Abstract
To clarify the flow of wash water in a drained-top counter current washer, the authors conducted a study on characteristics of film flow in the fixed and moving beds during gravitational drainage and an alaysis according to the theory of film flow.
The change of moisture saturation with drainage time in the low moisture zone of the fixed bed was given the following equation:
S=S∞+kf (εux/Kρt) 1/2
where, S∞ is residual equilibrium moisture saturation, ε is porosity, u is viscosity, ρ is density, K is permeability, x is distance from the top of the bed, t is drainage time and kf is coefficient of film flow in the fixed bed. From the experimental results, the average value of kf was found to be 0.43, and S∞ was assumed to be 0.07.
Moisture saturation on the top of the moving bed in the washer under non-washing operation was given the following equation:
S=S∞+km (3εuvi/Kρ) 1/2
where, vi is the moving velocity of the bed, and km is coefficient of film flow in the washer. The experimental data reported in the previous report showed that the value of S∞ was 0.07 when vi=0, and that the average value of km was 0.62. The average value of km in the moving bed was larger than that of kf in the fixed bed. This was considered to have been caused by the fact that the quantity of non-flowing moisture in the moving bed; namely, the residual equilibrium moisutre saturation increased as the moving velocity of the bed increased.
