CN115651714A - Device and method for gasification conversion of low-calorific-value fuel - Google Patents
Device and method for gasification conversion of low-calorific-value fuel Download PDFInfo
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Abstract
The invention belongs to the technical field of chemical gas production, and particularly relates to a device and a method for gasification conversion of low-calorific-value fuel. The invention adopts oxygen-rich gas, oxygen-poor gas and steam of specific components as gasifying agents to carry out gasification conversion on low-calorific-value fuel; the device comprises: a normal temperature air separation oxygen making device, a cyclone separator, a membrane separator, a heat exchanger, a supercharging device and the like; the circulating fluidized bed receives low-calorific-value fuel, generates high-calorific-value fuel gas containing hydrogen and carbon monoxide and containing nitrogen less than or equal to 5%, and generates power by-product steam; after the output flue gas is utilized by heat energy, part of the output flue gas is circularly returned to be mixed with oxygen to form oxygen enrichment, and the rest of the output flue gas is converted into carbon dioxide. The method adopts carbon dioxide background gas mixed with pure oxygen as oxygen enrichment and steam as a gasifying agent to gasify the low-calorific-value fuel, can efficiently convert the low-calorific-value fuel into high-calorific-value fuel gas containing nitrogen less than or equal to 5 percent, and has the advantages of high conversion efficiency, simple operation, high automation degree, good economic benefit and remarkable advantage.
Description
Technical Field
The invention belongs to the technical field of thermal energy engineering, and particularly relates to a device and a method for gasification conversion of low-calorific-value fuel.
Background
The normal pressure fixed bed gas producer (also called mixed gas producer) usually uses the mixed gas of air and water vapor as gasifying agent to produce coal gas, and its working process is usually to add fuel from the top of the gas producer, then to introduce air or oxygen-enriched gas from the bottom of the gas producer and solid fuel to burn, to accumulate heat in the fuel layer, then to introduce steam into the fuel layer to react with carbon to produce water gas, and the process of producing coal gas is mainly in the gasifying layer. Generally, the main chemical reactions of the gasification layer are the following oxidation and reduction reactions:
C+ O2 = CO2 + Q （1）
2C + O2 = 2CO + Q 2CO + O2 = 2CO2 + Q （2）
c + H2O (steam) = CO + H2-Q (3)
C + 2H2O (vapour) = CO2 + 2H2-Q (4)
C + CO2 = 2CO – Q （5）
In the gasification reaction process, oxygen is mainly used as a gasification agent to participate in oxidation reaction and release heat energy, and water vapor is mainly used as a gasification agent to participate in reduction reaction and absorb heat energy to generate hydrogen and carbon monoxide;
obviously, if the balance between the heat released by the oxidation reaction and the heat absorbed by the reduction reaction can be maintained, theoretically, the gas making process can be continuously carried out;
however, in any case, if air is used as the oxidant source, since the air contains about 21% of oxygen and 78% of nitrogen, the combustion reaction process using the air as the oxidant source inevitably brings a large amount of nitrogen, which not only greatly reduces the calorific value of the fuel gas, but also generates a large amount of nitrogen oxide pollution;
oxygen enrichment, which generally means oxygen-enriched air with volume percentage of oxygen of not less than 21% (wherein the non-oxygen component is mostly nitrogen), has been widely applied to combustion-supporting, energy-saving and environmental-friendly fields such as various fuel oils, fuel gases, coal-fired kilns (glass, cement, ceramics), various boilers, heating furnaces, incinerators, heating media furnaces, hot blast furnaces, smelting furnaces, aircraft engines, marine engines, etc.; the oxygen enrichment technology is applied to the fields of catalytic cracking, desulfurization, wastewater treatment, engine synergism, oxygen enrichment coal gas production, various oxidation reactions, fermentation and the like, so that better economic benefits are obtained. However, in practice, mixing carbon dioxide generated by a combustion chemical reaction with pure oxygen to obtain oxygen-enriched air with an oxygen volume percentage of ≧ 21% (wherein the non-oxygen component is carbon dioxide) can also effectively support the combustion chemical reaction, also commonly referred to as flue gas recirculation, and using this as a source of gasifying agent for oxygen in the gasification process would bring a revolutionary technical advance to the gasification process.
Disclosure of Invention
In view of the above circumstances, an object of the present invention is to provide an apparatus and method for gasification reforming of low-calorie fuels, which have high reforming efficiency, good economic efficiency, and simple operation, in a process of converting energy using low-calorie fuels such as biomass.
