CN112032709B - Ultra-low NOx emission system and method adopting combination of pre-pyrolysis and ammonia injection - Google Patents

Ultra-low NOx emission system and method adopting combination of pre-pyrolysis and ammonia injection Download PDF

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CN112032709B
CN112032709B CN202010891121.5A CN202010891121A CN112032709B CN 112032709 B CN112032709 B CN 112032709B CN 202010891121 A CN202010891121 A CN 202010891121A CN 112032709 B CN112032709 B CN 112032709B
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boiler
pyrolysis
pulverized coal
temperature
pipeline
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CN112032709A (en
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孙同敏
贺延枫
武兴卓
赵俊杰
任杰
李永生
谢国峰
张二祥
兰俊生
李建军
王淋韵
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Guodian Inner Mongolia Dongsheng Thermal Power Co Ltd
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Guodian Inner Mongolia Dongsheng Thermal Power Co Ltd
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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 
    • F23C5/00—Disposition of burners with respect to the combustion chamber or to one another; Mounting of burners in combustion apparatus
    • F23C5/08—Disposition of burners
    • 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 
    • F23C9/00—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber
    • F23C9/003—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber for pulverulent fuel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D1/00—Burners for combustion of pulverulent fuel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J7/00—Arrangement of devices for supplying chemicals to fire
    • 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 
    • F23C2202/00—Fluegas recirculation
    • F23C2202/10—Premixing fluegas with fuel and combustion air
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)

Abstract

The invention discloses an ultra-low NOx emission system and method combining pre-pyrolysis and ammonia injection, relating to the technical field of pulverized coal combustion, and being characterized by comprising a pulverized coal pre-pyrolysis device, a pulverized coal pre-pyrolysis device and a pulverized coal pre-pyrolysis device, wherein the pulverized coal pre-pyrolysis device is arranged to enable pulverized coal to be controllably pre-pyrolyzed at high temperature to realize ultra-low NOx emission, the ammonia injection is carried out on a high-temperature area of a boiler hearth to realize ultra-low NOx emission, and the pulverized coal pre-pyrolysis device is additionally arranged in front of the boiler hearth and is communicated with a reduction area of the boiler hearth; the coal powder pre-pyrolysis device is provided with a plasma igniter, and primary air and coal powder are introduced from a primary air pipeline to carry out pre-pyrolysis; introducing flue gas into the pulverized coal pre-pyrolysis device, controlling the combustion intensity and temperature in the boiler hearth, and directionally generating reductive pyrolysis products; adding multiple layers of ammonia guns in a high-temperature area of a boiler hearth, and decomposing at high temperature to generate a reducing agent NH by spraying urea solution 3 (ii) a NH formed by reductive pyrolysis products and urea solution 3 And reducing NOx generated by combustion in the main combustion zone to achieve the aim of ultralow NOx emission of the boiler.

Description

Ultra-low NOx emission system and method using pre-pyrolysis in combination with ammonia injection
Technical Field
The invention relates to the technical field of pulverized coal combustion, in particular to an ultra-low NOx emission system and method adopting the combination of pre-pyrolysis and ammonia injection.
Background
In the prior art, the occupied ratio of coal in the whole energy structure is still large, and NOx generated by coal combustion harms the environment. In China, in order to enable the concentration of NOx in boiler flue gas to reach the specified emission standard, most of thermal power generating units rely on the measures of conventional low NOx combustion modification and denitration system addition to meet the emission standard, but the defects of cost increase, boiler coking and the like are overcome. How to realize the ultra-low NOx emission of the pulverized coal fired boiler on the premise of not increasing the cost is a technical problem which is eagerly solved by the technical personnel in the field and is not solved so far.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and the NOx emission concentration of a thermal power plant is 100 mg/m 3 The standard of provides an ultra-low NOx emission system which is reasonable in structure, does not increase equipment cost and reduce operation cost, can meet the requirement of NOx emission concentration of a thermal power plant and adopts the combination of pre-pyrolysis and ammonia injection, and can be widely applied to the transformation of in-service boilers and the design of new boilers; and provides a scientific and reasonable ultralow NOx emission method with strong applicability and good effect by combining pre-pyrolysis with ammonia injection.
