A new type of ultra-low emission coal gasification-gas boiler coupled coal utilization system

Abstract

The present invention discloses a coal utilization system coupled with an ultra-low emission coal gasification-gas boiler, wherein the coal utilization system is mainly composed of a coal powder bin, a vertical strong vortex liquid slag removal gasifier, a slag pool, a desuperheater, a bubbling fluidized bed dry desulfurization desulfurization tower, a separation ash + desulfurization product bin, a high-temperature low-oxygen coal gas burner, a MILD gas boiler with an SNCR device, a high-temperature air duct, a high-temperature flue gas duct, a bag filter, an induced draft fan, a chimney and other equipment. The system uses high-temperature molten air gasification technology for coal gasification, and the generated hot coal gas is desulfurized by a pre-arranged bubbling fluidized bed desulfurization tower, and then MILD combustion and heat release are carried out in a MILD gas boiler with an SNCR device equipped with a high-temperature low-oxygen coal gas burner. The core of the present invention is to innovatively propose a coal utilization system coupled with a new type of pre-desulfurization ultra-low emission coal gasification-gas boiler that integrates multiple ultra-low emission advantage technologies, and the system has the advantages of low cost, low water consumption, and low pollution.

Description

Technical Field

[0001] The present invention relates to the technical field of efficient and clean utilization of coal, and in particular to an ultra-low emission coal gasification-gas boiler coupled coal utilization system. Background Art

[0002] my country's natural resource structure of being poor in oil, little in gas, and rich in coal has determined my country's energy structure and the long-term important position of coal in industry and economy. However, the pollutants such as sulfur, nitrogen, and dust emitted by coal combustion, as well as greenhouse gases such as carbon dioxide, have adverse effects on the environment and climate, making the clean and efficient utilization technology of coal an urgent problem to be solved. How to give full play to the advantages, cleanly utilize my country's relatively abundant coal resources, improve my country's energy and industrial technology level, and solve the problems of air pollution and low energy efficiency has become an important development direction for the country's energy and resource utilization and energy conservation and environmental protection. Realizing the clean and efficient use of coal is of great significance to my country's energy security, industrial and agricultural production, people's lives, and air and environmental protection.

[0003] Developing a coal utilization system coupled with coal gasification and gas boilers, first gasifying coal to form clean gas, and then using the gas in gas boilers, can effectively reduce pollutant emissions and improve the thermal utilization efficiency of coal. This system can not only significantly improve the environmental performance of coal combustion, but also promote the development of equipment such as gas boilers in the direction of high efficiency, energy saving and environmental protection. In addition, the combustible coal gas produced by pretreatment can also be used for other purposes such as power generation and chemical manufacturing, further expanding the utilization of coal. Therefore, the coal utilization system coupled with coal gasification and gas boilers can promote the clean use of coal, help related energy companies to efficiently use coal resources, reduce environmental pollution, and is of great significance to energy conservation and carbon reduction and the promotion of sustainable social and economic development.

[0004] At present, there are various coal-fired boiler technologies and equipment systems, each with its own structure, technical characteristics and relative advantages, but because they can only complete the direct combustion of coal, they have problems with coal combustion efficiency, system thermal energy utilization efficiency, and pollutant emissions. These are serious problems that are prevalent and have not been solved for a long time in the current coal energy utilization. The effective solution is to cleanly and efficiently gasify coal to produce hot coal gas, and directly complete the clean combustion and heat release of hot coal gas to achieve clean and efficient energy utilization of coal. However, such coal energy utilization systems are not yet mature and have various problems, among which system efficiency and pollutant emissions are two core issues. How to effectively utilize and reasonably couple multiple technical advantages and propose an ultra-low emission coal gasification-gas boiler coupled coal utilization system has become the direction of efforts of scholars in related fields. Summary of the invention

[0005] The core purpose of the present invention is to propose an ultra-low emission coal gasification-gas boiler coupled coal utilization system, which effectively solves the problems of low coal energy utilization efficiency, high air pollution emissions and high equipment operating costs existing in existing coal-fired boiler technology, and realizes clean, efficient and low-cost utilization of coal.

