WO2014194855A1 - 一种适应于贫煤锅炉的低氮氧化物直流煤粉燃烧装置 - Google Patents

一种适应于贫煤锅炉的低氮氧化物直流煤粉燃烧装置 Download PDF

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Publication number
WO2014194855A1
WO2014194855A1 PCT/CN2014/079349 CN2014079349W WO2014194855A1 WO 2014194855 A1 WO2014194855 A1 WO 2014194855A1 CN 2014079349 W CN2014079349 W CN 2014079349W WO 2014194855 A1 WO2014194855 A1 WO 2014194855A1
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WIPO (PCT)
Prior art keywords
combustion
group
wind
coal
pulverized coal
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PCT/CN2014/079349
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English (en)
French (fr)
Inventor
董信光
郝卫东
胡志宏
董建
刘豪杰
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Electric Power Research Institute of State Grid Shandong Electric Power Co Ltd
State Grid Corp of China SGCC
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Electric Power Research Institute of State Grid Shandong Electric Power Co Ltd
State Grid Corp of China SGCC
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Priority claimed from CN2013203316581U external-priority patent/CN203323116U/zh
Priority claimed from CN201310228682.7A external-priority patent/CN103267279B/zh
Application filed by Electric Power Research Institute of State Grid Shandong Electric Power Co Ltd, State Grid Corp of China SGCC filed Critical Electric Power Research Institute of State Grid Shandong Electric Power Co Ltd
Publication of WO2014194855A1 publication Critical patent/WO2014194855A1/zh
Anticipated expiration legal-status Critical
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Classifications

    • 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
    • F23C5/32—Disposition of burners to obtain rotating flames, i.e. flames moving helically or spirally
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K5/00—Plants characterised by use of means for storing steam in an alkali to increase steam pressure, e.g. of Honigmann or Koenemann type
    • F01K5/02—Plants characterised by use of means for storing steam in an alkali to increase steam pressure, e.g. of Honigmann or Koenemann type used in regenerative installation
    • 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 
    • F23C7/00—Combustion apparatus characterised by arrangements for air supply
    • F23C7/02—Disposition of air supply not passing through burner

Definitions

  • the invention relates to a direct current pulverized coal combustion device, in particular to a low nitrogen oxide direct current coal powder burning device adapted to a lean coal boiler.
  • Nitrogen oxides are pollutants that endanger human health and damage the atmosphere.
  • coal-fired power plants are the most important source of emissions, accounting for 67% of NOx emissions, and will increase with the increase in the capacity of thermal motor assembly machines.
  • NOx pollutants that endanger human health and damage the atmosphere.
  • coal-fired power plants are the most important source of emissions, accounting for 67% of NOx emissions, and will increase with the increase in the capacity of thermal motor assembly machines.
  • the state has successively promulgated more stringent emission standards for thermal pollutants from thermal power plants, and proposed more stringent levels of nitrogen oxides emissions, and no longer have different standards for coal types, that is, whether it is a bituminous coal boiler or a lean coal, or even It is an anthracite boiler that must implement uniform emission standards.
  • the boilers of DC pulverized coal combustion mode account for the majority, and the boiler capacity is mainly 135 liters, 300 liters and 600 liters.
  • the NOx emission concentration of these boilers is relatively high, and the NOx emission concentration of the bituminous coal boiler is 500-800 mg/Nm 3 , which is poor.
  • coal boiler 3 is higher in 650-1100mg / Nm NOx emission concentration of boiler anthracite, nitrogen oxide emissions are much higher than the concentration of these boilers States environmental Protection
  • SCR selective catalytic reduction
  • the low-nitrogen combustion reform of a large number of thermal power units at home and abroad such as #1-#4 boiler of Zouxian Power Plant of Huadian Group, #3, #4 boiler of Zhangqiu Power Plant, #4 and #5 boiler of Laiwu Power Plant of Huaneng Group , Guodian Group's Penglai Power Plant #1 and #2 boilers, Datang Group's Zhangjiakou Power Plant #7 boiler, etc.
  • These boilers are tangentially burning DC pulverized coal boilers. In these transformation cases, the transformation effect is better. It is a bituminous coal or lignite boiler, and the effect of the poor coal-fired boiler is not ideal.
  • the #3 furnace of a Huadian power plant is a sub-critical boiler of lOOOOt/h
  • the coal is lean coal
  • the milling system is a steel ball mill direct blow type.
  • the NOx emission concentration is 534mg/Nm 3
  • the carbon content of the boiler fly ash is 8.8%
  • the boiler efficiency is only 85.5%.
  • coal (deified bituminous high volatile coal) the NOx exhaust concentration will be 410 mg / Nm 3, the Unburned carbon reduced 3 5 O / q;.
  • Some low NOx combustion technology verification is not related to a specific low-NOx combustion, more particularly not designed to accommodate lean coal burners of low nitrogen and low nitrogen how to ensure combustion of the boiler while the high temperature corrosion prevention and the like.
  • the application literature of low-nitrogen burners is as follows: Liu Wen, "Application of Low-nitrogen Combustion Technology in 420t/h Coal-fired Boiler of Wanglong Power Plant", Boiler Manufacturing, 2011, 7 (4) : 26-29 Zhai Qingming, Zhang Bo, Zhu Xianran et al.
  • Patent 89109301 A method and apparatus for reducing the amount of nitrogen oxides produced, the basic principle of which is to reduce the amount of oxygen in the combustion air by introducing flue gas or other reducing gas into the combustion air, thereby reducing The combustion zone generates nitrogen oxides.
  • This method is suitable for small-scale combustion equipment and is not suitable for large-scale power station boilers. Because large-scale boilers require a large amount of air for combustion, the amount of smoke extracted is also very large, which will seriously affect the normal operation of heat exchange equipment behind the extraction point. OK, and the smoke contains a lot of dust and corrosive gas. When extracting the flue gas, it is necessary to consider dust removal and anti-corrosion.
  • the patent claims also mention that the extracted flue gas should be cooled, this part of the heat can not be utilized, and the boiler efficiency is reduced. .
  • Patent 95224587. 6 Burner for strengthening pulverized coal combustion and reducing nitrogen oxides.
  • the effect of the dense phase and the dilute phase produced is not described in the patent, and It is not obvious that the effect of reducing nitrogen oxides is not obvious by the use of low-oxygen combustion. Another point is that this patent has great difficulty in implementation. It is difficult to install the ejector tube with wear resistance and high temperature resistance in one wind vent.
  • Patent 200510047662. 5 An ultra-fine coal powder reburning low-nitrogen oxide combustion technology, this patent principle is to use the re-ignition of ultra-fine coal powder to form a reduction zone, and reduce the NOx generated in the main combustion zone to N 2 . It is mainly carried out in the laboratory. It is difficult to realize for large-scale power station boilers. Firstly, it is difficult to obtain ultra-fine coal powder. Whether it is a new production unit or a modified unit, it is necessary to add a new ultra-fine coal powder preparation device to obtain ultra-fine coal powder.
  • the ultra-fine coal powder preparation device has a higher explosion-proof level and a larger investment in the power plant; another reason requires a special ultra-fine coal powder nozzle, and additional investment is required; this patent only mentions the ultrafine of bituminous coal in the claims.
  • the fineness of pulverized coal is not involved in other coal types.
  • Patent 200610090797. 4 - A low-NOx emission combustion method, the principle is to use the high-temperature oxygen-enriched flue gas of the circulating fluidized bed as the secondary air of the pulverized coal boiler, so that the pulverized coal is burned in a high-temperature and low-oxygen environment. Reduce NOx formation.
  • This method is difficult to implement for a power plant without a circulating fluidized bed boiler. It is difficult to use this method for a power plant with a circulating fluidized bed boiler. The reason is that the large boiler requires a large amount of smoke, and high temperature, smoke is considered. The ash content in the gas is large, and the investment in equipment, design and construction is huge.
  • This method first requires the addition of an oxidant that produces an oxygen concentration of 30%, and requires a power plant to accelerate the oxidant to a certain speed.
  • the equipment is complex and requires explosion-proof measures.
  • This patent also requires adjustment of the jet velocity to reduce The generation of NOx, because each burner must be adjusted at any time, the workload of the operation is large for the operating personnel. Because of the difference in the primary wind speed of each burner, the jet velocity adjustment is designed to be automatically adjusted.
  • Patent 200710071816. 3 A method for the combustion of low nitrogen oxides in a coal-fired boiler. This patent also uses the reburning principle of refined coal powder to reduce the emission of nitrogen oxides, and proposes to refine the finer and finer coal of coal powder. The proportion of powder is larger. The difficulty of implementing this patent is not described in the same way as patent 200510047662.
  • Patent 200810085042. 4 - A method for reducing nitrogen oxides by a pulverized coal boiler using an internal combustion type burner.
  • the principle of this patent is to ignite pulverized coal in a pre-combustion chamber by a plasma igniter or a micro-oil igniter, and then reduce the main The excess air ratio in the combustion zone reduces the generation of NOx.
  • the essence of this method is to reduce the generation of NOx by reducing the amount of oxygen in the main combustion zone.
  • this type of internal combustion burner can be used in boiler ignition. It saves fuel and can stabilize the fuel at low load, but the nozzle is easy to coke and burn. For this type of burner, if the upper part of the furnace is not equipped with a separate burnout air vent, the effect on reducing NOx is not obvious. There are many reducing gases in the water-cooled wall of the main combustion zone, which may cause high temperature corrosion.
  • This patent also easily causes coking and burning of the pulverized coal nozzle, and causes high temperature corrosion on the water-cooled wall surface of the main combustion zone.
  • Patent 200910054141 A low-NOx emission pulverized coal tangential combustion device, the basic principle is that the primary air and the secondary air are arranged at intervals in the main combustion zone, and the exhausted air vent is arranged on the road wall of the upper furnace of the boiler. And the imaginary cut circle that burns the wind has a large diameter.
  • This patent will achieve a better low nitrogen effect on bituminous coal or lignite boilers, but it is not suitable for lean coal with poor ignition characteristics, because the interval between primary and secondary winds will cause low load on lean coal boilers.
  • the combustion is unstable, and the anoxic combustion in the main combustion zone causes high temperature corrosion of the water wall.
