Method for ethane liquefaction

Abstract

The process for ethane liquefaction can include a mixed refrigerant containing heavy hydrocarbons (e.g., butane and/or pentane) using compression without interstage cooling, or cooling only after the first compression stages where there is no liquid formation yet, such that the number of liquid recycle loops are reduced. The lack of cooling in the compressor reduces the compressor's mechanical efficiency; however, this is offset by having a more thermodynamically efficient process cycle because the cycle can operate as a mixed refrigerant rather than cascade.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a non-provisional application of U.S. Provisional Applicant No. 62 / 060,609, filed Oct. 7, 2014, which is herein incorporated by reference in its entirety.TECHNICAL FIELD OF THE INVENTION[0002]The present invention relates to an apparatus and method for liquefaction of ethane. More specifically, embodiments of the present invention are related to liquefying a gaseous stream comprised predominantly of ethane by using a mixed refrigerant loop incorporating heavy hydrocarbons (butane, and / or pentane) compression without providing cooling between stages or with limited cooling between stages.BACKGROUND OF THE INVENTION[0003]Liquefaction of methane (LNG) is well established, dating back to over 50 years. In certain cases, liquid ethane can also be produced directly from these LNG plants along with other higher hydrocarbon chain components and are called natural gas liquids (NGLs). However, many applications require the indep...

AI Technical Summary

Benefits of technology

[0006]The present invention is directed to a process that satisfies at least one of these needs. In one embodiment, the process for ethane liquefaction can include using inline compression without interstage cooling (or cooling only after the first compression stages where there is no liquid formation yet) such that the number of liquid recycle loops are reduced or eliminated. The lack of cooling in the compressor slightly reduces the compressor efficiency; however, this is offset by having a more thermodynamically efficient process because the cycles can operate as a mixed refrigerant rather than cascade.

Problems solved by technology

However, because this process employs large temperature differences between the hot and cold fluids, brazed aluminum heat exchangers cannot be used as the exchangers would be subjected to very high thermal stresses.

As such, the process known heretofore suffers several drawbacks, including using multiple, independent shell and tube type exchangers (or the like), suffering high irreversible losses, and having increased power and capital costs.

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