(7a) Pressure Recovery Systems for Pressure Driven Membrane Processes

The majority of gas and liquid membrane separation processes are pressure driven. For some separations, such as nitrogen production from air, the desired product is the high pressure retentate stream and the product is desired to be delivered at pressure.

For many other separations, such as filtration or oxygen production from air, the desired product is the low pressure permeate and the high pressure retentate commonly is depressurized without attempt to capture the energy released upon depressurization. Pressure recovery devices for use in membrane desalination plants are increasingly commonplace and can recover in excess of 90% of the energy release.

We describe alternative devices for gas separation processes in which the permeate is the desired product and may require recompression for a second stage to achieve desired purities. The devices relay upon direct contacting between high and low pressure streams in devices that closely resemble the modules used in the separation process. The use of such devices could have a significant impact on energy consumption in pressure driven membrane gas separation processes.