The device for gasification and transformation of low-calorific-value fuel provided by the invention adopts oxygen enrichment, oxygen depletion and steam of specific components as gasification agents to gasify and transform the low-calorific-value fuel, and the structure of the device is shown in figure 1, and the device comprises:
(1) At least one set of oxygen generating device adopting normal temperature air separation is used for directly extracting oxygen with the purity of 80-99.9% from the air; the normal temperature air separation oxygen generating device can be a device adopting membrane separation or pressure swing adsorption technology;
(2) At least one set of first circulating fluidized bed, also called oxygen-enriched gasification reaction bed, is used for carrying out oxidation exothermic reaction in the main chemical reaction process of a common coal gasification layer and providing heat energy for the whole system; and the source of the oxidant in the circulating fluidized bed is oxygen-enriched air (wherein the non-oxygen component is carbon dioxide) with the oxygen volume percentage of ≧ 21% after the oxygen provided by the oxygen making device is mixed with the carbon dioxide in the flue gas;
(3) At least one set of high-temperature flue gas cyclone separator is used for separating high-temperature materials which are not burnt out from the first circulating fluidized bed; wherein, the flue gas exchanges heat through a set of heat exchangers (group) and produces steam as a byproduct, and the separated high-temperature material and the high-temperature material overflowing from the middle part of the first circulating fluidized bed are sent into a second circulating fluidized bed;
(4) At least one set of second circulating fluidized bed, also called lean oxygen gasification reaction bed, is used for carrying out reduction gas making reaction in the main chemical reaction process of a common coal gasification layer; the gasification agent steam is fed after being decompressed from the byproduct steam, heat energy is from high-temperature materials brought in by the first circulating fluidized bed and carbon in low-heat-value fuels such as biomass and the like to generate high-heat-value fuel gas which mainly contains hydrogen, carbon monoxide and methane and contains nitrogen less than or equal to 5% in a continuous gasification reaction in the bed, wherein part of the fuel gas is circularly returned to the second circulating fluidized bed to serve as carrier gas;
(5) At least one set of high-temperature coal gas cyclone separator is used for separating high-temperature materials which are not completely gasified in the second circulating fluidized bed; meanwhile, a ceramic membrane filter can be preferably, but not necessarily, matched to thoroughly intercept solid-phase components in the high-temperature coal gas, and the solid-phase components are recycled and returned to the first circulating fluidized bed for combustion chemical reaction;
(6) The heat exchanger (group) is preferably but not necessarily used for adjusting the output temperature of the high-temperature fuel gas, and simultaneously recovering heat energy and improving the steam quality;
(7) At least one set of high-temperature gas pressure boosting device is used for boosting the gas pressure, wherein one part of the high-temperature gas pressure boosting device is sent to a terminal gas using point (such as direct combustion, power generation or further hydrogen purification and the like), and the other part of the high-temperature gas pressure boosting device boosts partial gas and circulates the partial gas as carrier gas of the second circulating fluidized bed;
(8) At least one ceramic membrane filter, which is used for thoroughly intercepting solid phase components in hot flue gas of heat energy recovery byproduct steam from a first circulating fluidized bed (oxygen-enriched gasification reaction bed) through a heat exchanger (group), wherein the pressure loss is provided by a set of high-temperature flue gas pressure boosting device, on one hand, the ceramic membrane filter is used for overcoming the filtration and the on-way resistance loss, on the other hand, the ceramic membrane filter is used for circularly returning oxygen prepared by a system which directly extracts oxygen with the purity of 80-99.9% from the air with the normal-temperature air separation oxygen generation device, and premixing oxygen-enriched air (wherein the non-oxygen component is carbon dioxide) with the oxygen volume percentage of not less than 21% so as to provide oxygen for the oxidation reaction process;
(9) And at least one set of control system is used for controlling the on-off/switching of the field equipment and realizing the continuous cyclic gasification process.
In the present invention, the "oxygen enrichment" refers to oxygen-enriched air (preferably, oxygen-enriched air is oxidized to 23-40% by volume, wherein the non-oxygen component is carbon dioxide) obtained by premixing the prepared oxygen with part of the flue gas discharged from the system to an oxygen-containing volume percentage of ≥ 21%, and the "oxygen-poor" refers to an oxygen-containing volume percentage of ≤ 1%.
The method for gasification and conversion of the low-calorific-value fuel is based on the device and comprises the following specific steps:
(1) Directly extracting oxygen with the purity of 80-99.9% from air by adopting a normal-temperature air separation oxygen generation device, premixing the prepared oxygen and part of flue gas discharged by a system according to an air supply loop designed as shown in figure 1 until the oxygen-containing volume percentage of oxygen-enriched air (preferably, the oxygen-enriched air is enriched to 23-40%, wherein the non-oxygen component is carbon dioxide) is not less than 21% is preheated to 100-200 ℃, and then sending the oxygen-enriched air into a first circulating fluidized bed as an oxygen source of an oxidation reaction, wherein the pressure of the oxygen-enriched air meets the requirement of suspension gasification, typically, the air pressure requirement of 5-30 kpa is generally provided;
(2) The preheated rich oxygen is sent into the first circulating fluidized bed to carry out oxidation reaction with low-heat-value fuels such as biomass in the bed, namely the following main chemical reaction processes of a common coal gasification layer are completed in the bed, heat is released, and heat energy required by the whole system is maintained:
