(146a) Overcoming Foreseen and Unforeseen Problems with Oldershaw Column Designs in a Pilot Plant

Nunley, R., Mid-Atlantic Technology, Research & Innovation Center (MATRIC)
Graham, G., Mid-Atlantic Technology, Research and Innovation Center (MATRIC)
During a pilot plant design, the team recognized a potential problem with standard Oldershaw tray designs handling unusual vapor / liquid ratios, which would be the norm in this particular system. Cold-flow testing with several off-the-shelf Oldershaw column sections demonstrated that the low vapor flow would likely result in poor tray loading and efficiency during operation. Although very little published data is available for the sizing of Oldershaw columns, the team successfully designed custom trays with a unique hole pattern to handle these unusual conditions.

However, upon startup, downcomer flooding problems were encountered in the lower portions of several tray sections. Testing and troubleshooting identified a simple but easily overlooked issue with the bottom tray outlet design that was leading to the inadequate performance.

Once corrected, the trays performed well with good loading. Tests using chemicals with well-understood VLE data validated the tray efficiency, and the results matched predictive correlations for efficiency and pressure drop quite well. This gave the team the confidence necessary to trust that the system could be used to validate the actual process VLE data and scale-up the system for commercial design.

This presentation will qualitatively cover the discussions that led to the identification of the vapor loading concern, the testing that validated it, and the hurdles overcome to produce a sound design basis for the tray design. It will cover the hydraulic problems encountered that led to the downcomer flooding and the corrective actions taken to fix that problem. Lastly, it will cover the testing used to validate the column performance so that the data collected during actual pilot plant operation could be trusted to scale up to a commercial plant design.