A coal-fired boiler with main and auxiliary furnaces and ignition method thereof

Abstract

The present invention relates to a coal-fired boiler with a main and auxiliary furnace, comprising a main furnace, an auxiliary furnace and an induced draft system, wherein the main furnace and the auxiliary furnace are respectively arranged in the combustion furnace and separated from each other by an intermediate retaining wall, the main hood and the main air distribution plate are located at the top of the main furnace air chamber, the auxiliary hood and the auxiliary air distribution plate are located at the top of the auxiliary furnace air chamber, the coal material layer for combustion is burned at the top of the main hood and the auxiliary hood respectively, part of the burning coal material in the main furnace passes over the intermediate retaining wall under the action of the wind pressure of the main furnace blower and enters the auxiliary furnace to continue burning, an inner circulation channel connecting the main furnace and the auxiliary furnace is arranged on the intermediate retaining wall, the inner circulation channel opening located on the auxiliary furnace side is higher than the inner circulation channel opening located on the main furnace side, so that the burning coal material in the auxiliary furnace automatically falls into the main furnace through the inner circulation channel and continues to burn. The present invention also discloses an ignition method of the coal-fired boiler. The present invention uses cold slag as bed material and charcoal as an ignition source for ignition, thereby reducing the ignition cost and improving the ignition success rate.

Description

Technical Field

[0001] The invention belongs to the technical field of boiler combustion, and in particular relates to a coal-fired boiler with a main furnace and an auxiliary furnace and an ignition method thereof. Background Art

[0002] The commonly used ignition method of a fluidized bed boiler includes: laying hot slag on the air distribution plate, laying bamboo charcoal on the hot slag, igniting to form a charcoal fire layer, generating a slight negative pressure of -10Pa to 50Pa in the furnace, starting the blower to make the charcoal fire layer jump slightly without being buried by the slag, evenly spreading crushed coal on the charcoal fire layer and gradually increasing the air volume to increase the temperature of the material layer. When the air supply reaches the minimum wind speed during normal operation, the amount of crushed coal sprinkled is used to maintain the material layer temperature increase speed; when the material layer temperature reaches 600℃ to 700℃, increase the amount of crushed coal and the air supply so that the wind speed exceeds the minimum wind speed within 5s; when the material layer temperature reaches 750℃ to 800℃, keep the amount of crushed coal added and the air supply unchanged to make the temperature rise steadily; when the material layer temperature reaches 800℃ to 850℃, start the coal feeder to feed coal normally, keep the air supply unchanged, and adjust the combustion until the flame stabilizes in golden yellow.

[0003] The disadvantages of the existing ignition method of boiling boiler are:

[0004] 1. It is necessary to use hot slag to lay the bottom, which is very difficult for small enterprises with only one boiler. In addition, laying hot slag on the air distribution plate requires manual feeding, which poses a safety hazard.

[0005] 2. The existing coal-fired boilers with main and auxiliary furnaces are characterized by a small main furnace and a large auxiliary furnace. During the main furnace lighting process, problems such as coking and quenching are easily caused by operation. During the auxiliary furnace lighting process, coking is also easily caused by unbalanced air volume control, which affects the overall output of the boiler.

[0006] 3. When the boiler is just started, affected by the boiling degree of the material layer, there is a large deviation between the actual temperature of the material layer and the instrument temperature. For the furnace ignition, there are problems of low-temperature extinction and high-temperature coking. Temperature cannot be used as the only standard for adjusting air supply and coal supply. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a coal-fired boiler with a main and auxiliary furnace and an ignition method thereof, using cold slag as bed material and charcoal as an ignition source to ignite a high and low differential bed boiler, thereby reducing the ignition cost and improving the ignition success rate.

