Abstract: Process and apparatus for separating particulate material from fluids. Essentially, the process and apparatus involves passing a dispersion of particulate material in a fluid through a porous, solid tubular member, which can retain the particulate material within the tubular member but permits passage of the fluid therethrough. The process and apparatus disclosed are especially useful in washing and/or adjusting the concentration of particulate materials dispersed in fluids by recycling the dispersion through the porous member until the concentration of dispersed particulate material is increased to a predetermined degree.