Pulverized coal combustion method suitable for large-dust kiln condition

Abstract

The invention discloses a pulverized coal combustion method suitable for a large-dust kiln condition, and belongs to the field of lime for rotary kiln roasting metallurgy. The method comprises the steps that (1) the primary air volume and the air pressure are improved, the pulverized coal clamping capacity of primary air is enhanced, more secondary air is entrained to form bright and powerful flames under the dust kiln condition, and the combustion rate is increased; (2) the diameter of an outer pipe of the burner is enlarged, the sectional area of flames is increased, and the improved pulverized coal burner comprises a primary combustion-supporting air channel, an axial flow air channel, an adjusting valve of the axial flow air channel, a rotational flow air channel, a central air channel, an elevator wave compensation adjusting assembly and an air atomization pipeline; an adjusting mechanism is arranged in the combustor in a matched mode. According to the invention, the diameter of the outer tube of the burner is enlarged, so that the sectional area of flame is increased, a larger burning space is provided for the flame, the dust content in the unit volume of a flame area is reduced, the chemical reaction time of pulverized coal burning is prolonged, the influence of dust on pulverized coal burning is weakened, and the burner adapts to the dust kiln condition by improving the dust containing capacity of the burner.

Description

Technical Field

[0001] The present invention relates to a pulverized coal combustion method suitable for a kiln condition with a large amount of dust, and belongs to the field of lime roasting in a rotary kiln for metallurgy. Background Art

[0002] Metallurgical production enterprises mainly use three major process equipment, namely a preheater, a rotary kiln, and a cooler, to produce highly reactive white lime for metallurgy. The heat source for calcining limestone comes from a pulverized coal burner at the kiln head, and the combustion performance of the pulverized coal burner directly affects coal consumption and kiln conditions. Aiming at the problem of low strength of raw limestone, it is not adaptable to the existing combustion technology; due to the low hardness of the raw limestone ore and the relatively large combined water content in the internal microscopic crystal particles, it is easy to cause problems such as bursting and pulverization after entering the kiln and a large amount of dust in the kiln. The burners used in the existing process severely restrict the combustion of pulverized coal, resulting in afterburning of pulverized coal, low burnout rate, and divergent flame in a dust environment; problems such as nodulation and ring formation in the kiln, blockage of the preheater, blackening of the dust removal ash, and excessive CO in the exhaust gas at the kiln tail are prominent. The burner is a non-standard equipment designed for each kiln. In view of the above problems, there is an urgent need to design a pulverized coal burner suitable for a kiln condition with a large amount of dust, and to match the primary air process operation to improve the kiln condition, reduce coal consumption, and ensure production. Summary of the Invention

[0003] In order to solve the problem that the original burner cannot adapt to the roasting of the existing easily pulverized ash ore, the present invention aims to provide a pulverized coal combustion method suitable for a kiln condition with a large amount of dust.

[0004] The present invention mainly focuses on the problems of low strength of raw limestone, easy bursting during the roasting process, resulting in a large amount of dust in the kiln, incomplete combustion of pulverized coal, and nodulation and ring formation in the kiln, and conducts improvements in the burner design and the primary air fan air distribution technology.

[0005] The innovation points of the present invention are as follows: ① fully considering the influence of the dust content on the combustion of pulverized coal and increasing the cross-sectional size of the burner; ② increasing the primary air velocity to enhance the ability of the secondary combustion-supporting air to be involved in the combustion zone; ③ adding a wind-gathering hood device to improve the polymerization degree of the coal-air mixture ejected from the gun and enhance the flame forward impact in a multi-dust environment; ④ calculating and designing the influence range of the swirling air mixing and disturbance to weaken the mutual interference of the axial cyclones on the flame formation and forward impact rate.

