Novel coal utilization system of ultralow emission coal gasification-gas boiler couplingTechnical Field
The invention relates to the technical field of efficient clean utilization of coal, in particular to an ultralow-emission coal gasification-gas boiler coupled coal utilization system.
Background
The natural resource structure of lean oil, less gas and rich coal in China determines the important status of energy structure and coal in industry and economy for a long time in China. However, pollutants such as sulfur, nitrogen, dust and the like discharged by coal combustion and adverse effects of room gases such as carbon dioxide and the like on the environment and the climate make clean and efficient utilization technology of coal a problem to be solved. How to exert the advantages, clean and utilize relatively abundant coal resources in China, promote the energy and industrial technical level in China, solve the problems of air pollution and low energy efficiency, and become an important development direction of national energy and resource utilization, energy conservation and environmental protection. Realizes the clean and efficient utilization of coal and has great significance for the energy safety of China, the industrial and agricultural production, the mass life and the atmosphere and environmental protection.
The coal utilization system of coal gasification-gas boiler coupling is developed, coal is gasified to form clean gas, and then the gas is used for the gas boiler, so that pollutant emission can be effectively reduced, and meanwhile, the heat utilization efficiency of the coal can be improved. The system not only can obviously improve the environmental performance of coal combustion, but also can promote the development of equipment such as a gas boiler and the like to the directions of high efficiency, energy conservation and environmental protection. In addition, the combustible gas generated by pretreatment can be used for other purposes such as power production, chemical manufacturing and the like, and the utilization way of coal is further enlarged. Therefore, the coal utilization system of coal gasification-gas boiler coupling can promote coal cleanness, power-assisted related energy enterprises efficiently utilize coal resources, reduce environmental pollution, and have important significance for saving energy, reducing carbon and promoting sustainable development of society and economy.
At present, various coal-fired boiler technologies and equipment systems exist, and although the technologies and the equipment systems have the structural characteristics and the relative advantages, the problems of coal combustion efficiency, system heat energy utilization efficiency, pollutant emission and the like exist only because the direct combustion of coal can be completed. These are serious problems which are ubiquitous and can not be solved for a long time in the current coal energy utilization, the effective solution is to clean and efficiently gasify coal to generate hot coal gas, clean combustion and heat energy release of the hot coal gas are directly completed, and clean and high-efficiency energy utilization of coal is realized. How to effectively and reasonably couple various technical advantages and provide an ultralow-emission coal gasification-gas boiler coupled coal utilization system which is the direction of students in the related field.
Disclosure of Invention
The invention aims at providing an ultralow-emission coal gasification-gas boiler coupled coal utilization system, which effectively solves the problems of low utilization efficiency of coal energy, high atmospheric pollution emission, high equipment operation cost and the like in the existing coal-fired boiler technology, and realizes clean, efficient and low-cost utilization of coal.
The invention aims at realizing the technical scheme that the coal utilization system of the ultralow-emission coal gasification-gas boiler coupling comprises equipment such as a coal powder bin, a vertical strong vortex liquid slag discharging gasifier, a slag pool, a desuperheater, a bubbling fluidized bed dry desulfurization tower, a separated ash and desulfurization product bin, a high-temperature low-oxygen gas burner, a MILD gas boiler with an SNCR device, a high-temperature air pipeline, a high-temperature flue gas pipeline, a bag-type dust remover, an induced draft fan, a chimney and the like. Coal dust enters a vertical strong vortex liquid slag-off gasifier (2) from a coal dust bin (1) and is subjected to a molten air gasification reaction with a high-temperature air gasifying agent (> 700 ℃) conveyed by a MILD gas boiler (8) with an SNCR device through a high-temperature air pipeline (9), the generated liquid slag falls into a slag pool (3) from a slag hole at the bottom of the gasifier by gravity, is cooled and then discharged, the generated high-temperature hot gas is cooled to 900 ℃ through a desuperheater (4) and then enters a bubbling fluidized bed desulfurization tower (5) with a desulfurizing agent of limestone for desulfurization, the generated separated ash and a desulfurization solid product fall into a separated ash and desulfurization product bin (6), the desulfurized hot gas (> 800 ℃) is conveyed to the MILD gas boiler (8) with the SNCR device, which is provided with the high-temperature low-oxygen gas combustor (7) for MILD combustion, part of the combusted flue gas is recycled to the high-temperature low-oxygen gas combustor (7) through the flue gas, and the other part of the flue gas is discharged after heat exchange and SNCR denitration, and the flue gas is pulled by a draught fan (12) to a bag dust collector (11) and is discharged from a chimney (13).