C+ O2 = CO2 + Q ， （1）
2C + O2 = 2CO + Q ，2CO + O2 = 2CO2 + Q ， （2）
when the system is started, the initial fuel required by the first circulating fluidized bed is from the initial feeding of low-calorific-value fuel such as biomass, the oxygen enrichment is obtained by premixing prepared oxygen and air (most of non-oxygen components of the oxygen enrichment are nitrogen), when the whole system normally operates, the fuel gradually comes from un-gasified carbon-containing materials fed reversely from a cyclone separator, a ceramic membrane separator and the like on the side of the second circulating fluidized bed, and the oxygen enrichment replaces the prepared oxygen enrichment and part of flue gas discharged by the system to be premixed to oxygen-enriched air with the oxygen volume percentage of not less than 21% (preferably, the oxygen enrichment is 23-40%, wherein the non-oxygen components are carbon dioxide); the reaction temperature is generally controlled according to different ash melting points of low-calorific-value fuels such as biomass, and is typically controlled to be 800-950 ℃;
(3) High-temperature flue gas generated by the first circulating fluidized bed passes through a cyclone separator to separate high-temperature materials which are not burnt out from the first circulating fluidized bed; wherein, the flue gas is directly output as a product by the steam generated by heat exchange of the heat exchanger (group), and can also be sent to a turbine for power generation; meanwhile, the separated high-temperature materials and the high-temperature materials overflowing from the middle part of the first circulating fluidized bed are sent into a second circulating fluidized bed to be used as a main heat energy source of the high-temperature first circulating fluidized bed;
(4) In the second circulating fluidized bed, the high-temperature material overflowed from the middle part of the first circulating fluidized bed and the high-temperature material separated by the cyclone separator and the low-heat value fuel such as biomass are continuously fed, and the main reduction chemical reaction process of a common coal gasification layer is generated in the second circulating fluidized bed:
c + H2O (vapour) = CO + H2-Q, (3)
C + 2H2O (vapour) = CO2 + 2H2-Q, (4)
C + CO2 = 2CO – Q， （5）
Wherein, the steam from the byproduct steam is sent into the reactor after being decompressed, and the typical temperature is controlled between 150 and 250 ℃; the heat energy required by the main endothermic reaction is from high-temperature materials brought in by a first circulating fluidized bed, the circulating carrier gas is from self-produced coal gas, the circulating carrier gas and carbon and the like in low-calorific-value fuels such as biomass and the like in a second circulating fluidized bed generate violent gasification reaction in the second circulating fluidized bed, the reaction temperature is generally controlled to be 700-850 ℃, the reaction process is completed in an oxygen-deficient state (typically, the oxygen content is less than or equal to 1% by volume percent), and high-calorific-value fuel gas mainly containing hydrogen, carbon monoxide and methane and containing nitrogen is less than or equal to 5% is generated;
(5) The high-temperature materials which are not completely gasified and reacted are separated by the cyclone separator after the high-heat value fuel gas is generated, preferably, a first-stage ceramic membrane filter is added to thoroughly intercept solid phase components in the high-temperature materials, the high-temperature materials are circularly returned to be sent into the first circulating fluidized bed for combustion chemical reaction, and the high-temperature fuel gas can be subjected to heat exchanger (group) to adjust the output temperature of the high-temperature fuel gas, recover heat energy and improve steam quality at the same time, and can be output as a product, the hot fuel gas can be directly used for combustion, and carbon monoxide in the hot fuel gas can be continuously converted into hydrogen to extract hydrogen and the like in the high-heat value fuel gas;
(6) The high-calorific-value gas is generated, the gas pressure is increased by the high-temperature gas pressure boosting device according to the working pressure required by a client, and the gas is output as product gas, wherein one part of the gas can be sent to a terminal gas using point (such as direct combustion, power generation or further hydrogen purification and the like), and the other part of the gas can also be output according to the pressure requirement; boosting part of the coal gas by another high-temperature coal gas boosting device and circulating the coal gas as carrier gas of a second circulating fluidized bed, typically boosting the pressure to the requirement of 5-30 kpa of wind pressure;
(7) The high-temperature flue gas generated by the first circulating fluidized bed generally passes through a multistage heat exchanger to recover heat energy, high-temperature and high-pressure steam is generated as a byproduct, the flue gas passes through a ceramic membrane filter to thoroughly intercept solid phase components contained in the flue gas, the pressure loss of the flue gas is generally provided by a set of high-temperature flue gas pressure boosting device, on one hand, the high-temperature flue gas pressure boosting device is used for overcoming the filtration and the on-way resistance loss, on the other hand, the high-temperature flue gas pressure boosting device is used for circularly returning oxygen prepared by a system which directly extracts oxygen with the purity of 80-99.9% from air by the normal-temperature air separation (membrane separation or pressure swing adsorption method) technology, and on the other hand, the high-temperature flue gas is premixed to oxygen-enriched air with the oxygen volume percentage of not less than 21% (wherein the non-oxygen component is carbon dioxide) to provide oxygen for the oxidation reaction process.
The gasification and conversion process can continuously realize the cyclic gasification and conversion process of low-calorific-value fuels such as biomass and the like under the action of the control system.
