%. The unactivated biochar had low porosity and weak catalytic activity, resulting in incomplete cracking and decreased combustion efficiency. In comparison example 2, the calorific value decreased by 6.2%, the burnout time increased by 59%, and the pollutants increased by 179-183%. The catalytic support function of the biochar was lost, the reaction rate decreased, and the number of uncracking components increased. In comparison example 3, SO2 emissions increased by 600%, NO x The sulfide in the red mud was not removed by phosphoric acid activation, and a large amount of SO2 was released during combustion. The catalytic activity of the unactivated red mud was insufficient, resulting in an increase in the conversion of nitrogen oxides. In comparative example 4, SO2 increased by 967%, and the burnout time increased by 83%. The desulfurization function and cracking catalytic effect of the red mud were lost, and the sulfide was released directly, and the reaction rate was significantly reduced. In comparative example 5, the calorific value decreased by 8.5%, CO increased by 381%, and NOx increased by 171%. The high moisture content and acid value led to an increase in cracking side reactions, generating a large amount of incomplete combustion products (CO) and nitrogen oxides. In comparative example 6, CO increased by 286%, and NO x Increased by 86% Due to the lack of cerium oxide's catalytic oxidation effect, CO oxidation is incomplete; at the same time, the increase in incomplete combustion products pushes up NO x generate.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. An environmentally friendly biomass fuel, characterized in that: The invention comprises the following materials in parts by weight: 60-70 parts of sawdust, 25-35 parts of activated biochar, 15-20 parts of phosphoric acid-activated red mud, 3-5 parts of waste cooking oil, 2-4 parts of calcium lignin sulfonate, and 0.8-1.2 parts of cerium oxide; wherein the activated biochar is prepared by soaking rice husks in a ZnCl2 solution; and the phosphoric acid-activated red mud is prepared by adding dried red mud to a phosphoric acid solution.

2. The environmentally friendly biomass fuel according to claim 1, characterized in that: The preparation method of phosphoric acid-activated red mud comprises: adding dried red mud to a phosphoric acid solution, stirring at a rotation speed of 200-300 rpm and a temperature of 75-85° C. for 2-4 hours, vacuum filtering, washing the filter cake with deionized water until neutral, and drying in an oven at 100-110° C. until the moisture content is ≤5%.

3. The environmentally friendly biomass fuel according to claim 2, characterized in that: The mass concentration of the phosphoric acid aqueous solution is 5-10%; the usage ratio of the dried red mud to the phosphoric acid aqueous solution is 1:10-12.

4. The environmentally friendly biomass fuel according to claim 2, characterized in that: The red mud drying process includes drying the red mud at a temperature of 80-90° C. for 4-6 hours.

5. The environmentally friendly biomass fuel according to claim 1, characterized in that: The preparation method of the activated biochar comprises: immersing the rice husk biochar in a ZnCl2 solution, activating it at 110-120°C for 2-4 hours, and washing it with deionized water until there is no Cl2. - Under nitrogen conditions, the temperature is raised to 550-650°C at a rate of 10°C / min, kept warm for 60-70 minutes, and cooled to room temperature after the reaction is completed.

6. The environmentally friendly biomass fuel according to claim 5, characterized in that: The ZnCl2 solution is a ZnCl2 aqueous solution with a mass concentration of 10-12%, and the usage ratio of the rice husk biochar to the ZnCl2 solution is 1g:4-6mL.

7. The environmentally friendly biomass fuel according to claim 1, characterized in that: The wood chips are wood processing waste chips, including at least one of pine wood chips, fir wood chips, poplar wood chips, and fruit wood chips.

8. The environmentally friendly biomass fuel according to claim 1, characterized in that: The waste catering grease needs to be pretreated, and the steps include: filtering to remove solid impurities, heating to 75-85° C. for sedimentation and dehydration for 1-2 hours, and then centrifuging at 3000-4000 rpm for 15-20 minutes to obtain the waste catering grease.

9. The environmentally friendly biomass fuel according to claim 8, characterized in that: The waste catering oil has a water content of ≤5% and an acid value of ≤5mg KOH / g.

10. A method for preparing an environmentally friendly biomass fuel according to any one of claims 1 to 9, characterized in that the steps include: Sawdust is crushed into particles of 1-3 mm; raw materials are weighed according to the formula, activated biochar, phosphoric acid-activated red mud, and cerium oxide are stirred and mixed at a speed of 100-200 r / min for 60-80 minutes to obtain a catalyst; sawdust, waste catering oil, and calcium lignin sulfonate are then placed in a reactor and stirred at 200-250 rpm for 40-50 minutes, nitrogen is introduced to replace the air, the catalyst is added, the temperature is increased to 380-450°C at 5°C / min, and a catalytic cracking reaction is carried out at 8-12 MPa for 80-100 minutes; the reaction product is cooled to 80-100°C for gas-liquid-solid separation, and the liquid phase product is collected; The liquid phase product is refined to obtain the environmentally friendly biomass fuel.