A method and system for producing a biomass fuel for metallurgical use

Abstract

The application discloses a method and system for preparing a biomass fuel for metallurgy. The biomass fuel prepared by sequentially drying, pyrolyzing, washing, digesting, distilling, balling and carbonizing the biomass has the characteristics of low volatile content (<10 wt%), low combustion rate, low alkali metal, high energy density and high strength, has the potential to replace fossil coke on a large scale, can greatly reduce the dependence on fossil energy and greatly reduce carbon emission. In addition, the biomass fuel prepared by the application also contains a large amount of calcium ferrite, can greatly improve the quality of metallurgical products, and significantly reduces NOx emission, and is a clean energy friendly to the environment and directly used in the steel process.

Description

Technical Field

[0001] This invention relates to fuel production technology, specifically to a method and system for preparing biomass fuel for metallurgical use, belonging to the field of metallurgical fuel production technology. Background Technology

[0002] The steel industry is an energy-intensive sector, accounting for approximately 15% of the nation's total carbon emissions, second only to the thermal power industry, making it the largest carbon emitter among the 31 categories of manufacturing. The steel industry currently primarily uses fossil fuels, especially coal, which is widely applied in various processes such as coking, sintering, blast furnaces, and steelmaking.

[0003] Biomass energy is a clean energy source and the only renewable carbon source. It is widely available and has enormous reserves; the world produces 170 billion tons of dry biomass annually, but only 1.3 billion tons are currently utilized. Biomass fuels are generally low in sulfur (S) and nitrogen (N), which can reduce nitrogen and sulfur pollutants at the source. More importantly, biomass fuel is currently considered a "zero-carbon" fuel because the CO2 released during its combustion is equal to the CO2 absorbed during its growth cycle. From the perspective of the entire biomass life cycle, it can be considered to release no additional CO2 into the environment, thus being considered an environmentally friendly energy source with "zero CO2 emissions."

[0004] Applying biomass to the steel industry to replace traditional fossil fuels can improve the utilization efficiency of biomass fuels and reduce carbon emissions from the steel industry at the source. However, due to problems such as high volatile matter content, high alkali metal content, low energy density, low strength, and excessively fast combustion rate, biomass generally cannot be used directly in steel production. Biomass cannot be directly used in steel production, mainly due to several drawbacks in the steelmaking process: ① High volatile matter content: Biomass generally has a high volatile matter content, which easily precipitates in the high-temperature environment of the steelmaking process, leading to an increase in CO concentration in the flue gas. Furthermore, the volatile matter often contains a lot of tar, which easily condenses in subsequent pipelines, causing equipment corrosion and adhesion. Therefore, the volatile matter content of fuel entering the furnace in metallurgical processes generally needs to be below 10%. ② High alkali metal content: Fertilizers, such as potash fertilizer, are used during the growth of biomass, resulting in a high alkali metal content. ③ Low energy density: Due to its low density and loose texture, biomass is difficult to mix evenly with metallurgical raw materials, easily causing segregation during mixing. ④ Low strength: Biomass pyrolysis char has a porous structure, is brittle, and has low compressive strength. ⑤ Excessively fast combustion rate: Due to the high volatile matter content and well-developed pore structure of biomass, the combustion rate is too fast, making it difficult to meet the sustained high-temperature requirements of the smelting process. Therefore, biomass must undergo pretreatment before entering the metallurgical process.

[0005] CN110699142B discloses a biomass pretreatment method that involves mixing and briquetting tailings slag with biomass, followed by low-temperature and high-temperature carbonization. This method may have some effect on removing volatile matter from biomass. However, it suffers from difficulties in mixing biomass powder and tailings slag due to their large density difference. Furthermore, the biomass after pyrolysis has large pores, resulting in a relatively fast reaction rate. In addition, it does not address the removal of alkali metals from biomass or the comprehensive utilization of the bio-oil and pyrolysis gas produced by the reaction, leading to a relatively simple product and low resource utilization. Summary of the Invention

[0006] In view of the problems in existing technologies, biomass cannot be directly used in steel production due to its high volatile matter content, high alkali metal content, low energy density, low strength, and excessively fast combustion rate. The purpose of this invention is to provide a method and system for preparing biomass fuel for metallurgy. The biomass fuel prepared by this invention has the characteristics of low volatile matter content, low alkali metal content, high strength, low combustion rate, and high energy density. Its overall properties are close to those of coke, and it has the potential to replace coke in a large proportion. It is a clean energy source that can be directly used in steelmaking processes.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0008] According to a first embodiment of the present invention, a method for preparing biomass fuel for metallurgical use is provided:

[0009] A method for preparing biomass fuel for metallurgical use, the method comprising the following steps:

[0010] 1) The biomass is dried and crushed to obtain biomass dry powder.

[0011] 2) The biomass dry powder is pyrolyzed to obtain biochar, pyrolysis gas and bio-oil.

[0012] 3) The biochar is washed with water to obtain washed biochar and saline wastewater.

[0013] 4) Add quicklime to the washed charcoal and mix well to obtain digested feed.

[0014] 5) The bio-oil obtained in step 2) is fractionated to obtain light water, light oil, and heavy oil. Then, the digestate is mixed with the light oil and distilled to obtain distilled char and light bio-oil.

[0015] 6) Add heavy oil and iron-containing solid waste to distilled charcoal for mixing and pelletizing to obtain carbon-iron raw pellets.

[0016] 7) Carbonize the iron pellets to obtain biomass fuel.

[0017] Preferably, the method further includes:

[0018] 8) The pyrolysis gas obtained in step 2) is burned as fuel to obtain high-temperature flue gas, which is then recycled for the pyrolysis treatment of biomass dry powder and / or for the carbonization treatment of carbon-iron pig pellets. The medium-temperature flue gas emitted during the pyrolysis and / or carbonization treatment is recycled for the drying treatment of biomass and / or for subsequent concentration and desalination treatment.

[0019] Preferably, 9) the saline wastewater is recycled for the washing treatment of biochar to obtain high-salt wastewater, which is then concentrated and desalinated to obtain mixed salt and condensate. Preferably, the condensate and light water are recycled as the washing water for biochar.

[0020] Preferably, in step 1), the drying and crushing process specifically involves drying the biomass at 90-160℃ for 0.3-3 hours (preferably at 105-140℃ for 0.5-2 hours), and then crushing the dried biomass to a particle size of less than 1.5 mm (preferably less than 1 mm) to obtain dried biomass powder.

[0021] Preferably, in step 1), the moisture content of the biomass dry powder is not higher than 5 wt%, and more preferably 0.5-3 wt%.

[0022] Preferably, in step 2), the pyrolysis treatment specifically involves pyrolyzing the biomass dry powder at 600-900℃ for 0.1-2 hours (preferably at 700-800℃ for 0.3-1 hours) in an oxygen-isolated environment. The gas produced during pyrolysis is pyrolysis gas, the liquid produced is bio-oil, and the remaining solid is biochar.

[0023] Preferably, in step 2), the volatile matter content in the biochar is less than 10%, preferably 3-8%.

[0024] Preferably, in step 3), the solid-liquid mass ratio of the water washing treatment is 1:2-8, more preferably 1:3-6. The water washing time is not less than 10 minutes, preferably 30-60 minutes.