In the gasification conversion method, the gas making process of the gasification reduction reaction, namely the process of generating carbon monoxide and hydrogen, is carried out under the condition of poor oxygen, therefore, the calorific value of the generated gas is greatly reduced because of ineffective components such as nitrogen and the like, and the calorific value is higher, generally, a two-stage gas generator which takes 5500kcal/kg of fire coal as a raw material generally is listed, the ineffective components such as nitrogen and the like in the fuel gas account for up to 50 percent, and the calorific value is only about 1500kcal/m < 3 >, but the invention adopts the calorific value of low calorific value fuel such as biomass and the like, even 3500kcal/kg, can also obtain high calorific value fuel with the nitrogen component of only about 0.5 to 2 percent and the effective components such as carbon monoxide, hydrogen, methane and the like of up to 55 to 75 percent, the calorific value of the fuel can easily reach more than 2500kcal/m < 3, and can be used for generating electricity by-product steam, and the energy conversion efficiency is up to more than 90 percent;
moreover, by the oxygen control vaporization technology, the gasification agent is flexibly adjusted to contain oxygen, the effective components of the gasification agent can be generated to be mainly hydrogen and carbon monoxide which are up to 70 percent (wherein, typically, such as 40 percent of hydrogen and 30 percent of carbon monoxide), and the rest is methane and carbon dioxide, at present, the industrial raw material gas of the level is generated by adopting high-quality 6500kcal/kg raw material coal, the revolutionary process technology provides a brand-new solution for the high-efficiency utilization of straws, and on the basis of the biomass energy of the periodic growth, the oxygen control vaporization and the nickel-based membrane purification material based on SSS technology can extract pure hydrogen, can be combined with carbon dioxide to convert into methanol, and is combined with a new energy supply system assisted by other clean electric power (such as photovoltaic, hydroelectric power and nuclear power), which is a necessary way for human beings to realize the energy industry of carbon neutralization;
in addition, the invention is applied to gasification and conversion of biomass energy such as straws and the like, the main component of the generated residue is plant ash, and beneficial components such as sylvite and the like are added to return the field simply, so that the problem of environmental protection and discharge caused by direct burning is solved.
The invention has the advantages of high conversion efficiency, simple operation, high automation degree and good economic benefit, and has obvious advantages compared with the prior coal gasification process taking coal as fuel.
Drawings
Figure 1 is a schematic representation of the low heating value fuel gasification process of the present invention.
Fig. 2 is a schematic view of the structure of the gasification apparatus for low heating value fuel according to the present invention.
Reference numbers in the figures: 1 is a normal-temperature air separation oxygen generation device, A1 is a first circulating fluidized bed, and A2 is a second circulating fluidized bed; f1 is a first circulating fluidized bed side cyclone separator, and F2 is a second circulating fluidized bed side cyclone separator; m1 is a high-temperature coal-gas separator at the side of the second circulating vulcanization bed, and M2 is a high-temperature smoke-gas separator at the side of the first circulating vulcanization bed; h1, H2, H3, H4 are heat exchangers, R1, R2, R3, R4 are dumpers, AB1, AB2, AB3 are high-temperature gas booster devices (fans), PV01 is a storage tank. Q1 is a feeding machine interface, Q2 is a water inlet interface, and Q3 is an oxygen interface; w1 is a gas outlet, W2 is a steam outlet, W3 is a residue outlet, W4 is a flue gas outlet, and W5 is waste water pollution discharge; 1-1,1-2,1-3 are respectively interfaces on the normal-temperature air separation oxygen production device 1; 2-1,2-2,2-3,2-4,2-5,2-6,2-7,2-8 are interfaces on the first circulating fluidized bed A1, respectively; 3-1,3-2.3-3,3-4,3-5 are interfaces on the second circulating fluidized bed A2, respectively.
Detailed Description
The invention is further described below with reference to the figures and examples.
The embodiment of the device and the process flow for gasification and conversion of the low heating value fuel provided by the invention is shown in figure 1. The device comprises: a normal-temperature air separation oxygen generation device (nitrogen-oxygen separation device) 1, a first circulating fluidized bed A1 and a second circulating fluidized bed A2; a first circulating fluidized bed side cyclone separator F1 and a second circulating fluidized bed side cyclone separator F2; a second circulating vulcanization bed side high-temperature coal-gas separator M1 and a first circulating vulcanization bed side high-temperature smoke-gas separator M2; heat exchangers H1, H2, H3 and H4, dischargers R1, R2, R3 and R4, high-temperature coal gas pressure boosting devices AB1, AB2 and AB3 (fans) and a storage tank PV01; a feeding machine interface Q1, a water inlet device interface Q2 and an oxygen interface Q3; a gas outlet W1, a steam outlet W2, a residue outlet W3, a flue gas outlet W4 and a wastewater discharge outlet W5; the normal temperature air separation oxygen generation device 1 is provided with interfaces 1-1,1-2 and 1-3; the first circulating fluidized bed A1 is provided with interfaces 2-1,2-2,2-3,2-4,2-5,2-6,2-7 and 2-8; the second circulating fluidized bed A2 is provided with interfaces 3-1,3-2, 3-3,3-4 and 3-5; wherein:
an upper interface 1-1 of the normal temperature air separation oxygen making device 1 is connected with the upper part of H3, and an interface 1-2 is connected with the lower part of H3; the interfaces 1-3 are respectively connected with a lower interface 2-7 of the first circulating fluidized bed A1 and a lower interface 3-5 of the second circulating fluidized bed A2;
in the first circulating fluidized bed A1, a middle connector 2-1 is connected with Q1, an upper connector 2-2 is connected with F1, a connector 2-3 is connected with R1, a connector 2-4 is connected with the upper part of H3, a connector 2-5 is connected with the upper part of H3, a connector 2-6 is respectively connected with R2 and R4, a connector 2-7 is connected with an upper connector 1-2 of a normal-temperature air separation oxygen generation device 1, and connectors 2-8 are sequentially connected with high-temperature smoke gas separators M2 and W3;
in the second circulating fluidized bed A2, a middle connector 3-1 is connected with Q1, and an upper connector 3-2 is connected with F2; the upper interface 3-3 is respectively connected with R3, R1 and R4, the lower interface 3-4 is connected with AB2, and the lower interface 3-5 is connected with the upper interface 1-3 of the normal temperature air separation oxygen making device 1;
the heat exchanger H1 is respectively connected with the upper part of the heat exchanger H4, the upper part of the F1 and the gas outlet W1;
the heat exchanger H2 is respectively connected with a water supply source and the lower part of the heat exchanger H4 and a sewage discharge outlet W5;
the heat exchanger H3 is connected with an upper interface 1-1 of a normal-temperature air separation oxygen making device 1, the upper part of the heat exchanger H3 is connected with an interface 2-4 of A1, and the lower part of the heat exchanger H3 is connected with an interface 2-6 of A1;
the lower part of the heat exchanger H4 is sequentially connected with AB1 and PVO 1;
PVO1 is connected with AB 2; AB2 is connected to interfaces 3-4 of A2.
