In situ measurement of sludge thickness in high-centrifugal force by optimized particle resistance normalization for wireless electrical resistance detector (WERD)

This study investigates the in situ sludge thickness of polymers in a real-scale horizontal decanter centrifuge using the optimized particle resistance normalization (OPRN) technique. The sludge thickness of poly(methyl methacrylate) (PMMA) in an aqueous sodium chloride (NaCl) carrier fluid was observed as a function of the normalized particle resistance of a wireless electrical resistance detector. The measured resistance of the continuous phase during the centrifugation is set as the reference and normalized following its dominant frequency by Fourier transform. Here, the OPRN limits the particle resistance using the normalization function based on the closed-packing condition (i.e. Krieger 1972 Adv. Colloid Interface Sci. 3 111–36; Phillips et al 1992 Phys. Fluids A 4 30–40; and Rao et al 2002 Int. J. Numer. Methods Fluids. 39 465–83) in the particle sensitivity area (PSA). The normalized value is then plotted in the fitting equation using a nonlinear generalized reduced gradient. The PSA is solved by a simulation study on electrostatics and by static experiments. Two different centrifugation parameters of feed rates and two centrifugal forces at four different measurement points were considered to observe the sludge thickness distribution as a function of operational time. As a result, the in situ sludge thickness is described in the nonlinear fit plot equation with a coefficient score to explain the separation phenomenon inside the decanter centrifuge. The plot agrees well with the experimental data with a high degree of coefficient of determination. (paper)