[0025] Preferably, in step 4), the water-washed charcoal has a moisture content of less than 30 wt%, preferably 10-20 wt%. The amount of quicklime added is 3-12% of the total mass of the water-washed charcoal, preferably 5-10%.

[0026] Preferably, in step 5), the fractionation process specifically involves: first, fractionating the bio-oil at a temperature of 100-150°C until the bio-oil mass hardly changes, to obtain light water and oil; then, fractionating the oil at a temperature of 250-350°C until the oil mass hardly changes, to obtain light oil and heavy oil.

[0027] It should be noted that in this invention, the fractionation time is related to the total amount of material being fractionated; the larger the total amount of material, the longer the fractionation time will be. Generally, the condition for the completion of a single fractionation is that the mass of the material being fractionated has reached a basically constant weight, that is, its mass no longer changes.

[0028] Preferably, in step 5), the distillation process specifically involves distilling the mixture of digested feed and light oil at a temperature of 200-300°C for 20-60 minutes (preferably at a temperature of 240-280°C for 30-50 minutes) to obtain distilled charcoal and light bio-oil.

[0029] Preferably, in step 5), the mass ratio of the digested feed to the light oil is 1:1-10, more preferably 1:2-7.

[0030] Preferably, in step 6), the amount of heavy oil added is 8-20% of the total mass of the distilled charcoal, and more preferably 10-15%.

[0031] In step 6), the amount of iron-containing solid waste added is such that the molar ratio of iron-containing compounds to quicklime in the mixture is 0.5-2:1, preferably 0.8-1.5:1.

[0032] Preferably, in step 6), the pelletizing process is extrusion pelletizing, and the extrusion pelletizing pressure is not less than 10 MPa, preferably 12-20 MPa. The extrusion pelletizing time is 30-120 s, preferably 50-90 s.

[0033] Preferably, in step 6), the particle size of the carbon iron pellets is 3-12 mm, more preferably 4-9 mm.

[0034] Preferably, in step 7), the carbonization process specifically involves carbonizing the carbon-iron pig pellets at a temperature of 500-900℃ for 10-90 minutes (preferably at a temperature of 600-850℃ for 20-60 minutes) to obtain biomass fuel.

[0035] Preferably, in step 8), the pyrolysis gas is used as fuel in the hot blast stove and is burned with combustion air to obtain high-temperature flue gas at 800-1000°C (preferably 850-950°C).

[0036] Preferably, in step 8), the temperature of the medium-temperature flue gas is 300-500℃, more preferably 350-450℃.

[0037] Preferably, in step 8), the water-containing hot gas generated during the drying process is condensed to obtain dried condensate, and the dried condensate is used for the water washing treatment of biochar.

[0038] Preferably, in step 9), the concentration factor of the high-salt wastewater is 2-8 times, and more preferably 3-6 times.

[0039] Preferably, both the pyrolysis treatment and the carbonization treatment are indirect heat exchangers.

[0040] According to a second embodiment of the present invention, a system for preparing biomass fuel for metallurgical use is provided:

[0041] A system for preparing biomass fuel for metallurgical use, or a system for the method described in the first embodiment, comprises a drying unit, a crushing unit, a pyrolysis unit, a water washing and filtration unit, a mixing and digestion unit, a distillation unit, a mixing and pelletizing unit, and a carbonization unit. The drying unit, crushing unit, pyrolysis unit, water washing and filtration unit, mixing and digestion unit, distillation unit, mixing and pelletizing unit, and carbonization unit are arranged in series. Both the pyrolysis unit and the carbonization unit are indirect heat exchangers.

[0042] Preferably, the system also includes a hot blast stove. The hot blast stove's hot blast outlet is connected to the hot blast inlets of the pyrolysis unit and the carbonization unit via hot blast delivery pipes. The hot blast outlets of the pyrolysis unit and the carbonization unit are connected to the hot blast inlet of the drying unit via hot blast delivery pipes. The drying unit's air outlet is connected to a chimney via an exhaust pipe.

[0043] Preferably, the pyrolysis gas outlet of the pyrolysis unit is connected to the fuel inlet of the hot blast furnace via a pyrolysis gas delivery pipeline. The oil outlet of the distillation unit is connected to the fuel inlet of the hot blast furnace via an oil delivery pipeline. Preferably, a pyrolysis gas external bypass pipeline is also connected to the pyrolysis gas delivery pipeline.

[0044] Preferably, the system also includes a fractionation unit. The oil outlet of the pyrolysis unit is connected to the feed inlet of the fractionation unit via an oil pipeline. The light water outlet of the fractionation unit is connected to the water inlet of the water washing and filter press unit via a water pipeline. The light oil outlet of the fractionation unit is connected to the feed inlet of the distillation unit via an oil pipeline. The heavy oil outlet of the fractionation unit is connected to the feed inlet of the mixing and pelletizing unit via an oil pipeline.

[0045] Preferably, the system also includes a salt concentration and separation device. The filtrate outlet of the water washing filter press is connected to the feed inlet of the salt concentration and separation device via a water supply pipe. Preferably, the filtrate outlet of the water washing filter press is also connected to the water inlet of the water washing filter press via a circulating water supply pipe.

[0046] Preferably, the system also includes a condenser. The steam outlets of the drying unit and the salt concentration unit are both connected to the steam inlet of the condenser via steam pipelines. The water outlet of the condenser is connected to the water inlet of the water washing filter press via a water pipeline.

[0047] This invention addresses the problems of existing biomass, which are unsuitable for direct use in steel production due to high volatile matter, high alkali metal content, low energy density, low strength, and excessively fast combustion rate. Furthermore, existing technologies only perform simple volatile matter removal on biomass, resulting in large biomass porosity, a relatively fast reaction rate, lack of alkali metal removal, and insufficient utilization of the resulting bio-oil and pyrolysis gas, leading to limited product variety and low resource utilization. This invention proposes a method for preparing biomass fuel from biomass. By employing processes such as drying, pyrolysis, washing, distillation, molding, and carbonization, the method removes volatile matter and alkali metals from biomass, increases its energy density, and reduces its reaction rate. Simultaneously, it achieves a complete system of self-heating and material balance using biomass, minimizing or eliminating the need for external energy and raw materials, thus reducing production costs. In addition to obtaining low-nitrogen biomass fuel for metallurgical production, it also simultaneously produces light bio-oil, pyrolysis gas, and K / Na salts as byproducts, significantly enhancing the utilization value of biomass.

[0048] In this invention, the biomass includes crops, crop waste, wood, and wood waste, such as straw (excluding grains and fruits), lignocellulose from trees, by-products from agricultural and forestry production, and agricultural and forestry waste. Generally, biomass typically has a high moisture content, ranging from 10 to 40 wt%. Direct pyrolysis would result in moisture entering the pyrolysis gas, reducing its quality. Therefore, this invention first dries the biomass to reduce its moisture content to below 10%. The heat source for drying comes from the high-temperature flue gas used as the medium-temperature flue gas after pyrolysis. The dried, moisture-containing flue gas is condensed to obtain condensate and low-temperature flue gas. Since the low-temperature flue gas contains no pollutants, it can be directly emitted.