The coal utilization system adopting the ultralow-emission coal gasification-gas boiler coupling is characterized by comprising the following operation steps and technical processes:
The coal powder enters a hearth of the gasifier from the upper part of the vertical strong vortex liquid slag-discharging gasifier through air conveying by a coal powder bin, high-temperature air gasification medium heated to more than 700 ℃ by an air heater of a tail flue of an MILD gas boiler at the rear end of the system is tangentially and graded from the side surface of the gasifier, the equivalent coefficient of gasification air is maintained at about 0.4, the temperature in the gasifier is controlled to be more than 1700 ℃, liquid slag generated at high temperature falls into a slag pool from a slag hole at the bottom of the gasifier by gravity, and is discharged after being cooled, and high-temperature hot gas generated is discharged from the upper end of the gasifier.
Hot gas discharged from the gasifier is firstly passed through a desuperheater (for heating the feed water of a MILD gas boiler), cooled to 900 ℃, and then enters a bubbling fluidized bed desulfurizing tower with a desulfurizing agent of limestone or lime for desulfurization. The sulfides in the hot gas are mainly H2S、COS、CS2, RSH, RSSR, SO2 and the like, the dry desulfurization is carried out by adopting a bubbling fluidized bed desulfurization tower, the desulfurization temperature ranges from 800 ℃ to 900 ℃, the desulfurization products are mainly CaS and CaSO4, and the desulfurization efficiency is not lower than 97%. The desulfurization products and the separated fly ash fall into a separated ash and desulfurization product bin for removal, and the desulfurized hot gas enters a high-temperature low-oxygen gas burner for combustion and heat release.
The hot gas after desulfurization (the temperature is more than 800 ℃) and high-temperature hot air and high-temperature circulating hot flue gas are subjected to MILD combustion in a MILD gas boiler hearth through a high-temperature low-oxygen gas burner, and the flame center temperature of the hearth after combustion is higher than 1900 ℃ due to the high initial temperature of the hot gas, so that the hot gas can be efficiently combusted under the working condition that the air excess coefficient is equal to 1, the generation of NOx in the furnace is restrained (the air excess coefficient of discharged smoke can be controlled below 100mg/m3 due to no excess oxygen), and the thermal efficiency of the boiler is increased. Meanwhile, an SNCR mixed reduction reactor is designed in a horizontal flue after the hearth outlet of the MILD gas boiler, so that the content of nitrogen oxides in the boiler exhaust smoke is ensured to be lower than 20mg/m3 (standard state, dry basis and 6% of oxygen content in the smoke).
Flue gas generated by combustion of the MILD gas boiler is removed from a chimney after dust removal by a bag-type dust remover under the action of an induced draft fan. Since the liquid slag discharging vertical strong vortex gasifier adopted in the prior art discharges over 80-90% of ash in a liquid slag mode, the initial fly ash concentration in the flue gas is greatly reduced, the load of a dust removing system is greatly reduced, and compared with a pulverized coal furnace burning the same coal type, the smoke quantity in the flue gas is reduced by 70-80%.
The invention has the following advantages:
1. The invention forms a coal utilization system of ultra-low emission coal gasification-gas boiler coupling through creative system layout and advanced gasification and combustion technology organic integration, and compared with the existing ultra-low emission coal-fired power plant boiler and pollutant purification system, the system has the advantages of simplicity, high efficiency, low cost, low water consumption, dry desulfurization products and the like. The system omits the SCR catalytic reactor and the desulfurizing tower for denitration, greatly reduces the desulfurizing and denitrating cost, eliminates the treatment burden of the SCR catalyst as dangerous waste, also does not have the problems of blocking and corroding GGH of a wet desulfurization system, and saves a large amount of desulfurizing water.