[0006] The present invention provides a pulverized coal combustion method suitable for a kiln condition with a large amount of dust, including the following contents: (1) Selection of the primary air fan and matching of the primary air volume and air pressure Increasing the primary air volume and air pressure can enhance the ability of the primary air to hold the pulverized coal, break through the obstruction of the dust barrier, entrain more secondary air, form a bright and powerful flame under the kiln condition with dust, and increase the combustion rate; (2) The outer tube diameter of the burner is enlarged, increasing the cross-sectional area of the flame, providing a larger combustion space, reducing the dust content per unit volume in the flame area, lengthening the chemical reaction time of pulverized coal combustion, weakening the influence of dust on pulverized coal combustion, and adapting to the dust kiln condition by improving the dust-containing capacity of the burner: The improved pulverized coal burner includes a primary combustion-supporting air passage, an axial flow air passage and its regulating valve, a swirl air passage, a central air passage, a lift wave compensation regulating component, and an air atomization pipeline; In the burner, the outer tube diameter of the primary combustion-supporting air is φ350mm, the outer tube diameter of the burner is φ560mm, and the coal tube diameter is φ250mm. A regulating mechanism (burner wave compensation regulating component) is provided in the burner. The regulating mechanism includes an axial flow air metal bellows compensator, a swirl air metal bellows compensator, and a thermal compensator. Specifically, the regulating mechanism includes an axial flow air metal bellows compensator. When its spacing is shortened, the cross-sectional area of the axial flow air outlet increases, the axial flow air velocity decreases, the flame lengthens, and the pressure gauge reading decreases. When its spacing is extended, the cross-sectional area of the axial flow air outlet decreases, the axial flow air velocity increases, the flame shortens, and the pressure gauge reading increases. The regulating mechanism includes a swirl air metal bellows compensator. When its spacing is shortened, the cross-sectional area of the swirl air outlet increases, the swirl air velocity decreases, the flame shortens, and the pressure gauge reading decreases. When its spacing is extended, the cross-sectional area of the swirl air outlet decreases, the swirl air velocity increases, the flame lengthens, and the pressure gauge reading increases. The adjustment of the axial flow air compensator and the swirl air compensator is achieved through the regulating mechanism. The axial flow air metal bellows compensator and the swirl air metal bellows compensator have scale indicators. The allowable axial movement of the axial flow air is ±30mm, and the maximum adjustment amount each time does not exceed 5mm; the allowable axial movement of the swirl air is ±15mm, and the maximum adjustment amount each time does not exceed 3mm.

[0007] The head structure of the burner is designed as follows: The shape of the axial flow air holes is a square groove, and the number of square grooves is 32. The dimensions of the rectangular cross-section of the square groove are: length 22mm, width 12mm; the cross-sectional area of the groove can be adjusted accordingly, and the outer tube diameter of the axial flow air is φ560mm.

[0008] The head of the burner is equipped with a flame-gathering cover structure, which gathers the flame without divergence. The diameter of the flame-gathering cover is φ514mm.

[0009] The shape of the swirl air holes in the head structure of the burner is a spiral groove, and the number of spiral grooves is 24. The width of the spiral groove in the zero position of the wave compensation regulator is 13mm, and the normal width of the groove reaches 16mm by adjusting the length of the wave compensation with a lead screw; the cross-sectional area of the groove can be adjusted accordingly, and the outer tube diameter of the swirl air is φ356mm.

[0010] In the present invention, the primary air is provided by a Roots blower. The requirements for the primary air are small air volume and large pressure. Generally, the primary air volume of the lime rotary kiln is 12%-18% of the secondary air volume. The main function of the primary air is to control the shape of the pulverized coal injected into the kiln so as to control the flame shape, while the oxygen required for combustion mainly comes from the secondary air. The requirements for the secondary air are large air volume and small wind pressure. If the wind pressure of the primary air is insufficient, the secondary air will pass by the flame under the traction of the ID fan at the kiln tail and cannot effectively participate in combustion. Therefore, the wind pressure of the primary air must be high enough to reach a certain wind speed to produce a jet-suction effect and draw in enough secondary air to participate in combustion. Specifically, the Roots blower of the primary process fan is re-selected with a wind pressure of 53.9 kPa and an air volume of 174.5 m 3 / min to make the axial flow wind speed reach 180-250 m / s.

