Expression deliquoring of oily sludge from a petroleum refinery plant

This work evaluates filtration followed by expression characteristics of oi l-containing sludge from a dissolved-air-flotation unit of a petroleum refi nery plant at a mechanical pressure of 2000 psi. Although slightly but fini tely enhancing the deliquoring rate, cationic polyelectrolyte conditioning cannot significantly reduce the residual liquor content after expression. I n contrast, freeze/thaw treatment can significantly improve the sludge's de liquorability and markedly reduce the bound liquor content. Closely examini ng the freezing time and the required cost revealed that freeze/thaw techni que is a feasible means of treating oily sludge from a petroleum refinery p lant. (C) 1999 Elsevier Science Ltd. All rights reserved.