Bal K. Kaul

Simulation of gasoline vapor recovery by pressure swing adsorption

A multicomponent pressure swing adsorption (PSA)-gasoline vapor recovery (GVR) process simulator was used to carry out full-scale simulations of the recovery of butane, benzene and/or heptane vapors from nitrogen using BAX activated carbon. This mixture of vapors simulates the recovery of gasoline vapors from tank filling operations. PSA-GVR processes utilizing both feed and carrier gas pressurization were investigated, with different feed mixtures varying from two to four components, including nitrogen. A long tail in the butane vapor concentration wave was always present when feed pressurization was used, and it led to butane vapor breakthrough, whereas the process having the same conditions but pressurized with carrier gas produced pure light product (nitrogen). Thus, carrier gas pressurization in lieu of feed pressurization should be used in PSA-GVR processes. The presence of the heavier vapor components in the feed resulted in a creeping wave phenomenon, which pushed the butane concentration wave toward the light product end of the column. They also produced higher temperatures in the column, which effectively lowered the adsorbent capacity. These effects have significant implications with regard to environmental regulations and must be accounted for in the design of PSA-GVR processes.