CN116207310A - SOFC system for recycling tail gas and starting method - Google Patents

SOFC system for recycling tail gas and starting method Download PDF

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Publication number
CN116207310A
CN116207310A CN202310271740.8A CN202310271740A CN116207310A CN 116207310 A CN116207310 A CN 116207310A CN 202310271740 A CN202310271740 A CN 202310271740A CN 116207310 A CN116207310 A CN 116207310A
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group
electric
stacks
tail gas
reformer
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王世忠
舒正龙
张亚鹏
张华森
侯建钟
陈鹏燕
王云
陈罗倩雯
陈翠容
李云
陈启章
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Sinocat Environmental Technology Co Ltd
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Sinocat Environmental Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
    • H01M8/0662—Treatment of gaseous reactants or gaseous residues, e.g. cleaning
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/043—Processes for controlling fuel cells or fuel cell systems applied during specific periods
    • H01M8/04302—Processes for controlling fuel cells or fuel cell systems applied during specific periods applied during start-up
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
    • H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
    • H01M8/0612—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants from carbon-containing material
    • H01M8/0618—Reforming processes, e.g. autothermal, partial oxidation or steam reforming
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

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  • Chemical Kinetics & Catalysis (AREA)
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  • General Chemical & Material Sciences (AREA)
  • Fuel Cell (AREA)

Abstract

The invention discloses an SOFC system for recycling tail gas and a starting method, wherein the SOFC system comprises the following components: a first set of stacks, a second set of stacks, a heat exchanger, a reformer, an evaporator, and a tail gas burner; the system not only optimizes the connection and arrangement modes of all components in the SOFC system, but also pointedly distinguishes the electric pile according to functions and actions, and limits the starting sequence, so that the fuel in the anode tail gas of the electric pile in the SOFC system can be fully recycled, the utilization rate of the fuel in the electric pile is obviously improved, and after the electric pile normally operates, the water vapor required by fuel reforming is directly provided through the high-temperature anode tail gas, and the circulation processes of water cooling, separation and re-evaporation in the tail gas and a heat exchange system are not required, thereby obviously reducing the energy consumption, the system complexity and the product manufacturing cost, and being more beneficial to the large-scale popularization and application of the SOFC system.

Description

SOFC system for recycling tail gas and starting method
Technical Field
The invention relates to the field of SOFC systems, in particular to an SOFC system with tail gas recycling and a starting method.
Background
A solid oxide fuel cell (Solid Oxide Fuel Cell, abbreviated as SOFC) is a novel power generation technology for directly converting chemical energy of fuel into electric energy in an electrochemical reaction mode, and the working temperature is between 500 ℃ and 800 ℃.
The SOFC system mainly comprises an evaporator, a reformer, a galvanic pile, a tail gas burner, a heat exchanger, a waste heat recovery system, an inverter and the like. The evaporator is mainly used for heating and evaporating deionized water to form water vapor; the reformer is mainly used for reforming and converting hydrocarbon fuel such as natural gas, alcohols and the like and steam into mixed gas mainly comprising hydrogen, carbon monoxide and carbon dioxide, so that electrochemical reaction in a pile is facilitated; the burner mainly converts fuel which is not completely reacted in the anode tail gas into heat and provides heat energy for the system; the heat exchanger exchanges heat energy, and the high-temperature heat source is used for heating the low-temperature medium.
The tail gas of the anode of the SOFC system electric pile contains residual CO and H 2 Therefore, the tail gas of the anode of the electric pile is available for recyclingSex; particularly, the high-temperature vapor contained in the tail gas can be completely recycled without cooling separation (the process of cooling and recycling the vapor in the anode tail gas to the evaporator in the prior art), and is directly recycled in the form of high-temperature vapor without passing through the evaporator, so that the energy loss in the vapor recycling process is reduced.