[0049] In this invention, before pyrolyzing biomass, the dried biomass needs to be crushed into dry biomass powder with a particle size of 1.5 mm (preferably less than 1 mm). The dry biomass powder is then placed in a pyrolysis device for oxygen-free pyrolysis. The pyrolysis temperature is generally 600-900℃ (preferably 700-800℃), and the pyrolysis time is generally 0.1-2 h (preferably 0.5-3-1 h). Under these conditions, most of the volatile matter in the biomass can be removed, reducing the volatile matter content in the residue to less than 10%. (Further increasing the temperature and extending the time beyond this point will increase energy consumption and reduce production efficiency, while not significantly aiding in further volatile matter removal). The pyrolysis products include biochar (pyrolysis char), pyrolysis gas, and bio-oil (pyrolysis oil). The yield of thermal biochar is generally around 20-40 wt%, the yield of pyrolysis gas is generally around 50-70 wt%, and the yield of biomass tar is generally around 10-30 wt%. Pyrolysis equipment is generally a type of indirect heat exchanger, with the heat source coming from the high-temperature flue gas generated by the subsequent combustion of pyrolysis gas. The high-temperature flue gas exchanges heat with the material through an indirect heat exchange process, which can form high-calorific-value pyrolysis gas and high-quality pyrolysis char.

[0050] In this invention, the bio-oil obtained through pyrolysis is a high-molecular-weight compound containing polycyclic aromatic hydrocarbons and hundreds of different organic compounds. Based on their molecular weight, these different types of organic compounds can be divided into heavy and light fractions. The heavy fraction typically contains multiple benzene rings, has a large molecular weight, and a high boiling point, resulting in high viscosity and making direct combustion difficult. The light fraction is typically straight-chain hydrocarbons or small-molecule hydrocarbons containing only one or two benzene rings, with a low boiling point and better fluidity and combustibility. Furthermore, the bio-oil also contains a significant amount of water, primarily generated from hydrogen- and oxygen-containing groups such as hydroxyl and hydrogen groups in the biomass during the condensation reaction. Therefore, by utilizing the different boiling points of the components, bio-oil is fractionated at 100~150℃ (preferably 105~130℃) and 250~350℃ (preferably 280~320℃) to separate light water, light oil and heavy oil. The light water can be used as washing water, while the light oil and heavy oil are consumed in subsequent distillation and pelletizing processes to achieve full resource utilization of bio-oil.

[0051] In this invention, the main components of the pyrolysis gas are CO, H2, CH4, CO2 and other hydrocarbons, with a calorific value of approximately 12~16 MJ / Nm³. 3The temperature is slightly lower than that of coke oven gas. Because biomass is rich in oxygen, the CO2 content in the pyrolysis gas is relatively high, generally 30-50%, and the CO content is 30-40%. Biomass pyrolysis gas is an important product of biomass pyrolysis, carrying most of the chemical energy of the biomass. Therefore, a hot blast stove is set up specifically for incinerating the pyrolysis gas, generating high-temperature flue gas at approximately 800-1000℃ (preferably 850-950℃). This high-temperature flue gas serves as the heat source for various processes in the entire production system (e.g., pyrolysis and carbonization processes; both pyrolysis and carbonization use indirect heat exchange, and the high-temperature flue gas is cooled to 300-500℃ after pyrolysis or carbonization, becoming medium-temperature flue gas, which can provide heat for drying and evaporation concentration for salt extraction, forming a tiered utilization of waste heat and improving thermal energy utilization efficiency). After heat balance calculations, the generated pyrolysis gas, after partially supplying the hot blast stove to obtain high-temperature flue gas, still has a surplus of pyrolysis gas, accounting for approximately 30-50% of the total. Therefore, this surplus pyrolysis gas can be used as gas for other metallurgical processes, such as fuel for sintering ignition furnaces and pelletizing central burners, replacing traditional natural gas or coke oven gas as a gaseous fuel. In other words, through the recycling of pyrolysis gas, the system achieves self-heating energy balance, significantly reducing fossil fuel consumption and greatly reducing carbon emissions.

[0052] In this invention, biochar is a high-carbon fuel with well-developed porosity. After pyrolysis, the volatile matter content of biochar is reduced to below 10 wt% (e.g., 3-8 wt%), initially meeting the requirements for volatile matter content in metallurgical fuels. Therefore, the next step is to wash it with water to remove alkali metals. Existing research shows that the proportion of soluble alkali metals in biochar reaches 70-80% (based on the total alkali metal content), and most of the alkali metals in biomass can be removed by washing. Therefore, biochar is washed with water (e.g., light water from fractionation, condensate from the system, or fresh water) to remove soluble alkali metals from the biochar. During the washing process, the saline wastewater obtained by pressure filtration after washing can be recycled to participate in the washing of biochar to increase the salt content in the saline wastewater, thereby obtaining high-concentration, high-salt wastewater. Finally, the high-salt wastewater is evaporated and concentrated to extract salt, which can obtain mixed salts containing K / Na. The condensate obtained from evaporation can be used as circulating water for washing. When the light water and condensate are insufficient, fresh water can be added to meet the washing requirements.

[0053] In this invention, the moisture content of the washed char after water washing and pressure filtration is generally less than 30 wt% (e.g., 10-30 wt%). If it is dried again, it will consume additional energy. By adding a certain amount of quicklime powder (e.g., 3-12% of the total mass of the washed char, preferably 5-10%) to the washed char, the addition of quicklime can, on the one hand, react with the moisture in the washed char to reduce the moisture content to less than 10%; on the other hand, the reaction of quicklime with water will generate an emulsion, which is a viscous substance and can act as a binder in the subsequent extrusion molding stage; in addition, the molecules of quicklime and Ca(OH)2 emulsion are relatively fine and can enter the pores of the pyrolytic char, sealing and filling the pores, reducing the porosity of the biochar, and reducing the reaction rate of biomass.

[0054] In this invention, the light oil fraction produced by bio-oil fractionation has a certain viscosity and fluidity, allowing for good mixing and wetting with biochar. Therefore, the light oil is uniformly mixed with digested biochar (i.e., digestate) and then distilled at a temperature of 200-300℃ (preferably 240-280℃) for 20-60 min (preferably 30-50 min). The solid-liquid mass ratio of the digestate to the light oil fraction is 1:1-10 (preferably 1:2-7). After distillation, the relatively large molecular weight fractions of the light oil undergo condensation reactions, adhering to the biochar. Some large molecular weight oils act as binders, wetting the pores of the biochar and sealing CaO / Ca(OH)2 molecules within the pores, reducing the specific surface area and reactivity of the char. The light oil is then fractionated again, further lightening the composition. The resulting light bio-oil has good combustibility and can be directly consumed internally as a light biomass oilseed for direct combustion.

