A metallurgical biocoke preparation system and method based on bio-oil graded utilization

Abstract

The present invention provides a metallurgical biocoke production system and method based on the graded utilization of bio-oil. The system includes a first pyrolysis furnace, a cyclone separator, a first condensing unit, a second condensing unit, a pickling unit, a granulating unit, a first conveyor, a second pyrolysis furnace, a coke oven, and a second conveyor. The outlet of the first pyrolysis furnace is connected to the inlet of the cyclone separator, and the solid phase flows sequentially through the cyclone separator, the pickling unit, the granulating unit, the first conveyor, the second pyrolysis furnace, the coke oven, and the second conveyor. The gas and liquid phases flow sequentially through the cyclone separator and the condensing unit. The heavy oil outlet of the first condensing unit is connected to the granulating unit, and the light oil outlet of the second condensing unit is connected to the pickling unit. Through the graded utilization of bio-oil, this system and method achieves autonomous control of the properties of metallurgical biocoke, improving biomass utilization while avoiding additional costs and risks associated with the supply chain.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, and in particular to a metallurgical bio-coke preparation system and method based on the graded utilization of bio-oil. Background Art

[0002] The steel industry is one of the largest industrial carbon dioxide emitters. In my country, the long-process steelmaking process accounts for approximately 9.2% of the country's total carbon emissions and around 15% of total industrial carbon emissions. The blast furnace-converter process, the predominant steelmaking route, suffers from high energy consumption and high carbon emissions in the sintering, coking, and blast furnace processes. Carbon emissions from the blast furnace process are particularly significant, accounting for over 75% of the total carbon emissions from the steel industry, highlighting the significant challenges facing the blast furnace process in energy conservation and emission reduction. Biomass energy utilization technologies can reduce carbon emissions from the long-process process by 30-40%, garnering widespread attention as a substitute for fossil fuels. However, unlike mature applications in power generation and heating, the application of biomass in the steel industry is still at a technical juncture, with limited demonstration projects. Therefore, research on biomass energy utilization in the steel industry holds great research significance and broad application prospects.

[0003] Biomass resources, a valuable natural asset second only to traditional fossil energy in terms of reserves, are widely distributed and diverse, encompassing crop residues, forestry waste, municipal solid waste, and aquatic plants. Biomass can be introduced into blast furnaces as a low-carbon fuel and reducing agent in three forms: biochar, bio-oil, and biomass-derived syngas. However, due to economic and operational considerations, previous research has focused on blast furnace injection of biocoke. Biocoke can be widely used in various processes, including coke production (coking with coal), tuyere injection, iron ore sintering, and carbon composite pelletization. However, unlike traditional coal coke, biocoke's high alkali metal content, low strength, high reactivity, and high volatile content limit its inclusion rate. For example, its inclusion rate in coke should not exceed 2–10 wt.%, and its inclusion rate in sintering should not exceed 40 wt.%, significantly reducing the carbon reduction potential of biomass energy. Therefore, there is an urgent need to develop novel metallurgical biocoke performance control technologies to meet the requirements for low-carbon fuels and reducing agents in various process steps. Summary of the Invention

[0004] The present invention provides a metallurgical biocoke preparation system and method based on bio-oil graded utilization, which are used to solve the defects of biocoke in the prior art, such as high alkali metal content, low strength and high volatile matter content.

[0005] The present invention provides a metallurgical bio-coke preparation system based on bio-oil graded utilization, comprising a first pyrolysis furnace, a cyclone separator, a first condensing device, a second condensing device, a pickling device, a granulating device, a first conveyor, a second pyrolysis furnace, a coke oven, and a second conveyor;

[0006] The inlet of the first pyrolysis furnace is used to input biomass fuel, the outlet of the first pyrolysis furnace is connected to the inlet of the cyclone separator, the solid phase outlet of the cyclone separator is connected to the solid phase inlet of the pickling device, the solid phase outlet of the pickling device is connected to the solid phase inlet of the granulation device, the outlet of the granulation device is connected to the inlet of the first conveyor, the outlet of the first conveyor is connected to the solid phase inlet of the second pyrolysis furnace, the solid phase outlet of the second pyrolysis furnace is connected to the solid phase inlet of the coke oven, the solid phase outlet of the coke oven is connected to the inlet of the second conveyor, and the outlet of the second conveyor is used to output demineralized bio-coke particles; the gas phase outlet of the cyclone separator is connected to the inlet of the first condensing device, the heavy oil outlet of the first condensing device is connected to the liquid phase inlet of the granulation device, the gas phase outlet of the first condensing device is connected to the inlet of the second condensing device, the light oil outlet of the second condensing device is connected to the liquid phase inlet of the pickling device, and the liquid phase outlet of the pickling device is used to output pickling waste liquid;

[0007] The first pyrolysis furnace, the second pyrolysis furnace and the coke oven are all provided with a flue gas inlet for inputting high-temperature flue gas.