In the prior art, related technologies for recycling anode tail gas to a reformer and a next-stage electric pile exist, for example, patent CN113540539A discloses an SOFC system combining a partial oxidation reforming device and a steam reforming device, and the system reforms tail gas of an anode of a previous-stage electric pile with natural gas in a mixed manner through the series connection of the electric pile and the reformer to become air inlet of the next-stage electric pile, so that the recycling of the tail gas of the electric pile is realized, the utilization rate of the natural gas is improved, high-temperature steam is effectively utilized, and the energy consumption is reduced; however, because the connection and arrangement modes of all the components in the system are complex, a plurality of reformers are needed to realize the operation of the SOFC system, so that the SOFC system has complex structure, high manufacturing cost and small improvement of fuel utilization rate, and when the electric pile normally operates, a partial oxidation reaction CPOX device is needed to be reserved to ensure the normal operation of the electric pile, thereby being unfavorable for commercialization and miniaturization of the SOFC system and influencing the improvement of electric efficiency.
The gas composition after methane steam reforming depends on various factors such as water-carbon ratio, reaction temperature, catalyst and the like. As can be seen from the equations (1) - (3) for methane reforming and oxidation,
CH 4 + 2H 2 O = CO 2 + 4H 2 (1)
4H 2 + 2O 2 = 4H 2 O (2)
CH 4 + 2O 2 = CO 2 + 2H 2 O (3)
in steam reforming of methane alone, CO 2 25% by weight, whereas in an infinite number of multistage cycles, CO 2 Will be determined primarily by the hydrocarbon ratio of methane, which is about 33%. According to well known theory, high concentration CO 2 Can dilute fuel and stabilize fuel oxidation kinetics and nickel anodeThe performance may be affected and thus there is a potential risk of multi-stage cycling. In order to reduce the water content in the tail gas and improve the fuel content as much as possible, theoretically, the next-stage electric pile needs to use twice the methane amount, i.e. the power of the next-stage electric pile is optimally 2 times that of the upper-stage electric pile. Considering the total power comprising the upper-level stacks, in the case of the two-level stacks, only about 33% of the exhaust gas is recycled. With the increase of the number of the galvanic pile stages, the tail gas recycling rate is increased, but the system is complicated, and the cost is high.
Disclosure of Invention
The invention aims to overcome the defects of lower fuel utilization rate, more components and complex structure of the conventional SOFC system for recycling tail gas, and provides the SOFC system for recycling tail gas and a starting method thereof.
In order to achieve the above object, the present invention provides an SOFC system for recycling exhaust gas, including: a first set of stacks, a second set of stacks, a heat exchanger, a reformer, an evaporator, and a tail gas burner;
the output end of the evaporator is connected with the input end of the reformer;
the output end of the reformer is respectively connected with the anode input ends of the first group of electric piles and the second group of electric piles, an opening and closing device is arranged between the output end of the reformer and the anode input ends of the first group of electric piles and the second group of electric piles, whether the anode input ends of the first group of electric piles and/or the second group of electric piles are communicated with the output end of the reformer or not can be controlled through the opening and closing device, and the gas flow rate of the reformer input into the first group of electric piles and the second group of electric piles is controlled;
the cathode output ends of the first group of electric stacks and the second group of electric stacks are connected with the input end of the tail gas burner;
the anode output ends of the first group of electric stacks and the second group of electric stacks are simultaneously connected with the input end of the tail gas burner and the input end of the reformer, opening and closing devices are arranged between the anode output ends of the first group of electric stacks and the second group of electric stacks and the input end of the reformer as well as between the anode output ends of the first group of electric stacks and the second group of electric stacks and the input end of the tail gas burner, and the tail gas amount of the anode output ends of the first group of electric stacks and/or the second group of electric stacks entering the reformer and the tail gas burner can be controlled through the opening and closing devices;
the output end of the tail gas burner is connected with the heat input end of the heat exchanger; the heat exchanger is used for preheating fuel gas entering the reformer and/or cathode air entering the first and second stacks, and/or for providing heat for heat absorbing or cryogenic components of the reformer, etc., and/or for providing heat for the second stacks at start-up.
According to the SOFC system capable of recycling tail gas, the connection and arrangement modes of all the components in the SOFC system are optimized, so that the starting sequence of a cell stack is controlled to complete the starting and stable operation of the whole SOFC system, the SOFC system is started in batches, the starting can be completed under less starting energy, part of tail gas generated by the cell stack can be recycled, the utilization rate of the SOFC system to fuel is remarkably improved, the starting system is simplified, and the cost is reduced; in addition, the water vapor balance of the system is completely realized by circulation, and the energy consumption is reduced (the energy loss in the circulation process caused by condensing tail gas to obtain water and then generating water vapor again by heat exchange in the prior art is avoided); after the SOFC system is normally operated, anode tail gas can be recycled to the greatest extent, water balance is realized, energy loss is reduced, and the SOFC system is more beneficial to large-scale popularization and application.
