High-alkali coal gradient utilization system and method coupling fuel pretreatment and oxygen-enriched combustion

Abstract

The invention discloses a fuel pretreatment and oxygen-enriched combustion coupled high-alkali coal gradient utilization system and method.The system comprises a boiler body connected with a semicoke outlet of a pyrolysis gasification furnace, a high-temperature flue gas outlet of the boiler body is connected with a flue gas inlet of the pyrolysis gasification furnace, and a synthesis gas outlet of the pyrolysis gasification furnace is connected with a high-temperature synthesis gas inlet of a heat exchanger; a low-temperature synthesis gas outlet of the heat exchanger is connected with an inlet of the cyclone separator, a liquid-solid mixture outlet of the cyclone separator is connected with an inlet of the centrifugal separator, a gas outlet of the cyclone separator is connected with an inlet of the electric precipitator, and a synthesis gas outlet of the electric precipitator is connected with an inlet of the synthesis gas storage equipment; a flue gas inlet of an air pre-heater arranged in a boiler body is communicated with the boiler body, an oxygen inlet of the air pre-heater is connected with an oxygen outlet of air separation equipment, flue gas flowing out of the flue gas outlet of the air pre-heater enters flue gas treatment equipment and a heat exchanger through the flue gas outlet of the boiler body, and oxygen flowing out of the oxygen outlet of the air pre-heater is mixed with high-temperature flue gas and enters the boiler body. The efficient and safe utilization of the high-alkali coal is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of efficient utilization of coal and carbon emission reduction, and specifically is a high-alkali coal cascade utilization system and method coupled with fuel pretreatment and oxygen-enriched combustion. Background Art

[0002] my country has abundant reserves of high-alkali coal (such as Zhundong coal). Usually, according to the different reaction characteristics of the same components in coal, the pyrolysis, gasification and combustion reactions of coal are combined to achieve the cascade utilization of high-alkali coal, thereby improving the utilization efficiency of high-alkali coal, reducing pollutant emissions, and obtaining high-value-added products such as coal gas and tar. However, when coal is burned, a large amount of CO is released. 2 Greenhouse gases and nitrogen oxides NO x Moreover, due to the high content of alkali metals in high-alkali coal, it is easy to cause ash and slagging in the boiler, which is not conducive to the safe and stable operation of the boiler, and increases economic costs and safety hazards.

[0003] Oxygen-enriched combustion technology is to mix pure oxygen with recycled flue gas and use it instead of air as the combustion-supporting gas, which can greatly increase the CO content in flue gas. 2 content, which is convenient for CO 2 Large-scale capture and storage of NO x The emission of atmospheric pollutants such as coal can be reduced, and it is expected that the efficient and clean utilization of high-alkali coal can be achieved. For example, Chinese invention patents CN202111290416.8 and CN201410030446.9 involve the coupling of fuel cascade utilization and oxygen-enriched combustion systems, which not only improves the fuel utilization efficiency, obtains chemical products such as coal gas and tar, but also achieves carbon emission reduction.

[0004] However, how to couple the oxygen-enriched combustion technology with the high-alkali coal cascade utilization system to simultaneously improve fuel utilization, reduce carbon emissions, reduce the alkali metal content fed into the boiler, and reduce NO x The emission of pollutants such as carbon monoxide and other pollutants still needs to be studied. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a high-alkali coal cascade utilization system and method that couples fuel pretreatment and oxygen-enriched combustion, which not only realizes the efficient, clean and safe utilization of high-alkali coal, but also effectively ensures the safe and stable operation of the boiler.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A high-alkali coal cascade utilization system coupling fuel pretreatment and oxygen-enriched combustion, comprising a boiler body, a pyrolysis gasifier, a heat exchanger, a cyclone separator, a centrifugal separator, an electrostatic precipitator, a synthesis gas storage device, an air separation device, an air preheater and a flue gas treatment device;

