Biomass hydrogen-rich gasification process with plasma heat source cooperating with multistage reactant separation and steam regenerative cycle coupling

Abstract

The invention provides a biomass hydrogen-rich gasification process with cooperation of a plasma heat source and multi-stage reactant separation and steam regenerative cycle coupling, and belongs to the technical field of comprehensive utilization of resources. The drying stage, the pyrolysis stage and the gasification stage are respectively completed in three devices. Three separation processes and a steam regenerative cycle process are set in the three stages, and the separation processes and the steam regenerative cycle process are coordinated and consistent. The three separation processes are respectively used for separating reaction unnecessary gas, pyrolysis gas, pyrolysis oil and hydrogen-rich gasification gas; according to the three steam regenerative cycle processes, regenerative cycles of different steps are carried out on steam of different steps. According to the process, stepped heating and stepped regenerative circulation are refined, a three-stage heating process and a two-stage reaction process can be controllably managed, and engineering implementation feasibility is achieved.

Description

Technical Field

[0001] This invention relates to the field of comprehensive resource utilization technology, and in particular to a biomass hydrogen-rich gasification process that couples plasma heat source with multi-stage reactant separation and steam reheat cycle. Background Technology

[0002] Steam gasification technology is widely recognized as a highly promising biomass-to-hydrogen pathway due to its ability to produce high-hydrogen-content syngas. This technology uses steam as a gasifying agent, converting biomass into hydrogen-rich syngas at high temperatures. Subsequent purification and separation processes yield high-purity hydrogen. During steam gasification, steam not only participates in the water-gas shift reaction as a reaction medium but also effectively promotes tar cracking, thereby significantly increasing hydrogen yield.

[0003] Biomass steam gasification is a complex thermochemical process involving multiple interactive reactions. Its core reaction mechanisms include a series of reactions such as biomass pyrolysis, tar cracking, steam reforming, and water-gas shift reaction. These reactions are usually carried out at high temperatures of 700–1000°C in specific gasification reactors (such as top- / bottom-suction fixed beds and fluidized beds); while entrained flow reactors are more suitable for modern subsequent separation, synthesis, and other process steps.

[0004] The efficiency and product composition of biomass steam gasification for hydrogen production are significantly affected by a variety of operating parameters, including: 1) Gasification temperature: Temperature is directly related to reaction kinetics and thermodynamic equilibrium. Studies have shown that within the range of 700~1000°C, hydrogen yield and industrial equipment reliability can be well balanced; 2) Steam to biomass ratio (S / B): This parameter is one of the key factors affecting hydrogen yield. A suitable S / B ratio of 1.2~2.0 can promote water-gas shift reaction and tar steam reforming, but an excessively high S / B ratio will lead to a decrease in system energy efficiency. Therefore, under the S / B condition that meets the reaction requirements and heat carrying requirements, improving energy efficiency has become the core direction of process innovation; 3) Gasification pressure: Atmospheric pressure operation is usually more conducive to obtaining higher hydrogen yield, while pressurized gasification facilitates the utilization and treatment of subsequent syngas. Existing process technologies have not yet achieved the goal of optimizing gasification pressure while simultaneously balancing steam regeneration cycle efficiency and gasification gas-steam separation effect.

[0005] To further improve the techno-economic efficiency of biomass steam gasification for hydrogen production, researchers have developed several innovative processes and system optimization strategies. Firstly, the adsorption-enhanced gasification technology disclosed in existing technology CN202210743867.0 not only significantly improves hydrogen purity but also drastically reduces separation energy consumption, demonstrating excellent energy utilization efficiency. Secondly, chemical looping gasification (CLG) technology, through the cyclic operation of an oxygen carrier between an air reactor, a fuel reactor, and a hydrogen production reactor, achieves efficient biomass gasification and hydrogen production. Under optimized conditions, the system can achieve a syngas yield of 0.98 m³ / kg and an H₂ yield of 0.025 kg / kg, with an efficiency as high as 68.06%. The significant feature of this technology is that it can achieve system self-heating, maintaining the gasification process continuously without external heating, while obtaining high-purity syngas and hydrogen. Thirdly, the biomass staged gasification technology described in existing technologies CN110591743A and CN115974080A implements the pyrolysis and gasification processes in stages. First, the biomass is pyrolyzed to produce coke, and then coke steam is used to gasify and produce hydrogen-rich syngas. At the same time, the combustion of volatiles provides heat and steam for the pyrolysis and gasification processes. The outstanding advantage of this process is that it can inhibit tar formation from the source, making the tar content in the produced gas lower than 20mg / Nm³, while obtaining high-quality syngas with an H2 yield of ≥400L / kg.