The first group of electric piles are used as starting electric piles of the SOFC system, and after the SOFC system operates normally, the first group of electric piles and the second group of electric piles operate as conventional electric piles of the SOFC system; the number of the electric piles in the first group and the second group of electric piles can be adjusted according to actual conditions, and the number of the electric piles in each group of electric piles can be set arbitrarily according to requirements under the condition that the overall design thought and principle are not influenced. In order to reduce the energy required for starting the pile starting system and during starting, the pile can be further divided into a plurality of groups of piles according to the invention, and multistage starting is carried out.
The heat exchanger in the SOFC system is used for preheating fuel gas entering the reformer and/or cathode air entering the first group of electric stacks and the second group of electric stacks, and simultaneously can also provide heat supply or heat dissipation functions for other devices of the system needing to maintain a specific temperature, such as auxiliary tail gas burner heat dissipation, heat supply for starting of the reformer and the second group of electric stacks, and the like, so that normal operation of the electric stacks is ensured, heat energy is utilized to the greatest extent, and the heat efficiency of the system is improved; the evaporator is used for heating water into water vapor when the galvanic pile is started, providing the water vapor for the reformer, ensuring the normal operation of the galvanic pile, closing the evaporator after the galvanic pile is normally operated, and directly providing the water vapor by anode tail gas; the reformer can reform the input steam, fuel and anode tail gas, so that each component in the mixed gas output by the reformer accords with the optimal proportion, thereby being beneficial to the efficient power generation of a galvanic pile and improving the fuel conversion efficiency; the tail gas burner can convert tail gas which is generated by the anode of the electric pile and does not need to be circulated into heat energy through combustion, and further recycle the generated heat energy through the heat exchanger, so that the fuel energy utilization rate is improved to the greatest extent.
Preferably, the opening and closing device is a high-temperature valve capable of adjusting the flow, such as a high-temperature gas flow valve.
Preferably, the tail gas burner is a catalytic burner, which can completely burn unreacted fuel in the tail gas, release heat energy in the fuel to the greatest extent, and be fully utilized.
Preferably, the tail gas burner, the reformer and the heat exchanger together form an integrated heat exchange module; through modular design, can reduce heat dissipation, improve heat exchange efficiency, simultaneously, reduce occupation space, do benefit to the miniaturization of SOFC system.
Preferably, the first group of electric stacks and the second group of electric stacks together form an SOFC power generation module; through the modularized design, heat dissipation can be reduced, system efficiency is improved, and meanwhile, occupied space is reduced, so that miniaturization of the SOFC system is facilitated.
Preferably, a gas circulation auxiliary device is further arranged between the anode output ends of the first group of electric stacks and the second group of electric stacks and the input end of the reformer; the gas circulation auxiliary device can assist in introducing the tail gas and new fuel at the anode output ends of the first group of electric stacks and/or the second group of electric stacks into the reformer, so that the reformer and water vapor in the tail gas are utilized to reform the fuel, and synthesis gas generated by reforming and the fuel in the tail gas enter the electric stacks to perform electrochemical reaction, thereby better realizing the recycling of the tail gas; more preferably, the gas circulation auxiliary device is an ejector or a high-temperature fan; most preferably, the gas circulation auxiliary device is an ejector; the output port of the ejector is connected with the input end of the reformer, the high-pressure input port of the ejector inputs fuel gas, the low-pressure input port of the ejector is connected with the anode output ends of the first group of electric stacks and the second group of electric stacks, the anode tail gas of the first group of electric stacks and the second group of electric stacks is input, and the pressure of the fuel gas is higher than that of the anode tail gas; through the arrangement of the ejector, the anode tail gas can be better led into the reformer, and the self-circulation of the SOFC system is realized.
Preferably, the output end of the heat exchanger is also connected with a waste heat recovery device; the heat in the tail gas after the heat exchange of the heat exchanger can be recovered through the waste heat recovery device, so that the heat efficiency of the SOFC system can be further improved.
