(17b) Process Gas Compressor Fouling & Washing Mitigation

Part A The ethylene industry has been affected by the economic downturn. Plants have operated at low rates and have fed lighter feeds when possible. In this paper, the impacts of feed rates and types on process gas compressor operation and monitoring are discussed.

Part B Ethylene plant capacities have continually increased in recent years with outputs well beyond the 1 MMTPY and now reaching 2 MMTPY. The cracked gas compressor (CGC) is the most critical unit in an ethylene plant and several types of contaminates can often foul the compressor flow path, causing deterioration in performance and significantly losses in plant production. In order to prevent efficiency losses during long-term operation, end users have employed cleaning methods via wash oil injection, mainly on a trial and error basis. Using this methodology, it is difficult to optimize the washing procedure since flow conditions during the wash injection are unknown and the relationship between wash injection procedure and wash efficiency improvement is not clear and has not been studied in detail.

To resolve this problem, the end user and the turbomachinery manufacturer have to work in conjunction with each other to better understand the equipment design, experience and the actual operating conditions. As an OEM, this paper introduces a typical, conventional wash oil procedure and the actual fouling conditions of the compressor flow path to highlight the points to be resolved practically. In order to improve the wash efficiency, the authors carried out the simulation of oil injection by application of a unique CFD modeling and analysis technique and testing of the injection flow pattern on a rotating impeller including flow visualization.

The results of this study will show that introducing the wash oil injection flow directly into the compressor casing is more effective than injection into the suction pipe. However, these results are specific to the manufacturer's equipment design and the flow ratio, spray pattern and injection rate for other equipment designs must be determined independently in order to achieve successful mitigation of the fouling conditions. A part of these impressive results will be shared and discussed.