Debottlenecking Runtime of a Large Beer-Ethanol Column through a Fouling-Hydraulic Analysis and a Robust Equipment Design

The seventh largest bioethanol facility in the United States with a design capacity of 153 MGPY ethanol experienced major runtime problems. This state-of-the-art facility with the latest energy efficiency technology was commissioned in 2012. Years later, the plant pursued process improvements in the fermentation and distillation train. The ethanol yield was improved using new enzymes (bio-catalyst) under batch operation rather than continuous. This improvement resulted in the production of higher percentage of solids being fed to the distillation train. Thereafter, high-performance trays for the beer column were considered to increase runtime and to reduce energy consumption. Unfortunately, this upgrade impacted negatively the bioethanol production, the plant uptime decreased by eighty percent. This bottleneck lasted about 18-months, all this time the plant dealt periodically with the beer column cleaning-in-place (CIP) activities, and failed equipment modifications.

The plant seeking longer runtime contacted the original beer column equipment supplier. The supplier was updated with the operating issues and with the expectations for the replacement. Subsequently, a thorough fouling-hydraulic analysis of original and troubled high-performance trays was performed. Several scenarios were considered to explain the bottleneck impacting this 17-ft (5.2 m) diameter column. The complete analysis and column modifications were presented. These were accepted and swiftly and safely implemented. Conventional trays replaced existing high-performance trays. The new internals had features that assure uniform hydraulics to maximize mass transfer performance, and the most critical one, process uptime.

Since the debottlenecking activities in early 2Q2017, the bioethanol plant is operating at 168 MGPY and longer runtimes, and with expansion plans to produce 185 MGPY of ethanol.

This paper confirms that importance of a robust design of mass transfer equipment for critical applications, fouling in specific; and that in some applications, a well-designed conventional tray can “out-perform” a poorly-designed high-performance one.