A material pyrolysis gasification process, system and application

Abstract

The present invention provides a material pyrolysis and gasification process, system and application, which belongs to the field of solid waste / biomass pyrolysis, and includes a feeding device, a pyrolysis furnace, a semi-coke crusher and a gasification furnace. The feeding device is used to feed the mixed material into the pyrolysis furnace; a pyrolysis gas delivery pipeline is connected to the top of the pyrolysis furnace to deliver the pyrolysis gas, and heating flue gas is introduced into the jacket for drying and pyrolysis of garbage; the pyrolysis semi-coke is cooled to form semi-coke powder, which is sent to the gasification furnace through water vapor to react with the gasification agent to generate output gas with high calorific value. The process of the present invention can achieve self-sufficiency in energy during the pyrolysis and gasification of garbage, and produce fuel gas with high comprehensive calorific value and organic products with high added value. It can be coupled with a gas boiler / gas turbine to fully recover energy while meeting the consumption of water vapor in the pyrolysis and gasification process. It has significant advantages such as high gasification efficiency, high comprehensive calorific value of fuel gas, and high energy utilization efficiency.

Description

Technical Field

[0001] The invention relates to solid waste / biomass pyrolysis, and in particular to a pyrolysis and gasification process for urban domestic waste and its application. Background Art

[0002] Domestic waste treatment technologies include landfill, composting and thermal treatment. Thermal treatment technology can be divided into direct incineration and pyrolysis gasification. From the perspective of pollutant emissions, secondary pollution caused by the insufficiency of direct incineration, especially the emission of dioxins, seriously restricts the promotion and application of this technology. The pyrolysis gasification process is carried out in an oxygen-poor or anoxic atmosphere, which reduces the generation of dioxins in principle. At the same time, most heavy metals will dissolve into ash during the pyrolysis gasification process, reducing the emission of heavy metals.

[0003] However, the existing domestic waste pyrolysis and gasification technology mainly adopts internal heat pyrolysis and gasification. Since a large amount of air will enter the furnace during the internal heat pyrolysis and gasification process, it is easy to produce dioxin pollution like waste incineration. At the same time, the N2 and CO2 contained in the pyrolysis output gas account for a large proportion, which significantly reduces the calorific value of the gas and increases its utilization limitations. On the other hand, waste pyrolysis is a strong endothermic reaction, especially domestic waste contains a large amount of water, and an external heat source is required to heat, dry and pyrolyze the waste. If coal is used for heating, secondary pollution is easy to occur; if electricity and gas are used for heating, the cost is relatively high. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a municipal domestic waste pyrolysis gasification process and system, which mainly solves the current problems of low calorific value of municipal waste pyrolysis gasification gas, secondary pollution risk and high cost.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0006] A material pyrolysis and gasification process, the process sequentially comprises preheating, drying, pyrolysis, gasification and heat recovery, the heat source required for preheating is provided by medium-temperature flue gas greater than 250°C after drying; the heat source required for drying and pyrolysis is provided by medium-temperature flue gas greater than 750°C after gasification in the form of external heating; the heat source required for gasification is provided by high-temperature flue gas greater than 1000°C formed by combustion of combustible gas generated by gasification; heat is recovered from medium-temperature flue gas greater than 750°C after gasification to produce low-temperature flue gas greater than 100°C, after gas-solid separation of the low-temperature flue gas, the gaseous part is purified to become combustible gas, and the solid part is mixed and granulated to produce organic compound fertilizer; the gasification medium required for gasification comprises water vapor produced in the drying and pyrolysis processes, pyrolysis output gas produced in the pyrolysis process and medium-temperature steam produced during heat recovery.