Preferably, the input end of the reformer is also connected with a desulfurizer; the fuel can enter the reformer after being treated by the desulfurizer, so that the influence of sulfur-containing gas on the SOFC system can be reduced, and the service life of the SOFC system is prolonged.
In order to achieve the above object, the present invention further provides a method for starting an SOFC system with tail gas recycling, comprising the following steps:
s1: a starting stage: connecting the first group of electric piles and the reformer, disconnecting the second group of electric piles and the reformer, and closing the gas circulation auxiliary device; the preheating evaporator, the reformer and the first group of electric stacks can adopt the known hot air or electric heating mode; after the first group of electric stacks reach the starting temperature, introducing preheated air, fuel and water vapor, and starting the first group of electric stacks; introducing all anode tail gas of the first group of galvanic piles into a tail gas burner; the heat generated by combustion is used for preheating a second group of electric stacks;
s2: and (3) a transition stage: when the first group of electric stacks are started normally and the second electric stacks reach the starting temperature, anode tail gas of the first group of electric stacks is led into the reformer gradually by adjusting the opening and closing device and the gas circulation auxiliary device; simultaneously, the second group of electric stacks are communicated with the reformer, the introduction amount of the system fuel and air is increased, the amount of water injected into the evaporator is reduced, and the second group of electric stacks are started; introducing all or part of anode tail gas of the second group of electric stacks into a tail gas burner, so that the first group of electric stacks and the second group of electric stacks safely run at the same time;
s3: and (3) a normal working stage: the evaporator is stopped, the gas circulation auxiliary device, the reformer, the fuel and air supply device are dynamically adjusted, the fuel and air input quantity of the system and the ratio of anode tail gas of the first group of electric stacks and the second group of electric stacks to the reformer and the tail gas burner are controlled, the material balance of the inlet and outlet of the system and the temperature and pressure balance are realized, the water vapor required by the first group of electric stacks and the second group of electric stacks is completely provided by the circulated anode tail gas, and after the system reaches a stable state, the starting of the SOFC system for recycling the tail gas is completed, so that the normal operation of the system is realized.
Preferably, the starting temperature of the first group of electric stacks and the second group of electric stacks is 400-600 ℃; the preferred start-up temperature uses less start-up preheating energy.
Wherein, the safe working pressure range of the first group of electric piles and the second group of electric piles is preferably 0-500 kPa; most preferably, the safe operating pressure range is 0.1 to 50 kPa; the optimized working pressure range is that the pile works stably, the fuel utilization rate is high, the safety is good, and the maintenance cost is lower.
According to the starting method of the SOFC system with the tail gas recycling function, the connection relation and arrangement mode of all components in the SOFC system are fully utilized, and the starting sequence and mode of the SOFC system are specifically adjusted and controlled, so that the SOFC system can be started with the lowest energy and the smallest starting system; after the SOFC system is normally started, the water vapor balance can be completely achieved, so that the energy consumption is reduced; the starting method is simple, reliable, good in practicability and high in safety, and has positive effects on large-scale popularization and application of the SOFC system.
Compared with the prior art, the invention has the beneficial effects that:
1. the SOFC system optimizes the connection and arrangement modes of all the components in the SOFC system, thereby completing the starting and stable operation of the whole SOFC system by controlling the starting sequence of the electric pile, remarkably simplifying the structure of the starting system, reducing the requirement of the SOFC system on starting energy and remarkably reducing the operation cost.
2. The SOFC system can directly recycle part of tail gas generated by the electric pile, thereby obviously improving the fuel utilization rate of the system participating in the electric pile power generation and obviously reducing the operation cost.
3. After the SOFC system is normally operated, the cyclic balance of the system self high-temperature steam is realized through cyclic utilization of tail gas, so that the generation of the steam and cyclic components are simplified, the operation cost is lower, and the energy consumption is also obviously reduced.
4. The SOFC system can effectively improve the utilization efficiency of heat, improve the integral cogeneration efficiency of the system, reduce the steam amount entering the tail gas burner, and be beneficial to improving the durability of the catalyst in the tail gas burner and the reliability of the SOFC system.
