Natural Gas Cryogenic Demethanizer Troubleshooting:an Internal Look of the Column Operation

The Demathanizer column of a new natural gas plant located in the West Texas area showed symptoms of premature flooding after one year of uninterrupted operation. The performance issues started after the operation mode was switched from rejection to recovery. Under recovery mode the plant was not able to achieve its nameplate capacity (200 MMSCFD), because the
Demethanizer column showed signs of flooding and excessive entrainment (high pressure drop, erratic temperature profile, out of spec products, etc.) while operating with the lower temperature profile and higher liquid rates required for this mode of operation.

A step-by-step analysis was conducted to identify the possible causes of the performance issues. Throughout the analysis different tools and techniques were used to aid with the interpretation of the process data and column behavior: process simulation, hydraulic evaluation, gamma scanning, on-site inspection of the column internals, etc. This presentation will provide an overview of the steps taken to complete the troubleshooting analysis and highlight some recommendations that could assist other engineers to interpret the process data of columns with similar performance.