CN100459267C - Biomass hydrogen energy electric generation method - Google Patents

Abstract

A biomass hydrogen energy power generation method, characterized in that the biomass is converted into clean high-temperature hydrogen-rich gas through a biomass thermochemical hydrogen production method, and the high-temperature hydrogen-rich gas is directly applied to a molten carbonate fuel cell to generate electricity without purification Production.

Description

Biomass Hydrogen Power Generation Method

technical field

The invention relates to a method for generating electricity with biomass hydrogen energy.

Background technique

With the shortage of fossil fuels and the increasingly tense energy supply situation, the development of biomass energy has attracted great attention. Biomass energy has the characteristics of abundant resources, huge reserves and renewable. Biomass power generation technology uses waste biomass resources such as straw to produce green power, which is of great significance for alleviating the tension in power supply and ensuring energy security. The currently developed biomass power generation technologies mainly include biomass direct combustion power generation and gasification power generation. Direct combustion power generation uses biomass as boiler fuel to produce superheated steam, and realizes power production through steam turbines and gas turbines; gasification power generation uses gasifiers in the form of fluidized beds and fixed beds to convert biomass raw materials into low-to-medium calorific value gas, This is then converted to electricity in internal combustion engines, gas turbines. For example, the patent "Method for Power Generation Using Plant Straw Biomass" (01129656.9) discloses a method for generating electricity using 80%-90% plant straw biomass. cracked gas, and then the mixed cracked gas is purified, tar-removed, etc., and then supplied to the internal combustion engine for power generation, or the mixed cracked gas is directly sent to the combustion zone at 800-1000°C to generate combustion gas, which is passed through the combustion The gas drives the gas turbine to drive the generator to generate electricity, or the mixed cracked gas is directly sent to the boiler of the thermal power station for combustion to replace coal and oil for electricity generation. Both direct combustion power generation and gasification power generation technologies have been applied in industry, but the ubiquitous problems of low process energy conversion rate and high cost of collection, storage and transportation of biomass raw materials in large-scale utilization still cannot be ignored. Combining biomass power generation technology with hydrogen energy technology, using hydrogen energy as the intermediary of biomass power generation, combined with the high efficiency and flexibility of fuel cells, will realize the clean and efficient conversion of biomass to electricity. The fuel cell system is not restricted by the second law of thermodynamics, and its power generation efficiency is much higher than that of conventional thermal power generation and internal combustion engine power generation. Therefore, biomass hydrogen power generation technology has broad application prospects. Invention patent "Using crop biomass to produce hydrogen and hydrogen power generation device" (200410005733.0), which discloses a method of using crop straw and other biomass to produce hydrogen through microbial decomposition, and through biomass decomposition, fermentation to produce hydrogen, and after the reaction liquid Treatment, water sealing, gas elution, gas drying, hydrogen storage and fuel cell device conversion to electricity. Microbial transformation method, which uses decomposing microorganisms to decompose various agricultural straws and starchy substances into sugar substances, and uses microorganisms to ferment sugar substances to produce hydrogen; This leads to low utilization of biomass raw materials, and the hydrogen production process is limited by raw materials; hydrogen needs to be purified, and then pure hydrogen is used for low-temperature proton membrane fuel cell power generation.

Contents of the invention

The purpose of the present invention is to provide a method for biomass hydrogen power generation with higher raw material utilization rate and higher energy conversion efficiency. The biomass hydrogen energy power generation method proposed by the present invention converts biomass into clean hydrogen-rich gas through advanced biomass thermochemical hydrogen production technology, and the high-temperature hydrogen-rich gas can be directly used for molten carbonate fuel without purification Batteries, to achieve electricity production, can obtain higher energy conversion efficiency, and at the same time, the adaptability of raw materials is also greatly expanded.

The scheme of the present invention is achieved through the following steps: a biomass hydrogen energy generation method, which is characterized in that biomass is converted into clean high-temperature hydrogen-rich gas through a biomass thermochemical hydrogen production method, and the high-temperature hydrogen-rich gas does not need to be purified Direct application to molten carbonate fuel cells for electricity production.

The specific feature of the present invention is that the biomass thermochemical hydrogen production method is to convert the biomass raw material into gas phase products and carbon residues by pyrolysis at a temperature of 550-650 °C under the condition of air isolation; After separation in the medium, it is removed from the reaction system, and the heat is obtained by combustion for the energy loss of the biomass hydrogen power generation process; the gas phase products generated after pyrolysis are cracked at 800-950°C, and combined with the dolomite catalyst and water vapor The role is to realize the cracking and reforming of gas phase products, cracking and reforming the tar of heavy hydrocarbon components with relatively large molecular weight into hydrogen, methane and other light hydrocarbons, eliminating tar and reducing the content of methane and other hydrocarbons, and increasing the concentration of gas products. Hydrogen content and output, prepare a gas product with a hydrogen volume content of 30%-55%, cool it down to 300°C, perform hot filtration and desulfurization, and send the gas product to the carbon monoxide shift reactor after removing impurities, where the carbon monoxide shift catalyst Carbon monoxide is further converted into hydrogen under the action of water vapor, and the obtained hydrogen-rich gas is directly used in molten carbonate fuel cells to generate electricity through the electrochemical process inside the fuel cell system.

The biomass thermochemical hydrogen production method is to send biomass raw materials such as straws with a water content of 10%-20% into the pyrolysis reactor quantitatively after being crushed; The rear part of the pyrolysis reactor is indirectly heated while being conveyed. During the conveying process, biomass pyrolysis occurs under the condition of isolated air. The temperature of the pyrolysis reactor is adjusted by the external flue gas heating and control device. The decomposition reaction time is at least 5 minutes, and the components accounting for 60-75% of the weight of the biomass raw material are volatilized and analyzed to become gas phase products. The gas phase products include hydrogen, carbon monoxide, carbon dioxide, methane, etc. Macromolecular compounds that condense into liquids;

At the rear of the pyrolysis reactor, the biomass pyrolysis solid phase product is separated from the gas phase product; the gas phase product enters the dust collector to remove the particulate impurities in the gas phase product; the solid phase product enters the carbon residue collection box and is sent into the The residual carbon combustion device achieves good combustion by adjusting the air supply, and obtains high-temperature flue gas, which is used to maintain the temperature level of the pyrolysis reaction and cracking reaction part and the energy required for the production of superheated steam;

The pyrolysis gas phase product after dedusting enters the cracking reactor, and the dolomite catalyst is filled in the cracking reactor, and superheated steam (140 ° C) is passed through. The addition of steam is 10-30% of the biomass quality, and according to Adjust the characteristics of the biomass raw material; use the flue gas heating and control device to adjust the temperature of the cracker, and crack at a temperature of 800-950 ° C. The reaction time is at least 3 seconds, and the heavy hydrocarbon components with larger molecular weight (tar ) is cracked into hydrogen, methane and other light hydrocarbons, combined with steam reforming of cracked products to realize the conversion of methane and other hydrocarbons, increase hydrogen production, eliminate tar, increase gas production and hydrogen content of gas, and obtain hydrogen-rich gas , while reducing carbon deposition and avoiding catalyst deactivation due to carbon deposition.

The beneficial effects of the present invention are as follows: 1. The method of the present invention uses biomass resources such as straws as raw materials, converts them into hydrogen-rich gas through pyrolysis combined with cracking methods, and combines high-temperature fuel cells to realize power generation. The energy conversion efficiency of the gas power generation part is More than 50%, compared with the traditional biomass combustion gasification power generation method, it has a higher energy conversion efficiency. 2. The method of pyrolysis combined with cracking to produce hydrogen-rich gas can use various agricultural and forestry wastes such as rice husks, corn stalks, rice stalks, and wheat stalks. It can be used as fertilizer and returned to the field, and the utilization rate of raw materials is high. 3. The hydrogen content in the hydrogen-rich gas is relatively high, which is directly used for high-temperature fuel cell power generation, avoiding the high-cost hydrogen purification process; the high-temperature hydrogen-rich gas produced in the hydrogen production section is directly used in the fuel cell without cooling, which improves the energy Take advantage of the economy. 4. The biomass hydrogen energy power generation system is convenient and flexible, easy to arrange around users, avoids the high cost of raw material collection, storage and transportation in the large-scale utilization of biomass resources, is suitable for the establishment of distributed energy systems, and is suitable for rural areas, forests, etc. Energy development in rural areas, remote mountainous areas, pastoral areas, islands and some areas far away from the grid and rich in biomass resources.