[0006] In summary, while basic research on innovative technologies such as adsorption enhancement, catalyst enhancement, and chemical looping gasification is relatively thorough, and some processes are already in the experimental or small-scale pilot stages, their industrial application remains difficult due to factors such as technological complexity, additive lifespan limitations, and economic constraints. Plasma-enhanced treatment technology is largely limited to the field of high-temperature solid waste treatment and has not yet been effectively applied to biomass hydrogen-rich gasification scenarios. Although staged gasification technology has identified key technological directions such as staged gasification and steam recycling, focusing on reducing system energy consumption, it has failed to organically combine staged methods with the characteristics of pyrolysis gasification. Research on cyclic staged design, parameter optimization, and reduction of S / B parameters remains insufficient.

[0007] Based on this, the development of a biomass hydrogen-rich gasification process that couples plasma heat source with multi-stage reactant separation and steam reheat cycle has significant technical value and application implications. Summary of the Invention

[0008] The purpose of this invention is to provide a biomass hydrogen-rich gasification process that combines plasma heat source with multi-stage reactant separation and steam reheating cycle coupling, thereby solving the problems existing in the prior art.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a biomass hydrogen-rich gasification process coupled with plasma heat source, multi-stage reactant separation, and steam regeneration cycle, comprising the following steps: 1) Drying stage: Biomass is added to the cascade air heat exchange drying section and dried using a heating medium to obtain the dried solid product and other products. The other products are washed by the first washing tower to obtain washing gas and washing liquid. The washing liquid is vaporized by the first flash evaporation tower to generate steam, and the washing gas is discharged. 2) Pyrolysis stage: The dried solid product is passed into the stepped steam heat exchange pyrolysis section and pyrolyzed at low temperature using a heating medium to obtain pyrolytic carbon and pyrolysis gas-steam mixture. 3) Gasification stage: Pyrolytic carbon is transported to the fluidized bed gasifier via a pyrolysis gas-steam mixture and gasified with steam to obtain gasification slag and mixed gas. The mixed gas passes through heat exchanger 3, heat exchanger 2, heat exchanger 1 and the third scrubbing tower in sequence. After being scrubbed by the third scrubbing tower, the mixed gas is obtained as hydrogen-rich gasified gas and scrubbing liquid. The scrubbing liquid is gasified by the third flash evaporation tower to generate steam. The obtained steam is heated in two stages by heat exchanger 3 and plasma tower, and then recycled back to the fluidized bed gasifier. Heat exchanger 2 provides heat to the heating medium required for the pyrolysis stage, and heat exchanger 1 provides heat to the heating medium required for the drying stage.

[0010] Preferably, in step 1), the biomass includes straw; The heating medium is a mixture of steam and air, and the temperature of heat exchanger 1 is 160~220℃.

[0011] Preferably, in step 2), the heating medium is steam, and the temperature of heat exchanger 2 is ≤260~350℃.

[0012] Preferably, in step 2), the pyrolysis gas-steam mixture is washed by the second washing tower to obtain pyrolysis gas and washing liquid. The washing liquid is vaporized by the second flash evaporator to generate steam and pyrolysis oil. The pyrolysis gas and steam enter the fluidized bed gasifier.

[0013] Preferably, in step 3), the temperature of the heat exchanger 3 is 500~800℃, and the temperature of the plasma tower is 850~1000℃.

