Systems and methods for separating alkane gases with applications to raw natural gas processing and flare gas capture

Abstract

The present invention is a field-deployable system for separating methane and natural gas liquids (NGLs) from a raw gas stream comprising a compressor; a dehydrator; a refrigerator having one or more stages; and a separation subsystem adapted to separate the raw gas stream into three product streams including a methane stream that is at least 80% methane, an ethane-rich stream, and a NGLs stream having a vapor pressure of no more than 250 psia at 38° C. The methane stream is sufficiently lean to be useable in existing natural gas engines without modification. The NGLs stream has a sufficiently low vapor pressure to be transportable in standard propane containers. The ethane-rich stream may be utilized within the system itself to power its own operations. The system can be utilized to reduce flaring from liquids-rich gas production sites to an absolute minimum, produce natural gas liquids for transport, and provide dry methane gas suitable for use in portable field generators.

Description

REFERENCE TO RELATED APPLICATIONS[0001]This application is a non-provisional of and claims priority from U.S. Ser. No. 61 / 836,220, filed on Jun. 18, 2013, entitled “Mobile Alkane Gas Separator,” the entirety of which is hereby incorporated by reference herein.FIELD OF THE INVENTION[0002]The present invention relates to enabling the utilization of raw natural gas, such as flare gas, for power generation and liquids capture. More specifically, this invention relates to a mobile system for separating raw natural gas into a high-quality methane gas stream, an ethane-rich gas stream, and a natural gas liquids stream having a low vapor pressure.BACKGROUND OF THE INVENTION[0003]The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.[0004]Currently liquids-rich raw natural gas is being flared in large quantities at numerous locations by oil producers. This activity entails significant loss of income that could ...

AI Technical Summary

Benefits of technology

[0014]The inventors have realized as a result of substantial experimental work that an optimal temperature and pressure range for the entire process can be achieved with a unique refrigeration design and unique overall system design. The result is a system that can achieve high-quality separation in a field environment using a mobile processing plant. By utilizing a unique cascade / autocascade refrigeration system to achieve an optimal temperature range, the inventors have been able to reduce the operating pressure of the entire system, as well as reduce the cost and complexity of the entire system. The result is a portable natural gas processing plant that can simultaneously achieve both lean methane separation as well as NGLs capture meeting Y-grade specification.

Problems solved by technology

Some existing solutions were designed for extracting NGLs from flare gas, and then flared the remaining methane and ethane because it was unusable in existing gensets.

Other existing solutions generated high-quality (lean) methane for CNG or pipelines, and flared the remaining NGLs because it had high ethane content, and hence a high vapor pressure, too high to be transportable in existing propane tanks.

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