Disclosure of Invention
Technical problem to be solved
The application provides a coal staged gasification method and device based on chemical looping combustion, which at least solve the technical problems.
(II) technical scheme
The invention provides a coal staged gasification method based on chemical looping combustion, which comprises the following steps: s1, heating coal by adopting first heat to generate coke and coke oven gas; s2, heating the coke and the first part of carbon dioxide by using second heat so that the coke and the first part of carbon dioxide react to generate carbon monoxide; s3, reacting part of the carbon monoxide with the oxidation state metal oxygen carrier to generate a second part of carbon dioxide and reduction state metal oxygen carrier; s4, reacting the reduced metal oxygen carrier with hot air to generate an oxidized metal oxygen carrier and high-temperature flue gas; s5, reacting the other part of carbon monoxide with water vapor to generate hydrogen and a third part of carbon dioxide; wherein the first portion of carbon dioxide comprises at least a second portion of carbon dioxide and a third portion of carbon dioxide.
Optionally, the high temperature flue gas releases the first heat and the second heat.
Optionally, the high temperature flue gas heats the air to generate hot air after releasing the first heat and the second heat.
Optionally, the reaction temperature of part of the carbon monoxide reacting with the oxidized form metal oxygen carrier in step S3 is 1200-1700 ℃.
Optionally, the reaction temperature of the reduced metal oxygen carrier and the hot air in the step S4 is 1100-1500 ℃.
The invention provides a coal grading gasification device based on chemical looping combustion, which comprises: the carbonization unit is used for heating coal by adopting first heat to generate coke and coke oven gas; the coke gasification unit is used for heating the coke and the first part of carbon dioxide by adopting second heat so as to enable the coke and the first part of carbon dioxide to react to generate carbon monoxide; a fuel reaction unit for reacting a portion of the carbon monoxide with the oxidized form of the metal-oxygen carrier to produce a second portion of carbon dioxide and a reduced form of the metal-oxygen carrier; the air reaction unit is used for reacting the reduced metal oxygen carrier with hot air to generate an oxidized metal oxygen carrier and high-temperature flue gas; the shift hydrogen production unit is used for reacting the other part of carbon monoxide with water vapor to generate hydrogen and a third part of carbon dioxide; wherein the first portion of carbon dioxide comprises at least the second portion of carbon dioxide and a third portion of carbon dioxide.
Optionally, the device further comprises a heat transfer unit for releasing the first heat and the second heat from the high-temperature flue gas.
Optionally, the device further comprises an air preheating unit for heating the air to generate hot air after the high-temperature flue gas releases the first heat and the second heat.
Optionally, the reaction temperature of the carbonization unit is 700-1100 ℃.
Optionally, the reaction temperature of the hydrogen conversion unit is 200-400 ℃.
(III) advantageous effects
The chemical chain conversion technology is combined with the coal gasification technology, so that carbon dioxide generated by carbon monoxide chemical chain combustion is used as a non-metallic oxide oxygen carrier, solid-solid reaction between an oxygen carrier and coke in the coal gasification process is avoided, the problems of solid-solid separation and oxygen carrier pollution are solved, the coal gasification efficiency is improved, and the coal gasification device has wide social benefits and industrial application prospects.
Detailed Description
The invention provides a coal staged gasification method based on chemical looping combustion, which comprises the following steps of: s1, heating coal by adopting first heat to generate coke and coke oven gas; s2, heating the coke and the first part of carbon dioxide by using second heat so that the coke and the first part of carbon dioxide react to generate carbon monoxide; s3, reacting part of the carbon monoxide with the oxidation state metal oxygen carrier to generate a second part of carbon dioxide and reduction state metal oxygen carrier; s4, reacting the reduced metal oxygen carrier with hot air to generate an oxidized metal oxygen carrier and high-temperature flue gas; s5, reacting the other part of carbon monoxide with water vapor to generate hydrogen and a third part of carbon dioxide; wherein the first portion of carbon dioxide comprises at least a second portion of carbon dioxide and a third portion of carbon dioxide.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings 1 in conjunction with specific embodiments.
And S1, heating coal by adopting the first heat to generate coke and coke oven gas.
