A direct current burner and swirl burner cooperative combustion device and a cooperative combustion method

Abstract

The application relates to a direct-flow combustor and swirl combustor cooperative combustion device and method, and belongs to the technical field of tangential circle boiler combustion technology. In order to solve the problems of poor stable combustion effect of a coal power unit only relying on pulverized coal combustion at 20%-30% rated load, reduced denitration efficiency during low-load operation, and unstable combustion caused by coal quality deviating from the design value, the application relies on the direct-flow primary air and direct-flow secondary air of a direct-flow combustor, the stable combustion cavity of a self-help stable combustion combustor, and swirl inner secondary air, so that a center backflow area is formed in the center of a swirl combustor, as a stable ignition heat source, high-concentration pulverized coal is heated, a flame formed by the self-help stable combustion combustor is ignited, a direct-flow pulverized coal combustor primary air powder flame is ignited, external flame combustion-supporting technologies such as micro-oil or plasma are not used, and the stable combustion effect of the coal power unit only relying on pulverized coal combustion at 20%-30% rated load is realized. The application is mainly used for improving the stable combustion effect of a boiler during work.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tangentially fired boiler combustion, in particular to a direct-flow burner and swirl burner cooperative combustion device and method. BACKGROUND

[0002] Some major new energy power generation forms, including solar power generation, wind power generation, water power generation, biomass power generation, etc., account for an increasing proportion year by year, and the utilization hours of thermal power are decreasing year by year. The energy structure system is constantly changing. However, new energy power generation in the power industry is facing many challenges, which are mainly due to its randomness and instability. Since the influence of new energy power generation on the power system is more complex and difficult to predict, in order to maintain the stability of the power grid and promote the clean and low-carbon transformation of the power industry, large thermal power units need to have deep flexible peak shaving capability. In the improvement of the flexibility of the unit peak shaving capability, the most critical problem is to realize the stable operation of the boiler at 20%-30% of the rated load.

[0003] Coal-fired boiler power generation is currently the main part of China's energy structure. The main combustion method of coal-fired boilers is to arrange direct-flow burners on the four corners or eight corners of the boiler furnace, and the coal powder gas flow and the secondary air are injected into the furnace through the direct-flow burners. The coal powder gas flow is ignited by the direct impact of the high-temperature flame from the upstream adjacent corner, and the four-corner (or eight-corner) jet supports each other to form a rotating combustion flame. The four-corner (or eight-corner) tangentially fired pulverized coal boiler is the most widely used and mature boiler type in China's power plants, accounting for more than 70% of the total installed capacity. However, the stable combustion load of domestic coal-fired units without oil injection can only reach 30%-40%. Single reliance on coal powder combustion cannot achieve stable combustion at 20%-30% of the rated load, and the four-corner (or eight-corner) tangentially fired pulverized coal boiler cannot meet the deep peak shaving requirement.

[0004] Currently, to make the boiler not to oil stable combustion load to reach 20%-30%, it needs to be assisted by plasma, micro-oil or intermediate frequency electric heating technology to maintain the boiler 20%-30% rated load for a long time. The micro-oil stable combustion technology uses a small amount of oil (0.4t / h-0.6t / h of oil gun output) to ignite the coal powder, and through its own combustion heat release to strengthen the ignition and stable combustion of the coal powder, which has the advantage of strong coal adaptability, from lignite boiler to anthracite boiler. The disadvantage is that long-term operation has a certain negative impact on the electrode of the electric dust removal and the desulfurization slurry. On the other hand, the oil gun stable combustion consumes more than ten thousand tons of oil per year, which is poor in economy and extremely high in cost. The plasma stable combustion technology mainly uses high-power plasma gun to generate high-temperature arc to strengthen the ignition and stable combustion of the coal powder, which has the characteristics of economy and environmental protection, but has the disadvantages of short service life of the cathode and poor coal quality adaptability, and is often used for boilers burning high-volatile bituminous coal. The intermediate frequency electric heating technology uses intermediate frequency induction heating to obtain good low load and variable load combustion stability. However, due to the increase of the additional pulverizing system, the system is complex and the investment cost is increased; at the same time, the intermediate frequency induction is needed to heat the flammable bituminous coal, which is easy to slag in the flame extension pipe during long-term operation.

[0005] In addition, in the SCR (Selective Catalytic Reduction) denitrification of thermal power plants, high-temperature catalysts are generally used, and the designed operating temperature range is 320-420℃. When the load of the power plant is lower than 50%, the flue gas temperature is usually lower than 320℃. During low load operation, the performance of the SCR catalyst cannot be fully utilized, and the denitrification efficiency will be significantly reduced, and there is a great risk of NOx exceeding the standard at this time. At the same time, the coal quality in China is variable, and the coal quality used in power plant boilers is poor, which seriously deviates from the best coal parameters designed for the boiler, which directly affects the combustion stability of the power plant boiler. SUMMARY

[0006] The present application provides a kind of direct-flow burner and swirl burner collaborative combustion device and collaborative combustion method to solve the problems of poor stable combustion effect, low load operation denitrification efficiency reduction and combustion instability caused by coal quality deviation from design value of coal-fired unit only relying on coal combustion at 20%-30% rated load.

[0007] The application discloses a kind of direct-flow combustor and swirl burner synergistic combustion device, synergistic combustion device includes four corner circle coal powder combustion boiler, secondary air box and four direct-flow coal powder burners, four direct-flow coal powder burners are respectively arranged at four corners of four corner circle coal powder combustion boiler, each direct-flow coal powder burner corresponds at least one coal mill, direct-flow primary air nozzle in direct-flow coal powder burner is communicated with the coal outlet end of coal mill by coal supply pipeline arrangement, direct-flow secondary air nozzle in direct-flow coal powder burner is communicated with the air outlet end of secondary air box by air supply pipeline arrangement, at least one self-help stable combustion burner is arranged in each direct-flow coal powder burner, and each self-help stable combustion burner is arranged between direct-flow primary air nozzle and direct-flow secondary air nozzle in corresponding direct-flow coal powder burner in the same layer, and self-help stable combustion burner is communicated with the coal supply pipeline adjacent to direct-flow primary air nozzle and the air supply pipeline adjacent to direct-flow secondary air nozzle by air-powder system arrangement;

[0008] Further, direct-flow coal powder burner is divided into three layers from bottom to top, the first layer includes a layer of direct-flow secondary air nozzle and a layer of direct-flow primary air nozzle, and a layer of direct-flow primary air nozzle is located above a layer of direct-flow secondary air nozzle, the second layer includes two layers of direct-flow secondary air nozzle and two layers of direct-flow primary air nozzle, and two layers of direct-flow primary air nozzle are located above two layers of direct-flow secondary air nozzle, the third layer includes three layers of first direct-flow secondary air nozzle, three layers of direct-flow primary air nozzle and three layers of second direct-flow secondary air nozzle, and three layers of first direct-flow secondary air nozzle, three layers of direct-flow primary air nozzle and three layers of second direct-flow secondary air nozzle are sequentially arranged from bottom to top;

[0009] Further, the coal supply pipeline includes direct-flow primary air channel, primary air pipe and first regulating valve, one end of the direct-flow primary air channel is communicated with the corresponding direct-flow primary air nozzle, one end of the primary air pipe is communicated with the coal outlet end of the corresponding coal mill, the other end of the direct-flow primary air channel is communicated with the other end of the primary air pipe, and the first regulating valve is installed at the communication position of the direct-flow primary air channel and the primary air pipe;

[0010] Further, the coal supply pipeline further includes a second regulating valve, a third regulating valve, a first coal powder pipeline and a coal powder separation device, the coal inlet end of the coal powder separation device is communicated with the primary air pipe, and the second regulating valve is connected in series on the primary air pipe, the first coal outlet end of the coal powder separation device is communicated with the direct-flow primary air channel through the first coal powder pipeline, and the third regulating valve is connected in series on the first coal powder pipeline;

[0011] Further, the air supply pipeline includes direct-flow secondary air channel, secondary air duct and fourth regulating valve, one end of the direct-flow secondary air channel is communicated with the corresponding direct-flow secondary air nozzle, one end of the secondary air duct is communicated with the air outlet end of the corresponding secondary air box, the other end of the direct-flow secondary air channel is communicated with the other end of the secondary air duct, and the fourth regulating valve is installed at the communication position of the direct-flow secondary air channel and the secondary air duct.