[0008] The high-temperature flue gas outlet of the boiler body is connected to the flue gas inlet of the pyrolysis gasifier, the semi-coke outlet of the pyrolysis gasifier is connected to the boiler body, the high-temperature semi-coke generated by the reaction of the high-alkali coal in the pyrolysis gasifier is sent into the boiler body by the combustion-supporting gas, and the amount of oxygen in the combustion-supporting gas is lower than the amount of oxygen required for the complete combustion of the high-temperature semi-coke, the high-temperature synthesis gas outlet of the pyrolysis gasifier is connected to the high-temperature synthesis gas inlet of the heat exchanger, the low-temperature synthesis gas outlet of the heat exchanger is connected to the inlet of the cyclone separator, the liquid-solid mixture outlet of the cyclone separator is connected to the inlet of the centrifugal separator, the gas outlet of the cyclone separator is connected to the inlet of the electrostatic precipitator, and the synthesis gas outlet of the electrostatic precipitator is connected to the inlet of the synthesis gas storage device;

[0009] The air preheater is arranged inside the boiler body, and the flue gas inlet of the air preheater is connected to the boiler body, the oxygen inlet of the air preheater is connected to the oxygen outlet of the air separation equipment, the flue gas outlet of the air preheater is connected to the low-temperature flue gas outlet of the boiler body, the low-temperature flue gas outlet of the boiler body is respectively connected to the flue gas inlet of the flue gas treatment equipment and the low-temperature flue gas inlet of the heat exchanger, the oxygen outlet of the air preheater and the high-temperature flue gas outlet of the heat exchanger are connected to the boiler body through a pipeline, and the high-temperature oxygen from the air preheater and the high-temperature flue gas from the heat exchanger are mixed in the pipeline and then introduced into the boiler body as a combustion-supporting gas.

[0010] Furthermore, the interior of the boiler body is provided with a semi-coke combustion zone, a synthesis gas combustion reduction zone and a burnout zone in sequence from bottom to top;

[0011] After the high-temperature oxygen and high-temperature flue gas are mixed in the pipeline, a part of them enters the semi-coke combustion zone of the boiler body as combustion-supporting gas, and the other part enters the burnout zone of the boiler body.

[0012] Furthermore, the synthesis gas outlet of the electrostatic precipitator is also connected to the synthesis gas combustion and reduction zone of the boiler body.

[0013] Furthermore, a low-temperature flue gas inlet is provided above the burnout zone of the boiler body, and the low-temperature flue gas inlet is connected to the low-temperature flue gas outlet of the boiler body.

[0014] Furthermore, the outlet of the flue gas treatment equipment is connected to a carbon capture device.

[0015] A high-alkali coal cascade utilization method based on a high-alkali coal cascade utilization system coupled with fuel pretreatment and oxygen-enriched combustion comprises the following steps:

[0016] Step 1, feeding high-alkali coal into a pyrolysis gasification furnace, generating high-temperature semi-coke and high-temperature crude synthesis gas after pyrolysis and gasification reactions, wherein part of the alkali metal in the high-alkali coal is volatilized and mixed in the high-temperature crude synthesis gas, and the remaining alkali metal is mixed in the high-temperature semi-coke;

[0017] Step 2, the high-temperature semi-coke is sent into the boiler body by the combustion-supporting gas for combustion. The internal combustion of the boiler body generates high-temperature flue gas, which flows downstream and the temperature gradually decreases. When the temperature of a part of the high-temperature flue gas drops to 700-900°C, it enters the pyrolysis gasifier as a heat source and gasification agent, and the other part of the high-temperature flue gas continues to flow downstream and the temperature continues to decrease, and then enters the air preheater, exchanges heat with the low-temperature oxygen from the air separation equipment, forms low-temperature flue gas and flows through the flue gas outlet of the air preheater and the low-temperature flue gas outlet of the boiler body in turn. A part of the low-temperature flue gas enters the flue gas treatment equipment for purification, and a part of the low-temperature flue gas enters the heat exchanger;

[0018] The high-temperature crude synthesis gas enters the heat exchanger, and after heat exchange with the low-temperature flue gas from the air preheater, the gaseous alkali metal carried by it is first condensed and then solidified. As the low-temperature crude synthesis gas enters the cyclone separator, the cyclone separator separates the gas from the liquid-solid mixture in the low-temperature crude synthesis gas. The separated gas enters the electrostatic precipitator, and after impurities are removed, pure synthesis gas is obtained. The pure synthesis gas is stored in the synthesis gas storage equipment. The separated liquid-solid mixture enters the centrifugal separator for liquid-solid separation, thereby separating the tar and the solid particles rich in alkali metals carried by the low-temperature crude synthesis gas, and obtaining solid residue and tar respectively;

[0019] The low-temperature flue gas and the high-temperature crude synthesis gas are heat exchanged inside the heat exchanger to form high-temperature flue gas. The high-temperature flue gas is mixed with the high-temperature oxygen from the air preheater to form a high-temperature oxygen / flue gas mixture. The high-temperature oxygen / flue gas mixture is used as a combustion-supporting gas to send the high-temperature semi-coke into the boiler body for combustion.