The process can be expressed as a carbonization process of coal, the carbonization and purification of raw material coal can be realized through the process, the required heat can be provided by the following steps S3 and S4, and chemical products such as crude coke, coke oven gas, tar and the like can be obtained. The reaction temperature in the process is preferably 700-1100 ℃, and when the temperature is reduced to 600-900 ℃, the products are coke, coke oven gas, tar and the like. The process can be realized in a heating furnace, a soaking furnace or a calcining furnace in the metallurgical industry.
And S2, heating the coke and the first part of carbon dioxide by using the second heat so that the coke and the first part of carbon dioxide react to generate carbon monoxide.
The process can realize gasification of the coke, the coke obtained in the step S1 reacts with carbon dioxide to generate carbon monoxide, the carbon monoxide can be realized in the coke gasification unit, the hot coke (about 1000 ℃) obtained in the step S1 enters from the top of the coke gasification unit, the carbon dioxide enters from the bottom of the coke gasification unit, the coke and the carbon dioxide meet to generate gasification reaction, the coke is gasified into the carbon monoxide, and the carbon monoxide is discharged from the upper part of the coke gasification unit. The required amount of heat may also be provided by the following steps S3 and S4 processes. The carbon dioxide required for this can be provided at least by steps S3 and S5. The coke gasification reaction temperature is 1100 ℃, and the carbon conversion rate is 95%.
Part of carbon monoxide generated in the process participates in the chemical looping combustion process, and the other part of carbon monoxide participates in the hydrogen conversion process. Wherein, the chemical looping combustion process includes a fuel reaction process and an air reaction process, which can be respectively realized by the following steps S3 and S4. The shift hydrogen production process may be implemented by step S5.
And S3, reacting part of the carbon monoxide with the oxidation state metal oxygen carrier to generate a second part of carbon dioxide and reduction state metal oxygen carrier.
The process is a fuel reaction process in a chemical looping combustion process. A portion of the carbon monoxide produced by the char gasification process reacts with the oxidized form of the metal-oxygen carrier to produce a second portion of carbon dioxide and reduced form of the metal-oxygen carrier. The metal oxygen carrier may be Fe2O3With Fe3O4. The reaction temperature in the fuel reaction process is preferably 1200-1700 ℃.
And S4, reacting the reduced metal oxygen carrier with hot air to generate an oxidized metal oxygen carrier and high-temperature flue gas.
The process is an air reaction process in a chemical looping combustion process. And (4) reacting the reduced metal oxygen carrier obtained in the step (S3) with hot air to generate an oxidized metal oxygen carrier and high-temperature flue gas. After the high temperature flue gas is coarsely dedusted, the heat transfer unit can provide the first heat and the second heat required by steps S1 and S2. The high-temperature flue gas releases the first heat and the second heat and then heats air to generate hot air required by the step, the temperature is about 1050 ℃, and the flue gas is discharged below 200 ℃ after waste heat recovery. The temperature in the air reaction process can be 1100-1500 ℃.
S5, reacting the other part of carbon monoxide with water vapor to generate hydrogen and a third part of carbon dioxide; wherein the first portion of carbon dioxide comprises at least a second portion of carbon dioxide and a third portion of carbon dioxide.
And reacting the other part of carbon monoxide with water vapor to generate hydrogen and a third part of carbon dioxide, separating by using a separation device to obtain carbon dioxide and pure hydrogen, and returning the separated carbon dioxide to the carbon monoxide production process to continuously react with coke. The temperature of the transformation reaction in the transformation hydrogen production process is about 200-400 ℃. The third portion of carbon dioxide participates in step S2 along with the second portion of carbon dioxide generated in step S3. A part of the carbon monoxide generated in step S2 participates in step S3, another part thereof participates in step S5, and a part thereof is outputted as carbon monoxide.
The three gases of coke oven gas, carbon monoxide and hydrogen can be obtained by the process.
