CN110715289B - Layer combustion microfluidization boiler structure and combustion method - Google Patents
Layer combustion microfluidization boiler structure and combustion method Download PDFInfo
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- CN110715289B CN110715289B CN201911040354.8A CN201911040354A CN110715289B CN 110715289 B CN110715289 B CN 110715289B CN 201911040354 A CN201911040354 A CN 201911040354A CN 110715289 B CN110715289 B CN 110715289B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/18—Details; Accessories
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/18—Details; Accessories
- F23C10/20—Inlets for fluidisation air, e.g. grids; Bottoms
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Abstract
The invention relates to the technical field of boiler equipment, and discloses a layered combustion micro-fluidized boiler structure and a combustion method, wherein the layered combustion micro-fluidized boiler structure comprises a main hearth and a tail flue which are vertically installed, a plurality of independent air chambers are arranged at the bottom of the main hearth side by side, and an air preheater on the tail flue is connected with a plurality of air chambers close to the front at the bottom of the main hearth and used for intensively feeding primary air into the main hearth through the air chambers; the side wall of the main hearth is provided with a first nozzle, and the first nozzle is used for spraying calcium oxide powder or calcium carbonate powder into the main hearth. The invention provides a layer combustion microfluidization boiler structure and a combustion method, which can intensively feed primary air into a main combustion zone to reduce an air supply interval and increase the local air supply quantity of the main combustion zone, so that fuel on a grate, such as a coal bed, is changed into a low-suspension microfluidization state from a traditional moving state, and further a partial suspension combustion mode is added on the basis of traditional layer combustion, thereby improving the combustion speed, reducing the bed depth, shortening the combustion stroke and improving the combustion efficiency.
Description
Technical Field
The invention relates to the technical field of boiler equipment, in particular to a layered combustion microfluidization boiler structure and a combustion method.
Background
China is a developing country taking coal as a main energy source, and the coal resource accounts for about 75% of the total energy production and consumption of China. During the combustion of coal, a large amount of pollutants, among which Nitrogen Oxides (NO), are producedX) The method has great harm to the environment, and the nitrogen oxide can form photochemical smog to harm human health besides forming acid rain to destroy the ecological environment. High temperature combustion of coal is NOXOne of the main sources of the coal-fired boiler, and the boiler in China mainly uses the coal as the main source, thereby reducing the NO of the coal-fired boilerXThe discharge of (b) has important significance.
At present, various technologies and devices have been developed at home and abroad to be applied to desulfurization and denitration of boilers. The denitration technology comprises a low-nitrogen combustion technology, a flue gas denitration (SNCR) technology and the like. The reaction temperature is not controlled in place, and the reaction time is short, so that the reaction amount of nitrogen and carbon particles in the flue gas is small, and the self-separation of nitrogen oxides is not in time, so that the content of nitrogen oxides in the flue gas discharged from the tail part of the boiler is high. Various methods for desulfurizing boilers also have disadvantages.
The traditional grate-firing boiler is generally divided according to warm combustion, main combustion and burning-out when adopting a grate-firing mode, corresponding air quantity required by combustion is sent into corresponding air chambers so as to realize stable combustion, the traditional combustion air supply technology can lead to long burning-out stroke, and fuel is stacked on a grate to have the problem of influence on combustion efficiency due to insufficient combustion.
Disclosure of Invention
Technical problem to be solved
The invention aims to provide a layer combustion micro-fluidization boiler structure and a combustion method, which are used for solving or partially solving the problems that the conventional layer combustion boiler has long combustion stroke due to the fact that corresponding air quantity required by combustion is fed into corresponding different air chambers, and the combustion efficiency is influenced due to insufficient combustion when fuel is stacked on a grate.
(II) technical scheme
In order to solve the technical problems, the invention provides a layer-combustion microfluidization boiler structure, which comprises a main hearth and a tail flue, wherein the main hearth and the tail flue are vertically installed; and a first nozzle is arranged on the side wall of the main hearth and used for spraying calcium oxide powder or calcium carbonate powder into the main hearth.
On the basis of the scheme, the device also comprises a flue gas recirculation pipeline; the flue gas recirculation pipeline is communicated with at least one air chamber close to the rear of the bottom of the main hearth and the tail end of the tail flue and used for introducing the flue gas at the tail end of the tail flue into the rear of the bottom of the main hearth.
