- Time:Jan 14, 2023
A. Causes of high heat consumption of rotary kiln
1. Reasons for high heat consumption.
(1) Preheating precalciner system, rotary kiln, grate cooler surface heat dissipation.
(2) Heat loss due to incomplete combustion.
(3) Heat loss due to elevated exhaust gas volume caused by system air leakage.
(4) Large raw material moisture, coarse fineness, inadequate heat exchange.
(5) Poor effect of spreading device, material dispersion is not uniform.
2. Ways to reduce heat loss
(1) Take insulation measures to reduce heat loss on the surface of the system.
(2) Maintain a low excess air coefficient with complete fuel combustion, reducing the heat carried by exhaust gases.
(3) Strictly control the fineness and moisture of coal powder to ensure complete combustion.
(4) Ensure stable coal feeding and eliminate incomplete combustion.
(5) Strengthen sealing and plugging to eliminate air leakage inside and outside the preheater system, air leakage outside the kiln head and kiln tail, and air leakage inside and outside the grate cooler system.
(6) Improve the efficiency of grate cooler and reduce the heat loss of grate cooler clinker.
(7) Reduce the heat loss carried by the exhaust gas.
(8) Reduce heat loss from kiln ash and evaporated (raw material and pulverized coal) moisture.
B. The collapse of precalciner kiln
1. Causes of collapsed material.
(1) Design or structural defects of the preheater or decomposer.
(2) Influence of raw material and fuel quality.
(3) The impact of production equipment and failures.
2. Effects of design or structural defects of preheaters or decomposers and measures.
(1) The air speed of hot air duct is too low, and it can be solved by increasing the air speed by adding shrinkage.
(2) The size of the kiln tail indentation is too large, and the air speed of the indentation is too low (28m/s～35m/s), reduce the size of the indentation to ensure the air speed of the indentation.
(3) The position of the spreader at all levels, the length and angle of the spreading board are not reasonable. Ensure that the material coming from the spreading board can be fully spread.
(4) The design space angle of the down tube is less than 55° or too many bends, the material filling rate is low, and the counterweight of the flap valve is too heavy. Find ways to solve the technical reform.
(5) Cyclone flat pipe or decomposition furnace gooseneck pipe accumulation of material. Solved by transformation.
(6) Preheater inner tube inserted into the depth of too little, too much inner circulation of materials caused by enrichment.
3. Impact of raw materials and fuel quality fluctuations and measures.
Harmful ingredients alkali, sulfur cycle enrichment, materials easy to burn sticky, coal powder incomplete combustion, etc. lead to cyclone inner wall crust or attached to the cyclone inner wall of the material collapse material. Solved by batching and process operation adjustment.
4. The impact of production operations and equipment failure and measures.
(1) Low temperature, long flame, low output and slow kiln speed at kiln opening lead to low duct air speed, which produces accumulation of material or enrichment in the preheater leading to collapse of material. Take the method of fast temperature rise, increase material and kiln speed to operate.
(2) Unbalanced kiln and furnace air volume, insufficient ventilation in the kiln, low air speed at the shrinkage, resulting in collapse of material. Adjust the kiln and furnace air volume to achieve balance.
(3) The feeding volume and coal feeding volume are unstable and easy to produce material pulse and short circuit, which leads to collapse material. Ensure the stability of wind and coal material. Inner cylinder damage, preheater system local lining across the fall leads to accumulation of material, resulting in collapse of material. Take corresponding measures to solve.
C. Blockage of preheater
1. Preheating system clogging when the "signs".
(1) The ash discharge valve is stationary.
(2) The negative pressure rises sharply in all places above the blocked parts, and the positive pressure appears in the parts below the blocked parts, with ash coming out of the stabbing holes and exhaust valves, poor ventilation at the kiln head, and fire coming out when it is serious.
(3) The temperature at the entrance of the exhaust fan, the exit of the first stage cylinder, the exit of the decomposer and the tail of the kiln rises abnormally, and even reaches or exceeds the dangerous temperature range.
(4) The negative pressure of the preheater cone is sharply reduced or the temperature of the downstream material is reduced. If found in a timely manner, the cyclone cylinder in a few minutes full of material powder, but to the kiln under the material is very little. When the amount of material blocking the kiln is too large, there will be a sudden collapse of material, material powder rushed out of the kiln to cause accidents.
2. Major areas within the preheating system that tend to clog.
(1) Four-stage cyclone C4 vertical flue and C4 cone. The two blockages are similar, mainly high temperature unburned coal particles and raw material deposits.