[0014] Preferably, in step 3), oxygen is introduced into the fluidized bed gasifier.

[0015] The beneficial effects of this invention are: The process described in this invention features a three-stage heating reaction (drying stage, pyrolysis stage, and gasification stage), corresponding to a coupling of energy and material flows through a three-stage washing and separation process and a three-stage steam cycle. The washing and separation process is coupled with flash evaporation, compression, and temperature / pressure increases to separate steam from non-condensable gases, thereby obtaining the energy of regenerative steam and products (waste gas, intermediate products, and final products). Plasma is applied in the high-temperature region of the process, enabling electrical energy to be rationally applied as external energy to the reaction process, achieving a synergistic gasification mechanism of heating and activating the reaction. This lays the foundation for green hydrogen and green syngas. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the process flow for Example 1; Figure 2 This is a schematic diagram of the process flow for Example 2; Figure 3 This is a schematic diagram of the process flow for Example 3; Figure 4 This is a schematic diagram of the process flow for Example 4; Figures 1-4 The labels in the attached figures are as follows: 1 is the first compressor, 2 is the first circulating fan, 3 is the second circulating fan, 4 is the first fan, 5 is the second compressor, 6 is the third compressor, and 7 is the second fan. Detailed Implementation

[0018] This invention provides a biomass hydrogen-rich gasification process coupled with plasma heat source, multi-stage reactant separation, and steam regeneration cycle, comprising the following steps: 1) Drying stage: Biomass is added to the cascade air heat exchange drying section and dried using a heating medium to obtain the dried solid product and other products. The other products are washed by the first washing tower to obtain washing gas and washing liquid. The washing liquid is vaporized by the first flash evaporation tower to generate steam, and the washing gas is discharged. 2) Pyrolysis stage: The dried solid product is passed into the stepped steam heat exchange pyrolysis section and pyrolyzed at low temperature using a heating medium to obtain pyrolytic carbon and pyrolysis gas-steam mixture. 3) Gasification stage: Pyrolytic carbon is transported to the fluidized bed gasifier via a pyrolysis gas-steam mixture and gasified with steam to obtain gasification slag and mixed gas. The mixed gas passes through heat exchanger 3, heat exchanger 2, heat exchanger 1 and the third scrubbing tower in sequence. After being scrubbed by the third scrubbing tower, the mixed gas is obtained as hydrogen-rich gasified gas and scrubbing liquid. The scrubbing liquid is gasified by the third flash evaporation tower to generate steam. The obtained steam is heated in two stages by heat exchanger 3 and plasma tower, and then recycled back to the fluidized bed gasifier. Heat exchanger 2 provides heat to the heating medium required for the pyrolysis stage, and heat exchanger 1 provides heat to the heating medium required for the drying stage.

[0019] In this invention, in step 1), the biomass preferably includes straw; The heating medium is preferably a mixture of steam and air, and the temperature of the heat exchanger 1 is preferably 160~220℃, more preferably 170~210℃, and even more preferably 180~200℃.

[0020] In this invention, in step 1), the particle size of the biomass is preferably 30-80 mm, more preferably 30-50 mm, and even more preferably 50 mm; the moisture content of the product obtained after the drying stage of the biomass is preferably <5%, more preferably <4%, and even more preferably <3%; the heating medium is powered by a circulating fan and obtains heat from the heat exchanger 1; the obtained steam is delivered to the system by the compressor 6 to replenish the steam in the drying stage and the pyrolysis stage.

[0021] In this invention, the drying stage realizes the first separation process of extracting steam through a dry humid air medium and the first process of steam reheating cycle.

[0022] In this invention, in step 1), the remaining products are a mixture of steam and air gas and moisture generated during the drying process.

[0023] In this invention, in step 2), the heating medium is preferably steam, and the temperature of the heat exchanger 2 is preferably 260~350℃, more preferably 180~340℃, and even more preferably 300~320℃.

[0024] In this invention, the temperature of the pyrolysis stage is ≤300℃, which can increase the carbon yield, reduce the gas evolution rate and reduce the tar content, which is conducive to the long-term stable operation of the system and maximizes the amount of pyrolyzed carbon entering the fluidized bed gasifier.

