PHOTO: Chris Richards, Lallemand
FERMENTATION
Lurking Problems A blanked line on a fermentation outlet is an example of a dead leg where contaminants can hide.
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Renewable Fuels | Ethanol Group 42 | Ethanol Producer Magazine | JANUARY 2013
source may be elusive. “You can have a contamination from a fill line or heat exchanger that only shows in the fermentor because the mash only remains in the heat exchanger for a few seconds or minutes,� Richards explains. Multiple samples need to be gathered from as many places as possible and analyzed, using one of several methods, such as titrations, high-performance liquid chromatography (HPLC) or fluorescence microscopes. The samples need to be re-analyzed after several hours to determine if bacteria are growing. An increase in the organic acids, or other indicators being tested, indicates a possible source of contamination. Sometimes the sources of chronic contaminations are structural. Many plants were engineered for mechanics and cost effectiveness and not necessarily optimized for hygiene, Richards points out. Furthermore, when changes to a plant are proposed, the economic and process impacts are well studied, while the hygienic implications can sometimes be overlooked. He recommends that a plant’s quality control team systematically select areas of the plant to review in detail, looking at each line connection and valve. “Look at the product running through the branch or line and assess the risk to the process by looking at the type of product, frequency of cleaning and normal temperatures,� he says. Look for and eliminate dead legs—lines that are no longer in use, or perhaps used only occasionally—and make sure that there is no potential for bacterial contamination to move into the process. An ongoing project for every plant should be to optimize the pipework, he adds. Key things to look for include verifying internal weld surfaces are polished, making sure valves aren’t positioned too far from the T and finding any pipe runs with low points that are not drained. Each tank and all heat exchangers need scrutiny as well, using the same sort of logic as applied to pipework, Richards advises. While plants can’t change design easily, a good set of standard operating procedures can be designed to optimize hygiene. “Find key performance indicators that can be used to monitor effectiveness,� he says. Clean in place (CIP) procedures need to be reviewed to make sure the fluids are at the proper temperatures, the correct cleaners are used, the