STUDY OF A 6-BED PRESSURE SWING ADSORPTION PROCESS

A mathematical model of a six-bed, ten-step PSA operation is developed . The process cycle considered resembles an industrial hydrogen recove ry process from the refinery fuel gas. Three hydrocarbon impurities (m ethane, ethane, and propane) are considered in the feed gas. The adsor bent used is activated carbon. The nonisothermal, bulk separation PSA model adopts the linear driving force approximation for particle uptak e and the extended Langmuir isotherm to represent adsorption equilibri um. A transient pressure equation is incorporated to account for the d ynamics in variable pressure steps. The model was verified using exper imental results from a computer-controlled, laboratory-scale PSA unit. Considering the complexity of operation, comparison of various stream flow rates, concentrations, bed pressure and temperature profiles ind icates that the model provides a sufficiently accurate prediction of t he PSA performance. Parametric studies further show that its product p urity declines relatively quickly with increasing cycle time and decre asing high operating pressure due to the breakthrough of a relatively sharp methane front. There is no real advantage in operating the PSA u nit beyond a high operating pressure of about 18.0 bar.