2. The coal utilization system has the core advantages that the system can realize front-mounted desulfurization of coal gas, namely high-temperature coal gas desulfurization is carried out before the coal gas enters a gas boiler for combustion, and the front-mounted desulfurization device adopts high-temperature dry desulfurization (the desulfurization efficiency is not lower than 97 percent), so that the desulfurization cost is greatly reduced compared with a wet flue gas desulfurization system arranged at the rear part of the boiler, and the desulfurization product is in a dry state, so that the system is easier to comprehensively utilize. Meanwhile, the flue gas exhausted by the boiler is dry flue gas by adopting the dry desulfurization in front of the boiler, the flue gas temperature (more than 120 ℃) is far higher than that of the flue gas subjected to the wet desulfurization at present (lower than 70 ℃), the lifting height of the flue gas is increased, and the diffusion of pollutants is facilitated.
3. The coal utilization system provided by the invention has the advantages that the coal dust is in a strong reducing atmosphere (the equivalent coefficient of gasification air is about 0.4) in the gasification process of the vertical strong vortex liquid slag-off gasifier, the content of NOx in hot coal gas is extremely low, and meanwhile, when the hot coal gas is subjected to MILD combustion in a MILD gas boiler hearth through a high-temperature low-oxygen gas burner, the initial temperature of the hot coal gas is high, the hot coal gas can be efficiently combusted under the working condition that the air excess coefficient is equal to 1 (low oxygen is realized), and the generation of NOx is also inhibited, so that the NOx emission of the whole system is also at a lower level.
4. According to the coal utilization system provided by the invention, as the liquid slag is discharged from the liquid slag-discharging vertical strong vortex gasifier, more than 80-90% of ash is discharged from the liquid slag, the initial fly ash concentration in the boiler smoke is greatly reduced, the load of a dust removal system is greatly reduced, and the smoke quantity in the smoke is reduced by 70-80% compared with a pulverized coal furnace burning the same coal type.
5. According to the coal utilization system provided by the invention, the gas-fired boiler can realize combustion under the condition that the air excess coefficient is equal to 1, the oxygen content in the boiler flue gas is far lower than that of a conventional boiler, SO3 generated in the boiler is very low, the generation of sulfate, particularly pyrosulfate, on the wall surface of a heated surface can be reduced, and the risk of high-temperature corrosion of the heated surface of the boiler can be greatly reduced. Meanwhile, the oxygen content in the boiler flue gas is low, and SO3 generated by the catalysis of metal oxides (such as Fe2O3、 V2O5 and the like) in ash is low in the later period, SO that the acid dew point of the boiler flue gas can be greatly reduced, and the acid corrosion and ash deposition of a low-temperature heating surface of the boiler are reduced.
Drawings
Fig. 1 is an overall system diagram of the present invention.
The reference numerals indicate that 1, a coal dust bin, 2, a vertical strong vortex liquid slag-off gasifier, 3, a slag pool, 4, a desuperheater, 5, a bubbling fluidized bed dry desulfurization tower, 6, a separated ash and desulfurization product bin, 7, a high-temperature low-oxygen gas burner, 8, a MILD gas boiler with an SNCR device, 9, a high-temperature air pipeline, 10, a high-temperature flue gas pipeline, 11, a bag-type dust remover, 12, an induced draft fan, 13 and a chimney.
Detailed Description
The following description of the present invention is provided with reference to the accompanying drawings, but is not limited to the following description, and any modifications or equivalent substitutions of the present invention without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention.
As shown in fig. 1, the coal utilization system with the coupling of the ultralow emission coal gasification-gas boiler provided by the invention comprises a coal powder bin (1), a vertical strong vortex slag tapping gasifier (2), a slag pool (3), a desuperheater (4), a bubbling fluidized bed dry desulfurization tower (5), a separated ash and desulfurization product bin (6), a high-temperature low-oxygen gas burner (7), a MILD gas boiler (8) with an SNCR device, a high-temperature air pipeline (9), a high-temperature flue gas pipeline (10), a bag-type dust remover (11), an induced draft fan (12) and a chimney (13).