[0012] Further, the self-stabilized combustion burner comprises a stabilization chamber, a rotational inner secondary air passage and a self-stabilized combustion burner straight primary air passage, the rotational inner secondary air passage is coaxially sleeved outside the self-stabilized combustion burner straight primary air passage, one end of the self-stabilized combustion burner straight primary air passage and one end of the rotational inner secondary air passage are both in communication with the stabilization chamber, the other end of the self-stabilized combustion burner straight primary air passage is in communication with a coal supply pipeline through a wind-powder system, the other end of the rotational inner secondary air passage is in communication with a wind supply pipeline through the wind-powder system, an axial blade group is arranged between the self-stabilized combustion burner straight primary air passage and the rotational inner secondary air passage, and the axial blade group is arranged close to the stabilization chamber, the axial blade group comprises a plurality of axial blades, the plurality of axial blades are equidistantly arranged between the self-stabilized combustion burner straight primary air passage and the rotational inner secondary air passage in a circumferential direction, one end of each axial blade is connected with an outer wall of the self-stabilized combustion burner straight primary air passage, and the other end of each axial blade is connected with an inner wall of the rotational inner secondary air passage;

[0013] Further, the wind-powder system comprises a straight coal supply pipeline and a rotational wind supply pipeline, the coal supply pipeline is in communication with the self-stabilized combustion burner straight primary air passage through the straight coal supply pipeline, and the wind supply pipeline is in communication with the rotational inner secondary air passage through the rotational wind supply pipeline;

[0014] Further, the straight coal supply pipeline comprises a self-stabilized combustion burner straight connection air duct, a No. 5 regulating valve, a No. 2 coal powder passage and a No. 6 regulating valve, the primary air pipe is in communication with the self-stabilized combustion burner straight primary air passage through the self-stabilized combustion burner straight connection air duct, the No. 5 regulating valve is connected in series on the self-stabilized combustion burner straight connection air duct, the No. 2 coal powder passage is in communication with the self-stabilized combustion burner straight primary air passage through the No. 2 coal powder passage at a No. 2 coal outlet of the coal powder separation device, and the No. 6 regulating valve is connected in series on the No. 2 coal powder passage;

[0015] The rotational wind supply pipeline comprises a self-stabilized combustion burner rotational connection air duct and a No. 7 regulating valve, the secondary air passage is in communication with the rotational inner secondary air passage through the self-stabilized combustion burner rotational connection air duct, and the No. 7 regulating valve is connected in series at the communication position of the rotational inner secondary air passage and the self-stabilized combustion burner connection air duct;

[0016] A kind of direct-flow burner and swirl burner in the cooperative combustion method of boiler at more than 50% rated load operating condition;Shut off No. 2 regulating valve, by changing the opening of No. 1 regulating valve to 80%-100%, control the speed of primary air into the direct-flow primary air passage to 26-28m / s, by changing the opening of No. 5 regulating valve to 80%-100%, control the speed of primary air into the self-stable combustion burner to 22-26m / s, shut off No. 7 regulating valve, so that there is no rotating secondary air in the self-stable combustion burner, the secondary air can pass through No. 4 regulating valve to 70%-80%, control the speed of secondary air into the direct-flow secondary air passage to 45-47m / s, after the above operation, its stable combustion cavity compared to the furnace cross section has larger heat load, the heat released after combustion makes the temperature in the stable combustion cavity rise rapidly and maintain at high temperature, at the same time, the unburned pulverized coal gas flow rises to the direct-flow primary air nozzle with the flue gas, mixes with the primary air sprayed from the direct-flow primary air nozzle again, continues to burn, compared with the original furnace four corners only arranging direct-flow burner, the burnout area is increased, which is beneficial to the burnout of pulverized coal, so as to realize the cooperative combustion of direct-flow pulverized coal burner and self-stable combustion burner at more than 50% rated load.

[0017] A kind of direct-flow burner and swirl burner in the cooperative combustion method of boiler at less than 50% rated load operating condition;Shut off No. 1 regulating valve and No. 5 regulating valve, open No. 2 regulating valve, the primary air powder can pass through No. 2 regulating valve into the pulverized coal separation device, the pulverized coal gas flow enters No. 1 powder passage, by changing the opening of No. 3 regulating valve to 50%-80%, control the speed of primary air into the direct-flow primary air passage to 16-26m / s, the pulverized coal gas flow enters No. 2 pulverized coal passage, by changing the opening of No. 6 regulating valve to 40%-80%, control the speed of primary air into the direct-flow primary air passage of self-stable combustion burner to 14-22m / s, by adjusting the opening of No. 7 regulating valve to 40%-70%, control the speed of secondary air into the swirl inner secondary air passage to 35-50m / s, by adjusting the opening of No. 4 regulating valve to 30%-60%, control the speed of secondary air into the direct-flow secondary air passage to 30-45m / s, after the above operation, by controlling the speed of primary air and swirl inner secondary air of self-stable combustion burner, a wide and long central recirculation zone is formed in the stable combustion cavity, by controlling the speed of direct-flow primary air and secondary air arranged above and below, the rotating air flow is limited to expand at the same time, the gas flow in the stable combustion cavity is injected, the length of central recirculation zone continues to grow, wherein De refers to the diameter of inner secondary air, D is the maximum diameter of recirculation zone, L is the maximum length, the diameter of recirculation zone is 0.8De

[0018] The present application produces the beneficial effects relative to the prior art:

[0019] 1. The present application provides a kind of direct-flow burner and swirl burner synergistic combustion device and synergistic combustion method, rely on the direct-flow burner direct-flow primary air, the injection effect of direct-flow secondary air, synergistic swirl burner stable combustion chamber and swirl inner secondary air, make its form center recirculation zone in the center of swirl burner, as stable ignition heat source, heat high concentration coal powder, simultaneously, the flame formed by swirl burner, ignite direct-flow burner primary air powder flame, without the aid of micro-oil or plasma and other external flame combustion-supporting technology, realize that coal power unit only relies on coal powder combustion at 20%-30% rated load stable combustion effect.

[0020] Prior art is arranged on the four corners or eight corners of boiler furnace direct-flow burner, coal powder gas flow and secondary air are sprayed into furnace through direct-flow burner jet, converge in the form of tangent circle (such as Figure 1 Shown), coal powder gas flow is ignited by the direct impact of upstream adjacent corner high temperature flame to one side of fire, and four corners (or eight corners) jet support each other. Therefore, the high temperature flame of each corner jet and ignition combustion is the main heat source to ignite downstream coal powder gas flow, and the ignition of coal powder gas flow is sequentially ignited by each corner.

[0021] With the decrease of boiler load, gradually reduce the coal grinding amount and shut down the coal mill, the amount of coal powder sent into the furnace is greatly reduced, and the amount of coal powder sent into the furnace at 20%-30% rated load is about 25%-40% of full load. When running at low load, with the decrease of coal supply amount, the heat released by coal powder combustion decreases, while the furnace volume and the heating surface in the furnace remain unchanged, resulting in the decrease of the temperature of the furnace burner area, which is only about 900℃ at 20%-30% rated load (the temperature of the furnace burner area is about 1300℃ at full load). As the main heat source to ignite downstream coal powder gas flow, the temperature of upstream flame decreases significantly, and the heat transfer amount decreases, which is lower than the heat required for the ignition of coal powder gas flow. Therefore, the four corner (or eight corner) tangent circle coal powder boiler is difficult to achieve stable combustion effect at 20%-30% rated load only relying on coal powder combustion.

[0022] The present application directly sends high concentration coal powder gas flow into stable combustion chamber in the form of direct flow, which expands to the wall of stable combustion chamber under the action of swirl inner secondary air, and the pressure in the center of the burner decreases. The speed of coal powder gas flow after leaving the stable combustion chamber is 8-9 m / s, the speed range of direct-flow primary air arranged above and below is 16-28 m / s, and the speed range of direct-flow secondary air is 30-47 m / s, which is high and has large momentum. Under the further injection of high-speed direct-flow primary and secondary air, a wide and long center recirculation zone is formed in the center of the burner (such as Figure 7The maximum values of D and L can reach 1.5-2De and 3.5-4De respectively. Wherein De refers to the inner secondary air diameter, D is the maximum diameter of the backflow area, and L is the maximum length. The maximum flue gas flow rate is 7-8 times the primary air flow rate. The central backflow area entrains a large amount of high-temperature flue gas, and in the area between the outside of the backflow area and the main flow, a turbulent mixing area of the coal powder flow and the hot backflow flue gas is formed, in which strong mass, momentum and energy exchange occurs, the coal powder flow is continuously heated and heated to the ignition temperature to start ignition. The flame spreads from the inside to the outside, and the heat is also transmitted to the backflow flue gas, which is carried upstream, and the heat is transmitted to the new coal powder flow. At the same time, the high-temperature flue gas of the backflow has a low speed, effectively prolonging the residence time of the coal powder in the high-temperature area, so that the coal powder is fully burned to release a large amount of heat, and the temperature of the flue gas in the central backflow area can reach above 1300℃. The high-concentration coal powder flow is concentrated in the high-temperature central backflow area and forms a high-temperature and high-concentration area in the central backflow area. The self-stabilized burner relies on the high-temperature and high-concentration backflow area as a stable heat source to make the coal powder flow entering the stable combustion chamber ignite in time and burn stably. The high-temperature flame is sprayed from the stable combustion chamber of the self-stabilized burner.

