(78c) Full Throttle: More Innovations in Ultra-High Capacity Trays

Designing trays for extremely high and low L/V ratios brings special challenges. With cross-flow trays, at the low end of the liquid rate range, where the tray hydraulics transition into the spray regime, tray capacity and efficiency can decline. For this reason, structured packing is often preferred, but if trays are used, they often require special adapted designs, such as orbit flow or perhaps even hybrid tray/packing combinations to be used. At the opposite end of the spectrum, with very high liquid rates, cross-flow trays may be operating in the emulsion regime with very high weir loadings, and tray capacity and efficiency can again suffer as a result.

This also applies for the ultra-high-capacity tray types that are designed to operate above the system limit. These types of trays use either centrifugal or impaction-based separation techniques.

Koch-Glitsch has previously presented in this forum [Presentation 62c, Kister Distillation Symposium, 2023 AIChE Spring Meeting] an adaptation of the ULTRA-FRAC® trays designed specifically for very low liquid rate operation with vapor velocities well above the system limit, such as in glycol (TEG) contactors for the dehydration of natural gas. This paper will describe another field of application of ULTRA-FRAC® trays, this time in high pressure Depropanizers and Deethanizers with extremely high liquid rates (exceeding 50 USgpm/ft² on a tower cross-sectional area basis).

Adaptations to the ULTRA-FRAC® tray design were developed to enhance performance at the highest possible liquid rates. This will be showcased with performance data from a case study in which a light hydrocarbons distillation tower in a commercial NGL Fractionation plant in North America was revamped using ULTRA-FRAC® trays to increase the capacity by 25%. Actual plant performance has exceeded this by a significant margin, demonstrating that we can confidently address the complexities of high liquid rate mass transfer in critical high-pressure applications.