[0008] The present invention is implemented in this way, providing a coal-fired boiler with a main and auxiliary furnace, comprising a main furnace, an auxiliary furnace and an induced draft system, the main furnace comprising a main furnace, a main hood, a main air distribution plate, a main furnace air chamber and a main furnace air blower, the auxiliary furnace comprising an auxiliary furnace, an auxiliary hood, an auxiliary air distribution plate, an auxiliary furnace air chamber and an auxiliary furnace air blower, a combustion furnace surrounded by a furnace wall is arranged in the coal-fired boiler, the main furnace and the auxiliary furnace are respectively arranged in the combustion furnace and are separated from each other by an intermediate retaining wall, the main furnace air chamber is connected to an external main furnace air blower through a main furnace air duct, the main hood and the main air distribution plate are located at the top of the main furnace air chamber, the auxiliary furnace air chamber is connected to an external auxiliary furnace air blower through the auxiliary furnace air duct, and the auxiliary furnace is connected to the auxiliary furnace air chamber through the auxiliary furnace air duct. The hood and auxiliary air distribution plate are located on the top of the auxiliary furnace air chamber, and the coal layers for combustion are burned on the top of the main hood and the auxiliary hood respectively. Under the action of the wind pressure of the main furnace blower, part of the burning coal in the main furnace passes over the middle retaining wall and enters the auxiliary furnace to continue burning. A coal lowering port and a main furnace door are respectively arranged on the furnace wall of the main furnace, and an internal circulation channel connecting the main furnace and the auxiliary furnace is arranged on the middle retaining wall. The opening of the internal circulation channel on the auxiliary furnace side is higher than the opening of the internal circulation channel on the main furnace side, so that the burning coal in the auxiliary furnace automatically falls into the main furnace through the internal circulation channel to continue burning, and an buried pipe containing a heating medium is arranged in the auxiliary furnace.

[0009] Furthermore, the coal-fired boiler also includes a rear flue separator for collecting unburned fine dust particles in the boiler flue gas.

[0010] Furthermore, the main furnace also includes a main furnace lower slag pipe, and the auxiliary furnace includes an auxiliary furnace lower slag pipe, the main furnace lower slag pipe is connected to the main furnace, and the auxiliary furnace lower slag pipe is connected to the auxiliary furnace, and a return port and an auxiliary furnace door are arranged on the furnace wall of the auxiliary furnace.

[0011] Furthermore, the main furnace is located on the left side of the combustion furnace, the auxiliary furnace is located on the right side of the combustion furnace, the coal port is arranged on the furnace wall on the left side of the main furnace, the main furnace door is respectively arranged on the front furnace wall and / or the rear furnace wall of the main furnace, the return port is arranged on the furnace wall on the right side of the auxiliary furnace, and the auxiliary furnace door is respectively arranged on the front furnace wall and / or the rear furnace wall of the auxiliary furnace.

[0012] Furthermore, the return port is arranged at a height higher than the height of the burning coal layer in the auxiliary furnace.

[0013] Furthermore, the setting height of the coal lowering port is higher than the height of the burning coal layer in the main furnace.

[0014] The present invention is implemented by providing an ignition method for a coal-fired boiler with a main furnace and an auxiliary furnace as described above, comprising the following steps:

[0015] Step 1: Lay the bottom material in the main furnace. Evenly lay the cold slag on the main hood at the bottom of the main furnace as the bottom material. The laying thickness is 450mm to 500mm.

[0016] Step 2: Ignite the main furnace, open the main furnace door, close other furnace doors, start the draft system to make the main furnace slightly negative pressure; put matches or charcoal in the main furnace and ignite them with igniters, wait for the firewood to burn into charcoal or the charcoal to burn through, break it up and lay it on the bottom material, repeat this process until the charcoal layer reaches 80mm to 120mm thick;

[0017] Step 3: Start the main furnace blower to make the charcoal fire layer particles slightly jump up and down. When the charcoal fire particles in the furnace decrease and a reddish-red fire wave appears, add fine coal to increase the air flow. As the fine coal ignites and burns, the bottom material below also begins to burn. When the furnace temperature of the main furnace reaches 600℃~700℃, close the main furnace door, start the coal feeder to add fine coal through the coal lowering port, switch to normal operation with 70% of the coal feed, and gradually increase it to normal according to the furnace temperature. Under the air supply of the main furnace blower, part of the burning coal jumping up and down in the main furnace continuously passes over the middle retaining wall into the auxiliary furnace for accumulation and continues to burn. When the furnace temperature of the main furnace rises to above 800℃, the main furnace ignition is completed.

[0018] Step 4: Light the auxiliary furnace. When the main furnace runs stably for 8 hours and the bed material accumulation in the auxiliary furnace has reached the height of the middle retaining wall, start the auxiliary furnace fan, and slowly increase its air volume to normal. The bed material in the auxiliary furnace burns to a fluidized state, and part of the burning coal automatically falls into the main furnace through the internal circulation channel to continue burning. When there is no obvious fluctuation in the air volume of the main furnace and the current of the main furnace fan, it means that the auxiliary furnace is successfully ignited, the main furnace and auxiliary furnace are successfully connected, and the whole ignition process is completed.

