PTQ Q3 2026 Issue

reactor changeover slightly earlier than planned in response to increasing hydrogen slippage can often prevent distur- bances from propagating downstream. In addition to monitoring the hydrogenation unit, oper- ating teams should observe ethylene tower operating trends for early signs of instability. Subtle variations in column pressure, reflux flow rate, or condenser duty may sometimes correlate with hydrogen slip events occurring upstream. Establishing correlations between hydrogen analyser trends and ethylene tower operating parameters can provide valuable diagnostic insight. Finally, integrated monitoring across the cold section can significantly improve troubleshooting effectiveness. Reviewing data from the hydrogenation reactors, column operating conditions, and refrigeration system behaviour together allows engineers to identify relationships that may not be apparent when units are analysed independently. Adopting such proactive monitoring practices helps plant engineers detect upstream disturbances earlier and take corrective action before they develop into more significant operational problems affecting ethylene tower stability. Conclusion Ethylene towers in steam cracking plants operate under highly sensitive cryogenic conditions where even small var- iations in feed composition or condenser performance can influence column stability. Since pressure fluctuations and condenser duty variations are observed directly in the col- umn and refrigeration system, troubleshooting efforts often

focus primarily on these areas. However, practical operat- ing experience shows that disturbances affecting ethylene tower performance may originate upstream in reaction sys- tems rather than within the column itself. Since hydrogen behaves as a non-condensable compo- nent under the operating conditions of the ethylene tower condenser, its presence can influence condensation behav - iour and reduce effective heat transfer performance. This may lead to variations in reflux generation, cyclic pressure fluctuations, and apparent instability in the refrigeration system. Since these symptoms appear within the ethylene tower itself, the upstream origin of the disturbance may not always be immediately recognised. Understanding the interaction between hydrogenation reactor performance and downstream cryogenic distillation is therefore essential for effective troubleshooting. Careful monitoring of hydrogen slip trends, catalyst performance indicators, and reactor operating conditions can provide early warning of developing disturbances. By recognising these upstream influences, plant engineers can identify the true root cause of ethylene tower instability and implement corrective actions before the disturbance escalates into more significant operational problems. Vikram Mohite is a chemical engineer and independent process trou- bleshooting consultant with experience in refinery, petrochemical, and polymer plants, focusing on process diagnostics, operational trouble- shooting, and improving plant performance through practical, data- driven analysis. He holds a bachelor’s degree in chemical engineering and a postgraduate qualification in petrochemical engineering.

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PTQ Q3 2026