Ejector system troubleshooting
Figure 1. Three stage twin element ejector system
Introduction
Whether for lube oil, fuel oil, or general fractionation, vacuum columns utilize ejector systems to maintain design vacuum levels within the column. Noncondensibles, cracked gases, hydrocarbon vapors and steam are removed from the column by the ejector system. Extraction of these fluids from the column is key to a proper vacuum level within the column and consequently, design charge rates and specification quality product are achieved.
Refiners do have lengthy operating experience with ejector systems. Ejector systems have been the mainstay for refinery vacuum distillation. Whether a crude vacuum tower operates as a ‘wet’, ‘damp’ or ‘dry’ tower, an ejector system is the vacuum producer. Different tower operating pressures and overhead load characteristics of wet, damp or dry operation affect only the configuration of an ejector system but the basic operating principle remains unchanged.
Even with lengthy operating experience, refiners view ejector systems with hesitation and uncertainty. This uncertainty results from an incomplete understanding of the basic operating principles of ejectors themselves and their interdependency with any vacuum condenser it supports or to which it discharges. There is only limited information in technical journals or books addressing operating principles of ejector systems....
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