A kind of biochar particle for fluidized bed or fixed bed green methanol fuel preparation and its preparation method and utilization method

Abstract

This invention discloses a biochar pellet for producing green methanol fuel in fluidized beds or fixed beds, and its preparation and utilization methods. First, agricultural and forestry waste is pyrolyzed and ball-milled into biochar powder. Then, sludge is introduced as the main binder, utilizing the organic colloids in the sludge as a natural binder, eliminating the need for additional inorganic or organic binders, thus achieving waste-to-waste treatment and reducing costs. This invention further introduces sawdust as an auxiliary binder and calorific value regulator. As unpyrolyzed primary biomass, sawdust compensates for the decrease in calorific value caused by the addition of sludge. Simultaneously, the thermoplastic melting of lignin in the sawdust at the high temperature of granulation can play an auxiliary binding role. Finally, by granulating biochar powder, sludge, and sawdust in a specific ratio, biochar pellets with high mechanical strength, good reactivity, and suitable calorific value are obtained, with compressive strength meeting the requirements of vigorous tumbling in fluidized beds and accumulation in fixed beds.

Description

Technical Field

[0001] This invention relates to the field of biomass energy and solid waste co-utilization technology, and more specifically, to a biochar pellet for producing green methanol fuel in a fluidized bed or fixed bed, and its preparation and utilization methods. Background Technology

[0002] With the accelerated decarbonization process in the global shipping and chemical industries, the demand for green methanol, as a carbon-neutral liquid fuel, is growing exponentially. Currently, biomass gasification syngas is one of the main technological routes for producing green methanol.

[0003] However, in the existing technology, biomass gasification to methanol faces the following bottlenecks: (1) Agricultural waste such as straw and rice husks have low density (<100kg / m³) and irregular shape. If they are directly fed into a fluidized bed gasifier, they are prone to bridging or being blown out by the gas flow, resulting in poor fluidization quality. If they are fed into a fixed bed gasifier, they are prone to excessive pressure drop in the bed or flow deviation. (2) The tar content in the crude syngas produced by direct biomass gasification is usually as high as 10~50g / m³, which seriously clogs downstream pipelines and purification equipment, increasing the purification cost before methanol synthesis. (3) Existing technologies generally use commercial binders such as bentonite (increasing ash content) or starch (increasing cost) for granulation, which is not economically viable.

[0004] Furthermore, the sludge produced by current wastewater treatment plants is enormous and contains heavy metals and pathogens, making its disposal a significant challenge. Traditional landfilling occupies land, while incineration is energy-intensive. Moreover, current technologies struggle to efficiently and economically produce green methanol fuel while simultaneously achieving the synergistic resource recovery of agricultural waste and sludge.

[0005] Therefore, there is an urgent need for a technical solution that can co-process agricultural waste and sludge to produce biochar pellets with high strength, low tar yield, and that meet the requirements for green methanol production. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned defects in the prior art and provide biochar particles for producing green methanol fuel in fluidized beds or fixed beds, as well as their preparation and utilization methods.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A method for preparing biochar pellets for producing green methanol fuel in a fluidized bed or fixed bed includes the following steps: S1. After crushing and drying agricultural and forestry waste, it is then subjected to pyrolysis and ball milling to obtain biochar powder. S2. Sludge as the main binder, sawdust as the auxiliary binder, calorific value regulator and biochar powder are mixed and stirred in a dry basis mass ratio of (5~15):(5~15):(70~90) to obtain a mixed material; S3. The mixed material is extruded and granulated under high temperature and high pressure, and then the granulated wet particles are dried at low temperature to obtain biochar particles.

[0009] The present invention also discloses a biochar particle prepared by the preparation method described above.

