Study of oily sludge treatment by centrifugation

Centrifugation has been widely applied as a pretreatment method for oily sludge. The effect of centrifugation on pure oily sludge was stable and unsatisfactory under different speeds, times, or temperatures. A new parameter, the mean volume diameter of solid surface layer particle (SPD) was proposed to evaluate centrifugal effect. The results showed that water content of about 90% together with a TPH (Total Petroleum Hydrocarbons) content around 4% and SPD of 31-32 mu m was the limit for treatment of oily sludge in the low speed range. Higher speeds may be more effective in increasing the number or quality of critical particles. The analysis of water distribution by differential scanning calorimeter showed the dewatering rate of free water was much higher than bound water, and the bound energy of oily sludge centrifuged at 4000 rpm was about 2392 kJ/kg, which was much higher than that of municipal sludge. The solid particle migration was calculated using the grade efficiency model and the deviation between the simulated and experimental results suggested this model should be further studied to improve simulation accuracy and practical application.