[0011] The technical solution provided by the present invention matches the air volume and wind pressure of the primary fan, and improves the momentum of the combustion-supporting air for organizing the combustion of pulverized coal by the burner; optimizes the structure of the pulverized coal burner from the aspects of the penetration ability and combustion ability of the flame, and strengthens the ability of the pulverized coal to be efficiently mixed in the roasting zone to achieve complete combustion; the specific optimization and transformation technical solutions are as follows: 1. The combustion-supporting air enters the kiln in two parts to participate in combustion: one part is controlled by the primary combustion-supporting fan, which mainly plays the role of gathering fire to form a reasonable flame shape and organizing the mixed combustion of pulverized coal fuel, and the other part is the secondary hot air exchanged through the vertical cooler (auxiliary equipment of the rotary kiln). As much of this part of hot air as possible is utilized (depending on the height of the material layer and the cooling effect, heat will be carried into the kiln). Specifically, the limestone is preheated by the preheater for preliminary decomposition and then enters the rotary kiln for further roasting and decomposition to produce hot lime, which falls into the cooler for stacking. There is a secondary fan below the cooler, and the generated air cools the lime material layer evenly through 5 air caps. At the same time, the air is heated to become hot air, and the hot air enters the kiln and enters the flame under the entrainment of the primary air of the burner, providing oxygen for the combustion of the pulverized coal.

[0012] Match the primary air volume and wind pressure. Generally, the ratio of the primary combustion-supporting fan equipped at the kiln head of the lime rotary kiln is: the primary air volume is 12-18% of the secondary air volume.

[0013] 2. Optimization of the axial flow air cross-sectional area structure of the burner: The cross-sectional area of the original burner is non-adjustable and has a round-hole-shaped air outlet. It is optimized to be adjustable with a square-hole-shaped air outlet, and the cross-sectional area of the square groove can also be adjusted accordingly to increase or decrease. This structural design can change the axial flow wind speed by increasing the air volume or changing the cross-sectional area. According to the on-site pulverized coal consumption condition, a high-penetration ability flame with strong entrainment ability is adjusted. The designed wind speed of the optimized axial flow air can reach a maximum of 250 m / s, and the adjustable range is 180-250 m / s. The flame of the pulverized coal combustion is more powerful, the ability to entrain the secondary air is stronger, and the effect of penetrating the dust-laden air curtain is better.

[0014] 3. Add a flame concentrating hood to the burner: The original burner structure has no flame concentrating hood. After the pulverized coal is ejected, it immediately meets and mixes with the induced secondary air for combustion. The expansion effect of the rapid combustion makes the flame short and thick, and the penetration ability of the backward movement is limited (intuitively, there is a phenomenon of fire suppression). The ability of the induced combustion-supporting air at the flame tail to participate in the pulverized coal combustion mixture is greatly reduced, and the complete combustion of the pulverized coal cannot be achieved in the roasting zone; adding a flame concentrating hood structure to the burner can prevent the flame shape from spreading and burning immediately when the pulverized coal is ejected, concentrate the flame, mix while advancing spirally backward, enable the pulverized coal to be orderly and fully mixed and burned in a longer roasting zone, uniformly release heat energy, have a good roasting effect, effectively extend the high-temperature zone, be conducive to the improvement of the kiln atmosphere, and to a certain extent, can also effectively reduce the dust amount generated by the bursting stones.

[0015] 4. Enlarge the size of the burner to increase the combustion rate Based on the original structural dimensions, starting from increasing the diameter of the central air hole plate, sequentially expand the pipes of each layer, that is, increase the mixed columnar area of the pulverized coal combustion to ensure the effective mixed combustion of the pulverized coal. Especially in the soot environment with a high dust content, it is more necessary. The size of the original burner air pipe 1 is: Φ450mm, and the size of the outer air pipe of the newly designed burner is: Φ560mm. The overall combustion cross-sectional area is increased by about: 38.7%. In the enlarged mixed columnar area, the pulverized coal mixed combustion effect is better and the penetration ability is also better. This can ensure that when the pulverized coal consumption is greater than 7 - 8t / h, it can also be completely and fully mixed and burned, and there is no high-temperature concentration. The heat is slowly released in the roasting zone, reducing or avoiding the afterburning of the pulverized coal, so as to ensure that a large amount of unburned pulverized coal will not enter the preheater backward to cause preheater clinkerization. In this way, the ventilation in the kiln is good, the burner flame is smooth and regular, the pulverized coal burns completely, and the burnout rate can reach more than 99%.