[0010] This invention also discloses a method for preparing green methanol using biochar particles, wherein the biochar particles are those prepared by the above-described method, or biochar particles as described above; the method includes: feeding the biochar particles as raw material into a gasifier for gasification reaction to produce crude syngas; the gasifier is a fluidized bed gasifier or a fixed bed gasifier; cooling and purifying the crude syngas and performing a water-gas shift reaction to adjust the H2 / CO ratio in the syngas to 2.0~2.1, and then using methanol as a removal agent to remove sulfides and CO2 from the crude syngas to obtain purified syngas; and reacting the purified syngas to generate green low-carbon methanol.

[0011] Based on the aforementioned deficiencies in existing technologies, the inventors propose using sludge as the primary binder and utilizing the organic colloids within the sludge as a natural binder. This eliminates the need for additional inorganic or organic binders, achieving waste treatment and reducing costs. Furthermore, the inventors have discovered that using sludge alone for granulation results in a low calorific value. Therefore, this invention further introduces sawdust as an auxiliary binder and calorific value regulator. As unpyrolyzed primary biomass, sawdust compensates for the decrease in calorific value caused by the addition of sludge. Simultaneously, the thermoplastic melting of lignin in the sawdust at the high granulation temperature serves as an auxiliary binder. Finally, by proportioning biochar powder, sludge, and sawdust in a dry weight ratio of (70~90):(5~15):(5~15) and granulating, multiple issues related to molding, strength, and calorific value are synergistically resolved.

[0012] Implementing the embodiments of the present invention will have the following beneficial effects: This invention first involves pyrolyzing and ball-milling agricultural and forestry waste to produce biochar powder. Then, sludge is introduced as the primary binder, and sawdust is added as an auxiliary binder and calorific value regulator. The mixture is then kneaded according to a specific ratio, and the uniformly mixed material is extruded into shape. Under high-temperature extrusion at 80℃~120℃ and high-pressure extrusion at 50MPa~150MPa, the lignin in the sawdust reaches its glass transition temperature, undergoing thermoplastic softening and melting. Simultaneously, the sludge contains a large amount of extracellular polymeric substances (EPS) composed of polysaccharides and proteins, possessing natural polymeric adhesive properties. During extrusion, the molten lignin and the EPS macromolecules of the sludge interpenetrate, compress, and physically cross-link between the pores and interfaces of the biochar powder particles. Upon cooling, a rigid "lignin-EPS interpenetrating network structure" is formed, thereby endowing the biochar particles with extremely high mechanical strength and compressive strength. The final product is biochar granules with high mechanical strength, good reactivity, and suitable calorific value. The bulk density of the granules is 400 kg / m³ to 700 kg / m³, and the compressive strength meets the requirements of violent tumbling in fluidized beds and stacking in fixed beds.

[0013] This invention further utilizes biochar particles to prepare green methanol. The biochar particles contain Ni and alkali metal elements derived from sludge, which catalyze the in-situ cracking of tar, significantly reducing the tar content of the syngas. The resulting hydrogen-rich syngas, after purification, meets the requirements for the synthesis of green, low-carbon methanol. The entire process can be driven by green electricity, achieving high-value utilization of waste. The entire production and gasification process of this invention is driven by green electricity. Combined with the carbon-neutral properties of biomass raw materials, the final methanol produced meets EU green fuel certification standards. Attached Figure Description

[0014] Figure 1 This is a process flow diagram of the present invention for preparing green methanol using biochar particles. Detailed Implementation

[0015] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0016] This invention discloses a method for preparing biochar pellets for producing green methanol fuel in a fluidized bed or fixed bed, comprising the following steps: S1. After crushing and drying agricultural and forestry waste, it is then subjected to pyrolysis and ball milling to obtain biochar powder.

[0017] In one specific embodiment, step S1, the crushing and drying process includes: crushing agricultural and forestry waste to 3-8mm and then drying it at a temperature of 80℃-120℃ to achieve a moisture content of ≤15%, thereby obtaining crushed and dried agricultural and forestry waste; if the moisture content is too high, the evaporation of water will consume a large amount of reaction heat, significantly reducing the pyrolysis efficiency and increasing energy consumption; at the same time, excessive water vapor will dilute the pyrolysis products, leading to an increase in the moisture content of bio-oil and affecting the quality and yield of biochar.

[0018] In one specific embodiment, in step S1, the agricultural and forestry waste is one or more of the following: rice husks, sawdust, rice straw, and corn straw.

[0019] In one specific embodiment, step S1, the pyrolysis treatment method includes: pyrolyzing the crushed and dried agricultural and forestry waste under anaerobic or hypoxic conditions, with a pyrolysis temperature of 350℃~550℃, a pyrolysis heating rate of 5℃ / min~15℃ / min, and a pyrolysis time of 30min~120min, to obtain biochar.

[0020] In one specific embodiment, step S1, the ball milling method includes: ball milling the biochar obtained after pyrolysis treatment, the ball milling speed is 200 r / min to 400 r / min, the ball milling time is 15 min, and the biochar powder with a particle size of <100 μm is obtained by sieving.

[0021] S2. Sludge as the main binder, sawdust as the auxiliary binder, calorific value regulator and biochar powder are mixed and stirred at a dry basis mass ratio of (5~15):(5~15):(70~90) to obtain a mixed material; In one specific embodiment, step S2, kneading and mixing, includes: first kneading and mixing sawdust as dry material with biochar powder, then adding sludge for a second kneading and mixing. The temperature of the first kneading and mixing is 20℃~30℃, and the time is 10min~20min. The temperature of the second kneading and mixing is 20℃~40℃, and the time is 15min~30min. The moisture content is controlled at 20%~30% to obtain the kneaded material. If the moisture content is too low, the friction of the material in the mold will be too high, which will easily lead to machine blockage and failure to form. If the moisture content is too high, the water will vaporize violently under the high temperature generated by extrusion, which will form pores or even burst inside the particles, resulting in loose particles with extremely poor strength after forming.

[0022] In one specific embodiment, the dry weight ratio of biochar powder, sludge, and sawdust in the biochar granules is 70:15:15; under this ratio, the organic matter content of the biochar granules is maximized, and the total salt content is controlled at a low level to prevent gasification slagging.

[0023] In one specific embodiment, the sludge is municipal sludge or digested sludge.

[0024] In one specific embodiment, the sludge has a moisture content of 10% to 20%, an organic matter content of 40% to 60%, and a total salt content of ≤5%; the sludge contains 400 to 500 mg / kg of nickel, 450 to 650 mg / kg of copper, and 4100 to 4500 mg / kg of zinc.

[0025] Compared to filter press sludge (total salt > 6%), the sludge used in this invention has a low total salt content (≤ 5%), which effectively avoids the problems of bed material agglomeration and slagging during fluidized bed gasification.

[0026] In one specific embodiment, the particle size of the wood chips is 60 mesh; the moisture content of the wood chips is 10%~15%.

[0027] Specifically, wood chips with a moisture content of 10% to 15% and sludge with a moisture content of 10% to 20% are mixed with biochar powder. By adding a small amount of water or balancing the moisture content on its own, the overall moisture content is controlled within the optimal range of 20% to 30% for granulation, without the need for additional high-energy drying.

[0028] S3. The mixed materials are extruded and granulated under high temperature and high pressure, and then the granulated wet particles are dried at low temperature to obtain biochar particles.

[0029] In one specific embodiment, in step S3, the extrusion granulation temperature is 80℃~120℃, and the extrusion granulation pressure is 50MPa~150MPa. Under these high temperature and high pressure conditions, the lignin component rich in wood chips softens and melts under the high temperature generated by granulation extrusion, and works synergistically with the organic colloids in the sludge to enhance the mechanical strength of the particles; at the same time, it compensates for the reduction in the overall calorific value of the particles caused by the addition of sludge.

[0030] In one specific embodiment, in step S3, the temperature of low-temperature drying is 105℃~150℃. The low-temperature drying process hardens the organic colloids in the sludge, thereby enhancing the compressive strength and wear resistance of the particles.

