CN210069868U - Grate furnace based on flue gas recirculation system - Google Patents

Grate furnace based on flue gas recirculation system Download PDF

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CN210069868U
CN210069868U CN201920289276.4U CN201920289276U CN210069868U CN 210069868 U CN210069868 U CN 210069868U CN 201920289276 U CN201920289276 U CN 201920289276U CN 210069868 U CN210069868 U CN 210069868U
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flue gas
primary air
air
grate furnace
combustion
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袁野
时正海
高洪培
孙献斌
赵鹏勃
肖平
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Huaneng Clean Energy Research Institute
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Huaneng Clean Energy Research Institute
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Abstract

The utility model discloses a grate furnace based on flue gas recirculation system belongs to msw incineration and clean burning technical field. A grate furnace based on a flue gas recirculation system is characterized in that a primary air oxygenation system is arranged on a primary air pipeline, a recirculation flue gas fan is additionally arranged at the outlet of a flue gas purification system, and part of purified flue gas is introduced into a hearth as part of secondary air. The circulating flue gas is used as part of secondary air, so that the mixing of fuel in the furnace and the primary air and the secondary air can be promoted, the combustion effect is improved, meanwhile, the classification is strengthened, the temperature of part of the flue gas is reduced, and the generation of NOx is reduced. When the combustion is insufficient, the oxygen concentration in the primary air is improved through the primary air oxygenation system to promote the fuel combustion, so that special pollutants such as CO, dioxin and the like generated due to insufficient combustion are reduced, and the quality of fly ash is improved. Can be according to the grate furnace operational aspect, nimble adjustment air distribution mode, reasonable in design, reduce pollutant discharge when abundant burning fuel, high-efficient environmental protection.