[0055] In this invention, heavy oil and iron-containing solid waste are added to distilled charcoal for mixing and pelletizing. The heavy oil fraction produced by bio-oil fractionation has poor flowability and good binding properties, making it an excellent binder for the distilled charcoal during the pelletizing process. The addition ratio of heavy oil is 8-20% (preferably 10-15%, based on the total mass of the distilled charcoal). Adding too little heavy oil will not provide sufficient binding, preventing the distilled charcoal from being pelletized; while adding too much will cause the tar to volatilize again during subsequent carbonization, creating secondary pores in the distilled charcoal, increasing its specific surface area and combustion characteristics, which contradicts the objective of this invention. The iron-containing solid waste refers to various iron-containing dust ash from steel plants, such as sintering environment dust, sintering machine head washing ash, and iron oxide scale. This type of solid waste generally contains more than 40 wt% iron, with K / Na < 1 wt% and Zn < 0.5 wt%. The purpose of adding distilled char to iron-containing solid waste for mixing is twofold: ① Due to the rapid combustion rate of biomass, the addition of non-combustible ash components reduces the relative content of carbon elements in the biomass, thereby slowing down the reaction rate of carbon elements; ② Because the quicklime added in the early stage contains CaO components, it can react with Fe2O3 in the iron-containing solid waste at high temperatures to form calcium ferrite. Experiments have shown that calcium ferrite is a very beneficial substance in the metallurgical process, which can inhibit the formation of NOx and help improve the strength of sintered ore. The addition ratio of iron-containing solid waste is determined based on the amount of quicklime added, that is, the amount of iron-containing solid waste added should be such that the molar ratio of iron compounds to quicklime in the pelletizing mixture is 0.5-2:1 (preferably 0.8-1.5:1).

[0056] In this invention, a mixture of distilled charcoal, heavy oil, and iron-containing solid waste is pelletized, typically by extrusion pelletizing. The extrusion pressure is not less than 10 MPa (preferably 10-20 MPa), and the holding time for extrusion pelletizing is 30-120 s (preferably 60-90 s). The resulting carbon-iron pig pellets have a particle size of 3-12 mm (preferably 4-9 mm). The purpose of extrusion pelletizing is to physically remove the pores within the biochar, reduce its volume, and give it a specific shape. The carbon-iron pig pellets with a specific shape are then carbonized, specifically by carbonizing them at 500-900℃ for 10-90 min (preferably at 600-850℃ for 20-60 min) to obtain biomass fuel. The overall performance of the obtained biomass fuel is significantly improved, closely resembling the parameters and performance of coal coke, and it has the potential to replace coke on a large scale, making it a promising clean energy source.

[0057] In this invention, the biomass fuel preparation process can essentially achieve a self-balance between matter and energy. Besides biomass raw materials, the only externally added raw materials are quicklime powder and iron-containing solid waste. Quicklime powder is a flux required in the metallurgical process itself; adding quicklime in this process reduces the amount needed in subsequent sintering and ironmaking processes. Essentially, it simply adds quicklime from later stages to the biomass fuel preparation process, without increasing the total amount added throughout the production cycle. Iron-containing solid waste is waste from steel production, representing a process of turning waste into treasure. It also co-processes some steel plant solid waste during the production of metallurgical biomass fuel. Energy balance primarily comes from the hot flue gas generated by pyrolysis gas combustion; aside from a small amount of electricity required for equipment operation, virtually no external energy is needed.

[0058] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0059] 1. The biomass fuel prepared by the biomass fuel preparation method of the present invention basically meets the requirements of metallurgical processes for fuel. It has the characteristics of low volatile matter (<10wt%), low combustion rate, low alkali metal, high energy density and high strength. It has the potential to replace fossil coke on a large scale, which can greatly reduce dependence on fossil energy and significantly reduce carbon emissions.

[0060] 2: The biomass fuel prepared by this invention contains a large amount of calcium ferrite, which can significantly improve the quality of metallurgical products and at the same time significantly reduce NOx emissions, making it environmentally friendly.

[0061] 3: The process system of the method described in this invention can basically achieve the balance of materials and energy within the system, requiring little or no additional materials and energy, resulting in low production costs and advantages for large-scale promotion and application.

[0062] 4. The process and system of this invention are simple and easy to operate. The products obtained include external pyrolysis gas, K / Na mixed salt, light biomass oil, bio-coal, etc., and multiple products can be produced simultaneously, which has good economic and environmental benefits. Attached Figure Description

[0063] Figure 1 This is a simplified flowchart of the method described in this invention.

[0064] Figure 2 This is a schematic diagram of the overall process of the method described in this invention.

[0065] Figure 3 This is a schematic diagram of the overall structure of the system described in this invention.

[0066] Figure reference numerals: 1: Drying device; 2: Crushing device; 3: Pyrolysis device; 4: Water washing and filtration device; 5: Mixing and digestion device; 6: Distillation device; 7: Mixing and pelletizing device; 8: Carbonization device; 9: Hot air furnace; 10: Fractionation device; 11: Concentration and salt separation device; 12: Condensation device. Detailed Implementation

[0067] The technical solution of the present invention will be illustrated below with examples. The scope of protection sought by the present invention includes, but is not limited to, the following embodiments.

[0068] A system for preparing biomass fuel for metallurgical use includes a drying unit 1, a crushing unit 2, a pyrolysis unit 3, a water washing and filter press unit 4, a mixing and digestion unit 5, a distillation unit 6, a mixing and pelletizing unit 7, and a carbonization unit 8. The drying unit 1, crushing unit 2, pyrolysis unit 3, water washing and filter press unit 4, mixing and digestion unit 5, distillation unit 6, mixing and pelletizing unit 7, and carbonization unit 8 are arranged in series. Both the pyrolysis unit 3 and the carbonization unit 8 are indirect heat exchangers.

[0069] Preferably, the system also includes a hot blast stove 9. The hot air outlet of the hot blast stove 9 is connected to the hot air inlets of the pyrolysis unit 3 and the carbonization unit 8 via hot air delivery pipes. The hot air outlets of the pyrolysis unit 3 and the carbonization unit 8 are connected to the hot air inlet of the drying unit 1 via hot air delivery pipes. The air outlet of the drying unit 1 is connected to the chimney via an exhaust pipe.

[0070] Preferably, the pyrolysis gas outlet of the pyrolysis unit 3 is connected to the fuel inlet of the hot blast furnace 9 via a pyrolysis gas delivery pipeline. The oil outlet of the distillation unit 6 is connected to the fuel inlet of the hot blast furnace 9 via an oil delivery pipeline. Preferably, a pyrolysis gas external bypass pipeline is also connected to the pyrolysis gas delivery pipeline.

[0071] Preferably, the system also includes a fractionation unit 10. The oil outlet of the pyrolysis unit 3 is connected to the feed inlet of the fractionation unit 10 via an oil pipeline. The light water outlet of the fractionation unit 10 is connected to the water inlet of the water washing and filter press unit 4 via a water pipeline. The light oil outlet of the fractionation unit 10 is connected to the feed inlet of the distillation unit 6 via an oil pipeline. The heavy oil outlet of the fractionation unit 10 is connected to the feed inlet of the mixing and pelletizing unit 7 via an oil pipeline.

[0072] Preferably, the system also includes a salt concentration and separation device 11. The filtrate outlet of the water washing filter press 4 is connected to the feed inlet of the salt concentration and separation device 11 via a water supply pipe. Preferably, the filtrate outlet of the water washing filter press 4 is also connected to the water inlet of the water washing filter press 4 via a circulating water supply pipe.