The technical scheme adopted for realizing one of the purposes of the invention is as follows: 1. an ultra-low NOx emission system combining pre-pyrolysis and ammonia injection comprises a boiler body, a primary air pipeline, a boiler X-layer burner, a boiler lower-layer burner, a boiler over-fire air nozzle and a boiler flue, wherein at least one boiler lower-layer burner is arranged on the boiler body and opposite to the main combustion area of a boiler hearth, at least one boiler X-layer burner is arranged on the boiler body and between the main combustion area of the boiler hearth and a reduction area of a high-temperature area, the ultra-low NOx emission system is characterized by further comprising a flue gas temperature control pipeline inserting plate door, a boiler X-layer burner pipeline inserting plate door, a pulverized coal pre-pyrolysis device input pipeline inserting plate door, a pulverized coal pre-pyrolysis device plasma igniter, a pulverized coal pre-pyrolysis device, a pyrolysis product burner, a high-level ammonia injection gun, a low-level ammonia injection gun, flue gas recirculation and a high-pressure fan, at least one pyrolysis product burner is arranged on the boiler body and opposite to the reduction area of the high-temperature area of the boiler hearth, a high-temperature ammonia spraying area is arranged on the boiler body and above the position of a reduction area corresponding to a high-temperature area of a boiler hearth, a plurality of high-level ammonia spraying guns are arranged on the upper layer of the boiler body and the position corresponding to the high-temperature ammonia spraying area of the boiler hearth, a plurality of low-level ammonia spraying guns are arranged on the boiler body and on the lower layer of the position opposite to the high-temperature ammonia spraying area of the boiler hearth, a smoke recycling induced draft fan is arranged at a smoke outlet of a boiler flue, a high-pressure fan is arranged at an overfire air nozzle of a boiler body 17, the primary air pipeline is communicated with a boiler flue through a flue gas temperature control pipeline inserting plate door and a flue gas recirculation induced draft fan, the primary air pipeline is communicated with the boiler X-layer combustor through a pipeline inserting plate door of the boiler X-layer combustor, the primary air pipeline is communicated with the air inlet end of the plasma igniter of the pulverized coal preheating and decomposing device through the inserting plate door of the input pipeline of the pulverized coal preheating and decomposing device, and the controllable high-temperature outlet end of the pulverized coal preheating and decomposing device is communicated with the pyrolysis product burner.
The second technical scheme adopted for achieving the purpose of the invention is as follows: a method for ultra-low NOx emission by combining pre-pyrolysis with ammonia injection is characterized by comprising the following steps:
1) the coal dust pre-pyrolysis device is arranged to ensure that the coal dust can be controllably pre-pyrolyzed at high temperature to realize ultralow NOx emission
The pulverized coal pre-pyrolysis device is adopted, the directional generation of reducing substances in the pulverized coal high-temperature pyrolysis process is controlled, the burnout of solid particles is improved, the generation of thermal nitrogen oxides is inhibited, the NOx in a boiler hearth is deeply reduced by utilizing pyrolysis gas, and the ultralow emission of the NOx under the high burnout condition is realized;