[0023] The high-temperature flame sprayed from the self-stabilized burner ignites the primary air powder flow of the straight-flow coal burner above. Compared with the original furnace four corners or eight corners only arranged with straight-flow burners, the straight-flow burners cooperating with the swirl burners can make the coal powder sprayed by the straight-flow burners ignite in time and can be severely burned, so that the temperature of the coal powder flame is increased. This is beneficial to the mutual ignition of the tangential straight-flow burners, strengthens the combustion of the coal powder flow during tangential combustion, makes the flame more stable, and enhances the combustion stability of the tangential straight-flow burners under 20%-30% rated load.

[0024] 2. The straight-flow burner and swirl burner cooperative combustion device and method provided by the application can ensure that the flue gas temperature at the denitration inlet is within a reasonable range under 20%-30% rated load.

[0025] With the decrease of the boiler load, the coal grinding amount gradually decreases and the coal mill is stopped, and the amount of coal powder sent into the furnace is greatly reduced, which is about 25%-40% of the full load under 20%-30% rated load. The amount of coal powder sent into the furnace is reduced, the heat released by the coal powder combustion is reduced, and the furnace temperature is reduced, so that the coal powder flame is unstable. Under 20%-30% rated load, the coal mill is stopped, and the corresponding straight-flow primary air and straight-flow secondary air are stopped. In order to protect the straight-flow primary air and straight-flow secondary air nozzles from overheating and burning out, the straight-flow secondary air nozzle baffle opening degree is kept between 5%-10%, which plays a role in cooling the nozzle. This part of the cooling secondary air accounts for about 20%-40% of the total secondary air. When the boiler is running at low load, such as Figure 2If the upper layer direct current primary air and direct current secondary air (third layer No. 2 secondary air nozzle, third layer primary air nozzle and third layer No. 1 secondary air nozzle) are put into operation, the low-temperature direct current secondary air for cooling the nozzle of the lower layer will be mixed into the upper layer direct current primary air coal powder gas flow, so that the coal powder flame is more unstable. If the lower layer direct current primary air and direct current secondary air (first layer primary air nozzle and first layer secondary air nozzle) are put into operation, the low-temperature direct current secondary air for cooling the nozzle of the upper layer moves upward and has the least influence on the lower layer direct current primary air coal powder gas flow. Therefore, in order to maximize the stability of the flame, the lower layer direct current primary air and direct current secondary air are generally put into operation. Compared with full load operation, low load operation of the lower layer direct current primary air and direct current secondary air will cause the flame center to move downward, the flue gas temperature at the furnace outlet to decrease, and the SCR denitration inlet flue gas temperature to be generally as low as about 260-280℃, which is difficult to reach the best flue gas temperature of the coal-fired power plant denitration device catalyst.

[0026] The present application relies on the direct current primary air and direct current secondary air of the direct current burner for ejection, cooperates with the self-help stable combustion burner stable combustion chamber and the swirling inner secondary air, forms a central recirculation zone in the center of the self-help stable combustion burner, serves as a stable ignition heat source, heats high-concentration coal powder, and at the same time, the high-temperature flame sprayed by the swirling burner burns, ignites the direct current primary air powder flame, strengthens the tangential combustion of the coal powder gas flow, makes the flame more stable, enhances the coal powder combustion stability at 20%-30% rated load, and makes it possible to flexibly put the upper layer direct current primary air and direct current secondary air or the lower layer direct current primary air and direct current secondary air into operation at low load. At 20%-30% rated load, (for example, Figures 8 to 10 As shown, four self-help stable combustion burners are arranged at the four corners between the first layer primary air nozzle and the second layer secondary air nozzle of the direct current burner, and the SCR denitration inlet flue gas temperature can be increased by 10%-15%. Four self-help stable combustion burners are arranged at the four corners between the third layer primary air nozzle and the third layer No. 1 secondary air nozzle of the direct current burner, and the SCR denitration inlet flue gas temperature can be increased by 15%-20%. According to the actual SCR denitration inlet flue gas temperature, the self-help stable combustion burners can be arranged between the primary air and secondary air nozzles of the direct current burners at different layers, which can not only ensure the stability of the flame at low load, but also increase the position of the furnace flame center, increase the flue gas temperature at the furnace outlet, and ensure that the SCR denitration inlet flue gas temperature is within a reasonable range at 20%-30% rated load, thereby preventing the NOx emission from exceeding the standard.

[0027] 3. The direct current burner and swirling burner cooperative combustion device and the cooperative combustion method provided by the present application can effectively improve the coal powder burnout rate.

[0028] The prior art arranges the direct current burners at the four corners or eight corners of the boiler furnace, and the coal powder gas flow and the secondary air are sprayed into the furnace through the direct current burner jet, and are converged in the form of a tangent circle, (as shown inFigure 1 The tangential combustion mode can cause the gas streams emitted by adjacent burners to ignite each other, but the coal powder gas stream ignites at a long distance. Meanwhile, the primary air powder gas stream is linearly injected, the gas stream diffusion angle is small, the axial kinetic energy is large, the range is long, and the high-temperature flue gas can only mix into the gas stream, so that the coal powder at the periphery of the gas stream ignites first, and then gradually expands to the center of the gas stream, the ignition is delayed, and this is not conducive to the complete combustion of the coal powder.

[0029] The four self-help stable combustion burners are arranged at the four corners between the straight-flow primary air injection port and the straight-flow secondary air injection port of the straight-flow coal powder burner. At low load, the straight-flow primary air and the straight-flow secondary air of the straight-flow burner are used to guide the self-help stable combustion burner, and the inner secondary air of the swirl flow burner is used to form a high-temperature central backflow area in the center of the self-help stable combustion burner, as a stable ignition heat source, heat the high-concentration coal powder, form a high-temperature and high-concentration area in the central backflow area, and prolong the residence time of the coal powder in the high-temperature area, which is conducive to the complete combustion of the coal powder in the swirl flow burner. Meanwhile, the high-temperature flame emitted by the swirl flow burner below ignites the primary air powder flame of the straight-flow burner above. Compared with the original furnace with only straight-flow burners arranged at the four corners or the eight corners, the ignition distance of the coal powder gas stream emitted by the straight-flow burner is shortened, the ignition is timely, the coal powder combustion time in the furnace is increased, and the complete combustion of the coal powder is facilitated.

[0030] At high load, the coal powder gas stream of the original furnace with only straight-flow burners arranged at the four corners or the eight corners is at 28-30 m / s. In the present application, the primary air powder gas stream is divided into two parts. One part enters the stable combustion chamber through the straight-flow primary air channel of the self-help stable combustion burner. The outlet area of the stable combustion chamber is 1.2-1.5 times the area of the straight-flow primary air injection port. The coal powder gas stream exits the stable combustion chamber at a speed of 8-9 m / s and enters the furnace. On the one hand, the speed of the coal powder gas stream is low, the residence time in the furnace is long, and the complete combustion of the coal powder is facilitated. On the other hand, the stable combustion chamber has a large heat load compared with the cross section of the furnace. The heat released after combustion causes the temperature in the stable combustion chamber to rise rapidly and remain at a high temperature. At the same time, the unburned coal powder gas stream rises with the flue gas to the straight-flow primary air injection port, mixes with the primary air emitted by the straight-flow primary air injection port, and continues to burn. Compared with the original furnace with only straight-flow burners arranged at the four corners or the eight corners, the burning area is increased, and the complete combustion of the coal powder is facilitated. The other part enters the straight-flow primary air injection port through the straight-flow primary air channel. The coal powder gas stream enters the furnace at a speed of 26-28 m / s. Compared with the original furnace with only straight-flow burners arranged at the four corners or the eight corners, the speed of the coal powder gas stream of the straight-flow burner that cooperates with the swirl flow burner is reduced, the combustion time in the furnace is sufficient, the complete combustion of the coal powder is facilitated, the combustion efficiency is improved, and the self-help stable combustion burner is provided.

[0031] 4. The straight-flow burner and swirl flow burner cooperative combustion device and method provided by the present application have a large primary air speed adjustment range and good adjustment characteristics compared with the prior art.