  • Patent 201110033811 8 Low NOx emission pulverized coal decoupling burner and pulverized coal decoupling combustion method, this patent introduces a contradiction between the carbon content of fly ash and low nitrogen combustion by a burner separation by two poles.
  • the burners can strengthen the combustion to a certain extent and reduce the generation of NOx in the main combustion zone.
  • this burner is not adjustable and can be easily coked in the nozzle due to the presence of a strong recirculation zone, and this patent does not have Measures to solve the high temperature corrosion of water wall.
  • Patent 20111032443 X multi-coal low-nitrogen DC pulverized coal combustion device, the most important feature of this combustion system is that the secondary air nozzle can swing horizontally and vertically; the separated over-combustion air is divided into two groups with a certain distance.
  • Current DC burner The group is generally designed to be able to remotely control the vertical swing to adjust the reheat steam temperature.
  • This patent designs the secondary air nozzle to be horizontally swingable (manual). Since the momentum of the secondary air is larger than the primary wind, the level is adjusted twice. The air vents regulate the diameter of the combustion tangential circle to achieve combustion of multiple coal types. First of all, this method adapts to the change of the diameter of the burning circle to adapt to the change of the coal type.
  • the range of variation of the coal type is narrow and the inconvenience is realized.
  • the adaptability of the size of the burning circle to the coal type is suitable for each type of coal in each boiler. Different, there is no ready-made experience to make a basis, and it is necessary to constantly explore, and the diameter of the burning and cutting circle is large and stable, but it is easy to cause the burning of the wall and coking. When the burning is small, the stable burning effect is not good at low load. If you use this kind of burner to burn some kind of lean coal, you must first know how much burning and rounding is needed to burn this kind of lean coal. Since there is no basis, you can continue to test to determine the size of the burning circle, but this adjustment method is very good.
  • Patent 201120044217 4 low-nitrogen direct-current combustion device for pulverized coal boiler.
  • This combustion device is mainly to optimize the existing low-nitrogen burner, such as deflecting the secondary air in the middle, and changing the primary air separation nozzle to the adjustable concentrated-light separation burner. These changes are beneficial to reduce NOx formation.
  • the combustion device is suitable for the lean coal boiler. It does not solve the problem of low-load stable combustion and high-temperature corrosion of water-cooled walls.
  • the current low-nitrogen DC pulverized coal burner is more suitable for the ignition characteristics, and the coal with higher volatility such as bituminous coal or lignite will produce more coals with poor fire characteristics such as lean coal.
  • the negative effects are mainly reflected in: (1) The fly ash and slag have higher carbon content, and the boiler economy is reduced. (2) The boiler's low load stability is reduced. (3) Water The wall of the cold wall has a high reducing atmosphere, and the water wall is prone to high temperature corrosion.
  • the object of the present invention is to solve the above problems and provide a low nitrogen oxide direct current pulverized coal combustion device adapted to a lean coal boiler, which can achieve stable economic combustion and can reduce nitrogen oxide emissions to a lower level, so that lean coal
  • the boiler's low-nitrogen combustion retrofit technology has been enhanced.
  • the present invention adopts the following technical solutions:
  • a low nitrogen oxide direct current pulverized coal combustion device adapted to a lean coal boiler, comprising the same structure main body arranged in a four-corner tangential combustion manner at the four corners of the lean coal boiler and cooperating with the water wall anti-high temperature corrosion system of the furnace Burner group; each main burner group includes spaced pulverized coal burners and secondary air nozzles; the upper part of the main burner group is provided with a corresponding separation burnout group; every n-layer pulverized coal burner is provided The layer pre-combustion chamber recirculating burner, the jet direction of the main burner group is counterclockwise, but the direction of the secondary tuyere jet rotating in the upper part of the pre-combustion chamber reflow burner is clockwise, and the imaginary tangential diameter is larger than the main combustion The imaginary tangential diameter of the device is large; the components of the separated burnout wind are the upper group and the lower group, the lower group jet adopts a large imaginary tangential manner, and the upper group adopts a he
  • the top of the main burner group is also provided with a tertiary air vent, the nozzle adopts a large bluff body, the rotation direction of the third air jet is counterclockwise, and the imaginary tangential diameter is larger than the imaginary tangential diameter of the main burner jet in the counterclockwise direction.
  • the pre-chamber reflow burner comprises a pre-combustion chamber, the front end of which is a primary air nozzle, the rear end is a mixing bellows, and the mixing bellows is a wind source of an inner peripheral air outlet of the upper part of the pre-combustion interior wall; for the medium storage type powder-making system
  • the mixed bellows is provided by secondary hot air, tertiary air and natural cold air, and the third wind is from a part of the tertiary air nozzle; for the direct blowing type milling system, the mixed bellows is composed of secondary hot air.
  • the cold secondary air provides a wind source; a wall temperature measuring device is provided on the pre-combustion outdoor wall.
  • the wall temperature measuring device is a sheet-like thermal resistor disposed on the pre-combustion outdoor wall, and the temperature signal collected by the thermal resistor is sent to the control system.
  • the ratio of the height of the pre-chamber to the high temperature of the primary air vent is greater than three.
  • the upper and lower groups of the separated burnout wind group are arranged in a compact manner or separated by a certain distance, wherein the ratio of the lower group of the burnout wind group to the total separated burnout wind volume is less than 50%, and the lower group spout area is burned out than the upper group.
  • the wind vent is large, so as to ensure that the wind speed of the next group is lower than that of the upper group, and the imaginary tangential circle of the lower group is 1.6 times higher than that of the main burner.
  • the wind speed of the wind is higher than the group's burnt wind speed, and the upper group burnout wind is arranged diagonally, that is, the imaginary cut circle diameter of the upper group burnout wind is 0.
  • the water wall anti-high temperature corrosion system comprises an annular bellows, a small wind box, a communication bellows and a ventilation trough, wherein the annular air box sends the hot secondary air of the hot secondary air to the bellows to each small bellows and the coordinating bellows and then to the water cooling.
  • the ventilation groove on the wall fin forms an oxidizing atmosphere on the wall surface of the water wall; the ventilation groove is a strip vent opening on the water wall, and the annular wind box wind is arranged on the connecting pipe of the hot secondary air connection bellows and the annular bellows
  • the pressure control baffle is used to adjust the amount of hot secondary air introduced according to the reducing atmosphere condition of the surface of the water wall.
  • the pulverized coal burner adopts a louver-type concentrated pulverized coal burner, and the difference in density between light and light is within 15%.
  • the width of the stabilizing teeth of the tertiary air nozzle is 1/3 to 1/2 of the height of the tertiary air nozzle.
  • the low-nitrogen oxide direct-flow pulverized coal combustion device adapted to lean coal of the present invention has several key points in design, 1) the pre-combustion chamber size of the pre-combustion chamber return burner and the height of the primary air nozzle, according to the site The location size and the poorer coal's ignition performance are determined to ensure combustion stability. 2), the area of the upper auxiliary air nozzle close to the pre-combustion chamber return burner should be reduced to ensure that the auxiliary air is delayed into the primary air to ensure stable combustion. 3), the next group separates the area of the burnt air vent, the proportion of the air volume, the imaginary tangential diameter and the wind speed are determined according to the coal quality, boiler thermal parameters and fineness of pulverized coal. 4).
  • the relevant parameters of the upper group to separate the burnout wind are determined after comprehensively considering the factors of the steam temperature deviation after determining the relevant parameters of the lower set of burnout winds.
  • 5) Water Wall The location, size and quantity of the annular air duct and ventilation duct in the high temperature corrosion prevention system shall be determined according to the high temperature corrosion situation and the specific structure of the site.
  • the formation and destruction of NOx are mainly related to the following factors: (1) characteristics of coal type; (2) combustion temperature; (3) smoke atmosphere in the reaction zone in the furnace; (4) high temperature of fuel and combustion products in flame The residence time in the area and the furnace.
  • Low NOx combustion technology is to control the above key parameters by changing the combustion conditions to suppress NOx generation or decompose the generated NO x to achieve the purpose of reducing NOx emissions.
  • the low-nitrogen combustion technology applied at home and abroad adopts the combination of low-oxygen combustion method and other methods, mainly adopting rich-light burner (horizontal shading or vertical shading) + offset peripheral wind (or adherent wind) + SOFA (Separated Over Fire air separates the wind.)
  • the principle of the concentrated pulverized coal burner is to use the louver or spiral fins in the nozzle body to separate the pulverized coal airflow into two parts, which are respectively sent into the furnace.
  • the concentration of the dense phase pulverized coal needs less heat, which is good for ignition and stable combustion; Replenishing the air required in the later stage is conducive to the burning of pulverized coal.
  • the NOx emissions of most boilers can be controlled at 300 mg/Nm 3 , and some boilers can be controlled at 200 mg/Nm 3 , but the effect on lean coal boilers is better. Poor, this is because the coal quality characteristics of lean coal are quite different from those of bituminous coal.
  • the main performance is low volatile matter, high fixed carbon and sulfur content, and poor lean coal ignition characteristics and burnout.
  • the thermal parameters of lean coal-fired boilers are relatively high, such as the use of higher volumetric heat load and furnace section thermal strength, and in order to improve the burn-up of lean coal, high oxygen consumption is used.
  • the combustion temperature of the furnace is also high.
  • the present invention adopts a pre-combustion with better stable combustion effect.
  • the chamber return burner is combined with a common rich burner to improve the combustion stability of the main combustion zone and enhance the combustion intensity to achieve an excess air ratio of less than one.
  • the air separation combustion is realized by using the upper and lower sets of different wind rates, different speeds and different imaginary tangential diameters to separate the burnt air.
  • the combustion mode is inevitable. It will cause high temperature corrosion of the boiler water wall. Therefore, the wall-assisted wind with distributed, small wind rate and high wind speed is used to enhance the oxidizing atmosphere of the water wall wall to avoid high temperature corrosion, so that the whole combustion process can be fully optimized, which can achieve stable economy. Combustion also reduces nitrogen oxide emissions to a lower level, which improves the low-nitrogen combustion retrofit technology of lean coal-fired boilers.
  • the excess air ratio is less than 1 and the combustion temperature and strength increase, so that the amount of nitrogen oxides in the main combustion zone is reduced, and the carbon content of the slag and the carbon content of the fly ash are reduced.
  • a pre-combustion chamber reflow burner is used in each n-layer pulverized coal burner in the main combustion zone to improve the combustion intensity and stability of the boiler.
