Power requirement for mixing powders in a rotary vessel type mixer has been analyzed by introducing a simplified model, which regards the vessel shape of the three dimension as that of two dimension. The total force exerted on the mixer's shaft by the charged powders is assumed to be the sum of; (i) the gravitational force by the powders bed, (ii) the inertia force for accelerating the powders mass, and (iii) the frictional force acting between the powders bed and the inside wall of the mixer.
Horizontal drum, twin shell (V) and double cones type mixer are used in this work.
Power equations were obtained as the function of the operating conditions, the propertied of the powders and the dimension of the mixers. An agreement within an accuracy of ±20% was obtained between the measured power and the one calculated by these equations.

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There are three methods to control pressure loss across a fabric filter, i.e., timer type, one point pressure switch type and two points pressure switch type.
It is well known that the outlet dust concentration of a fabric filter increases remakably just after the cleaning operation.
Therefore in this paper, the number of cleaning cycles per unit time for each method by using a mathematical model are calculated. A first order lag model can be applied to express the dynamic characteristics between pressure loss amplitude of a timer type and frequency of inlet dust concentration. In the timer type, the number of cleaning cycles per unit time depends on the period and the amplitude of inlet dust concentration, and increases rapidly beyond a specified cyclic period of inlet dust concentration. On the other hand, in a pressure switch type the number of cleaning cycles is almost independent of its inlet variables and constant. Therefore, a pressure switch type is preferable to have an advantage over a timer type for long cyclic period of inlet dust concentration.

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