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Cement kiln central control operation intermediate worker training materials (2)
  • Time:Feb 02, 2023
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XVI. Briefly describe the operating principles of the firing system

      During the operation of the firing system or during the process of increasing production, attention should be paid to the principle of raising air first and then adding coal; in case of production reduction accidents, safe and active, rapid transition, and thin material fast burning, the specific operations are as follows:

      1. In the process of raising temperature and feeding or increasing production, we should pay attention to the principle of raising air first, then adding coal; in the stage of reducing production and speed, we should first reduce material, coal, and then reduce air, so as to prevent the system from collapsing and clogging .

      2. Since the decomposition system of the preheater responds sensitively to the operating parameters, the operator is required to have the good quality of quick response, accurate judgment and quick action, otherwise the system operation will deviate from the normal operation requirements. When it is serious, it will lead to major accidents and affect production.

      3. At the initial stage of ignition and feeding, attention should be paid to the occurrence of skinning in the kiln tail smoke chamber. The up and down movement of the rotary kiln will cause the sealing problem of the kiln tail and the red kiln of the kiln shell after production.

      4. Pay attention to the position of the kiln coal injection nozzle and the adjustment of the flame to form a reasonable firing environment in front of the kiln. It is necessary to avoid burning flow caused by excessive temperature in front of the kiln, and the phenomenon of undercooked burning and intermingling should not occur. At the same time, pay attention to the shape of the flame so as not to scour the kiln skin.

      5. In the process of production and operation, attention should be paid to the control of the outlet temperature of the calciner. If it is too low, it will increase the burden on the rotary kiln and cause frequent running of raw materials. If it is too high, it will easily lead to the premature appearance of intermediate minerals and liquid phase components, resulting in crusting and blockage.

      6. For off-line furnaces, during the transition from SP to NSP system, attention should be paid to the steady increase of fuel in the two-way combustion of C5-level cylinder materials and kiln tail. Avoid fuel and material pulses and local overheating; the online calciner can be directly put into NSP operation.

      7. Strengthen the management and control of the cooling machine, so as not to cause large changes in the air volume and air temperature in the second and third times, which will affect the combustion in the kiln.

      8. The operating process of the system should be based on the principle of balance and slow down adjustment. Pay attention to the changes and speed of each parameter. If the speed of change is large, it means that the operation is not suitable, and the production control parameters should be avoided.

XVII. What are the automatic control loops in the general firing system

      The main automatic control circuits of the general firing system are: automatic control circuit for feeding and weighing bin weight, automatic control circuit for kiln feeding amount, automatic control circuit for coal injection amount, automatic control circuit for temperature of materials entering the kiln in the lowest stage of cyclone , kiln head coal injection volume automatic control circuit, kiln head negative pressure automatic control circuit, grate cooler cooling air volume automatic control circuit, grate cooler first chamber (or second chamber) grate pressure (material layer thickness) automatic control circuit, grate cooler The automatic water spray control circuit of the machine, the automatic control circuit of the grate speed of each section of the grate cooler, the automatic control circuit of the water spray of the humidification tower, and the automatic control circuit of the pulverized coal bin.

XVIII. What are the key control parameters in the normal operation of the firing system

      The key control parameters in the normal operation of the firing system are: kiln host current, high-temperature fan inlet temperature and inlet and outlet pressure, outlet pressure and temperature of the first-stage cylinder, pressure and temperature of the lowest-stage cyclone cylinder, outlet and feeding pipe temperature and Pressure, temperature and pressure of cyclones at all levels, kiln tail temperature and pressure, gas analysis data at kiln tail and preheater outlet, grate cooler first and second chamber grate plate and lower grate temperature, grate cooler each section current, The current of the grate cooler, the clinker temperature of the grate cooler, the secondary air temperature of the kiln, the tertiary air temperature of the kiln, the negative pressure of the kiln head, the negative pressure of the tertiary air of the kiln, the feeding amount of the kiln, and the current of each conveying equipment , the amount of coal injection at the kiln head and kiln tail, and the pressure and current of the Roots fan, the inlet temperature of the residual air fan at the kiln head, the temperature of the kiln supporting wheel, the temperature of each point of the coal powder bin, the decomposition rate of the kiln, the clinker vertical weight and f-CaO content, kiln carcass temperature, high temperature fan, residual wind fan current, high pressure air pressure.

      Due to the different process conditions of each enterprise, the control indicators of process parameters are slightly different.

XIX. What is the adjustment principle of the air volume of the firing system

      The adjustment of the primary air volume at the kiln head should be based on the principle of maintaining a suitable flame shape and temperature distribution to meet the needs of clinker firing; The principle is to maintain an appropriate air ratio for the kiln and furnace, and proper ventilation in the kiln; the adjustment of the total exhaust air volume should meet the needs of raw material suspension and fuel combustion, and the principle is to maintain an appropriate excess air coefficient of the kiln and furnace.

