CN117329535A - Pollution-doped low-nitrogen combustion system of four-corner tangential high-temperature high-pressure pulverized coal boiler - Google Patents
Pollution-doped low-nitrogen combustion system of four-corner tangential high-temperature high-pressure pulverized coal boiler Download PDFInfo
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- 239000003245 coal Substances 0.000 title claims abstract description 116
- 238000002485 combustion reaction Methods 0.000 title claims abstract description 67
- 240000004282 Grewia occidentalis Species 0.000 title claims abstract description 18
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 15
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 11
- 239000010802 sludge Substances 0.000 claims abstract description 61
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 20
- 238000005243 fluidization Methods 0.000 claims abstract description 14
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 9
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23K—FEEDING FUEL TO COMBUSTION APPARATUS
- F23K1/00—Preparation of lump or pulverulent fuel in readiness for delivery to combustion apparatus
-
- 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
- F23C10/22—Fuel feeders specially adapted for fluidised bed combustion apparatus
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23K—FEEDING FUEL TO COMBUSTION APPARATUS
- F23K1/00—Preparation of lump or pulverulent fuel in readiness for delivery to combustion apparatus
- F23K1/04—Heating fuel prior to delivery to combustion apparatus
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23K—FEEDING FUEL TO COMBUSTION APPARATUS
- F23K3/00—Feeding or distributing of lump or pulverulent fuel to combustion apparatus
- F23K3/02—Pneumatic feeding arrangements, i.e. by air blast
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L1/00—Passages or apertures for delivering primary air for combustion
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L15/00—Heating of air supplied for combustion
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L9/00—Passages or apertures for delivering secondary air for completing combustion of fuel
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23K—FEEDING FUEL TO COMBUSTION APPARATUS
- F23K2201/00—Pretreatment of solid fuel
- F23K2201/10—Pulverizing
- F23K2201/1006—Mills adapted for use with furnaces
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23K—FEEDING FUEL TO COMBUSTION APPARATUS
- F23K2201/00—Pretreatment of solid fuel
- F23K2201/20—Drying
Abstract
The invention discloses a four-corner tangential high-temperature high-pressure pulverized coal boiler pollution-doped low-nitrogen combustion system, which relates to the technical field of boiler pulverized coal combustion, adopts a preheating combustion technology, adopts a mode of preheating and then burning, heats coal/sludge to 850-950 ℃ by utilizing partial heat of the coal/sludge in a fluidization preheating combustion device, then feeds the coal/sludge into a hearth for full combustion, adjusts relevant parameters of a coal mill, and achieves the purposes of flexibly regulating the peak of the depth of a boiler and reducing the original emission concentration of NOx, thereby improving the benefit of a power plant and reducing the emission of pollutants. Simultaneously, municipal sludge with 40% -45% of mixed water content is cooperatively treated according to the mass ratio of 10%, and the incinerated flue gas is subjected to purification treatment by depending on the existing flue gas treatment system, so that the secondary pollution is avoided.
Description
Technical Field
The invention relates to the technical field of pulverized coal combustion of boilers, in particular to a pollution-doped low-nitrogen combustion system of a pulverized coal boiler with four corners tangential to the circle and high temperature and high pressure.
Background
The sewage and the sludge are pollutants, and in the implementation process of the national energy conservation and emission reduction policy, the pollutants in the sewage are transferred to the sludge after being treated. The emission reduction of COD is realized, sewage is treated, the sludge is treated and reduced, the water content of the sludge after deep treatment can be reduced to about 60%, and the transportation cost is greatly reduced; meanwhile, the sludge subjected to advanced treatment is subjected to incineration treatment, and the generated waste heat can be recycled to further dry the sludge, so that the use of primary energy is reduced. Under the promotion of sustainable development and development routes of recycling economy, cities need to excavate and utilize recyclable resources like sludge as much as possible.