[0032] The prior art arranges straight-flow burners on four or eight corners of a boiler furnace, and each mill corresponds to a layer of burners. The mill outlet is connected to four primary air pipes, and the air speed of these air pipes is mainly determined by the air volume at the mill inlet. When the coal quantity of the mill is unchanged, the air speed can be finely adjusted within a certain range (±2 m / s). This fine adjustment is limited in terms of the change range of the air speed. When the coal quality fluctuates, the stable combustion performance of the straight-flow burners deteriorates, and the primary air speed needs to be adjusted accordingly. If the primary air speed is greatly reduced in order to improve the stable combustion performance, the coal grinding quantity of a single burner will decrease, thereby causing the temperature in the burner area to decrease and further reducing the stable combustion performance of the burner.

[0033] The present application can finely control the air speed of the straight-flow burners and the primary air pipes of the swirl burners by adjusting the valve opening of the straight-flow burners and the primary air pipes of the swirl burners while keeping the air volume of the mill unchanged, and the adjustment range is large and the adjustment performance is good. The boiler can maintain the best combustion state under the condition of coal quality fluctuation. When the coal quality deteriorates and the stable combustion performance of the straight-flow burners deteriorates, the straight-flow primary air speed is adjusted by changing the opening of the two adjusting doors on the straight-flow primary air passage and the opening of the adjusting door on the first pulverized coal passage. The straight-flow primary air speed ranges from 16 to 28 m / s. Through the above adjustment method, the straight-flow primary air speed can be greatly reduced, and the residence time of the pulverized coal gas flow in the burner area is increased, which is beneficial to the ignition and stable combustion of the pulverized coal. While reducing the straight-flow primary air speed, the self-stable combustion burner straight-flow primary air speed is adjusted by changing the opening of the adjusting door on the second pulverized coal passage and the opening of the adjusting door on the straight-flow primary air passage of the self-stable combustion burner. The self-stable combustion burner straight-flow primary air speed ranges from 14 to 26 m / s. The swirl inner secondary air speed is adjusted by changing the opening of the adjusting door on the swirl inner secondary air passage, and the swirl secondary air speed ranges from 35 to 50 m / s. By using high swirl inner secondary air speed and low primary air speed, the range of the central recirculation zone is increased (the diameter of the recirculation zone is 1.2De<D2<2De, and the length is 3De<L2<4De). The amount of high-temperature flue gas recirculated by the recirculation is large, and the pulverized coal is ignited in time. At the same time, the high-temperature flame of the self-stable combustion burner ignites the pulverized coal gas flow of the straight-flow pulverized coal burner above, and low-load stable combustion is achieved.

[0034] When the coal quality is good, the coal powder gas flow at the outlet of the straight-flow burner will ignite early, causing the flame to be too close to the nozzle, which is prone to cause problems such as nozzle burning and slagging. By changing the opening degree of the two regulating doors on the straight-flow primary air channel and the opening degree of the regulating door on the No. 1 coal powder channel, the straight-flow primary air speed is jointly adjusted, and the straight-flow primary air speed ranges from 16 to 28 m / s. Through the above adjustment method, the straight-flow primary air speed can be greatly increased, so that the coal powder gas flow can be dispersed more quickly in the furnace after leaving the straight-flow burner, thereby slowing down the ignition speed and moving the ignition point backward appropriately. While increasing the straight-flow primary air speed, the opening degree of the regulating door on the No. 2 coal powder channel and the opening degree of the regulating door on the straight-flow primary air channel of the self-stabilizing burner are changed to jointly adjust the straight-flow primary air speed of the self-stabilizing burner, and the straight-flow primary air speed of the self-stabilizing burner ranges from 14 to 26 m / s. The straight-flow primary air speed of the self-stabilizing burner is reduced, and the opening degree of the regulating door on the swirling inner secondary air channel is changed to adjust the swirling inner secondary air speed, and the swirling inner secondary air speed ranges from 35 to 50 m / s. Through accurate control of the straight-flow primary air speed and the swirling inner secondary air speed of the self-stabilizing burner, the backflow area is pushed away from the nozzle, and in the case of ensuring stable combustion, the phenomenon of burning caused by the close distance between the high-temperature backflow area and the burner nozzle is prevented.

[0035] 5. The straight-flow burner and swirling burner cooperative combustion device and the cooperative combustion method provided by the application, wherein the self-stabilizing burner and the straight-flow burner can be switched to operate, thereby reducing accidents such as extinguishing caused by the shutdown of a single burner.

[0036] Power plants often have accidents of boiler shutdown caused by the failure of a single burner, which seriously threatens the safe and stable operation of the boiler. The application realizes independent control of the self-stabilizing burner and the straight-flow burner by controlling the regulating doors, so that when one of the burners needs to be repaired or fails, the air supply and fuel supply thereof can be quickly cut off, and the other burner can continue to work. When the self-stabilizing burner needs to be repaired or fails, the No. 1 regulating door is opened to cut off the self-stabilizing burner system while ensuring that the first layer of primary air provides coal powder combustion, thereby avoiding shutdown. When the first layer of primary air burner needs to be repaired or fails, the No. 2 regulating door is opened to cut off the first layer of primary air system while ensuring that the self-stabilizing burner provides coal powder combustion, thereby avoiding shutdown. The instant switching capability avoids the full furnace shutdown caused by the failure of a single burner, greatly improves the availability and stability of the boiler, and can flexibly cope with different working conditions and failure conditions, thereby significantly improving the stable operation capability and overall safety of the boiler.

[0037] 6. The direct-flow burner and swirl-flow burner cooperative combustion device and method provided by the application are beneficial to enhancing the coal type adaptability of a boiler and improving the capacity adaptability of the boiler.

[0038] Power plant boilers are usually optimized for specific coal types at the design stage to ensure that the combustion efficiency and heat output reach the expected standards. When burning poor coal, the volatile matter content is the main heat source for coal powder ignition. Coal with low volatile matter content is difficult to ignite, requiring higher ignition temperature and longer ignition time, which increases the difficulty and instability of combustion. In addition, boilers of different capacities have significant differences in structure, operating parameters, and fuel requirements, which further limits the adaptability of power plant boilers in different capacity applications.

[0039] The present application relies on the direct-flow primary air and direct-flow secondary air of the direct-flow burner, the stable combustion cavity of the self-stable combustion burner, and the swirl inner secondary air to form a central recirculation zone in the center of the self-stable combustion burner, which serves as a stable ignition heat source to heat high-concentration coal powder. At the same time, the high-temperature flame emitted by the swirl-flow burner ignites the surrounding direct-flow burner primary air flame, strengthening the tangential combustion of the coal powder gas flow and making the flame more stable. Multiple layers of self-stable combustion burners can be added according to the actual boiler capacity requirements and the coal quality requirements, ensuring that the temperature in the furnace burner area remains around 1300°C even when burning poor coal. Without the aid of external flame combustion technologies such as micro-oil or plasma, the coal-fired power plant can achieve stable combustion at 20%-30% of the rated load solely relying on coal powder combustion. When burning bituminous coal with Vdaf>20% or applying to boilers with a capacity below 300MW, one layer of self-stable combustion burners can be added. When burning lean coal with Vdaf between 10% and 20% or applying to boilers with a capacity between 300MW and 600MW, two layers of self-stable combustion burners can be added. When burning anthracite coal with Vdaf<10% or applying to boilers with a capacity above 600MW, three layers of self-stable combustion burners can be added (as shown in Figures 11 to 13 ). BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 A four-corner tangential ignition schematic diagram of the cooperative combustion device described in the present application;

[0041] Figure 2 A layout schematic diagram of a direct-flow burner in the cooperative combustion device described in the present application;

[0042] Figure 3 A B-B view of a direct-flow burner in the cooperative combustion device described in the present application;

[0043] Figure 4 A wind-powder system diagram of a self-stable combustion burner in the cooperative combustion device described in the present application;

[0044] Figure 5 A schematic diagram of the self-stabilized combustion burner in the synergic combustion device described in the present application;

[0045] Figure 6 A C-C direction schematic diagram of the self-stabilized combustion burner in the synergic combustion device described in the present application;

[0046] Figure 7 A schematic diagram of the self-stabilized combustion burner in the synergic combustion device described in the present application;

[0047] Figure 8 A schematic diagram of the self-stabilized combustion burner in the synergic combustion device described in the present application;

[0048] Figure 9 A schematic diagram of the self-stabilized combustion burner in the synergic combustion device described in the present application;

[0049] Figure 10 A schematic diagram of the self-stabilized combustion burner in the synergic combustion device described in the present application;

[0050] Figure 11 A schematic diagram of the self-stabilized combustion burner in the synergic combustion device described in the present application;

[0051] Figure 12 A schematic diagram of the self-stabilized combustion burner in the synergic combustion device described in the present application;

[0052] Figure 13 A schematic diagram of the self-stabilized combustion burner in the synergic combustion device described in the present application. DETAILED DESCRIPTION

[0053] Specific implementation one: combined with Figures 1 to 13The present embodiment provides a direct-flow coal burner and swirl burner cooperative combustion device. The device comprises a tangential circle coal powder combustion boiler 11, a secondary air box 31 and four direct-flow coal burners 10. The four direct-flow coal burners 10 are arranged at the four corners of the tangential circle coal powder combustion boiler 11 respectively. Each direct-flow coal burner 10 corresponds to at least one coal mill 21. The direct-flow primary air nozzle 1 in the direct-flow coal burner 10 is in communication with the coal outlet end of the coal mill 21 through a coal supply pipeline. The direct-flow secondary air nozzle 3 in the direct-flow coal burner 10 is in communication with the air outlet end of the secondary air box 31 through an air supply pipeline. The device is characterized in that at least one self-supporting combustion burner 2 is arranged in each direct-flow coal burner 10. Each self-supporting combustion burner 2 is arranged between the direct-flow primary air nozzle 1 and the direct-flow secondary air nozzle 3 at the same level in the corresponding direct-flow coal burner 10. The self-supporting combustion burner 2 is in communication with the coal supply pipeline adjacent to the direct-flow primary air nozzle 1 and the air supply pipeline adjacent to the direct-flow secondary air nozzle 3 through a wind-powder system.