On the basis of the scheme, a secondary air inlet is arranged on the side wall of the top of the main hearth from top to bottom and is connected with external cold air.
On the basis of the scheme, the first nozzle is connected with external hot air or connected with a tail flue through a flue gas pipeline, and a pneumatic conveying device and a water removal device are connected on the flue gas pipeline in series.
On the basis of the scheme, a second nozzle is arranged on the side wall above the main hearth and used for spraying ammonia water or urea into the hearth; the first nozzle is located below the second nozzle.
On the basis of the scheme, the rear part of the main hearth is sequentially provided with the auxiliary hearth and the convection channel side by side, the top end of the main hearth is communicated with the top end of the auxiliary hearth, the bottom end of the auxiliary hearth is communicated with the bottom end of the convection channel, and the top end of the convection channel is communicated with the tail flue.
On the basis of the scheme, the fire grate is arranged at the bottom of the main hearth, the bottom of the main hearth covers the fire grate, the cross-sectional areas of the middle part and the top of the main hearth are smaller than that of the bottom of the main hearth, the auxiliary hearth is bent, and a switching part is arranged between the bottom end of the auxiliary hearth and the bottom end of the convection channel.
In a second aspect of the present invention, there is provided a stratified charge microfluidization combustion method based on the above-described stratified charge microfluidization boiler structure, including: the primary air is intensively fed into the main hearth through the air chamber close to the front side at the bottom of the main hearth, so that the fuel at the front side of the grate is combusted in a suspended state.
On the basis of the scheme, the method further comprises the following steps: extracting the recirculated flue gas from the tail end of the tail flue, and sending the recirculated flue gas to the rear part of the bottom of the main hearth; secondary air is supplemented into the main hearth through a secondary air inlet.
On the basis of the scheme, the proportion of primary air in the total air supply is 75-85%; the proportion of the secondary air in the total air supply amount is 15-25%; the temperature of the recirculated flue gas is less than or equal to 150 ℃; the proportion of the recycled flue gas in the total flue gas is 15-25%; the primary fan pressure head is 30-50% higher than that of the traditional grate-firing boiler.
(III) advantageous effects
The invention provides a layer combustion microfluidization boiler structure and combustion method, send the primary air to the main combustion area and can reduce the air supply interval in a centralized way, increase the local air supply volume of the main combustion area, make the fuel on the fire grate such as coal bed change from traditional moving state into the low suspension microfluidization state, and then increased the combustion way of partial suspension on the basis of traditional layer combustion, has raised the combustion speed, reduced the bed depth, reduce and burn out the journey, raise the combustion efficiency; calcium oxide powder or calcium carbonate powder is sprayed into a proper area of a hearth, the calcium oxide powder or the calcium carbonate powder can react with acidic substances in smoke, and the calcium oxide powder or the calcium carbonate powder can be neutralized by acid and alkali and oxidized and reduced to realize in-furnace desulfurization.
Drawings
FIG. 1 is a schematic view of a structure of a stratified combustion microfluidization boiler according to an embodiment of the present invention;
FIG. 2 is a schematic view of a chain microfluidization boiler according to an embodiment of the present invention;
FIG. 3 is a schematic overall view of a structure of a stratified combustion microfluidization boiler according to an embodiment of the present invention;
FIG. 4 is a schematic view of a chain microfluidization boiler according to an embodiment of the present invention.
Description of reference numerals:
| 1-a drum; | 2-main furnace chamber; | 3, a grate; |
| 4, an auxiliary hearth; | 5-secondary air inlet; | 6-tail flue; |
| 7, primary air; | 8-RecirculationCirculating flue gas; | 9-a second nozzle; |
| 10-convection channel; | 11-a transfer part; | 12 — a first nozzle; |
| 13-a dust removal device in the furnace; | 14-convection heating surface; | 15-a coal economizer; |
| 16-an air preheater; | 17-a desulfurization unit. |
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
The embodiment of the invention provides a layer combustion micro-fluidized boiler structure, referring to fig. 1, the boiler structure comprises a main hearth 2 and a tail flue 6 which are vertically installed, the bottom of the main hearth 2 is provided with a plurality of mutually independent air chambers side by side, an air preheater 16 on the tail flue 6 is connected with a plurality of air chambers near the front of the bottom of the main hearth 2 and is used for intensively feeding primary air 7 into the main hearth 2 through the air chambers; the side wall of the main hearth 2 is provided with a first nozzle 12, and the first nozzle 12 is used for spraying calcium oxide powder or calcium carbonate powder into the main hearth 2.
