High-conversion-rate gasification method based on biomass and plastic mixed raw material

Abstract

The invention discloses a high-conversion-rate gasification method based on a biomass and plastic mixed raw material, which adopts a flash evaporation Joule heat technology, does not need to depend on external source heating, can quickly heat the mixed raw material to a high-efficiency gasification interval of 1500-2000 DEG C, solves the defects of high energy consumption ratio, limited temperature interval and long reaction period in traditional pyrolysis, and remarkably improves the gasification rate of the mixed raw material. Meanwhile, a gas-oil-carbon gradient utilization system is constructed, and all-component high-value conversion is achieved: pyrolysis gas generated by gasification is pretreated and then subjected to biological methanation, the pyrolysis gas is efficiently converted into biogas with the purity larger than 95%, and the problems that the pyrolysis gas is low in heat value and poor in stability due to direct utilization are solved; the pyrolysis residual solid carbon residue is activated to prepare a pollutant adsorbent; pyrolysis oil burns to release heat, energy is supplied to the raw material drying and biological methanation process, in order to further optimize the system energy utilization rate, the Joule heat system adopts solar energy to supply power, condensate water generated in the raw material drying process is reused for the gasification link, and the product quality is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, specifically involving a high-conversion-rate gasification method based on a mixture of biomass and plastic raw materials. Background Technology

[0002] With the development of large-scale and modern agriculture, the yield of crop straw has increased dramatically, reaching hundreds of millions of tons annually in my country alone. Simultaneously, to meet the needs of crop insulation, moisture retention, and increased yield, the use of plastic agricultural film continues to grow, exceeding one million tons annually in my country. However, straw and plastic agricultural film become entangled during field disposal, making separation extremely difficult. Agricultural solid waste decomposes slowly after landfilling and easily produces greenhouse gases such as methane. Traditional incineration methods generate large amounts of harmful gases, severely polluting the atmospheric environment.

[0003] In contrast, thermochemical conversion technology can rapidly and stably produce fine chemicals and high-calorific-value liquid fuels based on the structural characteristics of straw and plastic components, serving as chemical raw materials and diesel substitutes. Biomass pyrolysis oil itself suffers from high water and oxygen content; the addition of plastics can not only increase the yield of biomass pyrolysis oil but also improve its viscosity, corrosiveness, and thermal stability, thereby increasing the calorific value of the product.

[0004] Traditional co-pyrolysis processes primarily rely on external heating methods such as electric heating elements and gas furnaces. These methods have a heat transfer efficiency of only 30%-50% and cannot dynamically adjust the heating intensity according to the pyrolysis requirements of the materials. For example, in conventional biomass pyrolysis, a large amount of external energy is continuously consumed to maintain the reaction temperature, yet efficient pyrolysis cannot be achieved. Furthermore, existing technologies often focus on the recovery of a single product; traditional processes often only consider liquid oil, and pyrolysis gas is typically directly burned and vented. In addition, in existing technologies, material pretreatment, pyrolysis reaction, and product collection are independent processes. The low-grade heat generated during pyrolysis is not recovered and utilized. Summary of the Invention

[0005] The purpose of this invention is to provide a high-conversion-rate gasification method based on a mixture of biomass and plastic raw materials to solve the above-mentioned problems.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a high-conversion-rate gasification method based on a mixture of biomass and plastic raw materials, the specific steps of which are as follows: S1. Crushing and drying: Crush the biomass and plastic to a fineness of 100-200 mesh, then dry and dehydrate to a moisture content of ≤ 5%. S2, Mix conductive additives: Mix the pulverized material from S1 with conductive graphite; S3. Fill the mixed packing material from S2 into the central quartz cavity of the airtight reaction chamber. Then, evacuate the reaction chamber through the vacuum pump connected to the evacuation port to create a negative pressure environment inside. Then, introduce inert protective gas Ar or N2 through the air inlet while maintaining the negative pressure in the reaction chamber. S4. The water produced by drying and dehydration in S1 is converted into steam by a condenser and a steam generator and sent into the Joule heating device. The steam needs to be heated to a superheated state at a temperature of 250~400 ℃. S5. After superheated steam is introduced into the Joule heating device in S4, the power control system charges the capacitor bank to 100~300 V according to the amount and resistance of the mixed packing. The high-voltage cable at the positive terminal of the capacitor bank is controlled by the circuit control unit to open and close, with an opening and closing time of 50~1000 ms and the number of opening and closing times. This allows the current to pass through the mixed packing, and the Joule heating is used to rapidly raise the material temperature to 1500~2000 ℃ for pyrolysis to produce biochar, pyrolysis oil and pyrolysis gas. S6. While pyrolysis is being carried out in S5, the heat energy from the combustion of pyrolysis oil is used through a heat exchanger to dry the raw materials in step S1 and maintain the heat supply to the bioreactor. S7. The solid carbon slag generated by the pyrolysis of S5 is activated by gradient temperature control at 700~800 ℃ to produce mesoporous carbon and at 800~900 ℃ to produce microporous carbon. S8. The syngas produced by pyrolysis in S5 is reacted with CO, H2 and CO2 by microorganisms to improve the utilization rate of methane and obtain biogas with a purity of >95%.

