Expression deliquoring of oily sludge from a petroleum refinery plant

This work evaluates filtration followed by expression characteristics of oil-containing sludge from a dissolved-air-flotation unit of a petroleum refinery plant at a mechanical pressure of 2000 psi. Although slightly but finitely enhancing the deliquoring rate, cationic polyelectrolyte conditioning cannot significantly reduce the residual liquor content after expression. In contrast, freeze/ thaw treatment can significantly improve the sludge's deliquorability and markedly reduce the bound liquor content. Closely examining the freezing time and the required cost revealed that freeze/thaw technique is a feasible means of treating oily sludge from a petroleum refinery plant.