Description of the drawings:
FIG. 1 is a schematic diagram of a SOFC system in accordance with example 1 of the present invention;
reference numerals: 1-a second group of galvanic piles; 2-a first group of galvanic piles; 3-heat exchanger; a 4-reformer; 5-tail gas burner; 6-an evaporator; 7-desulfurizing device; 8-a waste heat recoverer; 9-a gas circulation auxiliary device; 10-opening and closing means; 11-galvanic pile.
Detailed Description
The present invention will be described in further detail with reference to test examples and specific embodiments. It should not be construed that the scope of the above subject matter of the present invention is limited to the following embodiments, and all techniques realized based on the present invention are within the scope of the present invention.
Example 1:
SOFC system structure composition (figure 1) for recycling tail gas:
mainly comprises a first group of electric piles 2 (consisting of 1 electric pile 11), a second group of electric piles 1 (consisting of 2 electric piles 11), a heat exchanger 3, a reformer 4, an evaporator 6 and a tail gas burner 5; wherein the first group of electric piles 2 and the second group of electric piles 1 are connected in parallel; the output end of the evaporator 6 is connected with the input end of the reformer 4; the output end of the reformer 4 is respectively connected with the anode input ends of the first group of electric piles 2 and the second group of electric piles 1, an opening and closing device 10 (gas flow valve) is respectively arranged between the output end of the reformer 4 and the anode input ends of the first group of electric piles 2 and the second group of electric piles 1, whether the anode input ends of the first group of electric piles 2 and/or the second group of electric piles 1 are communicated with the output end of the reformer 4 or not can be controlled by the opening and closing device (10), and the gas flow of the reformer 4 input to the first electric piles 2 and the second electric piles 1 is controlled; the cathode output ends of the first group of electric piles 2 and the second group of electric piles 1 are connected with the input end of the tail gas burner 5; the anode output ends of the first group of electric piles 2 and the second group of electric piles 1 are simultaneously connected with the input end of the tail gas burner 5 and the input end of the reformer 4, opening and closing devices 10 (gas flow valves) are arranged between the anode output ends of the first group of electric piles 2 and the second group of electric piles 1 and the input end of the reformer 4 as well as between the anode output ends of the tail gas burner 5, and the tail gas amount of the anode output ends of the first group of electric piles 2 and/or the second group of electric piles 1 entering the reformer 4 and the tail gas burner 5 can be controlled through the opening and closing devices; the output end of the tail gas burner 5 is connected with the heat input end of the heat exchanger 3; the heat exchanger 3 is used for preheating fuel gas entering the reformer 4 and/or cathode air entering the first group of stacks 2 and the second group of stacks 1, or for providing heat for the start-up of the reformer 4, the second group of stacks 1; the output end of the heat exchanger 3 is also connected with a waste heat recovery device 8; the input end of the reformer 4 is also connected with a desulfurizer 7; a gas circulation auxiliary device 9 (ejector) is further arranged between the anode output ends of the first group of electric stacks 2 and the second group of electric stacks 1 and an opening and closing device 10 (a gas flow valve) of the input end of the reformer 4, an output port of the ejector is connected with the input end of the reformer 4, a high-pressure input port of the ejector is high-temperature fuel gas, and a low-pressure input port of the ejector is anode output end tail gas.
The system starting method comprises the following steps:
s1: a starting stage: the first group of electric stacks 2 and the reformer 4 are communicated through the opening and closing device 10, a switch (opening and closing device 10) of the second group of electric stacks 1 and the reformer 4 is disconnected, and the gas circulation auxiliary device 9 (ejector) is closed; preheating the evaporator 6, the reformer 4 and the first group of electric stacks 2, introducing preheated air, fuel and water vapor after the first group of electric stacks 2 reach a starting temperature (500 ℃), and starting the first group of electric stacks 2; introducing all of the anode off-gas of the first group of stacks 2 into the off-gas burner 5; the high-temperature gas generated by the combustion of the tail gas burner 5 enters the heat exchanger 3 and preheats the second group of electric stacks 1 through the heat exchanger 3;
s2: and (3) a transition stage: when the first group of electric piles 2 are started normally and the second electric pile 1 reaches the starting temperature (500 ℃), the anode tail gas of the first group of electric piles 2 is led into the reformer 4 gradually by adjusting the opening and closing device 10 and the gas circulation auxiliary device 9; simultaneously, the second group of electric stacks 1 and the reformer 4 are communicated, the introduction amount of the system fuel and air is increased, the amount of water injected into the evaporator 6 is reduced, and the second group of electric stacks 1 are started; introducing all or part of anode tail gas of the second group of electric stacks 1 into a tail gas burner 3, so that the first group of electric stacks 2 and the second group of electric stacks 1 safely run simultaneously;
s3: and (3) a normal working stage: the evaporator 6 is stopped, the gas circulation auxiliary device 9, the reformer 4, the fuel and air supply device are dynamically adjusted, the fuel and air input quantity of the system and the proportion of anode tail gas of the first group of electric stacks 2 and the second group of electric stacks 1 entering the reformer 4 and the tail gas burner 5 are controlled, the material balance of the inlet and outlet gas of the system and the temperature and pressure balance are realized, the water vapor required by the first group of electric stacks 2 and the second group of electric stacks 1 is completely provided by the circulated anode tail gas, and after the system reaches a stable state, the SOFC system for recycling the tail gas is started, so that the system works normally.