[0031] In one specific embodiment, in step S3, extrusion granulation can be performed using a flat die, a ring die, or a double-roller granulator.

[0032] In one specific embodiment, the biochar particles have a particle size of 2mm to 10mm, a bulk density of 400kg / m³ to 700kg / m³, a moisture content of <20%, a calorific value of 15MJ / kg to 25MJ / kg, and a compressive strength of 300N to 400N; and the biochar particles contain Ni and alkali metal elements derived from sludge.

[0033] In one specific embodiment, the biochar particles contain alkali metal elements such as potassium (K) and sodium (Na) derived from sludge, and their total mass fraction in the biochar particles is 0.1% to 1.5%.

[0034] In one specific embodiment, although the heavy metal content in the biochar particles originates from sludge, it does not affect the subsequent methanol synthesis process of the gasification products after dilution. Furthermore, after high-temperature gasification, most of the heavy metals will solidify in the bottom ash, which can be recovered later and used as a co-catalyst for methanol synthesis.

[0035] The present invention also discloses a biochar particle prepared by the preparation method described above.

[0036] This invention also discloses a method for preparing green methanol using biochar particles, wherein the biochar particles are biochar particles prepared by the above-described preparation method, or biochar particles as described above; the method includes: Biochar pellets are fed into a gasifier as raw material for gasification to produce crude syngas; the gasifier is either a fluidized bed gasifier or a fixed bed gasifier. The crude syngas is cooled, purified, and subjected to a water-gas shift reaction to adjust the H2 / CO ratio in the syngas to 2.0-2.1. Then, methanol is used as a removal agent to remove sulfides and CO2 from the crude syngas, resulting in purified syngas. Green, low-carbon methanol is produced by the reaction of purified syngas.

[0037] In one specific embodiment, when a fluidized bed gasification process is used, biochar particles are fed into a fluidized bed gasifier as raw material. The wear-resistant structure formed by the solidification of the sludge colloid mixed in the particles allows the particles to maintain their intact shape without breaking in the furnace. The gasifying agent is oxygen and water vapor, the gasification temperature is 800℃~950℃, and the pressure is 0.1~2.0MPa.

[0038] In one specific embodiment, during the gasification reaction, the Ni element and / or alkali metal element in the biochar particles act as catalysts to catalyze the gas-liquid-solid multiphase reaction in the fluidized bed, preventing bed material agglomeration and reducing tar yield.

[0039] In one specific embodiment, when a fixed-bed gasification process is used, biochar particles are fed into a fixed-bed gasifier as raw material. Taking advantage of the uniform particle size and high compressive strength of the particles, a permeable material layer with uniform porosity is constructed to avoid short-circuiting or deviating of the gasifying agent. The gasifying agent is oxygen and water vapor, the gasification temperature is 700℃~900℃, and the pressure is 0.1MPa~3.0MPa.

[0040] In one specific embodiment, the pressure of the water-gas shift reaction is 2~3 MPa, the temperature is 250~350℃, and the catalyst used is a Ni-based catalyst; at the same time, the Ni element and alkali metal element in the biochar particles can be used as co-catalysts.

[0041] In one specific embodiment, the reaction conditions are a reaction pressure of 2.4~4MPa, a temperature of 240~280℃, a space velocity of 8000~12000ml / (gcat·h), and a Cu-Zn-Al based catalyst; at the same time, Ni and / or alkali metal elements in the biochar particles serve as co-catalysts.

[0042] In one specific embodiment, the entire process is driven by green electricity: the electricity required to drive the mechanical equipment and maintain the process temperature in the biochar particle preparation method and the green methanol preparation method comes entirely or partially from renewable energy power systems such as wind power, solar photovoltaic or hydropower.

[0043] In one specific embodiment, the green and low-carbon methanol fuel produced by the present invention meets the international certification standards for green methanol in terms of its life-cycle carbon emission intensity. This method utilizes agricultural waste, sludge, and other resources, which is in line with the national strategic goals of carbon peaking and carbon neutrality.