Description

Grate furnace based on flue gas recirculation system
Technical Field
The utility model belongs to the technical field of msw incineration and clean burning, concretely relates to grate furnace based on flue gas recirculation system.
Background
Along with the continuous development of social economy and the continuous improvement of the living standard of people's materials, the urban life and industrial garbage are more and more. The safe disposal of various wastes has become a prominent problem in the development of modern society. From the development process of each country, the garbage incineration technology has the characteristics of harmlessness, reduction, resource optimization and the like, the specialized and controlled garbage incineration is completely different from the outdoor disordered garbage incineration, and the garbage incineration technology has the characteristics of mature and reliable technology, huge application potential and the like.
The furnace type adopted by the existing waste incineration mainly comprises a mechanical grate furnace and a circulating fluidized bed boiler. The grate furnace has the greatest advantages of mature technology and stable and reliable operation, but can not realize in-furnace desulfurization; grate furnace combustion temperature is high, and grate discharge temperature is higher than 1000 ℃ usually, produces a large amount of NOx easily, and to the grate furnace, SNCR efficiency is lower in the stove, makes NOx discharge to reach standard through SNCR usually not enough, and the afterbody flue needs additionally to set up low temperature SCR denitrification facility. There are two main reasons for the low SNCR efficiency in furnaces, first: the urea or ammonia water spray gun is usually arranged at the middle upper part of the hearth, the temperature of the corresponding grate is high, and the denitration reaction efficiency is low; in addition, urea or ammonia water and flue gas are not fully mixed and only can be sprayed and covered by a spray gun, the flue gas mixed with the denitrifier quickly enters a tail flue through the upper part of a hearth for heat exchange, the temperature of the flue gas is reduced, the denitration reaction efficiency is reduced, and the SNCR reaction residence time is short. Compared with the circulating fluidized bed garbage furnace, the grate furnace does not have a device like a cyclone separator, so that a proper temperature range and sufficient reaction time can be provided for the SNCR denitration reaction, and therefore, the overall SNCR efficiency of the grate furnace is low.
The original generation of NOx in the waste incineration process of the grate furnace is high, the SNCR efficiency is low, the waste incineration denitration cost is increased, and if the SNCR cannot meet the standard emission of NOx, an SCR reactor needs to be additionally arranged; meanwhile, the SNCR reaction efficiency is low, and the problems of dust accumulation on the low-temperature heating surface at the tail part and the like are caused by excessive ammonia escape.
Patent document with publication number CN104141958A discloses a mechanical waste incineration grate boiler afterbody flue gas waste heat recycling system, the system includes circulating fan, circulation wind channel baffle, overgrate air circulation wind channel baffle, this utility model discloses can replace whole rubbish dry with primary air, reduce the amount of wind and primary air steam preheater high, low temperature section heating steam volume. But the temperature of the recirculated flue gas of the system is higher, and the effect of strengthening the staged combustion is limited.
Disclosure of Invention
In order to solve the defects existing in the prior art, the utility model aims to provide a clean combustion technology of grate furnace and grate furnace based on flue gas recirculation system through set up wind oxygenation system once on a flue gas pipeline to increase recirculated flue gas fan in the export of flue gas purification system, introduce furnace with the flue gas after the part purifies as partial overgrate air in. Can be according to the grate furnace operational aspect, nimble adjustment air distribution mode, reasonable in design, reduce pollutant discharge when abundant burning fuel, high-efficient environmental protection.
The utility model discloses a following technical scheme realizes:
the utility model discloses a grate furnace based on a flue gas recirculation system, which comprises an induced draft fan, a primary air oxygenation system, a secondary air fan and a recirculation flue gas fan; the primary air oxygenation system is connected with a primary air pipeline, a secondary air inlet and a recycling flue gas inlet are arranged on a hearth of the grate furnace, a secondary air fan is connected with the secondary air inlet through a secondary air pipe, an induced draft fan is arranged on a flue gas lead-out pipe between the flue gas purification system and a chimney, the recycling flue gas fan is connected with the flue gas lead-out pipe, and the recycling flue gas fan is connected with the recycling flue gas inlet through a recycling flue gas pipe.
Preferably, the secondary air inlet and the recirculated flue gas inlet are both arranged at the upper part of the throat of the furnace.
Further preferably, the direction of the overfire air inlet and the recirculated flue gas inlet is perpendicular to the direction of the flue gas.
Preferably, the recirculation flue gas pipe is provided with a valve and a circulation flue gas flowmeter.
Preferably, an oxygen regulating valve oxygen and a flow meter are arranged between the primary air oxygenation system and the primary air pipeline.
Preferably, a temperature measuring device is arranged in the hearth.
Compared with the prior art, the utility model discloses following profitable technological effect has:
