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Optimization of calcium carbide slag drying system in cement

 lvssn group second-line 3000t /d production line was put into production in December, 2011. Calcium carbide slag produced by chemical plant dry production of acetylene was used as limestone raw material, and the slag had less moisture (about 6%), which was directly used for raw material batching after drying in the drying system.In the process of production, there are some problems in the calcium carbide slag drying system, which affect the stable operation of production.

  Calcium carbide slag drying system

  The drying process of calcium carbide slag is shown in figure 1. The calcium carbide slag is fed into the dryer through the belt conveyor and Fu zipper machine from the reservoir, mixed with the hot air from the end of the kiln of the humidifying tower and dried in the dryer. The moisture is reduced to less than 2%, and then collected by the efficient cyclone separator on the top of the calcium carbide slag dry powder warehouse.The unloading system (grillers, screw conveyors and hoists) set at the lower part of the dryer carries large pieces of sundries and ferrosilicon to the ferrosilicon silos and then through the vehicle exhaust.The humidifying pipe is set on the outlet preheater pipe. When the gas temperature of the electric precipitator entering the kiln tail is too high, the spray device can be opened to reduce the gas temperature.The powdered material collected at the bottom of the humidifying pipe goes into the raw material homogenization library together with the finished raw material powder from the raw material mill.
 

  analysis of existing problems and causes

  1) at the beginning of the production and operation of the spray humidifying pipe cause the humidifying effect is bad, humidifying pipeline caused by pipeline collected a large number of wet material cones installation frame round often jammed, can enter library of raw meal homogenization, wet material needs a large number of outside, causing the waste of material, system air leakage is very serious, at the same time affect the thermal stability of the firing system.

  2) firing system thermal instability or preheater high temperature fan can lead to dry out of system pressure is small, the time delay of carbide slag conveyor equipment downtime that carbide slag are still enter the dryer, coupled with carbide slag in the dryer, originally collected a large amount of calcium carbide slag can not be timely dry, piling up in dryer cones, cause jams, wheel frame jammed, can't eduction of carbide slag.This aggravated the thermal fluctuation of the burning system, affected the output of calcium carbide slag powder, cleaning up more trouble.

  Measures and effects taken

  Replace the grid-wheel under the humidifying pipe and dryer with the flap lock air valve;A new screw conveyor is added to transport the materials collected by the humidifying pipe to the screw conveyor at the lower part of the dryer, and the original humidifying tower is stopped to the Fu zipper machine in the raw material homogenization library.Replace the grid wheel before calcium carbide slag enters the dryer with a rotary filter cake feeder to ensure the stability of the amount of added wet calcium carbide slag;A three-way feed valve is installed at the elevator exit into sife silos, which directly enters sife silos all the way, and a rotary unloader is installed all the way to send some materials to the dryer again.

  After optimization, when the spray device in the humidifying pipeline fails or the humidifying effect is not good, the wet materials in the humidifying tower can be sent to the dryer for drying again through the newly added screw conveyor, three-way material distributing valve and rotary unloader, so that the materials can be fully utilized and the air leakage in the system can be reduced at the same time.Due to the humidification pipe collection of materials relative to calcium carbide slag powder, the amount is very small, the impact on raw material ingredients can be almost negligible.The flapper valve under the newly added dryer can discharge the materials inside the dryer smoothly when the high-temperature fan stops and the negative pressure of the system decreases.The newly added three-way material separation valve can feed the materials inside the conveying equipment into the dryer to form an internal circulation through the bucket elevator when the high-temperature fan fails to operate, so as to avoid the material clog up in the cone of the dryer, and purify the silicon and iron in the external discharge materials to avoid the inclusion of too much calcium carbide slag dry powder.

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