In the layer-combustion micro-fluidized boiler structure provided by the embodiment, the primary air supply openings are intensively arranged in the air chamber at the front of the bottom of the main hearth 2. The hot air preheated by the air preheater 16 is intensively fed into the main furnace 2 through a plurality of air chambers located at the front. The air chambers in front correspond to the main combustion area. That is, the primary air 7 is intensively and completely sent to the main burning zone, and the primary air 7 can not be sent to the warm burning zone.
The primary air 7 is intensively fed into the main combustion area, so that the air supply interval can be reduced, the local air supply quantity of the main combustion area is increased, the fuel on the grate 3, such as a coal bed, is changed into a low-suspension micro-fluidization state from a traditional moving state, and further, a partial suspension combustion mode is added on the basis of traditional grate combustion, so that the combustion speed is improved, the bed depth is reduced, the burnout stroke is shortened, and the combustion efficiency is improved; calcium oxide powder or calcium carbonate powder is sprayed into a proper area of a hearth, the calcium oxide powder or the calcium carbonate powder can react with acidic substances in smoke, and the calcium oxide powder or the calcium carbonate powder can be neutralized by acid and alkali and oxidized and reduced to realize in-furnace desulfurization.
Furthermore, the number of the air chambers near the front for feeding the primary air 7 into the main hearth 2 can be specifically set according to the size of the boiler, the feeding part of the primary air 7 corresponds to the main combustion area, and the number of the air chambers is reduced as much as possible, so that the local air supply quantity is increased as much as possible on the basis of meeting the combustion requirement of the main combustion area, and a coal bed low-suspension micro-fluidization state is formed better.
On the basis of the above embodiment, further, a structure of a layer-combustion microfluidization boiler further comprises a flue gas recirculation pipeline; the flue gas recirculation pipeline is communicated with at least one air chamber close to the rear part of the bottom of the main hearth 2 and the tail end of the tail flue 6 and is used for introducing the flue gas at the tail end of the tail flue 6 into the rear part of the bottom of the main hearth 2. The starting end of the tail flue 6 is connected with the outlet of the hearth. The end of the back pass 6, i.e. the part through which the flue gas flows, is closer to the end of the back pass 6, the lower the temperature of the flue gas.
According to the layer combustion microfluidization boiler structure provided by the embodiment, calcium oxide powder is sprayed into the boiler, so that the desulfurization in the boiler can be realized; part of the recirculated flue gas 8 is taken from the tail end of the tail flue 6 and sent into the main hearth 2, so that the combustion temperature of a combustion area in the main hearth 2 can be reduced, and the generation of thermal nitrogen oxides is reduced; the requirements of the sulfur oxide and the nitrogen oxide on the environmental protection emission are met, the investment of environmental protection equipment and the operation cost of the environmental protection equipment are reduced, and better economic benefit and social benefit are achieved; and the flue gas is introduced into the main hearth 2 again, thereby being beneficial to the full and complete combustion of the fuel, further improving the heat utilization rate and improving the heat efficiency.
The tail end of the tail flue 6 is provided with a smoke outlet which is connected with a smoke recirculation pipeline, the smoke recirculation pipeline is connected with an air chamber positioned at one side of the grate 3 close to the tail, and the smoke of the tail flue 6 is introduced to the rear of the main hearth 2.
The smoke taking port can be arranged on the side wall at the tail end of the tail flue 6 and used for leading out smoke. The flue gas recirculation pipeline is used for guiding the flue gas taken out from the flue gas taking port to one side of the fire grate 3 close to the tail part. The flue gas can contact with the ash at the tail part of the fire grate 3, thereby reducing the temperature of the ash, reducing the heat loss of the ash and improving the boiler efficiency.
The flue gas recirculation pipeline can be connected with 1-2 air chambers close to the tail part, namely the rear part, of the fire grate 3, and the number of the air chambers which are specifically connected is set according to the size of the boiler, so that the introduced recirculation flue gas 8 corresponds to the position of ash slag as much as possible. Further, a fan can be arranged on the flue gas recirculation pipeline to provide conveying power for the recirculated flue gas 8.
On the basis of the above embodiment, further, a secondary air inlet 5 is arranged on the top side wall of the main hearth 2 in an upward and downward direction, and the secondary air inlet 5 is connected with outside cold air.