The steam outlet W2 is respectively connected with R1 and H1, and the residue outlet W3 is respectively connected with M2 and connected with the interfaces 2-8 in A1.
(1) The normal temperature air separation oxygen production device 1 directly extracts oxygen with purity of 80-99.9% from air, outputs oxygen with the same purity or different purity from interfaces 1-1 and 1-2 according to an air supply loop designed as shown in the figure, pre-mixes the prepared oxygen with partial flue gas discharged by a system to oxygen-enriched air (preferably, the oxygen-enriched air is enriched to 23-40% and non-oxygen component is carbon dioxide) with oxygen volume percentage of ≧ 21%, then preheats to 100-200 ℃ through a preheater H3, and respectively sends the oxygen to interfaces 2-5 and 2-4 of a first circulating fluidized bed A1 to serve as oxygen sources of oxidation reaction, the pressure of the oxygen meets the requirement of suspension gasification, and specifically provides 5-30 kpa of wind pressure.
(2) The preheated rich oxygen is sent into the first circulating fluidized bed A1 to carry out oxidation reaction with biomass fuel in the bed, the following reactions in the chemical reaction process of the coal gasification layer are completed in the bed, heat is released, and the heat energy required by the whole system is maintained:
C+ O2 = CO2 + Q， （1）
2C + O2 = 2CO + Q 2CO + O2 = 2CO2 + Q ， （2）
when the system is started, the initial fuel needed by the first circulating fluidized bed A1 is fed from an interface 2-1, the initial fuel is the initial feeding of low-calorific-value fuel such as biomass and the like from a feeder Q1, the oxygen enrichment is obtained by premixing prepared oxygen and air to obtain oxygen enrichment (most of non-oxygen components of the oxygen enrichment are nitrogen), when the whole system normally operates, the fuel gradually comes from a cyclone separator F2 at the side of the second circulating fluidized bed A2, a ceramic membrane separator M1 and the like to intercept un-gasified carbon-containing materials which are fed reversely and are not gasified and residual carbon from an overflow outlet 3-3 of the second circulating fluidized bed A2, and is accessed from an interface 2-6 of the first circulating fluidized bed A1, and the oxygen enrichment replaces the prepared oxygen enrichment and part of flue gas discharged by the system to premix oxygen-enriched air with the oxygen volume percentage of not less than 21% (preferably, the oxygen enrichment is 23-40%, wherein the non-oxygen components are carbon dioxide); the reaction temperature is controlled to be 800-950 ℃; wherein the interfaces 2-7 introduce nitrogen gas generated by the oxygen-nitrogen separation device 1 as a protective purge gas in an emergency; the interface 2-8 is used for discharging solid residues burnt out by the first circulating fluidized bed A1 and returning the solid residues to the field after elements such as beneficial sylvite and the like are added.
(3) High-temperature flue gas generated by the first circulating fluidized bed A1 is discharged from a connector 2-2, and is separated from non-burnt high-temperature materials in the first circulating fluidized bed A1 through a cyclone separator F1, wherein the flue gas is subjected to heat exchange by-product steam of heat exchangers H1, H2, H3 and H4 and is directly output from a steam outlet W2 as a product, and can also be sent to a turbine for power generation; meanwhile, the separated high-temperature material and the high-temperature material from the middle overflow outlet of the interface 2-3 of the first circulating fluidized bed A1 are sent into the interface 3-3 of the second circulating fluidized bed A2 to be used as main reaction raw materials of the first high-temperature circulating fluidized bed A1.