the utility model discloses a grate furnace based on flue gas recirculation system is through setting up wind oxygenation system on a wind pipeline to increase recirculated flue gas fan in the export of gas cleaning system, introduce the flue gas after the part purifies in the furnace of grate furnace as partial overgrate air. The circulating flue gas is used as secondary air, so that on one hand, the mixing of fuel in the furnace and the primary air and the secondary air can be promoted to improve the combustion effect, and on the other hand, the classification can be strengthened, the temperature of part of the flue gas can be reduced, and the generation of NOx can be reduced. When the combustion is insufficient, the oxygen concentration in the primary air can be improved through the primary air oxygenation system to further promote the fuel combustion, after the oxygen is introduced, the CO discharge amount can be reduced by 20%, substances such as dioxin in flue gas and the like are reduced to 25% of the original value, substances such as dioxin in fly ash and the like are reduced by 50% of the original value, other heavy metals in the fly ash escape into the fly ash due to high-temperature melting and coking, and the quality of the fly ash is improved. Although the combustion temperature is increased and the original generation of NOx is improved after oxygen is introduced, the whole generation amount of NOx is reduced by 10 percent after the flue gas recirculation is combined to replace partial secondary air. Therefore, the air distribution mode can be flexibly adjusted according to the running condition of the grate furnace: if NOx is high and pollutants such as CO, dioxin and the like are normal, the amount of the recirculated flue gas can be increased to reduce the primary air quantity, so that the enhanced staged combustion is realized; if pollutants such as NOx, CO, dioxin and the like are high, oxygen can be introduced into the primary air to improve the combustion intensity in the furnace. After oxygen is doped into primary air and recycled flue gas is used as secondary air, the combustion temperature on the grate is increased, the whole flue gas flow is reduced, the compact design of a grate furnace system is facilitated, and the heat efficiency is improved. The secondary air fan is reserved independently, the boiler is set to be closed, the secondary air fan can suck air in the closed environment into the hearth, peculiar smell around the garbage furnace can be reduced, and the secondary air volume accounts for 20-30% of the total air volume generally.
Furthermore, the secondary air inlet and the recirculated flue gas inlet are both arranged at the upper part of the throat of the hearth, and secondary air is introduced into the upper part of the throat to improve the oxygen concentration in the middle stage of combustion and strengthen the combustion effect. Meanwhile, the recycled flue gas is introduced in the middle stage of combustion, so that a better staged combustion effect can be obtained. If secondary air or recirculated flue gas is introduced into the lower part of the throat, the combustion temperature is too high due to the addition of the secondary air, and the emission of pollutants such as NOx is increased; the introduction of recirculated flue gas can lead to unstable combustion of the waste fuel to some extent.
Furthermore, the direction of the secondary air inlet and the direction of the recirculated flue gas inlet are perpendicular to the flue gas direction, the action mechanism of the secondary air inlet and the recirculated flue gas is determined by the mixing degree of the secondary air inlet and the flue gas, and the secondary air inlet and the recirculated flue gas inlet are perpendicular to the flue gas direction, so that on one hand, the mixing can be enhanced, and on the other hand, the back flushing is prevented from influencing the upstream combustion flow field.
Furthermore, a valve is arranged on the recirculating flue gas pipe, real-time adjustment can be carried out according to the combustion condition in the furnace, and the recirculating flue gas pipe can be used as part of secondary air, so that the original generation amount of NOx can be reduced; meanwhile, a part of secondary air is reserved, so that the air quantity of primary air can be further reduced, and staged combustion is realized.
Furthermore, an oxygen regulating valve and an oxygen flowmeter are arranged between the primary air oxygenation system and the primary air pipeline, so that the flow of oxygen can be controlled in real time, and when the combustion is insufficient, proper oxygen is introduced to improve the combustion intensity and reduce pollutants such as NOx, CO, dioxin and the like; meanwhile, the phenomenon that the combustion temperature is too high due to too high oxygen concentration and NOx control is not facilitated is avoided.
Furthermore, a temperature measuring device is arranged in the hearth, so that the temperature in the furnace can be monitored in real time, whether the combustion of the fuel is sufficient or not is intuitively reflected, and the purposes of fully combusting the fuel and reducing pollutants such as NOx, CO, dioxin and the like are achieved by matching a primary air oxygenation system and a recycling flue gas system.
Drawings
FIG. 1 is a schematic view of the system configuration and process flow of the present invention;
in the figure: 1-an induced draft fan, 2-a recirculated flue gas fan, 3-a recirculated flue gas inlet, 4-a secondary air inlet, 5-a primary air pipeline, 6-a primary air oxygenation system, 7-a secondary air fan, 8-a valve, 9-a flue gas purification system and 10-a chimney.
Detailed Description
The invention will be described in further detail with reference to the following drawings and specific examples, which are intended to illustrate and not to limit the invention:
the utility model relates to a grate furnace based on a flue gas recirculation system, as shown in figure 1, which comprises a draught fan 1, a primary air oxygenation system 6, a secondary air fan 7 and a recirculation flue gas fan 2; the primary air oxygenation system 6 is connected with the primary air pipeline 5, and an oxygen regulating valve and an oxygen flow meter can be arranged between the primary air oxygenation system 6 and the primary air pipeline 5 to accurately regulate the oxygen flow. The secondary air inlet 4 and the recirculated flue gas inlet 3 are arranged on the hearth of the grate furnace, the secondary air inlet 4 and the recirculated flue gas inlet 3 are both arranged on the upper part of the throat of the hearth, and preferably, the directions of the secondary air inlet 4 and the recirculated flue gas inlet 3 are perpendicular to the direction of the flue gas, so that the directions of the secondary air and the recirculated flue gas are perpendicular to the direction of the flue gas. The secondary air fan 7 is connected with the secondary air inlet 4 through a secondary air pipe, the induced draft fan 1 is arranged on a flue gas leading-out pipe between the flue gas purification system 9 and the chimney 10, the recirculation flue gas fan 2 is connected with the flue gas leading-out pipe, the recirculation flue gas fan 2 is connected with the recirculation flue gas inlet 3 through a recirculation flue gas pipe, and a valve 8 and a circulation flue gas flowmeter can be arranged on the recirculation flue gas pipe to accurately adjust the circulation flue gas. A temperature measuring device can be arranged in the hearth to monitor the combustion condition in the furnace in real time.
The oxygen increasing system can adopt an oxygen increasing fan or can be directly connected with an oxygen pipeline for supplying oxygen.
The valve 8 can be an electric regulating valve, such as: ZAZP type electric through single seat regulating valve.
The circulating flue gas flowmeter can adopt an electromagnetic flue gas flowmeter, such as: XY-LUGB flue gas flowmeter.
The oxygen regulating valve can adopt an electric regulating valve, such as: ZAZN oxygen special-purpose electric control valve.
The temperature measuring device can adopt a thermocouple, such as: type B sheathed thermocouples.
The utility model discloses a process flow of grate furnace based on flue gas recirculation system as follows:
the flue gas generated by the incineration of the grate furnace sequentially passes through a heating surface (a primary evaporator, a high-temperature superheater, a medium-temperature superheater, a low-temperature superheater, a secondary evaporator, an economizer superheater, an economizer and the like) at the tail part in the furnace and flue gas purification equipment (a semi-dry desulfurization reaction tower, a dust remover, a low-temperature SCR system, wet desulfurization and a chimney), and is discharged into the chimney through a flue gas pipe. The valve is also arranged on the recirculation flue gas pipe to control the flow of the recirculation flue gas. Circulating flue gas is introduced into the hearth through a pipeline through a recirculating flue gas inlet, and the amount of the circulating flue gas is determined by the NOx generation amount in the furnace. The secondary air fan leads combustion air into the hearth from a secondary air inlet, the recirculating flue gas inlet and the secondary air inlet are both arranged at the upper part of the throat of the hearth, and the wind direction is vertical to the flue gas direction. If the boiler is designed to be closed, the secondary air fan can suck air in the closed environment into the hearth, so that peculiar smell around the garbage furnace can be reduced, and the secondary air volume accounts for 20-30% of the total air volume. If the combustion temperature of the hearth is low, and the emission of special pollutants such as CO and dioxin is high, oxygen can be converged into a primary air pipeline by using a primary air oxygenation system and introduced into the hearth from the lower part of the grate furnace to improve the combustion intensity of the hearth, and the concentration of the primary air oxygen can be controlled to be 25-27%. The proportion of the circulating flue gas is usually controlled to be 10-20% of the total amount of the flue gas, and the original generation of NOx can be reduced by about 20% by replacing part of secondary air with the circulating flue gas. Meanwhile, a part of secondary air is reserved, so that the air quantity of primary air can be further reduced, and staged combustion is realized. When the air volume of primary air is too low and the combustion intensity is insufficient, oxygen can be introduced into the primary air to improve the combustion effect, but the too high oxygen concentration can cause the combustion temperature to be too high, which is not beneficial to NOx control, generally, the oxygen concentration of the primary air does not exceed 30%, and the control in actual operation is more reasonable from 25% to 27%. After oxygen is introduced, the emission amount of CO can be reduced by 20%, substances such as dioxin in flue gas are reduced to 25% of the original value, substances such as dioxin in fly ash are reduced by 50% of the original value, and other heavy metals in fly ash escape into the fly ash due to high-temperature melting and coking. Although the combustion temperature is increased and the original generation of NOx is improved after oxygen is introduced, the whole generation amount of NOx is reduced by 10 percent after the flue gas recirculation is combined to replace partial secondary air.
The air distribution quantity of the primary air on the fire grate can adopt the following scheme: 15% of a drying section, 75% of a burning section and 10% of a burnout section. When the fuel is just put into a hearth, the energy generated by oxidation reaction is mainly used for evaporating water in the fuel, the proportion of primary air is about 15% in the section, then the fuel enters a full combustion stage, the air volume is about 75% in the main stage of the whole burnout process, and finally 10% of the primary air is utilized to ensure the burnout of low slag on a grate and reduce the content of combustible substances.
It should be noted that the above description is only one of the embodiments of the present invention, and all equivalent changes made by the system described in the present invention are included in the protection scope of the present invention. The technical field of the present invention can be replaced by other embodiments described in a similar manner, without departing from the structure of the present invention or exceeding the scope defined by the claims, which belong to the protection scope of the present invention.