The system operation route is as follows:
and (3) cathode: external air enters the heat exchanger 3 through the air supply device for preheating, and the heat exchanger 3 supplies heat through being connected with the tail gas burner 5; the heated air can enter the first group of electric stacks 2 and the second group of electric stacks 1 respectively according to distribution; the cathode off-gas of the first group of stacks 2 and the second group of stacks 1 is discharged and then all is led to the off-gas burner 5 or the heat exchanger 3.
Anode: natural gas, methane and other fuels enter the desulfurizer 7 through the fuel supply device, the fuel after desulfurization treatment of the desulfurizer 7 enters the reformer 4 for reforming, and the reformed fuel can enter the first group of electric stacks and the second group of electric stacks respectively; the reformer 4 supplies heat required for reforming fuel through the heat supply of the heat exchanger 3; in the starting stage, all anode tail gas generated by the first group of electric stacks 2 is led into a tail gas burner 5 for burning, and high-temperature gas generated by burning is led into a heat exchanger 3 to provide heat for a reformer, preheated air, preheated second electric stacks and other places needing heat; in the transition stage, part of anode tail gas generated by the first group of electric stacks 2 is led into a tail gas combustor 5 for combustion, and the other part is led into a reformer 4 through a gas circulation auxiliary device 9; in the normal working stage, part of anode tail gas generated by the first group of electric stacks 2 and the second group of electric stacks 1 is led into a tail gas burner 5 for burning, and the other part is led into a reformer 4 through a gas circulation auxiliary device 9; the tail gas after heat exchange by the heat exchanger 3 can enter various waste heat recovery devices 8 according to the requirements.
Moisture content: in the starting stage, the water supply device supplies deionized water to the evaporator 6, and steam generated by the evaporator 6 is supplied to the reformer 4 for reforming hydrocarbon fuel; in the transition stage, the water supplied by the water supply device to the evaporator 6 is gradually reduced, and the water required by the reformer 4 is gradually supplied by the water in the tail gas of the anode of the electric pile; in the normal operation phase, the water supply device and the evaporator 6 are stopped, and the water required by the reformer 4 is completely supplied by the water in the stack anode tail gas.
Theoretical efficiency measurement:
the first group of electric piles 2 (consisting of 1 electric pile 11 with the power of 1 kW) and the second group of electric piles 1 (consisting of 2 electric piles 11 with the power of 0.5 kW) have the same power, and the powers are 1 kW;
the tail gas of the first group of electric pile 2 is fully recycled, which is equivalent to 50 percent of the tail gas of the whole system, and the fuel utilization rate of the first electric pile and the second electric pile is 70 percent, the power generation efficiency is 60 percent, and the power generation efficiency is 1 Nm 3 And the heat value of the natural gas is calculated by 10 kW.h electric quantity, and the fuel consumption of the system is reduced by 15%.
