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Abstract

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 filtration, the compressive yield stress Py (ϕ) and a hindered settling function R(ϕ) of flocculated suspensions are determined as a function of the solids volume fraction ϕ. 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. Py (ϕ) is determined from the equilibrium solids volume fraction. The gradient d(t/V)/dV is traditionally used to determine R(ϕ) 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 Py (ϕ) and R(ϕ) for multiple solids volume fractions and substantially decreases the time required for sample characterization. To eliminate the influence of a stepped pressure on calculated permeabilities, the analysis of experimental results was modified using the gradient dt/dV2. Results are presented for a zirconia suspension comparing both single and stepped pressure filtration.