[0008] According to the present invention, a metallurgical bio-coke preparation system based on bio-oil graded utilization is provided, which also includes a gas furnace, and the flue gas inlets of the first pyrolysis furnace, the second pyrolysis furnace and the coke oven are respectively connected to the flue gas outlet of the gas furnace; the second condensing device and the gas phase outlet of the second pyrolysis furnace are respectively connected to the primary gas inlet of the gas furnace to input primary gas; the gas phase outlet of the coke oven is connected to the secondary gas inlet of the gas furnace pair to input secondary gas.

[0009] The present invention also provides a method for preparing metallurgical biocoke based on the graded utilization of bio-oil, using the preparation system as described above, comprising:

[0010] S1: feeding the biomass fuel into the first pyrolysis furnace for primary pyrolysis to generate a mixture of biochar, bio-oil vapor and pyrolysis gas;

[0011] S2: The mixture enters the cyclone separator for gas-solid separation to obtain a gas mixture and biochar;

[0012] S3: The gas mixture enters the first condensing device and the second condensing device in sequence for condensation, and the heavy oil, light oil and pyrolysis gas are separated in sequence;

[0013] S4: feeding the biocoke from step S2 into an acid washing device, adding water and the light oil obtained from step S3 to remove the alkaline metals in the biocoke to obtain demineralized biocoke;

[0014] S5: The heavy oil obtained in step S3 and the demineralized bio-coke obtained in step S4 are fed into a granulation device to mix and produce demineralized bio-coke particles;

[0015] S6: The demineralized biochar particles are fed into the second pyrolysis furnace via the first conveyor for secondary pyrolysis to generate enhanced biochar and pyrolysis gas;

[0016] S7: feeding the enhanced biocoke into a coke oven for coking to generate demineralized biocoke particles and pyrolysis gas;

[0017] S8: The demineralized bio-coke particles are transported to various metallurgical links through the second conveyor for application.

[0018] According to the present invention, a method for preparing metallurgical bio-coke based on graded utilization of bio-oil further comprises, in step S7:

[0019] The pyrolysis gas separated in steps S3, S6 and S7 is introduced into the gas furnace as supplementary fuel to generate high-temperature flue gas after the reaction. The heat carried by the high-temperature flue gas is used to maintain the internal temperature of the first pyrolysis furnace, the second pyrolysis furnace and the coke oven, so as to realize the recovery and recycling of the waste heat of the high-temperature exhaust gas.

[0020] According to a method for preparing metallurgical biocoke based on the graded utilization of bio-oil provided by the present invention, in step S3, the condensation temperature of the first condensing device is 100°C to 150°C, and the condensation temperature of the second condensing device is 0°C. Heavy oil is condensed in the first condensing device through an oil bath, and light oil is condensed in the second condensing device through an ice-water mixture.

[0021] According to the present invention, a method for preparing metallurgical bio-coke based on graded utilization of bio-oil further comprises, in step S5:

[0022] Add ethanol to the granulation device.

[0023] According to a method for preparing metallurgical biocoke based on the graded utilization of bio-oil provided by the present invention, the pyrolysis temperature of the first pyrolysis furnace is 500°C to 600°C, the pyrolysis temperature of the second pyrolysis furnace is 200°C to 300°C, and the coking temperature of the coke oven is 950°C to 1050°C.

[0024] According to a method for preparing metallurgical bio-coke based on graded utilization of bio-oil provided by the present invention, the temperature of the gas furnace is 800°C to 1000°C.

[0025] According to the present invention, a method for preparing metallurgical bio-coke based on graded utilization of bio-oil further comprises, after step S4:

[0026] The pickling waste liquid output from the pickling device is converted into organic liquid fertilizer rich in potassium and sodium after fermentation and aging.

[0027] The present invention provides a metallurgical biocoke preparation system and method based on the graded utilization of bio-oil. By washing with an acidic light oil-water solution to control the alkali metal content and using high-viscosity hydrophobic heavy oil to assist in the formation of demineralized biocoke, the system and method ultimately achieve precise control of the properties of metallurgical biocoke without the need for external raw materials. This system and method utilize the weak acidity of pyrolysis light oil to effectively neutralize and reduce the alkali metal content in biocoke without the introduction of additional chemical reagents, thereby solving the problems of difficult alkali metal removal and high energy consumption in traditional methods. Simultaneously, the system and method utilize the adhesive properties of pyrolysis heavy oil to act as both a binder and a coating. As an adhesive, it effectively controls the porosity and fluidity of the biocoke. As a coating, it effectively blocks the intrusion of moisture and other polar substances, protecting the internal structure of the biocoke from damage. This system and method also helps improve the strength, weather resistance, and stability of the biocoke. Through graded condensation utilization, this system and method achieves autonomous control of the properties of metallurgical biocoke, improving the utilization rate of biomass while avoiding the additional costs and risks brought by the supply chain. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 This is a schematic flow diagram of a metallurgical bio-coke preparation system based on bio-oil graded utilization provided by the present invention;

[0030] Reference numerals:

[0031] 1. First pyrolysis furnace; 2. Cyclone separator; 3. First condensing device; 4. Second condensing device; 5. Pickling device; 6. Granulating device; 7. First conveyor; 8. Second pyrolysis furnace; 9. Coke oven; 10. Gas furnace; 11. Second conveyor. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0033] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of the present invention based on specific circumstances.