the pulverized coal pre-pyrolysis device introduces a mixture of air and pulverized coal in a specific proportion from a primary air pipeline and through a pulverized coal pre-pyrolysis device input pipeline plug board door, after ignition of a plasma igniter of the pulverized coal pre-pyrolysis device, controllable high-temperature pre-pyrolysis is carried out in the pulverized coal pre-pyrolysis device, the pre-pyrolysis temperature is 850-1000 ℃, pyrolysis products are conveyed into a hearth to reduce NOx generated by combustion in a main combustion area, a high-pressure fan arranged on an over-fire air nozzle is pressurized to improve the speed of separated over-fire air, at 80-100 m/s, the pyrolysis products are connected with a boiler hearth reduction area, and the NOx reduction efficiency of synthesis gas is 50-85% through controllable high-temperature pre-pyrolysis; a flue gas recirculation induced draft fan arranged at a flue outlet of a boiler flue enables the flow velocity of flue gas to be more than or equal to 36m/s, and can effectively prevent powder accumulation and slag bonding of a pipeline;
2) ultra-low NOx emission by ammonia injection into high temperature zone of boiler furnace
The method is characterized in that at least one pyrolysis product burner is arranged at a position corresponding to a reduction zone of a high-temperature zone of a boiler furnace, so that the temperature of the high-temperature zone of the boiler furnace is 1200-1400 ℃, a plurality of high-level ammonia spraying guns are arranged at the upper layer of the high-temperature ammonia spraying zone, a plurality of low-level ammonia spraying guns are arranged at the lower layer of the high-temperature ammonia spraying zone, the medium sprayed by the ammonia spraying guns is an amino reducing agent, a urea solution with the concentration of 10% is adopted, a steam channel is arranged in an inner pipe of a spray gun, a urea solution channel is arranged in a middle pipeline, a high-pressure steam channel is arranged in an outer sleeve pipe, the flow range of the urea solution is 0-120L/h, the pressure is 0.4-0.6 MPa, the steam pressure is 0.6-0.8 MPa, the ammonia spraying amount of each spray gun can be adjusted, the adjustment range of the ammonia spraying ratio NSR (the molar ratio of the reducing agent to NOx in the flue gas) value of the urea solution with the concentration of 10% to the ammonia nitrogen oxide in the flue gas is 0-2.5, and the NSR in the operation of the furnace is 1.5-2.0h, NH of urea solution decomposition in pulverized coal flame 3 Mixing with NOx in flue gas to reduce NOx into N 2 。
The invention discloses an ultra-low NOx emission system and method combining pre-pyrolysis and ammonia injection, and has the advantages that:
because the pulverized coal pre-pyrolysis device is added in front of the boiler hearth, the pulverized coal pre-pyrolysis device is communicated with the reduction region of the high-temperature region of the boiler hearth; the top of the pyrolysis device is provided with a plasma igniter of a pulverized coal pre-pyrolysis device, primary air is introduced from a primary air pipeline and preheated with pulverized coalSolving; introducing flue gas into the pulverized coal pre-pyrolysis device, controlling the combustion intensity and temperature in the boiler hearth, and directionally generating reductive pyrolysis products; set up high temperature at boiler furnace high temperature district and spout the ammonia district, spout the upper strata of ammonia district position at boiler furnace high temperature and set up a plurality of high-order and spout the ammonia rifle, spout the ammonia rifle and through spouting urea solution, pyrolysis generates reductant NH 3 (ii) a NH formed by reductive pyrolysis products and urea solution 3 And reducing NOx generated by combustion in the main combustion zone to achieve the aim of ultralow NOx emission of the boiler. The system has reasonable structure, does not increase equipment cost and reduce operation cost, can meet the requirement of NOx emission concentration of a thermal power plant, and can be widely applied to the transformation of in-service boilers and the design of new boilers; the method is scientific and reasonable, and has strong applicability and good effect.
Drawings
FIG. 1 is a schematic diagram of an ultra-low NOx emission system using pre-pyrolysis in combination with ammonia injection in accordance with the present invention.
