CN112484021A - Ultralow-load stable-combustion pre-pyrolysis combustion system and ultralow-load operation method - Google Patents
Ultralow-load stable-combustion pre-pyrolysis combustion system and ultralow-load operation method Download PDFInfo
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- CN112484021A CN112484021A CN202011148540.6A CN202011148540A CN112484021A CN 112484021 A CN112484021 A CN 112484021A CN 202011148540 A CN202011148540 A CN 202011148540A CN 112484021 A CN112484021 A CN 112484021A
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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
- F23C7/00—Combustion apparatus characterised by arrangements for air supply
- F23C7/002—Combustion apparatus characterised by arrangements for air supply the air being submitted to a rotary or spinning motion
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L9/00—Passages or apertures for delivering secondary air for completing combustion of fuel
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N1/00—Regulating fuel supply
- F23N1/04—Regulating fuel supply conjointly with air supply and with draught
- F23N1/042—Regulating fuel supply conjointly with air supply and with draught using electronic means
Abstract
The invention discloses an ultralow-load stable-combustion pre-pyrolysis combustion system and an ultralow-load operation method, wherein the ultralow-load stable-combustion pre-pyrolysis combustion system comprises a coal mill, an air box, a first powder feeding pipeline, a direct-current combustor, a powder feeding pipeline reversing valve, a secondary air adjusting valve, a preheating and de-swirling flow combustor, a boiler hearth, a secondary air pipeline and a main combustor; the central height of the nozzle of the pre-pyrolysis cyclone burner is the same as the height of the nozzle of the direct-current burner on the layer where the nozzle is located; the coal mill is communicated with the direct-current burner and the preheating and de-swirling burner through a first powder feeding pipeline, the preheating and de-swirling burner is installed on the front wall and the rear wall of a boiler hearth, the air box is arranged on the side wall of the boiler hearth, which is adjacent to the side wall where the preheating and de-swirling burner is installed, and the air box is communicated with the direct-current burner and the preheating and de-swirling burner; the pulverized coal can be subjected to low-temperature pyrolysis in the pre-combustion chamber of the preheating and de-swirling flow combustor, the pyrolysis product is mixed with external secondary air and then sprayed into a boiler hearth for stable combustion, the stable operation of the boiler under ultra-low load is ensured, and the requirement of deep peak regulation is met.
Description
Technical Field
The invention belongs to the field of boiler combustion, and particularly relates to an ultralow-load stable-combustion pre-pyrolysis combustion system and an ultralow-load operation method.
Background
With the deterioration of ecological environment, the global carbon dioxide emission reduction pace is accelerated, and the energy structure will be changed. In recent years, new low-carbon energy represented by wind energy and solar energy is rapidly developed, and large-scale wind and light energy sources are connected to the grid, however, the electric power has the characteristics of strong randomness, intermittent energy production and incapability of adjusting according to the requirements of a power grid, and great challenges are generated on the safety and stability of the power grid. According to analysis, after the proportion of wind power and photovoltaic reaches a certain proportion of 15% -20% in a power system, the peak regulation requirement of the power system is qualitatively changed every time the percentage is higher. The operation flexibility of electric power systems in many areas is not enough, and the system needs a large-proportion flexible power supply to improve a peak regulation power supply structure urgently, so that the peak regulation pressure of the system is relieved.
Coal power is the most economical and reliable flexible power supply with the most development potential, and a coal power unit is increasingly used as a peak regulation means for matching with new energy for power generation. At present, peak regulation is mainly based on low-load tracking energy of a coal-electric unit in the low-ebb of a power grid and comprises deep peak regulation and start-stop peak regulation. In order to stimulate the enthusiasm of peak shaving of the coal-electric set, a local electric power peak shaving market is started, the standard of peak shaving compensation is greatly improved, and the quotations are divided into 0-0.4 yuan/kW.h and 0.4-1 yuan/kW.h. And the latest power auxiliary service market operation rule is provided, and the deep peak regulation compensation standard is changed to be consistent with that of northeast, and the maximum value can reach 1 yuan/kW.h.