Claims (6)

1. The grate furnace based on the flue gas recirculation system is characterized by comprising an induced draft fan (1), a primary air oxygenation system (6), a secondary air fan (7) and a recirculation flue gas fan (2); the primary air oxygenation system (6) is connected with the primary air pipeline (5), and the concentration of oxygen in the primary air is 25-27%; be equipped with overgrate air entry (4) and recirculated flue gas entry (3) on the furnace of grate furnace, overgrate air fan (7) are connected through the overgrate air pipe with overgrate air entry (4), and establish on the flue gas eduction tube between flue gas cleaning system (9) and chimney (10) draught fan (1), and recirculated flue gas fan (2) are connected with the flue gas eduction tube, and recirculated flue gas fan (2) are connected through recirculated flue gas pipe with recirculated flue gas entry (3).
2. The grate furnace based on a flue gas recirculation system according to claim 1, characterized in that the secondary air inlet (4) and the recirculated flue gas inlet (3) are both arranged at the upper part of the throat of the furnace.
3. The grate furnace based on a flue gas recirculation system according to claim 2, characterized in that the direction of the secondary air inlet (4) and the recirculated flue gas inlet (3) is perpendicular to the flue gas direction.
4. The grate furnace based on a flue gas recirculation system according to claim 1, characterized in that a valve (8) and a circulating flue gas flow meter are arranged on the recirculation flue gas pipe.
5. The grate furnace based on the flue gas recirculation system as claimed in claim 1, wherein an oxygen regulating valve and an oxygen flow meter are arranged between the primary air oxygenation system (6) and the primary air pipeline (5).
6. The grate furnace based on the flue gas recirculation system as claimed in claim 1, wherein a temperature measuring device is arranged in the hearth.
CN201920289276.4U 2019-03-07 2019-03-07 Grate furnace based on flue gas recirculation system Active CN210069868U (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112503535A (en) * 2020-10-30 2021-03-16 光大环境科技(中国)有限公司 Low NOXPollutant garbage incinerator
CN112833386A (en) * 2021-01-05 2021-05-25 神华神东煤炭集团有限责任公司 Flue gas denitrification system of chain furnace

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112503535A (en) * 2020-10-30 2021-03-16 光大环境科技(中国)有限公司 Low NOXPollutant garbage incinerator
CN112833386A (en) * 2021-01-05 2021-05-25 神华神东煤炭集团有限责任公司 Flue gas denitrification system of chain furnace
CN112833386B (en) * 2021-01-05 2023-09-22 神华神东煤炭集团有限责任公司 Flue gas denitrification system of chain furnace

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