The secondary air inlet 5 is used for introducing outside cold air as secondary air. The secondary air is blown downwards into the main hearth 2, the feeding direction of the secondary air is opposite to the flowing direction of the flue gas, and the flue gas can be used for blowing the flue gas into the main hearthUnburned carbon particles carried in the gas are blown back to the hearth, so that the combustion time of the hearth is prolonged, and the hearth is favorable for being burnt out. The secondary air graded air distribution is arranged, so that the high temperature generated by local violent combustion can be weakened, and NO is reducedxThe amount of production. The air distribution in stages can weaken local oxygen concentration and reduce NOxAnd (4) generating.
On the basis of the above embodiment, further, the first nozzle 12 is connected with the external hot air or connected with the tail flue 6 through a flue gas pipeline, and a pneumatic conveying device and a water removal device are arranged on the flue gas pipeline in series.
Namely, the calcium oxide powder or the calcium carbonate powder can be transported by hot air injection, and the tail flue gas can also be extracted from the tail flue 6 and transported by tail flue gas injection. When adopting afterbody flue gas to spray and carry calcium oxide powder or calcium carbonate powder, first nozzle 12 links to each other with the one end of outside flue gas pipeline, and the other end of flue gas pipeline links to each other with afterbody flue 6, and the last pneumatic conveyor and the water trap of establishing ties of flue gas pipeline are equipped with.
The tail flue gas is adopted to spray calcium oxide powder or calcium carbonate powder into the hearth, and has a certain temperature, so that the influence on combustion inside the hearth due to too low temperature can be avoided, the temperature of the hearth can be properly reduced, and the generation of nitrogen oxides can be reduced; meanwhile, tail flue gas is introduced into the hearth and can be combusted again, so that the combustion efficiency is improved, and the fuel is fully and completely combusted.
Because calcium oxide powder is hygroscopic, reacts with water to form alkali, is corrosive and generates a large amount of heat, and has the specific reaction formula: CaO + H2O→Ca(OH)2. Therefore, the water removal device is arranged, the introduced tail flue gas passes through the water removal device before being mixed with the calcium oxide powder, and the problem that the tail flue gas carries water to influence acid-base neutralization and redox reaction of the calcium oxide powder is avoided. Further, the pneumatic conveying device can be an air pump and is used for providing conveying power for the flue gas.
Further, when the first nozzle 12 injects calcium carbonate powder, the injection point of the calcium carbonate powder is located at the position where the temperature of the main furnace 2 is between 900 ℃ and 950 ℃. When the first nozzle 12 injects the calcium oxide powder, the injection point of the calcium oxide powder is located at the position where the temperature of the main furnace 2 is between 750 ℃ and 850 ℃. Taking the example of spraying calcium oxide powder, the acid-base neutralization and redox reaction are carried out in the temperature range, and the specific reaction formula is as follows:
CaO+SO2+1/2O2→CaSO4；
CaO＋SO3→CaSO4；
furthermore, the calcium oxide powder or the calcium carbonate powder can be ground to 200 meshes and sprayed into the hearth, which is beneficial to improving the reaction efficiency. The calcium oxide powder or calcium carbonate powder can be placed inside a storage box, the storage box is connected with the first nozzle 12, and a certain amount of calcium oxide powder is conveyed to the first nozzle 12 every time and enters the hearth through air flow injection.
On the basis of the above embodiment, further, a second nozzle 9 is arranged on the upper side wall of the main hearth 2, and the second nozzle 9 is used for spraying ammonia water or urea into the hearth; the first nozzle 12 is located below the second nozzle 9. Through spouting into aqueous ammonia or urea to the appropriate region of furnace, can realize the SNCR denitration in the stove, can reduce the environmental protection input to a certain extent, reduce the boiler and take up an area of, improve economic nature.
Furthermore, because the calcium oxide powder has hygroscopicity, reacts with water to generate alkali, is corrosive and is accompanied by a large amount of heat generation, the calcium oxide powder can be sprayed for desulfurization, and then ammonia water or urea is sprayed for denitration, so that the desulfurization and denitration can be smoothly carried out. Therefore, the first nozzle 12 can be provided at a position below the second nozzle 9. Further, the second nozzle 9 can be disposed in the region where the temperature of the main furnace 2 is 850-. The temperature of the area is proper, so that the denitration reaction is favorably carried out. The second nozzle 9 can be arranged towards the central part of the main hearth 2, so that the flue gas and the ammonia water or the urea are fully mixed and reacted.