[0034] It should be noted that, unless otherwise specified or limited, the term "connected" should be understood in a broad sense, for example, it can mean directly connected or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the embodiments of the invention can be understood by those skilled in the art in specific circumstances.

[0035] like Figure 1 As shown, an embodiment of the present invention provides a metallurgical bio-coke preparation system based on bio-oil graded utilization, including a first pyrolysis furnace 1, a cyclone separator 2, a first condensing device 3, a second condensing device 4, a pickling device 5, a granulating device 6, a first conveyor 7, a second pyrolysis furnace 8, a coke oven 9, a gas furnace 10 and a second conveyor 11.

[0036] The inlet of the first pyrolysis furnace 1 is used to input biomass fuel, the outlet of the first pyrolysis furnace 1 is connected to the inlet of the cyclone separator 2, the solid phase outlet of the cyclone separator 2 is connected to the solid phase inlet of the pickling device 5, the outlet of the pickling device 5 is connected to the inlet of the granulation device 6, the outlet of the granulation device 6 is connected to the inlet of the first conveyor 7, the outlet of the first conveyor 7 is connected to the solid phase inlet of the second pyrolysis furnace 8, the solid phase outlet of the second pyrolysis furnace 8 is connected to the solid phase inlet of the coke oven 9, and the solid phase outlet of the coke oven 9 is connected to the second conveyor 11 to output demineralized bio-coke particles.

[0037] The gas phase outlet of the cyclone separator 2 is connected to the inlet of the first condensing device 3, the liquid phase outlet of the condensing device 3 is connected to the liquid phase inlet of the granulating device 6, the gas phase outlet of the condensing device 3 is connected to the inlet of the second condensing device 4, the liquid phase outlet of the second condensing device 4 is connected to the liquid phase inlet of the pickling device 5, and the liquid phase outlet of the pickling device is used to output the pickling waste liquid.

[0038] The system also includes a gas furnace 10. The first pyrolysis furnace 1, the second pyrolysis furnace 8, and the coke oven 9 are all equipped with flue gas inlets for the input of high-temperature flue gas. The gas phase outlets of the second condensing device 4 and the second pyrolysis furnace 8 are respectively connected to the primary gas inlet of the gas furnace 10 for the input of primary gas; the gas phase outlet of the coke oven 9 is connected to the secondary gas inlet of the gas furnace 10 for the input of secondary gas.

[0039] During use, the biomass raw material is first introduced into the first pyrolysis furnace 1, and the pyrolysis gas-solid mixture at the outlet of the first pyrolysis furnace 1 is introduced into the cyclone separator 2 to achieve gas-solid separation; the gas after gas-solid separation is introduced into the first condensation device 3 and the second condensation device 4 to separate heavy oil, light oil and high-temperature gas; the light oil and the solid after gas-solid separation enter the pickling device 5 to generate demineralized bio-coke; the demineralized bio-coke is formed and granulated with heavy oil in the granulation device 6 and then enters the second pyrolysis furnace 8 and the coke oven 9 in sequence to generate demineralized bio-coke particles.

[0040] The first pyrolysis furnace 1 and the second pyrolysis furnace 8 can be a rotary kiln pyrolysis furnace, a fixed bed pyrolysis furnace, or a fluidized bed pyrolysis furnace, preferably a fluidized bed pyrolysis furnace.

[0041] Cyclone 2 is used to separate the gas and solids from the materials produced after the initial pyrolysis. When the dust-laden airflow enters the cyclone separator at a constant speed through the air inlet pipe, it changes from linear motion to circular motion, spiraling downward from the cylindrical body toward the cone along the wall. Centrifugal force throws particles in the airflow toward the wall. Once in contact with the wall, dust particles lose their inertia and fall along the wall into the ash hopper. The descending, outward-spinning airflow continuously flows toward the center of the separator, forming an upward-spinning, inward-spinning flow, which is discharged from the clean air outlet.