[0020] Furthermore, part of the low-temperature flue gas in step 2 enters the flue gas treatment equipment, part enters the heat exchanger, and the other part is transported to the top of the burnout zone of the boiler body to reduce the temperature of the flue gas inside the boiler body.

[0021] Furthermore, part of the pure synthesis gas in step 2 is stored in the synthesis gas storage device, and the other part is transported to the synthesis gas combustion reduction zone of the boiler body to enhance the reducing atmosphere inside the boiler body.

[0022] Furthermore, a part of the high-temperature oxygen / flue gas mixture in step 2 is used as a combustion-supporting gas to deliver the high-temperature semi-coke into the semi-coke combustion zone of the boiler body, and the other part enters the burnout zone to promote the burnout of the remaining fuel.

[0023] Furthermore, the flue gas purified by the flue gas treatment equipment in step 2 is collected into the carbon capture equipment.

[0024] Compared with the prior art, the present invention has the following technical effects:

[0025] The high-alkali coal cascade utilization system of the present invention couples fuel pretreatment and oxygen-enriched combustion, and has the following advantages: first, oxygen and nitrogen in the air are separated by air separation equipment, and a mixture of oxygen and high-temperature flue gas is used instead of air as a combustion-supporting gas for semi-coke, thereby preventing nitrogen in the air from generating nitrogen oxides under high-temperature reactions. Moreover, since the amount of oxygen in the combustion-supporting gas is lower than the amount of oxygen required for complete combustion of the high-temperature semi-coke, the interior of the boiler body is a reducing atmosphere, which can inhibit the generation of nitrogen oxides. Second, the high-temperature flue gas generated inside the boiler body is used as a heat source and gasifying agent for pyrolysis and gasification reactions of high-alkali coal, thereby promoting the decomposition of high-alkali coal in the pyrolysis gasification furnace into high-temperature semi-coke and high-temperature crude synthesis gas. Since the main components of the high-temperature flue gas generated by oxygen-enriched combustion in the boiler body are carbon dioxide and water, both carbon dioxide and water can react with coal to generate combustible gas, thereby increasing the calorific value of the crude synthesis gas. Third, part of the alkali metals in the high-alkali coal are volatilized to In the high-temperature crude synthesis gas, after the high-temperature crude synthesis gas exchanges heat with the low-temperature flue gas, the gaseous alkali metals carried are first condensed and then solidified, and pass through the cyclone separator and the centrifugal separator in turn to obtain tar, pure synthesis gas and solid impurities rich in alkali metals, respectively, which reduces the content of alkali metals entering the boiler body, thereby weakening the tendency of ash accumulation and slagging in the boiler body, and effectively ensuring the safe and stable operation of the boiler; fourthly, the high-temperature flue gas and low-temperature oxygen are first exchanged with heat by the self-air preheater to form low-temperature flue gas, and then the low-temperature flue gas and the high-temperature crude synthesis gas are exchanged with heat by the heat exchanger, which is not only convenient for separating high-value-added tar, pure synthesis gas and solid impurities rich in alkali metals, but also the high-temperature flue gas / oxygen mixture as a combustion-supporting gas effectively promotes the combustion of semi-coke and improves the utilization rate of flue gas heat; fifthly, part of the flue gas generated by the boiler body is sent to the flue gas treatment equipment, and part is recycled and not discharged into the atmosphere, thereby achieving carbon emission reduction. In summary, the present invention improves the utilization rate of high-alkali coal, reduces the emissions of nitrogen oxides and carbon dioxide, reduces the amount of alkali metals in the boiler, achieves efficient, clean and safe utilization of high-alkali coal, and effectively ensures the safe and stable operation of the boiler.