A certain interval is arranged between the first nozzle 12 and the second nozzle 9, so that the calcium oxide powder and the ammonia water or the urea react with the flue gas in different areas, and the mutual influence between the calcium oxide powder and the ammonia water or the urea can be avoided to reduce the desulfurization and denitrification efficiency; and the smoke passes through the calcium oxide powder and then passes through the ammonia water or the urea, so that the calcium oxide powder can be prevented from moisture absorption and inactivation and corrosion.
On the basis of the above embodiment, further, the rear portion of the main furnace 2 is sequentially provided with the auxiliary furnace 4 and the convection channel 10 side by side, the top end of the main furnace 2 is communicated with the top end of the auxiliary furnace 4, the bottom end of the auxiliary furnace 4 is communicated with the bottom end of the convection channel 10, and the top end of the convection channel 10 is communicated with the tail flue 6.
The rear part of the main hearth 2 is the rear side in the flow direction of the flue gas, i.e. the part to which the flue gas flows backwards. The auxiliary furnace 4 and the convection channel 10 are also vertically arranged and are connected with the main furnace 2 in sequence side by side. The layer combustion boiler is additionally provided with an auxiliary hearth 4 and a convection channel 10 at the rear side of a main hearth 2. Flue gas generated by combustion of fuel in the main furnace 2 flows into the auxiliary furnace 4 through a top outlet, then flows from the top to the bottom of the auxiliary furnace 4 into the convection channel 10, and then flows into the tail flue 6.
According to the layer combustion boiler structure, the auxiliary hearth 4 and the convection channel 10 are sequentially arranged behind the main hearth 2 side by side, the top of the main hearth 2 is communicated with the auxiliary hearth 4, and the bottom of the auxiliary hearth 4 is communicated with the convection channel 10, so that the main hearth 2, the auxiliary hearth 4 and the convection channel 10 form an S-shaped three-return-stroke flue gas channel, the flow distance of flue gas can be effectively increased, the combustion time of fuel, namely pulverized coal, in a boiler is increased, and the combustion efficiency is improved; the products which are not fully combusted in the flue gas are reduced, the emission of sulfur oxides is favorably reduced, the environmental protection investment is reduced, and the economical efficiency is improved.
Furthermore, membrane type water-cooled walls are attached to the peripheral side walls of the main hearth 2 and the auxiliary hearth 4; the side wall of the convection passage 10 is also provided with a membrane water-cooling wall, and a convection heating surface 14 is arranged in the convection passage 10 to improve the use efficiency of heat. The membrane water-cooled wall is communicated with a downcomer which is connected with the boiler barrel 1.
On the basis of the above embodiment, further, the bottom of the main furnace 2 is provided with the grate 3, the bottom of the main furnace 2 covers the grate 3, the cross-sectional areas of the middle part and the top of the main furnace 2 are smaller than the cross-sectional area of the bottom, the auxiliary furnace 4 is bent, and a transition part 11 is arranged between the bottom end of the auxiliary furnace 4 and the bottom end of the convection channel 10.
That is, the fire grate 3 is completely positioned in the main hearth 2, the fire grate 3 has an unchanged structure compared with the original single hearth, the cross sections of the middle part and the top part of the main hearth 2 are reduced so as to reduce the occupied width of the main hearth 2, and the auxiliary hearth 4 and the convection passage 10 are arranged side by side.
The auxiliary hearth 4 and the convection channel 10 are arranged side by side with the top and the middle part of the main hearth 2, and the bottom of the auxiliary hearth 4 can be bent to enable the outlet to face one side above the fire grate 3; the convection channel 10 can also be arranged side by side with the auxiliary furnace 4 at the top and the middle part, and the bottom can be bent to enable the outlet to face to one side; the outlet at the bottom of the convection channel 10 can be located above the outlet at the bottom of the secondary hearth 4. In order to facilitate the communication between the bottom of the auxiliary hearth 4 and the bottom of the convection channel 10, the switching part 11 can be arranged to be communicated with the auxiliary hearth and the convection channel 10 respectively, and the flue gas turns at the switching part 11 and flows into the convection channel 10.