[0073] Preferably, the system also includes a condenser 12. The steam outlets of the drying device 1 and the salt concentration and separation device 11 are both connected to the steam inlet of the condenser 12 via steam pipelines. The water outlet of the condenser 12 is connected to the water inlet of the water washing filter press 4 via a water pipeline.

[0074] Example 1

[0075] like Figure 3 As shown, a system for preparing biomass fuel for metallurgical use includes a drying unit 1, a crushing unit 2, a pyrolysis unit 3, a water washing and filter press unit 4, a mixing and digestion unit 5, a distillation unit 6, a mixing and pelletizing unit 7, and a carbonization unit 8. The drying unit 1, crushing unit 2, pyrolysis unit 3, water washing and filter press unit 4, mixing and digestion unit 5, distillation unit 6, mixing and pelletizing unit 7, and carbonization unit 8 are arranged in series. Both the pyrolysis unit 3 and the carbonization unit 8 are indirect heat exchangers.

[0076] Example 2

[0077] The system repeats Example 1, except that it also includes a hot air furnace 9. The hot air outlet of the hot air furnace 9 is connected to the hot air inlets of the pyrolysis unit 3 and the carbonization unit 8 via hot air delivery pipes. The hot air outlets of the pyrolysis unit 3 and the carbonization unit 8 are connected to the hot air inlet of the drying unit 1 via hot air delivery pipes. The air outlet of the drying unit 1 is connected to a chimney via an exhaust pipe.

[0078] Example 3

[0079] Example 2 is repeated, except that the pyrolysis gas outlet of the pyrolysis unit 3 is connected to the fuel inlet of the hot blast furnace 9 via a pyrolysis gas delivery pipeline. The oil outlet of the distillation unit 6 is connected to the fuel inlet of the hot blast furnace 9 via an oil delivery pipeline. Preferably, a pyrolysis gas external bypass pipeline is also connected to the pyrolysis gas delivery pipeline.

[0080] Example 4

[0081] The system repeats Example 3, except that it also includes a fractionation unit 10. The oil outlet of the pyrolysis unit 3 is connected to the feed inlet of the fractionation unit 10 via an oil pipeline. The light water outlet of the fractionation unit 10 is connected to the water inlet of the water washing and filter press unit 4 via a water pipeline. The light oil outlet of the fractionation unit 10 is connected to the feed inlet of the distillation unit 6 via an oil pipeline. The heavy oil outlet of the fractionation unit 10 is connected to the feed inlet of the mixing and pelletizing unit 7 via an oil pipeline.

[0082] Example 5

[0083] Example 6 is repeated, except that the system also includes a salt concentration and separation device 11. The filtrate outlet of the water washing and filter press 4 is connected to the feed inlet of the salt concentration and separation device 11 via a water supply pipe.

[0084] Example 6

[0085] Example 5 is repeated, except that the filtrate outlet of the water washing filter press 4 is also connected to the water inlet of the water washing filter press 4 through a circulating water pipe.

[0086] Example 7

[0087] The system is repeated in Example 6, except that it also includes a condenser 12. The steam outlets of both the drying unit 1 and the salt concentration and separation unit 11 are connected to the steam inlet of the condenser 12 via steam pipelines. The water outlet of the condenser 12 is connected to the water inlet of the water washing and filter press 4 via a water pipeline.

[0088] Example 8

[0089] picture Figure 1 As shown, the method for preparing metallurgical biomass fuel using the system described in Example 7 includes the following steps:

[0090] 1) The biomass is dried and crushed to obtain biomass dry powder.

[0091] 2) The biomass dry powder is pyrolyzed to obtain biochar, pyrolysis gas and bio-oil.

[0092] 3) The biochar is washed with water to obtain washed biochar and saline wastewater.

[0093] 4) Add quicklime to the washed charcoal and mix well to obtain digested feed.

[0094] 5) The bio-oil obtained in step 2) is fractionated to obtain light water, light oil, and heavy oil. Then, the digestate is mixed with the light oil and distilled to obtain distilled char and light bio-oil.

[0095] 6) Add heavy oil and iron-containing solid waste to distilled charcoal for mixing and pelletizing to obtain carbon-iron raw pellets.

[0096] 7) Carbonize the iron pellets to obtain biomass fuel.

[0097] Example 9

[0098] like Figure 2 As shown, Example 8 is repeated, except that the method further includes:

[0099] 8) The pyrolysis gas obtained in step 2) is burned as fuel to obtain high-temperature flue gas, which is then recycled for the pyrolysis of biomass dry powder and / or for the carbonization of carbon-iron pig pellets. The medium-temperature flue gas emitted during the pyrolysis and carbonization processes is recycled for the drying of biomass and for subsequent concentration and desalination.

[0100] Example 10

[0101] Repeat Example 9, except that the method further includes:

[0102] 9) The saline wastewater is recycled for the washing treatment of biochar to obtain high-salt wastewater. The high-salt wastewater is then concentrated and desalinated to obtain mixed salt and condensate. The condensate and light water are recycled as the washing water for biochar.

[0103] Application Example 1

[0104] Biomass straw was dried at 110℃ for 50 minutes, and then crushed into particles smaller than 1 mm using a crusher to obtain biomass dry powder. The biomass dry powder was then placed in a pyrolysis furnace with indirect heat exchange and pyrolyzed at 750℃ for 40 minutes in an oxygen-free environment. Biochar (volatile matter content of approximately 6.5 wt%), pyrolysis gas, and bio-oil were collected.

[0105] The pyrolysis gas is fed into a hot blast furnace for combustion to obtain high-temperature flue gas for pyrolysis in the pyrolysis furnace. The bio-oil is first fractionated at 120°C and then at 280°C to collect light water (for subsequent washing), light oil and heavy oil respectively.

[0106] Biochar was washed with water at a solid-liquid mass ratio of 1:5, and then filtered to obtain washed biochar (with a water content of approximately 16 wt%). Then, approximately 7 wt% quicklime powder was added to the washed biochar for mixed digestion to obtain digested feed. Then, the digested feed was mixed with light oil at a solid-liquid mass ratio of 1:7 and distilled at 240°C for 35 minutes to collect distilled biochar and light bio-oil (used as fuel for a hot blast stove).

[0107] Heavy oil (12% wt) and iron-containing solid waste were added to distilled charcoal and mixed evenly to obtain a pelletizing mixture (the molar ratio of iron compound to quicklime was approximately 1.3:1). The pelletizing mixture was then extruded under a pressure of 18 MPa for about 60 seconds to obtain carbon-iron raw pellets. Finally, the carbon-iron raw pellets were carbonized at 800℃ for 60 minutes to obtain biomass fuel.

[0108] Application Example 2

[0109] Biomass straw was dried at 115℃ for 50 minutes, and then crushed into particles smaller than 1 mm using a crusher to obtain biomass dry powder. The biomass dry powder was then placed in a pyrolysis furnace with indirect heat exchange and pyrolyzed at 700℃ for 60 minutes in an oxygen-free environment. Biochar (volatile matter content of approximately 6.2 wt%), pyrolysis gas, and bio-oil were collected.