[0016] 5. Adjust the process parameters during combustion: The low-nitrogen combustion working state can be adjusted online through the cross-sectional area and air volume and air valve ratio of the axial flow air and the swirl air, and a reasonable working condition for the pulverized coal combustion and the lime production quality of the rotary kiln can be adjusted online. The reasonable states of each working condition can be recorded and can be conveniently reset and adjusted in subsequent working conditions.

[0017] Preferably, by adjusting the wave compensation to change the cross-sectional area of the axial flow air and swirl air ports, the distribution ratio of the primary air basically reaches: axial flow air flow: swirl air flow: central air flow = 60:35:5. When the designed production capacity of the rotary kiln is 1000t / d and the coal feeding amount is 7000kg / h, the kiln head temperature is increased by 44℃, reaching 901℃, the operation is stable, the CO concentration is decreased by 3017ppm, the burnout rate of the pulverized coal in the kiln is significantly improved, the high-temperature bonding effect of the lime powder is improved with the increase of the kiln head temperature, and the powder rate in the kiln is decreased by 0.54%.

[0018] The beneficial effects of the present invention are as follows: The present invention designs a burner with a large cross-sectional area and a flame-holding cover, and selects a primary air fan with high wind speed and large air volume, so as to improve the entrainment ability of the primary air to the secondary air to obtain sufficient oxygen. The pulverized coal air is clamped by the strong primary air in the axial and swirling directions, breaks through the dust barrier to form a flame, improves the burnout rate of the pulverized coal, reduces the pulverized coal consumption, and improves the kiln condition. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of the overall structure of the burner of the present invention; Figure 2 is Figure 1 the top view of; Figure 3 is a schematic diagram of the head structure of the burner of the present invention.

[0020] In the figure, 1 - nozzle, 2 - axial flow air duct, 3 - pulverized coal air duct, 4 - swirling air duct, 5 - central air duct, 6 - ignition oil gun duct, 7 - side air duct, 8 - first rib plate, 9 - second rib plate, 10 - third rib plate, 11 - fourth rib plate, 12 - adjustment mechanism, 13 - ball valve, 14 - pressure gauge, 15 - flame-holding cover, 16 - air atomization pipeline, 17 - square groove, 18 - spiral groove. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0022] As Figures 1 to 3 shown, a pulverized coal burner adapted to a kiln condition with relatively large dust includes a primary combustion-supporting air channel (i.e., the side air duct 7 in the figure), an axial flow air duct 2 and its regulating ball valve 13, a swirling air duct 4, a central air duct 5, an adjustment mechanism 12, and an air atomization pipeline 16.

[0023] In a preferred embodiment, the adjustment mechanism 12 includes an axial flow air metal bellows compensator. When its spacing is shortened, the cross-sectional area of the axial flow air outlet increases, the axial flow air speed decreases, the flame lengthens, and the pressure gauge reading decreases. When its spacing is extended, the cross-sectional area of the axial flow air outlet decreases, the axial flow air speed increases, the flame shortens, and the pressure gauge reading increases.

[0024] In a preferred embodiment, the adjusting mechanism 12 includes a swirl air metal bellows compensator. When its spacing is shortened, the cross-sectional area of the swirl air outlet increases, the swirl air velocity decreases, the flame shortens, and the pressure gauge reading drops. When its spacing is extended, the cross-sectional area of the swirl air outlet decreases, the swirl air velocity increases, the flame lengthens, and the pressure gauge reading increases.

[0025] In a preferred embodiment, the adjustment of the axial air compensator and the swirl air compensator is achieved through the adjusting mechanism. The axial air metal bellows compensator and the swirl air metal bellows compensator have scale indications. The allowable axial movement of the axial air is ±30 mm, and the maximum adjustment amount each time does not exceed 5 mm; the allowable axial movement of the swirl air is ±15 mm, and the maximum adjustment amount each time does not exceed 3 mm.

[0026] In a preferred embodiment, the shape of the axial air holes in the burner head structure is a square groove 17. The number of square grooves is 32. The dimensions of the rectangle of the cross-section of the square groove are: length 22 mm and width 12 mm; the cross-sectional area of the groove can be adjusted accordingly. The outer diameter of the axial air outer tube is φ560 mm.