In the figure, 1 primary air pipeline, 2 flue gas temperature control pipeline spile door, 3 boiler X layer combustor pipeline spile door, 4 pulverized coal pre-pyrolysis device input pipeline spile door, 5 pulverized coal pre-pyrolysis device plasma igniter, 6 pulverized coal pre-pyrolysis device, 7 pyrolysis product combustor, 8 high position ammonia spraying gun, 9 low position ammonia spraying gun, 10 boiler low layer combustor, 11 boiler burn-out air nozzle, 12 boiler furnace, 13 boiler X layer combustor, 14 high temperature ammonia spraying area, 15 high temperature area reduction area, 16 main combustion area, 17 boiler body, 18 flue gas recirculation draught fan, 19 boiler flue, 20 high pressure draught fan.
Detailed Description
The present invention will be described in further detail with reference to fig. 1 and specific examples, which are provided herein for the purpose of illustration only and are not intended to be limiting.
Referring to fig. 1, the ultra-low NOx emission system using the combination of pre-pyrolysis and ammonia injection of the present invention comprises a boiler body 17, a primary air duct 1, a boiler X-layer burner 13, a boiler lower-layer burner 10, a boiler over-fire air nozzle 11, a boiler flue 19, at least one boiler lower-layer burner 10 arranged on the boiler body 17 at a position corresponding to a main combustion zone 16 of a boiler furnace 12, at least one boiler X-layer burner 13 arranged on the boiler body 17 between the main combustion zone 16 corresponding to the boiler furnace 12 and a reduction zone 15 of a high temperature zone, a flue gas temperature control duct plugboard door 2, a boiler X-layer burner duct plugboard door 3, a pulverized coal pre-pyrolysis device input duct plugboard door 4, a pulverized coal pre-pyrolysis device plasma igniter 5, a pulverized coal pre-pyrolysis device 6, a pyrolysis product burner 7, a high-level ammonia injection gun 8, a low-level ammonia injection gun 9, a flue gas recirculation induced draft fan 18 and a high pressure fan 20, on boiler body 17, 15 positions of reduction zone relative to 12 high-temperature regions of boiler furnace 12 set up at least one pyrolysis product combustor 7, on boiler body 17, set up high-temperature ammonia injection zone 14 above 15 positions of reduction zone relative to 12 high-temperature regions of boiler furnace, on boiler body 17, set up a plurality of high-level ammonia injection rifle 8 relative to the upper strata of 12 high-temperature ammonia injection zone 14 positions of boiler furnace, on boiler body 17, set up a plurality of low-level ammonia injection rifle 9 relative to the lower floor of 12 high-temperature ammonia injection zone 14 positions of boiler furnace, set up flue gas recirculation draught fan 18 at the smoke outlet of boiler flue 19, set up high pressure positive blower 20 at the burn-out air spout 11 of boiler body 17, primary air pipeline 1 communicates with boiler flue 19 through flue gas temperature control pipeline inserted plate door 2, flue gas recirculation draught fan 18, primary air pipeline 1 communicates with boiler X layer combustor 13 through boiler X layer combustor pipeline inserted plate door 3, the primary air pipeline 1 is communicated with the air inlet end of a plasma igniter 5 of a pre-pyrolysis device of a pulverized coal pre-pyrolysis device 6 through an insertion plate door 4 of an input pipeline of the pulverized coal pre-pyrolysis device, and the controllable high-temperature outlet end of the pulverized coal pre-pyrolysis device 6 is communicated with a pyrolysis product burner 7.