[0007] Preferably, the pulverizing and drying device in S1 is one or more of the following: ball mill, horizontal roller mill, Raymond mill, or air jet mill.

[0008] Preferably, the proportion of conductive graphite in the mixed filler in S2 is 0-25%, ensuring that the resistance value of the mixture is ≤ 100 Ω·cm, which is suitable for the Joule heating requirements.

[0009] Preferably, during the pyrolysis process in S5, a portion of the high-temperature pyrolysis gas is rapidly cooled by a cold trap, causing some of it to condense into liquid, while the non-condensable gas is collected in a gas collection device.

[0010] Preferably, the heat exchanger in S6 includes one or more of the following: shell and tube type, plate type, plate and shell type, plate and fin type, or finned type.

[0011] Preferably, in step S6, the preparation of biomethane specifically involves pyrolysis syngas as the core gaseous product, with H2, CO, and CO2 comprising more than 50% of the total. Microorganisms then react CO, H2, and CO2 (e.g., CO + 3H2 → CH4 + H2O, CO2 + 4H2 → CH4 + 2H2O) to improve methane utilization. An anaerobic expanded granular bed reactor, a stirred anaerobic reactor, or a biofilm reactor is used for biomethanation. The reactor temperature is controlled at 35–55 °C, the pH of the reaction system is controlled at 6.0–8.0, and the relative humidity of the reaction gas is controlled at 80%–90%. The reaction product gas enters a purification unit where CO2 is adsorbed using molecular sieves to obtain biomethane with a purity >95%.

[0012] The technical effects and advantages of this invention are as follows: 1. This invention innovatively adopts flash Joule heating technology, which does not rely on external heating and can quickly raise the temperature of mixed raw materials to a high-efficiency gasification range of 1500~2000 ℃, solving the defects of high energy consumption, limited temperature range, and long reaction cycle of traditional pyrolysis, and significantly improving the gasification rate of mixed raw materials; at the same time, it constructs a "gas-oil-carbon" cascade utilization system to achieve high-value conversion of all components: 1. The pyrolysis gas generated by gasification is pretreated and then bio-methanated to efficiently convert it into biomethane with a purity >95%, solving the problems of low calorific value and poor stability of direct utilization of pyrolysis gas; 2. The residual solid carbon residue from pyrolysis is activated to prepare pollutant adsorbents; 3. The heat released by the combustion of pyrolysis oil provides energy for the raw material drying and bio-methanation process; 2. To further optimize the system's energy utilization rate, the Joule heating system is powered by solar energy, and the condensate generated during the raw material drying process is recycled for the gasification process, effectively improving product quality. Through multi-stage energy and material recycling, the system's energy consumption is significantly reduced, achieving efficient, environmentally friendly, and high-value treatment of biomass and plastics, providing a feasible path for the co-processing of agricultural waste and plastic waste. Attached Figure Description

[0013] Figure 1 This is a flowchart of the present invention; Figure 2 Distribution of biomass / plastic Joule thermal gasification products in an example of the present invention; Figure 3 The distribution of biomass / plastic Joule thermal gas phase products in an example of the present invention; Figure 4 This is a diagram illustrating the specific apparatus of the present invention. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] This invention provides, for example Figure 1-4 The high-conversion-rate gasification method based on a biomass-plastic hybrid feedstock shown herein involves mixing and pulverizing the biomass and plastic, followed by drying and dehydration. The dried feedstock is then fed into a flash Joule heating unit for pyrolysis to produce biochar, pyrolysis oil, and pyrolysis gas. The Joule heating unit is powered by solar energy. The cooled biochar is activated and used as a pollutant adsorbent. The pyrolysis gas, after biomethanation and purification, can be stored and supplied as biomethane. The pyrolysis oil can be used as fuel for combustion, providing heat energy for feedstock drying, dehydration, and methane bioconversion. The moisture in the feedstock is condensed and atomized before being fed into the Joule heating unit to improve the feedstock gasification efficiency. A detailed flow chart is provided below. Figure 3 .

[0016] (1) Crush straw (corn, wheat, rice) and plastic agricultural film (mainly polyethylene) to 100-200 mesh. The crushing and drying equipment is ball mill, horizontal roller mill, Raymond mill or air jet mill. Crushing the material can increase the specific surface area of ​​the reactants and make the reaction more complete.