[0019] Furthermore, in step one, the cold slag refers to the coal slag discharged from the high and low differential bed boiler and screened, and the proportion of the particle size between 0.1mm and 8mm accounts for more than 85wt% of the total amount, and the maximum particle size does not exceed 10mm.

[0020] Furthermore, in step 2, the thickness of the matches or charcoal is 30 mm to 40 mm.

[0021] Furthermore, in step three, the calorific value of the fine coal is 5000±200KJ / Kg, the proportion of the particle size between 0.1mm and 8mm accounts for more than 80% of the total, the maximum particle size does not exceed 15mm, and the volatile matter is less than 11%.

[0022] Compared with the prior art, the coal-fired boiler with main and auxiliary furnaces and the ignition method thereof of the present invention have the following characteristics:

[0023] 1. Use cold slag as bed material to increase safety;

[0024] 2. Use charcoal as the ignition source to reduce ignition costs;

[0025] 3. Use the color of the flame as the basis for the completion of the furnace lighting stage to improve the success rate;

[0026] 4. Use the same batch of bed materials to conduct the air distribution uniformity test and cold state test to reduce labor;

[0027] 5. The calorific value of the pilot coal only needs to be about 5,000 kcal, which expands the calorific value range of the fuel supply and reduces the ignition cost;

[0028] 6. Use cold slag and crushed carbon to control the drop and rise of furnace temperature during the furnace ignition process to avoid large-scale coking caused by air short circuit and quenching caused by too fast air supply in the furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The figure is a schematic structural diagram of a preferred embodiment of a coal-fired boiler with main and auxiliary furnaces according to the present invention. DETAILED DESCRIPTION

[0030] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] Please refer to Figure 1 As shown, a preferred embodiment of a coal-fired boiler with a main and auxiliary furnace of the present invention comprises a main furnace 1, an auxiliary furnace 2 and an induced draft system (not shown in the figure). The main furnace 1 comprises a main furnace 3, a main air cap 4, a main air distribution plate 5, a main furnace air chamber 6, a main furnace air blower 7 and a main furnace lower slag pipe 8, and the auxiliary furnace 2 comprises an auxiliary furnace 9, an auxiliary air cap 10, an auxiliary air distribution plate 11, an auxiliary furnace air chamber 12, an auxiliary furnace air blower 13 and an auxiliary furnace lower slag pipe 14. The arrows in the figure show the flow direction of the burning coal.

[0032] A combustion furnace 16 surrounded by a furnace wall 15 is provided in the coal-fired boiler, and the main furnace 3 and the auxiliary furnace 9 are respectively provided in the combustion furnace 16 and separated from each other by an intermediate retaining wall 17. The main furnace air chamber 6 is connected to the external main furnace blower 7 through the main furnace air duct 18, and the main air cap 4 and the main air distribution plate 5 are located at the top of the main furnace air chamber 6. The auxiliary furnace air chamber 12 is connected to the external auxiliary furnace blower 13 through the auxiliary furnace air duct 19, and the auxiliary air cap 10 and the auxiliary air distribution plate 11 are located at the top of the auxiliary furnace air chamber 12. The coal material layer A for combustion is burned at the top of the main air cap 4 and the auxiliary air cap 10 respectively.

[0033] Part of the burning coal in the main furnace 3 passes over the intermediate retaining wall 17 and enters the auxiliary furnace 9 to continue burning under the action of the wind pressure of the main furnace blower 7. A coal lowering port 20 and a main furnace door 21 are respectively arranged on the furnace wall 15 of the main furnace 3, and an inner circulation channel 22 connecting the main furnace 3 and the auxiliary furnace 9 is arranged on the intermediate retaining wall 17. The inner circulation channel opening on the auxiliary furnace 9 side is higher than the inner circulation channel opening on the main furnace 3 side, so that the burning coal in the auxiliary furnace 9 automatically falls into the main furnace 3 through the inner circulation channel 22 to continue burning.

[0034] The buried pipe 23 containing the heating medium is arranged in the auxiliary furnace 9. The coal-fired boiler heats the medium in the buried pipe 23.

[0035] The finer particles in the burning coal in the main furnace 3 pass over the middle retaining wall 17 and enter the auxiliary furnace 9 for accumulation under the action of the wind pressure of the main furnace blower 7, and heat the working medium in the buried pipe 23. After the bed material in the auxiliary furnace 9 reaches a fluidized state under the action of the auxiliary furnace blower 13, it will automatically fall into the main furnace 3 through the internal circulation channel 22 and then be fully burned. The burning coal completes an internal circulation in the combustion furnace 16.