[0027] In a preferred embodiment, a flame concentrating hood 15 is provided on the burner head to concentrate the flame without divergence. The diameter of the flame concentrating hood is φ514 mm.

[0028] In a preferred embodiment, the shape of the swirl air holes in the burner head structure is a spiral groove. The number of spiral grooves is 24. The width of the spiral groove in the zero position of the bellows compensator is 13 mm, and the normal width of the groove reaches 16 mm by adjusting the length of the bellows with a lead screw; the cross-sectional area of the groove can be adjusted accordingly. The outer diameter of the swirl air outer tube is φ356 mm.

[0029] In a preferred embodiment, according to the cross-sectional areas of the channels at the end of the burner, the Roots blower of the primary process blower is reselected. The parameter requirements of the blower are: air pressure 53.9 kPa and air volume 174.5 m³ / min, so that the axial air velocity reaches 180 - 250 m / s. The primary air requires a small air volume and a large pressure. The primary air volume of the lime rotary kiln generally takes 12% - 18% of the secondary air volume. The main function of the primary air is to control the shape of the pulverized coal injected into the kiln and thus control the flame shape.

[0030] The implementation principle of the pulverized coal combustion technology of the present invention suitable for a kiln condition with a large amount of dust is as follows: After the atomized diesel oil is injected into the diesel oil channel to ignite and bake the kiln to reach the temperature rise curve, the pulverized coal air is turned on and the primary air is turned on. Adjust the burner bellows compensator according to the flame shape, adjust the frequency conversion of the Roots blower to provide an air pressure of 40 kPa and a flow rate of 174.5 m³ / min, and adjust the flame shape into the best state of a writing brush shape.

[0031] The specific implementation method is as follows: At a pulverized coal consumption of 10 t / h, to ensure complete combustion of the pulverized coal and no coal leakage at the kiln tail, in this embodiment, the primary air fan is configured at about 15%. Therefore, it is necessary to configure 171.5 m 3 / min (the secondary air volume of this process is 68,600 m 3 / h. The primary air volume is taken as 15% of the secondary air volume, and finally converted to m 3 / min) of primary air. (Different from the kiln skin protection of the cement kiln, the high-temperature secondary air, and the subsequent complete suspension preheater equipment, the cement kiln can be configured with a lower primary air volume. Generally, during normal production, the ratio is 8 - 10% to make more use of the hot secondary air).

[0032] The distance from this fan to the kiln head is calculated as 150 meters. The conveying pipeline is DN350, with a pressure loss of 57 Pa per meter, and the approximate pressure loss is 8.5 kPa. In addition, the new burner needs to ensure that the wind speed at the axial air outlet can reach 250 m / s. Then, the dynamic pressure head of the combustion-supporting air at the burner head needs to be 37.8 kPa. Adding the pressure loss, the pressure at the fan outlet needs to be 46.3 kPa. Checking the fan configuration manual, the model can be selected as 174.5 m 3 / min, air pressure: 53.9 kPa, power: 220 kW. A primary air fan with a larger air volume can be reconfigured. A new variable-frequency Roots blower is used to supply the combustion-supporting air (axial air, swirl air, and central air) of the burner. Through the regulating valve on the burner, the air volume of each channel can be reasonably distributed, so that the air volume of a certain channel can be used to the maximum to improve the pulverized coal combustion mixing ability. For example, when the original configuration uses two variable-frequency blowers, if the swirl air volume is too small, the excess swirl air volume is not sent to the burner through frequency reduction operation. Now, the excess swirl air can be adjusted through the distribution of the regulating valve to be fully used for the axial air, increasing the ability of the axial air to entrain secondary air, strengthening the pulverized coal mixed combustion, and further increasing the flame penetration ability. The primary air fan selects a variable-frequency Roots blower, with an air volume of 174.5 m 3 / min, air pressure: 53.9 kPa, power: 220 kW. Based on the original two blowers (80.6 m 3 / min), the surplus is increased to improve the quality requirement in the momentum of the primary combustion-supporting air.