(2) Kiln tail smoke chamber indentation and kiln tail slope. The blockage is mainly crust material, which is hard after cooling and has high alkali content R2O.
(3) Five-stage cyclone C4 cone and the lower material pipe. The blockage is mainly crust material.
(4) The decomposition furnace and its connecting pipes. C4 cylinder and decomposition furnace connecting pipes have a lot of crusts in the blockage, some of them are very hard, and there are a lot of unburned coal particles on the crusts, and there will be open fire when blowing with high pressure wind.
3. Preheating system clogging cause analysis
(1) Process reasons: The deposits in the preheater and at the rotary kiln inlet contain high levels of sulfate base and chloride base, and the sulfate base contained in the kiln gas separates out due to molten coalescence and forms substances that combine with combustion substances and kiln ash. Such molten material forms a film on the raw material particles, deteriorating the flow and causing blockage in the preheater.
(2) Operational reasons: uneven feeding, raw material composition fluctuations, improper flame formation, reducing atmosphere in the kiln, incomplete combustion, etc. are likely to cause crust blockage in the preheating system.
(3) Equipment maintenance: air leakage at kiln tail seal, manhole, cold air gate, etc., preheater lining peeling, flap valve too tight and inflexible, etc. cause crust blockage in preheating system.
4. Processing method
(1) When blockage is reported, measures such as stopping the material, reducing coal and slow turning the kiln should be taken immediately.
(2) To detect the blockage situation and the blockage area.
(3) agreed to clear the plugging program, the organization of human and material resources unified action.
(4) If the blockage is mild and can be cleared with a little bucket, you can reduce coal appropriately and continue to turn the kiln; if the blockage is serious, stop the material and turn the kiln slowly at the same time.
(5) poke plugging available compressed air gun aimed at the blockage site directly barrel pounding.
(6) When clearing the plug should be based on the principle of "first down, then up".
(7) clear the plug to keep the preheater system is a negative pressure state, to facilitate the barrel plug.
(8) After the stabbing blocking is completed, carry out a detailed inspection of the preheating system to ensure that all levels of cyclones return to normal.
(9) Ignition, temperature rise and feeding.
5. Preventive measures.
(1) Strictly control the quality of incoming raw materials and fuels; reasonably match the wind, materials, coal and kiln speed, stabilize the kiln's thermal regime, and avoid fierce increases and decreases and big adjustments.
(2) Stabilize raw material composition, control kiln tail temperature, decomposition furnace outlet temperature, etc. Make the temperature match with the composition, prevent local overheating, prevent incomplete combustion of the kiln and the formation of reducing atmosphere, and then lock the air tightly by sealing the leakage points of preheater at all levels and flap valve to ensure the stability of the system working conditions.
(3) Reasonably set up stabbing holes, monitoring and alarm devices, air cannons, etc. in the parts frequently clogged with crust.
D. Utilization of low quality fuels
1. Low quality fuel
Low quality fuel refers to the fuel with high ash content and the heat output below 3000 calories/Kg. There are coal gangue, coal sludge, etc.
2. Utilization of low quality fuels
(1) It can reduce the consumption of high quality fuel and reduce the cost of coal consumption.
(2) Ash from poor quality fuels can replace clay or sandstone in raw material ingredients.
3. Combustion characteristics of poor quality fuels.
(1) low combustion temperature: less heat released by combustion in a unit of time, the heat dissipated towards the surrounding area increases, the actual combustion temperature decreases. First, the ash content of low-quality fuel is large, heating requires considerable heat, so that the combustion temperature is reduced; second, the volatile content of low-quality fuel is small, the ignition temperature increases, coupled with the effect of heat dissipation, the actual combustion temperature is reduced. Third, the total flue gas volume after combustion is larger: carbonate decomposition occurs simultaneously with combustion, and CO₂ escapes and mixes into the flue gas, so that the total volume of flue gas increases; CO₂ absorbs more heat than air, so that the actual combustion temperature after combustion decreases (when high quality fuel is burned, only when the flue gas enters the decomposition zone in the kiln, the decomposed CO₂ mixes into the flue gas and reduces its temperature, but does not affect the combustion temperature of the firing zone) .
(2) slow combustion: the decomposition of CO₂ in the material during combustion increases the amount of flue gas, the air preheating temperature is not enough (temperature field impact); due to the low calorific value of low-quality fuel, less volatile matter, ash, combustible materials and oxygen contact area is relatively reduced, the combustion rate is slowed down (concentration field impact).
4. Measures to utilize poor quality coal
(1) Fine grinding of pulverized coal to improve the combustion rate of pulverized coal.
