Tray Columns: Design

Distillation has remained an important separation technology for the chemical process industries. In 1997 it was reported in the journal Chemical Engineering that about 95% of all worldwide separation processes use this technology. In the USA alone, some 40000 distillation columns represent a capital investment of about US $8 billion. They consume the energy equivalent of approximately 1 billion barrels of crude oil per day. Such columns are used in reRneries, petrochemical plants, gas processing plants and organic chemical plants to purify natural gas, improve gasoline, produce petrochemicals and organic products, recover pollulant species, etc. Distillation can be carried out in a tray or a packed column. The major considerations involved in the choice of the column type are operating pressure and design reliability. As pressure increases, tray coulmns become more efRcient for mass transfer and can often tolerate the pressure drop across the trays. The design procedure for the large diameter tray column is also more reliable than that for the packed column. Thus, trays are usually selected for large pressurized column applications. Distillation trays can be classiRed as: