Following a plant turnaround in mid-2007, the ethylene refrigeration compressor was restarted. During restart, the compressor began to surge. The compressor was shut down due to high amps with an apparent seal failure. The older design of the wet seals allowed approximately 400 gallons of lube oil to leak into the refrigeration system. The seal was replaced and the majority of this oil was removed using a toluene wash followed by several washes with a mix of n-propanol and methanol. The compressor was restarted without issue and ran nine months until a power failure tripped the plant. During the power failure the refrigeration system warmed allowing the stagnant oil to move into undesired locations. Upon startup, the plant experienced poor heat transfer and high pressure drop in the cold box. This resulted in heavy ethylene losses from the demethanizer, and below target production due to pressure drop concerns. When normal operating conditions could not be met the refrigeration system was warmed and cleaned using toluene to disperse the oil and chased with methanol several times. This effort had little effect on improving heat transfer in the cold box. The plant was shut down to inspect the demethanizer and clean the cold box. During this shutdown the first, second, third stage suction drums and demethanizer condenser were cleaned by circulating toluene and chased with methanol. The plant was brought online and heavy losses to fuel were still occurring. To help increase heat exchange an additional exchanger was put online. This exchanger has cracked gas on the tube side and ethylene refrigeration on the shell side. Using this exchanger cooled the demethanizer feeds resulting in better tower performance and lower pressure drop. For weeks following this restart of the compressor, the shell side of the exchanger was blown down several times a shift to remove any oil. This greatly improved heat transfer in the cold box, but did not restore optimal performance. The plant continues to operate with lower heat transfer in the cold box and higher than normal losses to fuel. Several actions were taken to reduce the potential for this failure during startup. Startup procedures were revised to ensure the seal pots are unblocked when putting compressor oil system into service and starting the refrigeration compressor. A shutdown strategy was developed to prevent damage due to prolonged compressor surging. The attempts to remove the oil resulted in increased downtime and loss of production. This paper will further describe the mechanisms of failure and provide more detail on the activities taken to remedy the problem and concepts to reduce the severity.
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