[0026] The present invention sequentially arranges a semi-coke combustion zone, a synthesis gas combustion reduction zone and a burnout zone inside the boiler body from bottom to top, and delivers a high-temperature oxygen / flue gas mixture to the burnout zone of the boiler body, which can ensure the burnout of the fuel and improve the utilization rate of high-alkali coal; at the same time, the synthesis gas purified by the electrostatic precipitator is delivered to the synthesis gas combustion reduction zone of the boiler body, and the pure synthesis gas does not carry alkali metal particles, which can reduce the tendency of ash accumulation and slagging in the boiler and improve the safety and stability of boiler operation; in addition, the pure synthesis gas can enhance the reducing atmosphere of the synthesis gas combustion reduction zone, further reduce the generation of nitrogen oxides, thereby reducing the emission of nitrogen oxides and being more environmentally friendly. It can be seen that the present invention combines oxygen-enriched combustion with staged combustion, which not only reduces the generation of nitrogen oxides, but also improves the stability of boiler operation and the utilization rate of high-alkali coal.

[0027] The present invention introduces low-temperature flue gas into the upper part of the burnout zone of the boiler body, thereby reducing the flue gas temperature in the boiler body, thereby reducing the viscosity of fly ash particles, further weakening the tendency of ash accumulation and slagging in the boiler, and making the boiler operation safer and more stable.

[0028] The present invention removes impurities such as water and sulfur oxides from low-temperature flue gas through a carbon capture device and captures the flue gas into the carbon capture device for other uses, thereby achieving zero emission of carbon dioxide. This is not only environmentally friendly, but also improves the utilization efficiency of high-alkali coal. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the system structure of the present invention;

[0030] In the figure: 1. Boiler body; 2. Pyrolysis gasifier; 3. Heat exchanger; 4. Cyclone separator; 5. Centrifugal separator; 6. Electrostatic precipitator; 7. Syngas storage equipment; 8. Air separation equipment; 9. Air preheater; 10. Flue gas treatment equipment; 11. Carbon capture equipment. DETAILED DESCRIPTION

[0031] The specific contents of the present invention are further explained in detail below in conjunction with embodiments.

[0032] like Figure 1 As shown, a high-alkali coal cascade utilization system coupled with fuel pretreatment and oxygen-enriched combustion includes a boiler body 1, a pyrolysis gasifier 2, a heat exchanger 3, a cyclone separator 4, a centrifugal separator 5, an electrostatic precipitator 6, a synthesis gas storage device 7, an air separation device 8, an air preheater 9, a flue gas treatment device 10 and a carbon capture device 11;

[0033] The high-temperature flue gas outlet of the boiler body 1 is connected to the flue gas inlet of the pyrolysis gasification furnace 2. The high-temperature flue gas of more than 1000°C generated inside the boiler body 1 gradually decreases in temperature during its flow downstream. When the temperature of a part of the high-temperature flue gas drops to 700-900°C, it flows out through the high-temperature flue gas outlet of the boiler body 1 and is transported to the pyrolysis gasification furnace 2 as a heat source and gasification agent.

[0034] The boiler body 1 is provided with a semi-coke combustion zone, a synthesis gas combustion reduction zone and a burnout zone in order from bottom to top. The semi-coke outlet of the pyrolysis gasifier 2 is connected to the semi-coke combustion zone of the boiler body 1. The high-alkali coal is fed into the pyrolysis gasifier 2 through the fuel inlet of the pyrolysis gasifier 2, undergoes pyrolysis and gasification reactions, and generates high-temperature semi-coke and high-temperature crude synthesis gas. Part of the alkali metals in the high-alkali coal volatilizes and is mixed with the high-temperature crude synthesis gas, and the remaining alkali metals are mixed with the high-temperature semi-coke. The high-temperature semi-coke is fed into the semi-coke combustion zone of the boiler body 1 by the combustion-supporting gas for combustion, and the amount of oxygen in the combustion-supporting gas is lower than the amount of oxygen required for complete combustion of the high-temperature semi-coke, so that a reducing atmosphere is formed in the semi-coke combustion zone, thereby reducing the generation of nitrogen oxides.