[0054] The direct-flow coal burner 10 is divided into three layers from bottom to top. The first layer comprises a layer of direct-flow secondary air nozzles 20 and a layer of direct-flow primary air nozzles 19. The layer of direct-flow primary air nozzles 19 is above the layer of direct-flow secondary air nozzles 20. The second layer comprises two layers of direct-flow secondary air nozzles 18 and two layers of direct-flow primary air nozzles 17. The two layers of direct-flow primary air nozzles 17 are above the two layers of direct-flow secondary air nozzles 18. The third layer comprises three layers of direct-flow secondary air nozzles 16, three layers of direct-flow primary air nozzles 15 and three layers of direct-flow secondary air nozzles 14. The three layers of direct-flow secondary air nozzles 16, the three layers of direct-flow primary air nozzles 15 and the three layers of direct-flow secondary air nozzles 14 are sequentially arranged from bottom to top.

[0055] The coal supply pipeline comprises a direct-flow primary air channel 5, a primary air pipe 22 and a first regulating valve 23. One end of the direct-flow primary air channel 5 is in communication with the corresponding direct-flow primary air nozzle 1. One end of the primary air pipe 22 is in communication with the coal outlet end of the corresponding coal mill 21. The other end of the direct-flow primary air channel 5 is in communication with the other end of the primary air pipe 22. A first regulating valve 23 is installed at the communication position of the direct-flow primary air channel 5 and the primary air pipe 22.

[0056] The coal supply pipeline further comprises a second regulating valve 25, a third regulating valve 26, a first coal powder pipeline 27 and a coal powder separation device 28. The coal inlet end of the coal powder separation device 28 is in communication with the primary air pipe 22. The second regulating valve 25 is connected in series on the primary air pipe 22. The first coal outlet end of the coal powder separation device 28 is in communication with the direct-flow primary air channel 5 through the first coal powder pipeline 27. The third regulating valve 26 is connected in series on the first coal powder pipeline 27.

[0057] The air supply pipeline comprises a straight-flow secondary air passage 7, a secondary air duct 32 and a fourth regulating valve 34, one end of the straight-flow secondary air passage 7 is in communication with the corresponding straight-flow secondary air nozzle 3, one end of the secondary air duct 32 is in communication with the air outlet end of the corresponding secondary air box 31, the other end of the straight-flow secondary air passage 7 is in communication with the other end of the secondary air duct 32, and the fourth regulating valve 34 is installed at the communication position of the straight-flow secondary air passage 7 and the secondary air duct 32;

[0058] The self-stabilized combustion burner 2 comprises a stabilization chamber 4, a rotational-flow inner secondary air passage 6 and a straight-flow primary air passage 8 of the self-stabilized combustion burner, the rotational-flow inner secondary air passage 6 is coaxially sleeved outside the straight-flow primary air passage 8 of the self-stabilized combustion burner, one end of the straight-flow primary air passage 8 of the self-stabilized combustion burner and one end of the rotational-flow inner secondary air passage 6 are both in communication with the stabilization chamber 4, the other end of the straight-flow primary air passage 8 of the self-stabilized combustion burner is in communication with the coal supply pipeline through the air-powder system, the other end of the rotational-flow inner secondary air passage 6 is in communication with the air supply pipeline through the air-powder system, an axial blade group 9 is arranged between the straight-flow primary air passage 8 of the self-stabilized combustion burner and the rotational-flow inner secondary air passage 6, the axial blade group 9 is arranged close to the stabilization chamber 4, the axial blade group 9 comprises a plurality of axial blades, the plurality of axial blades are equidistantly arranged between the straight-flow primary air passage 8 of the self-stabilized combustion burner and the rotational-flow inner secondary air passage 6 in the circumferential direction, one end of each axial blade is connected with the outer wall of the straight-flow primary air passage 8 of the self-stabilized combustion burner, and the other end of each axial blade is connected with the inner wall of the rotational-flow inner secondary air passage 6;

[0059] The air-powder system comprises a straight-flow coal supply pipeline and a rotational-flow air supply pipeline, the coal supply pipeline is in communication with the straight-flow primary air passage 8 of the self-stabilized combustion burner through the straight-flow coal supply pipeline, and the rotational-flow air supply pipeline is in communication with the rotational-flow inner secondary air passage 6 through the rotational-flow air supply pipeline;

[0060] The straight-flow coal supply pipeline comprises a straight-flow connection air duct of the self-stabilized combustion burner, a fifth regulating valve 24, a second coal powder passage 29 and a sixth regulating valve 30, the primary air pipe 22 is in communication with the straight-flow primary air passage 8 of the self-stabilized combustion burner through the straight-flow connection air duct of the self-stabilized combustion burner, the fifth regulating valve 24 is connected in series on the straight-flow connection air duct of the self-stabilized combustion burner, the second coal outlet end of the coal powder separation device 28 is in communication with the straight-flow primary air passage 8 of the self-stabilized combustion burner through the second coal powder passage 29, and the sixth regulating valve 30 is connected in series on the second coal powder passage 29;

[0061] The rotational-flow air supply pipeline comprises a rotational-flow connection air duct of the self-stabilized combustion burner and a seventh regulating valve 33, the secondary air duct 32 is in communication with the rotational-flow inner secondary air passage 6 through the rotational-flow connection air duct of the self-stabilized combustion burner, and the seventh regulating valve 33 is connected in series at the communication position of the rotational-flow inner secondary air passage 6 and the connection air duct of the self-stabilized combustion burner.

[0062] This embodiment provides a co-combustion device for a DC burner and a swirl burner. The outlet of the DC pulverized coal burner 10 consists of a DC primary air nozzle 1 and a DC secondary air nozzle 3, both of which are rectangular nozzles. The DC primary air nozzles 1 and 3 are arranged alternately. An upstream corner flame is ignited at the root of the downstream DC pulverized coal burner 10, forming an actual flame zone 12. The DC primary air enters the DC primary air nozzle 1 through the DC primary air channel 5 and is injected into the furnace in a DC manner, forming an imaginary tangent circle 13 at the center of the furnace. Another path passes through the DC primary air channel 8 of the self-sustaining burner, supplying pulverized coal to the self-sustaining burner 2, and enters the combustion chamber 4 in a DC manner. The DC secondary air enters the DC secondary air nozzle 3 through the DC secondary air channel 7 and is injected into the furnace in a DC manner. The swirl secondary air enters the combustion chamber 4 in a rotating manner after passing through the axial blade assembly 9 within the swirl secondary air channel 6. Under the action of secondary air and combustion stabilization chamber 4 in the swirling flow, the primary air and pulverized coal form a stable recirculation zone in the center of the combustion stabilization chamber and enter the furnace in the form of the recirculation zone.

