A method for reducing carbon emissions by using high-concentration CO2 internal circulation sealed coal combustion

Abstract

The present invention relates to the field of boiler carbon emission reduction methods, and proposes a carbon emission reduction method that uses high-concentration CO2 internal circulation to seal coal combustion, which has a reasonable structural design and can improve the CO2 concentration to achieve one-step compression. The carbon emission reduction method is as follows: A sealing cover is provided outside the overall boiler housing, and the sealing cover is filled with high-concentration CO2; The air separation device purifies O2 and sends it into the mixed air distribution system to be mixed with CO2 to form a mixed gas; The sealing cover isolates gases other than O2 and CO2 from entering the boiler, increasing the CO2 concentration at the boiler tail.

Description

Technical Field

[0001] The present invention relates to the field of boiler carbon emission reduction methods, and in particular to a carbon emission reduction method utilizing high-concentration CO2 internal circulation sealed coal combustion. Background Art

[0002] O2 / CO2 mixed oxygen-enriched combustion technology can simultaneously reduce the emission of pollutants such as SO2, NO, and CO2. It is an environmentally friendly combustion method with low comprehensive pollutant emissions. This technology uses flue gas recirculation to replace nitrogen in the combustion air with CO2 in the flue gas, which participates in combustion together with oxygen, and can directly recover CO2. Compared with conventional air combustion, SO2 and NO emissions are low, and the smoke exhaust volume is only 1 / 4 of the traditional method, thereby greatly reducing smoke exhaust losses and significantly improving boiler thermal efficiency.

[0003] There is air leakage during the boiler combustion process. On the one hand, this is because the combustion system and smoke and air system inside the boiler are both negative pressure systems, which provide power for external air to enter the boiler; on the other hand, it is due to the design and manufacturing problems of the boiler itself, such as the thermal expansion of the boiler, which makes it difficult to completely seal some of the heating surface connections; in addition, in the general boiler manufacturing and on-site installation process, the sealing quality requirements for non-pressure parts connections are not strict. Therefore, air leakage of coal-fired boilers is an inevitable phenomenon and its existence is reasonable.

[0004] Due to the current air leakage of the boiler, the air that leaks in will participate in the reaction to generate SO2, NO, etc., reducing the concentration of CO2, making the actual concentration of CO2 collected at the tail lower than 80%, which cannot reach the purity for direct compression. The CO2 with insufficient purity needs to be purified again before it can be compressed for geological storage. Purification will greatly increase the cost and energy consumption, limiting the application of O2 / CO2 mixed oxygen-enriched combustion technology.

[0005] Therefore, how to solve the problem of low tail CO2 concentration becomes the key to whether O2 / CO2 combustion technology can be applied on a large scale. Summary of the invention

[0006] Therefore, in view of the above problems, the present invention proposes a carbon emission reduction method using sealed coal combustion with high-concentration CO2 internal circulation, which has a reasonable structural design and can increase the CO2 concentration to achieve one-step compression.

[0007] In order to solve the above technical problems, the solution adopted by the present invention is: a carbon emission reduction method using high-concentration CO2 internal circulation sealed coal combustion, the carbon emission reduction method is as follows:

[0008] S1. A sealing cover is set on the overall outer cover of the boiler, and the sealing cover is filled with high-concentration CO2;

[0009] S2, using the air separation unit to purify the O2 in the air and send it into the mixed air distribution system to mix with the high-concentration CO2 to form a mixed gas, and then the mixed gas is sent into the boiler by the mixed air distribution system;

[0010] S3, the coal supply system supplies coal to the boiler, and under the action of the sealing cover, it isolates gases other than O2 and CO2 from entering the boiler, so that the mixed gas assists the coal powder to burn fully, and increases the CO2 concentration at the tail of the boiler;

[0011] S4. The high-concentration CO2 generated by boiler combustion is collected through a CO2 collection device, and the collected high-concentration CO2 with a concentration of not less than 95% that meets the compression conditions is directly compressed to a supercritical state. 18%-42% of the high-concentration CO2 is compressed into a high-pressure viscous liquid, and 58%-82% of the high-concentration CO2 is not compressed. The high-concentration CO2 gas in a supercritical state is reused through an internal circulation system;

[0012] S5. 57.2%-81.5% of the CO2 in the 58%-82% high-concentration CO2 gas that has not been compressed into a supercritical state is sent to the mixed air distribution system through the A loop of the internal circulation system in one direction, mixed with the O2 purified by the air separation unit, and then sent to the boiler again to assist the combustion of pulverized coal;

[0013] S6. 0.5%-0.8% of the CO2 in the 58%-82% high-concentration CO2 gas that has not been compressed into a supercritical state is sent into the sealed cover in one direction through the B loop of the internal circulation system;

[0014] S7, the CO2 in the sealed cover is connected to the mixed air distribution system, and an internal circulation system C loop is used to discharge the CO2 in the sealed cover to the CO2 collection device in one direction by means of the mixed air distribution system;

[0015] S8. The supercritical CO2 obtained after compression is injected into underground rock formations for storage.