Detailed ways

Biomass raw materials such as straws with a water content of 10-20% are crushed and pretreated, and then quantitatively sent to a pyrolysis reactor. During the transportation of biomass raw materials in the pyrolyzer, the pyrolysis reaction occurs under the condition of isolated air. The pyrolysis temperature is 550-650°C, and the pyrolysis reaction time is at least 5 minutes. By monitoring the temperature and adjusting the flue gas heating device accordingly The load realizes the regulation and control of the pyrolysis reaction temperature. After pyrolysis, the biomass raw material is converted into gas phase and solid phase products. The gas phase pyrolysis products include hydrogen, carbon monoxide, carbon dioxide, methane and other gases that are not condensed at normal temperature, and tar and other macromolecular hydrocarbons that condense into liquid at normal temperature. The basic pyrolysis reaction is:

At the rear of the pyrolyzer, the pyrolysis solid phase products are separated from the gas phase products. The gas phase product enters the dust collector to remove the particulate impurities in the gas phase product. The solid phase product enters the carbon residue collection box, and is sent to the carbon residue burner through the conveying mechanism, and the air supply is adjusted to achieve good combustion, and the high-temperature flue gas at about 1000°C is obtained, and sent to the pyrolyzer, cracker, carbon monoxide converter, etc. Energy-consuming equipment. The residual carbon combustion process only produces biomass ash accounting for 5-15% of the mass of biomass raw materials, which can be used as fertilizer and returned to the field.

The pyrolysis gas phase product after dedusting enters the cracker, and a cracking reaction occurs under the action of dolomite catalyst and superheated steam (above 140°C), and the heavy hydrocarbon component (tar) with a large molecular weight is cracked into light products. Combined with the steam reforming of cracking products, the conversion of methane and other hydrocarbons can be realized, the heavy hydrocarbon components can be eliminated, and the gas output and hydrogen content in the gas can be increased. The pyrolysis reaction temperature is 800-950°C, and the reaction time is at least 3 seconds. The temperature of the pyrolysis reaction is controlled by monitoring the temperature and adjusting the load of the flue gas heating device accordingly. The amount of water vapor added is 10-30% of the biomass mass, and Adjust according to the characteristics of biomass raw materials. The main reactions that occur during the cracking process are:

一氧化碳变换反应

carbon monoxide shift reaction

甲烷重整反应

methane reforming reaction

水煤气反应

water gas reaction

The product gas from the cracker passes through the water-cooled heat recovery device to reduce the gas flow temperature to about 300°C to meet the temperature level required for high-temperature filtration and desulfurization. The hot water obtained from heat recovery can be sent to the superheated steam generator.

The product gas at about 300°C enters the high-temperature filter to filter the particulate impurities that may be generated during the reaction process. The filtered gas product enters the desulfurizer, and the trace sulfur that may be contained in the gas flow is removed under the action of a zinc oxide desulfurizer at a temperature of about 250-350 °C.

水煤气反应The gas product after desulfurization enters the carbon monoxide shift reactor, using a water gas shift reaction catalyst, the reaction temperature is 300-400 ° C, and the superheated steam above 140 ° C is introduced, and the amount of water vapor added is adjusted according to the gas composition to convert the carbon monoxide in the gas flow For hydrogen and carbon dioxide, reduce the content of carbon monoxide and increase the output of hydrogen to obtain a hydrogen-rich gas with a volume content of hydrogen of more than 60%, a volume content of carbon monoxide of less than 3%, and a volume content of methane of less than 2%, which can meet the requirements of molten carbonate fuel cell reaction need. The main reactions of this process are:

water gas reaction

The hydrogen-rich gas at 300-400°C is sent to the anode of the molten carbonate fuel cell, and the mixture of air and carbon dioxide is sent to the cathode of the fuel cell. At about 600-650°C, the molten carbonate is used as the electrolyte to pass through the fuel cell. The electrochemical process inside the system generates electricity and outputs it externally. The energy conversion efficiency of the gas-fired power generation part is above 50%, far exceeding the power generation efficiency of internal combustion engines, steam turbines, and gas turbines generally not exceeding 40% in combustion and gasification power generation. The main reactions of this process are:

Cathode: O ₂ +2CO ₂ +4e ^- → 2CO ₃ ^2-

Anode: 2H ₂ +2CO ₃ ^2- → 2CO ₂ +2H ₂ O+4e ^-

Total reaction: O ₂ +2H ₂ →2H ₂ O

The high-temperature exhaust gas (above 500°C) of the fuel cell can be discharged after recovering part of the heat energy through the water-cooled waste heat recovery device, and the hot water generated can be sent to the superheated steam generator to generate superheated steam, or provide part of the hot water for heating purposes.