[0033] According to the on-site pulverized coal consumption working condition, a high-penetration ability flame with strong entrainment ability is adjusted. The designed wind speed of the optimized axial air structure can reach up to 250 m / s, and the adjustable range is 180 - 250 m / s. The flame of the pulverized coal combustion is more powerful, the ability to entrain secondary air is stronger, and the effect of penetrating the dust-laden air curtain is better.

[0034] Adjust the process parameters during combustion: The preferred parameters in this embodiment are as follows: The axial flow air metal bellows compensator and the swirl flow air metal bellows compensator have scale indications, and the initial zero position state: The flange spacing of the axial flow bellows compensator is 287 mm, and the spacing of the swirl flow bellows compensator is 281 mm. Combining the flame length diameter and the NO X emission data, the axial flow bellows compensator is adjusted to 297 mm, and the swirl flow bellows compensator is adjusted to 276 mm. By adjusting the bellows, the cross-sectional areas of the axial flow air and swirl flow air ports are changed, so that the distribution ratio of the primary air basically reaches: axial flow air flow: swirl flow air flow: central air flow = 60:35:5. The adjustments of the axial flow air opening and swirl flow air opening of the burner are as follows: The primary air fan is frequency conversion controlled. When the set frequency is 42.5 HZ after debugging, the fan speed is 833 r / min, and the air volume is 148 m 3 / min. Adjust the pointer of the axial flow bellows compensator +10 and the swirl flow bellows compensator -5. At this time, the combustion flame state, the burnout rate of pulverized coal, and the NO X environmental protection indicators reach the best state. The production is set at 1000 t / d, and the coal feeding amount is 6500 ± 50 kg / h.

[0035] After implementing the technical solution of the present invention, the temperature at the kiln head is increased by 44 °C, the operation is stable, the CO concentration is decreased by 3017 ppm, and the primary air volume is increased by 4823 m 3 / h. The burnout rate of pulverized coal in the kiln is significantly improved. The increase in the temperature at the kiln head makes the high-temperature bonding effect of lime powder better, and the powder rate in the kiln is reduced by 0.54%. After continuously debugging the speed of the primary air fan and coordinating with the adjustments of the axial flow air opening and swirl flow air opening of the burner, after optimizing the process parameters, comparing the quality and quantity of the 1# kiln production line, the output is increased by 112 t / t, and the quality is improved from secondary ash to primary ash. The average low calorific value of the pulverized coal on an air-dried basis is 6285 kcal / kg, and the fuel energy consumption is equivalent to saving 16 kg / t of raw coal.

[0036] The increase in the temperature at the kiln head makes the high-temperature bonding effect of lime powder better, and the formation of rings and nodules in the kiln is improved. After the transformation, the output is increased to 868 t / d, and the quality is primary ash.

[0037] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: They can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pulverized coal combustion method suitable for a kiln condition with a large amount of dust, characterized in that It includes the following: (1) Selection of primary air fans to match the primary air volume and pressure By increasing the primary air volume and pressure, the ability of the primary air to hold the pulverized coal is enhanced, and more secondary air is entrained to form a bright and powerful flame under the dust kiln condition, increasing the combustion rate; (2) Enlarge the outer tube diameter of the burner to increase the cross-sectional area of the flame. The improved pulverized coal burner includes a primary combustion-supporting air channel, an axial flow air channel and its regulating valve, a swirl air channel, a central air channel, a lift wave compensation regulating component, and an air atomization pipeline; in the burner, the outer tube diameter of the primary combustion-supporting air is φ350mm, the outer tube diameter of the burner is φ560mm, and the coal tube diameter is φ250mm; a regulating mechanism is provided in the burner.

