Course: BFM 201 Ethanol Production

Unit 14 Readings and Lecture

To Do:
Read Textbook: Ethanol Process Fundamentals – Chapter 9 pages 9.1 – 9.11
Drying occurs in the “back end” of the ethanol production process. Preparing co-products, thermal energy transfer, and reusing water occur in the dry house which includes centrifuge, evaporators, dryers and thermal oxidation.  A major component of the facilities energy balance and cost efficiency occurs in the dry house.

Dryer capacity is a limiting factor for controlling the ethanol production process. Dryer failure will shut the plant down and is not easily remedied.  When selecting dryers for the plant, they look for two things: Reliability and maximum economic return. Reliability refers to the construction of the dryers such that they can handle the demands of producing large quantities of dried distiller’s grain. One factor to research in order to maximize economic return is the value of the co-products to be sold.  The facility can make wet distillers grain with solubles and/or modified wet distillers grain with soluble that do not require extensive drying and are a high value co-product. Wet distillers grain with soluble (and MWDGS) do not store for any length of time and should be marketed in the area immediately surrounding the plant. If the preferred market is outside of the immediate area of the plant and will require shipping the co-product long distance or require longer storage time, then the wet cake must be dried. Dried Distillers Grain with Solubles is dried to a moisture content of 10 – 13% in rotary drum driers, flash driers or both.

We have discussed the circulatory nature of ethanol production in the plant. It is important to time each production process from the Front end to the back end to achieve the most economical speed of operation:

- Milling size at the front end affects particle size at the centrifuge and the efficiency of the centrifuge to separate liquids and solids. Good liquid/solid separation is key to efficiency.
- The efficiency of the centrifuge determines the amount of product going to the evaporators. It costs more to remove water at the driers than at the evaporators.
- Dryer efficiency is also a function of fermentation efficiency. Unconverted starch and sugar foul transfer surfaces causing capacity reduction in the evaporators.
- Measuring suspended solids and dissolved solids throughout these production processes provides clues as to how efficient the process is going.

Dryers use a lot of energy and are a source of air emissions. Blowers are used to pull air through the dryer drum. The air will have some DDG particles that need to be removed through a cyclone to remove airborne particles. The air then goes to the thermal oxidizer to remove 99% of any air emission pollutants. We will discuss more on thermal oxidation in the next unit.
References:

Chapter 9 (2006). In Ethanol process fundamentals: An introduction to ethanol processing. Granite Falls, MN: Minnesota Energy Enterprise Center.

Jacques, K. A., Lyons, T. P., & Kelsall, D. R. (2003). Chapter 26. In The alcohol textbook: A reference for the beverage, fuel and industrial alcohol industries. Nottingham: Nottingham University Press.