The invention relates to an ultra-low NOx emission method adopting pre-pyrolysis and ammonia injection, which comprises the following steps:
1) the coal dust pre-pyrolysis device is arranged to ensure that the coal dust can be controllably pre-pyrolyzed at high temperature to realize ultralow NOx emission
The pulverized coal pre-pyrolysis device is adopted, the directional generation of reducing substances in the pulverized coal high-temperature pyrolysis process is controlled, the burnout of solid particles is improved, the generation of thermal nitrogen oxides is inhibited, the NOx in a boiler hearth is deeply reduced by utilizing pyrolysis gas, and the ultralow emission of the NOx under the high burnout condition is realized;
the pulverized coal pre-pyrolysis device introduces a wind and pulverized coal mixture with a specific proportion from a primary air pipeline through a pulverized coal pre-pyrolysis device input pipeline inserting plate door 4, after the ignition of a plasma igniter of the pulverized coal pre-pyrolysis device, controllable high-temperature pre-pyrolysis is carried out in the pulverized coal pre-pyrolysis device, the pre-pyrolysis temperature is 850-1000 ℃, pyrolysis products are conveyed into a hearth to reduce NOx generated by combustion of a main combustion area, a high-pressure fan arranged on an over-fire air nozzle pressurizes to improve the wind speed of SOFA wind (separated over-fire air), at 80-100 m/s, the pyrolysis products are connected with a boiler hearth reduction area, and the NOx reduction efficiency of synthesis gas is 50-85% through controllable high-temperature pre-pyrolysis; a flue gas recirculation induced draft fan arranged at a flue outlet of a boiler flue enables the flow velocity of flue gas to be more than or equal to 36m/s, and can effectively prevent powder accumulation and slag bonding of a pipeline;
2) ultra-low NOx emission by spraying ammonia to high-temperature region of boiler hearth
The method is characterized in that at least one pyrolysis product burner is arranged at a position corresponding to a reduction zone of a high-temperature zone of a boiler furnace, so that the temperature of the high-temperature zone of the boiler furnace is 1200-1400 ℃, a plurality of high-level ammonia spraying guns are arranged at the upper layer of the high-temperature ammonia spraying zone, a plurality of low-level ammonia spraying guns are arranged at the lower layer of the high-temperature ammonia spraying zone, the medium sprayed by the ammonia spraying guns is an amino reducing agent, a urea solution with the concentration of 10% is adopted, a steam channel is arranged in an inner pipe of a spray gun, a urea solution channel is arranged in a middle pipeline, a high-pressure steam channel is arranged in an outer sleeve pipe, the flow range of the urea solution is 0-120L/h, the pressure is 0.4-0.6 MPa, the steam pressure is 0.6-0.8 MPa, the ammonia spraying amount of each spray gun can be adjusted, the adjustment range of the ammonia spraying ratio NSR (the molar ratio of the reducing agent to NOx in the flue gas) value of the urea solution with the concentration of 10% to the ammonia nitrogen oxide in the flue gas is 0-2.5, and the NSR in the operation of the furnace is 1.5-2.0h, NH of urea solution decomposition in pulverized coal flame 3 Mixing with NOx in flue gas to reduce NOx into N 2 。
The pulverized coal pre-pyrolysis device 6 is a controllable high-temperature pulverized coal pre-pyrolysis device, and the boiler X-layer combustor 13 and the pulverized coal pre-pyrolysis device 6 are switched in operation through a boiler X-layer combustor pipeline plugboard door 3 and a pulverized coal pre-pyrolysis device input pipeline plugboard door 4. When the pulverized coal pre-pyrolysis device 6 is shut down, overhauled and the like, the pulverized coal pre-pyrolysis device can be separated from the boiler and put into the X-layer combustor 13 of the boiler to operate, and the load of a unit and the operation of the heat supply working condition cannot be influenced. The boiler lower burner 10 is illustrated for each layer of boiler burners other than the boiler X-layer burner 13, through which fuel, i.e. pulverized coal, is burned into the main combustion zone 16 of the furnace. The upper limit of the installation quantity of the pulverized coal pre-pyrolysis devices 6 is the quantity of the original burners of the layer of the boiler, and the pulverized coal pre-pyrolysis devices can be adjusted according to the combustion state of the boiler. Taking a tangential boiler with four corners as an example, 4 or other numbers of coal dust pre-pyrolysis devices can be installed. The plasma igniter 5 of the pyrolysis device is installed at the top of the pulverized coal preheating and decomposing device 6, the primary air and pulverized coal mixture is conveyed to the pulverized coal preheating and decomposing device 6 to be ignited and combusted, and the pyrolysis temperature is controlled by recycling through adjusting the proportion of the air and the pulverized coal or introducing smoke gas of a boiler flue 19, so that the directional generation of the reducing substances is realized. The proportion of the pulverized coal conveyed to the pulverized coal pre-pyrolysis device can be adjusted according to the content of the reducing substances after pyrolysis, and the optimal configuration of NOx reduction is realized.