  • the tertiary air vent is fitted with a wider stabilizing body to enhance combustion.
  • the imaginary tangential diameter of the tertiary wind jet is larger than the imaginary tangential diameter of the main burner jet, also for stable combustion.
  • the lower group SOFA wind adopts large imaginary tangential circle, and the nozzle area is increased to reduce the wind speed. It can realize the staged combustion and can make the large coke particles that are blown out by the main air stream to obtain sufficient oxygen to continue burning.
  • the ash combustible content is favorable.
  • the upper group SOFA wind adopts the jet combustion of the jet, and the nozzle area is reduced, the wind speed is increased, and the penetration of the SOFA jet is improved, which is beneficial for reducing the fly ash combustible content.
  • Figure 1 is a schematic view showing the structure of a low-NOx oxide DC pulverized coal burning apparatus for a lean-pulverized boiler of a direct-blowing type pulverizing system.
  • Figure la is a side view of Figure 1.
  • 2 is a schematic view showing the structure of a low-NOx oxide DC pulverized coal combustion apparatus for a lean coal-fired boiler of a medium storage type pulverizing system.
  • Figure 2a is a side view of Figure 2.
  • Figure 3 is a front elevational view showing the structure of the first type of pre-chamber reflow burner.
  • Figure 4 is a front elevational view showing the structure of the second type of pre-chamber reflow burner.
  • Figure 5 is a schematic side view showing the structure of two types of pre-chamber reflow burners.
  • Figure 6 is a schematic view of the arrangement of the anti-high temperature corrosion ventilation slots.
  • Figure 7 is a schematic view of the arrangement of the anti-high temperature corrosion annular bellows.
  • Figure 8 is a schematic diagram of the connection between the anti-high temperature corrosion annular bellows and the small bellows.
  • Fig. 9 is a schematic view showing the flow directions of the jets of the main burner (except the secondary air nozzles of the BC and EF layers).
  • Figure 10 is a schematic view of the flow direction of the secondary air jets of the BC and EF layers.
  • Figure 11 is a schematic view of the flow direction of the next set of SOFA nozzle jets.
  • Figure 12 is a schematic view of the flow direction of the upper SOFA nozzle jet.
  • Figure 13 is a schematic view of the flow direction of the tertiary air jet.
  • A, B, C, D, E, F are pulverized coal burners
  • FF1 and FF2 are secondary air nozzles
  • G is a tertiary air nozzle.
  • S0FA1, S0FA2, S0FA3, S0FA4 are four-layer separated burnout air spouts, 1. Pre-combustion chamber, 2. Secondary hot air control baffle, 3. Secondary cold air control baffle, 4. Mixed bellows, 5.
  • Flaky heat Resistance 6, tertiary air control baffle, 7, primary air spout, 8, temperature display device, 9, built-in peripheral air spout, 10, water wall tube, 11, ventilation trough, 12, annular bellows, 13, annular bellows wind pressure Control baffle, 14, small bellows, 15, contact bellows, 16, hot secondary air contact bellows.
  • boilers that burn lean coal.
  • One is a boiler with a medium-storage milling system.
  • the boiler uses hot air to feed the powder, and the exhaust gas from the powder discharge machine is sent to the furnace as a tertiary air.
  • the pulverizing system With a direct-blowing pulverizing system, the pulverizing system is relatively simple, and there are no tertiary air vents in the burner. Therefore, there are two types of embodiments of the present invention, namely, the boiler of the storage type pulverizing system of Embodiment 1 and the boiler of the direct-blowing type pulverizing system of Embodiment 2. The details will be separately explained based on the drawings.
  • Huadian Group's #3 boiler is a subcritical, intermediate reheating, controlled circulating drum furnace with evaporation of 1025t/h.
  • the combustion method is a four-corner tangential combustion method.
  • the air nozzles are arranged at intervals, and the powder making system is a direct blowing type of double-inlet and double-out steel ball coal mills, and the burning coal type is lean coal.
  • the boiler burner adopts the early American CE technology, and the NOx emission concentration is high, the emission concentration is 750-900mg/N m 3 , and the fly ash carbon content is 5-6%.
  • the #3 boiler was modified for low-nitrogen combustion, and this low-NOx oxide DC pulverized coal combustion device adapted to lean coal was used.
  • a total of 6 layers of pulverized coal burners are respectively A layer, B layer, C layer, D layer, E layer and F layer; the secondary air nozzle is 9 layers respectively
  • the layers are AA layer, AB layer, BC layer, CC layer, DD layer, DE layer, EF layer, FF1 layer and FF2 layer; the separation burnout wind is 4 layers respectively S0FA1, S0FA2, S0FA3, S0FA4.
  • the burners of the A, C, D and F layers are ordinary rich and light burners, there is no special requirement, the ratio of density to light is required to be 2 or more, and the speed difference between the shade and the side is within 15%; B layer and E layer
  • the burner is a pre-chamber reflow burner, and the structure of the pre-chamber reflow burner is shown in Figures 3 and 5.
  • the pre-combustion chamber reflow burner uses the pre-combustion chamber 1 to recirculate the high-temperature flue gas to heat the pulverized coal, improve the combustion intensity, and reduce the carbon content of the fly ash and the slag.
  • the pre-combustion Since the recirculation of the high-temperature flue gas is easy to cause the fire to advance, the pre-combustion is easily caused. Room 1 is coked, the wall temperature of the pre-combustion chamber is raised, and the wall temperature of the pre-combustion chamber is measured by the sheet-shaped thermal resistance 5, and the wall temperature is displayed by the temperature display device 8, in order to reduce the wall temperature of the pre-combustion chamber through the built-in perimeter wind vent 9 to cool, the mixing bellows 4 provides a built-in perimeter wind, and the wind source is provided by the hot secondary air and the cold secondary air. The air temperature in the mixing bellows is controlled by the secondary hot air control baffle 2 and the secondary cold air control baffle 3 To adjust.
  • Figure 6, Figure 7 and Figure 8 show the high temperature corrosion prevention system for water wall.
  • the position of the ventilation groove 11 is determined, and the hot secondary air is taken out from the secondary hot air communication bellows 16 into the annular bellows 12 and then into the small bellows 14
  • the wind pressure of the annular bellows 12 is adjusted and controlled by the annular bellows wind pressure control baffle 13, and the small bellows 14 are connected by the communication bellows 15.
  • Figure 9, Figure 10, Figure 11 and Figure 12 are schematic views of the jet flow direction of each layer of nozzles, showing the diameter of the imaginary circle of the tangential combustion, wherein Figure 9 is AA, A, AB, B, C, CC, DD , D, DE, E, F, FF1 and FF2 jet orifices, the size and direction of the imaginary tangential diameter, Figure 9 shows that the main burner rotates counterclockwise; Figure 10 shows the vents of the BC and EF layers The size and rotation direction of the imaginary tangential diameter of the jet, the figure shows that the two jets rotate in a clockwise direction, and the imaginary tangential diameter is larger than the imaginary tangential diameter of the main burner; Figure 11 is an imaginary of the S0FA1 and S0FA2 jets.
  • Figure 11 shows that the direction of rotation of the S0FA1 and S0FA2 jets is counterclockwise, the imaginary tangential diameter is larger than the imaginary tangential diameter of the main burner;
  • Figure 12 shows the flow direction of the S0FA1 and S0FA2 jets, These two layers are hedged, that is, the imaginary tangential diameter is zero.
  • L1 is pre-combustion chamber reflow.
  • the height of the pre-combustion chamber of the burner, the height of the pre-combustion chamber determines the return flow and the reflow strength of the high-temperature flue gas.
  • L1 is determined according to the worst coal quality, and the L1 is selected as high as possible;
  • L3 is the regenerative combustion of the pre-combustion chamber.
  • the upper air vent of the device, the size of this nozzle is first limited by L1.
  • L3 In order to ensure sufficient combustion intensity of the pre-combustion chamber reflow burner, this layer of secondary air is delayed to be mixed into the pulverized coal gas flow, so L3 should be exhausted.
  • the amount is small;
  • L2 is the distance between the upper and lower two burners. This distance is determined according to the number of pulverized coal burners and the pressure difference between the fire side and the back side.
  • the general principle is that the coal three-layer pulverized coal burners are a group;
  • L4 is the distance between the upper and lower SOFA nozzles. It can be determined according to the actual structural size of the boiler and the required nitrogen oxide emission concentration. It is recommended to be 0-2m ;
  • L5 is the size of the lower SOFA nozzle, and
  • L6 is the size of the upper SOFA nozzle.
  • L5 is larger than L6 to ensure that the wind speed of the next group of SOFA nozzles is higher than that of the upper group SOFA nozzles; the amount of hot air introduced in the high temperature corrosion prevention system is required to be within 3% of the total air volume of the boiler, and the position and number of ventilation holes should be It is determined according to the position where high temperature corrosion is likely to occur and the direction of rotation of the burner jet.
  • Huaneng Group's #3 boiler is a subcritical, intermediate reheating, controlled circulating drum furnace with an evaporation of 1025t/h.
  • the combustion method is a four-corner tangential combustion method.
  • the nozzles are arranged at intervals.
  • the pulverizing system is a storage type pulverizing system in the DTM350/600 steel ball mill.
  • the hot air feeds the powder, and the exhaust gas is sent to the furnace as the tertiary air, and the burning coal is the lean coal in Jinzhong.
  • the boiler has a high NOx emission concentration of 800-950 mg/m 3 and a fly ash content of 3-6%.
  • the #3 boiler was modified for low-nitrogen combustion, and this low-NOx oxide DC pulverized coal combustion device adapted to lean coal was also used.
  • Embodiment 2 is a schematic view showing the structure of the present invention applied to Embodiment 2, wherein a total of 6 layers of pulverized coal burners are respectively A layer, B layer, C layer, D layer, E layer and F layer; secondary air nozzles are 8 layers respectively It is AA layer, AB layer, BC layer, CC layer, DD layer, DE layer, EF layer and FF1 layer; a layer of tertiary air nozzle G layer, peripheral air is arranged around the third air nozzle to cool the nozzle and install the flame-proof teeth Used for stable combustion; the separation of the burnout wind is 4 layers of S0FA1, S0FA2, S0FA3, S0FA4.
