For Grain Processing Corp. (GPC), one of the country's largest corn wet-milling firms, the problem was removing particulates added to the water by the processes themselves. The company mills corn and then steeps it in 125°F (52°C) water, causing the starch to transfer into the water. Cloth filters separate out most of the corn solids. The starch is then converted first into sugar and then into ethanol.
To cut its energy use, the process water passes through heat exchangers after the steeping process. Since the solids in the water run as high as 20 percent, they built up inside the heat exchangers. The heat exchangers then had to be pulled offline every two to four months for cleaning, a several-day task for the maintenance crew. GPC tried cartridge filters, but these also required frequent cleaning. Switching to self-cleaning filters on the heat recovery exchangers allowed the plant to keep running without constant attention from the maintenance staff.
“The filters definitely saved us a lot of manpower in cleaning the heat exchangers and replacing gaskets,” says maintenance supervisor Derrick Biggs. “The gaskets are extremely expensive, and every time you take the heat exchangers apart, you most likely have to replace the gaskets.”
Based on his experience with the heat exchangers, Biggs then turned to the cloth wash system, which uses rotary vacuum drum filters. Particulates were clogging the nozzles on the cloth wash, requiring operators to go in and unplug them. Installing self-cleaning filters keeps the spray nozzles open, allowing them to do a better washing job and allowing the plant to get more capacity out of each cloth.
“The Tekleen filters have performed beautifully, and we will continue to find new uses for them,” says Biggs.