In the invention, a plurality of high-level ammonia spraying guns 8 are arranged on the upper layer of the boiler body 17 and the position corresponding to the high-temperature ammonia spraying area 14 of the boiler hearth 12, and a plurality of low-level ammonia spraying guns 9 are arranged on the lower layer of the boiler body 17 and the position corresponding to the high-temperature ammonia spraying area 14 of the boiler hearth 12, which are only schematic arrangements of a plurality of layers of ammonia spraying guns, and the specific arrangement layer number is determined according to the specific condition of the boiler. A plurality of ammonia spraying guns are arranged on each layer. According to the distribution condition of the temperature and the flow field in the boiler, a spray gun is arranged at a proper position in a high-temperature area of the boiler, urea solution with the concentration of 10% of amino reducing agent is sprayed into the area, and the urea solution with the concentration of 10% is prepared by diluting high-concentration urea solution prepared in an SCR denitration system of a power plant, and is a technology familiar to persons skilled in the art. NH of urea solution decomposition in pulverized coal flame 3 Mixing with NOx in flue gas to reduce NOx into N 2 So as to achieve the purpose of reducing NOx. According to the real-time working conditions (such as the amount of smoke and NO) of the boiler X And O 2 Concentration, etc.) to flexibly carry out the operation of the spray gun and the adjustment of the flow control of the urea solution.
The ultra-low NOx emission system adopting the combination of the pre-pyrolysis and the ammonia injection is additionally provided with the combustion control device on the basis of the original boiler system, is parallel to the original combustion control system of the boiler, can be flexibly switched, and does not influence the safe and stable operation of the original boiler system and equipment. The pulverized coal pre-pyrolysis device 6 realizes the switching of feeding air powder into the pulverized coal pre-pyrolysis device 6 or the boiler burner nozzle 10 through the plug board door 2 of the flue gas temperature control pipeline by the primary air pipeline 1, and realizes the reliable shutdown and isolation of the pulverized coal pre-pyrolysis device. And the ammonia injection of the high-temperature ammonia injection zone 14 is stopped and isolated by judging whether the high-level ammonia injection gun 8 and the low-level ammonia injection gun 9 are put into operation or not.
The ultralow NOx emission system adopting the combination of the pre-pyrolysis and the ammonia injection in the embodiment takes a certain 330MW subcritical coal-fired unit boiler as an example, wherein the boiler is arranged in an n-shaped closed single-hearth arrangement, the four corners of the boiler are tangent circles, and the rated power of the turbonator is 300 MW.
Firstly, according to the content of the invention, a pulverized coal pre-pyrolysis device 6 is arranged outside a boiler furnace, four corners of the pulverized coal pre-pyrolysis device are respectively provided with one pulverized coal pre-pyrolysis device, and the pulverized coal pre-pyrolysis device 6 consists of three layers of fireproof and heat-insulating materials and a steel shell from inside to outside. The manufacturing method adopts the prior art. The inlet of the pulverized coal preheating and decomposing device 6 is connected with a pulverized coal pipeline, and the outlet is communicated with a boiler furnace 12. Interface position with the pulverizing system: the inlet powder pipe of the powder pre-pyrolysis device 6 is led from a vertical pipeline in front of the E-layer primary air furnace and is realized by arranging a flue gas temperature control pipeline inserting plate door 2, a boiler E-layer combustor pipeline inserting plate door 3 and a pulverized coal pre-pyrolysis device input pipeline inserting plate door 4. Interface position with boiler furnace 12: the products of the pulverized coal preheating and decomposing device 6 are sprayed into the boiler furnace 12 through the plasma igniter of the pulverized coal preheating and decomposing device, the spraying position is a reducing area between a CCOFA (separated over-fire air) nozzle and a SOFA (separated over-fire air) nozzle, the oxygen content in the area is low, and the preheated and decomposed products can be guaranteed to react with NOx to generate N 2 . Introducing flue gas into a primary air pipeline 1 at the outlet of the coal pulverizer at the E layer and a pulverized coal pipeline at the inlet of a pulverized coal preheating and decomposing device 6, on one hand, controlling the combustion intensity inside a boiler furnace 12, controlling the temperature of the inner wall of the boiler furnace 12 and avoiding over-temperature slag bonding; on the other hand, the wind speed of the primary wind pipeline 1 leading to the E layer of the boiler is improved, and the situation that the primary wind pipeline 1 accumulates coal powder due to the fact that the wind speed is low in low load is avoided.
