AIChE Journal, Vol.47, No.7, 1561-1570, 2001
Validation of a new filtration technique for dewaterability characterization
Characterization of the compressibility and permeability of flocculated suspensions is a time-consuming experimental process that often takes days to perform. A new pressure filtration method developed characterizes a sample only in hours. Using stepped pressure sure filtration, the compressive yield stress P-y(phi) and a hindered settling function R(phi) of flocculated suspensions are determined as a function of the solids volume function phi. Traditional pressure filtration experiments involve the pressure filtration of a particulate suspension in which the time of filtration t is monitored as a function of piston height from which the specific volume of filtrate V is determined. P-y(phi) is determined from the equilibrium solids volume fraction. The gradient d(t/V)/dV is traditionally used to determine R(phi) using a suspension filtration theory developed by Landman and White. The new method uses only one stepped pressure compressibility filtration test and one stepped pressure permeability filtration test to determine P-y(phi) and R(phi) for multiple solids volume fractions and substantially decreases the time requiredfor sample characterization. To eliminate the influence of a stepped pressure on calculated permeabilities, the analysis of experimental results was modified using the gradient dt/dV(2). Results are presented for. a zirconia suspension comparing both single and stepped pressure filtration.