[0016] A further improvement is that an internal circulation air pump A for unidirectional transport of CO2 is provided in the A loop of the internal circulation system.

[0017] A further improvement is that an internal circulation air pump B for unidirectional transport of CO2 is provided in the B loop of the internal circulation system.

[0018] A further improvement is that an internal circulation air pump C for unidirectional transport of CO2 is provided in the C loop of the internal circulation system.

[0019] A further improvement is that the sealing cover is kept at a positive pressure.

[0020] A further improvement is that the pressure inside the sealing cover is maintained at 0.05-0.1 atmosphere.

[0021] By adopting the above technical solution, the beneficial effects of the present invention are:

[0022] 1. In the present invention, a sealing cover is provided on the outer cover of the boiler to isolate air from entering the boiler, and the sealing cover is filled with high-concentration CO2, so that the gas entering the boiler from the gap of the boiler is also CO2, further increasing the CO2 concentration generated by the combustion of the boiler. The sealing cover maintains a positive pressure state, so that the smoke in the boiler will not leak out, reducing the heat loss of the boiler. The sealing cover also has a heat preservation effect on the boiler, increasing the CO2 concentration and improving the thermal efficiency of the boiler.

[0023] 2. The loops between the mixed air distribution system, boiler, CO2 collection device and sealing cover in the present invention constitute an internal circulation system for CO2 reflux and reuse. The internal circulation system ensures that the CO2 generated by combustion is finally collected in the CO2 collection device. The CO2 collection device provides CO2 to the mixed air distribution system and the sealing cover, and at the same time further improves the CO2 concentration, so that the collected CO2 can be directly compressed without further purification, reducing energy consumption and costs in the process of carbon emission reduction, which is conducive to the promotion and application of this technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a working schematic diagram of a carbon emission reduction method using sealed coal combustion in a high-concentration CO2 internal circulation according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0026] refer to Figure 1 The embodiment of the present invention discloses a carbon emission reduction method using high-concentration CO2 internal circulation sealed coal combustion, and the carbon emission reduction method is as follows:

[0027] S1. A sealing cover is set on the overall outer cover of the boiler, and the sealing cover is filled with high-concentration CO2. The pressure inside the sealing cover is maintained at 0.05-0.1 atmospheres to prevent smoke from being discharged and polluting the environment, while further improving the thermal efficiency of the boiler;

[0028] S2, using the air separation unit to purify the O2 in the air and send it into the mixed air distribution system to mix with the high-concentration CO2 to form a mixed gas, and then the mixed gas is sent into the boiler by the mixed air distribution system;

[0029] S3, the coal supply system supplies coal to the boiler through the sealing cover, and the gas other than O2 and CO2 is isolated from entering the boiler under the action of the sealing cover, so that the mixed gas assists the coal powder to burn fully, and the CO2 concentration at the tail of the boiler is increased;

[0030] S4. The high-concentration CO2 generated by boiler combustion is collected through a CO2 collection device, and the collected high-concentration CO2 with a concentration of not less than 95% that meets the compression conditions is directly compressed to a supercritical state. 18%-42% of the high-concentration CO2 is compressed into a high-pressure viscous liquid, and 58%-82% of the high-concentration CO2 is not completely compressed. The high-concentration CO2 gas in a supercritical state is reused through an internal circulation system;

[0031] S5, 57.2%-81.5% of the CO2 in the 58%-82% high-concentration CO2 gas that has not been compressed into a supercritical state is sent to the mixing air distribution system through the A loop of the internal circulation system in a one-way manner, mixed with the O2 purified by the air separation unit, and then sent to the boiler to assist the combustion of coal powder. The A loop of the internal circulation system is provided with an internal circulation air pump A for one-way delivery of CO2;

[0032] S6. 0.5%-0.8% of the CO2 in the 58%-82% high-concentration CO2 gas that has not been compressed into a supercritical state is unidirectionally delivered into the sealed cover through the B loop of the internal circulation system, and the B loop of the internal circulation system is provided with an internal circulation air pump B for unidirectional delivery of CO2;

[0033] S7. The CO2 in the sealing cover is connected to the mixing and air distribution system via an internal circulation system C loop for unidirectionally discharging the CO2 in the sealing cover to the CO2 collecting device via the mixing and air distribution system. The C loop of the internal circulation system is provided with an internal circulation air pump C for unidirectionally transporting CO2.