[0006] The objective of the present invention is achieved through the following technical scheme: a coal utilization system coupled with ultra-low emission coal gasification and gas boiler, comprising a pulverized coal bin, a vertical strong vortex liquid slag removal gasifier, a slag pool, a desuperheater, a bubbling fluidized bed dry desulfurization desulfurization tower, an ash separation + desulfurization product bin, a high-temperature low-oxygen coal gas burner, a MILD gas boiler with an SNCR device, a high-temperature air duct, a high-temperature flue gas duct, a bag dust collector, an induced draft fan, a chimney and other equipment. The pulverized coal enters the vertical strong vortex liquid slag discharge gasifier (2) from the pulverized coal bin (1) and undergoes a molten air gasification reaction with a high-temperature air gasifier (>700°C) delivered from a MILD gas boiler (8) with an SNCR device through a high-temperature air pipeline (9). The generated liquid slag falls into the slag pool (3) from the slag outlet at the bottom of the gasifier by gravity and is discharged after being cooled. The generated high-temperature hot coal gas is first cooled to 900°C by a desuperheater (4) and then enters a bubbling fluidized bed desulfurization tower (5) whose desulfurization agent is limestone for desulfurization. The raw separation ash and desulfurization solid products fall into the separation ash + desulfurization product bin (6); the hot coal gas (>800°C) after desulfurization is transported to a MILD gas boiler (8) with an SNCR device equipped with a high-temperature low-oxygen coal gas burner (7) for MILD combustion. Part of the flue gas after combustion is returned to the high-temperature low-oxygen coal gas burner (7) through flue gas recycling, and the other part is drawn by the induced draft fan (12) through the bag filter (11) after heat exchange and SNCR denitrification, and then discharged from the chimney (13).

[0007] The above-mentioned ultra-low emission coal gasification-gas boiler coupled coal utilization system is adopted, characterized in that the operation steps and process of the coal gasification-gas boiler coupled coal utilization system are as follows:

[0008] The pulverized coal enters the furnace of the gasifier from the upper part of the vertical strong vortex liquid slag discharge gasifier through air transportation from the pulverized coal bunker. The high-temperature air gasification medium is heated to above 700°C by the air heater of the tail flue of the MILD gas boiler at the rear end of the system. The high-temperature air gasification medium is fed in stages from the side of the gasifier. The gasification air equivalence coefficient is maintained at about 0.4. The temperature in the gasifier is controlled at above 1700°C. The liquid slag produced by high temperature falls into the slag pool from the slag outlet at the bottom of the gasifier by gravity and is discharged after cooling. The high-temperature hot coal gas produced is discharged from the upper end of the gasifier.

[0009] The hot coal gas discharged from the gasifier first passes through a desuperheater (used to heat the MILD gas boiler feed water), and after the hot coal gas is cooled to 900°C, it enters a bubbling fluidized bed desulfurization tower with limestone or lime as the desulfurizer for desulfurization. The sulfides in the hot coal gas are mainly H2S, COS, CS2, RSH, RSSR and SO2, etc. The bubbling fluidized bed desulfurization tower is used for dry desulfurization. The desulfurization temperature range is 800°C~900°C. The desulfurization products are mainly CaS and CaSO4, and the desulfurization efficiency is not less than 97%. The desulfurization products and separated fly ash fall into the separation ash + desulfurization product bin for removal, and the hot coal gas after desulfurization enters the high-temperature low-oxygen coal gas burner for combustion and heat release.

[0010] The desulfurized hot gas (temperature greater than 800℃), high-temperature hot air and high-temperature circulating hot flue gas are burned in the furnace of the MILD gas boiler through the high-temperature low-oxygen gas burner. Due to the high initial temperature of the hot gas, the center temperature of the furnace flame after combustion will be higher than 1900℃, so it can burn efficiently under the condition of an excess air coefficient of 1, which not only inhibits the generation of NOx in the furnace (due to the lack of excess oxygen, it can be controlled at 100mg / m 3 At the same time, the SNCR mixed reduction reactor is designed in the horizontal flue after the furnace outlet of the MILD gas boiler, which can ensure that the nitrogen oxide content in the boiler exhaust will be less than 20mg / m 3 (Standard state, dry basis, flue gas oxygen content 6%).

