From Steam Turbines to Large Motor Drives for Ethylene Plants: Considerations for Making the Switch

Increasingly, as major refinery operators move towards decarbonization, electric motor drives are considered as viable and in many ways more efficient replacements for steam turbines driving the primary plant ethylene compressors. This technical review discusses how to assess the project retrofit - in terms of the new electric motor controls, how to start and stop large powered motors, sizing of adjustable speed drives (ASD), and how to anticipate torsional issues that may arise (which likely were not issues for the steam turbine driver). Other project questions pertain to compressor modifications – which may enable a more reliable motor driven train design or make the compressor more efficient thru speed changes, rewheels¹, or rotor change-outs. The authors have relied upon previous publications and recent conference feedback [13] in writing about previous experiences as a supplier with large power (> 20MW) motor drive replacement projects worldwide.