[0035] The high-temperature synthesis gas outlet of the pyrolysis gasifier 2 is connected to the high-temperature synthesis gas inlet of the heat exchanger 3. The high-temperature crude synthesis gas generated by the pyrolysis gasifier 2 is sent to the heat exchanger 3. After heat exchange, the temperature is reduced to generate low-temperature crude synthesis gas. At the same time, the gaseous tar carried by the high-temperature crude synthesis gas is condensed into liquid, and the gaseous alkali metal carried by the high-temperature crude synthesis gas is first condensed and then solidified into solid.

[0036] An air preheater 9 is installed inside the boiler body 1. The flue gas inlet of the air preheater 9 is connected to the boiler body 1. Another part of the high-temperature flue gas inside the boiler body 1 continues to flow downstream, and the temperature continues to decrease, and then enters the air preheater 9. The oxygen inlet of the air preheater 9 is connected to the oxygen outlet of the air separation device 8. The inlet of the air separation device 8 is connected to air. After the air enters the air separation device 8, oxygen and nitrogen are separated. The nitrogen is discharged through the nitrogen outlet of the air separation device 8. After the low-temperature oxygen flows out through the oxygen outlet of the air separation device 8, it enters the air preheater 9 to exchange heat with the high-temperature flue gas from the boiler body 1. The flue gas outlet of the air preheater 9 is connected to the low-temperature flue gas outlet of the boiler body 1. The low-temperature flue gas outlet of the boiler body 1 is respectively connected to the flue gas inlet of the flue gas treatment device 10, the low-temperature flue gas inlet of the heat exchanger 3, and the low-temperature flue gas inlet opened above the burnout zone of the boiler body 1;

[0037] After the high-temperature flue gas and the low-temperature oxygen are heat-exchanged in the air preheater 9, the low-temperature flue gas generated is divided into three parts, wherein: a part of the low-temperature flue gas enters the flue gas treatment device 10 for purification, thereby removing impurities such as water and sulfur oxides, and the flue gas treatment device 10 is connected to a carbon capture device 11, and the purified low-temperature flue gas is captured by the carbon capture device 11 to achieve carbon emission reduction; a part of the low-temperature flue gas enters the burnout zone of the boiler body 1 from the low-temperature flue gas inlet opened above the burnout zone of the boiler body 1 to reduce the flue gas temperature in the boiler body 1, thereby reducing the viscosity of the fly ash particles and weakening the tendency of ash accumulation and slagging in the boiler body 1; another part of the low-temperature flue gas enters the heat exchanger 3, exchanges heat with the high-temperature crude synthesis gas from the pyrolysis gasification furnace 2 to form high-temperature flue gas;

[0038] The oxygen outlet of the air preheater 9 and the high-temperature flue gas outlet of the heat exchanger 3 are respectively connected to the semi-coke combustion zone and the burnout zone of the boiler body 1 through pipelines. The low-temperature oxygen from the air separation equipment 8 and the high-temperature flue gas from the boiler body 1 are heat-exchanged inside the air preheater 9 to form high-temperature oxygen. The high-temperature oxygen discharged from the oxygen outlet of the air preheater 9 and the high-temperature flue gas discharged from the high-temperature flue gas outlet of the heat exchanger 3 are mixed in the pipeline to form a high-temperature oxygen / flue gas mixture. A part of the high-temperature oxygen / flue gas mixture delivers the semi-coke to the semi-coke combustion zone of the boiler body 1 and serves as a combustion-supporting gas to promote the combustion of the semi-coke; the other part is passed into the burnout zone of the boiler body 1 to promote the combustion of the remaining fuel.