  • the burners of the A, C, D and F layers are ordinary concentrated burners, there is no special requirement, the ratio of density to light is required to be 2 or more, and the difference in speed between the shade and the side is within 15%; the B layer and the E layer
  • the burner is a pre-chamber reflow burner, and the structure of the pre-chamber reflow burner is shown in Figures 4 and 5.
  • the pre-combustion chamber reflow burner uses the pre-combustion chamber 1 to recirculate the high-temperature flue gas to heat the pulverized coal, improve the combustion intensity, and reduce the carbon content of the fly ash and the slag.
  • the pre-combustion is easily caused.
  • the chamber 1 is coked, and the wall temperature of the pre-chamber is raised.
  • the wall temperature of the pre-combustion chamber is measured by the sheet-shaped thermal resistor 5, and the wall temperature is displayed by the temperature display device 8, and the wall temperature of the pre-combustion chamber is lowered to pass the built-in peripheral air nozzle.
  • the mixing bellows 4 provides built-in perimeter wind, the wind source is provided by the tertiary air, the hot secondary air and the cold secondary.
  • the air temperature in the mixing bellows is controlled by the secondary hot air baffle 2 and the tertiary wind control block.
  • the plate 6 and the secondary cold air control baffle 3 are adjusted, and the third air is preferentially controlled to control the wind pressure of the bellows, so that the air volume of the G layer of the third air nozzle can be reduced, which is extremely advantageous for reducing the disturbance of the third wind to the combustion of the boiler. .
  • the tertiary air treatment is improper, which has a serious negative impact on the reduction of nitrogen oxides and boiler combustion.
  • the position of the ventilation groove 11 is determined, and the hot secondary air is taken from the secondary hot air communication bellows 15 into the annular bellows 12 and then into the small bellows 14
  • the wind pressure of the annular bellows 12 is adjusted and controlled by the annular bellows wind pressure control baffle 13, and the small bellows 14 are connected by the communication bellows 15.
  • Figure 9, Figure 10, Figure 11, Figure 12 and Figure 13 are schematic views of the jet flow direction of each layer of nozzles, showing the diameter of the imaginary circle of the tangential combustion, wherein Figure 9 is AA, A, AB, B, C, The size and direction of the imaginary tangential diameter of the jets of the CC, DD, D, DE, E, F, FF1 and FF2 jets, Figure 9 shows that the direction of rotation of the main burner is counterclockwise; Figure 10 shows BC and EF The size of the imaginary tangential diameter of the jet of the layer and the direction of rotation, the figure shows that the two jets rotate in a clockwise direction, and the imaginary tangential diameter is larger than the imaginary tangential diameter of the main burner; Figure 11 shows the S0FA1 and S0FA2 layers.
  • FIG. 11 shows that the S0FA1 and S0FA2 jets rotate counterclockwise, and the imaginary tangential diameter is larger than the imaginary tangential diameter of the main burner;
  • Figure 12 shows the S0FA1 and S0FA2 jets.
  • the flow direction indicates that the two layers are counter-combustion, that is, the imaginary tangential diameter is 0;
  • Figure 13 shows that the direction of rotation of the tertiary wind jet is counterclockwise, consistent with the direction of rotation of the main combustion zone, but three times Virtual inscribed circle diameter of the jet than the main jet of the combustion zone of an imaginary inscribed circle diameter is larger.
  • L1, L2, L3 and L4 in Figure 1 need to be determined according to coal quality, boiler structure and test or experience, and L1 is pre-combustion chamber reflow.
  • the height of the pre-combustion chamber of the burner, the height of the pre-combustion chamber determines the return flow and the reflow strength of the high-temperature flue gas.
  • L1 is determined according to the worst coal quality, and the L1 is selected as high as possible;
  • L3 is the regenerative combustion of the pre-combustion chamber.
  • the upper air vent of the device, the size of this nozzle is first limited by L1.
  • this layer of secondary air should be delayed into the pulverized coal gas flow, so L3 should be as small as possible;