In a second step, according to the invention, two layers are arranged in the boiler furnace 12The ammonia spraying gun is symmetrically arranged on the upper portion and the lower portion of a nozzle communicated with the pyrolysis product combustor 7, namely, a plurality of high-level ammonia spraying guns 8 are arranged on the upper layer of a boiler body 17 and opposite to the 14 position of the high-temperature ammonia spraying area of the boiler hearth 12, a plurality of low-level ammonia spraying guns 9 are arranged on the lower layer of the boiler body 17 and opposite to the 14 position of the high-temperature ammonia spraying area of the boiler hearth 12, and the ammonia spraying guns adopt anti-oxidation steam atomization ammonia spraying guns. In this example, 16 ammonia spraying guns are provided for each layer, and the total number of the ammonia spraying guns is 32. A urea solution with a concentration of 10% is prepared by diluting water with a urea solution with a concentration of 50% prepared in an SCR denitration system of a factory. During the operation of the boiler, according to the real-time working conditions (such as the flue gas volume, NOX and O) 2 Concentration, etc.) can be flexibly changed to throw the ammonia spraying gun and adjust the flow of the urea solution. NH3 decomposed by the urea solution in the pulverized coal flame is mixed with NOx in the flue gas to reduce the NOx into N 2 。
And thirdly, feeding part of SOFA wind into a primary air pipeline through a configured high-pressure fan 20, wherein the high-pressure fan 20 can increase the SOFA wind speed by pressurization so as to eliminate CO in the flue gas and improve the burnout rate. The high-speed SOFA nozzles are arranged in the upper SOFA nozzles and are embedded with the nozzles, and high-speed SOFA air is connected out of the hot primary air main pipe and enters the high-speed SOFA air pipeline from an opening at the lower part of the original SOFA air nozzles.
Finally, NOx generated by the pulverized coal after combustion in the main combustion area of the boiler is reduced by pyrolyzing the (CH) gas 4 CO, etc.) reduction, NH 3 The two reduction methods are combined to reduce the NOx emission concentration, and the ultra-low NOx emission target of the coal-fired unit without post-treatment measures is achieved.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and improvements can be made without departing from the principle of the present invention, and these should be considered as the protection scope of the present invention.