[0063] The DC pulverized coal burner 10 provided in this embodiment has three layers. The arrangement principle of the coal mill 21 and the secondary air box 32 is that each layer of DC primary air nozzle and DC secondary air nozzle in the DC pulverized coal burner 10 corresponds to one coal mill 21 and one secondary air box 32. According to the actual flue gas temperature at the SCR denitrification inlet, the self-sustaining combustion burner 2 can be flexibly arranged, that is, the self-sustaining combustion burner 2 is arranged between the primary air and secondary air nozzles of different layers of DC burners. When the rated load is 20%-30%, in order to effectively increase the flue gas temperature at the SCR denitrification inlet, four self-sustaining combustion burners 2 (one in each DC pulverized coal burner 10) are arranged at the four corners between the first layer of DC primary air nozzle 19 and the first layer of DC secondary air nozzle 20 of the lowest layer of DC burner. The flue gas temperature at the SCR denitrification inlet can be increased by 5%-10%. Four self-contained combustion stabilizers 2 are arranged at the four corners between the second-layer DC primary air nozzle 17 and the second-layer DC secondary air nozzle 18. This can increase the SCR denitrification inlet flue gas temperature by 10%-15%. Similarly, four self-contained combustion stabilizers 2 are arranged at the four corners between the third-layer DC primary air nozzle 15 and the third-layer No. 1 DC secondary air nozzle 16. This can also increase the SCR denitrification inlet flue gas temperature by 10%-15%. For details of these arrangements, please refer to the appendix. Figure 8 To be continued Figure 10 ;

[0064] In actual work, according to the actual boiler capacity demand and the coal quality requirement, multiple self-stabilizing combustion burners 2 can be installed to realize the stable combustion effect of the coal-fired unit at 20%-30% rated load only by relying on the pulverized coal combustion without the aid of external flame stabilizing technology such as micro-oil or plasma. When bituminous coal with Vdaf>20% is burned or when the boiler capacity is below 300 MW, one layer of self-stabilizing combustion burners 2 can be installed; when lean coal with Vdaf of 10%-20% is burned or when the boiler capacity is between 300 MW and 600 MW, two layers of self-stabilizing combustion burners 2 can be installed; when anthracite coal with Vdaf<10% is burned or when the boiler capacity is above 600 MW, three layers of self-stabilizing combustion burners 2 can be installed. The above arrangement can be specifically referred to the attached Figure 11 to the attached Figure 13 .

[0065] Specific implementation method two: combined with Figures 1 to 13 In this embodiment, a method for the coordinated combustion of the straight-flow burner and the swirl burner when the boiler is operated at a load higher than 50% of the rated load is provided. The second regulating valve 25 is closed, the opening of the first regulating valve 23 is changed to 80%-100% to control the speed of the primary air entering the straight-flow primary air passage 5 to 26-28 m / s, the opening of the fifth regulating valve 24 is changed to 80%-100% to control the speed of the primary air entering the self-stabilizing combustion burner 2 to 22-26 m / s, and the seventh regulating valve 33 is closed so that there is no rotating secondary air in the self-stabilizing combustion burner 2. The opening of the fourth regulating valve 34 is changed to 70%-80% to control the speed of the secondary air entering the straight-flow secondary air passage 7 to 45-47 m / s. Through the above operation, the oxygen required for the complete combustion of the supplementary fuel is supplied, thereby realizing the coordinated combustion of the straight-flow pulverized coal burner 10 and the self-stabilizing combustion burner 2 at a load higher than 50% of the rated load.

[0066] The synergistic combustion method provided in the embodiment is used when the boiler is operated at more than 50% rated load, and the self-stabilizing burner 2 is introduced to work at high load, which can effectively improve the burnout rate of the pulverized coal at high load. The present application divides the primary air flow into two parts, one of which enters the stable combustion chamber 4 through the straight-flow primary air passage 8 of the self-stabilizing burner, and the outlet area of the stable combustion chamber 4 is 1.2-1.5 times the area of the straight-flow primary air nozzle 1. The pulverized coal flow exits the stable combustion chamber at a speed of 8-9 m / s and enters the furnace. On the one hand, the speed of this stream of pulverized coal is low, and the residence time in the furnace is long, which is beneficial to the burnout of the pulverized coal. On the other hand, the stable combustion chamber has a larger heat load compared to the furnace cross section, and the heat released after combustion causes the temperature in the stable combustion chamber to rise rapidly and remain at a high temperature. At the same time, the unburned pulverized coal flow rises with the flue gas to the straight-flow primary air nozzle and mixes with the primary air again, continuing to burn. Compared with the original furnace with only straight-flow burners arranged at the four corners or eight corners, the increase in the burnout area is beneficial to the burnout of the pulverized coal. The other part enters the straight-flow primary air nozzle through the straight-flow primary air passage, and the pulverized coal flow enters the furnace at a speed of 26-28 m / s. Compared with the original furnace with only straight-flow burners arranged at the four corners or eight corners, the speed of the pulverized coal flow of the straight-flow burner cooperating with the cyclone burner is reduced, and the combustion time in the furnace is sufficient, which is beneficial to the burnout of the pulverized coal and improves the combustion efficiency.

[0067] Specific embodiment three: combination Figures 1 to 13In the present embodiment, a method for the coordinated combustion of a straight-flow burner and a swirl burner when the boiler is operated at less than 50% of the rated load is provided. The first regulating valve 23 and the fifth regulating valve 24 are closed, and the second regulating valve 25 is opened. The pulverized coal can enter the coal pulverizing device 28 through the second regulating valve 25, and the coal gas flow enters the first pulverized coal passage 27. The third regulating valve 26 is adjusted to 50%-80% to control the speed of the primary air entering the straight-flow primary air passage 5 to 16-26 m / s. The coal gas flow enters the second pulverized coal passage 29. The sixth regulating valve 30 is adjusted to 40%-80% to control the speed of the primary air entering the straight-flow primary air passage 8 of the self-stabilized burner to 14-22 m / s. The seventh regulating valve 33 is adjusted to 40%-70% to control the speed of the secondary air entering the swirl inner secondary air passage 6 to 35-50 m / s. The fourth regulating valve 34 is adjusted to 30%-60% to control the speed of the secondary air entering the straight-flow secondary air passage 7 to 30-45 m / s. Through the above operations, the speed of the primary air of the self-stabilized burner and the speed of the swirl inner secondary air are controlled to form a wide and long central recirculation zone in the stable combustion chamber 4. The speeds of the straight-flow primary air and secondary air arranged above and below are controlled to limit the expansion of the rotating gas flow, inject the gas flow in the stable combustion chamber, slow down the gas flow decay, and make the central recirculation zone continue to grow. De refers to the diameter of the inner secondary air, D is the maximum diameter of the recirculation zone, and L is the maximum length. The diameter of the recirculation zone is 0.8De

[0068] The coordinated combustion method provided in the present embodiment is used when the boiler is operated at less than 50% of the rated load. The specific conditions and adjustment ranges are further divided into the following cases:

[0069] Case 1: The method of the straight-flow burner and the swirl-flow burner cooperating combustion when the boiler is running at 40%-50% rated load, close the first regulating valve 23 and the fifth regulating valve 24, open the second regulating valve 25, the primary air powder can pass through the second regulating valve 25 into the coal powder separation device 28, the coal powder gas flow enters the first powder channel 27, by changing the opening of the third regulating valve 26 to 70%-80%, the primary air speed into the straight-flow primary air channel 5 is controlled to 22-26 m / s, the coal powder gas flow enters the second coal powder channel 29, by changing the opening of the sixth regulating valve 30 to 60%-80%, the primary air speed into the straight-flow primary air channel 8 of the self-supporting stable combustion burner is controlled to 20-22 m / s, by adjusting the opening of the seventh regulating valve 33 to 60%-70%, the secondary air speed into the swirl-flow inner secondary air channel 6 is controlled to 45-50 m / s, by adjusting the opening of the fourth regulating valve 34 to 50%-60%, the secondary air speed into the straight-flow secondary air channel 7 is controlled to 40-45 m / s, through the above operation, by controlling the primary air speed of the self-supporting stable combustion burner and the swirl-flow inner secondary air speed, a wide and long central recirculation zone is formed in the stable combustion chamber 4, by controlling the straight-flow primary air and secondary air speed arranged above and below, the rotation airflow is expanded while the airflow in the stable combustion chamber is injected, the airflow decay is slowed down, the length of the central recirculation zone continues to grow, wherein De refers to the inner secondary air diameter, D is the maximum diameter of the recirculation zone, L is the maximum length, the diameter of the recirculation zone is 0.8De

[0070] Case 2: The method of the straight-flow burner and the swirl-flow burner cooperating combustion when the boiler is running at 30%-40% rated load, close the first regulating valve 23 and the fifth regulating valve 24, open the second regulating valve 25, the primary air powder can pass through the second regulating valve 25 into the coal powder separation device 28, the coal powder gas flow enters the first powder channel 27, by changing the opening of the third regulating valve 26 to 60%-70%, the primary air speed into the straight-flow primary air channel 5 is controlled to 18-22 m / s, the coal powder gas flow enters the second coal powder channel 29, by changing the opening of the sixth regulating valve 30 to 50%-60%, the primary air speed into the straight-flow primary air channel 8 of the self-supporting stable combustion burner is controlled to 17-20 m / s, by adjusting the opening of the seventh regulating valve 33 to 50%-60%, the secondary air speed into the swirl-flow inner secondary air channel 6 is controlled to 40-45 m / s, by adjusting the opening of the fourth regulating valve 34 to 40%-50%, the secondary air speed into the straight-flow secondary air channel 7 is controlled to 35-40 m / s, through the above operation, by controlling the primary air speed of the self-supporting stable combustion burner and the swirl-flow inner secondary air speed, a wide and long central recirculation zone is formed in the stable combustion chamber 4, by controlling the straight-flow primary air and secondary air speed arranged above and below, the rotation airflow is expanded while the airflow in the stable combustion chamber is injected, the airflow decay is slowed down, the length of the central recirculation zone continues to grow, wherein De refers to the inner secondary air diameter, D is the maximum diameter of the recirculation zone, L is the maximum length, the diameter of the recirculation zone is 1.2De