Description of drawings

Fig. 1 is a block diagram of a method for generating electricity by biomass hydrogen energy.

Claims (5)

1. A biomass hydrogen energy power generation method, which is characterized in that biomass is converted into clean high-temperature hydrogen-rich gas through a biomass thermochemical hydrogen production method, and the high-temperature hydrogen-rich gas is directly applied to a molten carbonate fuel cell without purification enable electricity production; The biomass thermochemical hydrogen production method is to convert biomass raw materials into gas phase products and carbon residues by pyrolysis at a temperature of 550-650 ° C under air-isolated conditions; the carbon residues are separated from the gas phase products and then removed from the reaction system. The heat obtained by combustion is used for energy loss in the process of biomass hydrogen power generation; the gas phase products produced after pyrolysis are cracked at 800-950 °C, and the gas phase products are cracked and reformed in combination with the action of dolomite catalyst and water vapor. Rectification, splitting and reforming heavy hydrocarbons with larger molecular weights into hydrogen, methane and other light hydrocarbons, eliminating tar and reducing hydrocarbon content, increasing hydrogen content and output in gas products, and preparing hydrogen volume content up to 30%-55% hydrogen-rich gas product, cooled to 300°C, hot-state filtration and desulfurization, after removing impurities, the gas product is sent to the carbon monoxide shift reactor, and carbon monoxide is further converted under the action of carbon monoxide shift catalyst and water vapor It is a high-temperature hydrogen-rich gas. 2. The biomass hydrogen energy power generation method according to claim 1, characterized in that the biomass thermochemical hydrogen production method is to quantitatively send the biomass raw material with a water content of 10% to 20% into the pyrolysis reaction after crushing Biomass raw material is indirectly heated while being conveyed to the rear of the pyrolysis reactor by a screw conveying device inside the pyrolysis reactor. During the transportation process, biomass pyrolysis occurs under the condition of isolated air, and the temperature of the pyrolysis reactor is controlled by the external The flue gas heating and control device is adjusted, the pyrolysis temperature is 550-650°C, the pyrolysis reaction time is at least 5 minutes, and the components accounting for 60-75% of the weight of the biomass raw material are volatilized and analyzed to become gas phase products. The gas phase products include normal temperature Non-condensable gases and macromolecular compounds that condense into liquids at room temperature; At the rear of the pyrolysis reactor, the biomass pyrolysis solid phase product is separated from the gas phase product; the gas phase product enters the dust collector to remove the particulate impurities in the gas phase product; the solid phase product enters the carbon residue collection box and is sent into the Carbon residue burner, achieve good combustion by adjusting the air supply, and obtain high-temperature flue gas, which is used to maintain the temperature level of pyrolysis reaction, cracking reaction part and the energy required for the production of superheated steam; The pyrolysis gas phase product after dedusting enters the cracking reactor, which is filled with dolomite catalyst and fed with superheated steam at 140°C. The amount of steam added is 10-30% of the biomass mass, and according to the biomass The characteristics of the raw materials are adjusted; the temperature of the cracker is adjusted by the flue gas heating and control device, and the cracking is carried out at a temperature of 800-950 ° C. The reaction time is at least 3 seconds, and the heavy hydrocarbon component tar with a large molecular weight is cracked into Hydrogen, methane and other light hydrocarbons, combined with steam reforming of cracked products, realize the conversion of hydrocarbons, increase hydrogen production, eliminate tar, increase gas production and hydrogen content of gas, and obtain hydrogen-rich gas products. 3. The biomass hydrogen power generation method according to claim 2, characterized in that the pyrolysis temperature is 600-650°C, and the cracking temperature is 850-900°C. 4. The biomass hydrogen power generation method according to claim 2, characterized in that the pyrolysis reaction time is 6-8 minutes, and the cracking reaction time is 3-6 seconds. 5. The biomass hydrogen power generation method according to claim 2, characterized in that the temperature of the hydrogen-rich gas entering the molten carbonate fuel cell is 300-400°C, the hydrogen volume content in the gas is above 60%, and the carbon monoxide The volume content is less than 3%, and the volume content of methane is less than 2%.

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