Revamp of a Propane Recovery Plant To 90% Ethane Recovery from Design to Start-up

Presented at Annual Conference, 13 - 15 September 2017 at Sofitel Chain Bridge Hotel, Budapest by
John Mak, Brian Jung, Curt Graham and Alejandro Ramirez, Fluor
Fluor built a 600 MMscfd propane recovery cryogenic plant which has been operating for over 18 years. The plant has been achieving 99% propane recovery in full ethane rejection mode producing salable grade LPG. In recent years, the demand of ethane for petrochemicals feedstock has increased which could only be met with an increase in import. To reduce the amount of imported ethane client decided to convert the cryogenic plant from propane recovery to operate in ethane recovery.
The conversion must be achieved with minimal capital investment and must consider the changes in gas composition considering the variations in nitrogen content. The original propane recovery plant was designed for very low nitrogen content which must be revamped to operate between 5 mol% to 18 mol% nitrogen content. The recovery targets of the revamped process were 90% ethane recovery and 98% propane recovery.
The revamp scope included the installation of a new cold box to handle the higher cooling duty and re-traying column internals to handle the higher liquid loading. No changes were necessary for the turbo-expander refrigeration system and residue gas compressor.
The ethane recovery plant was started up and met all performance targets in August 2016. This paper is to discuss the original propane recovery design and discuss the details of the ethane conversion process. Lessons learned from the design and startup process will also be discussed.