For the pulverized coal fired boiler of a power station, the minimum oil-free stable combustion load is 30-50% of the rated load generally. The two most commonly used pulverized coal burners of a pulverized coal boiler of a power station are a cyclone burner and a direct-current burner. The cyclone burners are arranged by adopting a front wall or a front wall and a rear wall in opposite direction, and each burner forms an independent flame in a hearth. The swirl burner mixes the primary air and the secondary air earlier than the direct-flow burner, and the mixing is not strong enough in the later period, so that the condition of unstable ignition or difficult burnout is easily caused. In order to achieve good ignition and combustion performance of the burner, a prechamber is often added to the burner. The high-temperature smoke sucked and returned by the precombustion chamber heats the pulverized coal, so that the pulverized coal airflow is stably ignited; the heat released by the combustion of the pulverized coal can also keep the temperature of the precombustion chamber high. Due to the high temperature and small space of the precombustion chamber, the pulverized coal is combusted in the precombustion chamber to generate a large amount of nitrogen oxides, and the conditions of dust deposition and slag bonding are easy to occur.
Application number is CN201720210613.7 discloses a novel low-load surely fires cyclone burner, through the mixing natural gas, with natural gas and air at central tuber pipe back half premix, spout into the precombustion chamber and the burning of peripheral wind powder mixture, realizes the stable burning of buggy. The application number is CN201811552507.2 discloses an adopt swirl pulverized coal burner of flue gas recirculation and precombustion chamber, sets up flue gas recirculation tuber pipe respectively between swirl burner primary air duct and interior secondary air pipe, interior secondary air duct and outer secondary air duct, strengthens furnace's fractional combustion degree, realizes the air fractional combustion. Application number is CN201310049397.9 discloses a power plant boiler burner based on hierarchical precombustion-pyrolysis of buggy, through on original cyclone burner's basis, establishes ties prechamber and pyrolysis chamber, and the high temperature flue gas that the burning of rare buggy entering prechamber produced gets into the pyrolysis chamber, for the pyrolysis of dense buggy provides the heat, under the condition that does not need outer heat source, makes the buggy carry out the pyrolysis. Although the swirl burner is improved at present, pulverized coal still needs to be ignited in the precombustion chamber, the emission of nitrogen oxides is high, long-term use of the burner can cause slag bonding and burning loss in the precombustion chamber, and unstable combustion can occur.
The direct current combustor adopts the four corners arrangement mode, arranges on four angles of furnace, forms the burning of tangent circle. However, the ability to stabilize combustion has been a problem with tangential firing. The boiler with tangential firing at four corners is adopted, pulverized coal airflow must be ignited by tangential fire balls, 4 burners at each layer must be synchronously controlled and synchronously operated or simultaneously closed, and the burners at the four corners cannot independently operate. When the load of the coal-electric machine set is reduced, the conditions of low coal burning quantity in the furnace and low temperature of the hearth can occur, so that the combustion is unstable. Therefore, in order to avoid the situation that the boiler extinguishes fire due to the fact that the temperature of the hearth is too low, the operation load cannot be further reduced, and the deep peak shaving of the boiler is restricted.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides an ultralow-load stable-combustion pre-pyrolysis combustion system and an ultralow-load operation method.
In order to achieve the purpose, the invention adopts the technical scheme that: an ultra-low load stable combustion preheating and de-burning system comprises a coal mill, an air box, a first powder feeding pipeline, a direct-current burner, a powder feeding pipeline reversing valve, a secondary air adjusting valve, a preheating and de-swirling burner, a boiler hearth, a secondary air pipeline and a main burner; each layer of the main burner is provided with a direct-current burner, and the central height of a nozzle of the preheating and de-swirling flow burner is the same as the height of the nozzle of the direct-current burner on the layer where the preheating and de-swirling flow burner is located; the coal mill is communicated with the direct-current burner and the preheating and de-swirling burner through a first powder feeding pipeline, the preheating and de-swirling burner is installed on the front wall and the rear wall of a boiler hearth, the air box is arranged on the side wall of the boiler hearth, which is adjacent to the side wall where the preheating and de-swirling burner is installed, and the air box is communicated with the direct-current burner and the preheating and de-swirling burner; the preheating and de-swirling burner comprises a central pipe, a swirling inner secondary air pipeline, axial blades, an outer secondary air pipeline, a pre-pyrolysis chamber and an outer secondary air nozzle; the second powder feeding pipeline is connected with the central pipe, the cyclone inner secondary air pipeline and the outer secondary air pipeline are coaxially arranged, the outlet of the cyclone inner secondary air pipeline and the outlet of the central pipe are connected with the inlet of the pre-pyrolysis chamber, the outer secondary air nozzle is communicated with the outer secondary air pipeline, and the outer secondary air nozzle is evenly arranged around the pre-pyrolysis chamber.
