It is very important to adjust the rotating speed of the sand dryer. In general, the rotating speed of a sand dryer is quite low. Besides, the serious air leakage will cause that the negative pressure inside the drying drum is too low. In the high-temperature segment of the drying drum, the thermal storage temperature is increasing, which will cause that the sand dryer can not be in the normal operation. At this time, if the original speed is kept or the charging quantity of sand is not adjusted well, the thickness of the material flow will not change and the venting capacity of the drying drum for the material flow can not be improved, which will lead to a vicious circle. Thus, in order to change this kind of operating condition, the only method is to increase the rotating speed of the sand dryer. Meanwhile, the charging quantity of ores should stay the same and the rotating speed of the chain grate should not be changed.
In the actual operation of the sand dryer, the blast volume used to spray coal powder at a time is very low. The coal powder sprayed into the heating device can not be burnt completely, which will cause that the flame at the head of the furnace of the sand dryer is too short and that the black flame front is too long. And the not burnt coal powder and coal ash will fall into the high-temperature segment, which may form furnace accretion. Therefore, the venting volume of the sand dryer at a time must be increased. However, it will cost a lot to replace a air blower. Thus, the hot blast used to dry coal powder can be connected with a blast pipe in series, which is beneficial to fire the coal powder completely and to change the shape of the flame. Besides, the period of forming the furnace accretion for a sand dryer will be prolonged.
After the increase of the rotating speed of the sand dryer, the thickness of the material flow in the sand dryer will decrease, the venting capacity of the drying drum can be improved, and the material flow area will increase. And the decomposition of carbonate will be accelerated. Besides, the duration of stay of the furnace burden inside the sand dryer will be shortened. And the calcining temperature will decrease. The incomplete combustion or over burning can be reduced. And the furnace accretion will decrease accordingly.