The chemical chain conversion technology is combined with the coal gasification technology, and a novel coal gasification mode of 'component alignment and graded conversion' of coal is realized. The carbon dioxide generated by the combustion of the carbon monoxide chemical chain is taken as the oxygen carrier of the non-metallic oxide, so that the solid-solid reaction between the oxygen carrier and the coke in the coal gasification process is avoided, the problems of solid-solid separation and oxygen carrier pollution are avoided, the coal gasification efficiency is improved, and the method has wide social benefits and industrial application prospects.
Another aspect of the present application provides a coal staged gasification device based on chemical looping combustion, as shown in fig. 2, including a carbonization unit 1, a coke gasification unit 2, an air reaction unit 4, a fuel reaction unit 5, and a conversion hydrogen production unit 3, wherein:
the carbonization unit 1 can be implemented, for example, as step S1, for heating coal 10 with a first heat to generate coke 13 and coke oven gas 12. Tar 11 may also be produced.
The char gasification unit 2, for example, may be implemented as step S2 for heating the char 13 and the first portion of carbon dioxide with the second heat to react the char 13 and the first portion of carbon dioxide to generate carbon monoxide. The reaction temperature of the carbonization unit is 700-1100 ℃.
The fuel reaction unit 5 may, for example, be realized as step S3 for reacting a portion of the carbon monoxide 17 with the oxidized form of the metal-oxygen carrier 19 to produce a second portion of carbon dioxide 16 and a reduced form of the metal-oxygen carrier 18.
The air reaction unit 4, for example, can be implemented as step S4, for reacting the reduced metal-oxygen carrier 18 with the hot air 21 to generate the oxidized metal-oxygen carrier 19 and the high temperature flue gas 20.
The shift hydrogen-producing unit 3 may be implemented, for example, as step S5 for reacting another portion of the carbon monoxide 14 with the water vapor 25 to produce hydrogen 24 and a third portion of the carbon dioxide 15. The carbon monoxide 14 reacts with the steam 25 to produce hydrogen 24 and a third portion of carbon dioxide 15.
Wherein the first portion of carbon dioxide comprises at least a second portion of carbon dioxide 16 and a third portion of carbon dioxide 15.
The coal grading gasification device also comprises a heat transfer unit 7 and an air preheating unit 6. The heat transfer unit 7 is used for releasing the first heat and the second heat from the high-temperature flue gas 20, and the air preheating unit 6 is used for heating the air 23 to generate hot air 21 after the first heat and the second heat are released from the high-temperature flue gas 20. By the surface type heat transfer unit 7, the heat loss in the heat transfer process is about 9% of the heat release. The air preheating unit 6 comprises a heat accumulating type waste heat recovery unit and a dividing wall type waste heat recovery unit.
After high-temperature flue gas generated in the chemical looping combustion process is subjected to coarse dust removal, the high-temperature flue gas passes through the heat transfer unit 7 and releases first heat and second heat to the carbonization unit 1 and the coke gasification unit 2 through the partition walls 8 and 9 respectively. The high-temperature flue gas 20 after releasing heat exchanges heat with air 23 in the air preheating unit 6 to obtain low-temperature flue gas 22 and hot air 21, the hot air 21 enters the air reactor 4 to react with the reduced-state metal oxygen carrier 18, and the low-temperature flue gas 22 is directly discharged. The reduced metal oxygen carrier 18 is oxidized into an oxidized metal oxygen carrier 19 in the air reactor 4, the oxidized metal oxygen carrier 19 is separated and then enters the fuel reactor 5 to react with carbon monoxide 17 generated in the coke gasification process to generate the reduced metal oxygen carrier 18 and carbon dioxide 16, wherein the reduced metal oxygen carrier 18 is recycled to the air reactor 4, and the carbon dioxide 16 returns to the coke gasification unit 2 to react with the crude coke 13.
Table 1 shows the energy input and output under the conditions of the examples, wherein the carbon dioxide separation work required by the shift unit is small in proportion due to the large part of the carbon dioxide provided by the chemical looping combustion technique.
TABLE 1
The coal grading gasification method based on chemical chain conversion provided by the application has the advantages that the cold coal gas efficiency can reach 89.8% under the embodiment, the gasification efficiency is 92.7%, and the coal grading gasification method is relatively high in improvement compared with the traditional gasification method.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.