[0017] (2) The moisture content of the raw materials after drying is ≤ 5%. Reduce the moisture content of the materials and increase the reaction temperature.

[0018] (3) The raw materials are mixed with conductive graphite (0~25%) to ensure that the resistance of the mixture is ≤ 100 Ω·cm, which is suitable for the Joule heating requirements. Adding carbon black as a conductive additive can ensure that the mixture has good conductivity so that it can heat up rapidly under Joule heating.

[0019] (4) Fill the pretreated mixed packing into the central quartz cavity of the airtight reaction chamber. Then, evacuate the reaction chamber through the vacuum pump connected to the evacuation port to create a negative pressure environment inside. Then, introduce inert protective gas Ar or N2 through the air inlet while maintaining the negative pressure in the reaction chamber.

[0020] The moisture from the dried raw materials is converted into steam via a condenser and steam generator, which is then fed into the Joule heating unit. The steam needs to be heated to a superheated state, preferably 250-400 °C. Superheated steam increases the water-gas reaction rate and inhibits coke deposition, indirectly improving gasification efficiency. The water-gas reaction (C + H₂O → CO + H₂) and the water-gas shift reaction (CO + H₂O → CO₂ + H₂) are described. (6) Based on the amount and resistance of the mixed filler, the power control system charges the capacitor bank to 100~300 V. The high voltage cable at the positive end of the capacitor bank is controlled by the circuit control unit to open and close, and the opening and closing time and number of opening and closing are 50~1000 ms, so that the current passes through the mixed filler and the Joule heat is used to rapidly raise the material temperature to 1500~2000 ℃.

[0021] (7) The volatiles generated during the reaction process are cooled down rapidly by a cold trap, causing some of the high-temperature pyrolysis gas to condense into liquid, while the non-condensable gas is collected in the gas collection device.

[0022] (8) The heat energy from the combustion of pyrolysis oil is used to dry the raw materials and maintain the temperature requirements of the bioreactor through heat exchangers (shell-and-tube type, plate type, plate-and-shell type, plate-and-fin type or fin type).

[0023] (9) The solid carbon residue generated by pyrolysis is activated by gradient temperature control at 700~800 ℃ to produce mesoporous carbon and 800~900 ℃ to produce microporous carbon, so as to achieve precise customization of adsorption performance and break through the limitations of traditional single-pore activated carbon.

[0024] The syngas from pyrolysis (containing over 50% H2, CO, and CO2) is the core gaseous product, but its direct utilization suffers from low calorific value and poor combustion stability. Microorganisms are used to react CO, H2, and CO2 (e.g., CO + 3H2 → CH4 + H2O, CO2 + 4H2 → CH4 + 2H2O) to improve methane utilization. Biomethanation is carried out using anaerobic expanded granular bed reactors, stirred anaerobic reactors, or biofilm reactors. The reactor temperature is controlled at 35–55 °C, the pH of the reaction system is controlled at 6.0–8.0, and the relative humidity of the reaction gas is controlled at 80%–90%. The reaction product gas enters a purification unit where CO2 is adsorbed using molecular sieves to obtain biomethane with a purity >95%. The entire process utilizes flash Joule heating technology to overcome the shortcomings of traditional pyrolysis technologies, such as reliance on external heating, high energy consumption, insufficient temperature control, and long processing times. A tiered utilization system of "gas-oil-coke" is constructed, where pyrolysis gas is used as raw material for biomethanation to produce biogas, activated biochar serves as an adsorbent for pollutants, and pyrolysis oil provides energy for raw material drying and biomethanation processes. To improve the overall energy efficiency of the system, the Joule heating system is powered by solar energy, fully utilizing the combustion heat of pyrolysis oil for raw material drying. After the raw material moisture is dried and condensed, it enters the pyrolysis process, effectively improving the quality of the pyrolysis gas. Energy consumption is significantly reduced, constructing an "energy cycle closed loop" and breaking through the high energy consumption bottleneck of traditional processes. The products are all high-value-added, upgrading from "single utilization" to "tiered value-added," thereby increasing economic benefits.

[0025] Example 1: Corn stalks, polypropylene, and a mixture of corn stalks and polypropylene (1:1) were placed in a Joule heating apparatus. The resistances of the samples were 67 Ω·cm, 25 Ω·cm, and 100 Ω·cm, respectively. The Joule heating voltage was 150 V, and the heating time was 10 s.

[0026] Table 1 Properties of straw and polypropylene raw materials

[0027] Example 2: Pyrolysis gas from a CO:CO2:H2 ratio (0.5 mmol, 0.5 mmol, 3.5 mmol, 1:1:1) was introduced into a methane bioreactor. The inoculum was anaerobic sludge. The reactor temperature was 55 °C, and the pH was 8. After the reaction, the CH4 concentration reached over 50%.