(2) Enhance wind and coal mixing.
(3) Strengthening the cyclone and spouting effect of the decomposer.
(4) Strengthen homogenization to ensure the stability of calorific value and composition of poor quality coal.
(5) Increase the temperature of the second and third air.
E. Kiln tail temperature is too low
F. Kiln tail temperature is too high
G. Operation of the kiln main transmission load reading
The current and power consumption of the kiln motor provide information not only about the calcination but also about the crusting condition. Slight fluctuations indicate normal and uniform crusting, however, large fluctuations indicate uneven crusting or crusting on one side, and the kiln current curve narrows or widens accordingly. The kiln drive current is a function of kiln speed, feed rate, crust condition, kiln heat and the amount of liquid phase in the material and its liquid phase viscosity, which reflects the overall kiln condition and represents much more than any other parameter.
(1) The kiln drive current is smooth and the kiln curve is flat. This indicates that the kiln system is smooth and the thermal regime is stable.
(2) The kiln current curve is fine, indicating that the kiln skin is flat or uneven but the torque applied to the kiln in the kiln drive process is balanced.
(3) The kiln current curve is coarse, indicating that the kiln skin is not flat or, the torque applied to the kiln in the kiln drive process is cyclical.
(4) The kiln drive current suddenly rises and then gradually decreases, indicating that there is kiln skin or kiln circle across the kiln. The higher the rise, the more kiln skins or kiln rings fall across. Most of the cross-fall occurs between the kiln mouth and firing zone. In this case, we should reduce the kiln speed according to the rising curve, and at the same time, reduce the feeding quantity and decomposer fuel appropriately, and then take further measures according to the speed of the falling curve. At this time, the grate speed of the grate cooler is accelerated and the material layer is pushed thin. After the curve turns and then gradually increase the kiln speed, feeding amount of decomposition furnace fuel, etc., so that the kiln turns to normal. If this situation is not handled properly, the material will be burned, grate cooler overload or temperature is too high so that the grate plate damage and other adverse consequences.
(5) The kiln drive current remains high. First, the kiln is overheated, the firing zone is long, the material is brought high in the kiln, at this time to reduce the system fuel. Second, the kiln is long kiln ring, the kiln material filling rate is high, thus causing bad material caking, from the grate cooler back to the kiln powder increase. This situation should be appropriate to reduce the amount of feeding and take measures to burn before the circle. Third, poor material granulation performance. As the material sticky scattered, the material from tumbling to sliding, so that the kiln rotation trapped which is difficult. Fourth, the kiln skin thick, kiln skin long. This time to shorten the flame, shorten the firing zone.
(6) Kiln current is very low. First, the kiln under-fired serious, close to run raw material. Second, the kiln after the knotted circle, the material gathered after the circle to a certain extent rushed into the firing zone, resulting in a short firing zone, the material burned sharply, easy to knot large blocks. Clinker more yellow heart, free calcium is also high. Third, the kiln skin is thin and short, this time to stretch the flame and properly extend the firing belt.
(7) The kiln drive current gradually increases. First, the kiln tends to high temperature. If the original clinker under-fired, it indicates that the kiln is tending to normal; if the original kiln firing normal, it indicates that the kiln is tending to overheat, should take measures to add material or reduce fuel to adjust. Second, the kiln began to long kiln ring, the material filling rate gradually increased, the firing zone of the sticky loose material in the increase. Third, the long thick kiln skin is forming.
(8) The kiln drive current gradually decreases. First, the kiln tends to move toward lower temperatures. Adding material or reducing fuel can produce this result. Second, this can also occur with an increase in discharge after the kiln skin or front ring span falls.
(9) kiln drive current suddenly dropped this situation also has two causes, first, the preheater decomposer system collapse of a large number of materials without good preheating suddenly into the kiln, resulting in each belt forward kiln forced to burn, or run raw material. At this time, to take measures to reduce the kiln speed to properly reduce the amount of feeding, and gradually return to normal. Second, large pieces of crust fall on the slope of the kiln tail blocking material accumulation to a certain extent, suddenly a large number of kiln into the same impact as the first case, while large pieces of crust also hinder ventilation fuel combustion is not good, the system temperature is low will also make the kiln drive current low.
H. Causes of laps and balls in the kiln
1. Causes of laps and balls in the kiln.
(1) Raw material into the distribution ratio is not appropriate, the saturation ratio is too low and the silicic acid rate is too low, forming too much liquid phase amount, in the decomposer temperature, kiln end calcination temperature, flame control and kiln speed is not appropriate, the formation of material balls or kiln knots.