[0007] In addition, in the process of the present invention, the superheated steam discharged before pyrolysis is used for gasification of pyrolysis semi-coke powder, and after the pyrolysis semi-coke is cooled, it is screened and crushed to produce semi-coke powder; the superheated water vapor generated in the semi-coke powder preparation process is used as a conveying medium to convey the semi-coke powder for gasification; the particle size of the semi-coke powder is 50-100 mesh; the residence time of the semi-coke powder in the gasification process is between 0.5-2.0s; and the mass ratio of water vapor to material pyrolysis semi-coke is 0.2-1.0.

[0008] In addition, the present invention also provides a pyrolysis and gasification system for urban domestic waste, comprising a preheating unit, a drying unit, a pyrolysis unit, a gasification unit and a heat recovery unit, the pyrolysis unit comprising a pyrolysis furnace, and the gasification unit comprising a gasification furnace; the heat source required for the preheating unit is provided by the medium-temperature flue gas with a temperature greater than 250°C generated by the drying unit; the heat source required for the drying unit and the pyrolysis furnace is provided by the medium-temperature flue gas with a temperature greater than 750°C after gasification in the gasification furnace in the form of external heating; the heat source required for the gasification furnace is provided by the high-temperature flue gas with a temperature greater than 1000°C formed by the combustion of combustible gas generated by gasification; the medium-temperature flue gas with a temperature greater than 750°C generated by the gasification furnace is heat recovered to produce low-temperature flue gas with a temperature greater than 100°C, and after gas-solid separation of the low-temperature flue gas, the gaseous part is purified to become combustible gas, and the solid part is mixed and granulated to produce organic compound fertilizer; the gasification medium required for gasification in the gasification furnace comprises water vapor produced by the drying unit and the pyrolysis furnace, the pyrolysis output gas produced by the pyrolysis furnace and the medium-temperature steam generated during heat recovery.

[0009] As an optimization method of the pyrolysis furnace, the pyrolysis furnace includes a furnace body shell and an inner cylinder, the inner cylinder is used to hold materials, and the top of the furnace body shell is provided with a flue gas inlet and outlet and a pyrolysis gas outlet. A conversion valve is provided at the flue gas inlet and outlet to change the inlet heat source so as to meet the heat required for drying and pyrolysis respectively; a pyrolysis gas conveying pipeline is connected to the top of the pyrolysis furnace to deliver the pyrolysis gas, and heated flue gas is introduced into the jacket of the pyrolysis furnace for drying and pyrolysis of materials.

[0010] More preferably, the pyrolysis furnace adopts the form of external flue gas heating. The material is sent into the pyrolysis furnace after being filled in the inner cylinder, and flue gases of different temperatures are introduced respectively for drying and pyrolysis of the material. During drying, the moisture in the material is heated and evaporated by the flue gas. After drying is completed, the flue gas with higher temperature is switched to be used for pyrolysis of the material.

[0011] As an optimization method of the gasifier, the gasifier includes multiple small-diameter steel pipes inside, adopts a fluidized bed structure with high-temperature flue gas external heating, the pyrolysis gas coming out of the pyrolysis furnace carries semi-coke powder feed, water vapor is used as a gasifying agent, and the gasification gas produced by gasification is separated from the gas and solid after heat exchange, the gas is purified and used for standby, and the solid is collected and granulated for the preparation of other additional products; the heat required for the gasification of the semi-coke powder in the gasifier comes from the high-temperature flue gas generated by the combustion of the combustible gas produced by gasification; the particle size of the semi-coke powder is 50-100 mesh; the residence time of the semi-coke powder in the gasification furnace is between 0.5-2.0s; the mass ratio of water vapor to the material pyrolysis semi-coke is 0.2-1.0.

[0012] Optionally, when pyrolyzing the semi-coke, the pyrolyzing semi-coke of the material is co-gasified with coal coke, the reaction temperature is 750-950° C., and the mixing ratio of the pyrolyzing semi-coke and coal coke is 1:1.