[0044] The following are specific embodiments. Example 1 The method for preparing biochar particles in this embodiment includes the following steps: S1. Corn stalks are crushed to 3-8 mm and then dried at 100℃ to achieve a moisture content ≤15%, yielding crushed and dried corn stalks. Subsequently, they are pyrolyzed under anaerobic conditions at 500℃, a pyrolysis rate of 15℃ / min, and a pyrolysis time of 60 min to obtain biochar. The pyrolyzed biochar is then ball-milled at 300 r / min for 15 min, and sieved to obtain biochar powder with a particle size <100 μm.

[0045] S2. Anaerobic digestion sludge (actually wet sludge, adjusted based on moisture content) from a municipal wastewater treatment plant (15 kg dry weight) was used as the main binder, and pine sawdust (15 kg dry weight) was used as an auxiliary binder. These were then mixed with 70 kg dry weight of biochar powder to obtain a kneaded material. The kneading process included: first, kneading the sawdust (dry material) with the biochar powder; then, adding the sludge for a second kneading process. The first kneading temperature was 20℃, and the kneading time was 10 minutes. The second kneading temperature was 30℃, and the kneading time was 20 minutes. Water was then added to obtain a kneaded material with a moisture content of 28%. This process ensures that the extracellular polymers in the sludge fully coat the biochar powder, while the long fibers of the pine sawdust act as a reinforcing agent, preventing particle breakage.

[0046] The characteristics of the sludge (air-dried basis) are as follows: moisture content 18.1%, pH 8.41, organic matter content 54.46%, total salt content 4.36%, Ni content 450 mg / kg, copper content 527 mg / kg, and zinc content 4329 mg / kg.

[0047] The characteristics of this pine sawdust are as follows: the particle size of the pine sawdust is 60 mesh; the moisture content of the sawdust is 10%.

[0048] S3. The mixed material is fed into a ring die granulator with a compression ratio of 1:5. It is extruded and granulated under high temperature and high pressure conditions. The extrusion granulation temperature is 100℃ and the extrusion granulation pressure is 80MPa to obtain cylindrical particles of 2mm~10mm. Then, the granulated wet particles are dried in a mesh belt dryer at 105℃ using electric heat provided by photovoltaic power generation until the moisture content is <8%.

[0049] The biochar granules have a bulk density of 580 kg / m³ and a calorific value of 16.5 MJ / kg; and the biochar granules contain Ni and alkali metal elements derived from sludge.

[0050] Example 2 This embodiment uses the biochar particles obtained in Example 1 to prepare green methanol. The method includes: Biochar particles are fed into a circulating fluidized bed gasifier for gasification. The gasifying agents are oxygen and water vapor. The gasification temperature is 900℃ and the pressure is 1.0 MPa, yielding crude syngas, which contains two or more of CO, CO2, H2, and CH4. During the gasification reaction, Ni and / or alkali metal elements in the biochar particles act as catalysts to catalyze the gas-liquid-solid multiphase reaction within the fluidized bed, preventing bed material agglomeration and reducing tar yield.

[0051] The crude syngas is passed into a cooling and purification unit for cooling and purification to remove ash and carbon black impurities, resulting in purified crude syngas.

[0052] The purified crude syngas was subjected to a water-gas shift reaction at a pressure of 2 MPa and a temperature of 250 °C. A Ni-based catalyst was used, with Ni and / or alkali metal elements from the biochar particles acting as co-catalysts. The H2 / CO ratio in the syngas was adjusted to 2.1. The main reaction formula is shown in (Ⅰ). CO + H₂O → CO₂ + H₂ (Ⅰ) Subsequently, methanol was used as a removal agent to remove sulfides and CO2 from the crude syngas, resulting in purified syngas.