[0042] The first condenser 3 and the second condenser 4 are used to stage-cool the gas and bio-oil vapor produced by the pyrolysis of biomass fuel. The first condenser 3 uses oil bath cooling, which can be achieved using a shell-and-tube heat exchanger, a plate heat exchanger, or an air-cooled heat exchanger. Its basic components include condensing tubes, an oil bath, a cooling pump, a temperature control system, and a condensate collector. The device operates by removing heat from the condensing material through an oil bath, a heat transfer medium, thereby condensing the vapor into a liquid. The cooling oil in the oil bath exchanges heat with the vapor, and the temperature control system maintains the cooling oil within a set temperature range (100°C to 150°C). To ensure effective heat exchange, high-efficiency heat transfer materials, such as copper or aluminum alloy, are used inside the condenser tubes to increase the condensing surface area and improve heat exchange efficiency. The selection of cooling oil should consider factors such as thermal stability, thermal conductivity, and low viscosity. Common cooling oils include mineral oil, synthetic oil, or specialty oils, which have high high-temperature resistance and can effectively reduce temperature fluctuations. To ensure effective condensation, the cooling oil needs to be regularly circulated and filtered to prevent impurities from affecting heat exchange efficiency. The oil bath may be provided with a temperature control system to monitor the temperature of the cooling oil in real time through a temperature sensor to ensure that the temperature is constant during the condensation process and to achieve a sufficient condensation effect. The cooling material of the first condensing device 3 is heavy oil.

[0043] The second condensing device 4 uses an ice-water mixture for cooling. This condensing device can utilize a shell-and-tube heat exchanger, a double-tube heat exchanger, or a cooling tower. Its basic components include condensing tubes, an ice-water mixing tank, a cooling pump, a condensate circulation system, and a temperature control system. The condensation principle is that the ice-water mixture acts as a cooling medium, absorbing the heat released by the steam, thereby condensing the steam into a liquid. The use of an ice-water mixture provides powerful cooling capacity at relatively low temperatures, helping to improve condensation efficiency. Specifically, the ice-water mixture circulates within the condenser's cooling pipes, where it comes into contact with the steam through a highly efficient heat exchange system, rapidly reducing the steam temperature. During the condensation process, the cooling water temperature is maintained at 0°C. An automatic control system adjusts the water flow rate and cooling capacity based on the actual steam temperature, ensuring the stability and adequacy of the condensation process. The cooling water flow is maintained by a cooling pump, and the circulating water system must be equipped with a filter to remove impurities from the water, prevent scaling, and ensure condensation efficiency. The cooling medium in the second condensing device 4 is a mixture of light oil and water. The condensed gas is fed into the gas furnace 10 as supplemental fuel. Heavy oil and light oil differ significantly in composition and properties. Heavy oil contains more macromolecular compounds, such as levoglucosan, trans-isoeugenol and 1,2-cyclopentanedione, has a higher specific gravity and viscosity, poor volatility, and is suitable as an adhesive; light oil is composed of smaller molecular compounds, such as acetone, methanol and acetic acid, has a lower specific gravity and viscosity, high volatility and is suitable as an eluent.

[0044] The pickling unit 5 can be a single-tray solid-phase pickling device. During operation, a mixture of light oil and water enters the system through a pipeline to elute the biocoke particles. The pickling unit 5 consists of two parts: a cover and a housing. The cover is connected to a motor at the top and an agitator at the bottom. During pickling, the agitator is activated by connecting a power source to the power supply, stirring the contents to achieve a uniform pickling effect. The housing is used to hold the material to be stirred and pickled, and has a connecting pipe for water injection.

[0045] The granulation device 6 can be a disc granulator or a twin-screw extruder granulator. Its basic components include a feed system, a granulation drum, a rotating device, a screening device, a cooling system, and a discharge system. Its primary function is to mechanically force the material into granules of a specific size and shape. The feed system uses a vibrating feeder to evenly feed the material into the granulator, ensuring a stable material flow. A drum within the granulation drum generates shear force through rotation, allowing the material to form granules under appropriate pressure and humidity conditions. The granule size and shape can be adjusted to meet specific requirements. The pressure ranges from 100 MPa to 200 MPa, and the humidity ranges from 30% to 50%. To ensure granule stability, heavy oil is added as a binder in an appropriate amount, ranging from 10% to 30%. The screening device is used to classify the granules by size, ensuring uniformity and removing oversized or undersized particles. The cooling system uses air flow cooling, spray cooling or water cooling to ensure that the pellets will not stick or deform due to excessive temperature after forming, thereby maintaining the strength and stability of the pellets. The discharging system transports the formed pellets to the collection area through an automatic discharge device.

[0046] The first conveyor 7 and the second conveyor 11 can be belt conveyors, primarily composed of a conveyor belt, a drive unit, rollers, a tensioning device, a support structure, a feed and discharge system, and a control system. These conveyors are capable of efficiently and stably transporting materials horizontally or at an angle. The conveyor belt is constructed of wear-resistant rubber or polyester to ensure durability and stability during long-term operation. The drive unit, comprised of an electric motor and a speed reducer, utilizes variable frequency speed regulation to adjust the conveying rate to suit varying transport requirements. The control system utilizes a PLC (Programmable Logic Controller) for real-time monitoring of equipment operating status and adjustment of parameters such as speed and start / stop parameters to ensure continuity and efficiency during transport.

