A New Model for the Calculation of Height Equivalent to Theoretical Plate in High Pressure Columns Equipped with Structured Packing for iC4/nC4 Separation

Abstract

A semi-empirical model is proposed to investigate the performance of packed columns equipped with structured packing at high pressures. The mass transfer efficiency is determined in terms of height equivalent to theoretcial plate (HETP) for empirical data of an iC4/nC4 mixture at elevated pressures. Some unexpected phenomena cause predictive models of mass transfer to be inaccurate at high pressures. The effects of the gas phase backmixing and the liquid maldistribution on the gas phase mass transfer coefficient and the effective interfacial area have been investigated in this study. The modified model is developed on the basis of the Delft model to predict the mass transfer behavior of structured packing at high pressures. The proposed model is validated by the empirical data and good agreement is observed between the empirical data and the results of the modified model. The error of HETP calculation by the modified model is less than the other models especially at moderate and high pressures. At low pressures, predicted values of different models are almost the same and they show minor errors. The difference between predicted HETP by various models increases by pressure rising. Moreover, the effect of liquid load on mass transfer in packed columns is investigated. The proposed model can predict the effect of liquid load on mass transfer performance. Proper efficiency has been obtained by the modified model for iC4/nC4 separation process in structured packed column at high pressures.

Reactive Distillation Performance of Difunctional Hollow Fiber Composite Membranes with Catalytic and Separative Properties as Structured Packing

“…L 0 L 2.2 0.6 0 0.6 0.33 (10) where Sh is the Sherwood number; D L is the diffusion coefficient in the liquid; φ = (d 0 /d s ) 2 × n is the packing density; Re is the Reynolds number; and Sc is the Schmidt number.…”

“…Structured packing has been widely used for separation processes with many advantages such as high capacity, high mass transfer surface area, high turn down ratio, low pressure drop, and low liquid hold up comparison with trays or random packing . In general, the specific surface of structured packing is between 100 and 750 m 2 /m 3 .…”

“…Structured packing has been widely used for separation processes with many advantages such as high capacity, high mass transfer surface area, high turn down ratio, low pressure drop, and low liquid hold up comparison with trays or random packing . In general, the specific surface of structured packing is between 100 and 750 m 2 /m 3 . Hollow fiber membrane has a large number of specific area due to its small diameter (approximately 1 mm) and has been widely used in membrane processes such as ultrafiltration, , nanofiltration, , pervaporation, − and gas separation. − Cussler and his co-workers have explored the feasibility of hollow fiber membrane as distillation structured packing in membrane contactor, exhibiting an extensive application prospect. − They have found that hollow fiber membrane as a new type of distillation structured packing can decrease the height of transfer unit (HTU) and enhance separation efficiency; moreover, it can be operated well above the normal flooding limit and has the potential for saving energy, since the energy use is huge, approximately 3–5% of total energy use in the U.S., and is one of the major costs in oil products. , …”

“…Structured packing has been widely used for separation processes 1 with many advantages such as high capacity, high mass transfer surface area, high turn down ratio, low pressure drop, and low liquid hold up comparison with trays or random packing. 2 In general, the specific surface of structured packing is between 100 and 750 m 2 /m 3 . 2 Hollow fiber membrane has a large number of specific area due to its small diameter (approximately 1 mm) and has been widely used in membrane processes such as ultrafiltration, 3,4 nanofiltration, 5,6 pervaporation, 7−9 and gas separation.…”

“…2 In general, the specific surface of structured packing is between 100 and 750 m 2 /m 3 . 2 Hollow fiber membrane has a large number of specific area due to its small diameter (approximately 1 mm) and has been widely used in membrane processes such as ultrafiltration, 3,4 nanofiltration, 5,6 pervaporation, 7−9 and gas separation. 10−12 Cussler and his co-workers have explored the feasibility of hollow fiber membrane as distillation structured packing in membrane contactor, exhibiting an extensive application prospect.…”