Method And Apparatus for High Purity Liquefied Natural Gas

Abstract

A novel method and system for liquefying and distilling natural gas into high purity liquid methane (LNG) and NGL product streams. Heat exchangers and distillation towers are configured to produce high purity liquefied natural gas (LNG) and NGL product streams, while also rejecting excess nitrogen contained in the inlet gas stream, utilizing liquid nitrogen as the process refrigerant. A molecular sieve pretreatment system is configured to utilize the vaporized nitrogen stream for regeneration of the molecular sieve beds which are designed for removing water and carbon dioxide from the inlet gas stream

Description

CROSS-REFERENCE[0001]This application is a continuation in part to U.S. patent application Ser. No. 12 / 765,750, filed on Apr. 22, 2010, priority of which is claimed herein and the entirety of which is hereby incorporated by reference.DESCRIPTION OF RELATED ART[0002]The present application relates to liquefaction of natural gas, more particularly, to a more environmentally friendly method and system for providing high purity Liquefied Natural Gas (LNG) with reduced cost by utilizing liquid nitrogen (LIN) as the LNG condensing medium and process refrigerant.[0003]Note that the points discussed below may reflect the hindsight gained from the disclosed inventions, and are not necessarily admitted to be prior art.[0004]The advent of high cost in transportation fuels such as gasoline and diesel (based on high petroleum costs) and the coincident very low cost in natural gas has prompted the transportation industry to switch fuels to compressed and liquefied natural gas. Besides the lower c...

AI Technical Summary

Benefits of technology

[0019]In one embodiment, a system for liquefying and distilling natural gas allows for the recovery of more than 99% of the contained ethane, and also allows for the recovery of other natural gas components as a liquid NGL product that contains less than 0.5 LV % methane in ethane.

[0020]In the present system, the use of vaporized nitrogen refrigerant for the regeneration of the pre-treatment system eliminates the requirement of a Regeneration Gas Cooler or a Regeneration Gas Scrubber typically found in a conventional system.

[0021]Because nitrogen is environmentally safe, the system can operate under an “open loop” design, and the need for refrigerant compression within the plant design can therefore be eliminated. However, the nitrogen can also be recycled back to a Nitrogen Liquefier or other system for reuse.

[0022]The present system will provide almost a 100% recovery of all components of natural gas while minimizing energy input and reducing overall atmospheric emissions.

Problems solved by technology

However, the liquefaction of natural gas into a Liquefied Natural Gas (LNG) product is currently performed using large and capital expenditure intensive equipment.

More importantly, the LNG from a typical liquefier will generally only meet an industrial or commercial grade standard sufficient for gas utility of a power plant use, not sufficient high quality enough for vehicle use.

The cost of trucking LNG fuel from a large distant LNG facility is prohibitive.

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