  • L2 is the distance between the upper and lower two burners. This distance is determined according to the number of pulverized coal burners and the pressure difference between the fire side and the back side.
  • the general principle is that the coal three-layer pulverized coal burner is a group; The distance between the two sets of SOFA nozzles can be determined according to the actual structural size of the boiler and the required NOx emission concentration. It is recommended to be 0-2m ;
  • L5 is the size of the SOFA nozzle of the lower group, and L6 is the size of the SOFA nozzle of the upper group.
  • the hot air volume introduced in the high temperature corrosion prevention system is required to be within 3% of the total air volume of the boiler, and the position and quantity of the ventilation holes should be based on the location prone to high temperature corrosion.
  • L7 is the width of the steady-burning teeth of the tertiary air nozzle, and the recommended value of L7 is 1/3 to 1/2 of the height of the tertiary air nozzle.
  • the high-temperature corrosion-resistant low-NOx oxide DC pulverized coal combustion device adapted to lean coal has achieved good application results.
  • the NOx emission concentration can be Controlled below 350mg/Nm 3 , the slag and fly ash combustibles of the boiler did not rise significantly, the boiler efficiency was close to the design value, and the boiler's stability was significantly improved.

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Abstract

一种适应于贫煤锅炉的低氮氧化物直流煤粉燃烧装置，包括以四角切圆燃烧方式布置在贫煤锅炉炉膛四角并与炉膛的水冷壁防高温腐蚀系统配合的且结构相同的主燃烧器组；各主燃烧器组则包括间隔设置的煤粉燃烧器和二次风喷口（AA，AB，BC，CC，DD，DE，EF，FF1，FF2）；主燃烧器组上部则设有对应的分离燃尽风组；每隔n层煤粉燃烧器设置一层预燃室回流燃烧器，主燃烧器组的射流旋转方向为逆时针方向，紧邻预燃室回流燃烧器上部的二次风口射流旋转方向为顺时针方向，且假想切圆直径比主燃烧器的假想切圆直径大；分离燃尽风组分为上组和下组，下组射流为大假想切圆，上组为对冲燃烧方式。该燃烧装置可实现稳定燃烧并使氮氧化物的排放降至较低水平。

Description

一种适应于贫煤锅炉的低氮氧化物直流煤粉燃烧装置 技术领域
本发明涉及一种直流煤粉燃烧装置， 尤其涉及一种适应于贫煤锅炉的低氮氧化物直流煤 粉燃烧装置。
背景技术
氮氧化物（NOx)是一种危害人体健康， 破坏大气环境的污染物。 其中燃煤发电厂是最主 要的排放源， 占 NOx排放量的 67%， 而且随着火电机组装机容量增长所占比重会有所提高， 为控制我国燃煤火电厂的 NOx污染物排放水平， 国家相继颁布的更为严格的火电厂大气污染 物排放标准， 提出了更为严格的氮氧化物排放水平， 而且对于煤种不再作不同标准， 也就是 说无论是烟煤锅炉还是贫煤， 甚至是无烟煤锅炉都要执行统一的排放标准， 而我国在 2004年 之前投产的煤粉锅炉采用了国外相对比较落后低氮燃烧技术， 氮氧化物排放浓度较高， 在这 些锅炉中， 采用切圆燃烧的直流煤粉燃烧方式的锅炉占大多数， 锅炉容量以 135丽， 300丽和 600丽为主， 这些锅炉的 NOx排放浓度较高， 其中烟煤锅炉 NOx排放浓度在 500-800mg/Nm3， 贫煤锅炉在 650-1100mg/Nm3， 无烟煤锅炉的 NOx排放浓度更高， 这些锅炉的氮氧化物排放浓 度远高于国家环保部新颁布的 《火电厂大气污染物排放标准》 氮氧化物的排放要求， 为了响 应国家环保标准， 并考虑到技术改造成本和运行成本， 目前火电厂大都采用先把燃烧器改造 为低氮燃烧器， 然后在烟道内采用选择性催化还原法 (SCR)进行烟气脱氮。 目前国内外进行大 量火电机组的低氮燃烧改造如华电集团的邹县电厂的 #1-#4锅炉， 章丘电厂的 #3， #4锅炉， 华能集团的莱芜电厂的 #4和 #5锅炉， 国电集团的蓬莱电厂 #1和 #2锅炉， 大唐集团的张家口 电厂 #7锅炉等等， 这些锅炉都是切圆燃烧的直流煤粉锅炉， 在这些改造案例中， 改造效果较 好的都是烟煤或褐煤锅炉， 贫煤锅炉改造效果均不理想， 如华电某电厂的 #3炉， 为 lOOOt/h 的亚临界锅炉， 燃煤为贫煤， 制粉系统为钢球磨直吹式， 在进行低氮燃烧改造后， 在燃用贫 煤时， NOx的排放浓度为 534mg/Nm3时， 锅炉飞灰含碳量为 8. 8%， 锅炉效率仅为 85. 5%， 在掺 入神化煤 (神化煤为高挥发份烟煤)后， NOx 的排放浓度将为 410 mg/Nm3, 锅炉飞灰含碳量降 为 3. 5O/q; 又如华电集团某电厂 #2炉， 锅炉为 435t/h的超高压锅炉， 燃煤为贫煤， 制粉系统 为钢球磨中储式， 在在进行低氮燃烧改造后， 也出现 NOx排放浓度高， 飞灰含碳量升高， 低 负荷稳燃特性变差， 在 75%BMCR (Boi ler Maximum Continuous Load锅炉最大连续出力）时即 出现几次灭火的情况。 通过全面的调査发现， 目前国内外低氮燃烧改造较为成功的案例都是 在烟煤或褐煤锅炉上进行的， 在贫煤锅炉上还没有比较成功的经验， 这是由于贫煤的煤质特 性与烟煤相比有较大不同， 而且贫煤锅炉在结构设计上也有着较大区别， 因此一些适用于烟 煤锅炉低氮改造经验不能完全适应于贫煤锅炉， 经过对多台进行低氮燃烧改造的贫煤锅炉进 行分析发现， 都存在 NOx排放浓度下降不多， 飞灰含碳量升高导致锅炉经济性降低， 水冷壁 出现高温腐蚀， 低负荷稳燃效果降低的问题。
由于氮氧化物的产生机理和低氮燃烧技术的基本原理的认识目前都已经比较成熟， 通过 文献检索发现， 目前关于低氮燃烧技术方面的文献主要集中在这两个方面， 一方面是基于低 氮燃烧技术原理方面的各种低氮燃烧技术的介绍或数值计算， 如何华庆， 朱跃， 潘志强等， "低 NOx燃烧技术综述"《锅炉制造》 2000 (4) : 34-38； 刘志超. 燃煤锅炉 NOx排放浓度影响 因素的实验和分析 [J] . 电站系统工程， 2005, 21 (5) : 30-34； Vasquez E, Sears R "Combustion control techniques achieve 0. 151b/BBBtu NOx without SCR" 《 Power Engineering)) , 2003, 107 (1) : 39-42； 王春林， 周昊， "基于遗传算法和支持向量机的低 NOx 燃烧优化"《中国电机工程学报》 2007 (11) : 40-44； 宋亚强， "煤粉锅炉低 NOx燃烧技术的数 值试验研究"东南大学硕士论文， 2005; 以上这些文献属于介绍低氮燃烧技术或者采用数值 模拟的方法验证一些低氮燃烧技术没有涉及到某一具体低氮燃烧器， 尤其没有设计到适应于 贫煤的低氮燃烧器以及如何在保证锅炉低氮燃烧的同时防治高温腐蚀等。 另一方面是低氮燃 烧器的应用文献如：刘文， "低氮燃烧技术在旺龙电厂 420t/h燃煤锅炉上的应用"《锅炉制造》， 2011, 7 (4) : 26-29； 禹庆明， 张波， 朱宪然等 "低氮燃烧器改造及运行调整方法探讨"《华北 电力技术》 2012 (7) 35-38; 肖燕华， 陈丰， "低氮燃烧技术在瑞明电厂的实际应用"《能源工 程》 2008 (1) : 55-59 等。 这些文献所描述的成功案例都是在烟煤锅炉上进行的， 在较差着火 性能煤种如贫煤、 无烟煤等基本没有。 聂其红， 孙绍增， 吴少华等， "新型水平浓淡低 NOx煤 粉燃烧器在贫煤锅炉上的应用研究"， 《中国电机工程学报》， 2002, 22 (7) : 155-159, 在这篇 文献介绍了早期的百叶窗型浓淡型低氮燃烧器在 300丽贫煤锅炉上的应用： NOx最低排放浓 度为 631mg/m3， 在煤质稳定的情况下最低不投油稳燃负荷为 140丽， 可以看出这种燃烧器的 稳燃特性较好， 但 NOx排放浓度过高， 已经不符合新的国家环保标准， 而且贫煤锅炉的高温 腐蚀情况比较严重， 文献中也没有明确说明防治高温腐蚀的有效措施。
通过专利检索发现有相关性的专利如下：
专利 89109301. X 降低氮氧化物生成量的燃烧方法及其装置， 这种装置的基本原理是通 过引入烟气或其他还原性的气体混入燃烧用的空气来降低燃烧空气中的氧量， 进而降低燃烧 区域生成氮氧化物。 这种方法适合小型的燃烧装置不适合大型电站锅炉， 因为大型锅炉的燃 烧需要大量空气， 因而抽取的烟气量也非常大， 将严重影响抽取点后面的换热设备的正常运 行， 而且烟气中含有大量灰尘和腐蚀性气体， 在抽取烟气时需要考虑除尘和防腐， 专利权利 要求中还提到抽取的烟气要冷却， 这部分热量不能利用， 又会降低锅炉效率。
