Gas boiler oxygen-enriched combustion gas supply access and carbon dioxide capture system and enrichment method

Abstract

The invention discloses an oxygen-enriched combustion gas supply access and carbon dioxide capture system for a gas boiler. A hearth is connected with a flue gas pipeline, the flue gas pipeline is connected with an air preheater, the air preheater is connected with a gas heater, the gas heater is connected with a flue gas condenser, and the flue gas condenser is connected with a carbon dioxide separation device; the gas heater is communicated with the hearth; the flue gas condenser is communicated with the hearth; the flue gas condenser is communicated with the hearth through a circulating flue gas pipeline; the other end of the air preheater is connected with a mixing pipeline which is connected with an air feeder, and the other end of the air feeder is communicated with the air pipeline; the mixing pipeline is communicated with the oxygen pipeline. The invention also provides a carbon dioxide enrichment method of the system. According to the invention, the flue gas passes through the flue gas condenser and the carbon dioxide separation device, and the separated carbon dioxide is compressed and stored, so that the purpose of capturing the carbon dioxide is achieved. Condensate water can absorb part of NOx and CO, and the purposes of cleaning flue gas and protecting the environment are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of oxy-fuel combustion of gas boilers, and particularly to an oxy-fuel combustion gas supply access and carbon dioxide capture system for gas boilers, as well as a carbon dioxide enrichment method. Background Art

[0002] The iron and steel industry is the industry with the most resource and energy consumption among China's industrial sectors and is a key industry for energy conservation and emission reduction. The by-product gas of the iron and steel industry (including blast furnace gas, coke oven gas, etc.) accounts for 12% of the total energy consumption of iron and steel enterprises and is a secondary energy source that is very worthy of utilization. If it is directly discharged into the air, it will cause energy waste. Many large iron and steel groups have long had excess oxygen. If the excess oxygen can be reasonably utilized in gas boilers, it can not only reduce energy waste, but also improve the utilization rate of boiler fuel to a certain extent. Under the background of "dual carbon", the requirements for energy conservation and emission reduction of iron and steel enterprises are more stringent. Oxy-fuel combustion technology has the advantages of increasing combustion temperature, reducing flue gas volume, and reducing heat loss of exhaust gas, which is of great significance for energy conservation and emission reduction and for building an environment-friendly society in China.

[0003] In domestic oxy-fuel combustion, the oxy-fuel small oil gun combustion process is mostly adopted. The existing small oil gun technology is prone to problems such as barrel blockage, resulting in insufficient oil supply pressure and flow rate, affecting the atomization effect of fuel oil, and affecting the startup progress and consuming excess fuel oil. Summary of the Invention

[0004] Therefore, the technical problems to be solved by the present invention are to study the application of oxy-fuel combustion technology and develop an optimized technology for the oxy-fuel combustion gas supply system and a carbon dioxide recovery system for gas boilers according to the combustion characteristics of gas boilers. Another technical problem to be solved by the present invention is to provide a method for enriching and recovering carbon dioxide by the recovery system.

[0005] The technical solution of the present invention is an oxy-fuel combustion gas supply access and carbon dioxide capture system for a gas boiler, including the furnace of the gas boiler, the furnace is connected to a flue gas pipeline 5; the flue gas pipeline 5 is connected to an air preheater 6, and the air preheater 6 communicates with the furnace;

[0006] The air preheater 6 is connected to a gas heater 7, the gas heater 7 is connected to a flue gas condenser 9, and the flue gas condenser 9 is connected to a carbon dioxide separation device 10; the gas heater 7 communicates with the furnace; the flue gas condenser 9 communicates with the furnace; a swirl burner is provided on the inner wall of the furnace; the carbon dioxide separation device 10 is provided with a carbon dioxide pipeline 12; the flue gas condenser 9 communicates with the furnace through a circulating flue gas pipeline 4;

[0007] The other end of the air preheater 6 is connected to a mixing pipe 13, the mixing pipe 13 is connected to a blower 16, and the other end of the blower 16 communicates with an air pipeline 17; the mixing pipe communicates with an oxygen pipeline 15.