XX. What is the adjustment principle of kiln speed

      The adjustment of kiln speed should be based on the principle of maintaining a stable and reasonable filling rate in the kiln; an appropriate kiln speed should be determined according to the feeding speed and the difficulty of firing, which should correspond to the feeding amount and increase or decrease with the feeding amount And increase or decrease, under the same feeding amount, the kiln speed should be higher or higher, and the fast rotation is beneficial to increase the turning frequency of the material, which is beneficial to the pre-burning and firing of the material; when only adjusting the coal and wind does not restore the normal calcination system or When the firing temperature is too low and it is too late to raise the temperature, the kiln speed should be lowered in time to meet the calcination requirements; when the firing temperature rises, the kiln speed should be raised in time to avoid the long-term slow kiln causing the kiln to burn. Increased material filling reduces heat transfer efficiency, reduces clinker output, and affects clinker quality.

XXI. What is the reason for the sticky bulk material in the kiln? how to operate

      1. Causes of sticky bulk material:

      (1) Improper composition of raw materials, too high n value, and small amount of liquid phase make the materials diverge

      (2) The Al₂O₃ or alkali content in the raw material is high, or the coal ash content is large, so that the Al₂O₃ content in the clinker is high, and the material is sticky.

      (3) The operation is unreasonable, the tail temperature is too high, the material is pre-fired too well, and after entering the firing zone, the material is too hot and sticky.

      (4) kiln ring.

      2. Operation processing

      (1) Appropriately increase the content of Fe₂O₃ in the ingredients.

      (2) Appropriately increase the wind in the kiln to increase the volatilization of alkali.

      (3) The firing temperature should be well controlled, and the clinker should be fine and uniform. On the premise of controlling f-CaO not exceeding the index, reduce the amount of coal used at the kiln head and reduce the temperature of the firing zone.

      (4) Appropriately increase the kiln speed to reduce the residence time of materials in the firing zone. If the front ring is high, the front ring should be burned first to make the material run smoothly.

XXII. What kinds of methods are generally adopted to deal with the kiln back circle? what should be paid attention to

      1. After processing, ring formation generally adopts ring burning method, including hot burning method, cold burning method and alternating hot and cold method.

      2. The problems that should be paid attention to after processing are:

      (1) During hot firing, the firing temperature should be higher than normal, the flame should be longer, the fire point should extend inward, and the kiln speed should be slower; during cold firing, the firing temperature should be slightly lower, and the flame should retract, and the fire point should move toward the kiln head. , The kiln speed should be as fast as possible; the alternating cold and hot method is to alternately carry out cold firing and heating, so that the temperature at the ring formation will have a large change, and the ring formation will collapse.

      (2) When burning rings, attention should be paid to the flame shape not sweeping the kiln skin.

      (3) When burning rings, the central control should closely cooperate with the kiln inspectors to coordinate operations. The movement of the fire point can be realized by adjusting the ventilation in the kiln, adjusting the position of the coal injection pipe at the kiln head and the ratio of the internal and external air valves.

XXIII. How to hang kiln skin

      According to the theory of hanging the kiln skin, the key is to hang the first layer of the kiln skin. The time for hanging the kiln skin is generally 72 hours (3 days). Within 3 days, the amount of cutting materials should be reduced to lower the output. The first day is the design 70% of the yield, 100% the next day. Before the material enters the firing zone, the surface of the refractory brick must be melted to make the material form small particles and stick to the refractory brick to hang on the first layer of kiln skin. During this period, it must be carefully observed, frequent operation, timely adjustment, and familiar The particles of the material should be fine and uniform, and the temperature difference between the material and the kiln skin should be kept small to maintain the position of the kiln skin. Uniform and stable kiln skin. The inside of the kiln must be kept clear, the flame should be kept lively and smooth, and it is strictly forbidden to burn the kiln.

      After 3 days, hang the kiln skin to be equal to the etched kiln skin, and the thickness of the kiln skin is preferably 150-200 mm.

XXIV. What are the symptoms of blockage of the preheater cyclone cone or the feeding pipe? What are the causes of blockage? What are the ways to prevent blockage? How to deal with the blockage

      1. Symptoms of cyclone cone blockage: the gas temperature from the clogged cyclone to the kiln tail rises significantly; the clogged cyclone cone pressure drops significantly to zero pressure.

      2. Causes of blockage: The blanking flap valve does not flicker or is stuck by hard objects, the cone is stuck by foreign objects, the crust is not cleaned in time, a large number of collapses occur when the temperature fluctuates, and improper operation causes super-high temperature materials to stick together , The draft is too small, the swirling speed is low, the cone bulk material is not washed away, the concentrated large slump is blocked, the chemical harmful components of the raw meal are too high or the chemical composition of the raw meal fluctuates too much, the system design is unreasonable, the system There is more air leakage.

      3. Ways to prevent clogging

      (1) Strengthen the inspection of the system to avoid unnecessary blockage caused by equipment failure.

      (2) Operate in strict accordance with the parameters of the production process to avoid the existence of local high temperature phenomena and fluctuations in thermal operating parameters, so as to eliminate the blockage caused by local bonding caused by thermal action.