(4) In the second circulating fluidized bed A2, the high-temperature materials from the middle connector 2-3 of the first circulating fluidized bed A1 and the high-temperature materials separated by the cyclone separator F1 and the low-heating-value fuels such as biomass from the connector 3-1 are continuously fed, and the main reduction chemical reaction process of a coal gasification layer is generated in the second circulating fluidized bed:
c + H2O (vapour) = CO + H2-Q, (3)
C + 2H2O (vapour) = CO2 + 2H2-Q, (4)
C + CO2 = 2CO – Q ， (5)
The steam is from the byproduct steam, is decompressed and then is sent in by a discharger R1, R2, R3 and R4, the temperature is controlled to be 150-250 ℃, the pressure is 0.15MPa, the heat energy required by the main endothermic reaction comes from the high-temperature material brought in by a first circulating fluidized bed A1, the circulating carrier gas comes from the self-produced gas accessed from an interface 3-4, the severe gasification reaction is generated in the bed together with carbon and the like in low-heat-value fuels such as biomass and the like, the reaction temperature is controlled to be 700-850 ℃, the reaction process is completed in an oxygen-deficient state (usually, the volume percentage of oxygen is less than or equal to 1 percent), high-heat-value fuel gas mainly containing hydrogen, carbon monoxide and methane and containing nitrogen less than or equal to 5 percent is generated, the high-heat-value fuel gas is led out from the interface 3-2, and the interface 3-5 is used for introducing nitrogen generated by a normal-temperature air separation device 1 to be used as protective purging gas in an emergency situation.
(5) Leading the fuel gas with high calorific value out from the interface 3-2 and separating high-temperature materials which are not completely gasified and reacted by a cyclone separator F2; and then the solid phase components in the high-temperature materials are thoroughly intercepted by a first-stage ceramic membrane filter M1, the high-temperature materials are circularly returned from the discharger R2, R3 and R4 at the outlet of the separator and are sent into the first circulating fluidized bed A1 for combustion chemical reaction, the high-temperature fuel gas in the high-temperature materials passes through a heat exchanger (group) H4 to adjust the output temperature of the high-temperature fuel gas, simultaneously recover heat energy and improve the quality of steam, the high-temperature fuel gas is output as a product, the hot fuel gas can be directly combusted, and carbon monoxide in the hot fuel gas can be continuously converted into hydrogen to extract the hydrogen and the like in the hot fuel gas.
(6) The high-heat value gas is generated through the process, and the gas pressure is increased by the high-temperature gas pressure increasing device AB1 according to the working pressure required by a client and is output as product gas. Wherein, a part of the waste gas is sent to a terminal gas using point (such as direct combustion, power generation or further hydrogen purification) through a buffer tank PV01; and the other part is used for boosting part of the coal gas through another high-temperature coal gas boosting device AB2 according to the pressure requirement, and the coal gas is used as carrier gas of the second circulating fluidized bed A2 for circulation, so that the pressure is boosted to the wind pressure requirement of 5-30 kpa.
(7) The high-temperature flue gas generated by the first circulating fluidized bed A1 passes through a multi-stage heat exchanger H1, H2, H3 and H4 to recover heat energy, a high-temperature and high-pressure steam is generated as a byproduct, the flue gas passes through a ceramic membrane filter M2 to thoroughly intercept solid phase components contained in the flue gas, and the pressure loss of the flue gas is provided by another high-temperature flue gas pressure boosting device AB3, so that on one hand, the high-temperature flue gas is used for overcoming the filtration and the loss along the process resistance, and on the other hand, the high-temperature flue gas is used for circularly returning oxygen prepared by a system which directly extracts the oxygen with the purity of 80-99.9% from the air by the normal-temperature air separation (membrane separation or pressure swing adsorption method) technology, and the oxygen is premixed to be not less than 21% of oxygen-enriched air with the oxygen volume percentage (wherein non-oxygen components are carbon dioxide) to provide oxygen for the oxidation reaction process.
The low-calorific-value fuel such as biomass is cut into pieces of about 50mm, the pieces are fed from a feeding machine interface Q1, make-up water is fed from a water inlet device interface Q2, oxygen is fed from an oxygen interface Q3 by an oxygen-nitrogen separation device, through the gasification and conversion process, under the action of a control system, the cyclic gasification and conversion of the low-calorific-value fuel such as biomass can be continuously realized, high-calorific-value fuel gas with high effective components such as hydrogen and carbon monoxide is generated and output from a fuel gas outlet W1 (the effective components in the high-calorific-value fuel gas can be continuously purified), high-temperature high-pressure steam is output from a steam outlet W2 (the high-temperature high-pressure steam can also be used for continuously generating electricity), high-quality plant ash is output from a residue outlet W3 (beneficial sylvite and other elements are added to form organic fertilizer to return to the field), flue gas rich in carbon dioxide (the content is not less than 80%) is output from a flue gas outlet W4 (a proper three-phase point can be selected to liquefy), and a small amount of heat exchange wastewater is discharged from a wastewater discharge outlet W5. Therefore, the low-calorific-value fuel gasification process which adopts carbon dioxide background gas mixed with pure oxygen as oxygen enrichment and steam as a gasification agent effectively reduces the nitrogen content, can efficiently convert effective components of the low-calorific-value fuel into high-calorific-value fuel gas which mainly contains hydrogen and carbon monoxide and contains nitrogen less than or equal to 5%, can convert 70-75% of the effective heat energy into fuel gas and 15-20% of the effective heat energy into steam or electric power, completes the efficient conversion of low-calorific-value fuels such as biomass and the like, has simple operation, high automation degree and good economic benefit, and has remarkable advantages compared with the conventional coal gasification process which takes coal as fuel.