The literature ' feasibility analysis of blending and burning sludge of a high-temperature high-pressure pulverized coal furnace of 170t/h of a certain domestic thermal power plant ', ren Xiaoming ' discloses the problem of blending and burning coal and sludge of the high-temperature pulverized coal furnace, and the conclusion indicates that the blending and burning proportion is more proper at 5%, because the blending and burning proportion is limited by the hot air temperature of a boiler, the coal type, the combustion stability, the ash and slag bonding of a heated area, the boiler efficiency, secondary pollution and the like, and the problem cannot be solved by improving the proportion.
Meanwhile, the traditional coal powder high-efficiency combustion technology mainly comprises a quadrangle tangential combustion technology, a W-type flame combustion technology, an ultrafine coal powder combustion technology and the like. The four-corner tangential pulverized coal boiler has the characteristics of good fuel adaptability and uniform mixing of wind and powder, and is widely applied to the power station boiler industry in China. In the four-corner tangential pulverized coal boiler, the burners are arranged at four corners of a hearth, the axial direction of air flow at the outlet of each burner is directed to an imaginary tangential circle at the center of the hearth, and the pulverized coal air flow sprayed out of each burner is impacted and heated by intense combustion high-temperature flame from an upstream adjacent corner, so that the pulverized coal boiler fires quickly, smoke rises in the hearth in a rotating way, the flame stroke is longer, the pulverized coal residence time is longer, and the pulverized coal boiler is favorable for burning off pulverized coal. Through continuous improvement of the four-corner tangential firing technology, domestic scholars can show better effect when burning low-volatile coal-based fuel. However, the burning condition is not ideal when the anthracite is burned by using a four-corner tangential firing boiler in some domestic power plants. For example, the unstable combustion causes the fire extinguishment of a boiler, and oil is needed to be added for supporting combustion; some boilers are laid with a defending combustion belt to improve combustion stability, but the boilers are often coked; the problem that the smoke temperature deviation at the outlet of a hearth is generally caused by the rotation rise of internal smoke, the smoke temperature deviation is generally 50-60 ℃, and the smoke temperature of an individual power plant is as high as more than 150 ℃; when some boilers burn anthracite with lower volatile matters, the combustion efficiency of the pulverized coal is low, and the like.
Disclosure of Invention
In order to solve the defects and the shortcomings existing in the prior art, the invention provides the pollution-doped low-nitrogen combustion system of the pulverized coal boiler with four corners tangential to the circle, which realizes the purposes of flexibly adjusting the peak of the depth of the boiler and reducing the original emission concentration of NOx, thereby improving the benefit of a power plant and reducing the emission of pollutants. Simultaneously, municipal sludge with 40% -45% of mixed water content is cooperatively treated according to the mass ratio of 10%, and the incinerated flue gas is subjected to purification treatment by depending on the existing flue gas treatment system, so that the secondary pollution is avoided.
The invention adopts the technical proposal for solving the technical problems that:
the pollution-doped low-nitrogen combustion system of the four-corner tangential pulverized coal boiler comprises a boiler body, wherein the boiler body is provided with two layers of 8 fuel nozzles, 8 impeller powder feeders respectively correspond to one boiler nozzle, and pulverized coal is fed into corresponding combustors through hot air to form four-corner tangential combustion; the device also comprises 4 pulverized coal preheating burners, wherein each preheating burner corresponds to two layers of nozzles at one corner, and the temperature after preheating reaches 850-950 ℃;
the coal pulverizing system is characterized in that sludge is fed into a coal conveying stack bridge belt to be mixed with coal according to a ratio of 1:9, mixing the pulverized coal and the fuel into a stokehold pulverizing system, feeding the fuel into a low-speed barrel type steel ball coal mill under the action of a metering coal feeder and self gravity, drying by hot air, crushing by impacting and smashing steel balls, and feeding pulverized coal into a hearth by a powder exhauster from the upper part of a fine powder separator to participate in combustion;
the flue gas system is characterized in that the air of the blower is preheated by the preheater and then is divided into four paths to enter the hearth, the preheating temperature of the air is 324 ℃, the second path is to convey pulverized coal at the lower part of the pulverized coal storage bin to enter the hearth, namely primary air, the preheating temperature of the primary air is 161 ℃, the third path is to enter the hearth from a burner nozzle, namely secondary air, the third path is to enter the coal mill, the secondary air is merged into the hearth from exhaust air, namely tertiary air, and the fourth path is to be sprayed into the hearth from SOFA air.