2. The pulverized coal combustion method adapted to a large dust kiln condition according to claim 1, characterized in that: The regulating mechanism includes an axial flow air metal bellows compensator. When its spacing is shortened, the cross-sectional area of the axial flow air outlet is increased, the axial flow air speed is decreased, the flame is lengthened, and the pressure gauge reading drops; When its spacing is extended, the cross-sectional area of the axial flow air outlet is decreased, the axial flow air speed is increased, the flame is shortened, and the pressure gauge reading increases; The regulating mechanism includes a swirl air metal bellows compensator. When its spacing is shortened, the cross-sectional area of the swirl air outlet is increased, the swirl air speed is decreased, the flame is shortened, and the pressure gauge reading drops. When its spacing is extended, the cross-sectional area of the swirl air outlet is decreased, the swirl air speed is increased, the flame is lengthened, and the pressure gauge reading increases; The adjustment of the axial flow air metal bellows compensator and the swirl air metal bellows compensator is realized through the regulating mechanism. The axial flow air metal bellows compensator and the swirl air metal bellows compensator have scale indications. The allowable axial movement of the axial flow air is ±30mm, and the maximum adjustment amount each time does not exceed 5mm; the allowable axial movement of the swirl air is ±15mm, and the maximum adjustment amount each time does not exceed 3mm.

3. The pulverized coal combustion method suitable for a large dust kiln condition according to claim 1, wherein: The head structure of the burner is designed as follows: the shape of the axial flow air holes is a square groove, the number of square grooves is 32, and the size of the rectangular cross-section of the square groove is: length 22mm, width 12mm; the outer diameter of the axial flow air outer tube is φ560mm.

4. The pulverized coal combustion method suitable for a large dust kiln condition according to claim 1, characterized in that: The head of the burner is provided with a flame-concentrating cover structure to concentrate the flame without divergence, and the diameter of the flame-concentrating cover is φ514mm.

5. The pulverized coal combustion method suitable for large dust kiln conditions according to claim 1, characterized in that: The shape of the swirl air holes in the head structure of the burner is a spiral groove, the number of spiral grooves is 24, the width of the spiral groove in the zero position of the wave compensation regulator is 13mm, and the normal width of the groove reaches 16mm by adjusting the length of the wave compensation with a lead screw; the outer diameter of the swirl air outer tube is φ356mm.

6. The pulverized coal combustion method suitable for a large dust kiln condition according to claim 1, wherein: The primary air fan is provided by a Roots blower, with a wind pressure of 53.9 kPa and an air volume of 174.5 m 3 / min, so that the axial flow wind speed reaches 180 - 250 m / s.

7. The pulverized coal combustion method suitable for large dust kiln conditions according to any one of claims 1 to 6, characterized in that: The technical solution is as follows: (1) The combustion-supporting air enters the kiln in two parts to participate in combustion: one part is controlled by the primary air fan, which plays the role of concentrating the fire to form a reasonable flame shape and organizing the mixed combustion of pulverized coal fuel, and the other part is the secondary hot air exchanged through the vertical cooler; The limestone stone is preheated by the preheater and preliminarily decomposed, then enters the rotary kiln for further roasting and decomposition to produce incandescent lime, which falls into the cooler and accumulates. There is a secondary air fan below the cooler. The generated air cools the lime material layer evenly through the air caps. At the same time, the air is heated to become hot air. The hot air enters the kiln and enters the flame under the entrainment of the primary air of the burner to provide oxygen for the combustion of the pulverized coal; (2) Optimization of the cross-sectional area structure of the axial flow air of the burner: The designed maximum axial flow air speed can reach: 250m / s, and the adjustable range is: 180~250m / s; (3)Install a flame-concentrating hood on the burner: The burner is equipped with a flame-concentrating hood structure, so that when the pulverized coal is ejected, the flame shape will not spread and burn immediately. The flame is concentrated, and while mixing, it spirals backward, enabling the pulverized coal to be mixed and burned orderly and fully within a relatively long roasting zone, releasing heat energy evenly, and achieving good roasting effect; (4)Enlarge the size of the burner to increase the combustion rate: The outer air duct size of the burner is: Φ560mm, and the overall combustion cross-sectional area is increased by 38.7%. In the enlarged mixing columnar area, the mixing and combustion effect of the pulverized coal is improved, and the burnout rate can reach over 99%; (5)Adjust the process parameters during combustion: By adjusting the wave compensation to change the cross-sectional areas of the axial flow air and swirl air ports, the distribution ratio of the primary air basically reaches: axial flow air flow: swirl air flow: central air flow = 60:35:

5.

8. The pulverized coal combustion method suitable for a large-dust kiln condition according to claim 7, wherein: The primary air volume is 12-18% of the secondary air volume.

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