The invention is preferably applied to gasification conversion of low-heating-value fuels such as biomass and the like, but does not represent application of the method of the invention to other fuels (typically high-quality fuels such as fire coal and the like), the basic principle disclosed by the invention is equally suitable, and typical examples which can be realized by the method of the invention comprise application to conversion of all fuels, such as solid fuels into gaseous fuels, carbon-containing fuels into hydrogen and the like.
The above-described embodiments of the invention only set forth some of the essential features of the invention, and it should be understood by those skilled in the art that although the invention has been described in part in connection with the accompanying drawings, this is merely an example of the invention or a method of its application, and all other variations which do not depart from the essence of the invention set forth in this patent are intended to fall within the scope of the invention, which is limited only by the scope of the appended claims.
The foregoing invention has been described in some detail by way of illustration and example, and it is not to be construed as limited the scope of the invention as defined by the appended claims.
Claims (2)
1. The device for gasification and conversion of the low-heating-value fuel is characterized in that oxygen enrichment, oxygen depletion and steam with specific components are adopted as gasification agents to perform gasification and conversion on the low-heating-value fuel, and the structure of the device comprises:
(1) At least one set of normal temperature air separation oxygen generating device is used for directly extracting oxygen with the purity of 80-99.9% from the air;
(2) At least one set of first circulating fluidized bed (also called oxygen-enriched gasification reaction bed) is used for carrying out oxidation exothermic reaction in the main chemical reaction process of the coal gasification layer and providing heat energy for the whole system; and the source of the oxidant in the circulating fluidized bed is oxygen-enriched air with the oxygen volume percentage being equal to or larger than 21% after the oxygen provided by the oxygen generating device is mixed with the carbon dioxide in the flue gas;
(3) At least one set of high-temperature flue gas cyclone separator is used for separating high-temperature materials which are not burnt out from the first circulating fluidized bed; wherein, the flue gas exchanges heat through a set of heat exchangers and produces steam as a byproduct, and the separated high-temperature material and the high-temperature material overflowing from the middle part of the first circulating fluidized bed are sent into a second circulating fluidized bed;
(4) At least one set of second circulating fluidized bed, also called lean oxygen gasification reaction bed, is used for carrying out reduction gas making reaction in the main chemical reaction process of the coal gasification layer; the gasification agent steam is fed after being decompressed from the byproduct steam, heat energy is from high-temperature materials brought in by the first circulating fluidized bed and carbon in the biomass low-heating-value fuel to generate high-heating-value fuel gas which mainly contains hydrogen, carbon monoxide and methane and contains nitrogen less than or equal to 5%, wherein part of the fuel gas is circularly returned to the second circulating fluidized bed to serve as carrier gas;
(5) At least one set of high-temperature coal gas cyclone separator is used for separating high-temperature materials which are not completely gasified in the second circulating fluidized bed; meanwhile, a ceramic membrane filter is matched to thoroughly intercept solid-phase components in the high-temperature coal gas, and the high-temperature coal gas is recycled and returned to the first circulating fluidized bed for combustion chemical reaction;
(6) The at least one set of heat exchanger is used for adjusting the output temperature of the high-temperature fuel gas, recovering heat energy and improving the quality of steam;
(7) At least one set of high-temperature coal gas pressure boosting device is used for boosting the gas pressure, wherein one part of the high-temperature coal gas pressure boosting device is sent to a terminal gas using point, and the other part of the high-temperature coal gas pressure boosting device boosts partial coal gas and circulates the boosted coal gas as the carrier gas of the second circulating fluidized bed;
(8) At least one ceramic membrane filter, which is used for thoroughly intercepting solid phase components in hot flue gas of heat energy byproduct steam recovered from a first circulating fluidized bed through a heat exchanger, wherein the pressure loss of the solid phase components is provided by a set of high-temperature flue gas pressure boosting device, on one hand, the ceramic membrane filter is used for overcoming the filtration and the on-way resistance loss, on the other hand, the ceramic membrane filter is used for circularly returning oxygen prepared by a system which directly extracts oxygen with the purity of 80-99.9% from air by the normal-temperature air separation oxygen generation device, and the oxygen is premixed to oxygen-enriched air with the oxygen volume percentage of not less than 21% so as to provide oxygen for the oxidation reaction process;
(9) The control system is used for controlling the on-off/switching of the field equipment and realizing the continuous cyclic gasification process;
the "oxygen enrichment" refers to oxygen-enriched air with the oxygen volume percentage of not less than 21% obtained by premixing prepared oxygen and part of flue gas discharged by the system, and the "oxygen deficiency" refers to oxygen-deficient air with the oxygen volume percentage of not less than 1%.