Axial blades are arranged in the secondary air pipeline in the rotational flow and are arranged along the central pipe in the annular direction.
The pre-pyrolysis chamber is provided with a first section and a second section along the medium flow direction, the cross-sectional areas of the first section and the second section are gradually increased, the areas are linearly increased, and the second section has an outward expansion angle alpha relative to the first section.
The outward expansion angle alpha is 90-135 DEG
The total number of the pre-pyrolysis cyclone burners is four, the pre-pyrolysis cyclone burners are divided into two pairs and are symmetrically distributed on the front wall and the rear wall of a boiler hearth.
A powder feeding pipeline reversing valve is arranged on a pipeline from the first powder feeding pipeline to the direct-current combustor and the preheating and de-swirling combustor, and is provided with a channel A, a channel B and a channel C, wherein the channel A is communicated with the first powder feeding pipeline, the channel B is communicated with a central pipe of the pre-pyrolysis swirling combustor, and the channel C is communicated with the direct-current combustor; and the channel B is communicated with a central pipe of the preheating and de-swirling burner through a second powder feeding pipeline.
The pre-pyrolysis cyclone burner is communicated with the air box through a secondary air pipeline, a secondary air adjusting valve is arranged on the secondary air pipeline, and the secondary air quantity of the pre-pyrolysis cyclone burner is adjusted through the secondary air adjusting valve.
An ultralow load operation method of an ultralow load stable combustion preheating and de-combustion system is characterized in that only a preheating and de-swirl burner is started, a corresponding coal mill is operated, an A channel and a B channel of a powder feeding pipeline reversing valve are opened, a C channel is closed, a secondary air regulating valve is opened, primary air powder is output by the coal mill, the primary air powder sequentially passes through a first powder feeding pipeline, the A channel, the B channel and a second powder feeding pipeline of the powder feeding pipeline reversing valve and then reaches the preheating and de-swirl burner, coal powder is subjected to low-temperature pyrolysis in a pre-combustion chamber, and products of the coal powder are mixed with external secondary air and sprayed into a boiler furnace to be stably combusted.
For the preheating and de-swirling burner, the inner secondary air pipeline and the outer secondary air pipeline of the swirling flow provide auxiliary air, the secondary air regulating valve is opened, and the secondary air pipeline is communicated with the air box, so that the auxiliary air is provided for the preheating and de-swirling burner; the air volume in the secondary air pipeline in the rotational flow accounts for 15-30% of the total volume.
Combustion drying ash-free base volatile component VdafAnthracite or bituminous coal in the range of 6% -35%.
Compared with the prior art, the invention has at least the following beneficial effects:
the ultralow-load stable-combustion preheating and de-swirling burner is combined with the direct-current burner, so that coal powder is preheated and pyrolyzed in the preheating and de-swirling burner, rather than directly combusted, the pyrolysis products are mixed with the external secondary air sprayed from the external secondary air nozzle and sprayed into a boiler hearth for full combustion, low-nitrogen combustion is facilitated, the position of the preheating and de-swirling burner can be flexibly adjusted, and the preheating and de-swirling burner is arranged on the middle upper layer of the main burner, namely any layer of the B-F layers, so that the temperature requirement of the screen superheater is met, and the screen superheater is protected.
Furthermore, the angle of the axial blades can be adjusted through the adjusting piece, the rotational flow strength is changed, the entrainment amount of high-temperature flue gas is increased or reduced, the temperature of the pre-pyrolysis chamber is further controlled, the coal powder is subjected to low-temperature pyrolysis in the pre-pyrolysis chamber, pyrolysis products are mixed with external secondary air sprayed from the external secondary air nozzle, and the mixture is sprayed into a boiler hearth and then stably combusted.
