Preheater measures to reduce collapse

Date: 2019-07-26 Views:

In the calcining process of rotary kiln, the wind and materials in the system do not match, leading to accumulation of materials in the preheater (but not completely blocked), and sudden collapse of materials to a certain extent causes an accident, and at the same time, the high-temperature fan turns around.
 

1. Strictly control the water content of raw material coming out of mill and stabilize the amount of raw material feeding into kiln


The uniformity of raw material composition is an important factor to determine the quality of cement clinker.But out of the ground raw water is too big, not only make the raw meal homogenizing library roof chute easy jam, library wall adhesion, reduce the effective volume of homogenization library, center at the bottom stirring indoor channel flow phenomenon is seen, raw material is not fully fluidization, directly affect the raw meal homogenizing effect, and high moisture of raw materials in the preheater feeding of small easy also bulging, raw uneven whereabouts or landslides, the feed rate of decomposition of entering the preheater system more and less, easy to cause the collapse.Therefore, the raw material moisture should be strictly controlled at 0.5%.

With uniform composition and smooth flow of raw material, if the quantity of feed is not timely, inaccurate measurement is difficult to stabilize the quantity of raw material feed into the kiln, ensure the stability of the kiln system thermal system and fired high quality cement clinker.At present, most of the large and medium-sized new dry method cement factories in China generally use weighing warehouse with shenke electronic belt scale raw material feeding material measurement system or use Japanese powder to study the rotor scale, they not only measure accurately, the amount of material can also be timely control, in operation rarely collapse material phenomenon, clinker quality is relatively high.But most small and medium-sized new dry method cement plant, because of the conditions, the raw material into the kiln feed quantity generally fluctuates greatly, plus the operation is not allowed, the pre-decomposition system collapse material frequently, the kiln speed does not rise, the firing system thermal system is not stable, the clinker production quality is generally low.For the cement factory, little in raw water and the surface of the material feeding capital under the premise of basic constant, if the two pipe screw feeder of the electromagnetic speed motor with frequency conversion speed governor control instead of asynchronous motor and remove air lift pump flow's influence on the measuring equipment, feeding precalcining system of shoes can tend to be more uniform.Further strengthen the job training, change the operation method, system collapse phenomenon and clinker production quality can be improved.

 

2. The horizontal section of the cyclone cylinder is inclined to avoid material accumulation


With the development of NSP technology, each design unit in China has developed its own pre-decomposition system.But the cyclone tube volume is small, the resistance is low, the preheating effect is good is everybody pursues the common goal.Some have changed the inlet of the cyclone cylinder and the bottom of the vortex shell to a certain degree of inclination, thus eliminating the possibility of large amount of material accumulation.However, some of them are still unchanged, especially the pre-decomposition kiln production lines built in the early stage, which mostly retain the inlet of the cyclone cylinder and the horizontal section at the bottom of the vortex shell.It is suggested that these cement plants appropriately increase the wind speed of the inlet of the cyclone tube and change the inclination Angle of the bottom of the vortex shell to ≥45°, so that the material collapse of the system will certainly be reduced.

3. A conical expansion bin is arranged below the outlet of the cyclone cone


The conical expansion bin set below the conical cone of the cyclone drum can enlarge the diameter of the cone outlet, thus effectively reducing the possibility of the material stacking and arching at the bottom of the cone.In addition, the section of the expansion warehouse is larger than that of the outlet of the cyclone cylinder cone, and the material enters the expansion warehouse because of its sudden expansion of the section, the falling speed of the material slows down, playing a buffer role.It can also reduce the negative pressure inside the discharge valve and discharge pipe, which is helpful to alleviate the phenomenon of material collapse caused by internal and external air leakage.
 

4. Reasonably adjust the Angle of the ash discharge valve stem and its counterweight


The function of ash valve is both lock air and blanking.However, if the valve stem Angle and its weight is not appropriate, either the valve plate is easy to pile up material caused by blockage, or the valve plate is not in place to produce large internal air leakage.According to the author's experience, the position of the valve balance bar should be below the horizontal line and the included Angle between the horizontal line is less than 30°, the best can be adjusted to about 15°.Because at this time, the line displacement of the balance bar center of gravity changes little, and with the increase of valve plate opening, the center of gravity and axis spacing of the balance bar increase at the same time, torque increases, and the time required for valve plate reset is shortened.As for counterweight, should be in cold state at the beginning of the tune, tune to lift the balance bar gently with the hand up, a let go of the hand balance bar reset, hot state only to individual ash valve can make micro adjustment.This kind of ash discharge valve balance bar swing small frequency, both in time to discharge and reduce air leakage, collapse of the phenomenon can be improved.
 

5. Jump over low-yield collapse hazards as soon as possible


The biggest characteristic of the preheater decomposing kiln production process is that about 60% of the fuel is burned in the decomposing furnace, and the raw material temperature can reach 830 ~ 850℃ in general, and the decomposing rate can reach more than 90%.This creates favorable conditions for fast rotary kiln, thin material and long flame calcining.Therefore, the starting point of NSP kiln feeding should be high, generally no less than 60% of the designed output.Gradually increase the feeding amount, but try to avoid delaying the running time of low feeding amount.In the stage of gradually increasing feeding quantity, the key is to master the relationship between wind, coal, feed and kiln speed. The operation step should be to lift the wind first, add coal, lift the kiln speed first, and then feed.

Initial feeding range can be appropriately larger, 80% of the feed after appropriate slowdown.As long as the system's thermal parameters are at the upper limit of a reasonable range, operate boldly.In this way, even a large scale NSP kiln can be added to the designed feeding quantity within 1h.In general, the amount of feeding to 80% of the design value is relatively stable.Under normal conditions of kiln skin, the maximum yield can be achieved within 1h after feeding.If the feeding quantity below 70% is the danger zone of collapse, then the feeding quantity will increase from 60% to 70%. It only takes a few minutes to skip this danger zone, and then the kiln condition will tend to be stable.Then quantificationally in precalcining system has reached a certain degree, the material flow is smooth, cyclone tube cone discharging mouth, ash discharge valve and the discharge pipe through a large number of material at any time, for the above parts of the air leakage and air leakage and inhibition effect, so rarely fall, even if have also is very small, there is no effect to the operation.So people say that the higher the yield of the NSP kiln, the easier it is to operate.

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