NEUTRAL ALCOHOL PLANTS - PROCESS
STARCH: Grains and tubers are milled before they are used in the process. Starch or by-products from wet milling plants do not require any special treatment and are fed directly to liquefaction.
Starch is treated by liquefaction and saccharification to obtain glucose as a fermentable sugar. The partly saccharified substance is cooled down and fed directly to the fermentation unit. Final conversion of the starch into glucose takes place simultaneously during fermentation.
At the fermentation stage yeast is employed to convert monosaccharides into alcohol.
CDA designs Fermentation units that can be implemented as a continuous process. Continuous systems are generally cheaper and easier to operate. Batch systems are often not preferred as feedstocks not switched.
Fermentation of the substrate starts in a pre-fermenter under adjusted conditions that promote yeast growth. The fermenting mash flows steadily through a series of main fermenters while the alcohol concentration increases to a range of 12 – 14 %vol (depending on the raw material). From the last fermenter the alcohol mash is fed to an intermediate tank for distillation.
With starch milk, yeast recycling can be used to improve yield and accelerate fermentation.