[0053] Methanol is synthesized from purified syngas at a reaction pressure of 2.4 MPa, a temperature of 240 °C, and a space velocity of 8000 ml / (gcat·h). A Cu-Zn-Al based catalyst is used, with Ni and / or alkali metal elements from biochar particles acting as co-catalysts. The reaction formula for preparing methanol from CO and H2 is shown in (II). CO + 2H₂ → CH₃OH (II) The crude methanol produced is transported to the methanol distillation unit for methanol distillation to obtain the final product, green low-carbon methanol.

[0054] Example 3 The only difference between this embodiment and embodiment 1 is that in step S2, the dry basis weight of the added biochar powder is 75 kg, and the amount of sludge and sawdust added is the same as in embodiment 1.

[0055] In step S3, the low-temperature drying temperature is 110℃.

[0056] Example 4 This embodiment uses the biochar particles obtained in Example 3 to prepare green methanol. The method is the same as in Example 2, except that the biochar particles are fed into an updraft fixed-bed gasifier as raw material to produce crude syngas. The gasifying agent is oxygen and water vapor, the gasification temperature is 800℃, and the pressure is 1.0MPa.

[0057] Example 5 The process parameters in this embodiment are completely identical to those in Embodiment 1, the difference being in energy management: The power supply lines for the raw material crusher, ball mill, granulator, and gasifier auxiliary systems (such as oxygen pumps and circulating pumps) are all connected to the direct wind power supply system.

[0058] According to LCA calculations, since the raw materials used are waste (biomass + sludge) and the energy input is zero-carbon electricity, the carbon emission intensity of the methanol produced in this embodiment fully meets the EU E-Fuel and the International Maritime Organization (IMO) certification standards for green methanol.

[0059] Comparative Example 1 The only difference between this comparative example and Example 1 is that in step S2, the dry basis mass ratio of sludge, sawdust, and biochar powder is 20:10:70.

[0060] Comparative Example 2 The only difference between this comparative example and Example 1 is that in step S2, the dry basis mass ratio of sludge, sawdust, and biochar powder is 10:20:70.

[0061] Comparative Example 3 The only difference between this comparative example and Example 1 is that in step S2, the dry weight ratio of sludge to biochar powder is 30:70.

[0062] Comparative Example 4-5 The only difference between this comparative example and Example 1 is that the extrusion granulation temperatures are 70°C and 150°C, respectively.

[0063] Table 1

[0064] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing biochar pellets for producing green methanol fuel in a fluidized bed or fixed bed, characterized in that, Includes the following steps: S1. After crushing and drying agricultural and forestry waste, it is then subjected to pyrolysis and ball milling to obtain biochar powder. S2. Sludge as the main binder, sawdust as the auxiliary binder, calorific value regulator and biochar powder are mixed and stirred in a dry basis mass ratio of (5~15):(5~15):(70~90) to obtain a mixed material; S3. The mixed material is extruded and granulated under high temperature and high pressure, and then the granulated wet particles are dried at low temperature to obtain biochar particles.

2. The method for preparing biochar pellets for producing green methanol fuel in a fluidized bed or fixed bed according to claim 1, characterized in that, In step S1, the crushing and drying method includes: crushing agricultural and forestry waste to 3-8mm and then drying it at a temperature of 80℃-120℃ to achieve a moisture content of ≤15%, thereby obtaining crushed and dried agricultural and forestry waste; the agricultural and forestry waste is one or more of rice husks, sawdust, rice straw, and corn straw. The pyrolysis treatment method includes: pyrolyzing crushed and dried agricultural and forestry waste under anaerobic or hypoxic conditions, with a pyrolysis temperature of 350℃~550℃, a pyrolysis heating rate of 5~15℃ / min, and a pyrolysis time of 30~120min to obtain biochar. The ball milling method includes: ball milling the biochar obtained after pyrolysis treatment at a speed of 200 r / min to 400 r / min for 15 min, and then sieving to obtain biochar powder with a particle size of <100 μm.