[0047] Coke oven 9 can be a side-loading coal coke oven. This equipment primarily consists of a furnace body, heating system, coal charging system, gas exhaust system, coke discharge system, and control system. The side-loading coal coke oven feeds biocoke into the furnace body through a side charging port, ensuring uniform biocoke distribution, optimizing the dry distillation reaction, and improving coke yield and quality. The furnace body is constructed of refractory bricks and high-temperature refractory materials, capable of withstanding operating temperatures exceeding 1100°C. The heating system utilizes a gas-fired heating system, heating the biocoke in the combustion zone within the furnace body to promote pyrolysis and produce biocoke. Biocoke is evenly fed into the furnace via a vibrating feeder. Compared to traditional top-loading coke ovens, side loading effectively avoids uneven coal distribution and improves reaction efficiency. The gas exhaust system recovers and treats exhaust gas from the gas furnace, meeting environmental emission standards. The coke discharge system removes the coke from the furnace using an automatic coke unloading device. The control system, through a PLC automated control system, manages parameters such as coke oven temperature, gas flow, and charge level, ensuring stable and efficient operation.

[0048] The primary function of the gas furnace 10 is to supply heat to various stages of the steelmaking process. Since the condensed gas temperature is not high enough for use, the gas is fed into subsequent gas furnaces 10, providing supplemental fuel for the ironmaking process. High-temperature exhaust gases from combustion can also be introduced into the pyrolysis furnace and coke oven for waste heat recovery. The gas furnace 10 can be a regenerative gas-fired heating furnace, featuring key components such as advanced gas combustion technology, a temperature control system, and an exhaust gas recovery system. The furnace body is typically constructed of high-temperature resistant materials or refractory bricks and can operate stably at temperatures up to 1000°C. The combustion system utilizes low-nitrogen combustion technology, effectively reducing emissions of pollutants such as nitrogen oxides while ensuring combustion efficiency. The temperature control system within the furnace is comprised of a PLC automated control system, which monitors the furnace temperature in real time and precisely adjusts it to ensure uniform and stable heat supply. The exhaust gas recovery system utilizes efficient dust removal, desulfurization, and denitrification equipment to reduce harmful emissions. It also recovers and utilizes waste heat from the exhaust gas, providing a supplemental heat source for the pyrolysis furnace and coke oven, improving overall energy efficiency. The cooling system uses water cooling or air cooling technology to ensure safe operation of the equipment and avoid equipment damage caused by overheating.

[0049] The present invention also provides a method for preparing metallurgical biocoke based on the graded utilization of bio-oil, using the above-described preparation system, comprising:

[0050] S1: Biomass fuel is fed into a first pyrolysis furnace 1 for pyrolysis to generate a mixture of biochar, bio-oil vapor, and pyrolysis gas. The pyrolysis temperature of the first pyrolysis furnace 1 is 500°C to 600°C. In some specific embodiments, the first pyrolysis furnace 1 is pyrolyzed at 550°C, 1 atmosphere of pressure, and an inert atmosphere for 30 minutes to generate biochar particles, gas, and oil vapor.

[0051] S2: The mixture enters cyclone separator 2 for gas-solid separation to obtain a gas mixture and biochar.

[0052] S3: The gas mixture enters the first condensing device 3 and the second condensing device 4 for condensation, and heavy oil, light oil and pyrolysis gas are precipitated; the condensation temperature of the first condensing device 3 is 100℃~150℃, and the condensation temperature of the second condensing device 4 is 0℃. The liquid phase condensed by the first condensing device 3 is heavy oil, and the liquid phase condensed by the second condensing device 4 is a mixture of light oil and water.

[0053] S4: The biocoke from step S2 is fed into an acid washing unit 5, where water and the light oil obtained in step S3 are added to remove alkaline metals from the biocoke, thereby producing demineralized biocoke. In some embodiments, the ratio of water, biocoke, and light oil is generally between 2-5:0.8-1.2:0.3-1. A preferred ratio is 3:1:0.5.

[0054] S5: The heavy oil from step S3 and the demineralized bio-coke from step S4 are fed into a pelletizing unit 6. Ethanol is added to the pelletizing unit 6 to dilute the highly viscous bio-heavy oil, and the mixture is mixed to produce bio-coke pellets. In some embodiments, the mass ratio of demineralized bio-coke:heavy oil:ethanol is 3-5:0.5-1.5:0.5-1.5. Preferably, the ratio of demineralized bio-coke:heavy oil:ethanol is 4:1:1.