Furthermore, the powder feeding of the direct-current combustor and the preheating and de-swirling flow combustor can be switched through the powder feeding pipeline reversing valve, and stable operation of the boiler under the ultra-low load working condition is further realized.
According to the invention, the preheating and de-swirling burner is arranged in the ultra-low load stable-combustion preheating and de-swirling combustion system, and the preheating and de-swirling burner enables the interior of the preheating and de-swirling chamber to integrally present a reducing atmosphere by adjusting the proportion of secondary air volume and primary air volume in swirling flow, so that the generation of NOx during the pyrolysis of pulverized coal in the high-temperature pre-combustion chamber is inhibited, and the NOx emission can be reduced; after transformation, one preheating and de-swirling burner can stably operate under 30% of design load; when other five layers of burners are closed and only four preheating and de-swirling burners in the tangential swirl coupled burners are operated, the boiler can stably operate at 6-20% of ultralow load, and more benefits can be brought to a power plant.
Furthermore, the suitable types of the fuel can be expanded by adopting the ultra-low load operation method.
Drawings
Fig. 1 is a schematic structural diagram of an ultra-low load stable combustion pre-pyrolysis burner and system design of the invention.
Fig. 2 is a schematic structural diagram of a preheating and de-swirling burner designed for an ultra-low load stable combustion pre-pyrolysis burner and a system of the invention.
FIG. 3 is a schematic view of the burner arrangement of an ultra-low load stable combustion pre-pyrolysis burner and system design of the present invention.
FIG. 4 is a schematic view of the burner nozzle arrangement of the ultra-low load stable combustion pre-pyrolysis burner and the system design of the present invention. In the figure: 1-a coal mill, 2-an air box, 3-a first powder feeding pipeline, 4-a direct current burner, 5-a powder feeding pipeline reversing valve, 6-a secondary air adjusting valve, 7-a preheating and cyclone-decomposing burner, 71-a central pipe, 72-a cyclone inner secondary air pipeline, 73-an axial blade, 74-an outer secondary air pipeline, 75-a pre-pyrolysis chamber, 76-an outer secondary air nozzle, 8-a boiler hearth, 9-a secondary air pipeline, 10-a second powder feeding pipeline, 11-a tangential cyclone coupling burner, 12-a main burner, 121-a burner nozzle, 122-an auxiliary air nozzle, 13-an over-fired air nozzle and 14-a separation air nozzle.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and all other embodiments obtained by a person of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "top", "bottom", "one side", "the other side", "front", "back", "middle part", "inside", "top", "bottom", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention; the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; furthermore, unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, as they may be fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
As shown in fig. 1,2,3, and 4, the present invention provides an ultra-low load stable combustion pre-pyrolysis burner and system design, including a pre-heating de-swirl burner and an ultra-low load stable combustion system;
the pre-pyrolysis cyclone burner 7 comprises a central pipe 71, a cyclone inner secondary air pipeline 72, axial blades 73, an outer secondary air pipeline 74, a pre-pyrolysis chamber 75 and an outer secondary air nozzle 76; the second powder feeding pipeline 10 is connected with a central pipe 71, the cyclone inner secondary air pipeline 72 and the outer secondary air pipeline 74 are coaxially arranged, an outlet of the central pipe 71 is connected with an inlet of the pre-pyrolysis chamber, the axial blades 73 are arranged in the cyclone inner secondary air pipeline 72 and are annularly arranged on the central pipe 71, and the outer secondary air nozzles 76 are communicated with the outer secondary air pipeline 74 and are evenly arranged around the pre-pyrolysis chamber 75.
Referring to fig. 2, the preheating and pyrolysis chamber is provided with a first section and a second section along the medium flow direction, the cross-sectional areas of the first section and the second section are gradually increased, the areas are linearly increased, the second section has an outward expansion angle α relative to the second section, the outward expansion angle α is adjustable within a set range of 90 degrees to 135 degrees, and when coal with poor combustion characteristics is burned, the outward expansion angle of the heat insulation cavity and the angle of the outer secondary air pipe are increased, so that partial heat required by pyrolysis can be provided by partial entrainment of high-temperature flue gas.
The air volume in the cyclone inner secondary air pipeline 72 accounts for 15% -30% of the whole, and the inside of the pre-pyrolysis chamber 75 is integrally made to be in a reducing atmosphere by adjusting the proportion of the secondary air volume to the primary air volume in the cyclone, so that the generation of NOx during the pyrolysis of the pulverized coal in the high-temperature pre-combustion chamber is inhibited, and the NOx emission can be reduced;
the axial blades 73 can uniformly adjust the angles of the axial blades 73 through adjusting parts arranged outside the pipeline, the rotational flow strength is changed, the entrainment amount of high-temperature flue gas is increased or reduced, the temperature of the pre-pyrolysis chamber 75 is controlled, so that the pulverized coal is pyrolyzed at low temperature in the pre-pyrolysis chamber 75, pyrolysis products are mixed with external secondary air sprayed from the external secondary air nozzles 76 and are sprayed into the boiler furnace 8, and then the pulverized coal is stably combusted; after transformation, the single preheating and de-swirling burner 7 can stably operate under 30% of design load.
The ultra-low load stable combustion system comprises a direct-current combustor 4, a preheating and de-swirling flow combustor 7 and a powder feeding system; the once-through burners 4 are symmetrically arranged at four corners of a boiler hearth 8 and are positioned at the same horizontal height, four once-through burners 4 are arranged on each layer, 6 layers are provided, the layers are marked as A, B, C, D, E and F respectively, and each layer of burner is correspondingly communicated with one coal mill 1;
the nozzles of the preheating and de-swirling burners 7 and the nozzles of the direct current burners 4 on the B layer, the C layer, the D layer, the E layer or the F layer are positioned on the same horizontal plane, four nozzles are arranged, divided into two pairs and symmetrically distributed on the front wall and the rear wall of the boiler furnace 8;
the powder feeding system comprises a coal mill 1, an air box 2, a first powder feeding pipeline 3, a powder feeding pipeline reversing valve 5, a secondary air adjusting valve 6, a secondary air pipeline 9 and a second powder feeding pipeline 10, the coal mill 1 is connected with the direct current burner 4 through a first powder feeding pipeline 3, the pre-pyrolysis cyclone burner 7 is connected with the first powder feeding pipeline 3 through a second powder feeding pipeline 10, the connection position is provided with a powder feeding pipeline reversing valve 5, the powder feeding of the burner is switched by the powder feeding pipeline reversing valve 5, the wind boxes 2 are arranged on the side walls at the left side and the right side of a boiler furnace 8, is communicated with the direct current burner 4, the preheating and de-swirling flow burner 7 is communicated with the air box 2 through a secondary air pipeline 9, the secondary air regulating valve 6 is arranged on the secondary air pipeline 9, the supply of the secondary air to the pre-pyrolysis cyclone burner 7 is controlled by opening and closing the secondary air adjusting valve 6.
The preheating de-swirl burners 7 are coupled with the direct current burners 4 at the four corners of the hearth to form tangent swirl coupled burners 11.
The main burner 12 is positioned below the over-fire air nozzle 13, the separation air nozzle 14 is positioned above the over-fire air nozzle 13, and the main burner 12, the over-fire air nozzle 13 and the separation air nozzle 14 are symmetrically distributed on four corners of the boiler furnace 9; a burner nozzle 121 is arranged between two adjacent auxiliary air nozzles 122 on the main burner 12, and the preheating and de-swirling flow burner 7 is arranged on the middle upper layer of the main burner 12, namely any layer of the B-F layers.