Claims (2)

1. An ultra-low NOx emission system combining pre-pyrolysis and ammonia spraying comprises a boiler body, a primary air pipeline, a boiler X-layer burner, a boiler lower-layer burner, a boiler over-fire air nozzle and a boiler flue, wherein at least one boiler lower-layer burner is arranged on the boiler body and opposite to the main burning zone of a boiler hearth, and at least one boiler X-layer burner is arranged on the boiler body and between the main burning zone of the boiler hearth and a reduction zone of a high-temperature zone. A high-temperature ammonia spraying area is arranged on the boiler body and above the position of a reduction area corresponding to a high-temperature area of a boiler hearth, a plurality of high-level ammonia spraying guns are arranged on the upper layer of the boiler body and the position corresponding to the high-temperature ammonia spraying area of the boiler hearth, a plurality of low-level ammonia spraying guns are arranged on the lower layer of the boiler body and the position corresponding to the high-temperature ammonia spraying area of the boiler hearth, a smoke recycling induced draft fan is arranged at a smoke outlet of a boiler flue, a high pressure fan is arranged at an overfire air nozzle of a boiler body 17, the primary air pipeline is communicated with the boiler flue through a flue gas temperature control pipeline inserting plate door and a flue gas recirculation induced draft fan, the primary air pipeline is communicated with the boiler X-layer combustor through a pipeline inserting plate door of the boiler X-layer combustor, the primary air pipeline is communicated with the air inlet end of the plasma igniter of the pulverized coal preheating and decomposing device through the inserting plate door of the input pipeline of the pulverized coal preheating and decomposing device, and the controllable high-temperature outlet end of the pulverized coal preheating and decomposing device is communicated with the pyrolysis product burner.
2. A method for ultra-low NOx emission by combining pre-pyrolysis with ammonia injection is characterized by comprising the following steps:
1) the coal powder pre-pyrolysis device is arranged to control the coal powder to be pre-pyrolyzed at high temperature so as to realize the ultralow NOx emission
The pulverized coal pre-pyrolysis device is adopted, the directional generation of reducing substances in the pulverized coal high-temperature pyrolysis process is controlled, the burnout of solid particles is improved, the generation of thermal nitrogen oxides is inhibited, the NOx in a boiler hearth is deeply reduced by utilizing pyrolysis gas, and the ultralow emission of the NOx under the high burnout condition is realized;
the pulverized coal pre-pyrolysis device introduces a mixture of air and pulverized coal in a specific proportion from a primary air pipeline and through a pulverized coal pre-pyrolysis device input pipeline plug board door, after ignition of a plasma igniter of the pulverized coal pre-pyrolysis device, controllable high-temperature pre-pyrolysis is carried out in the pulverized coal pre-pyrolysis device, the pre-pyrolysis temperature is 850-1000 ℃, pyrolysis products are conveyed into a hearth to reduce NOx generated by combustion in a main combustion area, a high-pressure fan arranged on an over-fire air nozzle is pressurized to improve the speed of separated over-fire air, at 80-100 m/s, the pyrolysis products are connected with a boiler hearth reduction area, and the NOx reduction efficiency of synthesis gas is 50-85% through controllable high-temperature pre-pyrolysis; a flue gas recirculation induced draft fan arranged at a flue outlet of a boiler flue enables the flow velocity of flue gas to be more than or equal to 36m/s, and can effectively prevent powder accumulation and slag bonding of a pipeline;
2) ultra-low NOx emission by spraying ammonia to high-temperature region of boiler hearth
At least one pyrolysis product burner is arranged at a position corresponding to a reduction zone of a high-temperature zone of a boiler furnace, so that the temperature of the high-temperature zone of the boiler furnace is 1200-1400 ℃, the method comprises the steps that a plurality of high-position ammonia spraying guns on the upper layer of a high-temperature ammonia spraying area are arranged, a plurality of low-position ammonia spraying guns on the lower layer of the high-temperature ammonia spraying area are arranged, all media sprayed by the ammonia spraying guns are amino reducing agents, a 10% urea solution is adopted, the inner pipe of each spray gun is a steam channel, the middle pipeline is a urea solution channel, the outer sleeve is a high-pressure steam channel, the flow range of the urea solution is 0-120L/h, the pressure is 0.4-0.6 MPa, the steam pressure is 0.6-0.8 MPa, the ammonia spraying amount of each spray gun can be adjusted, the adjustment range of the NSR value of the ammonia nitrogen ratio of the 10% urea solution to nitrogen oxides in smoke is 0-2.5, and NH decomposed by the urea solution in coal powder flame is sprayed within 1.5-2.0h when NSR in the furnace operates. 3 Mixing with NOx in flue gas to reduce NOx into N 2 。
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