[0055] S6: The biochar pellets are fed via the first conveyor 7 into the second pyrolysis furnace 8 for secondary pyrolysis, generating enhanced biochar and pyrolysis gas. The pyrolysis temperature in the second pyrolysis furnace 8 is 200°C to 300°C, and the pyrolysis process is carried out for 30 minutes at 1 atmosphere of pressure and in an inert atmosphere. Compared to the original biochar, the enhanced biochar has higher compressive strength and lower reactivity at high temperatures. Furthermore, due to its uniform structure, the enhanced biochar releases gases more slowly during the coking process, reducing impact and corrosion on the coking furnace.

[0056] S7: The enhanced biocoke is fed into a coke oven 9 for coking to produce demineralized biocoke particles and pyrolysis gas. In some embodiments, the coke oven 9 is operated at 950°C to 1050°C, 1 atmosphere of pressure, and an inert atmosphere for 120 minutes to remove volatiles and increase strength. Compared to the enhanced biocoke, the coked biocoke more closely meets metallurgical coke standards in terms of compressive strength, reactivity, CRI (coke reactivity index), and CSR (coke strength after reaction). The replacement of coal coke in the metallurgical sector by biomass is expected to increase further.

[0057] S8: The pyrolysis gas separated in steps S3, S6 and S7 is used as supplementary fuel to be introduced into the gas furnace 10. After the reaction, high-temperature exhaust gas is generated. The heat carried by the high-temperature exhaust gas is used to maintain the internal temperature of the pyrolysis furnaces 1 and 8 and the coke oven 9, thereby achieving the purpose of efficiently recovering and recycling the waste heat of the high-temperature exhaust gas. Among them, the primary fuel gas is generated by the pyrolysis furnace, which has a lower temperature and is mainly composed of volatile organic compound gases with a lower calorific value. Due to its complex composition, the light organic compounds in the fuel gas need to be further purified and treated before they can be effectively utilized. In contrast, the secondary fuel gas is mainly composed of combustible gases such as carbon monoxide, methane, and hydrogen, with a higher calorific value, and can be put into the gas furnace without excessive treatment.

[0058] S9: The demineralized bio-coke particles are transported to various metallurgical links through the second conveyor 11 for application.

[0059] In addition, it should be noted that the pickling waste liquid output from the liquid phase outlet of the pickling device 5 in step S4 is subjected to separation of solid particles and suspended matter in the waste liquid and dechlorination and desulfurization treatment by standing or accelerating sedimentation, thereby removing suspended matter and some harmful impurities therein. Next, the waste liquid enters a fermentation tank for microbial fermentation. During the fermentation process, anaerobic microorganisms begin to decompose the organic components in the waste liquid under suitable temperature, humidity and oxygen conditions. The metabolic action of microorganisms can not only decompose the complex organic matter in the waste liquid and convert it into nutrients such as organic acids, amino acids, and phenolic compounds, but also promote the conversion of inorganic salts in the waste liquid and convert minerals such as sodium and potassium into a form that can be absorbed by plants. After fermentation is completed, the waste liquid enters an aging tank for natural aging over several weeks to several months. The aging process can make the organic matter produced during the fermentation process more stable and promote the formation of a balanced release pattern of nutrients in the liquid. In the aged liquid fertilizer, the concentrations of major nutrients such as potassium, sodium, and nitrogen are increased, and the release of these nutrients is continuous and stable, which can meet the growth needs of different crops. Furthermore, the aging process further removes any potentially harmful components, ensuring the safety of the liquid fertilizer. Ultimately, the fermented and aged wastewater is transformed into a nutrient-rich organic liquid fertilizer. This liquid fertilizer not only contains significant amounts of essential plant nutrients like potassium, sodium, nitrogen, phosphorus, and calcium, but is also rich in beneficial microorganisms that improve soil biological activity and soil structure.

[0060] The following describes the process with reference to some specific embodiments.

[0061] Example 1

[0062] The biomass is kept at 550° C. for 30 minutes in the first pyrolysis furnace 1 and enters the cyclone separator 2 for gas-solid separation. The solid biocoke enters the acid washing equipment 5 for acid washing with light oil to obtain biocoke.

[0063] Comparative Example 1

[0064] The biomass is kept at 550° C. for 30 minutes in the first pyrolysis furnace 1 and then enters the cyclone separator 2 for gas-solid separation to obtain biochar.

[0065] Comparative Example 2

[0066] The biomass is kept at 550° C. for 30 minutes in the first pyrolysis furnace 1 and enters the cyclone separator 2 for gas-solid separation. The solid biochar enters the acid washing equipment 5 for acid washing with 1 mol / L hydrochloric acid to obtain biochar.

[0067] Table 1 shows the alkaline and alkaline earth metal (AAEM) contents of the biochars from Comparative Examples 1 and 2 and Example 1. Table 1 demonstrates the effectiveness of light oil as an eluent in removing biochar-derived AAEM. Compared to hydrochloric acid, light oil exhibits a higher removal rate, likely due to the presence of phenols in the light oil, which enhances the leaching of organically complexed metals. Furthermore, the hydrophobic interaction between light oil and biochar expands the reactive surface area for alkaline and alkaline earth metals to interact with water and organic acids.