[0036] The main furnace lower slag pipe 8 is connected to the main furnace 3, and the auxiliary furnace lower slag pipe 14 is connected to the auxiliary furnace 9. A return port 24 and an auxiliary furnace door 25 are provided on the furnace wall 15 of the auxiliary furnace 9. The main furnace lower slag pipe 8 is used to discharge the coal slag burned in the main furnace 3, and the auxiliary furnace lower slag pipe 14 is used to discharge the coal slag burned in the auxiliary furnace 9.

[0037] The coal-fired boiler further includes a rear flue separator 26 for collecting unburned fine dust particles in the boiler flue gas. The fine dust particles collected by the rear flue separator 26 enter the auxiliary furnace 9 through the return port 24 for further combustion and utilization. This process belongs to the external circulation of the combustion coal particles, so that the coal is fully utilized and coal resources are further saved.

[0038] like Figure 1 As shown, in this embodiment, the main furnace 3 is located on the left side of the combustion furnace 16, the auxiliary furnace 9 is located on the right side of the combustion furnace 16, the coal port 20 is arranged on the furnace wall 15 on the left side of the main furnace 3, the main furnace door 21 is respectively arranged on the front furnace wall and / or the rear furnace wall of the main furnace 3, the return port 24 is arranged on the furnace wall 15 on the right side of the auxiliary furnace 9, and the auxiliary furnace door 25 is respectively arranged on the front furnace wall and / or the rear furnace wall of the auxiliary furnace 9.

[0039] Specifically, the setting height of the return opening 24 is higher than the height of the burning coal material layer A in the auxiliary furnace 9. The setting height of the lower coal opening 20 is higher than the height of the burning coal material layer A in the main furnace 3.

[0040] The present invention also discloses an ignition method for a coal-fired boiler with a main furnace and an auxiliary furnace as described above, comprising the following steps:

[0041] Step 1: Lay the bottom material in the main furnace 3. Evenly lay the cold slag on the main hood 4 at the bottom of the main furnace 3 as the bottom material, with a laying thickness of 450mm to 500mm.

[0042] When laying the base material, all iron objects and debris between the main air hoods 4 are removed to avoid blockage of the main air hoods 4 and cause imbalance of the local fluidization state.

[0043] Among them, cold slag refers to the coal slag discharged from the high and low differential bed boiler and screened, the proportion of particle size between 0.1mm and 8mm accounts for more than 85wt% of the total, and the maximum particle size does not exceed 10mm.

[0044] The main furnace blower 7 is turned on to conduct the air distribution uniformity test and the cold state test and then turned off. The boiling uniformity of the cold slag bottom material in each part of the main furnace 3 is checked by increasing the air supply of the main furnace blower 7 to eliminate the boiling dead zone. The cold boiling critical air volume is determined by reducing the air supply of the main furnace blower 7 to estimate the minimum air volume during hot operation to avoid excessive air volume during hot operation, which may cause the cold slag to cover the red carbon and cause extinguishing.

[0045] Step 2: Ignite the main furnace 3, open the main furnace door 21, close other furnace doors, start the induced draft system to ventilate the coal-fired boiler for 4 to 5 minutes, so that the main furnace 3 is in a state of slight negative pressure. Put matches or charcoal in the main furnace 3 and ignite them with igniters. After the firewood is burned into charcoal or the charcoal is burned through, break it and lay it on the bottom material, and repeat this process until the charcoal layer reaches 80mm to 120mm thick. Wait for 15 to 25 minutes to let the charcoal turn red. The thickness of the matches or charcoal is 30mm to 40mm.

[0046] When igniting, the charcoal fire is controlled by adjusting the opening of the main furnace door 21. After the firewood is burned into charcoal fire or the charcoal is burned through, the larger red charcoal is broken up with a rake, and the charcoal that is not burned through should be cleared out of the main furnace.