[0110] The pyrolysis gas is fed into a hot blast furnace for combustion to obtain high-temperature flue gas for pyrolysis in the pyrolysis furnace. The bio-oil is first fractionated at 150°C and then at 300°C to collect light water (for subsequent washing), light oil and heavy oil respectively.

[0111] Biochar was washed with water at a solid-liquid mass ratio of 1:6, and then filtered to obtain washed biochar (with a water content of approximately 15 wt%). Then, approximately 5 wt% quicklime powder was added to the washed biochar for mixed digestion to obtain digested feed. Then, the digested feed was mixed with light oil at a solid-liquid mass ratio of 1:5 and distilled at 220°C for 40 minutes to collect distilled biochar and light bio-oil (used as fuel for a hot blast stove).

[0112] Heavy oil (10% wt) and iron-containing solid waste were added to distilled charcoal and mixed evenly to obtain a pelletizing mixture (the molar ratio of iron compound to quicklime was approximately 1.1:1). The pelletizing mixture was then extruded under a pressure of 15 MPa for about 60 seconds to obtain carbon-iron raw pellets. Finally, the carbon-iron raw pellets were carbonized at 850℃ for 60 minutes to obtain biomass fuel.

[0113] Application Example 3

[0114] Biomass straw was dried at 110℃ for 50 minutes, and then crushed into particles smaller than 1 mm using a crusher to obtain biomass dry powder. The biomass dry powder was then placed in a pyrolysis furnace with indirect heat exchange and pyrolyzed at 750℃ for 40 minutes in an oxygen-free environment. Biochar (volatile matter content of approximately 6.2 wt%), pyrolysis gas, and bio-oil were collected.

[0115] The pyrolysis gas is fed into a hot blast furnace for combustion to obtain high-temperature flue gas for pyrolysis in the pyrolysis furnace. The bio-oil is first fractionated at 120°C and then at 280°C to collect light water (for subsequent washing), light oil and heavy oil respectively.

[0116] Biochar was washed with water at a solid-liquid mass ratio of 1:5, and then filtered to obtain washed biochar (with a water content of approximately 16 wt%). Then, quicklime powder of approximately 1 wt% of its mass was added to the washed biochar for mixed digestion to obtain digested feed. Then, the digested feed was mixed with light oil at a solid-liquid mass ratio of 1:7 and distilled at 240°C for 35 minutes to collect distilled biochar and light bio-oil (used as fuel for hot blast stoves).

[0117] Heavy oil (12% wt) and iron-containing solid waste were added to distilled charcoal and mixed evenly to obtain a pelletizing mixture (the amount of iron-containing solid waste added was the same as in Application Example 1). The pelletizing mixture was then extruded under a pressure of 18 MPa for about 60 seconds to obtain carbon-iron raw pellets. Finally, the carbon-iron raw pellets were carbonized at 800℃ for 60 minutes to obtain biomass fuel.

[0118] Application Example 4

[0119] Biomass straw was dried at 110℃ for 50 minutes, and then crushed into particles smaller than 1 mm using a crusher to obtain biomass dry powder. The biomass dry powder was then placed in a pyrolysis furnace with indirect heat exchange and pyrolyzed at 750℃ for 40 minutes in an oxygen-free environment. Biochar (volatile matter content of approximately 6.5 wt%), pyrolysis gas, and bio-oil were collected.

[0120] The pyrolysis gas is fed into a hot blast furnace for combustion to obtain high-temperature flue gas for pyrolysis in the pyrolysis furnace. The bio-oil is first fractionated at 120°C and then at 280°C to collect light water (for subsequent washing), light oil and heavy oil respectively.

[0121] Biochar was washed with water at a solid-liquid mass ratio of 1:5, and then filtered to obtain washed biochar (with a water content of approximately 16 wt%). Then, quicklime powder of approximately 15 wt% of its mass was added to the washed biochar for mixed digestion to obtain digested feed. Then, the digested feed was mixed with light oil at a solid-liquid mass ratio of 1:7 and distilled at 240°C for 35 minutes to collect distilled biochar and light bio-oil (used as fuel for hot blast stoves).

[0122] Heavy oil (12% wt) and iron-containing solid waste were added to distilled charcoal and mixed evenly to obtain a pelletizing mixture (the amount of iron-containing solid waste added was the same as in Application Example 1). The pelletizing mixture was then extruded under a pressure of 18 MPa for about 60 seconds to obtain carbon-iron raw pellets. Finally, the carbon-iron raw pellets were carbonized at 800℃ for 60 minutes to obtain biomass fuel.

[0123] Application Example 5

[0124] Biomass straw was dried at 110℃ for 50 minutes, and then crushed into particles smaller than 1 mm using a crusher to obtain biomass dry powder. The biomass dry powder was then placed in a pyrolysis furnace with indirect heat exchange and pyrolyzed at 750℃ for 40 minutes in an oxygen-free environment. Biochar (volatile matter content of approximately 6.3 wt%), pyrolysis gas, and bio-oil were collected.

[0125] The pyrolysis gas is fed into a hot blast furnace for combustion to obtain high-temperature flue gas for pyrolysis in the pyrolysis furnace. The bio-oil is first fractionated at 120°C and then at 280°C to collect light water (for subsequent washing), light oil and heavy oil respectively.

[0126] Biochar was washed with water at a solid-liquid mass ratio of 1:5, and then filtered to obtain washed biochar (with a water content of approximately 16 wt%). Then, approximately 7 wt% quicklime powder was added to the washed biochar for mixed digestion to obtain digested feed. Then, the digested feed was mixed with light oil at a solid-liquid mass ratio of 1:7 and distilled at 240°C for 35 minutes to collect distilled biochar and light bio-oil (used as fuel for a hot blast stove).

[0127] Heavy oil (12% wt) and iron-containing solid waste were added to distilled charcoal and mixed evenly to obtain a pelletizing mixture (the molar ratio of iron compound to quicklime was approximately 0.1:1). The pelletizing mixture was then extruded under a pressure of 18 MPa for about 60 seconds to obtain carbon-iron raw pellets. Finally, the carbon-iron raw pellets were carbonized at 800℃ for 60 minutes to obtain biomass fuel.

[0128] Application Example 6

[0129] Biomass straw was dried at 110℃ for 50 minutes, and then crushed into particles smaller than 1 mm using a crusher to obtain biomass dry powder. The biomass dry powder was then placed in a pyrolysis furnace with indirect heat exchange and pyrolyzed at 750℃ for 40 minutes in an oxygen-free environment. Biochar (volatile matter content of approximately 5.9 wt%), pyrolysis gas, and bio-oil were collected.

[0130] The pyrolysis gas is fed into a hot blast furnace for combustion to obtain high-temperature flue gas for pyrolysis in the pyrolysis furnace. The bio-oil is first fractionated at 120°C and then at 280°C to collect light water (for subsequent washing), light oil and heavy oil respectively.

[0131] Biochar was washed with water at a solid-liquid mass ratio of 1:5, and then filtered to obtain washed biochar (with a water content of approximately 16 wt%). Then, approximately 7 wt% quicklime powder was added to the washed biochar for mixed digestion to obtain digested feed. Then, the digested feed was mixed with light oil at a solid-liquid mass ratio of 1:7 and distilled at 240°C for 35 minutes to collect distilled biochar and light bio-oil (used as fuel for a hot blast stove).