专利 95224587. 6 强化煤粉燃烧及降低氮氧化物的燃烧器， 这个专利利用在一次风中加 一高速射流 (速度比 Vl/V2=0-17)产生的引射作用使喷口煤粉产生浓相和稀相， 这个专利由于 引射流可以卷吸高温烟气加强热质和热量的交换， 对于加强煤粉燃烧是有利的， 至于产生的 浓相和稀相的效果在专利中没有说明， 而且仅靠浓淡不采用低氧燃烧， 降低氮氧化物的效果 不会很明显。 还有一点是这个专利在实现起来有较大难度， 在一次风喷口中加装耐磨和耐高 温的引射管难度较大， 还有采用什么介质作为引射流难于选择， 而且引射流难于实现较高的 速度比， 在锅炉正常运行中一次风速在 20-28m/s， 即使是 5倍的速度比， 引射流的流速也要 100-140m/s, 产生这样的引射流在电厂有一定难度， 所以至今在电站锅炉中还没有资料介绍 采用这种技术的燃烧器。
专利 200510047662. 5一种超细化煤粉再燃低氮氧化物燃烧技术，这个专利原理就是利用 超细煤粉的再燃形成还原区域， 将主燃区域生成的 NOx还原成 N2， 这种方法目前主要在实验 室中进行， 对于大型电站锅炉难于实现， 首先是超细化煤粉难于获得， 无论是新投产机组还 是改造机组要获得超细化煤粉必须增设新的超细煤粉制备装置， 而且超细煤粉制备装置的防 爆级别较高， 电厂的投入更大； 再一个原因需要特殊的超细煤粉喷口， 也需要另外的投入； 这个专利在权利要求中仅提到烟煤的超细煤粉细度， 对其他煤种没有涉及。
专利 200610090797. 4 —种低氮氧化物排放的燃烧方法， 其原理是利用循环流化床的高 温富氧烟气作为煤粉锅炉的二次风， 使煤粉在高温低氧的环境中燃烧， 降低 NOx的生成。 这 种方法对于没有循环流化床锅炉的电厂难于实现， 对于有循环流化床锅炉的电厂要采用这种 方法难度相当大， 原因是大型锅炉需要的烟气量大， 而且要考虑高温， 烟气中含灰量大等问 题， 设备、 设计和施工的投入巨大。
专利 200610123491. 4—种氮氧化物排放的富氧燃烧方法，其原理是利用氧气体积浓度小 于 30%的氧化剂与燃料从同轴套管式燃烧喷嘴注入形成引射流， 通过调整燃料和引射流的速 度差来减少 NOx的产生。 这种方法首先要增加产生氧气体积浓度为 30%的氧化剂的设备， 而 且还需有动力设备使氧化剂加速到一定速度， 设备较为复杂并且要有防爆措施； 这个专利还 要求要调整射流速度来减少 NOx的产生， 由于每个燃烧器都要随时调整， 对运行人员来说操 作的工作量较大， 在者由于每个燃烧器的一次风速有差别， 要使射流速度调整设计为自动调 整也较难实现； 还有一点是由于射流和燃烧首先在燃烧室中富氧燃烧， 火焰温度较高， 燃烧 室易结焦。 专利 200620079010. X双分级低氮直流燃烧器，其基本原理将部分一次风分离到二次风喷 口中形成两股煤粉， 达到燃料分级燃烧方式。 煤粉直流燃烧器独立的， 并且是壁面较厚的耐 磨材料， 要将一部分煤粉分到二次风中， 煤粉燃烧器和二次风风道都要产生较大变化， 无论 是设计制造还是施工都难于实现； 还有二次风的风温较高达到 350-400°C并且二次风压也随 时波动， 将煤粉混入后整个热二次风道都有爆炸危险。
专利 200710071816. 3一种用于燃煤锅炉中低氮氧化物燃烧的方法，这个专利也是利用细 化煤粉的再燃原理降低氮氧化物的排放， 提出了细化煤粉更细和细化煤粉的比例更大。 这个 专利的实现难度和专利 200510047662. 5一样不再叙述。
专利 200810085042. 4—种采用内燃式燃烧器的煤粉锅炉降低氮氧化物的方法，这个专利 的原理是通过等离子点火器或微油点火器将煤粉在预燃室内点燃， 然后再通过降低主燃区内 的过量空气系数减少 NOx的生成，这种方法其实质还是通过降低主燃区的氧量来实现减少 NOx 的生成， 在几个电厂应用说明这种内燃式燃烧器在锅炉点火方面可以节省燃油， 并在低负荷 时可以起到稳燃作用， 但喷口易结焦， 烧损， 对于这种燃烧器如果炉膛上部区域不加装分离 燃尽风喷口， 在降低 NOx方面效果不明显， 还有在主燃烧区的水冷壁面还原性气体较多易造 成高温腐蚀。
专利 200810240478. 6和 200820233871. 8低氮燃烧装置及方法， 其原理是采用预燃室式 燃烧器并加装点火装置， 然后再主燃烧区进行缺氧燃烧， 在锅炉上部引入分离燃尽风实现低 氮燃烧。 这个专利的也极易造成煤粉喷口的结焦、 烧损， 并在使主燃区的水冷壁面产生高温 腐蚀。
专利 200910054141. 0一种低氮氧化物排放煤粉切向燃烧装置，其基本原理是在主燃区内 一次风与二次风间隔布置， 在锅炉上部炉膛的路墙上布置燃尽风喷口， 并且燃尽风的假想切 圆直径较大。 这个专利在烟煤或褐煤锅炉上会取得较好的低氮效果， 但不适应于着火特性不 好的贫煤， 由于一次风和二次风的间隔布置对贫煤锅炉来说会造成低负荷时燃烧不稳， 并且 主燃区的缺氧燃烧会使水冷壁产生高温腐蚀。
专利 201110033811. 8 低氮氧化物排放煤粉解耦燃烧器及煤粉解耦燃烧方法， 这个专利 介绍了一种燃烧器通过两极浓淡分离来解决飞灰含碳量和低氮燃烧的矛盾， 这种燃烧器由于 浓淡比较大在一定程度上可以强化燃烧并在主燃区减少 NOx的生成， 但这种燃烧器由于存在 较强的回流区并不可调极易在喷口结焦， 并且这个专利并没有解决水冷壁高温腐蚀的措施。
专利 201110324431. X多煤种低氮直流煤粉燃烧装置， 这个燃烧系统的最主要的特点是 二次风喷口可以水平和垂直摆动； 将分离过燃风分隔为有一定距离的两组。 目前直流燃烧器 组一般都设计成可以远控垂直摆动用来调节再热汽温， 这个专利将二次风喷口设计成可水平 摆动（手动)这样由于二次风的动量比一次风大， 通过水平调节二次风喷口来调节燃烧切圆直 径， 实现多煤种的燃烧。 首先这种方式通过调节燃烧切圆直径来适应煤种变化副作用多、 适 应煤种的变化范围较窄而且实现不方便， 燃烧切圆的大小对煤种的适应性每台锅炉每种煤质 均不同， 没有现成的经验作依据， 要不断地摸索， 而且燃烧切圆直径大稳燃好但易造成贴壁 燃烧而结焦， 燃烧切圆小则低负荷时稳燃效果不好。 假如采用这种燃烧器烧某种贫煤， 首先 要知道烧这种贫煤需要多大的燃烧切圆， 由于没有依据可以需要不断试验才能确定燃烧切圆 的大小， 但这种调节方式实现起来很难， 由于锅炉燃烧器区域空间有限难于实现水平和垂直 均采用执行机构自动摆动， 目前只能采用垂直摆动为自动摆动而水平摆动采用手动调节， 需 要现场进行人工调节二次风的摆角， 改变燃烧切圆直径适应煤种变化， 但根据现场经验全部 二次风喷口调完至少需要三个小时的时间； 还有一个问题是较大的切圆对稳燃有利， 但水冷 壁更容易发生高温腐蚀， 而这个专利并没有涉及防治高温腐蚀的措施。
专利 201120044217. 4煤粉锅炉低氮直流燃烧装置，这个燃烧装置主要是优化了现有的低 氮燃烧器如将中部二次风进行偏转， 将浓淡分离一次风喷口改为可调式浓淡分离燃烧器， 经 过这些改动对降低 NOx的生成有利。 通过对装有偏转二次风的锅炉水冷壁贴壁气氛测量， 偏 转二次风由于比例和强度较小对改变水冷壁贴壁气氛的效果非常有限， 因此这种燃烧装置对 于贫煤锅炉来说， 并没有解决低负荷稳燃和水冷壁高温腐蚀的问题。
在检索过程中还发现一些低氮氧化物旋流燃烧装置如专利 200780017391. 6 —种低氮氧 化物旋流煤粉燃烧器； 201010145738. 9三层二次风低氮氧化物旋流燃烧器； 201120339568. 8 一种旋流燃烧器低氮氧化物低负荷稳燃装置等由于本专利为直流煤粉燃烧装置， 与旋流燃烧 装置没有可比性不做详细分析。
根据以上分析可以发现， 目前的低氮直流煤粉燃烧器较适合着火特性比较好， 挥发份较 高的煤种如烟煤或褐煤， 对于着火特性差的煤种如贫煤等会产生较多的负面影响， 主要表现 在： （1)、 飞灰和炉渣含碳量升高， 锅炉经济性降低。 （2)、 锅炉低负荷稳燃性降低。 （3)、 水 冷壁壁面还原性气氛较高， 水冷壁容易发生高温腐蚀。 这些问题不解决， 在进行贫煤锅炉的 低氮燃烧改造时， 不仅影响锅炉的低氮改造效果而且将严重影响锅炉的安全经济运行。
发明内容
本发明的目的就是为解决上述问题， 提供一种适应于贫煤锅炉的低氮氧化物直流煤粉燃 烧装置， 能实现稳定经济燃烧又能使氮氧化物排放降至较低水平， 使贫煤锅炉的低氮燃烧改 造技术得以提升。 为实现上述目的， 本发明采用如下技术方案：
一种适应于贫煤锅炉的低氮氧化物直流煤粉燃烧装置， 它包括以四角切圆燃烧方式布置 在贫煤锅炉炉膛四角并与炉膛的水冷壁防高温腐蚀系统配合的且结构相同的主燃烧器组； 各 主燃烧器组则包括间隔设置的煤粉燃烧器和二次风喷口； 主燃烧器组上部则设有对应的分离 燃尽风组； 每隔 n层煤粉燃烧器设置一层预燃室回流燃烧器， 主燃烧器组的射流旋转方向为 逆时针方向， 但紧邻预燃室回流燃烧器上部的二次风口射流旋转方向为顺时针方向， 并且假 想切圆直径比主燃烧器的假想切圆直径大； 分离燃尽风组分为上组和下组， 下组射流采用大 假想切圆方式， 上组采用对冲燃烧方式。
所述主燃烧器组的顶部还设有三次风喷口， 喷口采用大钝体， 三次风射流的旋转方向为 逆时针， 假想切圆直径大于主燃烧器射流的逆时针方向的假想切圆直径。
所述预燃室回流燃烧器包括预燃室， 它的前端为一次风喷口， 后端为混合风箱， 混合风 箱是预燃室内壁上部的内周界风喷口的风源； 对于中储式制粉系统来说， 混合风箱的是由二 次热风， 三次风和自然冷风提供风源的， 三次风来自三次风喷口的一部分； 对于直吹式制粉 系统来说， 混合风箱的是由二次热风， 冷二次风提供风源的； 在预燃室外壁设有壁温测量装 置。
所述壁温测量装置是布置在预燃室外壁上的片状热电阻， 由热电阻采集到的温度信号送 至控制系统。
所述预燃室的高度与一次风喷口高温之比大于 3。
所述分离燃尽风组的上下两组紧凑布置或分开一定距离布置， 其中下组分离燃尽风组占 总分离燃尽风风量的比例小于 50%， 下组喷口面积比上组分离燃尽风喷口大， 以保证下组分 离燃尽风的风速小于上组燃尽风风速， 同时下组燃尽风的假想切圆要比主燃烧器的 1. 6倍， 以实现下组分离燃尽风的低风速、 大切圆燃烧方式； 上组分离燃尽风占总分离燃尽风风量的 比例大于 50%， 上组喷口面积小于上组分离燃尽风喷口面积， 以保证上组分离燃尽风的风速 高于小组燃尽风风速， 上组燃尽风采用对角线布置， 即上组燃尽风的假想切圆直径为 0。