2. The method for gasification conversion of low heating value fuel based on the device of claim 1 is characterized by comprising the following specific steps:
(1) Directly extracting oxygen with the purity of 80-99.9% from air by adopting a normal-temperature air separation oxygen generation device, premixing the prepared oxygen and part of flue gas discharged by a system until the oxygen-enriched air with the oxygen volume percentage of not less than 21% is preheated to 100-200 ℃, and then sending the oxygen to a first circulating fluidized bed as an oxygen source of an oxidation reaction, wherein the pressure of the oxygen meets the requirement of suspension gasification, namely the air pressure requirement of 5-30 kpa is met;
(2) The preheated rich oxygen is sent into the first circulating fluidized bed to carry out oxidation reaction with biomass fuel in the bed, namely the following chemical reactions are completed in the bed, heat is released, and heat energy required by the whole system is maintained:
C+ O2 = CO2 + Q ， （1）
2C + O2 = 2CO + Q ，2CO + O2 = 2CO2 + Q ， （2）
when the system is started, the initial fuel required by the first circulating fluidized bed is from the initial feeding of the low-calorific-value fuel, the oxygen enrichment is obtained by premixing the prepared oxygen and air, when the whole system normally operates, the fuel gradually comes from un-gasified carbonaceous materials reversely fed from the cyclone separator and the ceramic membrane separator on the side of the second circulating fluidized bed, and the oxygen enrichment replaces the prepared oxygen enrichment and part of flue gas discharged by the system to be premixed to oxygen-enriched air with the volume percentage of oxygen being not less than 21%; the reaction temperature is controlled to be 800-950 ℃;
(3) High-temperature flue gas generated by the first circulating fluidized bed passes through a cyclone separator to separate high-temperature materials which are not burnt out from the first circulating fluidized bed; wherein, the flue gas is directly output as a product by the steam generated by heat exchange of the heat exchanger, or sent to a turbine for power generation; meanwhile, the separated high-temperature materials and the high-temperature materials overflowing from the middle part of the first circulating fluidized bed are sent into a second circulating fluidized bed to be used as a main heat energy source of the high-temperature first circulating fluidized bed;
(4) In the second circulating fluidized bed, the high-temperature material overflowed from the middle part of the first circulating fluidized bed and the high-temperature material separated by the cyclone separator and the continuous feeding of the low-heating-value fuel are subjected to the following reduction chemical reaction processes in the second circulating fluidized bed:
c + H2O (vapour) = CO + H2-Q, (3)
C + 2H2O (vapour) = CO2 + 2H2-Q, (4)
C + CO2 = 2CO – Q， （5）
Wherein the steam is from the byproduct steam, is sent after pressure reduction, and is controlled at the temperature of 150-250 ℃; the heat energy required by endothermic reaction comes from high-temperature materials brought in by the first circulating fluidized bed, the circulating carrier gas comes from self-produced coal gas, and the second circulating fluidized bed and carbon and the like in low-calorific-value fuels such as biomass and the like generate violent gasification reaction in the second circulating fluidized bed, the reaction temperature is controlled to be 700-850 ℃, the reaction process is completed in an oxygen-deficient state, and high-calorific-value fuel gas which mainly contains hydrogen, carbon monoxide and methane and contains nitrogen less than or equal to 5% is generated;
(5) Separating high-temperature materials which are not completely gasified in the generated high-calorific-value fuel gas by a cyclone separator, and thoroughly intercepting solid-phase components in the high-calorific-value fuel gas by a first-stage ceramic membrane filter; the high-temperature materials are circularly returned to be sent into the first circulating fluidized bed to carry out combustion chemical reaction, and the high-temperature fuel gas in the high-temperature materials passes through the heat exchanger to adjust the output temperature of the high-temperature fuel gas, recover heat energy and improve the quality of steam to be output as a product;
(6) Generating high-heat-value gas, increasing the gas pressure by a high-temperature gas pressure increasing device according to the working pressure required by a client, outputting the gas as product gas, wherein one part of the product gas is sent to a terminal gas using point, the other part of the product gas is increased in pressure by the high-temperature gas pressure increasing device according to the pressure requirement, and is used as carrier gas of a second circulating fluidized bed for circulation, and the pressure is increased to the wind pressure requirement of 5-30 kpa;
(7) The high-temperature flue gas generated by the first circulating fluidized bed passes through a multistage heat exchanger to recover heat energy, high-temperature and high-pressure steam is generated as a byproduct, the flue gas passes through a ceramic membrane filter to thoroughly intercept solid-phase components contained in the flue gas, the pressure loss of the flue gas is provided by a set of high-temperature flue gas pressure boosting device, on one hand, the high-temperature flue gas pressure boosting device is used for overcoming the filtration and the on-way resistance loss, on the other hand, the high-temperature flue gas pressure boosting device is used for circularly returning oxygen prepared by a system which directly extracts oxygen with the purity of 80-99.9% from air by the normal-temperature air separation oxygen generation device, and the oxygen is premixed to oxygen-enriched air with the oxygen volume percentage of not less than 21% so as to provide oxygen for the oxidation reaction process;
and continuously carrying out the cyclic gasification conversion process of the low-heating-value fuel under the action of the control system.
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| CN116864733A (en) * | 2023-05-05 | 2023-10-10 | 武汉雄韬氢雄燃料电池科技有限公司 | Oxygen enrichment device for high-power fuel cell and high-power fuel cell system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116864733A (en) * | 2023-05-05 | 2023-10-10 | 武汉雄韬氢雄燃料电池科技有限公司 | Oxygen enrichment device for high-power fuel cell and high-power fuel cell system |
| CN116864733B (en) * | 2023-05-05 | 2024-02-27 | 武汉雄韬氢雄燃料电池科技有限公司 | Oxygen enrichment device for high-power fuel cell and high-power fuel cell system |
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