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Balancing the economies of scale

Published by , Senior Editor
Hydrocarbon Engineering,

Profitable ethylene production involves high-volume, low-cost operation with uninterrupted production runs. Cracked gas compressor (CGC) performance is critical to achieving these goals. As global demand for plastic products increases, ethylene plants continue to grow in size as economies of scale are realised at larger capacities. A 1.5 million tpy ethylene plant is common now, and 2 million tpy equipment is already operating out in the field. Customer requests for 2.5 million tpy and even 3 million tpy equipment are expected.

Beyond plant capacity, there has been a general trend towards decreasing suction pressure at the CGC inlet. Suction pressure improves selectivity, so in some cases compressor volume flow is outpacing plant capacity increases. As volume plays a direct role in compressor frame size, continuing to scale the same compressors ever larger to match capacity means compressor frames will outpace plant capacity.

The scaling problem

The problem is if the industry continues to simply increase plant capacities and CGC inlet volume flows, expecting to increase compressor size to match, economies of scale will disappear. Manufacturers cannot meet ever-increasing plant capacities and volume flows by simply continuing to build larger and larger machines. As compressors get larger, not only do they get more expensive and challenging to build and maintain, but so do their large steam turbine drivers, as power must be increased with plant capacity…

Written by Shane Harvey, Elliott Group, USA.

This article originally featured in the July 2019 issue of Hydrocarbon Engineering. To read the full article, sign in or register for a free trial subscription.

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