Title: Unit 11 Readings and Lecture
Course: BFM 201 Ethanol Production > Section: BFM 201 Ethanol Production

Unit 11 Readings and Lecture

To Do:
Read Textbook: Ethanol Process Fundamentals – Chapter 7 pages 7.1 – 7.9
The microporous molecular structure of a zeolite, ZSM-5 (Wikipedia, CC BY-SA 3.0)

There are several options available for anhydrous ethanol recovery. The molecular sieve is the most common system in place at modern ethanol plants.

Azeotropic distillation was used in the past but it is seldom used today in modern ethanol facilities due to solvent carcinogenicity and toxicity from using the chemicals benzene, cyclohexane or monoethylene glycol to break the ethanol/water azeotrope.

The molecular sieve beds are filled with synthetic zeolite (molecular sieves). The synthetic zeolite used have a small enough pore size (0.3nm) which permit water molecules (0.28nm) to be adsorbed, but not ethanol molecules (0.44nm) in the vapor stream under pressure. This process can only continue for a short amount of time because the synthetic zeolite has a finite capacity for water. Therefore, there are two sieve beds that are cycled allowing one bed to be on-line and one bed to be regenerating every 6 – 8 minutes. The two sieve beds can operate on a timed cycle; however the most efficient systems are controlled by a computer to improve reliability and energy efficiency. The process measurements you need to monitor are Temperature, Pressure and Vacuum.
References:

Chapter 6 (2006). In Ethanol process fundamentals: An introduction to ethanol processing. Granite Falls, MN: Minnesota Energy Enterprise Center.

Walker, G. M. (n.d.). Bioethanol: Science and technology of fuel alcohol. Bioethanol: Science and Technology of Fuel Alcohol. Retrieved from http://bookboon.com/en/bioethanol-science-and-technology-of-fuel-alcohol-ebook

Jacques, K. A., Lyons, T. P., & Kelsall, D. R. (2003). Chapter 21. In The alcohol textbook: A reference for the beverage, fuel and industrial alcohol industries. Nottingham: Nottingham University Press.