Natural gas consumption per hour:
when the first group of electric piles 2 independently operate, the natural gas quantity is 0.24 Nm 3 Remaining 0.24 x (1-70%) =0.072 Nm 3 ；
The total circulation system 2 kW power, fuel consumption per hour: 0.24 x 2-0.072 = 0.408 Nm 3 ；
Conventional 2 kW power system, fuel consumption per hour: 0.24+0.24=0.48 Nm 3 ；
Fuel reduction/saving amount: a decrease per hour (0.48-0.408)/0.48=15%;
fuel utilization rate in the stack: (0.408-0.072)/0.408=82.35%
It can be seen that the exhaust gas circulation ratio of the SOFC system is 50%, and the fuel utilization rate of the electric pile is 82.35%.
Example 2:
SOFC system structure composition: the difference from embodiment 1 is only that the second group of stacks 1 consists of only 1 stack 11, but the sum of the powers of the second group of stacks 1 (consisting of 1 stack 11 with a power of 1 kW) and the first group of stacks 2 (consisting of 1 stack 11 with a power of 1 kW) is the same as embodiment 1.
The SOFC system operation route and start-up method were the same as in example 1.
Through measurement and calculation, the exhaust gas circulation ratio of the SOFC system is 50%, and the fuel utilization rate of the electric pile is 82.35%.
Example 3:
the SOFC system structure composition was the same as example 2;
the SOFC system operating route and start-up method differ from example 2 only in that,
s1: a starting stage: the first group of electric stacks 2 and the reformer 4 are communicated through the opening and closing device 10, a switch (opening and closing device 10) of the second group of electric stacks 1 and the reformer 4 is disconnected, and the gas circulation auxiliary device 9 (ejector) is closed; preheating the evaporator 6, the reformer 4 and the first group of electric stacks 2, introducing preheated air, fuel and water vapor after the first group of electric stacks 2 reach a starting temperature (500 ℃), and starting the first group of electric stacks 2; introducing all of the anode off-gas of the first group of stacks 2 into the off-gas burner 5; the high-temperature gas generated by the combustion of the tail gas burner 5 enters the heat exchanger 3 and preheats the second group of electric stacks 1 through the heat exchanger 3;
s2: and (3) a transition stage: after the first group of electric stacks 2 are started normally and the second electric stack 1 reaches the starting temperature (500 ℃), increasing the quantity of water injected into the evaporator 6 and the introduction quantity of system fuel and air, and starting the second electric stack 1; after the second electric pile is started normally, anode tail gas of the first electric pile group 2 is gradually led into the reformer 4 by adjusting the opening and closing device 10 and the gas circulation auxiliary device 9, so that the amount of water and system fuel injected into the evaporator 6 are reduced, and the first electric pile group 2 and the second electric pile group 1 are operated safely at the same time;
s3: and (3) a normal working stage: the evaporator 6 is stopped, the gas circulation auxiliary device 9, the reformer 4, the fuel and air supply device are dynamically adjusted, the fuel and air input quantity of the system and the proportion of anode tail gas of the first group of electric stacks 2 and the second group of electric stacks 1 entering the reformer 4 and the tail gas burner 5 are controlled, the material balance of the inlet and outlet gas of the system and the temperature and pressure balance are realized, the water vapor required by the first group of electric stacks 2 and the second group of electric stacks 1 is completely provided by the circulated anode tail gas, and after the system reaches a stable state, the SOFC system for recycling the tail gas is started, so that the system works normally.
Through measurement and calculation, the exhaust gas circulation ratio of the SOFC system is 50%, and the fuel utilization rate of the electric pile is 82.35%.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.

Claims (10)

1. An SOFC system for recycling exhaust gas, comprising: a first set of stacks, a second set of stacks, a heat exchanger, a reformer, an evaporator, and a tail gas burner;
the output end of the evaporator is connected with the input end of the reformer;
the output end of the reformer is respectively connected with the anode input ends of the first group of electric piles and the second group of electric piles, an opening and closing device is arranged between the output end of the reformer and the anode input ends of the first group of electric piles and the second group of electric piles, whether the anode input ends of the first group of electric piles and/or the second group of electric piles are communicated with the output end of the reformer or not can be controlled through the opening and closing device, and the gas flow rate of the reformer input into the first group of electric piles and the second group of electric piles is controlled;
the cathode output ends of the first group of electric stacks and the second group of electric stacks are connected with the input end of the tail gas burner;
the anode output ends of the first group of electric stacks and the second group of electric stacks are simultaneously connected with the input end of the tail gas burner and the input end of the reformer, opening and closing devices are arranged between the anode output ends of the first group of electric stacks and the second group of electric stacks and the input end of the reformer as well as between the anode output ends of the first group of electric stacks and the second group of electric stacks and the input end of the tail gas burner, and the tail gas amount of the anode output ends of the first group of electric stacks and/or the second group of electric stacks entering the reformer and the tail gas burner can be controlled through the opening and closing devices;
the output end of the tail gas burner is connected with the heat input end of the heat exchanger.