[0011] The flue gas generated by the combustion of the MILD gas boiler is discharged from the chimney after being dedusted by the bag filter under the action of the induced draft fan. Since the vertical strong vortex gasification furnace with liquid slag discharge is used, more than 80~90% of the ash is discharged in the form of liquid slag, so the initial fly ash concentration in the flue gas will be greatly reduced, which greatly reduces the load of the dust removal system. Compared with the pulverized coal boiler burning the same type of coal, the amount of smoke in the exhaust gas is reduced by 70~80%.

[0012] The present invention has the following advantages:

[0013] 1. The present invention forms a coal utilization system of ultra-low emission coal gasification-gas boiler coupling by innovative system layout and advanced gasification and combustion technology. Compared with the current ultra-low emission coal-fired power plant boiler and pollutant purification system, this system has the advantages of simplicity, high efficiency, low cost, low water consumption, and dry desulfurization products. This system eliminates the SCR catalytic reactor and desulfurization tower for denitrification, greatly reduces the cost of desulfurization and denitrification, eliminates the burden of SCR catalyst treatment as hazardous waste, and does not have the problem of clogging and corrosion of GGH in the wet desulfurization system, saving a large amount of desulfurization water.

[0014] 2. The coal utilization system proposed in the present invention has a core advantage in that the system can realize pre-desulfurization of coal gas, that is, high-temperature coal gas desulfurization before the coal gas enters the gas boiler for combustion. Due to the pre-desulfurization device and the use of high-temperature dry desulfurization (desulfurization efficiency is not less than 97%), the desulfurization cost will be greatly reduced compared with the wet flue gas desulfurization system set at the rear of the boiler, and the desulfurization product is dry, which is easier to comprehensively utilize. At the same time, the pre-furnace dry desulfurization is adopted, and the flue gas discharged from this boiler is dry flue gas, and the flue gas temperature (above 120°C) is much higher than the flue gas temperature after the current wet desulfurization (below 70°C), which increases the lifting height of the flue gas and is more conducive to the diffusion of pollutants.

[0015] 3. The coal utilization system proposed in the present invention has a very low NOx content in the hot coal gas because the coal powder is in a strong reducing atmosphere (the gasification air equivalence coefficient is about 0.4) during the gasification process in the vertical strong vortex liquid slag gasifier. At the same time, when the hot coal gas passes through the high-temperature low-oxygen coal gas burner for MILD combustion in the furnace of the MILD gas boiler, due to the high initial temperature of the hot coal gas, it can burn efficiently under the condition of an excess air coefficient equal to 1 (to achieve low oxygen), which also suppresses the generation of NOx. Therefore, the NOx emission of the entire system is also at a relatively low level.

[0016] 4. The coal utilization system proposed in the present invention adopts a vertical strong vortex gasification furnace with liquid slag discharge. More than 80-90% of the ash will be discharged in the form of liquid slag. Therefore, the initial fly ash concentration in the boiler exhaust will be greatly reduced, which greatly reduces the load of the dust removal system. Compared with a pulverized coal furnace burning the same type of coal, the amount of smoke in the exhaust is reduced by 70-80%.

[0017] 5. The coal utilization system proposed in the present invention has a much lower oxygen content in the flue gas of the boiler than that of conventional boilers, because the gas-fired boiler can achieve combustion under the condition of excess air coefficient equal to 1. The SO3 generated in the furnace is very low, which can reduce the generation of sulfates, especially pyrosulfates, on the wall of the heating surface, and can greatly reduce the risk of high-temperature corrosion of the heating surface of the boiler. At the same time, the oxygen content in the flue gas of the boiler is relatively low, and the SO3 generated by the catalysis of metal oxides (such as Fe2O3, V2O5, etc.) in the ash in the later stage is very low, which will greatly reduce the acid dew point of the flue gas of the boiler and reduce the acid corrosion and ash accumulation of the low-temperature heating surface of the boiler. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the overall system diagram of the present invention.