[0039] A part of the high-temperature flue gas generated by the boiler body 1 is transported to the pyrolysis gasification furnace 2 as a heat source and gasification agent, and the other part is heat exchanged with low-temperature oxygen through the air preheater 9, and then divided into three parts, which are respectively sent to the flue gas treatment equipment 10, the heat exchanger 3 and the burnout zone of the boiler body 1, and all are utilized without being discharged into the atmosphere, thereby achieving zero emission of carbon dioxide;

[0040] The low-temperature synthesis gas outlet of the heat exchanger 3 is connected to the inlet of the cyclone separator 4. The high-temperature crude synthesis gas from the pyrolysis gasifier 2 and the low-temperature flue gas from the air preheater 9 are heat-exchanged inside the heat exchanger 3 to generate low-temperature crude synthesis gas, which is transported to the cyclone separator 4. The liquid-solid mixture outlet of the cyclone separator 4 is connected to the inlet of the centrifugal separator 5. The gas outlet of the cyclone separator 4 is connected to the inlet of the electrostatic precipitator 6. The cyclone separator 4 separates the gas from the liquid-solid mixture in the low-temperature crude synthesis gas, wherein the liquid-solid mixture is tar and solid impurity particles rich in alkali metals. The gas separated by the cyclone separator 4 enters the electrostatic precipitator 6, and the separated liquid-solid mixture enters the centrifugal separator 5 for liquid-solid separation, thereby separating the tar and solid impurity particles rich in alkali metals carried by the low-temperature crude synthesis gas to obtain solid residue and tar respectively.

[0041] The synthesis gas outlet of the electrostatic precipitator 6 is connected to the synthesis gas storage device 7 and the synthesis gas combustion reduction zone of the boiler body 1. After the electrostatic precipitator 6 removes a small amount of impurities such as tar and alkali metals remaining in the gas, pure synthesis gas is obtained. Part of the pure synthesis gas is stored in the synthesis gas storage device 7, and the other part of the pure synthesis gas enters the synthesis gas combustion reduction zone of the boiler body 1 for combustion. The pure synthesis gas does not carry alkali metal particles, which can reduce the tendency of ash accumulation and slagging in the boiler, and the pure synthesis gas can enhance the reducing atmosphere in the synthesis gas combustion reduction zone, thereby reducing the generation of nitrogen oxides and reducing nitrogen oxide emissions.

[0042] A high-alkali coal cascade utilization method based on a high-alkali coal cascade utilization system coupled with fuel pretreatment and oxygen-enriched combustion comprises the following steps:

[0043] Step 1, feeding high-alkali coal into a pyrolysis gasification furnace 2, generating high-temperature semi-coke and high-temperature crude synthesis gas after pyrolysis and gasification reactions, wherein part of the alkali metal in the high-alkali coal is volatilized and mixed in the high-temperature crude synthesis gas, and the remaining alkali metal is mixed in the high-temperature semi-coke;

[0044] Step 2, the high-temperature semi-coke is sent into the semi-coke combustion zone of the boiler body 1 by the combustion-supporting gas for combustion, and high-temperature flue gas is generated inside the boiler body 1. The high-temperature flue gas flows downstream and the temperature gradually decreases. When the temperature of a part of the high-temperature flue gas drops to 700-900°C, it enters the pyrolysis gasifier 2 as a heat source and gasification agent, and the other part of the high-temperature flue gas continues to flow downstream and the temperature continues to decrease, and then enters the air preheater 9, exchanges heat with the low-temperature oxygen from the air separation equipment 8, forms low-temperature flue gas and flows through the flue gas outlet of the air preheater 9 and the low-temperature flue gas outlet of the boiler body 1 in turn, a part of the low-temperature flue gas enters the flue gas treatment equipment 10 for purification, and the purified flue gas is collected in the carbon capture equipment 11, a part of the low-temperature flue gas enters the heat exchanger 3, and the other part of the low-temperature flue gas is transported to the upper part of the burnout zone of the boiler body 1 to reduce the temperature of the flue gas inside the boiler body 1;

[0045] The high-temperature crude synthesis gas from the pyrolysis gasifier 2 enters the heat exchanger 3, and after heat exchange with the low-temperature flue gas from the air preheater 9, the gaseous alkali metal carried by it is first condensed and then solidified. As the low-temperature crude synthesis gas enters the cyclone separator 4, the cyclone separator 4 separates the gas from the liquid-solid mixture in the low-temperature crude synthesis gas. The separated gas enters the electrostatic precipitator 6, and after impurities are removed, pure synthesis gas is obtained. A part of the pure synthesis gas is stored in the synthesis gas storage device 7, and the other part of the pure synthesis gas is transported to the synthesis gas combustion reduction zone of the boiler body 1 to enhance the reducing atmosphere inside the boiler body 1; the separated liquid-solid mixture enters the centrifugal separator 5 for liquid-solid separation, so as to separate the tar and the solid particles rich in alkali metals carried by the low-temperature crude synthesis gas, and obtain solid residue and tar respectively;