Preferably, the water content of the sludge is 40-45% municipal sludge, and the temperature is not higher than 40 ℃.
Preferably, the primary air rate is 24%, the secondary air rate is 23%, the tertiary air rate is 23%, and the SOFA air rate is 30.4%.
Preferably, the inlet hot air temperature of the high coal mill is higher than 260 ℃, meanwhile, the water content of the coal powder is adjusted to be 5%, and the fineness R90 of the coal powder is adjusted to be 20-22%.
Preferably, the preheating burner further comprises an auxiliary machine system, wherein each preheating burner is provided with 2 powder feeding fans and 1 fluidization fan, and a powder feeding pipeline and a fluidization air pipeline are correspondingly arranged.
Compared with the prior art, the invention has the following beneficial effects:
1. the rated load of the boiler reaches 170t/h, and the load adjusting range is 30-110%;
2. the sludge mixing amount is 10 percent (mass ratio);
NOx original emission is less than or equal to 150mg/m 3 ；
4. The preheating combustion system is safe and reliable, the system is optimized, the functions are complete, and the normal operation of the boiler is not influenced.
5. The maximum smoke temperature deviation of the hearth outlet is not more than 60 ℃.
6. The coking of the boiler mixed-burned sludge is not deteriorated to the original extent.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The four corners circle of tangency pulverized coal fired boiler that this embodiment provided mixes dirty low nitrogen combustion system adopts the boiler model: UG170/9.8-M type boiler, on the basis of which the structure is modified, realizes the sludge co-combustion.
Boiler type: high-temperature high-pressure single-drum natural circulation pulverized coal furnace
Boiler design conditions:
main parameters of boiler
| Name of the name | Unit (B) | 170t/h of No. 1 pulverized coal furnace |
| Boiler design efficiency | ％ | 91 |
| Exhaust gas temperature | ℃ | 140 |
| Design of fuel consumption | kg/h | 21836 |
| Flow rate of flue gas | m 3 /h | 309117 |
The boiler body has 8 fuel nozzles in two layers, 8 impeller powder feeders are arranged at the bottom of a coal powder storage bin, each powder feeder corresponds to one boiler nozzle, and coal powder is fed into corresponding combustors through hot air to form four-corner tangential combustion.
According to the invention, the four corner tangential firing and preheating firing technology is combined, 4 pulverized coal preheating burners are newly added, each preheating burner corresponds to two layers of nozzles at one corner, 4 preheating burners are arranged in the ground space of two side walls of a hearth, and two preheating burners are arranged on each side and are supported by independent steel frames. The preheated fuel at the outlet of the preheating burner is divided into two parts, and enters the upper and lower burners at one corner of the hearth respectively, and the preheated fuel is injected into the furnace to form tangential circles at four corners.
Pulverized coal is sprayed into a furnace through eight nozzles at four corners of an upper layer and a lower layer, the cross section size of a hearth is 7090x 7090mm2, tangential combustion is formed, the imaginary tangential diameter in the furnace is 600mm, flue gas generated by pulverized coal combustion enters a bag-type dust collector after passing through a waste heat recovery system and an SCR denitration device, and the flue gas discharged from the bag-type dust collector is led to a desulfurization wet electric device by an induced draft fan for further purification and then is discharged to a chimney.
The four-corner tangential combustion and the preheating combustion technology are combined, the pulverized coal is firstly heated to 850-950 ℃ by utilizing partial heat of the pulverized coal in a fluidization preheating combustion device, and then is fed into a hearth for full combustion, and the pulverized coal has the advantages that:
(1) Fuel ignition stabilization
Because the coal dust and the sludge are preheated and then burnt, the preheated gas contains CO and H 2 And CH (CH) 4 And combustible components, and the preheating temperature of the fuel reaches 850-950 ℃ and exceeds the ignition temperature of carbon particles, so that the fuel preheated at high temperature can be quickly ignited and burned when meeting air after being sprayed into a hearth, and the low-load combustion is stable and does not have flameout problem.