所述水冷壁防高温腐蚀系统包括环形风箱、 小风箱、 联络风箱和通风槽， 所述环形风箱 是将热二次风联络风箱的热二次风送至各小风箱和联络风箱然后再送至水冷壁鳍片上的通风 槽， 在水冷壁壁面形成氧化性气氛； 所述通风槽为在水冷壁面上开的条形通风口， 热二次风 联络风箱与环形风箱的连接管道上设有环形风箱风压控制挡板， 用来根据水冷壁表面的还原 性气氛状况来调节引入的热二次风量。
所述煤粉燃烧器采用百叶窗式的浓淡煤粉燃烧器， 浓淡速度差在 15%以内。 所述三次风喷口的稳燃齿的宽度为三次风喷口高度的 1/3〜1/2。
本发明的适应贫煤的防高温腐蚀低氮氧化物直流煤粉燃烧装置在设计时有几个关键点， 1 )、 预燃室回流燃烧器的预燃室尺寸和一次风喷口高度， 根据现场位置尺寸和较差贫煤的着 火性能来定， 以保证燃烧的稳定性。 2)、 紧靠预燃室回流燃烧器的上辅助风喷口面积要减少 以保证辅助风延迟混入一次风保证稳定燃烧。 3)、 下组分离燃尽风喷口面积， 所占风量比例， 假想切圆直径和风速要根据煤质、 锅炉热力参数和煤粉细度决定。 4)、 上组分离燃尽风的相 关参数在确定下组分离燃尽风的相关参数后， 在综合考虑汽温偏差的因素确定。 5)、 水冷壁 高温腐蚀防止系统中环形风道、 通风槽的位置、 尺寸和数量要根据以往发生高温腐蚀情况和 现场具体结构确定。
根据 NOx生成机理， NOx的生成和破坏主要和以下因素有关： （1)煤种特性； （2)燃烧温 度； （3)炉膛内反应区烟气气氛； （4)燃料及燃烧产物在火焰高温区和炉膛内的停留时间。 低 NOx燃烧技术， 就是通过改变燃烧条件来控制上述关键参数， 以抑制 NOx生成或分解已生成 的 N0x， 达到减少 NOx排放的目的。 目前国内外应用的低氮燃烧技术采用低氧燃烧方法和其 他方法相结合的技术， 主要采用浓淡型燃烧器（水平浓淡或垂直浓淡) +偏置周界风（或贴壁 风） + SOFA (Separated Over Fire air分离燃尽风）。 浓淡煤粉燃烧器其原理是利用喷嘴体内 的百叶窗或螺旋鳍片将煤粉气流分成浓淡两股分别送入炉膛，浓相煤粉浓度高所需着火热少， 利于着火和稳燃； 淡相补充后期所需的空气， 利于煤粉的燃尽， 同时浓淡燃烧均偏离了化学 当量燃烧大大降低了 NOx的生成； 偏置周界风或贴壁风的作用主要是防止贴壁燃烧和减轻水 冷壁的避免的还原性气氛； 分离燃尽风 （SOFA) 控制燃烧反应当量， 进一步降低 N0x， 同时 在焦炭燃尽后期补充氧量， 使飞灰中的可燃物含量减少。 这些低氮燃烧技术在烟煤锅炉上取 得比较好的效果，大部分锅炉的 NOx排放能控制在 300mg/Nm3，有些锅炉能控制在 200 mg/Nm3, 但在贫煤锅炉的应用上效果较差， 这是由于贫煤的煤质特性与烟煤的煤质特性相比有着较大 不同， 主要表现为挥发份低， 固定碳和硫含量较高， 使贫煤着火特性和燃尽性比较差； 为了 适应贫煤的煤质特性， 贫煤锅炉的热力参数设计比较高， 如采用较高的容积热负荷和炉膛截 面热强度， 并且为了提高贫煤的燃尽性运行中采用高氧量， 炉膛的燃烧温度也较高， 这些因 素都直接影响了低氮燃烧技术的应用效果， 并产生前述的诸多负面影响， 为了避免这些负面 影响， 本发明采用具有较好稳燃效果较好的预燃室回流燃烧器与普通浓淡燃烧器相结合来提 高主燃烧区域的燃烧稳燃性并加强燃烧强度， 以实现在过量空气系数小于 1的情况下提高主 燃区的燃烧温度， 降低 NOx的生成、减少飞灰和炉渣含碳量； 采用空气分级燃烧方式降低 NOx 排放浓度， 在燃尽区由于燃尽风相对于炉内烟气温度来说是低温空气， 这部分空气的进入会 降低燃尽区域的温度， 但是当这些未燃尽的煤粉颗粒中的焦炭继续燃烧后， 燃尽区域的温度 又会升高，为了尽可能减少负面影响同时提高燃尽区域的焦炭燃尽率采用上下两组不同风率、 不同速和不同假想切圆直径分离燃尽风来实现空气分级燃烧； 由于贫煤含硫量比较高， 同时 在主燃烧区的过量空气系数小于 1这样燃烧方式必然会使锅炉水冷壁发生高温腐蚀， 因此采 用分布式、 小风率、 高风速的墙式辅助风来增强水冷壁壁面的氧化气氛避免高温腐蚀， 这样 整个燃烧过程得以全面优化， 既能实现稳定经济燃烧又能使氮氧化物排放降至较低水平， 使 贫煤锅炉的低氮燃烧改造技术得以提升。
本发明的有益效果是：
1 )在主燃区内， 过量空气系数小于 1的同时燃烧温度和强度增加， 使主燃区内的氮氧化 物的生成量减少， 同时使炉渣含碳量和飞灰含碳量有所降低。
2 )通过不同风率和风速的上下组分离燃尽风既可以降低氮氧化物的生成又可以有效加强 焦炭颗粒燃烧， 减少飞灰含碳量， 在减少汽温偏差也有一定效果。
3 )可以有效地改变水冷壁表面的还原性气氛， 通过对实施例测量， 水冷壁表面的氧量最 小为 0. 5%， 最大为 3%远高于改造前的壁面氧量（改造前壁面氧量： 最大为 0. 7%， 较多的测点 氧量为 0。 )
4)在主燃烧区域每 n层煤粉燃烧器中采用一层预燃室回流燃烧器， 来提高锅炉的燃烧强 度和稳燃性。
5 )预燃室回流燃烧器的上二次风喷口面积减少并且旋转方向反切， 并采用较大的假想切 圆直径， 使二次风混入推迟， 起到稳燃作用。
6 )将部分三次风引入预燃室回流燃烧器的混合风箱用来调温， 减少了三次风的直接送入 风量， 对锅炉燃烧有利。
7 ) 三次风喷口加装较宽的稳燃体， 用来加强燃烧。
8 ) 三次风射流的假想切圆直径大于主燃烧器射流的假想切圆直径， 也是为了稳燃。
9 ) 下组 SOFA风采用大假想切圆， 同时喷口面积加大， 使风速降低， 既能实现分级燃烧 又能使被主气流甩出的大焦炭颗粒得到充分的氧量继续燃烧， 对减少飞灰可燃物含量有利。
10 ) 上组 SOFA风采用射流的对冲燃烧， 同时喷口面积减少， 使风速提高， 提升 SOFA射 流的穿透性， 对减少飞灰可燃物含量有利。
附图说明
图 1为用于直吹式制粉系统贫煤锅炉的低氮氧化物直流煤粉燃烧装置结构示意图。 图 la为图 1的侧视图。 图 2为用于中储式制粉系统贫煤锅炉的低氮氧化物直流煤粉燃烧装置结构示意图。 图 2a为图 2的侧视图。
图 3为第一类预燃室回流燃烧器结构示意图主视图。
图 4为第二类预燃室回流燃烧器结构示意图主视图。
图 5为两类预燃室回流燃烧器结构示意图侧视图。
图 6为防高温腐蚀通风槽布置示意图。
图 7为防高温腐蚀环形风箱布置示意图。
图 8为防高温腐蚀环形风箱与小风箱的连接示意图。
图 9为主燃烧器（除 BC、 EF层二次风喷口）的各喷口射流流向示意图。
图 10为 BC、 EF层二次风喷口射流流向示意图。
图 11为下组 SOFA喷口射流流向示意图。
图 12为上组 SOFA喷口射流流向示意图。
图 13为三次风喷口射流流向示意图。
图中： A、 B、 C、 D、 E、 F为煤粉燃烧器， AA、 AB、 BC、 CC、 DD、 DE、 EF、 FF1禾口 FF2为 二次风喷口， G为三次风喷口， S0FA1、 S0FA2、 S0FA3、 S0FA4为四层分离燃尽风喷口， 1、 预 燃室， 2、 二次热风控制挡板， 3、 二次冷风控制挡板， 4、 混合风箱， 5、 片状热电阻， 6、 三 次风控制挡板， 7、 一次风喷口， 8、 温度显示装置， 9、 内置周界风喷口， 10、 水冷壁管， 11、 通风槽， 12、 环形风箱， 13、 环形风箱风压控制挡板， 14、 小风箱， 15、 联络风箱， 16、 热 二次风联络风箱。
具体实 式
下面结合说明书附图与实施例对本发明的技术方案作进一步的阐述。
燃用贫煤的锅炉目前有两种形式， 一种是采用中储式制粉系统的锅炉， 这种锅炉用热风 送粉， 排粉机的乏气作为三次风送入炉内； 另一种采用直吹式制粉系统， 制粉系统相对简单， 燃烧器中没有三次风喷口。 因此本发明的实施例有两类， 分别为实施例 1 中储式制粉系统的 锅炉和实施例 2直吹式制粉系统的锅炉。 将根据附图分别进行详细阐述。
实施例 1
华电集团某电厂 #3锅炉为蒸发量 1025t/h的亚临界、 中间一次再热、 控制循环汽包炉， 燃烧方式为四角切圆燃烧方式， 每角有六层煤粉燃烧器， 与二次风喷口间隔布置， 制粉系 统为双进双出钢球磨煤机的直吹式， 燃用煤种为贫煤。 该锅炉燃烧器采用了早期美国 CE 的技术， NOx的排放浓度较高， 排放浓度在 750-900mg/N m3， 飞灰含碳量在 5-6%。 为了达 到国家最新的火电厂污染物排放标准， 对 #3锅炉进行了低氮燃烧改造， 采用了这种适应于 贫煤的低氮氧化物直流煤粉燃烧装置。
图 1为本发明应用于实施例 1中的结构示意图， 共有 6层煤粉燃烧器分别为 A层， B层， C层， D层， E层和 F层； 二次风喷口为 9层分别为 AA层， AB层， BC层， CC层， DD层， DE 层， EF层， FF1层和 FF2层; 分离燃尽风为 4层分别为 S0FA1， S0FA2, S0FA3, S0FA4。 在 6 层煤粉燃烧器中， A， C， D和 F层燃烧器为普通浓淡燃烧器， 没有特殊要求， 要求浓淡比在 2 以上， 浓淡侧速度差在 15%以内； B层和 E层燃烧器为预燃室回流燃烧器， 预燃室回流燃烧器 的结构见图 3和图 5。 预燃室回流燃烧器就是利用预燃室 1使高温烟气回流来加热煤粉， 提 高燃烧强度， 减少飞灰和炉渣含碳量， 由于高温烟气的回流易使着火提前， 易造成预燃室 1 结焦， 使预燃室壁温升高， 预燃室的壁温是由片状热电阻 5测量， 通过温度显示装置 8来显 示壁温的， 为了降低预燃室壁温通过内置周界风喷口 9来冷却的， 混合风箱 4提供内置周界 风， 由热二次风和冷二次为混合风箱提供风源， 混合风箱内的风温由二次热风控制挡板 2和 二次冷风控制挡板 3来调节的。
图 6， 图 7和图 8为水冷壁高温腐蚀防止系统。 首先根据切圆燃烧的旋转方向和水冷壁 管 10发生高温腐蚀的位置， 确定通风槽 11的位置， 从二次热风联络风箱 16上引出热二次风 的进入环形风箱 12然后进入各小风箱 14， 环形风箱 12的风压由环形风箱风压控制挡板 13 来调节和控制， 小风箱 14之间通过联络风箱 15连接起来。
图 9， 图 10， 图 11和图 12为各层喷口的射流流向示意图， 表示了切圆燃烧的假想切圆 直径的大小， 其中图 9为 AA、 A、 AB、 B、 C、 CC、 DD、 D、 DE、 E、 F、 FF1和 FF2层喷口射流 的假想切圆直径的大小和旋转方向， 图 9 表明主燃烧器的旋转方向为逆时针方向旋转； 图 10 为 BC和 EF层的喷口射流的假想切圆直径的大小和旋转方向，图表明这两层射流为顺时针 方向旋转， 并且假想切圆直径比主燃烧器的假想切圆直径大； 图 11为 S0FA1和 S0FA2层射流 的假想切圆直径的大小和旋转方向， 图 11表明 S0FA1和 S0FA2层射流的旋转方向为逆时针， 假想切圆直径比主燃烧器的假想切圆直径大； 图 12为 S0FA1和 S0FA2层射流流向表明， 这两 层为对冲燃烧， 也就是说假想切圆直径为 0。