[0013] More preferably, the gasifier includes a gasification section and a methanation section fluidized bed structure, the pyrolysis product gas is used as a carrier to send the semi-coke powder into the gasification section for gasification reaction, the gasified gas after the reaction enters the methanation section for methanation reaction under the action of a catalyst, and the heat released by the methanation is recovered and used to prepare the gasification agent required for the gasification reaction.

[0014] Furthermore, in the gasifier, the catalyst added to the gasification reaction includes calcium carbonate or calcium oxide, the added amount CaO / C is 0.5, and the reaction temperature is 750-800°C.

[0015] The process or system of the present invention is particularly used for the pyrolysis and gasification of urban domestic garbage, domestic sludge or straw.

[0016] Compared with the prior art, the present invention has the following technical effects:

[0017] The municipal solid waste pyrolysis and gasification process provided by the present invention can realize energy self-sufficiency in the process of waste pyrolysis and gasification, and produce gas with high comprehensive calorific value and organic products with high added value. It can be coupled with a gas boiler / gas turbine to fully recover energy while meeting the consumption of water vapor in the pyrolysis and gasification process. It has significant advantages such as high gasification efficiency, high comprehensive calorific value of gas, and high energy utilization efficiency. Specifically:

[0018] 1. The present invention combines fixed bed drying-pyrolysis with entrained flow gasification technology to achieve the optimal conversion of domestic waste into gas fuel and improve the calorific value of the output gas;

[0019] 2. The process of the present invention can efficiently utilize domestic waste and convert it into combustible gas and ash containing organic carbon. According to the demand for the components of the combustible gas, the present invention can add a suitable catalyst in the methanation section of the gasifier to adjust the composition ratio of the output gas;

[0020] 3. The drying and pyrolysis of the process of the present invention are carried out in the same reactor, and the raw materials do not need to be pretreated. The water vapor generated in the process can be used as a carrier gas to transport the semi-coke powder to the gasifier, and can also be used as a gasifying agent for the gasification reaction of the semi-coke powder;

[0021] 4. The process of the present invention powders the pyrolysis semi-coke and transports it into a gasifier through water vapor for gasification reaction. The water vapor is used as a gasifying agent to greatly increase the gas production, increase the content of combustible gas components, and increase the calorific value of the gas production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the system principle of the present invention;

[0023] Figure 2 It is a schematic diagram of the drying pyrolysis furnace in the present invention;

[0024] Figure 3 Schematic diagram of the gasifier in the present invention.

[0025] The specific contents of the present invention are further explained in detail below with reference to the accompanying drawings. DETAILED DESCRIPTION

[0026] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0027] The municipal domestic waste described in the present invention refers to solid waste generated in daily urban life or in activities that provide services for daily urban life, as well as solid waste that is deemed as municipal domestic waste by laws and administrative regulations, mainly including residential domestic waste, commercial waste, market waste, street waste, public place waste, and waste from institutions, schools, factories, mines and other units (excluding hazardous solid waste such as industrial waste residues and special waste). In addition, the pyrolysis and incineration process of municipal domestic waste described in the present invention is not limited to the above-mentioned municipal domestic waste, and domestic sludge, straw, etc. can also use the system and process described in the present invention.

[0028] The semi-coke described in the present invention is a solid product obtained by dry distillation of peat, lignite and high-volatile bituminous coal at low temperature (500-700° C.).

[0029] Embodiment 1:

[0030] Following the above technical solution, Figure 1-3 As shown, this embodiment provides a pyrolysis gasification system. Taking urban domestic waste as an example, the entire process mainly includes feeding, drying, pyrolysis, gasification and energy recovery and reuse, which specifically includes the following steps:

[0031] First, the sludge, straw and domestic garbage are mixed and preheated after pretreatment such as magnetic separation, and the preheated mixed material is loaded into the inner cylinder of the pyrolysis furnace; the inner cylinder filled with materials is placed in the pyrolysis furnace, and the top of the furnace is provided with flue gas inlet and outlet and pyrolysis gas outlet pipes. The flue gas inlet and outlet are provided with conversion valves to change the inlet heat source to meet the heat required for drying and pyrolysis respectively. The pyrolysis gas outlet is installed with a gas flow meter and a pressure regulating valve to detect the pyrolysis gas flow and adjust the pressure in the furnace. There are two temperature detection points in the pyrolysis furnace, located on the wall and the top outlet of the pyrolysis furnace, respectively, to detect the temperature of the material in the pyrolysis furnace. Changes: The heat source required for drying and pyrolysis is provided by the medium-temperature flue gas after gasification through external heating: At the beginning of the drying stage, the air in the pyrolysis furnace is first extracted to ensure that the material is in an oxygen-deficient or oxygen-free environment. The pyrolysis gas pipeline is closed to make the inner cylinder of the material in a sealed state. During the heating process, the water in the material is gradually heated and evaporated to generate water vapor. The pressure in the furnace continues to increase, and the heat transfer rate between the gas, solid and liquid phases also gradually increases. When the free water on the surface of the material and the combined water inside the material are completely evaporated, heating continues, the temperature in the furnace continues to rise, and the water vapor is in a superheated state, becoming Superheated steam, the pressure in the pyrolysis furnace is controlled by adjusting the pressure regulating valve of the pyrolysis gas outlet pipeline. The discharged water vapor can be used for gasification of pyrolysis semi-coke powder. After the drying process is completed (the moisture content is about 10%), the heating heat source is switched to enter the pyrolysis stage; the dried material begins to be heated and pyrolyzed in the environment of superheated steam, and the generated pyrolysis gas is led out through the pyrolysis gas pipeline on the top of the furnace. The pressure is controlled by the pressure regulating valve. The semi-coke after pyrolysis is cooled and put into use; the pyrolysis semi-coke is then screened by a screening machine and crushed by a crusher to make semi-coke powder for storage and use; the superheated water vapor generated in the process is used as a conveying medium The semi-coke powder is fed into the gasifier, and the gasification reaction is carried out together with the pyrolysis gas drawn from the top of the pyrolysis furnace. The heat source required for gasification comes from the high-temperature flue gas formed by the combustion of the gas generated by gasification. The gasification medium is water vapor, which is provided by the water vapor in the pyrolysis gas and the medium-temperature steam generated in the heat energy recovery process. A plurality of small-diameter steel pipes are evenly arranged in the gasifier, and the semi-coke powder and the gasifying agent are fed into the steel pipes at the same time. The high-temperature flue gas enters the gasifier through the bottom, and performs countercurrent indirect heat exchange with the material in the steel pipe. The material is heated by the high-temperature flue gas and the temperature rises rapidly. The gasification temperature is controlled between 800-900℃, which is conducive to the gasification of the pyrolysis semi-coke.

[0032] Preferably, in order to increase the yield of combustible gas and improve the gasification efficiency, an appropriate amount of catalyst can be added to the gasifier, preferably calcium oxide, which can not only increase the content of combustible gas in the gasification gas, but also promote the cracking of tar during pyrolysis. The addition amount of CaO / C is 0.5, and the reaction temperature is 750-800°C;

[0033] In order to increase the heating area of ​​semi-coke and improve the gasification rate, the particle size of semi-coke powder is 50-100 mesh;

[0034] In order to ensure the gasification effect of semi-coke, the residence time of particles in the gasifier should be controlled between 1.5-2.0s;

[0035] The mass ratio of water vapor to garbage pyrolysis semi-coke is 0.2-1.0;

[0036] In order to increase the methane content in the gasification gas and improve the calorific value of the combustible gas, the gasifier can be designed as a two-stage fluidized bed structure, the upper section is the gasification section, and the lower section is the methanation section. The gasification gas from the gasification section then enters the methanation section to undergo a secondary reaction under the action of a catalyst to increase the methane content in the combustible gas.