(2) High combustion efficiency
CO, H generated after fuel preheating 2 And CH (CH) 4 The homogeneous phase gas combustion rate is high, the inner holes of the preheated solid particles are increased, the activity is enhanced, the temperature is high, the combustion reaction rate can be improved after the high-temperature preheated fuel is sprayed into a hearth, the burnout time is shortened, and the efficient combustion is realized.
(3) Low nitrogen oxide emission level
In the fuel preheating process, the mixture ratio of fuel and air is controlled, the whole preheating device is in a reducing atmosphere, fuel elements are easy to convert into nitrogen after being separated out during preheating, and the boiler can realize low nitrogen oxide emission by combining with deep staged combustion of the preheated fuel in the boiler.
(4) Wide fuel application range
The temperature reaches 850-950 ℃ after preheating, and the gas contains CO and H 2 And CH (CH) 4 And the combustible components such as the coal are stable in ignition, the adaptability of the boiler combustion coal is improved, and the coal with low volatile matters and high ash content can stably run.
(5) Wide range of boiler load adjustment
Because the ignition is stable after the fuel is preheated, the boiler can realize stable combustion without feeding oil under extremely low load, the adjusting range of the load of the boiler is increased, and the boiler can realize deep peak shaving.
(6) The combustion adjustment speed is fast
In the preheating combustion process, partial coal powder is gasified, and the preheated gas contains CO and H 2 And CH (CH) 4 And combustible components, the gases are sent to a hearth for re-combustion together with preheated solid fuel, and the presence of the combustible gases increases the combustion regulation rate of the boiler.
The boiler is provided with 2 sets of powder making systems with intermediate storage bins and hot air powder feeding of drying agents. The sludge conveying system, the newly built sludge scraper, is modified by utilizing the existing coal conveying belt. The dry sludge in the receiving bin is sent to the existing coal conveying pallet belt through a newly built sludge scraper machine, and is mixed with the fire coal to enter a stokehold pulverizing system, and each pulverizing system is provided with a volume of 206m 3 The raw coal bin of (2) is characterized in that fuel enters a low-speed barrel type steel ball coal mill under the action of a metering coal feeder and self gravity, is crushed through hot air drying and collision and smashing of steel balls, is pumped into a separator by a powder exhauster, is cleaned by the separator and then is discharged out of a powder making system, coal dust is continuously pumped into a coarse powder separator, coarse powder is separated under the action of gravity and centrifugal force, is sent into the coal mill through a powder return pipe to be continuously ground, fine powder is pumped into the fine powder separator to be separated, and qualified coal dust is separated out and enters 185m in volume through the wood dust separator 3 The finer pulverized coal is discharged from the upper part of the fine powder separatorThe powder machine is sent into a hearth to participate in combustion. Each boiler is provided with 2 ball mills, 8 impeller powder feeders are arranged at the bottom of the coal dust storage bin, and each powder feeder corresponds to one boiler nozzle.