The structure of the arrangement structure can reduce the structural change of the existing boiler grate 3, the auxiliary hearth 4 and the convection channel 10 can be additionally arranged on the basis of the arrangement of the existing grate 3, the combustion efficiency can be improved on the basis of the original fuel combustion amount, and the pollutant emission can be reduced.
Further, the bottom and middle of the main hearth 2 may be bent.
On the basis of the above embodiment, further referring to fig. 3, the interior of the convection channel 10 is provided with an in-furnace dust removing device 13 and a convection heating surface 14, and the tail flue 6 is provided with an SCR denitration module, an economizer 15 and an air preheater 16 in sequence along the flow direction of flue gas. The flue gas outlet of the air preheater 16 is connected with the desulfurizing device 17 through an induced draft fan. The heat use efficiency is improved.
In addition to the above embodiments, a stratified combustion microfluidization combustion method based on the structure of the stratified combustion microfluidization boiler according to any one of the above embodiments further includes: the primary air 7 is intensively fed into the main hearth 2 through the air chamber close to the front side at the bottom of the main hearth 2, so that the fuel at the front side of the grate 3 is combusted in a suspended state.
The laminar combustion microfluidization combustion method provides that 7 volumes of all primary air required by combustion are intensively fed into a main combustion zone, fine coal particles can be completely combusted in a suspension state, medium coal particles are combusted under continuous loosening of air flow, heat in a coal layer is released into a hearth in time, high-temperature coking of the coal layer and accumulation of carbon dioxide can be prevented from influencing the combustion speed, and all coal can be rapidly combusted under high air flow speed. In the temperature combustion area, no air or a small amount of air can be fed, and the temperature of the hearth is utilized to separate out and burn volatile matters in the coal.
On the basis of the above embodiment, further, a laminar-flow and microfluidized combustion method further includes: extracting the recirculated flue gas 8 from the tail end of the tail flue 6, and sending the recirculated flue gas 8 to the rear of the bottom of the main hearth 2; secondary air is supplied into the main hearth 2 through a secondary air inlet 5.
The laminar combustion micro-fluidized combustion method extracts part of flue gas and sends the extracted flue gas into an air chamber of a burning zone, so that ash can be physically cooled, oxygen supplementation and combustion supporting can be simultaneously carried out on the ash, the heated flue gas rapidly flows forwards after entering the tail part of a hearth, a main burning zone can be cooled, the temperature of the hearth can be favorably controlled to be kept below 900 ℃, and the generation of nitrogen oxides can be inhibited. And oxygen in the flue gas is consumed in the combustion process, so that the oxygen content of the discharged flue gas can be effectively reduced, and the aims of improving the boiler efficiency and reducing nitrogen oxides are fulfilled.
Further, in the low suspension combustion process, the combustion stroke of the fine coal particles and a part of volatile gas can be prolonged, and the double-hearth boiler structure provided by the embodiment can increase the space and time of burning out, and is suitable for the low suspension combustion process.
On the basis of the above embodiment, further, the proportion of the primary air 7 in the total air supply amount is 75% -85%; the proportion of the secondary air in the total air supply amount is 15-25%; the primary fan pressure head is 30-50% higher than that of the traditional grate-firing boiler. The temperature of the recirculated flue gas 8 is less than or equal to 150 ℃; the proportion of the recycled flue gas 8 in the total flue gas is 15-25%. The flow velocity of the recirculated flue gas 8 into the main furnace 22 is 25-35 m/s. The total air supply is the preset and proper total air supply.
Specifically, a smoke taking port is arranged behind the air preheater 16 of the tail flue 6, the temperature of the smoke at the position is lower than 150 ℃, and the smoke is taken to be sent to an air chamber at the rear part of the grate 3, so that the cooling of slag is ensured. The circulation amount of the recirculated flue gas 8 is about 20% of the total flue gas amount. In actual operation, the variable frequency fan can be used to adjust the amount of the recirculated flue gas 8 to achieve the best effect.
On the basis of the above embodiment, further, a layered combustion and microfluidization combustion method further includes: calcium oxide powder or calcium carbonate powder is sprayed into the main hearth 2; the calcium oxide powder or calcium carbonate powder is sprayed into the main hearth 2 by the tail flue gas of the boiler.