[0025] In this invention, the setting of the pyrolysis temperature in the pyrolysis stage has two significant advantages: first, it can obtain a high carbon yield and energy yield (about 80%); second, the gas evolution is generally less than 5%, and there is basically no tar.

[0026] In this invention, in step 2), the heating medium is powered by a circulating fan and the heat source is provided by a heat exchanger 2.

[0027] In this invention, in step 2), the pyrolysis gas-steam mixture is washed by the second washing tower to obtain pyrolysis gas and washing liquid. The washing liquid is vaporized by the second flash evaporation tower to generate steam and pyrolysis oil. The pyrolysis gas and steam enter the fluidized bed gasifier.

[0028] In this invention, step 2) completes the second separation process of separating pyrolysis gas, pyrolysis oil and steam, and the second cycle process of steam reheating.

[0029] In this invention, in step 3), the temperature of the heat exchanger 3 is preferably 500~800℃, more preferably 550~750℃, and even more preferably 600~700℃, and the temperature of the plasma tower is preferably 850~1000℃, more preferably 880~980℃, and even more preferably 900~950℃.

[0030] In this invention, in step 3), oxygen is introduced into the fluidized bed gasifier.

[0031] In this invention, the purpose of introducing oxygen in step 3) is to better coordinate the composition of the reaction products with the temperature level and heat required for the reaction, and to serve as a means of raising and regulating the temperature, thereby increasing the flexibility of the gasification operation.

[0032] In this invention, the gasification stage includes the gasification reaction of water vapor, the reforming reaction, and the polar ions excited by plasma. These reactions accelerate the gasification rate, reduce the gasification temperature, and increase the hydrogen production rate. The resulting synergistic reaction mechanism overcomes the constraints of the S / B ratio on the gasification reaction and hydrogen production rate, providing convenience for process design and industrialization.

[0033] In this invention, the gasification stage realizes the third separation process of steam and gasified hydrogen-rich gas and the third regenerative cycle process of steam.

[0034] In this invention, the drying, pyrolysis, and gasification stages are completed in three separate pieces of equipment. Three separation processes and a steam regeneration cycle are incorporated into each of the three stages, with the separation processes and steam regeneration cycle working in tandem. The three separation processes separate non-reactive gases, pyrolysis gas and pyrolysis oil, and hydrogen-rich gasification gas, respectively. The three steam regeneration cycle processes implement different stages of regeneration cycles for the steam at different stages. This process refines the staged heating and staged regeneration cycles, enabling controllable management of the three-stage heating process and the two-stage reaction process, thus demonstrating engineering feasibility.

[0035] In this invention, all three stages are heated by steam, and each stage establishes a separation and circulation of the heating medium: in the drying stage, the steam is washed and flashed to recover low-pressure steam and separate non-steam gas for discharge; in the pyrolysis stage, the steam medium is washed and flashed to recover slightly higher-pressure steam and separate non-pyrolysis gas or tar (this step can be omitted at low temperatures); in the gasification stage, the steam is washed and flashed to recover high-pressure steam and hydrogen-rich gas.

[0036] In this invention, the process is divided into a pyrolysis reaction section and a gasification reaction section based on the chemical reaction process. The purpose of the pyrolysis reaction is to pyrolyze biomass into charcoal, homogenizing various types of biomass with different forms and energy densities, and making them into high-density powder, thus providing engineerable conveying and reaction conditions for high-pressure gasification in the fluidized bed gasifier. The purpose of setting up a separate gasification stage is to implement high-pressure gasification, providing convenient conditions for subsequent separation, purification, and synthesis processes.

[0037] In this invention, electrical energy serves as the sole external heat source for the process. Since the electrical energy originates from green electricity, the hydrogen produced by this process is green hydrogen. Using the product of this process as raw material, the methanol produced in subsequent processes is green methanol. Ionized steam, accompanied by pyrolytic carbon, undergoes a gasification reaction in a fluidized bed gasifier, generating a gas with a high hydrogen content.