The invention is also provided with a negative pressure deodorizing system, the odor source is the space low-concentration gas between the dry sludge unloading room and the conveying equipment, the main components are hydrogen sulfide, ammonia gas and the like, the stainless steel 304 is adopted as a frame structure of the housing in the embodiment, the existing coal conveying belt is sealed, and the functions of opening and closing the top plate, overhauling the side plate, moving the door and the like are realized to a certain extent according to the use requirement of the equipment. Simultaneously, two newly-increased negative pressure air extraction fans are used for collecting air exchange in space in a dry sludge unloading workshop and a sealed cover, so that peculiar smell is ensured not to be emitted to the external space of the workshop, and space odor collected by the negative pressure air extraction fans is sent into a boiler air feeder inlet and enters a hearth as air required by boiler combustion to participate in combustion, thereby avoiding secondary pollution
Because the project needs to mix and burn the sludge, 8 powder feeders at the bottom of the powder bin need to be replaced by reselection, and 2 paths of powder feeding is arranged on each preheating burner so as to meet the required powder feeding amount under different load working conditions. Wherein the powder feeding pipeline 1 is designed to have the powder feeding amount of 3.8t/h and the powder feeding air quantity of 1200m 3 And/h, the powder feeding speed is 31m/s; the powder feeding pipeline 2 is designed to feed 1.6t/h of powder, and the powder feeding air quantity is designed to be 600m 3 And/h, the powder feeding speed is 33m/s. The preheating burner only operates the powder feeding pipeline 2 when the preheating burner is operated under 30 percent of load, only operates the powder feeding pipeline 1 when the preheating burner is operated under 30 percent of load to 70 percent of load, and simultaneously operates the powder feeding pipeline 1 and the powder feeding pipeline 2 when the preheating burner is operated under 70 percent of load.
The auxiliary machine system of the invention comprises a powder feeding fan: 8 powder feeding and pressurizing fans and 8 fluidization fans are added, wherein the fluidization fans are designed according to one standby for each preheating burner, frequency conversion control is adopted, and each preheating burner is provided with 2 powder feeding fans and 2 fluidization fans. Wherein, the design air quantity of four powder feeding fans is 1200m 3 And/h, the wind pressure is 30.0kPa, which corresponds to the powder feeding pipeline A; four powder feeding fans are designed to have 600m of design air quantity 3 And/h, the wind pressure is 30.0kPa, which corresponds to the powder feeding pipeline B; the fluidization air quantity is 2500m 3 And/h, the air pressure of the fluidization fan is 20.0kPa. Powder feeding pressurized airThe machine is arranged nearby the powder bin layer empty space of the main plant. The fluidization fans are arranged nearby the air spaces near the corresponding pulverized coal preheating burners. Simultaneously, a powder feeding air pipeline and a fluidization air pipeline are arranged, the powder feeding air speed is about 38.0m/s, and the fluidization air speed is 12.0m/s.
For the selection of the blended burnt sludge in the invention, the applicant tests the water content and the blending proportion of the sludge, wherein the blending proportion is 5%, 8% and 10% of the amount of the coal to be charged, the sludge is transported to a dry coal shed, mixed with the coal according to the proportion, and then added into a bin, and the amount of the sludge to be charged is about 50 t/d-80 t/d. Through a blending burning test, when the blending burning of the sludge with the water content of about 55 percent, the coal conveying system and a stokehold coal dropping pipe are easy to be blocked, and the running stability and the economical efficiency of the pulverized coal furnace are affected due to the lower calorific value of the sludge (about 400-500 Kcal/Kg); when the water content of the sludge is about 35%, the lower calorific value of the sludge is about 900-1000 Kcal/Kg, the self-sustaining combustion can be maintained, the influence on the combustion is small, but when the water content of the sludge is 35% or below, the property of the sludge is powdery, a large amount of dust emission is easy to generate, the environmental sanitation is influenced, and meanwhile, the odor overflow risk exists in the periphery of the dry coal shed. The smaller the blending ratio is, the larger the adaptive water content range is, but the water content has outstanding influence on blocking phenomenon and dust emission, and through a large number of calculation and experiments, the sludge water content is optimal in the range of 40% -45%, the combustion stability and the environmental influence are minimum, and the combustion of the highest 10% sludge blending ratio can be satisfied. Meanwhile, the temperature of the sludge is ensured to be below 40 ℃, and the risk of blockage of a conveying system caused by water vapor condensation of the high-temperature sludge above 40 ℃ is avoided. Meanwhile, the easily blocked part is cleaned regularly, and vibration measures are added.