[0019] Explanation of the accompanying symbols: 1. Pulverized coal silo, 2. Vertical strong vortex liquid slag discharge gasification furnace, 3. Slag pool, 4. Desuperheater, 5. Bubbling fluidized bed dry desulfurization and desulfurization tower, 6. Ash separation + desulfurization product silo, 7. High-temperature low-oxygen coal gas burner, 8. MILD gas boiler with SNCR device, 9. High-temperature air duct, 10. High-temperature flue gas duct, 11. Bag dust collector, 12. Draft fan, 13. Chimney. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described below in conjunction with the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the idea and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0021] like Figure 1 As shown, the ultra-low emission coal gasification-gas boiler coupled coal utilization system proposed in the present invention comprises a pulverized coal bin (1), a vertical strong vortex liquid slag removal gasifier (2), a slag pool (3), a desuperheater (4), a bubbling fluidized bed dry desulfurization desulfurization tower (5), an ash separation + desulfurization product bin (6), a high-temperature low-oxygen coal gas burner (7), a MILD gas boiler with an SNCR device (8), a high-temperature air duct (9), a high-temperature flue gas duct (10), a bag filter (11), an induced draft fan (12), and a chimney (13).

[0022] In the whole system, the pulverized coal bin (1) is connected to the vertical strong vortex liquid slag removal gasifier (2) for conveying pulverized coal as a gasification raw material to the gasifier; at the same time, the MILD gas boiler (8) with the SNCR device is connected to the vertical strong vortex liquid slag removal gasifier (2) through a high-temperature air pipeline (9) for conveying a high-temperature air gasification agent (>700°C) required for gasification. The slag pool (3) is arranged at the lower end of the vertical strong vortex liquid slag removal gasifier (2) for receiving liquid molten slag discharged by gravity from the slag outlet at the bottom of the gasifier. The rear end of the vertical strong vortex liquid slag removal gasifier (2) is connected to a desuperheater (4) for reducing the high-temperature hot coal gas generated in the vertical strong vortex liquid slag removal gasifier (2). The desuperheater (4) is connected to a bubbling fluidized bed desulfurization tower (5) for desulfurizing the hot coal gas cooled to 900°C; the lower end of the bubbling fluidized bed desulfurization tower (5) is connected to a separation ash + desulfurization product bin (6) for receiving the separation ash and desulfurization solid products generated by the desulfurization tower; at the same time, the rear end of the bubbling fluidized bed desulfurization tower (5) is connected to a high-temperature low-oxygen coal gas burner (7) installed on a MILD gas boiler (8) with an SNCR device, so as to ensure that the hot coal gas is MILD-combusted in the MILD gas boiler (8) with an SNCR device. A part of the flue gas after combustion is recycled back to the high-temperature low-oxygen coal gas burner (7) through the flue gas, and the other part is drawn by an induced draft fan (12) arranged behind the MILD gas boiler (8) with an SNCR device, passes through a bag filter (11), and is discharged from a chimney (13) after heat exchange and SNCR denitration.

[0023] The specific implementation steps of the present invention are as follows: First, coal powder is transported from the coal powder bin (1) through air into the furnace of the gasifier from the upper part of the vertical strong vortex liquid slag gasifier (2), and the high-temperature air gasification medium is heated to above 700° C. by the air heater of the tail flue of the MILD gas boiler (8) at the rear end of the system. The gasification medium is tangentially and graded from the side of the vertical strong vortex liquid slag gasifier (2), and the gasification air equivalent coefficient is maintained at about 0.4. The temperature in the vertical strong vortex liquid slag gasifier (2) is controlled at above 1700° C. The liquid slag generated at high temperature falls into the slag pool (3) from the slag outlet at the bottom of the gasifier by gravity and is discharged after cooling. The generated high-temperature hot coal gas is discharged from the upper end of the vertical strong vortex liquid slag gasifier (2). Then, the hot coal gas discharged from the vertical strong vortex liquid slag gasification furnace (2) first passes through a desuperheater (4) (used to heat the MILD gas boiler feed water), and after the hot coal gas is cooled to 900°C, it enters a bubbling fluidized bed desulfurization tower (5) whose desulfurization agent is limestone or lime for desulfurization. The sulfides in the hot coal gas are mainly H2S, COS, CS2, RSH, RSSR and SO2, etc., and a bubbling fluidized bed desulfurization tower is used for dry desulfurization. The desulfurization temperature range is 800°C to 900°C. The desulfurization products are mainly CaS and CaSO4, and the desulfurization efficiency is not less than 97%. The desulfurization products and separated fly ash fall into the separated ash + desulfurization product bin (6) for removal, and the hot coal gas after desulfurization enters the high-temperature low-oxygen coal gas burner (7) for combustion and heat release. Secondly, the hot coal gas (temperature greater than 800°C) after desulfurization, high-temperature hot air and high-temperature circulating hot flue gas are burned in the furnace of the MILD gas boiler (8) with SNCR device through the high-temperature low-oxygen coal gas burner (7). Since the initial temperature of the hot coal gas is high, the center temperature of the furnace flame after combustion will be higher than 1900°C, so it can burn efficiently under the condition of an excess air coefficient of 1, which not only suppresses the generation of NOx in the furnace (due to the absence of excess oxygen, it can be controlled at 100mg / m 3 At the same time, the SNCR mixed reduction reactor is designed in the horizontal flue after the furnace outlet of the MILD gas boiler, which can ensure that the nitrogen oxide content in the boiler exhaust will be less than 20mg / m 3 (Standard state, dry basis, flue gas oxygen content 6%). Finally, the flue gas generated by the combustion of the MILD gas boiler is dedusted by the bag filter (11) under the action of the induced draft fan (12) and then discharged from the chimney (13).

