The technology of alcohol production
The technology includes the following stages:
Feed stock is weighed, treated of a variety of contaminants before it enters grinding. Grinding of raw materials is carried out on roller or hammer mills of leading European manufacturers to ensure uniformity of grinding with a given particle size, which has a direct impact on the efficiency of further processing of ground grain. The higher the extent of grain milling, the quicker it is liquefied at gentle condition. Nowadays ultra-fine grinding of grain is used as it allows to get 80-95% of particles with size of less than 250 micrometers thanks to special installations, equipped with machine-desintegrator and separating device. Then it is diluted in a mixer with water till given solids content.
- Liquefaction (heat treatment) & Saccharification (hydrolysis)
After mixing and heating grain is fed in cooking section along with water and solutions of enzymes. Liquefaction carries out at high temperature and pressure for cells’ structure destruction and starch dissolving. At heating with water protein is swell and denatured, starch is gelatinized. Structure of feed stock is destructed generating homogeneous mash as a result of pressure drop from excessive to atmospheric at output of liquefied mass from cooking section. Continuous liquefaction is the most widespread. It is characterized with stability and high specific capacity of equipment, the process can be optimized and automated. Liquefied mass is fed in saccharificator. Saccharification of liquefied mass is carried out mainly with continuous method at certain conditions: temperature, medium pH, substrate and saccharified material concentration. During saccharification approximately 67% of starch turns into maltose and 33% - into dextrin which are finally saccharified by medium ferments into fermented sugars during fermentation. Saccharification includes liquefied mass cooling, its mixing with saccharifying material, saccharification and mash cooling. Saccharified mass is continuously running off from saccharificator through heat-exchanger in which it is cooled till 20-24C into fermentation section.
The fermentation process is rather complex , it is carried out consecutively with different ferments. Except alcohol and carbon dioxide secondary (glycerol, acetaldehyde) and by-products (fusel oil) are produced during fermentation. It carries out in fermenters by periodic or continuous methods. Continuous method is more popular as it has certain advantages. This method allows increasing throughput of fermentation section up to 20%, automatizing the process and increasing alcohol quantity. Ready mash is intermediate product of alcohol production. In order to get 1 m3 of alcohol it is necessary to have 12 m3 of mash which consists of 3 phases: liquid, gaseous and solid. Liquid phase includes water and ethyl alcohol with accompanying volatile impurities. Solid phase covers husk and pellet as well as all substances which remain after alcohol, water and volatile impurity evaporation (unfermented sugar, dextrin, protein, mineral substances). Gaseous phase includes carbon dioxide – the product of yeast activity which is generated during sugar fermentation. Mash is pumped into the transfer tank and then distillation process occurs.
To achieve the required concentration and purity of the alcohol the mash is purified during distillation stage. It is the process of binary or multicomponent liquid mixture separation for components or fractions which differ in volatility. The separation of similar volatile mixtures is carried out by multiple two-way mass and heat exchanging between counter flow moving steam and liquid streams. The purpose of ethyl alcohol purification – remove volatile mixtures and get alcohol of standard strength. It is also very important to concentrate selected mixtures and free it from ethanol and water. The minimum concentration of alcohol is 96.3%. To obtain high-quality alcohol additional distillation column is applied.
During distillation process the main waste product of alcohol is formed - stillage, which is processed to produce DDGS, feed yeast or biogas.
DDGS (Dried Distillers Grains with Solubles) - can be used as a high-quality animal feed.
Feed yeast is highly valuable protein supplement in the production of animal feed, feed mixes and premixes for feeding all farm animals, birds, fish and fur animals.
The biogas is used as fuel to produce electricity, heat or steam, or as a vehicle fuel.