[0038] In this invention, in the plasma tower, electrical energy generates plasma through power supply electrodes and is applied to high-temperature steam. This invention has three plasma generation methods: arc plasma, which ionizes gas through a high-temperature arc generated between graphite or metal electrodes; inductively coupled plasma, which uses a high-frequency electromagnetic field to induce eddy currents to ionize gas, without internal electrodes; and microwave plasma, which generates plasma through microwave energy coupling.

[0039] In this invention, electrical energy is added to steam in the form of plasma and fed into the fluidized bed gasifier, simultaneously providing heat energy and stimulating the gasification reaction. The mixture of high-temperature hydrogen-rich gas discharged from the gasifier and steam undergoes three-stage heat exchange to supply the heat energy required for pyrolysis, drying, and gasification, and is distributed to the three heating stages in the form of steam reheating cycle.

[0040] In this invention, the steam is derived from a hot gas medium used to wash and heat the washing liquid, which is then flash-evaporated and compressed to obtain the desired steam. This steam originates from water vapor generated during biomass drying or reaction, and also includes heat recovery from the system's cooling water.

[0041] The washing tower described in this invention not only recovers heat but also has the function of gas separation: after washing, the remaining products obtained in the drying stage are discharged as air-based non-condensable gases, which basically eliminates the retention of N2 in the system and avoids affecting the subsequent separation of hydrogen-rich gases; in the pyrolysis stage, the washing of the pyrolysis gas-steam mixture results in non-condensable gases, mainly pyrolysis gas or pyrolysis oil, which are recovered for other uses or sent to the gasifier for reforming; in the gasification stage, after washing, the mixed gas produced by the gasifier mainly consists of reaction products.

[0042] In this invention, the drying and pyrolysis stages are performed using atmospheric pressure chain grate equipment, and the gasification stage is performed using high pressure fluidized bed equipment. The equipment is highly industrialized and mature.

[0043] The process described in this invention is mainly applied to the hydrogen-rich gasification of biomass, but it is also applicable to the hydrogen-rich gasification of other organic wastes.

[0044] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0045] Example 1

[0046] Coarsely crushed straw (6) with a particle size of 30-80mm enters the stepped heating and drying section, where it is heated to 160-200℃ with a moisture content of less than 5%. The heating medium in the drying section is a mixture of steam and air, powered by the first circulating fan 2, and the heat is obtained by the heat exchanger 1. The remaining products are washed and purified to obtain washing gas (4), which is discharged by the second fan 7. The heated washing liquid flows to the first flash evaporator for vaporization, generating steam, which is then delivered to the system by the third compressor 6 to replenish the steam in the drying and pyrolysis sections.

[0047] After drying, the solid product falls into the pyrolysis section of a stepped steam heat exchanger. The pyrolysis temperature is 260~300℃, and the heating medium is steam, powered by the second circulating fan 3 and heated by the heat exchanger 2. The pyrolysis gas-steam mixture obtained from pyrolysis enters a scrubbing tower for washing and cooling, separating pyrolysis gas and pyrolysis oil. The pyrolysis gas is sent to the gasifier by the first fan 4; the scrubbing liquid is heated and then enters a flash evaporator for gasification, producing steam and pyrolysis oil. The pyrolysis oil ③ is collected for other uses, and the steam is sent back to the system by the second compressor 5.

[0048] Pyrolytic char is transported to the fluidized bed gasifier via pyrolysis gas and steam. The circulating steam is preheated to 600°C via heat exchanger 3, then sent to a plasma tower for further heating to 900°C, before entering the fluidized bed gasifier to fully mix and gasify with the pyrolytic char. After gasification, gasification slag and mixed gas are separated. Gasification slag ② is discharged, while the mixed gas exits the gasifier and sequentially passes through heat exchangers 3, 2, and 1 to release heat, distributing it to the gasification, pyrolysis, and drying stages for heating the heating medium. The gas then enters a scrubbing tower to separate hydrogen-rich gasified gas ①, which is then sent out of the system. The heated scrubbing liquid enters a flash evaporator for gasification to obtain steam, which is then compressed by the first compressor 1, heated in two stages by heat exchanger 3 and plasma, and then recycled back to the gasifier.