[0132] Heavy oil (12% wt) and iron-containing solid waste were added to distilled charcoal and mixed evenly to obtain a pelletizing mixture (the molar ratio of iron compound to quicklime was approximately 3.5:1). The pelletizing mixture was then extruded under a pressure of 18 MPa for about 60 seconds to obtain carbon-iron raw pellets. Finally, the carbon-iron raw pellets were carbonized at 800℃ for 60 minutes to obtain biomass fuel.

[0133] Comparative Example 1

[0134] Biomass straw was dried at 110℃ for 50 minutes, and then crushed into particles smaller than 1 mm using a crusher to obtain biomass dry powder. The biomass dry powder was then placed in a pyrolysis furnace with indirect heat exchange and pyrolyzed at 750℃ for 40 minutes in an oxygen-free environment. Biochar (volatile matter content of approximately 4 wt%), pyrolysis gas, and bio-oil were collected.

[0135] The pyrolysis gas is fed into a hot blast furnace for combustion to obtain high-temperature flue gas for pyrolysis in the pyrolysis furnace. The bio-oil is first fractionated at 120°C and then at 280°C to collect light water (for subsequent washing), light oil and heavy oil respectively.

[0136] Biochar was washed with water at a solid-liquid mass ratio of 1:5, and then filtered to obtain washed char (water content of about 16wt%). The washed char was then mixed with light oil at a solid-liquid mass ratio of 1:7 and distilled at 240℃ for 35 minutes to obtain distilled char and light bio-oil (used as fuel for hot blast stoves).

[0137] Heavy oil (12% wt) and iron-containing solid waste were added to distilled charcoal and mixed evenly to obtain a pelletizing mixture (the amount of iron-containing solid waste added was the same as in Application Example 1). The pelletizing mixture was then extruded under a pressure of 18 MPa for about 60 seconds to obtain carbon-iron raw pellets. Finally, the carbon-iron raw pellets were carbonized at 800℃ for 60 minutes to obtain biomass fuel.

[0138] Comparative Example 2

[0139] Biomass straw was dried at 110℃ for 50 minutes, and then crushed into particles smaller than 1 mm using a crusher to obtain biomass dry powder. The biomass dry powder was then placed in a pyrolysis furnace with indirect heat exchange and pyrolyzed at 750℃ for 40 minutes in an oxygen-free environment. Biochar (volatile matter content of approximately 4 wt%), pyrolysis gas, and bio-oil were collected.

[0140] The pyrolysis gas is fed into a hot blast furnace for combustion to obtain high-temperature flue gas for pyrolysis in the pyrolysis furnace. The bio-oil is first fractionated at 120°C and then at 280°C to collect light water (for subsequent washing), light oil and heavy oil respectively.

[0141] Biochar was washed with water at a solid-liquid mass ratio of 1:5, and then filtered to obtain washed biochar (with a water content of approximately 16 wt%). Then, approximately 7 wt% quicklime powder was added to the washed biochar for mixed digestion to obtain digested feed. Then, the digested feed was mixed with light oil at a solid-liquid mass ratio of 1:7 and distilled at 240°C for 35 minutes to collect distilled biochar and light bio-oil (used as fuel for a hot blast stove).

[0142] Heavy oil of 12% wt was added to distilled charcoal and mixed evenly to obtain a pelletizing mixture. The pelletizing mixture was then extruded under a pressure of 18 MPa for about 60 seconds to obtain carbon-iron pig pellets. Finally, the carbon-iron pig pellets were carbonized at 800℃ for 60 minutes to obtain biomass fuel.

[0143] Comparative Example 3

[0144] The biomass straw is dried at 110℃ for 50 minutes, and then the dried straw is crushed to a particle size of less than 1 mm to obtain biomass dry powder.

[0145] Biomass dry powder is washed with water at a solid-liquid mass ratio of 1:5, and then filtered to obtain washed residue (moisture content of about 15wt%). Then, about 7wt% of quicklime powder is added to the washed residue for mixed digestion to obtain digested feed. Then, iron-containing solid waste is added to the digested feed and mixed evenly to obtain pelleting mixture (molar ratio of iron compound to quicklime of about 1.3:1). Then, the pelleting mixture is extruded under a pressure of 15MPa for about 60s to obtain carbon-iron pig pellets. Finally, the carbon-iron pig pellets are carbonized at 800℃ for 60min to obtain biomass fuel.

[0146] The biomass fuels used in Application Examples 1-6 (i.e., Comparative Examples 1-3) were tested, and their key parameter properties are shown in the table below:

[0147]

Claims

1. A method for preparing biomass fuel for metallurgical use, characterized in that: The method includes the following steps: 1) The biomass is dried and crushed to obtain biomass dry powder; 2) The biomass dry powder is pyrolyzed to obtain biochar, pyrolysis gas and bio-oil; 3) The biochar is washed with water to obtain washed biochar and saline wastewater; 4) Add quicklime to the washed charcoal and mix well to obtain digested feed; 5) The bio-oil obtained in step 2) is fractionated to obtain light water, light oil and heavy oil; then the digestate is mixed with the light oil and distilled to obtain distilled char and light bio-oil. 6) Add heavy oil and iron-containing solid waste to distilled charcoal for mixing and pelletizing to obtain carbon-iron raw pellets; 7) Carbonize the iron pellets to obtain biomass fuel.

2. The method according to claim 1, characterized in that: The method also includes: 8) The pyrolysis gas obtained in step 2) is used as fuel for combustion to obtain high-temperature flue gas, which is then recycled for the pyrolysis treatment of biomass dry powder and / or for the carbonization treatment of carbon-iron pig pellets; the medium-temperature flue gas emitted during the pyrolysis and / or carbonization treatment is recycled for the drying treatment of biomass and / or for subsequent concentration and desalination treatment; and / or 9) The saline wastewater is recycled for the washing treatment of biochar to obtain high-salt wastewater. Then, the high-salt wastewater is concentrated and desalinated to obtain mixed salt and condensate.

3. The method according to claim 2, characterized in that: Condensate and light water are recycled and used as water for washing biochar.

4. The method according to claim 1, characterized in that: In step 1), the drying and crushing process specifically involves drying the biomass at a temperature of 90-160℃ for 0.3-3 hours, and then crushing the dried biomass to a particle size of less than 1.5 mm to obtain dried biomass powder.

5. The method according to claim 4, characterized in that: In step 1), the drying and crushing process specifically involves drying the biomass at 105-140℃ for 0.5-2 hours, and then crushing the dried biomass to a particle size of less than 1 mm to obtain dried biomass powder.

6. The method according to claim 4, characterized in that: In step 1), the moisture content of the biomass dry powder is not higher than 5 wt%.

7. The method according to claim 6, characterized in that: In step 1), the moisture content of the biomass dry powder is 0.5-3 wt%.

8. The method according to claim 1, characterized in that: In step 2), the pyrolysis treatment specifically involves pyrolyzing the biomass dry powder at a temperature of 600-900℃ for 0.1-2 hours in an oxygen-isolated environment; the gas produced during the pyrolysis process is pyrolysis gas, the liquid produced is bio-oil, and the remaining solid is biochar.