[0068] Table 1 Alkali metal and alkaline earth metal (AAEM) content and dewashing rate in samples

[0069]

[0070] Example 2

[0071] The biomass is kept at 550°C in the first pyrolysis furnace 1 for 30 minutes, enters the cyclone separator 2 for gas-solid separation, and the solid biocoke enters the pickling equipment 5 for pickling with light oil, then enters the granulation equipment 6 for molding and granulation, and is sent to the second pyrolysis furnace 8 via the first conveyor 7 and kept at 250°C for 30 minutes, and then enters the coking furnace 9 and kept at 1000°C for 120 minutes for coking to obtain biocoke particles.

[0072] Comparative Example 3

[0073] The biomass is kept at 550°C for 30 minutes in the first pyrolysis furnace 1 and enters the cyclone separator 2 for gas-solid separation. The solid biochar is sent to the coking furnace 9 and kept at 1000°C for 120 minutes for coking to obtain biochar particles.

[0074] Comparative Example 4

[0075] The bituminous coal is fed into a coking furnace 9 and coked at 1000° C. for 120 minutes to obtain metallurgical coke particles.

[0076] The compressive strength, ignition temperature, burnout temperature, CRI (coke reactivity index) and CSR (coke strength after reaction) of Comparative Examples 3, 4 and Example 2, which are key parameters for evaluating metallurgical coke, are shown in Table 2. As can be seen from Table 2, the biocoke prepared by this method (Example 2) is significantly better than the traditional biocoke (Comparative Example 3) in all data, and the gap with the coal coke (Comparative Example 4) is relatively small. Moreover, Example 2 is very close to the secondary metallurgical coke in terms of the two key indicators of metallurgical coke specified in the national standards of CRI and CSR. These data all show that the biocoke prepared by this system and method has great potential in promoting the application of biomass to replace coal coke in the metallurgical field.

[0077] Table 2 Key parameters of metallurgical coke

[0078]

[0079] *Based on the national standard for metallurgical coke GB / T 1996-2017

[0080] This embodiment provides a metallurgical biocoke production system and method based on the graded utilization of bio-oil. By washing with an acidic light oil-water solution to control alkali content and using high-viscosity, hydrophobic heavy oil to aid in the formation of demineralized bio-coke, the system and method achieve precise control of the properties of metallurgical bio-coke without requiring external raw materials. This system and method utilizes the weak acidity of pyrolyzed light oil to effectively neutralize and reduce the alkali metal content in bio-coke without the introduction of additional chemical reagents, thereby addressing the difficulties of alkali metal removal and high energy consumption in traditional methods. Furthermore, the system and method utilizes the adhesive properties of pyrolyzed heavy oil to act as both a binder and a coating. As a binder, it effectively controls the porosity and fluidity of the bio-coke. As a coating, it effectively blocks the intrusion of moisture and other polar substances, protecting the bio-coke's internal structure from damage and also helping to improve the bio-coke's strength, weather resistance, and stability. Through graded utilization, this system and method achieves autonomous control of the properties of metallurgical bio-coke, improving biomass utilization while avoiding the additional costs and risks associated with the supply chain.

[0081] It can be seen from the above examples that the system and method for preparing metallurgical biocoke provided by the present invention have the following advantages:

[0082] First, based on the properties of biomass oil, a new biomass oil processing method is proposed. The disadvantages of bio-oil being unstable and easy to separate are utilized to effectively utilize the bio-oil as a by-product of coking, thereby increasing the added value of biomass pyrolysis polygeneration products.

[0083] Second, the weak acidity of pyrolysis light oil is used to effectively reduce the alkali metal content in biocoke, avoiding the high energy consumption of traditional water washing and acid washing biomass drying and the difficulty in removing organic alkali metals in biocoke. This achieves the efficient synthesis of demineralized biomass coke, obtains high-quality biocoke, and realizes the goal of producing high-quality products from biomass, which plays an important role in promoting the utilization of biomass energy.

[0084] Third, high-viscosity hydrophobic heavy oil can play a dual role as a binder and a coating, achieving coordinated regulation of the strength and combustion rate of biochar without the need for exogenous binders.