[0046] After the low-temperature flue gas and the high-temperature crude synthesis gas are heat exchanged inside the heat exchanger 3, high-temperature flue gas is formed. After the high-temperature flue gas is mixed with the high-temperature oxygen from the air preheater 9, a high-temperature oxygen / flue gas mixture is formed. A part of the high-temperature oxygen / flue gas mixture is used as a combustion-supporting gas to send the high-temperature semi-coke into the boiler body for combustion, and the other part of the high-temperature oxygen / flue gas mixture enters the burnout zone to promote the burnout of the remaining fuel.

Claims

1. A high-alkali coal cascade utilization system coupling fuel pretreatment and oxygen-enriched combustion, characterized in that: It comprises a boiler body (1), a pyrolysis gasification furnace (2), a heat exchanger (3), a cyclone separator (4), a centrifugal separator (5), an electrostatic precipitator (6), a synthesis gas storage device (7), an air separation device (8), an air preheater (9) and a flue gas treatment device (10); The high-temperature flue gas outlet of the boiler body (1) is connected to the flue gas inlet of the pyrolysis gasifier (2), the semi-coke outlet of the pyrolysis gasifier (2) is connected to the boiler body (1), the high-temperature semi-coke generated by the reaction of high-alkali coal in the pyrolysis gasifier (2) is sent into the boiler body (1) by the combustion-supporting gas, and the amount of oxygen in the combustion-supporting gas is lower than the amount of oxygen required for the complete combustion of the high-temperature semi-coke, the high-temperature synthesis gas outlet of the pyrolysis gasifier (2) is connected to the high-temperature synthesis gas inlet of the heat exchanger (3), the low-temperature synthesis gas outlet of the heat exchanger (3) is connected to the inlet of the cyclone separator (4), the liquid-solid mixture outlet of the cyclone separator (4) is connected to the inlet of the centrifugal separator (5), the gas outlet of the cyclone separator (4) is connected to the inlet of the electrostatic precipitator (6), and the synthesis gas outlet of the electrostatic precipitator (6) is connected to the inlet of the synthesis gas storage device (7); The air preheater (9) is arranged inside the boiler body (1), and the flue gas inlet of the air preheater (9) is connected to the boiler body (1), the oxygen inlet of the air preheater (9) is connected to the oxygen outlet of the air separation device (8), the flue gas outlet of the air preheater (9) is connected to the low-temperature flue gas outlet of the boiler body (1), the low-temperature flue gas outlet of the boiler body (1) is respectively connected to the flue gas inlet of the flue gas treatment device (10) and the low-temperature flue gas inlet of the heat exchanger (3), the oxygen outlet of the air preheater (9) and the high-temperature flue gas outlet of the heat exchanger (3) are connected to the boiler body (1) through a pipeline, and the high-temperature oxygen from the air preheater (9) and the high-temperature flue gas from the heat exchanger (3) are mixed in the pipeline and then introduced into the boiler body (1) as a combustion-supporting gas.

2. The high-alkali coal cascade utilization system coupled with fuel pretreatment and oxygen-enriched combustion according to claim 1 is characterized in that: The boiler body (1) is provided with a semi-coke combustion zone, a synthesis gas combustion reduction zone and a burnout zone in sequence from bottom to top; After the high-temperature oxygen and high-temperature flue gas are mixed in the pipeline, a portion thereof enters the semi-coke combustion zone of the boiler body (1) as combustion-supporting gas, and the other portion thereof enters the burnout zone of the boiler body (1).

3. The high-alkali coal cascade utilization system coupled with fuel pretreatment and oxygen-enriched combustion according to claim 2 is characterized in that: The synthesis gas outlet of the electrostatic precipitator (6) is also connected to the synthesis gas combustion and reduction zone of the boiler body (1).

4. The high-alkali coal cascade utilization system coupled with fuel pretreatment and oxygen-enriched combustion according to claim 3 is characterized in that: A low-temperature flue gas inlet is provided above the burnout zone of the boiler body (1), and the low-temperature flue gas inlet is connected to the low-temperature flue gas outlet of the boiler body (1).

