String-wound cartridge filter media are replaceable filter elements fabricated by helically winding yarn around a porous core. Due to their ease of handling, they are widely used in a broad range of applications. These filter media capture particles in liquids and gases within the thickness of the yarn layers. In addition, because the yarn layers possess a density gradient, coarse particles are retained near the outer surface, whereas fine particles are captured in the inner layers, resulting in depth filtration. Although string-wound cartridge filters are characterized by high particle-holding capacity and low pressure drop, excessive particle accumulation can block the voids within the yarn layers, leading to a transition from depth filtration to cake filtration and a concomitant increase in pressure drop.

Blocking filtration theory describes, using mathematical models, the phenomenon in which the pores of a filter medium become progressively blocked by particles during filtration. This theory is generally applied to thin filter media, such as membranes and filter papers, with thicknesses of several millimeters or less. In the present study, however, blocking filtration theory was applied to filtration using string-wound cartridge filter media with thicknesses of several tens of millimeters.

A mixed slurry of calcium carbonate and diatomaceous earth was employed as a model slurry. Constant-rate filtration experiments were conducted using various string-wound cartridge filter media composed of polypropylene yarn. Temporal changes in filtration pressure and filtrate clarity were measured.

The results showed that, for [...].