The powder feeding pipeline reversing valve 5 is provided with three channels, namely a channel A, a channel B and a channel C, when the channel A and the channel B are opened, primary air powder is output by the coal mill 1 and is conveyed to the preheating and de-swirling burner 7 through the first powder feeding pipeline 3 and the second powder feeding pipeline 10, at the moment, the secondary air regulating valve 6 is opened, secondary air is input to the preheating and de-swirling burner 7, and pulverized coal is sprayed into a boiler hearth 8 after low-temperature pyrolysis is carried out in the preheating and de-swirling chamber 75 and then is stably combusted;
when the channel A and the channel C are opened, primary air powder is output by the coal mill 1 and is conveyed to the direct-current combustor 4 through the first powder feeding pipeline 3, the preheating and de-swirling flow combustor 7 stops running, the secondary air regulating valve 6 is closed, and pulverized coal is sprayed into a boiler hearth 8 from the direct-current combustor 4 to be subjected to tangential firing.
When the boiler runs at full load, five coal mills 1 run, and one coal mill 1 is reserved; when the load of the boiler is reduced, closing the burner layer and the corresponding coal mill 1; the relationship between the boiler load and the number of coal mills 1 operating can be calculated as follows:
D＝n÷5×100％
in the formula, D represents the boiler evaporation rate, n represents the number of coal mills 1 operating, and n is 1,2,3,4, 5.
When the boiler only operates one coal mill 1, only one layer of combustor is started, and the direct-current combustor cannot normally operate; at the moment, the preheating and de-swirling burner 7 is operated, the channel A and the channel B of the powder feeding pipeline reversing valve 5 are opened, the channel C is closed, and the direct current burners 4 at four corners are closed; when the four preheating and de-swirling burners 7 run at full load, the load of the boiler is 1 ÷ 5 × 100% ═ 20%; the improved preheating and de-swirling flow burner 7 can stably operate under 30% of design load, and if the 4 preheating and de-swirling flow burners 7 operate under 30% of load, the load of the boiler can be as low as 30% x 100%, namely 6%.
In the embodiment of the invention, the preheating and de-swirling burner 7 is arranged on the middle upper layer of the main burner, namely any layer from the layer B to the layer F. For convenience of illustration, in the embodiment of the present invention, the preheating and de-swirling burners 7 are all installed in the layer C of the main burner, and in practical applications, the installation positions of the preheating and de-swirling burners 7 can be flexibly adjusted. Considering the temperature requirements of the platen superheater, when the boiler is de-loaded, each layer of burners is closed in turn from the bottommost layer of the boiler furnace 8 upwards.
In the first embodiment, when the 600MW boiler operates under the full-load working condition, five coal mills 1 operate, and one coal mill 1 is reserved. Each coal mill 1 conveys primary air powder to a direct current combustor 4 in a corresponding combustor layer through a first powder feeding pipeline 3, auxiliary air is provided by an air box 2, the primary air powder and the auxiliary air are mixed and injected into a boiler hearth 8 and are directly impacted by high-temperature flame swept by an upstream adjacent angle, the ignition condition is superior, and stable ignition can be realized. For the layer C of the main combustor 12, under the full-load working condition, the four preheating and de-swirling flow combustors 7 are not operated for the moment, and only the four direct-current combustors 4 are operated. And a channel A and a channel C of the powder feeding pipeline reversing valve 5 are opened, a channel B is closed, and the secondary air regulating valve 6 is closed. The primary air powder is output by the coal mill 1, firstly reaches the channel A of the powder feeding pipeline reversing valve 5, and then reaches the four direct current combustors 4 arranged at four corners of the boiler hearth 8 through the channel C of the powder feeding pipeline reversing valve 5, and is jetted into the boiler hearth 8 to be ignited and combusted.
In the second embodiment, when the 600MW boiler operates under the 80% load condition, the burners of the layer A are closed, the corresponding coal mill 1 is stopped, the other four coal mills 1 are operated, and one coal mill 1 is reserved. At this time, the primary air powder and auxiliary air delivery manner of the boiler is completely the same as that of the first embodiment. Each coal mill 1 conveys primary air powder to a direct current combustor 4 in a corresponding combustor layer through a first powder feeding pipeline 3, auxiliary air is provided by an air box 2, and the primary air powder and the auxiliary air are mixed and injected into a boiler hearth 8 and then stably catch fire. The four preheating and de-swirling burners 7 are temporarily not operated, and only the four direct-current burners 4 are operated. A channel A and a channel C of the powder feeding pipeline reversing valve 1 are opened, a channel B is closed, and the secondary air adjusting valve 6 is closed. The primary air powder is output by the coal mill 1, sequentially passes through the channel A and the channel C of the powder feeding pipeline reversing valve 5 through the first powder feeding pipeline 3, then reaches the four direct current combustors 4 in the tangential cyclone coupling combustors 11 arranged at the four corners of the boiler hearth 8, is jetted into the boiler hearth 8, and then is ignited and combusted.