Calcium oxide powder or calcium carbonate powder is sprayed into the hearth, and the in-furnace desulfurization can be realized through acid-base neutralization and redox reaction, so that the operation is simple and convenient, the environmental protection investment is small, and the economical efficiency is high. The calcium oxide powder is injected into the hearth by adopting tail flue gas, so that the calcium oxide powder is conveniently and fully mixed and reacted in the furnace, the temperature of the hearth can be reduced, and the generation of nitrogen oxides is reduced.
On the basis of the above embodiment, further, the injecting of the calcium oxide powder into the main furnace 2 specifically includes: spraying calcium oxide powder into the region of the main hearth 2 with the smoke temperature of 750-; the temperature of the area is proper, the mixing reaction of calcium oxide powder is facilitated, and sulfur oxides in the flue gas at the temperature are more, so that the desulfurization effect is improved. Furthermore, the calcium oxide powder can be ground to 200 meshes and injected into the hearth, so that the mixing reaction efficiency can be improved.
The calcium oxide powder is sprayed into the main hearth 2 by adopting the tail flue gas of the boiler, and the method specifically comprises the following steps: extracting the injected flue gas from the tail flue 6 and the front side or the rear side of the economizer 15, mixing the injected flue gas with the calcium oxide powder, and then injecting the mixture into the main hearth 2; and carrying out water removal treatment on the sprayed flue gas before mixing with calcium oxide powder.
On the basis of the above embodiment, further, the sprayed flue gas is taken from the flue gas with the temperature of 200-300 ℃ in the tail flue 6; the flow rate of the injected flue gas is determined according to the weight of the calcium oxide powder and the type of the pneumatic conveying device for injecting the flue gas; the weight of the calcium oxide powder is determined according to the desulfurization requirement of the boiler.
CaO powder is sprayed into the main hearth 2 by adopting tail flue gas, so that the CaO powder is convenient to be fully mixed and reacted in the hearth. The flue gas is taken from the tail flue 6 and can be positioned in front of or behind the economizer 15, and the temperature is selected according to the temperature calculated by heat power and is between 200 ℃ and 300 ℃. The flue gas amount is selected according to the weight of CaO powder required by desulfurization and the type of the selected pneumatic conveying device.
After the flue gas is sprayed into the main hearth 2, the temperature of the hearth can be reduced, and the generation of nitrogen oxides is reduced. It is noted that CaO powder is hygroscopic, reacts with water to form alkali, is corrosive, and is associated with a large amount of heat generation. Therefore, a dewatering device is required to be arranged before the tail flue gas is mixed with the CaO powder.
On the basis of the above embodiment, further, the calcium oxide powder can be injected into the main hearth 2 by using compressed air. The flow rate of the compressed air for injecting the calcium oxide powder is determined according to the weight of the calcium oxide powder and the type of the pneumatic conveying device for injecting the compressed air; the weight of the calcium oxide powder is determined according to the desulfurization requirement of the boiler. The ammonia water or urea is delivered by a pump and sprayed into the main hearth 2 in a compressed air atomization mode. Similarly, the flow rate of the compressed air for injecting the ammonia water or the urea is determined according to the weight of the ammonia water or the urea and the type of the pneumatic conveying device; the weight of the ammonia water or the urea is determined according to the denitration requirement of the boiler.
On the basis of the embodiment, the interval time between the calcium oxide powder spraying and the ammonia water or urea spraying into the main hearth 2 is longer than or equal to the preset time; the distance between the spraying area of the calcium oxide powder and the spraying area of the ammonia water or the urea is more than or equal to the preset distance. So as to prevent the calcium oxide powder from contacting ammonia water and reacting with the water to generate alkali, so that the nozzle is corroded and the normal desulfurization and denitrification are influenced.
The laminar-combustion microfluidization boiler structure and the laminar-combustion microfluidization combustion method provided by the embodiments can be used for desulfurization and denitrification in the boiler, and reduce the treatment intensity of pollutants at the tail part of the boiler. The boiler structure is provided with the auxiliary hearth 4 and the convection channel 10 to form a three-return flue gas flow path, and the structure of a boiler system is simplified; the investment of desulfurization equipment and the operating cost of the desulfurization equipment are reduced while the requirement of environmental protection emission is met; has better economic benefit and social benefit.