2. The exhaust gas recycling SOFC system of claim 1, wherein the exhaust gas combustor, reformer, and heat exchanger together comprise an integrated heat exchange module.
3. The exhaust gas recycling SOFC system of claim 1, wherein the first and second groups of stacks together comprise an SOFC power module.
4. A tail gas recycling SOFC system according to any of claims 1-3, characterized in that a gas circulation auxiliary means is further provided between the anode output of the first and second stacks and the reformer input.
5. The tail gas recycling SOFC system of claim 4, wherein the gas recycling auxiliary device is an ejector or a high temperature fan.
6. The exhaust gas recycling SOFC system of claim 5, wherein the gas circulation auxiliary is an ejector; the output port of the ejector is connected with the input end of the reformer, the high-pressure input port of the ejector is used for inputting fuel gas, the low-pressure input port of the ejector is connected with the anode output ends of the first group of electric stacks and the second group of electric stacks, anode tail gas of the first group of electric stacks and the second group of electric stacks is input, and the pressure of the fuel gas is higher than that of the anode tail gas.
7. A tail gas recycling SOFC system according to any of claims 1-3, characterized in that the output of the heat exchanger is also connected to a waste heat recovery device.
8. A tail gas recycling SOFC system according to any of claims 1-3, characterized in that the input of the reformer is also connected to a desulfurizer.
9. A method of starting up an SOFC system with recycling of tail gas according to any of claims 1-8, comprising the steps of:
s1: a starting stage: connecting the first group of electric piles and the reformer, disconnecting the second group of electric piles and the reformer, and closing the gas circulation auxiliary device; preheating the evaporator, the reformer and the first group of electric stacks, and after the first group of electric stacks reach the starting temperature, introducing air, fuel and water vapor to start the first group of electric stacks; introducing all anode tail gas of the first group of galvanic piles into a tail gas burner; preheating a second group of stacks;
s2: and (3) a transition stage: when the first group of electric stacks are started normally and the second electric stacks reach the starting temperature, anode tail gas of the first group of electric stacks is led into the reformer gradually by adjusting the opening and closing device and the gas circulation auxiliary device; simultaneously, the second group of electric stacks are communicated with the reformer, the introduction amount of the system fuel and air is increased, the amount of water injected into the evaporator is reduced, and the second group of electric stacks are started; introducing all or part of anode tail gas of the second group of electric stacks into a tail gas burner, so that the first group of electric stacks and the second group of electric stacks safely run at the same time;
s3: and (3) a normal working stage: the evaporator is stopped, the gas circulation auxiliary device, the reformer, the fuel and air supply device are dynamically adjusted, the fuel and air input quantity of the system and the ratio of anode tail gas of the first group of electric stacks and the second group of electric stacks to the reformer and the tail gas burner are controlled, the material balance of the inlet and outlet of the system and the temperature and pressure balance are realized, the water vapor required by the first group of electric stacks and the second group of electric stacks is completely provided by the circulated anode tail gas, and after the system reaches a stable state, the starting of the SOFC system for recycling the tail gas is completed, so that the normal operation of the system is realized.
10. The method for starting an SOFC system with recycling of tail gas according to claim 9, wherein the starting temperatures of the first and second groups of stacks are 400-800 ℃; the safe operating pressure range of the first group of electric stacks and the second group of electric stacks is 0-500 kPa.
CN202310271740.8A 2023-03-20 2023-03-20 SOFC system for recycling tail gas and starting method Pending CN116207310A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202310271740.8A CN116207310A (en) 2023-03-20 2023-03-20 SOFC system for recycling tail gas and starting method

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202310271740.8A CN116207310A (en) 2023-03-20 2023-03-20 SOFC system for recycling tail gas and starting method

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CN116207310A true CN116207310A (en) 2023-06-02

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