Retrofitting distillation columns with higher capacity mass transfer internals is an effective way of increasing productivity. In the last decades, tray research and development has focused on two areas – improvement of downcomer designs and development of high performance valves with the target to handle higher vapor loads. An example for the second approach is the development of the new Sulzer UFM™ valve. This paper discusses Sulzer’s experience with laboratory testing strategies for fractionation trays and limitation of hydraulic tests with water and air.
Air/water testing is very popular due to the low cost and its simplicity. It is still considered as a reliable starting point for screening design options and to evaluate feasibility and capacity. The beginnings of the Sulzer UFM valve development followed this path, but soon weaknesses of the air/water test system were found. Prototype designs preceding the Sulzer UFM valve showed very promising results. Consequently, they were further optimized using air/water for maximum hydraulic capacity. But subsequent distillation tests using a standard binary test system at total reflux could not confirm previous findings. A reduction in liquid entrainment, as observed with water, does not necessarily lead to a capacity increase in distillation. The chosen testing strategy was obviously not efficient and disadvantageous regarding cost and timing.
A more successful development path adds more weight to distillation testing, specifically in the early design evaluation phase, but air/water hydraulic tests are not entirely abandoned. Consequently, the later valve designs, currently known as the Sulzer UFM valve, were mainly performed in Sulzer’s 1000mm distillation column and external distillation columns of industrial size.