[0037] Preferably, the methane content in the combustible gas can be adjusted by controlling the gasification temperature, and a gasification temperature of 700°C-950°C is conducive to the generation of methane;

[0038] The heat required for the whole process is all provided by the combustion of combustible gas generated by gasification. The high-temperature flue gas (>1100℃) generated after the combustion of combustible gas first enters the gasifier to provide the heat required for gasification. The flue gas temperature coming out of the gasifier is -750℃ and is divided into two parts. One part enters the steam generator to generate medium-temperature steam, and the other part enters the garbage pyrolysis unit to provide the heat required for garbage pyrolysis. The flue gas temperature coming out of the pyrolysis section is -500℃, which is then used for garbage drying. The outlet flue gas temperature after drying is -250℃, which is used to assist in the generation of medium-temperature steam. The low-temperature flue gas after heat recovery by steam generation can be further used for air preheating. Since the drying and pyrolysis of garbage are carried out in the same reactor, in actual working conditions, multiple pyrolysis furnaces are required to be connected in series to reasonably allocate and utilize flue gases of different tastes.

[0039] The gasification unit uses water vapor as the gasification agent. The sources of water vapor include two parts: a large amount of water vapor generated during the drying pyrolysis process enters the gasifier together with the pyrolysis gas and participates in the gasification reaction of the semi-coke powder as a gasification agent; the output gas from the gasifier needs to be recycled through a steam generator before entering the gas-solid separator, and the generated medium-temperature steam can be used as a gasification agent to supplement the gasification process;

[0040] In order to increase the energy density of garbage pyrolysis semi-coke and improve the calorific value of gasification gas, the pyrolysis semi-coke of garbage can be co-gasified with coal coke, with the reaction temperature being 750-950℃ and the mixing ratio of pyrolysis semi-coke and coal coke being 1:1.

[0041] The gasifier of the present invention generates a high calorific value output gas (composition is about φ(H2) = 20%-26%, φ(CO) = 28%-42%, φ(CO2) = 16%-23%, φ(CH4) = 10%-20%, calorific value is 10-13MJ / m 3); The semi-coke residue and bag ash after gasification contain rich organic carbon, which can be used to produce organic carbon fertilizer, while harmful heavy metals such as lead, cadmium, and arsenic can be treated by ceramicization. The formed ceramic materials can be used for floor tiles, etc. The heat required for the gasification of the semi-coke powder in the gasifier comes from the high-temperature flue gas generated by the combustion of the combustible gas produced by the gasification. The output gas of the gasifier is recovered through the heat exchanger to produce medium-temperature steam. The process of the present invention is energy self-sufficient, has high gasification efficiency, and has a high calorific value of the output gas, which has obvious advantages.

[0042] It mainly includes a pyrolysis furnace and a gasification furnace, wherein: the pyrolysis furnace adopts the method of external heating and internal barrel feeding, and a heating flue gas inlet pipeline is provided on the top of the pyrolysis furnace, which is used to dry and pyrolyze the domestic garbage to produce pyrolysis gas, and a pyrolysis gas conveying pipeline is used to lead the pyrolysis gas out for standby use;

[0043] The pyrolysis furnace adopts the form of flue gas external heating. The inner cylinder is filled with materials and then sent into the pyrolysis furnace. Flue gases of different temperatures are respectively introduced into the heat exchange tubes for drying and pyrolysis of domestic garbage. During the drying stage, the moisture in the garbage is heated and evaporated by the flue gas. After the garbage is dried, it is switched to flue gas with a higher temperature for pyrolysis of the garbage.

[0044] The top of the pyrolysis furnace is connected to a pyrolysis gas delivery pipeline for delivering the pyrolysis gas. The semi-coke after the reaction is cooled, sieved, and crushed to prepare semi-coke powder for use;

[0045] The interior of the gasifier is composed of multiple small-diameter steel pipes, and adopts an entrained bed structure with high-temperature flue gas external heating. The pyrolysis gas from the pyrolysis furnace carries the semi-coke powder feed, and water vapor is used as a gasifying agent. The gasified gas produced by gasification is separated from the gas and solid after heat exchange and cooling. The gas is purified and used for standby, and the solid is collected and used to prepare other additional products.

