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

Ethane steam cracking to ethylene plants produce a large amount of organic sewage containing oil and sus-pended 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.