The layered combustion micro-fluidized boiler structure and the combustion method reduce the feeding interval of primary air 7 on the basis of the traditional layered combustion technology, and adopt the mode that the primary air 7 is intensively fed into a main combustion area, and simultaneously, part of flue gas is taken from the tail part of the boiler and is fed into the rear part of a fire grate 3 to control the temperature of a hearth, inhibit the generation of thermal nitrogen oxides, and realize low-suspension low-nitrogen combustion. The problems of low thermal efficiency and high emission of nitrogen oxides of the grate-fired boiler are solved, and the treatment intensity of pollutants (nitrogen oxides) of the grate-fired boiler can be reduced; the ash temperature is reduced, the heat loss of ash is reduced, and the boiler efficiency is improved; the combustion temperature of flame in the hearth is reduced, and the generation of nitrogen oxides is reduced; the method meets the requirement of environment-friendly emission of nitrogen oxides, reduces the investment of environment-friendly equipment and the operating cost of the environment-friendly equipment, and has better economic benefit and social benefit.
On the basis of the above embodiments, further referring to fig. 2 and fig. 4, the boiler structure and the combustion method described in the above embodiments are also applicable to a chain boiler, and the specific structural arrangement and the operation method of the chain boiler are similar to those of the above grate firing boiler, and are not described again.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (9)
1. A layer fires the little fluidized boiler structure, including the main burner hearth and afterbody flue mounted vertically, characterized by that, the bottom of the said main burner hearth has multiple independent air chambers side by side, the air preheater on the said afterbody flue couples to a plurality of air chambers near the front of bottom of the said main burner hearth, used for sending into the primary air to the inside of the said main burner hearth through the said air chamber is concentrated; a first nozzle is arranged on the side wall of the main hearth and used for spraying calcium oxide powder or calcium carbonate powder into the main hearth;
and a secondary air inlet is formed in the side wall of the top of the main hearth and faces downwards, and the secondary air inlet is connected with external cold air.
2. The grate firing microfluidization boiler architecture of claim 1, further comprising a flue gas recirculation duct; the flue gas recirculation pipeline is communicated with at least one air chamber close to the rear of the bottom of the main hearth and the tail end of the tail flue and used for introducing the flue gas at the tail end of the tail flue into the rear of the bottom of the main hearth.
3. The layered combustion microfluidization boiler architecture of claim 1, wherein the first nozzle is connected to hot outside air or to a back flue via a flue gas duct, and a pneumatic transport device and a water removal device are connected in series to the flue gas duct.
4. The grate firing microfluidization boiler architecture of claim 1, wherein a second nozzle is provided on an upper side wall of the main furnace, the second nozzle being configured to inject ammonia or urea into the furnace interior; the first nozzle is located below the second nozzle.
5. The grate firing microfluidization boiler structure according to claim 1, wherein a sub-furnace and a convection channel are provided side by side in the rear part of the main furnace, the top end of the main furnace communicates with the top end of the sub-furnace, the bottom end of the sub-furnace communicates with the bottom end of the convection channel, and the top end of the convection channel communicates with a tail flue.
6. The grate firing microfluidization boiler architecture of claim 5, wherein a grate is provided at the bottom of the main furnace, the bottom of the main furnace covers the grate, the cross-sectional areas of the middle and top of the main furnace are smaller than the cross-sectional area of the bottom, the sub-furnace is bent, and an adapter is provided between the bottom of the sub-furnace and the bottom of the convection channel.
7. A laminar-combustion microfluidization combustion method based on the structure of the laminar-combustion microfluidization boiler according to any one of claims 1 to 6, comprising:
the primary air is intensively fed into the main hearth through the air chamber close to the front side at the bottom of the main hearth, so that the fuel at the front side of the grate is combusted in a suspended state.
8. The laminar flow microfluidic combustion method according to claim 7, further comprising:
extracting the recirculated flue gas from the tail end of the tail flue, and sending the recirculated flue gas to the rear part of the bottom of the main hearth;
secondary air is supplemented into the main hearth through a secondary air inlet.
9. The laminar-flow microfluidized combustion method according to claim 8, wherein a proportion of the primary air in the total air supply is 75% to 85%; the proportion of the secondary air in the total air supply amount is 15-25%; the temperature of the recirculated flue gas is less than or equal to 150 ℃; the proportion of the recycled flue gas in the total flue gas is 15-25%; the primary fan pressure head is 30-50% higher than that of the traditional grate-firing boiler.
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| CN111878800A (en) * | 2020-08-04 | 2020-11-03 | 辽宁绿源能源环保科技集团有限责任公司 | Combustion method for micro-flow layer combustion boiler |
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