[0071] Case 3: The method of the combined combustion of the straight-flow burner and the swirl-flow burner when the boiler is operated at 20%-30% of the rated load, the first regulating valve 23 and the fifth regulating valve 24 are closed, and the second regulating valve 25 is opened. The pulverized coal can enter the coal-pulverizing device 28 through the second regulating valve 25, and the coal-pulverized gas flow enters the first pulverized coal passage 27. The opening of the third regulating valve 26 is changed to 50%-60% to control the speed of the primary air entering the straight-flow primary air passage 5 to 16-18 m / s, and the coal-pulverized gas flow enters the second pulverized coal passage 29. The opening of the sixth regulating valve 30 is changed to 40%-50% to control the speed of the primary air entering the straight-flow primary air passage 8 of the self-stabilized combustion burner to 14-17 m / s. The opening of the seventh regulating valve 33 is changed to 40%-50% to control the speed of the secondary air entering the swirl-flow inner secondary air passage 6 to 35-40 m / s. The opening of the fourth regulating valve 34 is changed to 30%-40% to control the speed of the secondary air entering the straight-flow secondary air passage 7 to 30-35 m / s. Through the above operations, the speed of the primary air of the self-stabilized combustion burner and the speed of the swirl-flow inner secondary air are controlled to form a wide and long central recirculation zone in the stable combustion chamber 4. The speed of the straight-flow primary air and secondary air arranged above and below is controlled to limit the expansion of the rotating gas flow, inject the gas flow in the stable combustion chamber, slow down the gas flow decay, and continuously increase the length of the central recirculation zone. De refers to the diameter of the inner secondary air, D is the maximum diameter of the recirculation zone, and L is the maximum length. The diameter of the recirculation zone is 1.5 De < D1 < 2 De, and the length is 3.5 De < L1 < 4 De. The maximum flue gas flow rate is 7-8 times the primary air flow rate, so that the straight-flow pulverized coal burner 10 and the self-stabilized combustion burner 2 are combined to burn at 30%-40% of the rated load.

[0072] In combination with the second specific embodiment and the third specific embodiment, when the self-stabilized combustion burner 2 is overhauled or fails, the self-stabilized combustion burner 2 system can be cut off by closing the fifth regulating valve 24 and the second regulating valve 25 and opening the first regulating valve 23, while ensuring that the straight-flow primary air nozzle 19 provides pulverized coal combustion to avoid shutdown. When the straight-flow burner is overhauled or fails, the straight-flow burner can be cut off by closing the first regulating valve 23 and the second regulating valve 25 and opening the fifth regulating valve 24, while ensuring that the self-stabilized combustion burner 2 provides pulverized coal combustion to avoid shutdown. Thus, the straight-flow pulverized coal burner 10 and the self-stabilized combustion burner 2 can be independently combusted, and the stable operation of the boiler is improved.

[0073] The present application has been disclosed in the preferred embodiments as above, however, not for limiting the present application, any skilled person in the art can make some changes or modifications to the equivalent embodiments with the above disclosed structure and technical content without departing from the scope of the present application, but any simple modification, equivalent change and modification made according to the technical essence of the present application to the above embodiments are still within the scope of the present application. DETAILED DESCRIPTION

[0075] The technology has been applied to a 600 MW subcritical pressure drum boiler, which adopts four-corner tangential combustion. The boiler burns mixed coal of anthracite, lean coal and bituminous coal (coal quality characteristics are similar to lean coal), adopts a steel ball mill direct-fired pulverizing system, and the burner is provided with 6 layers of pulverized coal direct-flow burners. The boiler is provided with 6 steel ball mills, 6 layers are operated at MCR load of the boiler, and there is no standby. One layer of direct-flow primary air nozzle is arranged between two adjacent layers of direct-flow secondary air nozzles, one layer of direct-flow secondary air nozzle is arranged at the uppermost layer and the lowermost layer, the direct-flow secondary air nozzle at the uppermost layer plays a role of pulverized coal burnout, and the direct-flow secondary air nozzle at the lowermost layer plays a role of bottom support air. Before the burner is not transformed, the minimum non-oil stable combustion load of the boiler is 40%. At 30%-40% of the rated load, the third layer of the pulverizing system and the micro-oil system are operated, and the SCR system inlet flue gas temperature is 280-350℃. At less than 30% of the rated load, the second layer and the third layer of the pulverizing system and the micro-oil system are operated, and the SCR system inlet flue gas temperature is 260-280℃. When the coal quality fluctuates, the primary air speed can be adjusted within a certain range (±2 m / s) under the condition that the coal quantity of the mill is unchanged. The adjustment of the speed is limited in range, and the boiler has 3-4 times of extinguishing accidents within one year, which seriously affects the safe operation of the unit and causes a loss of about 3 million yuan.

[0076] The device and method of the application are used to arrange four self-stabilizing burners at the four corners between the straight-flow primary air nozzle and the straight-flow secondary air nozzle of the second layer straight-flow pulverized coal burner. The pulverized coal is taken from the branch pipeline of the second layer pulverizing system, and the air is taken from the secondary air box. At high load (more than 50% of the rated load), the fly ash carbon content is reduced from 10% before the transformation to 6% by the cooperative combustion of the straight-flow burner and the swirl burner, and the boiler efficiency is increased from 90.8% before the transformation to 92.9%. Under the condition of burning the same coal, the flame formed by the self-stabilizing burner ignites the primary air powder flame of the straight-flow burner without the help of external flame combustion technology such as micro-oil or plasma, realizes the stable combustion of the unit at 20%-30% of the rated load only by the pulverized coal combustion, saves the combustion oil cost of about 2 million yuan. At the same time, the inlet smoke temperature of the SCR system is increased to about 300℃. When the coal quality fluctuates greatly from anthracite (Vdaf=8%) to bituminous coal (Vdaf=38%), no boiler flameout accident occurs, the loss caused by flameout is reduced, and the total loss is 3 million yuan.

[0077] Under the requirement of "fully exerting the emergency peak regulation capacity of existing coal-fired units", the load of deep regulation of the thermal power unit will be further reduced, and the deep regulation time will be greatly increased. In order to encourage the thermal power unit to reduce the deep regulation load to below 30% of the rated load, each region adopts a step-by-step pricing incentive policy to set a higher pricing upper limit for the unit load rate below 30%. Taking the incentive policy of Heilongjiang Province as an example, when the load rate is below 25%, the price of 0.7-1 yuan / kwh can be declared. The "straight-flow burner and swirl burner cooperative combustion method and device" of the application can realize stable combustion at 20% of the rated load, and the comprehensive benefit of the burner after transformation is 70-80 million yuan more than that before transformation.

Claims

1. A direct-flow and swirl-flow burner cooperative combustion device, the cooperative combustion device comprising a four-corner tangential coal powder combustion boiler (11), a secondary air box (31), and four direct-flow coal powder burners (10), the four direct-flow coal powder burners (10) being respectively arranged at four corners of the four-corner tangential coal powder combustion boiler (11), each direct-flow coal powder burner (10) corresponding to at least one coal mill (21), a direct-flow primary air nozzle (1) in the direct-flow coal powder burner (10) being in communication with a coal outlet end of the coal mill (21) through a coal supply pipeline, and a direct-flow secondary air nozzle (3) in the direct-flow coal powder burner (10) being in communication with an air outlet end of the secondary air box (31) through an air supply pipeline, characterized in that: At least one self-stabilized combustion burner (2) is arranged in each straight-flow pulverized coal burner (10), and each self-stabilized combustion burner (2) is arranged between the straight-flow primary air nozzle (1) and the straight-flow secondary air nozzle (3) at the same layer in the corresponding straight-flow pulverized coal burner (10), and the self-stabilized combustion burner (2) is in communication with the coal supply pipeline adjacent to the straight-flow primary air nozzle (1) and the air supply pipeline adjacent to the straight-flow secondary air nozzle (3) through the air-pulverized coal system; The self-stabilized combustion burner (2) comprises a stable combustion chamber (4), a swirling inner secondary air channel (6) and a self-stabilized combustion burner straight-flow primary air channel (8), the swirling inner secondary air channel (6) is coaxially sleeved outside the self-stabilized combustion burner straight-flow primary air channel (8), one end of the self-stabilized combustion burner straight-flow primary air channel (8) and one end of the swirling inner secondary air channel (6) are both in communication with the stable combustion chamber (4), the other end of the self-stabilized combustion burner straight-flow primary air channel (8) is in communication with the coal supply pipeline through the air-pulverized coal system, and the other end of the swirling inner secondary air channel (6) is in communication with the air supply pipeline through the air-pulverized coal system. The air-pulverized coal system comprises a straight-flow coal supply pipeline and a swirling air supply pipeline, the coal supply pipeline is in communication with the self-stabilized combustion burner straight-flow primary air channel (8) through the straight-flow coal supply pipeline, and the air supply pipeline is in communication with the swirling inner secondary air channel (6) through the swirling air supply pipeline.