In the embodiment, the sludge source is blue algae sludge which is invested and constructed by tin-free national environmental protection technology and technology share limited company and dried sludge which is produced by municipal sludge treatment engineering projects. The test data are as follows:
the sludge was blended with coal at 1:9 and the fuel analysis of the coal and sludge was as follows:
because 40% -45% of the water content of the sludge in the pulverizing system is mixed into the coal mill, parameters of the coal mill need to be adjusted, the specific drying output is realized, the hot air temperature (more than 260 ℃) of the inlet of the coal mill is improved, meanwhile, the water content (5%) of coal dust is adjusted, the grinding output is realized, the original coal mill can stop for 2-3 hours after running for 8 hours, the fineness R90 to 20-22% of the coal dust can be properly adjusted after the sludge is mixed, and because the coal mill is used as tertiary air by the exhaust gas of the coal mill, the water content of the tertiary air is increased after the sludge enters the coal mill, and the tertiary air enters the boiler for stabilizing combustion and NO X The emission has influence, the tertiary air rate needs to be improved, and after experimental calculation, when the tertiary air rate reaches 29.2, the stable operation requirement can be met, and the original emission concentration of the boiler NOx is less than or equal to 150mg/Nm 3 . The coal mill calculation data are as follows:
the tertiary air rate is increased again, and when the tertiary air rate reaches 30.4%, the original emission of boiler NOx reaches 95mg/Nm 3 . And the tertiary air rate is continuously increased, the smoke temperature deviation at the outlet of the hearth is increased, and slag bonding is increased. When UG170/9.8-M boiler is not mixed with sludge for combustion, NOx emission can reach that the nitrogen oxide in Jiangsu province landmark (emission standard of atmospheric pollutants of coal-fired Power plant) (DB 32/4148-2021) is not higher than 50mg/Nm 3 But the original discharge concentration of the boiler is 400-600mg/Nm 3 Left and right. By adopting the technical scheme of the invention, the emission of NOx is greatly reduced while the original standard requirements are met, and the energy conservation and emission reduction and sludge resource utilization in the economic development process are further promoted.
The invention cooperatively treats municipal sludge with 40-45% of water content after green technology drying, and the blending ratio is 10% (mass ratio). The fuel coal consumption is 23.481t/h under the rated working condition of the modified mixed-combustion sludge, and the sludge (the water content is 40% -45%) consumption is 2.609t/h; the fuel consumption of the pure coal under the rated working condition is 23.515t/h. The boiler can be used for mixing and burning municipal sludge after dehydration and desiccation for about 50t/d, and the cost of outward transportation and disposal of the sludge can be reduced.
The variable load operation strategy of the boiler is as follows:
because the boiler uses the exhaust gas of the coal mill with powder as tertiary air, two coal mills simultaneously operate under 50% -100% load, and the powder content in the tertiary air in the load range is 15% of the powder feeding amount under full load; the coal mill operates under 50% load, and the powder content in tertiary air in the load range is 7.5% of the powder feeding amount under full load. The powder amount in the tertiary air does not change along with the change of the boiler load, and the tertiary air brings difficulty to the stable operation and the NOx emission control under the low load of the boiler.
In addition, the coal mill can stop running for a short time in the running process of the boiler, at the moment, the exhaust gas of the coal mill is stopped, the air quantity of tertiary air is required to be directly complemented from the preheated air, and the powder quantity in the tertiary air is required to be complemented from the preheated burner, so that the tertiary air is required to be directly connected to a main pipeline of the preheated air through a pipeline and is controlled through a valve.
In order to meet the requirements of stable load change and low NOx combustion of a boiler, under the current situation that the existing powder feeding system is not changed, the coal mill cannot be put into operation when the modified boiler is required to run below 40% load, tertiary air of the boiler cannot be exhausted by the coal mill, all coal is fed into a hearth from a preheating burner, a certain amount of coal dust is ensured in the hearth, and the low-load continuous operation of the boiler is met for 8 hours. When the load of the boiler is lower than 30%, the boiler needs to be changed from tangential operation at four corners to diagonal operation.
When the boiler load is lower than 60%, the blower and the induced draft fan can be started according to the operation requirement.
