across various sections of the column and can lead to overdesign, increased capital expenditure, and sometimes compromised performance. The hybrid tray configuration is an engineered solution grounded in mass transfer fundamentals and economic rationality. It balances hydraulic stability, tray efficiency, and capital expenditure by matching tray design to specific demands. With the hydrocarbon industry expanding into new horizons, the adoption of trays and internals from var - ious generations has evolved as a techno-economic tool to meet the performance benchmarks with optimal plots and selective future margins. Further reading 1 Kister, H.Z., Distillation Design , 1992, McGraw-Hill. 2 Van Winkle, M., Distillation , 1967, McGraw-Hill. 3 Liebermann, N.P. and Liebermann E.T., A Working Guide To Process Equipment , 3rd edition, McGraw-Hill. Rasna Rajendran is an Assistant General Manager at Engineers India Limited (EIL), with more than 19 years of experience in process design and engineering of units and systems within the hydrocarbon upstream and processing industry. She specialises in hydraulic design and engineering of column internals across refinery, petrochemical, and fertiliser applications in green and brown fields. Rajendran holds a Bachelor of Technology degree in chemical engineering. Email: r.rasna@eil.co.in Anupriya Shahi is a Manager at Engineers India Limited, with more than 10 years of experience in the chemical process industry. Her areas of expertise include hydraulic design of mass transfer internals, deaerators, and process design of flue gas desulphurisation units. She has extensive experience in revamp and retrofitting projects, as well as efficiency improvement studies for column internals. She holds a Bachelor’s degree in chemical engineering. Navneet Agarwal is General Manager and Head of the Mass Transfer Department at Engineers India Limited with more than 27 years of experience in fired heater design, hydraulic design of mass transfer internals, process design of units, revamps, and troubleshooting for the hydrocarbon industry. He holds a Bachelor of Technology degree in chemical engineering. He has authored technical articles in reputed journals. Figure 6 Column erection (misalignment with bolts can be seen)
and beams. This causes the internals not to fit properly, leaving gaps in the design, compromising phase distribu - tion, and ultimately performance. Crane capacities: In cases where only conventional valves are used, column diameter increases to ensure adequate hydraulic performance. This increased diameter is substan - tially larger than that obtained using combinations of HC and conventional trays. Handling these larger diameter col - umns requires larger and heavier cranes, adding significant stress to the structure (see Figure 5 ). Lifting large, curved segments without inducing temporary flexing or perma - nent deformation is also a major concern. Erection and alignment issues: Erecting larger diameter columns poses an additional issue since it requires welding a minimum of two parts. Misalignment at joints can cause ovality or tapering, especially if field welding tolerances are not tightly controlled. Additionally, ensuring the vertical alignment of large-diameter column is also difficult (see Figure 6). Economic Implications: A hybrid tray design often yields substantial cost savings by avoiding the ‘blanket’ applica - tion of costly HC trays. It also allows for savings related to column dimensions, which can be costly when conven - tional valve trays are applied uniformly. Operational savings result from improved energy efficiency and a reduced risk of hydraulic instability, especially at turndown loads, which can cause unplanned shutdowns or require expensive troubleshooting. Conclusion Process-driven tray selection, supported by rigorous hydraulic modelling and column profiling, is the necessity of our times. The hybrid tray configuration approach has techno-economic benefits and can be extended to address implementation challenges. It is important to have an unbiased assessment, espe - cially with the increasing trend toward complete HC tray-based designs, which often cite debottlenecking and performance enhancement as justifications. However, such proposals often overlook the required hydraulic demands Figure 5 Installation and on-site welding of column segments
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