Claims

1. A method for utilizing coal by coupling ultra-low emission coal gasification and gas boiler, characterized in that: The pulverized coal enters the vertical strong vortex liquid slag discharge gasifier (2) from the pulverized coal bin (1) and undergoes a molten air gasification reaction with the high-temperature air gasifier delivered from the MILD gas boiler (8) with an SNCR device through a high-temperature air pipeline (9). The generated liquid slag falls into the slag pool (3) from the slag outlet at the bottom of the gasifier by gravity and is discharged after being cooled. The generated high-temperature hot coal gas is first cooled to 900°C by a desuperheater (4) and then enters a bubbling fluidized bed dry desulfurization desulfurization tower (5) whose desulfurization agent is limestone for desulfurization. The generated separation ash and desulfurization solid products fall into the separation ash + desulfurization product bin (6), and the hot coal gas after desulfurization is transported to the MILD gas boiler (8) with an SNCR device equipped with a high-temperature low-oxygen coal gas burner (7) for MILD combustion. Part of the flue gas after combustion is returned to the high-temperature low-oxygen coal gas burner (7) through flue gas recycling, and the other part is pulled by the induced draft fan (12) through the bag filter (11) and discharged from the chimney (13) after heat exchange and SNCR denitrification; The vertical strong vortex liquid slag removal gasifier (2) adopts high-temperature air gasification, the gasifying agent used is high-temperature hot air, the temperature of the high-temperature hot air is greater than 700° C., the gasification air equivalent coefficient is maintained at 0.4, and the temperature in the gasifier is controlled at above 1700° C.; The fuel burned by the MILD gas boiler (8) with an SNCR device is desulfurized hot coal gas, the temperature of which is greater than 800° C. The desulfurized hot coal gas, high-temperature hot air and high-temperature circulating hot flue gas are subjected to MILD combustion in the furnace of the MILD gas boiler (8) with an SNCR device through a high-temperature low-oxygen coal gas burner (7). Since the initial temperature of the hot coal gas is high, the combustion is carried out under the condition that the air excess coefficient is equal to 1.

2. An ultra-low emission coal gasification-gas boiler coupled coal utilization system, adopting the ultra-low emission coal gasification-gas boiler coupled coal utilization method as claimed in claim 1, comprising a coal powder bin (1), a vertical strong vortex liquid slag removal gasifier (2), a slag pool (3), a desuperheater (4), a bubbling fluidized bed dry desulfurization desulfurization tower (5), an ash separation + desulfurization product bin (6), a high-temperature low-oxygen coal gas burner (7), a MILD gas boiler with a SNCR device (8), a high-temperature air duct (9), a high-temperature flue gas duct (10), a bag filter (11), an induced draft fan (12), and a chimney (13).

3. The ultra-low emission coal gasification-gas boiler coupled coal utilization system according to claim 2 is characterized in that The bubbling fluidized bed dry desulfurization desulfurization tower (5) is a pre-desulfurization device and adopts high-temperature dry desulfurization.

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