In the whole system, a coal powder bin (1) is connected with a vertical strong vortex liquid slag-off gasifier (2) and is used for conveying gasified raw coal powder into the gasifier, and meanwhile, an MILD gas boiler (8) with an SNCR device is connected with the vertical strong vortex liquid slag-off gasifier (2) through a high-temperature air pipeline (9) and is used for conveying high-temperature air gasifying agent (> 700 ℃) required by gasification. The slag pool (3) is arranged at the lower end of the vertical strong vortex liquid slag discharging gasification furnace (2) and is used for receiving liquid slag discharged by a slag hole at the bottom of the gasification furnace by gravity. The rear end of the vertical strong vortex slag tapping gasifier (2) is connected with a desuperheater (4) and is used for reducing high-temperature hot gas generated in the vertical strong vortex slag tapping gasifier (2). The rear end of the bubbling fluidized bed desulfurization tower (5) is connected with a high-temperature low-oxygen gas burner (7) arranged on a MILD gas boiler (8) with an SNCR device and used for ensuring that the hot gas is burned in the MILD gas boiler (8) with the SNCR device. Part of the burnt flue gas is recycled to the high-temperature low-oxygen gas burner (7) through the flue gas, and the other part is discharged from the chimney (13) after being subjected to heat exchange and SNCR denitration by a draught fan (12) arranged behind the MILD gas boiler (8) with the SNCR device, and the draught fan is pulled by a bag-type dust collector (11).
The method comprises the following specific implementation operation steps that firstly, coal dust enters a gasification furnace hearth from the upper part of a vertical strong vortex liquid slag-discharging gasification furnace (2) through air conveying by a coal dust bin (1), a high-temperature air gasification medium heated to more than 700 ℃ by an air heater of a tail flue of a MILD gas boiler (8) at the rear end of a system is tangentially and graded and fed from the side surface of the vertical strong vortex liquid slag-discharging gasification furnace (2), the equivalent coefficient of gasification air is maintained to be about 0.4, the temperature in the vertical strong vortex liquid slag-discharging gasification furnace (2) is controlled to be more than 1700 ℃, liquid slag generated at high temperature falls into a slag pool (3) from a slag hole at the bottom of the gasification furnace by gravity, is cooled and is discharged, and the generated high-temperature hot gas is discharged from the upper end of the vertical strong vortex liquid slag-discharging gasification furnace (2). Then, hot gas discharged from the vertical strong vortex liquid slag-off gasifier (2) firstly passes through a desuperheater (4) (for heating the feed water of the MILD gas boiler), is cooled to 900 ℃, and then enters a bubbling fluidized bed desulfurization tower (5) with a desulfurizing agent of limestone or lime for desulfurization. the sulfides in the hot gas are mainly H2S、COS、CS2, RSH, RSSR, SO2 and the like, the dry desulfurization is carried out by adopting a bubbling fluidized bed desulfurization tower, the desulfurization temperature ranges from 800 ℃ to 900 ℃, the desulfurization products are mainly CaS and CaSO4, and the desulfurization efficiency is not lower than 97%. The desulfurization products and the separated fly ash fall into a separated ash and desulfurization product bin (6) for removal, and the hot gas after desulfurization enters a high-temperature low-oxygen gas burner (7) for combustion and heat release. Secondly, hot gas (the temperature is more than 800 ℃) after desulfurization, high-temperature hot air and high-temperature circulating hot flue gas are combusted in a hearth of an MILD gas boiler (8) with an SNCR device through a high-temperature low-oxygen gas burner (7), and the initial temperature of the hot gas is high, so that the flame center temperature of the hearth after combustion is higher than 1900 ℃, the combustion can be efficiently carried out under the working condition that the air excess coefficient is equal to 1, the generation of NOx in the furnace is restrained (the air excess coefficient of smoke is reduced and can be controlled to be less than 100mg/m3 because no excess oxygen exists), and the thermal efficiency of the boiler is increased. Meanwhile, an SNCR mixed reduction reactor is designed in a horizontal flue after the hearth outlet of the MILD gas boiler, so that the content of nitrogen oxides in the boiler exhaust smoke is ensured to be lower than 20mg/m3 (standard state, dry basis and 6% of oxygen content in the smoke). Finally, the flue gas generated by combustion of the MILD gas boiler is discharged from a chimney (13) after being dedusted by a bag-type dust remover (11) under the action of an induced draft fan (12).