[0034] S8. The supercritical CO2 obtained after compression is injected into underground rock formations for storage.

[0035] The interconnecting loops among the mixed air distribution system, boiler, CO2 collection device and sealing cover constitute an internal circulation system for CO2 reflux and reuse. The CO2 generated by combustion is collected in the CO2 collection device, and then returns to the mixed air distribution system through the A loop between the CO2 collection device and the mixed air distribution system to be mixed with high-purity O2 to fully assist the combustion of coal while increasing the concentration of CO2 generated by combustion. The generated CO2 is collected again in the CO2 collection device. Part of the CO2 that enters the sealing cover through the B loop between the CO2 collection device and the sealing cover enters the boiler during the combustion process, and the remaining CO2 can flow to the mixed air distribution system through the C loop between the sealing cover and the mixed air distribution system, and finally returns to the CO2 collection device, thereby preventing CO2 from entering the air and alleviating the greenhouse effect.

[0036] The basic principles, main features and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which shall fall within the scope of the present invention to be protected. The scope of protection of the present invention shall be defined by the attached claims and their equivalents.

Claims

1. A method for reducing carbon emissions by using high-concentration CO2 internal circulation sealed coal combustion, characterized in that: Carbon reduction methods are as follows: S1. A sealing cover is set on the overall outer cover of the boiler, and the sealing cover is filled with high-concentration CO2; S2, using the air separation unit to purify the O2 in the air and send it into the mixed air distribution system to mix with the high-concentration CO2 to form a mixed gas, and then the mixed gas is sent into the boiler by the mixed air distribution system; S3, the coal supply system supplies coal to the boiler, and under the action of the sealing cover, it isolates gases other than O2 and CO2 from entering the boiler, so that the mixed gas assists the coal powder to burn fully, and increases the CO2 concentration at the tail of the boiler; S4. The high-concentration CO2 generated by boiler combustion is collected through a CO2 collection device, and the collected high-concentration CO2 with a concentration of not less than 95% that meets the compression conditions is directly compressed to a supercritical state. 18%-42% of the high-concentration CO2 is compressed into a high-pressure viscous liquid, and 58%-82% of the high-concentration CO2 is not compressed. The high-concentration CO2 gas in a supercritical state is reused through an internal circulation system; S5. 57.2%-81.5% of the CO2 in the 58%-82% high-concentration CO2 gas that has not been compressed into a supercritical state is sent to the mixed air distribution system through the A loop of the internal circulation system in one direction, mixed with the O2 purified by the air separation unit, and then sent to the boiler again to assist the combustion of pulverized coal; S6. 0.5%-0.8% of the CO2 in the 58%-82% high-concentration CO2 gas that has not been compressed into a supercritical state is sent into the sealed cover in one direction through the B loop of the internal circulation system; S7, the CO2 in the sealed cover is connected to the mixed air distribution system, and an internal circulation system C loop is used to discharge the CO2 in the sealed cover to the CO2 collection device in one direction by means of the mixed air distribution system; S8. The supercritical CO2 obtained after compression is injected into underground rock formations for storage.

2. A method for reducing carbon emissions by using sealed coal combustion with high concentration CO2 internal circulation according to claim 1, characterized in that: An internal circulation air pump A for unidirectionally transporting CO2 is provided in the A loop of the internal circulation system.

3. A method for reducing carbon emissions by using sealed coal combustion with high concentration CO2 internal circulation according to claim 1, characterized in that: An internal circulation air pump B for unidirectionally transporting CO2 is provided in the B loop of the internal circulation system.

4. The carbon emission reduction method of claim 1 using sealed coal combustion with high concentration CO2 internal circulation, characterized in that: An internal circulation air pump C for unidirectional transport of CO2 is provided in the C loop of the internal circulation system.

5. The carbon emission reduction method of claim 1 using sealed coal combustion with high concentration CO2 internal circulation, characterized in that: The sealing cover is maintained at a positive pressure.

6. A method for reducing carbon emissions by using sealed coal combustion with high concentration CO2 internal circulation according to claim 5, characterized in that: The pressure inside the sealed cover is maintained at 0.05-0.1 atmosphere.

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