Sweep gas for membrane-based dehydration modules

A method for drying a wet gas, the method comprising:

• a) passing a feed gas stream through a dehydration membrane module, the module having a feed end and a product end, to produce a dry product gas,
• b) entraining a portion of the dry product gas with a supplemental gas from a source, so as to produce a combined gas, and
• c) conveying said combined gas into the dehydration membrane, the combined gas being conveyed to a point in a vicinity of the product end such that the combined gas functions as a sweep stream which flows countercurrently to the feed gas stream of the dehydration module,
• further comprising selecting a location for said point according to the following steps:
• d) determining a water vapor concentration of said sweep stream,
• e) calculating a water vapor concentration of said feed gas stream flowing within the module, the calculating step being performed for a plurality of locations along the module, and
• f) injecting the sweep stream at a location along the module such that the water vapor concentration of said feed gas stream at said location is greater than or equal to the water vapor concentration of said sweep stream.

A method of providing a sweep gas for a dehydration membrane module, the module having a feed end and a product end, wherein a feed gas stream containing water vapor flows through the module such that some of the water vapor permeates through a membrane in the module, the method comprising:

• a) providing a sweep stream for the dehydration membrane module,
• b) determining a water vapor concentration of said sweep stream,
• c) calculating a water vapor concentration of said feed gas stream flowing within the module, the calculating step being performed for a plurality of locations along the module, and
• d) injecting the sweep stream at a location along the module such that the water vapor concentration of said feed gas at said location is greater than or equal to the water vapor concentration of said sweep stream, the injecting being performed such that the sweep stream flows countercurrently to a flow of said feed gas.