Two-Step Membrane Gas Separation Process

摘要

A gas separation process for treating a gas stream containing vapors of condensable components. The process includes two membrane separation steps, the second step using membranes of lower selectivity than the first step. Advantageously, the first membrane separation step may be carried out outside the pressure-ratio-limited region and the second membrane separation step may be carried out within the pressure-ratio-limited region. The second residue stream is a desired product of the process, and the process is particularly useful for applications where the target concentration of component A in this product is low, such as below 1-2 vol %.

主权项

1. A process for separating a gas mixture comprising vapors of condensable components A and B, comprising:
(a) passing the gas mixture to a first membrane separation step equipped with first membranes of selectivity α1 for component A over component B; (b) maintaining a first driving force for transmembrane permeation in the first membrane separation step, thereby producing a first residue stream depleted in component A compared with the gas mixture and a first permeate stream enriched in component A compared with the gas mixture; (c) passing the first residue stream to a second membrane separation step equipped with second separation membranes of selectivity α2 for component A over component B, where α1 and α2 satisfy the relationship α1>α2; (d) maintaining a second driving force for transmembrane permeation in the second membrane separation step, thereby producing a second residue stream further depleted in component A compared with the gas mixture and a second permeate stream; and (e) returning at least a portion of the second permeate stream for further separation treatment within the process.