Hybrid membrane and pressure swing adsorption nitrogen removal system

A membrane system for removing nitrogen from a feed gas containing at least nitrogen and methane, the system comprising:

• a) a first membrane stage, fed with the feed gas, configured to produce a first permeate enriched in methane and a first residue containing nitrogen;
• b) a second membrane stage, fed with the first residue containing nitrogen, configured to produce a second permeate enriched in methane and a second residue enriched in nitrogen;
• c) a pressure swing adsorption (PSA) system containing PSA beds, fed with the second residue enriched in nitrogen, configured to produce an high pressure overhead stream containing nitrogen and a low pressure offgas stream containing methane therein;
• and
• d) a combined gas, formed by combining the second permeate enriched in methane and the low pressure offgas stream containing methane,
• wherein the combine gas is forwarded to the feed gas for recycle, the high pressure overhead stream containing nitrogen is vent out, the first permeate enriched in methane is collected as a product.

A process for removing nitrogen from a feed gas containing at least nitrogen and methane, when the feed gas containing exceeding 10 mol % but not greater than 20 mol % of nitrogen, the process comprising the steps of:

• a) splitting the feed gas into a first and second feed streams;
• b) moderating a ratio of the feed gas in the first and second feed streams, respectively;
• c) forwarding the first merged gas to the second membrane stage, wherein the first feed stream is merged with a first residue enriched in nitrogen from a first membrane stage before forwarding the first merged gas to the second membrane stage;
• d) forwarding the second merged gas to pressure swing adsorption (PSA) beds to produce an high pressure overhead stream containing nitrogen and a low pressure offgas stream containing methane therein, wherein the second feed stream is merged with a second residue enriched in nitrogen from the second membrane stage before the second merged gas to pressure swing adsorption (PSA) beds, and;
• e) combining a second permeate enriched in methane from the second membrane stage and the low pressure offgas stream containing methane from the PSA beds to form a combined gas and forwarding the combined gas to the first membrane stage as a first stage feed gas;
• f) compressing the combined gas before forwarding the combined gas to the first membrane stage;
• g) collecting a first permeate enriched in methane as a product;
• and
• h) venting out the high pressure overhead stream containing nitrogen.