[0049] Example 2

[0050] The process described in Example 1, which involves "the pyrolysis gas-steam mixture obtained from pyrolysis is fed into a washing tower for washing and cooling to separate pyrolysis gas and pyrolysis oil, and the pyrolysis gas is sent into a gasifier by the first blower 4; the washing liquid is heated and then fed into a flash evaporator for gasification to produce steam and pyrolysis oil, the pyrolysis oil ③ is collected for other uses, and the steam is sent back to the system by the second compressor 5", is replaced with "the pyrolysis gas-steam mixture obtained from pyrolysis is sent into a gasifier by the first blower 4", with other processes remaining the same as in Example 1.

[0051] Example 3

[0052] Oxygen was introduced into the fluidized bed gasifier in Example 1, and the other processes were the same as in Example 1.

[0053] Example 4

[0054] Oxygen was introduced into the fluidized bed gasifier in Example 2, and the other processes were the same as in Example 2.

[0055] In this invention, in Example 2, the pyrolysis gas-steam mixture consists of CO2, CO and steam. The pyrolysis gas-steam mixture is pressurized and sent to the gasifier, which simplifies the process and has virtually no impact on the overall gasification product, but reduces investment.

[0056] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A biomass hydrogen-rich gasification process coupled with plasma heat source, multi-stage reactant separation, and steam reheat cycle, characterized in that, Includes the following steps: 1) Drying stage: Biomass is added to the cascade air heat exchange drying section and dried using a heating medium to obtain dried solid products and other products. The other products are washed by the first washing tower to obtain washing gas and washing liquid. The washing liquid is vaporized by the first flash evaporation tower to generate steam, and the washing gas is discharged. 2) Pyrolysis stage: The dried solid product is passed into the stepped steam heat exchange pyrolysis section and pyrolyzed at low temperature using a heating medium to obtain pyrolytic carbon and pyrolysis gas-steam mixture. 3) Gasification stage: Pyrolytic carbon is transported to the fluidized bed gasifier via a pyrolysis gas-steam mixture and gasified with steam to obtain gasification slag and mixed gas. The mixed gas passes through heat exchanger 3, heat exchanger 2, heat exchanger 1 and the third scrubbing tower in sequence. After being scrubbed by the third scrubbing tower, the mixed gas is obtained as hydrogen-rich gasified gas and scrubbing liquid. The scrubbing liquid is gasified by the third flash evaporation tower to generate steam. The obtained steam is heated in two stages by heat exchanger 3 and plasma tower, and then recycled back to the fluidized bed gasifier. Heat exchanger 2 provides heat to the heating medium required for the pyrolysis stage, and heat exchanger 1 provides heat to the heating medium required for the drying stage.

2. The biomass hydrogen-rich gasification process according to claim 1, characterized in that, In step 1), biomass includes straw; The heating medium is a mixture of steam and air, and the temperature of heat exchanger 1 is 160~220℃.

3. The biomass hydrogen-rich gasification process according to claim 1, characterized in that, In step 2), the heating medium is steam, and the temperature of heat exchanger 2 is 260~350℃.

4. The biomass hydrogen-rich gasification process according to claim 1 or 3, characterized in that, In step 2), the pyrolysis gas-steam mixture is washed by the second washing tower to obtain pyrolysis gas and washing liquid. The washing liquid is vaporized by the second flash evaporation tower to produce steam and pyrolysis oil. The pyrolysis gas and steam enter the fluidized bed gasifier.

5. The biomass hydrogen-rich gasification process according to claim 1, characterized in that, In step 3), the temperature of heat exchanger 3 is 500~800℃, and the temperature of plasma tower is 850~1000℃.

6. The biomass hydrogen-rich gasification process according to claim 1 or 5, characterized in that, In step 3), oxygen is introduced into the fluidized bed gasifier.

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