In the third embodiment, when the 600MW boiler operates under the 60% load working condition, the burners of the layer A and the layer B are closed, the corresponding coal mill 1 is stopped, other 3 coal mills 1 are operated, and one coal mill 1 is reserved. At this time, the primary air powder and auxiliary air delivery method of the boiler is completely the same as the first embodiment, and therefore, the description thereof is omitted.
In the fourth embodiment, when the 600MW boiler operates under the working condition of 40% load, the burners of the A layer, the B layer and the D layer at the bottom of the boiler hearth 9 are closed, the corresponding coal mills 1 are stopped, other 2 coal mills 1 are operated, and one coal mill 1 is reserved. At this time, the primary air powder and auxiliary air delivery method of the boiler is completely the same as the first embodiment, and therefore, the description thereof is omitted.
In the fifth embodiment, when the 600MW boiler operates under the working condition below 20% load, the burners of the layer A, the layer B, the layer D and the layer E are closed, the corresponding coal mills 1 are stopped, the preheating and cyclone separating burner 7 of the layer C is started, and the corresponding coal mills 1 are operated, and the coal mills 1 of the layer F are reserved. And (3) closing the four direct-current combustors 4, opening the channel A and the channel B of the powder feeding pipeline reversing valve 1, closing the channel C, and opening the secondary air regulating valve 6. The primary air powder is output by the coal mill 1, sequentially passes through the first powder feeding pipeline 3, the channel A of the powder feeding pipeline reversing valve 5, the channel B and the second powder feeding pipeline 10, and then reaches 4 preheating and de-swirling burners 7 arranged on the front wall and the rear wall of the boiler hearth 8, the preheating and de-swirling burners 7 are supplied with auxiliary air through the swirling inner secondary air pipeline 72 and the outer secondary air pipeline 74, the secondary air regulating valve 6 is opened, and the secondary air pipeline 9 is communicated with the air box 2, so that the auxiliary air is supplied to the preheating and de-swirling burners 7. The coal powder is pyrolyzed at low temperature in the precombustion chamber 75, and the product is mixed with the outer secondary air sprayed from the outer secondary air nozzle 76, sprayed into the boiler furnace 8, and then stably combusted. When the four preheating and de-swirling burners 7 are stably operated at 30% of the design load, the boiler load can be reduced to 6%.
Claims (10)
1. An ultra-low load stable combustion preheating and de-ignition combustion system is characterized by comprising a coal mill (1), an air box (2), a first powder feeding pipeline (3), a direct-current combustor (4), a powder feeding pipeline reversing valve (5), a secondary air adjusting valve (6), a preheating and de-swirl combustor (7), a boiler hearth (8), a secondary air pipeline (9) and a main combustor (12); each layer of the main burner (12) is provided with a direct-current burner (4), and the central height of a nozzle of the preheating and de-swirling flow burner (7) is the same as the height of a nozzle of the direct-current burner (4) on the layer where the preheating and de-swirling flow burner is located; the coal mill (1) is communicated with the direct-current combustor (4) and the preheating and de-swirling combustor (7) through a first powder feeding pipeline (3), the preheating and de-swirling combustor (7) is installed on the front wall and the rear wall of a boiler hearth (8), the wind box (2) is arranged on the side wall of the boiler hearth (8) adjacent to the installation of the preheating and de-swirling combustor (7), and the wind box (2) is communicated with the direct-current combustor (4) and the preheating and de-swirling combustor (7); the pre-pyrolysis cyclone burner (7) comprises a central pipe (71), a cyclone inner secondary air pipeline (72), axial blades (73), an outer secondary air pipeline (74), a pre-pyrolysis chamber (75) and an outer secondary air nozzle (76); the second powder feeding pipeline (10) is connected with the central pipe (71), the cyclone inner secondary air pipeline (72) and the outer secondary air pipeline (74) are coaxially arranged, the outlets of the cyclone inner secondary air pipeline (72) and the central pipe (71) are connected with the inlet of the pre-pyrolysis chamber, the outer secondary air nozzle (76) is communicated with the outer secondary air pipeline (74), and the outer secondary air nozzle are evenly arranged around the pre-pyrolysis chamber (75).
