US Patent 7575624 Molecular sieve and membrane system to purify natural gas

The invention comprises a process of removing carbon dioxide from a natural gas feed stream comprising sending a natural gas feed stream comprising methane and carbon dioxide through an adsorbent bed to produce a carbon dioxide depleted methane rich product stream after removal of carbon dioxide. The adsorbent bed is regenerated and then the spent regeneration gas stream cooled to produce a cooled spent regeneration gas stream that is sent to a membrane element. A permeate stream passes through the membrane element and a residue stream passes by the membrane element without passing through said membrane element. Substantially all of the carbon dioxide and a minor portion of the methane comprises the permeate stream which is disposed of and a major portion of the methane and a minor portion of the carbon dioxide comprises the residue stream which is then recirculated to the regeneration gas stream.