The operating parameters of the preheating burner, the secondary air, the tertiary air and the sofa air of the boiler under different loads are shown in the following table:
boiler operating parameters under different loads
| Operating load | 100％ | 100% (mix-burned sludge) | 50％ | 30％ | |
| Evaporation capacity | t/h | 170 | 170 | 85 | 51 |
| Main steam temperature | ℃ | 540 | 540 | 530 | 515 |
| Main steam pressure | MPa | 9.8 | 9.8 | 9.8 | 9.1 |
| Water supply temperature | ℃ | 215 | 215 | 215 | 158 |
| Coal consumption | Kg/h | 23515 | 26090 | 11632 | 7475 |
| Number of coal mill runs | Bench | 2 | 2 | 1 | 0 |
| Temperature of hot air | ℃ | 330 | 330 | 294 | 240 |
| Exhaust gas temperature | ℃ | 140 | 142 | 123 | 95 |
| Smoke volume | Nm3/h | 196636 | 202953 | 104986 | 69347 |
| Air quantity | Nm3/h | 171929 | 171929 | 90262 | 56098 |
| Boiler efficiency | ％ | 91.7 | 91.5 | 91.3 | 91.1 |
The original UG170/9.8-M type boiler load peak regulation capability is between 60% and 110%, the combustion stability is poor during low-load operation, the original emission concentration of boiler NOx can be effectively reduced by adopting a preheating combustion technology, the ecological environment of a service area is improved, the boiler depth flexible peak regulation function is synchronously realized, and the boiler can stably operate under 30% -110% of load.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (6)
1. The pollution-doped low-nitrogen combustion system of the four-corner tangential pulverized coal boiler is characterized by comprising a boiler body, wherein the boiler body is provided with two layers of 8 fuel nozzles, each of 8 impeller powder feeders corresponds to one boiler nozzle, and pulverized coal is fed into corresponding combustors through hot air to form four-corner tangential combustion; the device also comprises 4 pulverized coal preheating burners, wherein each preheating burner corresponds to two layers of nozzles at one corner, and the temperature after preheating reaches 850-950 ℃;
the coal pulverizing system is characterized in that sludge is fed into a coal conveying stack bridge belt to be mixed with coal according to a ratio of 1:9, mixing the pulverized coal and the fuel into a stokehold pulverizing system, feeding the fuel into a low-speed barrel type steel ball coal mill under the action of a metering coal feeder and self gravity, drying by hot air, crushing by impacting and smashing steel balls, and feeding pulverized coal into a hearth by a powder exhauster from the upper part of a fine powder separator to participate in combustion;
the flue gas system is characterized in that the air of the blower is preheated by the preheater and then is divided into four paths to enter the hearth, the preheating temperature of the air is 324 ℃, the second path is to convey pulverized coal at the lower part of the pulverized coal storage bin to enter the hearth, namely primary air, the preheating temperature of the primary air is 161 ℃, the third path is to enter the hearth from a burner nozzle, namely secondary air, the third path is to enter the coal mill, the secondary air is merged into the hearth from exhaust air, namely tertiary air, and the fourth path is to be sprayed into the hearth from SOFA air.
2. The four corner tangential pulverized coal boiler pollution-doped low nitrogen combustion system according to claim 1, wherein the municipal sludge with the water content of 40% -45% is at a temperature not higher than 40 ℃.
3. The four corner tangential pulverized coal fired boiler fouling low nitrogen combustion system according to claim 1, wherein the primary air rate is 24%, the secondary air rate is 23%, the tertiary air rate is 23% and the SOFA air rate is 30.4%.
4. The low nitrogen-doped combustion system of a four corner tangential pulverized coal boiler according to claim 1, wherein the inlet hot air temperature of the high coal mill is higher than 260 ℃, and the pulverized coal moisture is adjusted to 5%, and the pulverized coal fineness R90 is adjusted to 20-22%.
5. The low nitrogen-doped combustion system of the four-corner tangential pulverized coal boiler according to claim 1, further comprising an auxiliary machine system, wherein each preheating burner is provided with 2 powder feeding fans and 1 fluidization fan, and a powder feeding air pipeline and a fluidization air pipeline are correspondingly arranged.
6. A method of preheat combustion employing the system of any of claims 1-5.
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