Combination treatment of active water washing and solvent extraction for oily sludge

Key words:  oily sludge  active water washing  solvent extraction  oil removal rate

Abstract:

An active water washing-solvent extraction treatment was conducted on the oily sludge at the bottom of the refinery tank. The effects of the water-washing active agent, its compounding and processing conditions on the residual oil rate were investigated. The effects of solvent extraction treatment, its compounding and processing conditions on the oil removal rate were investigated as well. SEM and TG were applied to observe and analyze the oily sludge after treatment. It is found that the compound cleaning agent (SDS∶Na₂SiO₃=1∶3) shows the highest oil removal rate, and the optimal process conditions for water washing are:washing temperature 80 ℃, liquid-solid ratio 8∶1, washing time 40 min, and stirring rate 300 r/min. The compound solvent methylcyclohexane-ZO presents the highest oil removal rate when the volume ratio is 1∶2. The optimal process conditions for solvent extraction are:extraction temperature 40 ℃, agent-to-soil ratio 4∶1, extraction time 40 min, and stirring speed 300 r/min. The active water washing-solvent extraction combined treatment can reduce the sludge residual oil rate down to 0.96%.