[0008] The main special feature of the present invention is that the gas first passes through a gas heater to absorb the heat of the tail gas, improving the energy utilization rate.

[0009] In the oxygen-enriched combustion gas supply access and carbon dioxide capture system of the gas boiler according to the present invention, preferably, a flue gas pipeline 5 is connected to the upper part of the furnace chamber.

[0010] In the oxygen-enriched combustion gas supply access and carbon dioxide capture system of the gas boiler according to the present invention, preferably, a regulating valve is provided on the oxygen pipeline. The regulating valve is used to adjust the oxygen flow; the air pipeline and the pure oxygen pipeline are mixed evenly in the mixing pipe and then enter the air preheater for heating, and burn with the heated gas in the furnace chamber.

[0011] In the oxygen-enriched combustion gas supply access and carbon dioxide capture system of the gas boiler according to the present invention, preferably, the gas pipeline 8 is connected to the gas heater 7.

[0012] In the oxygen-enriched combustion gas supply access and carbon dioxide capture system of the gas boiler according to the present invention, preferably, the outlet of the carbon dioxide separation device 10 is connected to a carbon dioxide pipeline 12 and is also connected to a separated flue gas pipeline 11.

[0013] In the oxygen-enriched combustion gas supply access and carbon dioxide capture system of the gas boiler according to the present invention, preferably, a plurality of air supply nozzles 2 and a plurality of swirl burner nozzles 3 are provided on the inner side surface of the furnace chamber.

[0014] Further, the air preheater 6 communicates with the air supply nozzle 2; the gas heater 7 communicates with the swirl burner nozzle 3.

[0015] Further, the swirl burner nozzle 3 is connected to the swirl burner; the swirl burner is located at the four corners of the inner wall of the furnace chamber. Even further, the swirl burner is located at the four corners of the inner wall of the furnace chamber and is arranged in a tangential circle.

[0016] The cross-section of the inner wall of the furnace chamber is square. More preferably, the swirl burners are arranged in a tangential circle at the four corners of the inner wall of the furnace chamber, which means that multiple burners are on a circle in the horizontal plane. When arranged at the four corners, the four airflows form an imaginary circle in the center of the furnace chamber. This tangential combustion method can make the airflows ejected from adjacent burners ignite each other and play a role in ignition.

[0017] The present invention also provides a method for carbon dioxide enrichment using the above-mentioned oxygen-enriched combustion gas supply access and carbon dioxide capture system of the gas boiler, including the following steps:

[0018] The air blower sends air into the mixing pipeline, and oxygen enters through the oxygen pipeline connected to the mixing pipeline. After the air and oxygen are fully mixed in the mixing pipeline, an oxygen-enriched combustion-supporting gas with an oxygen concentration of 30%-35% is obtained, enters the air preheater for preheating, and is sent into the furnace through the mixing pipeline;

[0019] The gas is introduced into the gas heater through the gas pipeline for heating, and then passes through the swirl burner nozzle through the gas pipeline and burns in the furnace; the flue gas generated by combustion exits from the furnace outlet, passes through the flue gas pipeline, and successively passes through the air preheater and the gas heater to absorb the heat of the tail flue gas. After the flue gas passes through the flue gas condenser, it enters the swirl burner in the furnace through the circulating flue gas pipeline for circulating combustion. The high-concentration carbon dioxide flue gas formed is then captured by the carbon dioxide separation device.

[0020] According to the method for carbon dioxide enrichment of the oxygen-enriched combustion gas supply access and carbon dioxide capture system of the gas boiler of the present invention, preferably, a plurality of swirl burner nozzles and air supply nozzles are arranged in the furnace, the preheated gas is connected to the swirl burner nozzle, and the oxygen-enriched combustion-supporting gas is connected to the air supply nozzle.

