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Ejectors eject energy hogs

Published by , Senior Editor
Hydrocarbon Engineering,

Saving energy and thus reducing a plant’s carbon footprint is vitally important in today’s world. One of a plant’s greatest energy users can be its steam-driven turbines. Steam turbines have excellent reliability and durability and are used to drive pumps, compressors, generators, and other rotating mechanical equipment throughout the refining, chemical, and petrochemical industries for processes that produce petroleum products, chemicals, fertilizers, electric power, and other products that are used every day by people around the world.

Turbines utilise the potential energy contained in pressurised steam, converting it into kinetic energy to power a rotating shaft. Optimising turbine operation, which can often be accomplished by correcting issues in the auxiliary equipment that supports the turbine, will result in reduced energy use.

This article will focus on condensing turbines that discharge into a steam surface condenser which operates under vacuum. It will describe how the operation of the steam surface condenser and venting ejector package can greatly affect the amount of steam needed to produce the desired power output. Reducing a plant’s energy needs can depend on optimising the operation of these components, yet it is common for plants to neglect the condensers and ejectors, not realising the important role this equipment plays in influencing a plant’s steam use.

In an ideal world, steam turbines are isentropic machines, where the entropy of the steam leaving the turbine is equal to the entropy entering. Many improvements have been made to turbine designs over the years and, due to the efforts of rotating equipment experts, modern steam turbines can be capable of operation at 70 – 80% efficiency. Operating an efficient turbine and using the least steam possible do not always correlate, as will be seen. Neglect of the surface condenser or ejectors can turn an efficient turbine into an energy hog. The energy used by a turbine is dependent on the combined operation of the turbine and its auxiliary equipment…

Written by Bill Kubik, Graham Corp., USA.

This article was originally published in the March 2021 issue of Hydrocarbon Engineering magazine. To read the full article, view the March issue here. And to sign up to receive a free regular copy of the magazine, click here.

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