2. A direct and tangential flow burner co-combustion apparatus according to claim 1, characterized in that: The straight-flow pulverized coal burner (10) is divided into three layers from bottom to top, the first layer comprises one layer of straight-flow secondary air nozzles (20) and one layer of straight-flow primary air nozzles (19), and the one layer of straight-flow primary air nozzles (19) is located above the one layer of straight-flow secondary air nozzles (20), the second layer comprises two layers of straight-flow secondary air nozzles (18) and two layers of straight-flow primary air nozzles (17), and the two layers of straight-flow primary air nozzles (17) are located above the two layers of straight-flow secondary air nozzles (18), and the third layer comprises three layers of first straight-flow secondary air nozzles (16), three layers of straight-flow primary air nozzles (15) and three layers of second straight-flow secondary air nozzles (14), and the three layers of first straight-flow secondary air nozzles (16), the three layers of straight-flow primary air nozzles (15) and the three layers of second straight-flow secondary air nozzles (14) are sequentially arranged from bottom to top.

3. A direct and tangential flow burner co-combustion apparatus according to claim 2, characterized in that: The coal supply pipeline comprises a straight-flow primary air channel (5), a primary air pipe (22) and a first regulating valve (23), one end of the straight-flow primary air channel (5) is in communication with the corresponding straight-flow primary air nozzle (1), one end of the primary air pipe (22) is in communication with the coal outlet end of the corresponding coal mill (21), the other end of the straight-flow primary air channel (5) is in communication with the other end of the primary air pipe (22), and the first regulating valve (23) is installed at the communication position of the straight-flow primary air channel (5) and the primary air pipe (22).

4. A direct and tangential flow burner co-combustion apparatus according to claim 3, characterized in that: The coal supply pipeline further comprises a second regulating valve (25), a third regulating valve (26), a first pulverized coal pipeline (27), and a pulverized coal separation device (28). The coal inlet of the pulverized coal separation device (28) is in communication with the primary air pipeline (22), and the primary air pipeline (22) is in series with the second regulating valve (25). The first coal outlet of the pulverized coal separation device (28) is in communication with the straight-flow primary air passage (5) through the first pulverized coal pipeline (27), and the first pulverized coal pipeline (27) is in series with the third regulating valve (26).

5. A direct and tangential flow burner co-combustion apparatus according to claim 4, characterized in that: The air supply pipeline comprises a straight-flow secondary air passage (7), a secondary air duct (32), and a fourth regulating valve (34). One end of the straight-flow secondary air passage (7) is in communication with the corresponding straight-flow secondary air nozzle (3). One end of the secondary air duct (32) is in communication with the air outlet end of the corresponding secondary air box (31). The other end of the straight-flow secondary air passage (7) is in communication with the other end of the secondary air duct (32), and the fourth regulating valve (34) is installed at the communication position of the straight-flow secondary air passage (7) and the secondary air duct (32).

6. A direct and tangential flow burner co-combustion apparatus according to claim 5, characterized in that: An axial blade group (9) is arranged between the straight-flow primary air passage (8) of the self-stabilized combustion burner and the rotational flow inner secondary air passage (6), and the axial blade group (9) is arranged close to the self-stabilized combustion cavity (4). The axial blade group (9) comprises a plurality of axial blades. The plurality of axial blades are arranged equidistantly in the circumferential direction between the straight-flow primary air passage (8) of the self-stabilized combustion burner and the rotational flow inner secondary air passage (6). One end of each axial blade is connected with the outer wall of the straight-flow primary air passage (8) of the self-stabilized combustion burner, and the other end of each axial blade is connected with the inner wall of the rotational flow inner secondary air passage (6).

7. A direct and tangential flow burner co-combustion apparatus according to claim 6, characterized in that: The straight-flow coal supply pipeline comprises a self-stabilized combustion burner straight-flow connecting air duct, a fifth regulating valve (24), a second pulverized coal passage (29), and a sixth regulating valve (30). The primary air pipeline (22) is in communication with the straight-flow primary air passage (8) of the self-stabilized combustion burner through the self-stabilized combustion burner straight-flow connecting air duct, and the self-stabilized combustion burner straight-flow connecting air duct is in series with the fifth regulating valve (24). The second coal outlet of the pulverized coal separation device (28) is in communication with the straight-flow primary air passage (8) of the self-stabilized combustion burner through the second pulverized coal passage (29), and the second pulverized coal passage (29) is in series with the sixth regulating valve (30). The rotational flow air supply pipeline comprises a self-stabilized combustion burner rotational flow connecting air duct and a seventh regulating valve (33). The secondary air duct (32) is in communication with the rotational flow inner secondary air passage (6) through the self-stabilized combustion burner rotational flow connecting air duct, and the seventh regulating valve (33) is arranged at the communication position of the rotational flow inner secondary air passage (6) and the self-stabilized combustion burner connecting air duct.

8. A method for realizing the synergic combustion of a boiler at a load higher than 50% of the rated load, by means of the synergic combustion device of the direct flow burner and the cyclone burner according to any one of claims 1 to 7, characterized in that, Shut off the second regulating valve (25), by changing the opening of the first regulating valve (23) to 80%-100%, control the primary air speed into the straight flow primary air channel (5) to 26-28m / s, by changing the opening of the fifth regulating valve (24) to 80%-100%, control the primary air speed into the self-stable combustion burner (2) to 22-26m / s, shut off the seventh regulating valve (33), so that there is no rotating secondary air in the self-stable combustion burner (2), the secondary air can pass through the fourth regulating valve (34) opening to 70%-80%, control the secondary air speed into the straight flow secondary air channel (7) to 45-47m / s, through the above operation, the self-stable combustion chamber (4) has a larger heat load compared with the furnace cross section, the heat released after combustion makes the temperature in the self-stable combustion chamber (4) rise rapidly and maintain at a high temperature, at the same time, the unburned pulverized coal gas flow rises to the straight flow primary air nozzle (1) with the flue gas, mixes with the primary air sprayed from the straight flow primary air nozzle (1) again, continues to burn, compared with the original furnace with straight flow burners arranged at four corners, the burnout area is increased, which is beneficial to the burnout of pulverized coal, thereby realizing the cooperative combustion of the straight flow pulverized coal burner (10) and the self-stable combustion burner (2) at more than 50% rated load.

9. A method for realizing the synergic combustion of a boiler at a load lower than 50% of the rated load, by means of a synergic combustion apparatus comprising a direct flow burner and a swirl burner according to any one of claims 1 to 7, characterized in that: Shut off the first regulating valve (23) and the fifth regulating valve (24), open the second regulating valve (25), the primary air powder can pass through the second regulating valve (25) into the pulverized coal separation device (28), the pulverized coal gas flow enters the first pulverized coal pipeline (27), by changing the opening of the third regulating valve (26) to 50%-80%, control the primary air speed into the straight flow primary air channel (5) to 16-26m / s, the pulverized coal gas flow enters the second pulverized coal channel (29), by changing the opening of the sixth regulating valve (30) to 40%-80%, control the primary air speed into the straight flow primary air channel (8) of the self-stable combustion burner to 14-22m / s, by adjusting the opening of the seventh regulating valve (33) to 40%-70%, control the secondary air speed into the rotational inner secondary air channel (6) to 35-50m / s, by adjusting the opening of the fourth regulating valve (34) to 30%-60%, control the secondary air speed into the straight flow secondary air channel (7) to 30-45m / s, through the above operation, by controlling the primary air and rotational inner secondary air speed of the self-stable combustion burner, a wide and long central recirculation zone is formed in the self-stable combustion chamber (4), by controlling the straight flow primary and secondary air speed arranged above and below, the rotational air flow is limited to expand at the same time, the air flow in the self-stable combustion chamber is injected, the air flow decay is slowed down, the length of the central recirculation zone continues to grow, wherein De refers to the inner secondary air diameter, D is the maximum diameter of the recirculation zone, L is the maximum length, the diameter of the recirculation zone is 0.8De

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