下面结合附图就实施例 1 中的一些关键点进行说明： 在图 1 中几个尺寸 Ll， L2， L3和 L4， 需要根据煤质、 锅炉结构和试验或经验确定， L1为预燃室回流燃烧器的预燃室高度， 预 燃室高度决定了高温烟气的回流量和回流强度， L1要根据最差煤质确定， 在 L1 的选择上尽 量高； L3为紧靠预燃室回流燃烧器的上二次风喷口， 这个喷口尺寸首先受 L1 的限制， 为了 保证预燃室回流燃烧器的有足够的燃烧强度， 这层二次风要延迟混入煤粉气流， 因此 L3要尽 量小； L2为上下两组燃烧器的距离， 这个距离根据煤粉燃烧器的个数以及向火侧和背火侧的 压差确定， 一般原则是煤三层煤粉燃烧器为一组； L4为上下两组 SOFA喷口的距离， 可根据 锅炉的实际结构尺寸和要求的氮氧化物排放浓度确定， 推荐为 0-2m; L5为下组 SOFA喷口的 尺寸， L6为上组 SOFA喷口的尺寸， L5要比 L6大， 以保证下组 SOFA喷口风速要比上组 SOFA 喷口风速高； 防高温腐蚀系统中的引入的热风量要求在锅炉总风量的 3%以内， 通风孔的位置 和数量要根据易发生高温腐蚀的位置和燃烧器射流的旋转方向确定。
实施例 2
华能集团某电厂 #3锅炉为蒸发量 1025t/h的亚临界、 中间一次再热、 控制循环汽包炉， 燃烧方式为四角切圆燃烧方式， 每角有六层煤粉燃烧器， 与辅助风喷口间隔布置， 制粉系 统为 DTM350/600型钢球磨机中储式制粉系统， 热风送粉， 乏气作为三次风送入炉膛， 燃 用煤种为晋中贫煤。 该锅炉 NOx的排放浓度较高， 排放浓度在 800-950mg/m3， 飞灰含碳 量在 3-6%。 为了达到国家最新的火电厂污染物排放标准， 对 #3锅炉进行了低氮燃烧改造， 也采用了这种适应于贫煤的低氮氧化物直流煤粉燃烧装置。
图 2为本发明应用于实施例 2中的结构示意图， 共有 6层煤粉燃烧器分别为 A层， B层， C层， D层， E层和 F层； 二次风喷口为 8层分别为 AA层， AB层， BC层， CC层， DD层， DE 层， EF层和 FF1层； 一层三次风喷口 G层， 在三次风喷口周围设置周界风用来冷却喷口和加 装稳燃齿用来稳燃； 分离燃尽风为 4层分别为 S0FA1， S0FA2 , S0FA3 , S0FA4。 在 6层煤粉燃 烧器中， A， C， D和 F层燃烧器为普通浓淡燃烧器， 没有特殊要求， 要求浓淡比在 2以上， 浓淡侧速度差在 15%以内； B层和 E层燃烧器为预燃室回流燃烧器， 预燃室回流燃烧器的结构 见图 4和图 5。 预燃室回流燃烧器就是利用预燃室 1使高温烟气回流来加热煤粉， 提高燃烧 强度， 减少飞灰和炉渣含碳量， 由于高温烟气的回流易使着火提前， 易造成预燃室 1结焦， 使预燃室壁温升高， 预燃室的壁温是由片状热电阻 5测量， 通过温度显示装置 8来显示壁温 的， 为了降低预燃室壁温通过内置周界风喷口 9来冷却的， 混合风箱 4提供内置周界风， 由 三次风、 热二次风和冷二次为混合风箱提供风源， 混合风箱内的风温由二次热风控制挡板 2、 三次风控制挡板 6和二次冷风控制挡板 3来调节，在控制风箱风温上优先选择三次风来控制， 这样可以减少三次风喷口 G层的风量， 对减少三次风对锅炉燃烧的扰动是极为有利的。 在对 其他贫煤低氮燃烧改造不成功的案例的研究发现， 其中一个重要因素是三次风处理不当， 对 氮氧化物的降低和锅炉燃烧产生了较为严重的负面影响， 在这个实施例中， 除了将部分三次 风作为调温风之外， 在三次风喷口加了较宽的稳燃齿用来加强三次风的稳燃效果， 还有将三 次风射流的假想切圆直径放大来进一步加强燃烧见图 13。 图 6， 图 7和图 8为水冷壁高温腐蚀防止系统。 首先根据切圆燃烧的旋转方向和水冷壁 管 10发生高温腐蚀的位置， 确定通风槽 11的位置， 从二次热风联络风箱 15上引出热二次风 的进入环形风箱 12然后进入各小风箱 14， 环形风箱 12的风压由环形风箱风压控制挡板 13 来调节和控制， 小风箱 14之间通过联络风箱 15连接起来。
图 9， 图 10， 图 11， 图 12和图 13为各层喷口的射流流向示意图， 表示了切圆燃烧的假 想切圆直径的大小， 其中图 9为 AA、 A、 AB、 B、 C、 CC、 DD、 D、 DE、 E、 F、 FFl和 FF2层喷 口射流的假想切圆直径的大小和旋转方向，图 9表明主燃烧器的旋转方向为逆时针方向旋转； 图 10 为 BC和 EF层的喷口射流的假想切圆直径的大小和旋转方向， 图表明这两层射流为顺 时针方向旋转， 并且假想切圆直径比主燃烧器的假想切圆直径大； 图 11为 S0FA1和 S0FA2层 射流的假想切圆直径的大小和旋转方向，图 11表明 S0FA1和 S0FA2层射流的旋转方向为逆时 针， 假想切圆直径比主燃烧器的假想切圆直径大； 图 12为 S0FA1和 S0FA2层射流流向表明， 这两层为对冲燃烧，也就是说假想切圆直径为 0; 图 13表明三次风射流的旋转方向为逆时针， 与主燃烧区域的旋转方向一致， 但三次风射流的假想切圆直径要比主燃烧区域射流的假想切 圆之径要大。
下面结合附图就实施例 2中的一些关键点进行说明： 在图 1 中几个尺寸 Ll， L2， L3和 L4， 需要根据煤质、 锅炉结构和试验或经验确定， L1为预燃室回流燃烧器的预燃室高度， 预 燃室高度决定了高温烟气的回流量和回流强度， L1要根据最差煤质确定， 在 L1 的选择上尽 量高； L3为紧靠预燃室回流燃烧器的上二次风喷口， 这个喷口尺寸首先受 L1 的限制， 为了 保证预燃室回流燃烧器的有足够的燃烧强度， 这层二次风要延迟混入煤粉气流， 因此 L3要尽 量小； L2为上下两组燃烧器的距离， 这个距离根据煤粉燃烧器的个数以及向火侧和背火侧的 压差确定， 一般原则是煤三层煤粉燃烧器为一组； L4为上下两组 SOFA喷口的距离， 可根据 锅炉的实际结构尺寸和要求的氮氧化物排放浓度确定， 推荐为 0-2m; L5为下组 SOFA喷口的 尺寸， L6为上组 SOFA喷口的尺寸， L5要比 L6大， 以保证下组 SOFA喷口风速要比上组 SOFA 喷口风速高； 防高温腐蚀系统中的引入的热风量要求在锅炉总风量的 3%以内， 通风孔的位置 和数量要根据易发生高温腐蚀的位置和燃烧器射流的旋转方向确定； L7为三次风喷口的稳燃 齿的宽度， L7的推荐值为三次风喷口高度的 1/3〜1/2。
在这两个有所区别的实施例中， 适应贫煤的防高温腐蚀低氮氧化物直流煤粉燃烧装置都 取得较好的应用效果， 在煤质接近设计煤质时， NOx的排放浓度能控制在 350mg/Nm3以下， 锅 炉的炉渣和飞灰可燃物没有明显上升， 锅炉效率接近设计值， 同时锅炉稳燃性明显提高。

Claims

权利要求书
1.一种适应于贫煤锅炉的低氮氧化物直流煤粉燃烧装置， 其特征是， 它包括以四角切圆 燃烧方式布置在贫煤锅炉炉膛四角并与炉膛的水冷壁防高温腐蚀系统配合的且结构相同的 主燃烧器组； 各主燃烧器组则包括间隔设置的煤粉燃烧器和二次风喷口； 主燃烧器组上部则 设有对应的分离燃尽风组； 每隔 n层煤粉燃烧器设置一层预燃室回流燃烧器， 主燃烧器组的 射流旋转方向为逆时针方向， 但紧邻预燃室回流燃烧器上部的二次风口射流旋转方向为顺时 针方向， 并且假想切圆直径比主燃烧器的假想切圆直径大； 分离燃尽风组分为上组和下组， 下组射流采用大假想切圆方式， 上组采用对冲燃烧方式。
2.如权利要求 1所述的适应于贫煤锅炉的低氮氧化物直流煤粉燃烧装置， 其特征是， 所 述主燃烧器组的顶部还设有三次风喷口， 喷口采用大钝体， 三次风射流的旋转方向为逆时针， 假想切圆直径大于主燃烧器射流的逆时针方向的假想切圆直径。
3.如权利要求 1或 2所述的适应于贫煤锅炉的低氮氧化物直流煤粉燃烧装置，其特征是， 所述预燃室回流燃烧器包括预燃室， 它的前端为一次风喷口， 后端为混合风箱， 混合风箱是 预燃室内壁上部的内周界风喷口的风源； 对于中储式制粉系统来说， 混合风箱的是由二次热 风， 三次风和自然冷风提供风源的， 三次风来自三次风喷口的一部分； 对于直吹式制粉系统 来说， 混合风箱的是由二次热风， 冷二次风提供风源的； 在预燃室外壁设有壁温测量装置。
4.如权利要求 3所述的适应于贫煤锅炉的低氮氧化物直流煤粉燃烧装置， 其特征是， 所 述壁温测量装置是布置在预燃室外壁上的片状热电阻， 由热电阻采集到的温度信号送至控制 系统。
5.如权利要求 3所述的适应于贫煤锅炉的低氮氧化物直流煤粉燃烧装置， 其特征是， 所 述预燃室的高度与一次风喷口高温之比大于 3。
6.如权利要求 1所述的适应于贫煤锅炉的低氮氧化物直流煤粉燃烧装置， 其特征是， 所 述分离燃尽风组的上下两组紧凑布置或分开一定距离布置， 其中下组分离燃尽风组占总分离 燃尽风风量的比例小于 50%， 下组喷口面积比上组分离燃尽风喷口大， 以保证下组分离燃尽 风的风速小于上组燃尽风风速， 同时下组燃尽风的假想切圆要比主燃烧器的 1. 6倍， 以实现 下组分离燃尽风的低风速、 大切圆燃烧方式； 上组分离燃尽风占总分离燃尽风风量的比例大 于 50%， 上组喷口面积小于上组分离燃尽风喷口面积， 以保证上组分离燃尽风的风速高于小 组燃尽风风速， 上组燃尽风采用对角线布置， 即上组燃尽风的假想切圆直径为 0。
7.如权利要求 1所述的适应于贫煤锅炉的低氮氧化物直流煤粉燃烧装置， 其特征是， 所 述水冷壁防高温腐蚀系统包括环形风箱、 小风箱、 联络风箱和通风槽， 所述环形风箱是将热 二次风联络风箱的热二次风送至各小风箱和联络风箱然后再送至水冷壁鳍片上的通风槽， 在
权利要求书 水冷壁壁面形成氧化性气氛； 所述通风槽为在水冷壁面上开的条形通风口， 热二次风联络风 箱与环形风箱的连接管道上设有环形风箱风压控制挡板， 用来根据水冷壁表面的还原性气氛 状况来调节引入的热二次风量。
8.如权利要求 1所述的适应于贫煤锅炉的低氮氧化物直流煤粉燃烧装置， 其特征是， 所 述煤粉燃烧器采用百叶窗式的浓淡煤粉燃烧器， 浓淡速度差在 15%以内。
9.如权利要求 2所述的适应于贫煤锅炉的低氮氧化物直流煤粉燃烧装置， 其特征是， 所 述三次风喷口的稳燃齿的宽度为三次风喷口高度的 1/3〜 1/2。
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