5. The high-alkali coal cascade utilization system coupled with fuel pretreatment and oxygen-enriched combustion according to claim 4 is characterized in that: The outlet of the flue gas treatment device (10) is connected to a carbon capture device (11).

6. A method for cascade utilization of high-alkali coal based on the cascade utilization system of high-alkali coal coupled with fuel pretreatment and oxygen-enriched combustion according to claim 5, characterized in that: The steps include: Step 1, feeding high-alkali coal into a pyrolysis gasification furnace (2), generating high-temperature semi-coke and high-temperature crude synthesis gas after pyrolysis and gasification reactions, wherein part of the alkali metal in the high-alkali coal is volatilized and mixed in the high-temperature crude synthesis gas, and the remaining alkali metal is mixed in the high-temperature semi-coke; Step 2, the high-temperature semi-coke is sent into the boiler body (1) by the combustion-supporting gas for combustion. The internal combustion of the boiler body (1) generates high-temperature flue gas. The high-temperature flue gas flows downstream and its temperature gradually decreases. When the temperature of a part of the high-temperature flue gas drops to 700-900° C., it enters the pyrolysis gasification furnace (2) as a heat source and a gasifying agent. The other part of the high-temperature flue gas continues to flow downstream and its temperature continues to decrease. Then, it enters the air preheater (9) and exchanges heat with the low-temperature oxygen from the air separation device (8) to form low-temperature flue gas. The low-temperature flue gas flows through the flue gas outlet of the air preheater (9) and the low-temperature flue gas outlet of the boiler body (1) in sequence. A part of the low-temperature flue gas enters the flue gas treatment device (10) for purification, and a part of the low-temperature flue gas enters the heat exchanger (3); The high-temperature crude synthesis gas enters the heat exchanger (3), and after heat exchange with the low-temperature flue gas from the air preheater (9), the gaseous alkali metal carried by the gas is first condensed and then solidified. As the low-temperature crude synthesis gas enters the cyclone separator (4), the cyclone separator (4) separates the gas and the liquid-solid mixture in the low-temperature crude synthesis gas. The separated gas enters the electrostatic precipitator (6) to remove impurities to obtain pure synthesis gas. The pure synthesis gas is stored in the synthesis gas storage device (7). The separated liquid-solid mixture enters the centrifugal separator (5) for liquid-solid separation, thereby separating the tar and the solid particles rich in alkali metals carried by the low-temperature crude synthesis gas, and obtaining solid residue and tar respectively. After the low-temperature flue gas and the high-temperature raw synthesis gas are heat exchanged inside the heat exchanger (3), high-temperature flue gas is formed. After the high-temperature flue gas is mixed with the high-temperature oxygen from the air preheater (9), a high-temperature oxygen / flue gas mixture is formed. The high-temperature oxygen / flue gas mixture is used as a combustion-supporting gas to feed the high-temperature semi-coke into the boiler body (1) for combustion.

7. The high-alkali coal cascade utilization method according to claim 6, characterized in that: Part of the low-temperature flue gas in step 2 enters the flue gas treatment device (10), part enters the heat exchanger (3), and the remaining part is transported to the top of the burnout zone of the boiler body (1) to reduce the temperature of the flue gas inside the boiler body (1).

8. The high-alkali coal cascade utilization method according to claim 6 or 7, characterized in that: Part of the pure synthesis gas in step 2 is stored in the synthesis gas storage device (7), and the other part is transported to the synthesis gas combustion and reduction zone of the boiler body (1) to enhance the reducing atmosphere inside the boiler body (1).

9. The high-alkali coal cascade utilization method according to claim 6 or 7, characterized in that: A portion of the high-temperature oxygen / flue gas mixture in step 2 is used as a combustion-supporting gas to deliver the high-temperature semi-coke into the semi-coke combustion zone of the boiler body (1), and the other portion enters the burnout zone to promote the burnout of the remaining fuel.

10. The high-alkali coal cascade utilization method according to claim 6 or 7, characterized in that: In the step 2, the flue gas purified by the flue gas treatment device (10) is collected in the carbon capture device (11).

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