[0021] The beneficial effects of the present invention:

[0022] The present invention is provided with a flue gas recirculation system, and the captured CO2 concentration reaches more than 95%. Compared with the prior art: 1. No purification: The flue gas goes through compression - drying - compression, and the recovered CO2 concentration is the same as the inlet. 2. Partial condensation: The recovered CO2 concentration is about 90%.

[0023] According to the oxygen-enriched combustion gas supply access and carbon dioxide capture system of the gas boiler involved in the present invention, since oxygen and air are first mixed and then preheated, and at the same time the gas is also preheated in advance, the initial temperature of the gas is increased, the stable combustion in the boiler is ensured, the combustion efficiency is improved, and the heat loss due to incomplete chemical combustion is reduced. The swirl burner is adopted, and the nozzles spray the gas and the combustion-supporting gas into the furnace respectively. The existence of the recirculation zone in the swirl combustion causes the recirculation air flow to continuously entrain the unburned fuel and high-temperature flue gas, forming a stable high-temperature ignition source while also aggregating the fuel to generate a high-concentration combustion zone, which plays a role in stabilizing the flame and ensuring full combustion. The air preheater and the gas heater are arranged to absorb the heat of the tail flue gas, improve the energy utilization rate, reduce the ignition temperature of the gas, and shorten the burnout time. In addition, the flue gas passes through the flue gas condenser and the carbon dioxide separation device, and the separated carbon dioxide is compressed and stored to achieve the purpose of capturing carbon dioxide. The condensed water can absorb part of NOx and CO, achieving the purpose of cleaning the flue gas and protecting the environment. Description of the Drawings

[0024] Figure 1It is a schematic structural diagram of the oxygen-enriched combustion gas supply access and carbon dioxide capture system in the gas boiler of the present invention.

[0025] Figure 2 It is a cross-sectional view of the furnace.

[0026] In the figure, 1 - furnace; 2 - air supply nozzle; 3 - swirl burner nozzle; 4 - recycled flue gas pipeline; 5 - flue gas pipeline; 6 - air preheater; 7 - gas heater; 8 - gas pipeline; 9 - flue gas condenser; 10 - carbon dioxide separation device; 11 - separated flue gas pipeline; 12 - carbon dioxide pipeline; 13 - mixing pipeline; 14 - oxygen regulating valve; 15 - oxygen pipeline; 16 - air blower; 17 - air pipeline, 18 - swirl burner. Specific embodiments

[0027] As Figure 1 shown, this embodiment provides an oxygen-enriched combustion gas supply access and carbon dioxide capture system for a gas boiler, including a furnace 1, an air supply nozzle 2, a swirl burner nozzle 3, a recycled flue gas pipeline 4, a flue gas pipeline 5, an air preheater 6, a gas heater 7, a gas pipeline 8, a flue gas condenser 9, a carbon dioxide separation device 10, a separated flue gas pipeline 11, a carbon dioxide pipeline 12, a mixing pipeline 13, an oxygen regulating valve 14, an oxygen pipeline 15, an air blower 16, and an air pipeline 17.

[0028] As Figure 1 shown, the air pipeline 17 is connected to the air blower 16, and the air blower 16 sends air into the mixing pipeline 13. The pure oxygen pipeline 15 is connected to the mixing pipeline 13. Air and pure oxygen are fully mixed in the mixing pipeline 13 and then enter the air preheater 6 for preheating. After heating, they enter the air supply nozzle 2 of the furnace. The gas pipeline 8 is connected to the gas heater 7 for heating, and then is sent to the swirl burner nozzle 3 by the gas pipeline to burn in the furnace 1. The generated flue gas successively passes through the air preheater 6 and the gas heater 7 to absorb the heat of the tail flue gas, improving the energy utilization rate. Then it passes through the flue gas condenser 9. Part of the flue gas is sent into the furnace 1 through the recycled flue gas pipeline 4 for circulation. The high-concentration carbon dioxide flue gas generated after circulation is separated by the carbon dioxide separation device 10 to achieve the purpose of capturing carbon dioxide.