[0085] Fourth, the present invention proposes a new technical route for regulating the performance of metallurgical biocoke, which effectively reduces the high reactivity of biocoke and increases the addition ratio of biocoke to metallurgical coke.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A metallurgical bio-coke preparation system based on bio-oil graded utilization, characterized in that: It includes a first pyrolysis furnace, a cyclone separator, a first condensing device, a second condensing device, a pickling device, a granulating device, a first conveyor, a second pyrolysis furnace, a coke oven, and a second conveyor; The inlet of the first pyrolysis furnace is used to input biomass fuel, the outlet of the first pyrolysis furnace is connected to the inlet of the cyclone separator, the solid phase outlet of the cyclone separator is connected to the solid phase inlet of the pickling device, the solid phase outlet of the pickling device is connected to the solid phase inlet of the granulation device, the outlet of the granulation device is connected to the inlet of the first conveyor, the outlet of the first conveyor is connected to the solid phase inlet of the second pyrolysis furnace, the solid phase outlet of the second pyrolysis furnace is connected to the solid phase inlet of the coke oven, the solid phase outlet of the coke oven is connected to the inlet of the second conveyor, and the outlet of the second conveyor is used to output demineralized bio-coke particles; the gas phase outlet of the cyclone separator is connected to the inlet of the first condensing device, the heavy oil outlet of the first condensing device is connected to the liquid phase inlet of the granulation device, the gas phase outlet of the first condensing device is connected to the inlet of the second condensing device, the light oil outlet of the second condensing device is connected to the liquid phase inlet of the pickling device, and the liquid phase outlet of the pickling device is used to output pickling waste liquid; The first pyrolysis furnace, the second pyrolysis furnace and the coke oven are all provided with a flue gas inlet for inputting high-temperature flue gas.

2. The metallurgical bio-coke preparation system based on bio-oil graded utilization according to claim 1, characterized in that: Also includes a gas stove; The flue gas inlets of the first pyrolysis furnace, the second pyrolysis furnace and the coke oven are respectively connected to the flue gas outlet of the gas furnace; the gas phase outlet of the second condensing device and the second pyrolysis furnace are respectively connected to the primary gas inlet of the gas furnace to input primary gas; the gas phase outlet of the coke oven is connected to the secondary gas inlet of the gas furnace pair to input secondary gas.

3. A method for preparing metallurgical biocoke based on the graded utilization of bio-oil, characterized in that: The preparation system according to any one of claims 1 and 2, comprising: S1: feeding the biomass fuel into the first pyrolysis furnace for primary pyrolysis to generate a mixture of biochar, bio-oil vapor and pyrolysis gas; S2: The mixture enters the cyclone separator for gas-solid separation to obtain a gas mixture and biochar; S3: The gas mixture enters the first condensing device and the second condensing device in sequence for condensation, and the heavy oil, light oil and pyrolysis gas are separated in sequence; S4: feeding the biocoke from step S2 into an acid washing device, adding water and the light oil obtained from step S3 to remove the alkaline metals in the biocoke to obtain demineralized biocoke; S5: The heavy oil obtained in step S3 and the demineralized bio-coke obtained in step S4 are fed into a granulation device to mix and produce demineralized bio-coke particles; S6: The demineralized biochar particles are fed into the second pyrolysis furnace via the first conveyor for secondary pyrolysis to generate enhanced biochar and pyrolysis gas; S7: feeding the enhanced biocoke into a coke oven for coking to generate demineralized biocoke particles and pyrolysis gas; S8: The demineralized bio-coke particles are transported to various metallurgical links through the second conveyor for application.

4. The method for preparing metallurgical bio-coke based on bio-oil graded utilization according to claim 3, characterized in that: Further including: The pyrolysis gas separated in steps S3, S6 and S7 is introduced into the gas furnace as supplementary fuel to generate high-temperature flue gas after the reaction. The heat carried by the high-temperature flue gas is used to maintain the internal temperature of the first pyrolysis furnace, the second pyrolysis furnace and the coke oven, so as to realize the recovery and recycling of the waste heat of the high-temperature exhaust gas.

5. The method for preparing metallurgical bio-coke based on bio-oil graded utilization according to claim 3, characterized in that: In step S3, the condensation temperature of the first condensing device is 100°C to 150°C, and the condensation temperature of the second condensing device is 0°C. The heavy oil is condensed in the oil bath in the first condensing device, and the light oil is condensed in the ice-water mixture in the second condensing device.

6. The method for preparing metallurgical bio-coke based on bio-oil graded utilization according to claim 3, characterized in that: In step S5, it also includes: Add ethanol to the granulation device.

7. The method for preparing metallurgical bio-coke based on bio-oil graded utilization according to claim 3, characterized in that: The pyrolysis temperature of the first pyrolysis furnace is 500°C to 600°C, the pyrolysis temperature of the second pyrolysis furnace is 200°C to 300°C, and the coking temperature of the coke oven is 950°C to 1050°C.

8. The method for preparing metallurgical bio-coke based on bio-oil graded utilization according to claim 4, characterized in that: The temperature of the gas furnace is 800°C to 900°C.

9. The method for preparing metallurgical bio-coke based on the graded utilization of bio-oil according to any one of claims 3 to 8, characterized in that: After step S4, the method further includes: The pickling waste liquid output from the pickling device is converted into organic liquid fertilizer rich in potassium and sodium after fermentation and aging.

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