9. The method according to claim 8, characterized in that: In step 2), the biomass powder is pyrolyzed at 700-800℃ for 0.3-1h in an oxygen-isolated environment.

10. The method according to claim 8, characterized in that: In step 2), the volatile matter content in the biochar is less than 10% by mass.

11. The method according to claim 10, characterized in that: In step 2), the volatile matter content in the biochar is 3-8% by mass.

12. The method according to claim 1, characterized in that: In step 3), the solid-liquid mass ratio of the water washing treatment is 1:2-8; the water washing time is not less than 10 minutes; and / or In step 4), the water content of the washed charcoal is less than 30 wt%; the amount of quicklime added is 3-12% of the total mass of the washed charcoal.

13. The method according to claim 12, characterized in that: In step 3), the solid-liquid mass ratio of the water washing treatment is 1:3-6; the water washing time is 30-60 min; and / or In step 4), the water content of the washed charcoal is 10-20 wt%; the amount of quicklime added is 5-10% of the total mass of the washed charcoal.

14. The method according to claim 1, characterized in that: In step 5), the fractionation process specifically involves: first, fractionating the bio-oil at 100-150°C to obtain light water and oil; then, fractionating the oil at 250-350°C to obtain light oil and heavy oil; and / or In step 5), the distillation process specifically involves distilling the mixture of digested feed and light oil at 200-300°C for 20-60 minutes to obtain distilled charcoal and light bio-oil.

15. The method according to claim 14, characterized in that: In step 5), the distillation process specifically involves distilling the mixture of digested feed and light oil at 240-280°C for 30-50 minutes to obtain distilled charcoal and light bio-oil.

16. The method according to claim 14, characterized in that: In step 5), the mass ratio of the digested feed to the light oil is 1:1-10.

17. The method according to claim 16, characterized in that: In step 5), the mass ratio of the digested feed to the light oil is 1:2-7.

18. The method according to claim 1, characterized in that: In step 6), the amount of heavy oil added is 8-20% of the total mass of the distilled charcoal; and / or In step 6), the amount of iron-containing solid waste added is such that the molar ratio of iron-containing compounds to quicklime in the mixture is 0.5-2:

1.

19. The method according to claim 18, characterized in that: In step 6), the amount of heavy oil added is 10-15% of the total mass of the distilled charcoal; and / or In step 6), the amount of iron-containing solid waste added is such that the molar ratio of iron-containing compounds to quicklime in the mixture is 0.8-1.5:

1.

20. The method according to claim 1, characterized in that: In step 6), the pelletizing process is extrusion pelletizing, with an extrusion pelletizing pressure of not less than 10 MPa; the extrusion pelletizing time is 30-120 s; and / or In step 6), the particle size of the carbon iron pellets is 3-12 mm.

21. The method according to claim 20, characterized in that: The extrusion pelletizing pressure is 12-20 MPa; the extrusion pelletizing time is 50-90 s; and / or In step 6), the particle size of the carbon iron pellets is 4-9 mm.

22. The method according to claim 1, characterized in that: In step 7), the carbonization process specifically involves carbonizing the carbon-iron pellets at a temperature of 500-900℃ for 10-90 minutes to obtain biomass fuel.

23. The method according to claim 22, characterized in that: In step 7), the carbonization process specifically involves carbonizing the carbon-iron pellets at a temperature of 600-850℃ for 20-60 minutes to obtain biomass fuel.

24. The method according to claim 2, characterized in that: In step 8), the pyrolysis gas is used as fuel in a hot blast stove and combusted with combustion air to obtain high-temperature flue gas at 800-1000°C; and / or In step 8), the temperature of the medium-temperature flue gas is 300-500℃.

25. The method according to claim 24, characterized in that: In step 8), the pyrolysis gas is used as fuel in a hot blast stove and combusted with combustion air to obtain high-temperature flue gas at 850-950°C; and / or In step 8), the temperature of the medium-temperature flue gas is 350-450°C.

26. The method according to claim 2, characterized in that: In step 8), the water-containing hot gas generated during the drying process is condensed to obtain dried condensate, which is then used for the water washing treatment of biochar.

27. The method according to claim 2, characterized in that: In step 9), the concentration factor of the high-salinity wastewater is 2-8 times; and / or Both the pyrolysis and carbonization processes are performed using indirect heat exchangers.

28. The method according to claim 27, characterized in that: In step 9), the concentration factor of the high-salt wastewater is 3-6 times.

29. A system for use in the method of any one of claims 1-28, characterized in that: The system includes a drying device (1), a crushing device (2), a pyrolysis device (3), a water washing and filtration device (4), a mixing and digestion device (5), a distillation device (6), a mixing and pelletizing device (7), and a carbonization device (8); the drying device (1), crushing device (2), pyrolysis device (3), water washing and filtration device (4), mixing and digestion device (5), distillation device (6), mixing and pelletizing device (7), and carbonization device (8) are arranged in series; the pyrolysis device (3) and the carbonization device (8) are both indirect heat exchange devices.

30. The system according to claim 29, characterized in that: The system also includes a hot air furnace (9); the hot air outlet of the hot air furnace (9) is connected to the hot air inlets of the pyrolysis device (3) and the carbonization device (8) respectively through a hot air conveying pipe; the hot air outlets of the pyrolysis device (3) and the carbonization device (8) are connected to the hot air inlet of the drying device (1) through a hot air conveying pipe; the air outlet of the drying device (1) is connected to the chimney through an exhaust pipe.

31. The system according to claim 30, characterized in that: The pyrolysis gas outlet of the pyrolysis device (3) is connected to the fuel inlet of the hot air furnace (9) through a pyrolysis gas delivery pipeline; the oil outlet of the distillation device (6) is connected to the fuel inlet of the hot air furnace (9) through an oil delivery pipeline.

32. The system according to claim 31, characterized in that: A pyrolysis gas external bypass pipeline is also connected to the pyrolysis gas delivery pipeline.

33. The system according to claim 29, characterized in that: The system also includes a fractionation device (10); the oil outlet of the pyrolysis device (3) is connected to the feed inlet of the fractionation device (10) through an oil pipeline; the light water outlet of the fractionation device (10) is connected to the water inlet of the water washing filter press (4) through a water pipeline; the light oil outlet of the fractionation device (10) is connected to the feed inlet of the distillation device (6) through an oil pipeline; and the heavy oil outlet of the fractionation device (10) is connected to the feed inlet of the mixing and pelletizing device (7) through an oil pipeline.

34. The system according to claim 29, characterized in that: The system also includes a salt concentration and separation device (11); the filtrate outlet of the water washing and filter press device (4) is connected to the feed inlet of the salt concentration and separation device (11) through a water supply pipe.

35. The system according to claim 34, characterized in that: The filtrate outlet of the water washing filter press (4) is also connected to the water inlet of the water washing filter press (4) through a circulating water pipe.

36. The system according to claim 35, characterized in that: The system also includes a condenser (12); the steam outlets of the drying device (1) and the salt concentration and separation device (11) are connected to the steam inlet of the condenser (12) through a steam pipeline; the water outlet of the condenser (12) is connected to the water inlet of the water washing and filter press device (4) through a water pipeline.

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