[0029] In a preferred embodiment, an adjusting valve 14 is provided on the pure oxygen pipeline 15 to adjust the oxygen flow rate with the adjusting valve.

[0030] An air preheater 6 is provided on the pipeline after the mixing of oxygen and air to preheat the oxygen-enriched combustion-supporting gas.

[0031] A gas heater 7 is provided to preheat the gas temperature.

[0032] The swirl burner nozzle 3 is adopted to spray the heated coal gas into the furnace 1, and the preheated oxygen-enriched combustion-supporting gas fed in is combusted in the furnace 1. In a preferred embodiment, as Figure 2 shown, the swirl burner nozzle 3 is connected to the swirl burner 18. The swirl burners are located at the four corners of the inner wall of the furnace and are arranged in a tangential circle.

[0033] In a preferred embodiment, the flue gas at the combustion outlet of the furnace passes through the flue gas pipeline 5 to the air preheater 6.

[0034] In a preferred embodiment, the flue gas after passing through the air preheater 6 and the coal gas heater 7 is further condensed by the flue gas condenser 14 and then fed into the furnace 1 through the circulating flue gas pipeline 4.

[0035] In a preferred embodiment, the mixing pipeline 4 is connected to the air supply nozzle 2, and the coal gas pipeline is connected to the swirl burner nozzle 3. The coal gas and the oxygen-enriched combustion-supporting gas are evenly fed into the furnace for full combustion.

[0036] The working process of the present invention is as follows:

[0037] The air blower feeds air into the mixing pipeline, and oxygen enters through the oxygen pipeline connected to the mixing pipeline. After the air and oxygen are fully mixed in the mixing pipeline, an oxygen-enriched combustion-supporting gas with an oxygen concentration of 30%-35% is obtained, enters the air preheater for preheating, and is fed into the furnace through the mixing pipeline;

[0038] The coal gas is introduced into the coal gas heater through the coal gas pipeline for heating, and then passes through the swirl burner nozzle through the coal gas pipeline to burn in the furnace; the flue gas generated by combustion exits from the furnace outlet, passes through the flue gas pipeline, and sequentially passes through the air preheater and the coal gas heater to absorb the heat of the tail flue gas. After the flue gas passes through the flue gas condenser, it enters the swirl burner in the furnace through the circulating flue gas pipeline for circulating combustion, and the high-concentration carbon dioxide flue gas formed is further captured by the carbon dioxide separation device to realize carbon dioxide capture.

[0039] In the present invention, oxygen and air are first mixed and then preheated. At the same time, the gas is also heated to increase the initial temperature of the gas, ensuring stable combustion in the boiler, improving the combustion efficiency, and reducing the heat loss due to incomplete chemical combustion. A swirl burner is adopted, and the nozzle sprays the gas and the combustion-supporting gas into the furnace respectively. The existence of the recirculation zone in the swirl combustion causes the recirculation airflow to continuously entrain unburned fuel and high-temperature flue gas, forming a stable high-temperature ignition source and also concentrating the fuel to generate a high-concentration combustion zone, which plays a role in stabilizing the flame and achieving full combustion. The air preheater and the gas heater are set to absorb the heat of the tail flue gas, improving the energy utilization rate, reducing the ignition temperature of the gas, and shortening the burnout time. In addition, the flue gas passes through the flue gas condenser and the carbon dioxide separation device, and the separated carbon dioxide is compressed and stored to achieve the purpose of carbon dioxide capture. The condensed water can absorb part of NOx and CO, achieving the purpose of cleaning the flue gas and protecting the environment.

[0040] The above embodiments are preferred cases of the present invention and are not used to limit the protection scope of the present invention.

