Recovery of Light Olefins and NGLs from Refinery Off-Gas

Abstract

Recovery of Light Olefins and NGL's from Refinery Off-Gas

Kathy Bigger*, Danielle Goldbeck

Linde Process Plants, Inc., Tulsa, USA

*corresponding author: kathy.bigger@lppusa.com

Refinery Off-Gas can contain products such as light olefins and NGL's.  The Off-Gas streams from various refinery units are normally collected in a common system and burned as refinery fuel gas.  Linde Process Plants, Inc. (LPP) has a proven technology for the recovery of valuable light olefins and NGL's from Refinery Off-Gas.  Moderately pure hydrogen can also be recovered. High recoveries of ethylene and ethane (95+%) and very high recoveries of propylene, propane, and C4+ can also be achieved. 

There are many technical challenges in designing a Refinery Off-Gas recovery process.  In addition to the challenge of minimizing capital cost and achieving high energy efficiency, it is also essential to be able to clearly define the variations in Refinery Off-Gas composition and volumes that can occur due to changing conditions in the various Refinery units.  It is imperative to design the Refinery Off-Gas recovery process to be robust enough to handle these variations.  Accurately determining what contaminant species are present in the Refinery Off-Gas and what type of contaminant removal processes are required is also a critical component of the process design.  Properly addressing each potential contaminant is important both due to downstream product specifications as well as protecting the cryogenic processing equipment in the Refinery Off-Gas Recovery unit.  Finally, each location will have a unique set of requirements for downstream processing of the recovered olefins and NGL's, which will depend upon the type of Refinery units that are within the complex as well as potential customers across the fence.

In this paper, LPP will provide an overview of how cryogenic processing can be used to recover light olefins, hydrogen, and NGL's from Refinery Off-Gas and will also detail some challenges and solutions in designing a Refinery Off-Gas Recovery unit.