      (3) Control of harmful chemical ingredients. Strictly control the content of harmful chemical components in raw materials (K₂O+Na₂O, SO₃, Cl, etc.), and pay attention to the changes in the three ratios of raw materials and MgO content, and take corresponding actions according to the changes.

      (4) In the process of production operation, it is necessary to avoid the operation and control of drastic ups and downs, and the steady increase or decrease of wind, coal and material must be achieved to overcome the blockage caused by excessive feeding.

      (5) Avoid blockage due to poor ventilation in the preheater system and incomplete combustion of pulverized coal.

      (6) Pay attention to check the air leakage of the system on site.

      4. The treatment method after the blockage occurs

      (1) Judgment of the degree of internal blockage. After the preheater system is clogged, it is necessary to judge the clogging of the contents of the cyclone according to the length of the clogging time. Before the internal situation is clear, the larger access door must not be opened. When observing, it should be inspected step by step from the height of the cyclone downward and from the smaller observation hole. During inspection, inspectors must wear safety protective clothing to ensure personal safety.

      (2) In the process of unclogging, under normal circumstances, the high-temperature fan must work to ensure that the preheater is in a certain negative pressure state. But it should not be too large, so as not to cause the temperature in the kiln to drop too quickly.

      (3) The location of the preheater should be at the bottom of the blockage, and it should be cleaned up gradually, and all flap valves below the blockage should be lifted, and remember not to open the valve end cover at will.

      (4) When dealing with faults, the kiln should be in the slow rotation position to prevent deformation of the kiln body. Inform the relevant posts at any time to pay attention to safety, to prevent material rushing and cause burns. Special attention should be paid to the safety of personnel at the cooler and the underground clinker bucket conveyor.

      (5) Before cleaning, all observation doors below the material hole must be closed.

      (6) Use compressed air blowing plugging method. When using this method, the processing personnel must wear safety protective clothing and gloves, and must insert the rod into the inside of the preheater or the depth of the material before turning on the compressed air for processing.

      (7) Use the water cannon method to deal with. When using this method, insert the iron pipe for the material (the head should be smashed into the small hole of Φ5-8mm) into the deep part of the blocking material, and the pipe should be fixed as necessary. The other end of the pipe is equipped with a pressure-resistant rubber hose and connected to a high-pressure water valve (remember not to allow water to flow into the metal pipe). After all personnel evacuate from the scene to a safe place, quickly open the high-pressure water valve to complete the process of discharging the water cannon. The water cannon can be repeatedly released according to the situation until the blocking problem is cleared.

      (8) Professional high-pressure "water jets" can also be purchased for blockage removal operations.

XXV. A brief introduction to the phenomenon, causes and countermeasures of "egg laying" in the kiln

      1. The obvious phenomenon of "egg formation" in the kiln

      (1) The flame is stubby and unstable, and the airflow in the kiln is not smooth.

      (2) The temperature at the kiln tail decreases, and the negative pressure at the kiln tail fluctuates greatly.

      (3) The negative pressure at the kiln head decreases and the fluctuation increases.

      (4) The firing belt is uneven and fluctuates greatly.

      2. Causes of "egg formation" in the kiln

      (1) Improper ingredients, low SM and IM, large liquid phase volume, and low liquid phase viscosity.

      (2) Unsatisfactory homogenization of the raw material, large fluctuations in the chemical composition of the raw material entering the kiln, resulting in unsteady coal consumption and unstable thermal system. At this time, it is easy to cause the kiln skin to stick and fall off, and the kiln skin is not easy to maintain during firing It is flat and firm, and it is easy to cause large eggs.

      (3) The amount of feed is unstable, the pulverized coal is not completely burned, and the coal ash is unevenly mixed into the material.

      (4) The flame is too long, the fire head moves backward, the local high temperature behind the kiln, and the temperature of the decomposition furnace is too high, so that the liquid phase appears in advance of the materials entering the kiln.

      (5) Coal has high ash content and coarse fineness.

      (6) Harmful ingredients (alkali, chlorine) in raw materials are high.

      3. Countermeasures

      (1) When eggs are found in the kiln, the draft in the kiln should be appropriately increased to smooth the flame to ensure that the pulverized coal is completely burned, and the kiln should be reduced to slow down the kiln, so that the large eggs can "climb" up the kiln skin and enter the firing zone. The big fire burns the large eggs or burns them small, so as not to block the grate cooler or smash the grate plate, and at the same time, prevent the large eggs from damaging the coal injection pipe.

      (2) If it has entered the grate cooler, the material should be stopped in time, the kiln should be stopped, the large eggs should be stopped in the low temperature area, and manually broken.

      ZHENJIN REFRACTORIES is committed to one-stop general contracting services such as research and development, technical solution design, construction and supporting product provision of refractory materials in the cement, lime, non-ferrous, steel, glass and chemical industries. Kiln overall solution service provider. The service chain runs through the entire life cycle of the project, including preliminary consultation, scheme design, R&D and production, furnace construction and safety production. Through the optimized combination of various brand products, it can meet different process requirements and create value for customers.

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