Claims

1. An oxygen-enriched combustion gas supply access and carbon dioxide capture system for a gas boiler, comprising the furnace of the gas boiler, characterized in that: The furnace is connected to a flue gas pipeline (5); the flue gas pipeline (5) is connected to an air preheater (6), and the air preheater (6) communicates with the furnace; The air preheater (6) is connected to a gas heater (7), the gas heater (7) is connected to a flue gas condenser (9), and the flue gas condenser (9) is connected to a carbon dioxide separation device (10); the gas heater (7) communicates with the furnace; the flue gas condenser (9) communicates with the furnace; a swirl burner is provided on the inner wall of the furnace; the carbon dioxide separation device (10) is provided with a carbon dioxide pipeline (12); the flue gas condenser (9) communicates with the furnace through a circulating flue gas pipeline (4); The other end of the air preheater (6) is connected to a mixing pipeline (13), the mixing pipeline (13) is connected to a blower (16), and the other end of the blower (16) communicates with an air pipeline (17); the mixing pipeline communicates with an oxygen pipeline (15).

2. The oxygen-enriched combustion gas supply access and carbon dioxide capture system for a gas boiler according to claim 1, wherein: The upper part of the furnace is connected to a flue gas pipeline (5).

3. The oxygen-enriched combustion gas supply access and carbon dioxide capture system for a gas boiler according to claim 1, characterized in that: A regulating valve is provided on the oxygen pipeline.

4. The oxygen-enriched combustion gas supply access and carbon dioxide capture system for a gas boiler according to claim 1, characterized in that: A gas pipeline (8) is connected to the gas heater (7).

5. The oxygen-enriched combustion gas supply access and carbon dioxide capture system for a gas boiler according to claim 1, characterized in that: The outlet of the carbon dioxide separation device (10) is connected to a carbon dioxide pipeline (12) and is also connected to a separated flue gas pipeline (11).

6. The oxygen-enriched combustion gas supply access and carbon dioxide capture system for a gas boiler according to claim 1, characterized in that: A number of air supply nozzles (2) and a number of swirl burner nozzles (3) are provided on the inner side surface of the furnace.

7. The oxygen-enriched combustion gas supply access and carbon dioxide capture system for a gas boiler according to claim 6, characterized in that: The air preheater (6) communicates with the air supply nozzles (2); the gas heater (7) communicates with the swirl burner nozzles (3).

8. The oxygen-enriched combustion gas supply access and carbon dioxide capture system for a gas boiler according to claim 6, characterized in that: The swirl burner nozzles (3) are connected to the swirl burner; the swirl burner is located at the four corners of the inner wall of the furnace.

9. A method for carbon dioxide enrichment using the oxygen-enriched combustion gas supply access and carbon dioxide capture system described in any one of claims 1-8, characterized in that: It includes the following steps: The blower sends air into the mixing pipeline, oxygen enters through the oxygen pipeline connected to the mixing pipeline, the air and oxygen are fully mixed in the mixing pipeline to obtain an oxygen-enriched combustion-supporting gas with an oxygen concentration of 30%-35%, which enters the air preheater for preheating and is sent into the furnace through the mixing pipeline; The gas is introduced from the gas pipeline into the gas heater for heating, and then passes through the swirl burner nozzles through the gas pipeline to burn in the furnace; the flue gas generated by combustion exits from the furnace outlet, passes through the flue gas pipeline, and successively passes through the air preheater and the gas heater to absorb the heat of the tail flue gas. After the flue gas passes through the flue gas condenser, it enters the swirl burner in the furnace through the circulating flue gas pipeline for circulating combustion, and the high-concentration carbon dioxide flue gas formed then passes through the carbon dioxide separation device to achieve carbon dioxide capture.

10. A method for carbon dioxide enrichment in the oxygen-enriched combustion gas supply access and carbon dioxide capture system of a gas boiler according to claim 9, characterized in that: A number of swirl burner nozzles and air supply nozzles are arranged in the furnace, the preheated gas is connected to the swirl burner nozzles, and the oxygen-enriched combustion-supporting gas is connected to the air supply nozzles.

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