[0046] In the gasifier, since the domestic garbage is mixed with kitchen waste and sewage sludge, it contains a high amount of calcium and potassium elements, as well as catalytic metals such as iron, magnesium, and manganese. During the pyrolysis and gasification process, most of these metals will be converted into metal oxides with certain catalytic effects.

[0047] For example, CaO, MgO, etc. When the gasification temperature is higher than 700°C, the presence of these metal oxides is beneficial to increase the yield of combustible gas during the gasification process;

[0048] The heat source required for gasification in the gasifier comes from the high-temperature flue gas generated by the combustion of the combustible gas produced by gasification. After coming out of the gasifier, part of the flue gas is used for heat recovery to generate steam, and part is used for pyrolysis and drying of garbage, as well as air preheating units, etc.

[0049] As a further preferred embodiment of the present invention, the gasifier may preferably be a two-stage (gasification stage and methanation stage) fluidized bed structure, the pyrolysis output gas is used as a carrier to feed the semi-coke powder into the gasifier for gasification reaction, the gasified gas after the reaction enters the methanation stage for methanation reaction under the action of a catalyst, thereby increasing the yield of methane in the output gas, and the heat released by methanation can be recovered and used to prepare the gasification agent water vapor required for the gasification reaction;

[0050] As a further preferred embodiment of the present invention, the catalyst added to the gasification reaction in the gasifier is preferably calcium carbonate or calcium oxide;

[0051] As a further preferred embodiment of the present invention, the water vapor required for the gasification reaction in the gasifier comes from the pyrolysis gas on the one hand, and from the medium-temperature water vapor generated by heat recovery on the other hand;

[0052] Effect verification:

[0053] After drying and pyrolysis of municipal solid waste, the main components of the pyrolysis gas produced are CO and CH4, with a ratio of 1:1. After drying, pyrolysis and gasification, when the gasification temperature is higher than 850℃, the carbon conversion rate can reach more than 99%, and the components of combustible gas (H2, CO, CH4) in the output gas can reach more than 92%, of which the H2 component can reach more than 59%, and the calorific value of the obtained combustible gas can reach 10MJ / Nm 3 above.

[0054] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, and they should be covered by the protection scope of the present invention.