(2) The ash content of the coal is too high, coupled with the position of the burner and improper control of the flame shape, causing the kiln to be caked with circles or balls of material.
(3) Unstable control of the thermal system, resulting in large changes in kiln conditions, i.e., large fluctuations in high and low temperatures, resulting in the formation of circles or balls in the kiln
2. How to deal with the knotted circle and knotted material ball in the kiln.
(1) Reduce the fineness and moisture of coal powder.
(2) Move the position of coal injection pipe and change the position of coal pipe settlement to increase the temperature fluctuation.
(3) Raise the SM of raw material out of the mill, part of raw material out of the mill directly into the kiln, stabilize the composition of raw material into the kiln; lower the temperature of the decomposer, lower the temperature of the kiln tail, and delay the appearance of liquid phase.
(4) Move the position of the coal injection pipe at regular intervals to increase the temperature fluctuation.
(5) The material ball treatment depends on the situation, for smaller material balls can fall directly into the grate cooler. If the ball is too large than the effective radius of the kiln, cease fire before the ball reaches the burner nozzle and let it fall into the grate cooler for secondary manual processing.
I. Flame brush kiln skin causes and solutions
(1) The position of the burner problem. Readjust the burner.
(2) The shape of the flame is not appropriate. The internal wind is too large flame dispersion caused by brush kiln skin to be adjusted.
(3) There is a foreign body at the burner nozzle. Perform cleaning.
(4) There is coking at the burner nozzle. Carry out cleaning.
(5) or casting material off resulting in burner nozzle deformation. Re-repair and replace.
J. Kiln cylinder high temperature, red kiln solution
(1) Confirm the high-temperature parts and notify the site to measure the actual temperature with a thermometer to have a good idea.
(2) Forced cooling by axial flow fan.
(3) If the high temperature is in the firing zone, take measures such as elongating the flame, changing the position of the fire point, and properly reducing the kiln head coal.
(4) Red kilns are treated differently in two cases.
① One is that the red spot appeared by the cylinder is dark red and appears in the area with kiln skin, this situation is caused by collapsing kiln skin, at this time, you should continue to run, while adjusting the flame shape to avoid the highest point of flame temperature in the red kiln area; the axial flow fan of the kiln cylinder is aimed at the red kiln position to blow so that the temperature of the kiln cylinder is reduced.
② Red spot for bright red or appear in the area without kiln skin, this situation is generally due to the kiln lining off, this situation must immediately stop the kiln, if the large area of the brick, in order to prevent the deformation of the cylinder, you can first stop coal after stopping the material, and let the main motor run for a period of time, while the axial fan focused on the red kiln location blowing, so that the cylinder temperature drops rapidly, the red spot from bright red to dark red, and then continuous pan car kiln, and make a good red kiln location mark, ready for maintenance.
(5) to prevent red kiln, the key is to protect the kiln skin. Protection of kiln skin, from the perspective of operation, to master reasonable operating parameters, stable thermal system, strengthen the calcination control, avoid burning fire, top fire burning, strictly prohibit the burning flow and run raw material. Raw material composition of the kiln from difficult to burn material to easy to burn material change, when the coal powder due to the transfer of the stack of reasons from low to high calorific value, to adjust the relevant parameters in a timely manner, appropriate to reduce the amount of coal feeding, to avoid the kiln temperature is too high, to ensure a stable transition of the thermal system. In addition, we should try to reduce the number of kiln starts and stops, because the damage to the kiln skin and lining material is great when the kiln starts and stops, to ensure the long-term stable operation of the kiln, which will make the life of the kiln refractory material greatly improved.
K. Kiln skin maintenance measures
(1) The heat load in the kiln should not be too high and should be stable. Once you find burning high temperature, reverse it quickly.
(2) Pay attention to adjust the flame so that the flame position, shape, direction and length are reasonable.
(3) Pay attention to the change of incoming material volume, wind and coal fluctuation. Pay attention to the changes of material composition and coal quality, pay attention to the f-CaO test results and take corresponding countermeasures.
(4) The central control operator should protect and replenish the kiln skin by adjusting the flame, air temperature, air volume and coal feed according to the location of the highest temperature point shown on the kiln carcass temperature scanner, the length, thickness and uniformity of the kiln skin.
(5) firing with kiln skin renewal period or carcass high temperature, especially to strengthen the operation, do not burn high and burn low temperature, so that the kiln condition aggravated deterioration, should be timely replacement hanging kiln skin.