3. The method for preparing biochar pellets for producing green methanol fuel in a fluidized bed or fixed bed according to claim 1, characterized in that, In step S2, the kneading and stirring includes: kneading and stirring the sawdust and biochar powder once, then adding the sludge for a second kneading and stirring. The temperature of the first kneading and stirring is 20℃~30℃, and the time of the first kneading and stirring is 10min~20min. The temperature of the second kneading and stirring is 20℃~40℃, and the time of the second kneading and stirring is 15min~30min. The moisture content is controlled at 20%~30% to obtain the kneaded material. In the biochar granules, the dry basis mass ratio of biochar powder, sludge and sawdust is 70:15:

15.

4. The method for preparing biochar pellets for producing green methanol fuel in a fluidized bed or fixed bed according to claim 1, characterized in that, The sludge is municipal sludge or digested sludge; The sludge has a moisture content of 10% to 20%, an organic matter content of 40% to 60%, and a total salt content of ≤5%. The sludge contains 400-500 mg / kg of nickel, 450-650 mg / kg of copper, and 4100-4500 mg / kg of zinc.

5. The method for preparing biochar pellets for producing green methanol fuel in a fluidized bed or fixed bed according to claim 1, characterized in that, The wood chips have a particle size of 60 mesh and a moisture content of 10% to 15%.

6. The method for preparing biochar pellets for producing green methanol fuel in a fluidized bed or fixed bed according to claim 1, characterized in that, In step S3, the temperature of the extrusion granulation molding is 80℃~120℃, and the pressure of the extrusion granulation molding is 50MPa~150MPa. The temperature for the low-temperature drying is 105℃~150℃.

7. The method for preparing biochar pellets for producing green methanol fuel in a fluidized bed or fixed bed according to claim 1, characterized in that, The biochar particles have a particle size of 2mm to 10mm, a bulk density of 400kg / m³ to 700kg / m³, a moisture content of <20%, a calorific value of 15MJ / kg to 25MJ / kg, and a compressive strength of 300N to 400N; and the biochar particles contain Ni and alkali metal elements derived from the sludge. The electricity required for the preparation method comes from renewable energy sources.

8. Biochar particles prepared by the preparation method according to any one of claims 1-7.

9. A method for preparing green methanol using biochar particles, characterized in that, The biochar particles are biochar particles prepared by any one of the preparation methods described in claims 1-7, or biochar particles as described in claim 8; The method includes: The biochar particles are fed into a gasifier as raw material for gasification to produce crude syngas; the gasifier is a fluidized bed gasifier or a fixed bed gasifier. The crude syngas is cooled, purified, and subjected to a water-gas shift reaction to adjust the H2 / CO ratio in the syngas to 2.0-2.

1. Then, methanol is used as a removal agent to remove sulfides and CO2 from the crude syngas, resulting in purified syngas. The purified syngas reacts to produce green, low-carbon methanol.

10. The method according to claim 9, characterized in that, When using fluidized bed gasification, the gasifying agent is oxygen and water vapor, the gasification temperature is 800℃~950℃, and the pressure is 0.1MPa~2.0MPa. When a fixed-bed gasification process is used, the gasifying agent is oxygen and water vapor, the gasification temperature is 700℃~900℃, and the pressure is 0.1MPa~3.0MPa; In the gasification reaction, the Ni element and / or alkali metal element in the biochar particles serve as a catalyst. The pressure of the water-gas shift reaction is 2~3MPa, the temperature is 250~350℃, and the catalyst used is a Ni-based catalyst; at the same time, the Ni element and / or alkali metal element in the biochar particles serve as a co-catalyst. The reaction conditions are a reaction pressure of 2.4~4MPa, a temperature of 240~280℃, a space velocity of 8000~12000ml / (gcat·h), and a Cu-Zn-Al based catalyst; meanwhile, the Ni element and / or alkali metal element in the biochar particles serve as a co-catalyst. The electricity required for the method of preparing green methanol comes from renewable energy sources.

Images