Claims

1. Application of a material pyrolysis and gasification process in the pyrolysis and gasification of municipal solid waste, characterized in that: The process includes preheating, drying, pyrolysis, gasification and heat recovery in sequence, and is characterized in that the process is implemented by a material pyrolysis and gasification system, the system includes a preheating unit, a drying unit, a pyrolysis unit, a gasification unit and a heat recovery unit, the pyrolysis unit includes a pyrolysis furnace, and the gasification unit includes a gasification furnace; The heat source required by the preheating unit is provided by the medium-temperature flue gas greater than 250°C generated by the drying unit; The heat source required by the drying unit and the pyrolysis furnace is provided by the medium-temperature flue gas with a temperature of more than 750°C after gasification in the gasification furnace through external heating; the heat source required by the gasification furnace is provided by the high-temperature flue gas with a temperature of more than 1000°C formed by the combustion of the combustible gas generated by gasification; The medium-temperature flue gas with a temperature of more than 750°C produced by the gasification furnace is heat recovered to produce low-temperature flue gas with a temperature of more than 100°C. After gas-solid separation, the gaseous part of the low-temperature flue gas is purified to become combustible gas, and the solid part is mixed and granulated to produce organic compound fertilizer; The gasification medium required for gasification in the gasifier includes water vapor produced by the drying unit and the pyrolysis furnace, pyrolysis output gas produced by the pyrolysis furnace, and medium-temperature steam produced during heat recovery; The pyrolysis furnace comprises a furnace shell and an inner cylinder, the inner cylinder is used to hold materials, a smoke inlet and outlet and a pyrolysis gas outlet are provided at the top of the furnace shell, and a conversion valve is provided at the smoke inlet and outlet to change the inlet heat source so as to meet the heat required for drying and pyrolysis respectively; a pyrolysis gas delivery pipeline is connected to the top of the pyrolysis furnace to deliver the pyrolysis gas, and the heating smoke is introduced into the jacket of the pyrolysis furnace to dry and pyrolyze the materials; The pyrolysis furnace adopts the form of flue gas external heating. The inner cylinder is filled with materials and then sent into the pyrolysis furnace. Flue gases of different temperatures are introduced respectively for drying and pyrolysis of the materials. During drying, the moisture in the materials is heated and evaporated by the flue gas. After drying, the flue gas of higher temperature is switched to be used for pyrolysis of the materials. The gasifier includes a plurality of small-diameter steel pipes inside, and adopts an entrained bed structure with high-temperature flue gas external heating. The pyrolysis gas from the pyrolysis furnace carries the semi-coke powder feed, and water vapor is used as a gasifying agent. The gasification gas produced by gasification is separated from the gas and solid after heat exchange, and the gas is purified and used for standby use. The solid is collected and granulated for the preparation of other additional products. The heat required for the gasification of the semi-coke powder in the gasifier comes from the high-temperature flue gas generated by the combustion of the combustible gas produced by the gasification. The particle size of the semi-coke powder is 50-100 mesh; the residence time of the semi-coke powder in the gasification furnace is between 0.5-2.0s; the mass ratio of water vapor to material pyrolysis semi-coke is 0.2-1.0; The heat source required for preheating is provided by the medium-temperature flue gas greater than 250°C generated by drying; The heat source required for drying and pyrolysis is provided by the medium-temperature flue gas with a temperature of more than 750°C generated by gasification through external heating; the heat source required for gasification is provided by the high-temperature flue gas with a temperature of more than 1000°C formed by the combustion of the combustible gas generated by gasification; The medium-temperature flue gas with a temperature of more than 750°C generated by gasification is also used to generate low-temperature flue gas with a temperature of more than 100°C after heat recovery. After gas-solid separation of the low-temperature flue gas, the gaseous part is purified to become combustible gas, and the solid part is mixed and granulated to produce high value-added products; The gasification medium required for gasification includes water vapor produced during drying and pyrolysis, pyrolysis gas produced during pyrolysis, and steam produced during heat recovery; Before pyrolysis occurs, superheated steam is discharged. The superheated steam is used to gasify the pyrolysis coke. After the pyrolysis coke is cooled, it is screened and crushed to produce coke powder. The superheated steam generated in the process of preparing the semi-coke powder is used as a conveying medium to convey the semi-coke powder for gasification; The particle size of the semi-coke powder is 50-100 mesh; the residence time of the semi-coke powder in the gasification process is between 0.5-2.0s; the mass ratio of superheated steam to pyrolysis semi-coke is 0.2-1.0; The gasifier comprises a gasification section and a methanation section fluidized bed structure. The pyrolysis product gas is used as a carrier to send the semi-coke powder into the gasification section for gasification reaction. The gasified gas after the reaction enters the methanation section for methanation reaction under the action of a catalyst. The heat released by the methanation is recovered and used to prepare the gasification agent required for the gasification reaction.

2. The use according to claim 1, characterized in that When pyrolysis semi-coke is produced, the pyrolysis semi-coke and coal coke of the material are co-gasified, the reaction temperature is 750-950°C, and the mixing ratio of pyrolysis semi-coke and coal coke is 1:

1.

3. The use according to claim 1, characterized in that In the gasifier, the catalyst added for the gasification reaction includes calcium carbonate or calcium oxide, the added amount CaO / C is 0.5, and the reaction temperature is 750-800°C.

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