[0047] Step 3, the main furnace blower 7 is started, and a slight amount of wind is supplied according to the cold test result of step 1, so that the charcoal fire layer particles slightly jump up and down. When the charcoal fire particles in the furnace decrease and a reddish-brown fire wave appears, fine coal is added to increase the wind. However, since the furnace temperature is not high at this time, the wind volume should not be too large, which can only make the ash particles jump up and down, but not tumble. In the early stage of ignition, it is easy to drown the charcoal fire or the ignited coal particles, causing them to go out. Therefore, carefully observe the movement state of the charge. Sometimes there are too many combustible fine particles in the bottom material, which ignites quickly and releases a lot of heat in the furnace. At a lower wind speed, they boil and burn, causing deflagration. The temperature rises too quickly. Sometimes the air volume is too large, which will instantly fly out of the furnace in large quantities of the burning fine particles and the heat in the furnace, and the burning coarse coal particles that have not flown away are covered by the bottom material. If no measures are taken at this time, the flames will disappear in a blink of an eye, and the temperature will drop sharply or even go out. On the contrary, if the air volume of the main furnace is too small, floating coke will form on the surface of the bed material, affecting the continuation of the material layer quality exchange process. When "flowers" or "shooting stars" appear in the furnace, it is often a symbol of coking. The coke should be removed with a rake in time, and the opening of the furnace door should be adjusted. When the furnace temperature rises slowly, wind and coal can be added continuously. In the case of uneven temperature of the material layer, manual stirring can be used. As the fine coal ignites and burns, the flame waves jump higher and higher, which shows that the mass exchange of the boiling coal gradually extends downward. Due to the strong heat exchange brought about by the mass exchange of the upper and lower hot materials, the lower bottom material also begins to burn.

[0048] The calorific value of fine coal is 5000±200KJ / Kg, the proportion of particle size between 0.1mm and 8mm accounts for more than 80% of the total, the maximum particle size does not exceed 15mm, and the volatile matter is less than 11%.

[0049] When the furnace temperature of the main furnace 3 reaches 400℃~500℃, the flame changes from dark red to apricot yellow, and fine coal and air are added. At this time, the fine coal put in will quickly ignite and burn, and the furnace temperature will also rise rapidly.

[0050] When the furnace temperature of the main furnace 3 reaches 600℃~700℃, the flame becomes brighter and brighter, and the material layer is apricot yellow everywhere. The fluidization state of the coal reaches more than 2 / 3 (the upper material layer of 300mm has completed fluidization), and the fluidization state further expands downward, and the mass exchange between the upper and lower layers is further strengthened. At the same time, the mass exchange in the horizontal direction is also strengthened, and it has been extended to the entire main air distribution plate 5. At this time, the main furnace door 21 is closed. Start the coal feeder to add fine coal through the coal outlet 20, and switch to normal operation with 70% of the coal feed, and gradually increase it to normal according to the furnace temperature. Under the air supply of the main furnace blower 7, part of the burning coal jumping up and down in the main furnace 3 continuously crosses the middle retaining wall 17 into the auxiliary furnace 9 to accumulate and continue to burn.

[0051] When the temperature of the main furnace rises to above 800℃, the flame is orange-yellow, and the temperature difference between the upper, middle and lower points of the coal fluidized layer is getting smaller and smaller, the ignition of the main furnace 3 is completed. Use a rake to go deep into the bed material and swing it. If the swing resistance is small and the rake has touched the main air cap 4, it means that the entire bed material of the main furnace 3 has reached the fluidized state.

[0052] Step 4: After the auxiliary furnace 2 is ignited, the main furnace 3 runs stably for 8 hours, and the bed material in the auxiliary furnace 9 has reached the height of the middle retaining wall 17, the auxiliary furnace blower 13 is started, and its air volume is slowly increased to normal. The bed material in the auxiliary furnace 9 is burned to a fluidized state, and part of the burning coal automatically falls into the main furnace 3 through the internal circulation channel 22 to continue burning, completing the internal circulation of the burning coal. When there is no obvious fluctuation in the air volume of the main furnace 3 and the current of the main furnace blower 7, it means that the auxiliary furnace 2 is successfully ignited, the main furnace 3 and the auxiliary furnace 9 are successfully combined, and the entire ignition process is completed.

