Quench water pretreat process

Abstract

A process for pretreating a oily/water stream for closed loop dilution steam production within an ethylene plant using countercurrent multi-stage extraction to remove both free and dissolved organic solutes from in-situ (net) quench water with an organic solvent to yield an aqueous raffinate containing only residual amounts of organic solute. The raffinate is steam stripped to remove the residual organic solutes, yielding a pretreated quench water stream substantially free of organic material. The pretreated quench water is suitable for reuse to generate dilution steam (without fouling). The (solvent) extract from extraction is regenerated in a solvent regenerator having an overhead stream for purging light ends, a bottom stream for purging heavy ends, and a heart-cut side stream for recycling solvent to the extractor. Alternatively, solvent may be taken as a heart-cut or equivalent from an existing ethylene and/or refinery plant process stream, once passed through the multi-stage solvent extraction unit, and then returned to the processing unit of the plant from which it was taken.

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