for handling corrosive and particulate-laden process streams. As refineries continue to process increasingly sour crude – driven by changes in feedstock availability resulting from geopolitical developments – efforts to upgrade bottom-of- the-barrel products, and the expansion of crude processing capacity, the sulphur load to the amine regeneration unit and subsequently to the SRU has increased substantially. To manage this added capacity, the SRU needs higher inlet pressures, which in turn demand lower pressure drops across the amine regenerator. These requirements highlight the growing limitations of conventional tray-based designs, which often become bottlenecks and restrict overall plant throughput. Constructing additional trains or entirely new units to overcome these constraints involves significant capital investment and extended timelines. Consequently, operators are increasingly pursuing smarter and more economical alternatives, with internal system upgrades becoming a key area of focus. One such upgrade involves replacing trays with random packing. These modern internals offer a compelling suite of benefits: increased capacity, lower pressure drop, and enhanced mass transfer, all without altering the column shell. Thanks to recent innovations in filtration, corrosion control, and experience in operation and packing design, this approach is not only possible but increasingly attractive. This article presents a case study on the retrofit of an existing amine regenerator column, which was originally equipped with tray internals. The column was evaluated for modification to incorporate random packing. The primary aim of the study was to increase the amine processing capacity while reducing the pressure drop across the column. The scope of this analysis is limited to the regenerator itself; any modifications to associated equipment are excluded. Trays vs packing: a comparative overview Trayed columns are engineered with a series of horizontal plates spaced vertically inside the tower. Each tray facilitates vapour-liquid contact in discrete stages. In amine service, fixed valve trays are commonly used due to their mechanical robustness and antifouling nature. These trays are designed to manage the rigours of corrosive
environments and are often favoured for their reliability in high-fouling applications. Key advantages of trayed columns include: ○ Robust mechanical design : Trays are structurally robust and can withstand process upsets, pressure fluctuations, and thermal cycling. ○ Ease of inspection and maintenance: Trays allow straightforward access during turnarounds, making cleaning and inspection relatively simple and less labour-intensive. ○ Better handling of fouling : The open design of trays accommodates some solids and fouling, which can be manually cleaned without unloading internals. ○ Well-characterised hydraulics : Tray performance is well-documented, enabling reliable scale-up and design across a wide range of operating conditions. Challenges with trayed columns: ○ Higher pressure drop : Primary drawbacks of trays are the relatively high pressure drop across each tray and the need for a larger column diameter (for a given throughput) compared to packed beds. Packed columns use fill media, either random or structured packing, to provide a continuous surface area for vapour-liquid contact. Modern packing designs offer high mass transfer efficiency with significantly lower pressure drop. These columns are increasingly being considered for revamp scenarios where space, pressure head, and cost constraints are critical. Benefits of packed columns include: ○ Lower pressure drop : Packed beds generally offer a much lower pressure drop per theoretical stage compared to trays, enhancing the pressure available to downstream units like the SRU. ○ Smaller column diameter : High surface-area packings can manage large vapour/liquid rates in a smaller diameter than equivalent trays, which can reduce column size. ○ Compact and lighter internals : Packings generally weigh less than tray stacks and do not require support rings for each tray. This can simplify tower internals and, in some cases, reduce the structural load. The absence of downcomers means the entire column cross-section is available for flow, and packed beds can be stacked in multiple layers with intermediate redistribution if needed, using the height efficiently. Challenges with packed columns are: ○ Sensitive to liquid/vapour maldistribution: Uniform liquid and vapour distribution is critical.
Refining India
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