[0053] After the main furnace and auxiliary furnace are successfully connected and run stably, the unburned fine dust particles in the boiler flue gas collected by the rear flue separator are fed into the auxiliary furnace through the return port for continued combustion and utilization. This process is the external circulation of coal.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for igniting a coal-fired boiler with a main furnace and an auxiliary furnace, characterized in that: The coal-fired boiler with main and auxiliary furnaces comprises a main furnace, an auxiliary furnace and an induced draft system. The main furnace comprises a main furnace, a main air hood, a main air distribution plate, a main furnace air chamber and a main furnace air blower. The auxiliary furnace comprises an auxiliary furnace, an auxiliary air hood, an auxiliary air distribution plate, an auxiliary furnace air chamber and an auxiliary furnace air blower. A combustion furnace surrounded by a furnace wall is arranged in the coal-fired boiler. The main furnace and the auxiliary furnace are respectively arranged in the combustion furnace and are separated from each other by an intermediate retaining wall. The main furnace air chamber is connected to an external main furnace air blower through a main furnace air duct. The main air hood and the main air distribution plate are located at the top of the main furnace air chamber. The auxiliary furnace air chamber is connected to an external auxiliary furnace air blower through the auxiliary furnace air duct. The auxiliary air hood, the auxiliary air distribution plate and the auxiliary furnace air chamber are connected to the external auxiliary furnace air blower through the auxiliary furnace air duct. The plate is located at the top of the auxiliary furnace air chamber, and the coal layer for combustion is burned on the top of the main wind cap and the auxiliary wind cap respectively. Part of the burning coal in the main furnace goes over the middle retaining wall under the action of the wind pressure of the main furnace blower and enters the auxiliary furnace to continue burning. A coal lowering port and a main furnace door are respectively arranged on the furnace wall of the main furnace, and an internal circulation channel connecting the main furnace and the auxiliary furnace is arranged on the middle retaining wall. The internal circulation channel opening on the auxiliary furnace side is higher than the internal circulation channel opening on the main furnace side, so that the burning coal in the auxiliary furnace automatically falls into the main furnace through the internal circulation channel to continue burning. The buried pipe containing the heating medium is arranged in the auxiliary furnace; The ignition method comprises the following steps: Step 1: Lay the bottom material in the main furnace. Evenly lay the cold slag on the main hood at the bottom of the main furnace as the bottom material. The laying thickness is 450mm to 500mm. Step 2: Ignite the main furnace, open the main furnace door, close other furnace doors, start the draft system to make the main furnace slightly negative pressure; put matches or charcoal in the main furnace and ignite them with igniters, wait for the firewood to burn into charcoal or the charcoal to burn through, break it up and lay it on the bottom material, repeat this process until the charcoal layer reaches 80mm to 120mm thick; Step 3: Start the main furnace blower to make the charcoal fire layer particles slightly jump up and down. When the charcoal fire particles in the furnace decrease and a reddish-red fire wave appears, add fine coal to increase the air flow. As the fine coal ignites and burns, the bottom material below also begins to burn. When the furnace temperature of the main furnace reaches 600℃~700℃, close the main furnace door, start the coal feeder to add fine coal through the coal lowering port, switch to normal operation with 70% of the coal feed, and gradually increase it to normal according to the furnace temperature. Under the air supply of the main furnace blower, part of the burning coal jumping up and down in the main furnace continuously passes over the middle retaining wall into the auxiliary furnace for accumulation and continues to burn. When the furnace temperature of the main furnace rises to above 800℃, the main furnace ignition is completed. Step 4: Light the auxiliary furnace. When the main furnace runs stably for 8 hours and the bed material accumulation in the auxiliary furnace has reached the height of the middle retaining wall, start the auxiliary furnace fan, and slowly increase its air volume to normal. The bed material in the auxiliary furnace burns to a fluidized state, and part of the burning coal automatically falls into the main furnace through the internal circulation channel to continue burning. When there is no obvious fluctuation in the air volume of the main furnace and the current of the main furnace fan, it means that the auxiliary furnace is successfully ignited, the main furnace and auxiliary furnace are successfully connected, and the whole ignition process is completed.

2. The ignition method of a coal-fired boiler with a main furnace and an auxiliary furnace according to claim 1, characterized in that: In step 1, cold slag refers to the coal slag discharged from the high and low differential bed boiler and screened, the proportion of the particle size between 0.1mm and 8mm accounts for more than 85wt% of the total amount, and the maximum particle size does not exceed 10mm.

3. The ignition method of a coal-fired boiler with a main furnace and an auxiliary furnace according to claim 1, characterized in that: In step 2, the thickness of the matches or charcoal is 30 mm to 40 mm.

4. The ignition method of a coal-fired boiler with a main furnace and an auxiliary furnace according to claim 1, characterized in that: In step three, the calorific value of the fine coal is 5000±200KJ / Kg, the proportion of particle sizes between 0.1mm and 8mm accounts for more than 80% of the total, the maximum particle size does not exceed 15mm, and the volatile matter is less than 11%.

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