an atmospheric or vacuum flash condenser. After cooling, the mixture is held for one to two hours at 85°C to give the alpha-am-ylase enzyme time to break down the starch into short chain dextrins. Following pH and temperature adjustment, a second enzyme, glucoamylase, is added as the mixture is pumped into one of four fermentation tanks with a capacity of 2.8 million litres each. “The Johnstown facility produces about 154,000 tonnes of dried distillers grain with solubles every year.” Once inside the fermentation tanks, glu-coamylase enzyme breaks down the dex-trins in the mash to form simple sugars. Yeast is added (30 kilograms for each tank) to convert the sugar to ethanol and carbon dioxide. Urea ammonia is also added for nitrogen, which is food for the yeast. The mash is then allowed to ferment for 50 to 60 hours, resulting in a mixture, known as “beer” that contains about 15% ethanol as well as the solids from the grain and added yeast. The Johnstown facility has a clean-in-place (CIP) system to kill off bacteria and the fermentation tanks are cleaned between fills. The Johnstown plant has its own qual-ity lab where three technicians test samples of the mash. Process operators do the ma-jority of the analysis to monitor the onoing perfromance of the process. The fermented mash is pumped into a multi-column distillation system where additional heat is added. The columns uti-lize the differences in the boiling points of ethanol and water to boil off and sepa-rate the ethanol. By the time the ethanol is ready to leave the distillation columns, it contains about 95% ethanol by volume (190 proof). The residue from this process, known as stillage, contains non-ferment-able solids and water and is pumped out from the bottom of the columns into one of the four Flottweg centrifuges. The 190-proof ethanol is then pumped into the molecular sieve system. These specialized vessels contain molecular sieve beads made of ceramic that absorb water molecules from the process stream while ethanol molecules pass through unaffect-ed. When the ethanol leaves the molecular sieves, it is greater than 99% ethanol by volume or 200 proof. The 200-proof ethanol is pumped to on-site storage tanks where it is denatured or made unfit for human consumption – a legal requirement – and stored until it is ready to be pumped into fuel trucks and hauled away. The stillage from the distillation sys-tem is pumped into centrifuges to sepa-rate the majority of the solid matter from the solution. This creates two products: a semi-solid product called wet cake, which is removed and conveyed to a pair of ro-tary dryers, where it is converted into low-moisture DDGS, and a mostly water process stream, called thin stillage, which is pumped to the evaporation system to be concentrated before being added to the dryers. • KAHL Wood Pelleting Plants Quality worldwide. AMANDUS KAHL GmbH & Co. KG, SARJ Equipment Corp., Mr. Rick B. MacArthur, 29 Golfview Blvd., Bradford, Ontario L3Z 2A6 Phone: 001-905-778-0073, Fax: 001-905-778-9613, [email protected] www.akahl.de 14 Canadian BIOMASS January/February 2013
Canadian Biomass January/February 2013: Page 14