2. The ultra-low load steady combustion pre-pyrolysis combustion system of claim 1, wherein: axial blades (73) are arranged in the secondary air pipeline (72) in the rotational flow and are annularly arranged along the central pipe (71).
3. The ultra-low load steady combustion pre-pyrolysis combustion system of claim 1, wherein: the pre-pyrolysis chamber is provided with a first section and a second section along the medium flow direction, the cross-sectional areas of the first section and the second section are gradually increased, the areas are linearly increased, and the second section has an outward expansion angle alpha relative to the first section.
4. The ultra-low load steady-burning pre-pyrolysis combustion system of claim 3, characterized in that: the outward expansion angle alpha is 90-135 degrees.
5. The ultra-low load steady combustion pre-pyrolysis combustion system of claim 1, wherein: the total number of the pre-pyrolysis cyclone burners (7) is four, the pre-pyrolysis cyclone burners are divided into two pairs, and the two pairs are symmetrically distributed on the front wall and the rear wall of the boiler furnace (8).
6. The ultra-low load steady combustion pre-pyrolysis combustion system of claim 1, wherein: a powder feeding pipeline reversing valve (5) is arranged on the pipeline from the first powder feeding pipeline (3) to the direct-current combustor (4) and the preheating cyclone combustor (7), the powder feeding pipeline reversing valve (5) is provided with a channel A, a channel B and a channel C, wherein the channel A is communicated with the first powder feeding pipeline (3), the channel B is communicated with a central pipe (71) of the preheating cyclone combustor (7), and the channel C is communicated with the direct-current combustor (4); and the channel B is communicated with a central pipe (71) of the preheating and de-swirling burner (7) through a second powder feeding pipeline (10).
7. The ultra-low load steady combustion pre-pyrolysis combustion system of claim 1, wherein: the pre-pyrolysis cyclone burner (7) is communicated with the air box (2) through a secondary air pipeline (9), a secondary air adjusting valve (6) is arranged on the secondary air pipeline (9), and the secondary air quantity of the pre-pyrolysis cyclone burner (7) is adjusted through the secondary air adjusting valve (6).
8. The ultra-low load operation method of the ultra-low load stable combustion pre-pyrolysis combustion system is characterized in that only a pre-pyrolysis cyclone burner (7) is started, a corresponding coal mill (1) is operated, an A channel and a B channel of a powder feeding pipeline reversing valve (5) are opened, a C channel is closed, a secondary air regulating valve (6) is opened, primary air powder is output by the coal mill (1), the primary air powder sequentially passes through a first powder feeding pipeline (3), the A channel of the powder feeding pipeline reversing valve (5), the B channel and a second powder feeding pipeline (10), then reaches the pre-pyrolysis cyclone burner (7), coal powder is subjected to low-temperature pyrolysis in a pre-combustion chamber (75), products of the primary air powder are mixed with external secondary air, and the mixture is sprayed into a boiler hearth (8) for stable combustion.
9. The ultra low load operation method as claimed in claim 8, wherein, for the pre-pyrolysis cyclone burner (7), the inner (72) and outer (74) cyclone secondary air ducts provide the secondary air, the secondary air regulating valve (6) is opened, and the secondary air duct (9) communicates with the windbox (2) to provide the secondary air for the pre-pyrolysis cyclone burner (7); the air volume in the secondary air pipeline (72) in the rotational flow accounts for 15-30% of the total volume.
10. The ultra-low load method of operation of claim 8, wherein the dry ashless based volatiles, V, are burneddafAnthracite or bituminous coal in the range of 6% -35%.
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