[0028] Verification: Corn stalks, corn stalks + polypropylene (1:1), and corn stalks + polypropylene + 10 vol% water vapor were subjected to Joule heating at 150 V, with the sample heating temperature ranging from 1500 to 2000 ℃ for 10 s; the product distribution is as follows. Figure 2 Biomass alone produces a gas yield of 45.8 wt%, mixing it with plastics increases the gas yield to 58.5 wt%, and steam gasification increases the gas yield to 66.4 wt%. Figure 3 As shown, the H2 yield is 0.5 wt% when biomass is gasified alone, 3.0 wt% when mixed with plastic, and 8.5 wt% when water vapor is gasified. In summary, the efficiency of the method of the present invention is significantly improved, which solves the shortcomings of traditional pyrolysis technology such as reliance on external heating, high energy consumption, insufficient temperature control, and long time.

[0029] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-conversion gasification method based on a mixture of biomass and plastic raw materials, characterized in that: The specific steps are as follows: S1. Crushing and drying: Crush the biomass and plastic to a fineness of 100-200 mesh, then dry and dehydrate to a moisture content of ≤ 5%. S2, Mix conductive additives: Mix the material after S1 has been crushed and dried with conductive graphite; S3. Fill the mixed packing material from S2 into the central quartz cavity of the airtight reaction chamber. Then, evacuate the reaction chamber through the vacuum pump connected to the evacuation port to create a negative pressure environment inside. Then, introduce inert protective gas Ar or N2 through the air inlet while maintaining the negative pressure in the reaction chamber. S4. The water produced by drying and dehydration in S1 is converted into steam by a condenser and a steam generator and sent into the Joule heating device. The steam needs to be heated to a superheated state at a temperature of 250~400 ℃. S5. After superheated steam is introduced into the Joule heating device in S4, the power control system charges the capacitor bank to 100~300 V according to the amount and resistance of the mixed packing. The high-voltage cable at the positive terminal of the capacitor bank is controlled by the circuit control unit to open and close, with an opening and closing time of 50~1000 ms and the number of opening and closing times. This allows the current to pass through the mixed packing, and the Joule heating is used to rapidly raise the material temperature to 1500~2000 ℃ for pyrolysis to produce biochar, pyrolysis oil and pyrolysis gas. S6. While pyrolysis is being carried out in S5, the heat energy from the combustion of pyrolysis oil is used through a heat exchanger to dry the raw materials in step S1 and maintain the heat supply to the bioreactor. S7. The solid carbon slag generated by the pyrolysis of S5 is activated by gradient temperature control at 700~800 ℃ to produce mesoporous carbon and at 800~900 ℃ to produce microporous carbon. S8. The syngas produced by pyrolysis in S5 is reacted with CO, H2 and CO2 by microorganisms to improve the utilization rate of methane and obtain biogas with a purity of >95%.

2. The high-conversion gasification method based on a biomass and plastic mixed raw material according to claim 1, characterized in that: The pulverizing and drying device in S1 is specifically one or more of the following: ball mill, horizontal roller mill, Raymond mill, or air jet mill.

3. The high-conversion gasification method based on a biomass and plastic mixed raw material according to claim 1, characterized in that: The proportion of conductive graphite in the mixed filler in S2 is 0-25%, ensuring that the resistance of the mixture is ≤ 100 Ω·cm, which is suitable for the Joule heating requirements.

4. The high-conversion gasification method based on a biomass and plastic mixed raw material according to claim 1, characterized in that: During the pyrolysis process in S5, the volatiles generated pass through a cold trap to rapidly cool down a portion of the high-temperature pyrolysis gas, causing some of it to condense into liquid, while the non-condensable gases are collected in a gas collection device.

5. The high-conversion gasification method based on a biomass and plastic mixed feedstock according to claim 1, characterized in that: The heat exchangers in S6 include one or more of the following: shell and tube type, plate type, plate and shell type, plate and fin type, or finned type.

6. The high-conversion gasification method based on a biomass and plastic mixed feedstock according to claim 1, characterized in that: In S6, biomethane production specifically involves pyrolysis syngas as the core gaseous product, with H2, CO, and CO2 comprising over 50% of the total. Microorganisms then react CO, H2, and CO2 (e.g., CO + 3H2 → CH4 + H2O, CO2 + 4H2 → CH4 + 2H2O) to improve methane utilization. Biomethanation is carried out using an anaerobic expanded granular bed reactor, a stirred anaerobic reactor, or a biofilm reactor. The reactor temperature is controlled at 35–55 °C, the pH of the reaction system is controlled at 6.0–8.0, and the relative humidity of the reaction gas is controlled at 80%–90%. The reaction product gas enters a purification unit where CO2 is adsorbed using molecular sieves to obtain biomethane with a purity >95%.

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