Novel purification of oily process water from ethylene production at pilot scale

Abstract

Ethane steam cracking to ethylene plants produce a large amount of organic sewage containing oil and suspended solids, which can lead to heat exchanger blockage and steam regeneration difficulties. Efficient treatment and recycling of process water is one of the keys to ensure a stable operation of ethylene production plant. The traditional multi-stage tandem process water treatment process has issues such as long treatment process, blockage of flow path by coke powder particles, and incomplete oil–water separation. Therefore, this study proposes a cooperative process combining medium particles extraction (MPE) and combined fibrous coalescence (CFC) technology to remove oil and turbidity in process water. Based on laboratory tests and analyses, a pilot test of process water purification with a flow rate of 1.6 m3/h was implemented. The results of the pilot test demonstrated that the process reduced the average oil content of process water from 606 to 18.4 mg/L and the average turbidity from 1213 to 7.9 NTU, with average separation efficiencies of 96.96 % and 99.35 %, respectively. Compared with current process water treatments, this approach provides a higher operational flexibility, better separation effect, and it is more environmentally friendly. This study provides a novel approach for a green and efficient treatment and recycling of process water.