separation of yeast
I am a final year chemical engineering student with a design project on the production of fuel grade ethanol.
One of the problems I am looking at at the moment is the separation of the yeast and solids from the ethanol solution prior to distillation.
I have SOME information on centrifuges but would like to know what other methods are used in the industry and if there are any problems with this process
Thanks in anticipation of any help you can give
One option, and I suspect, the only viable option, is not to bother separating the yeast. I believe at least some, if not all the Scottish distilleries, do not bother. The fermented wort including yeast goes into the first stills. That way you get all the alcohol out of the yeast as well as the liquid.
Another option would be to push the whole lot through a membrane filter, normally a vibrating membrane to keep the membrane pores clear. Filtrox is one such company able to provide details of there equipment and process. They may be able to provide you with copies of their sales presentations, which outline the process and efficiencies. I strongly suspect that it would not be economic to push the entire fermented wort volume through such a system, as all it will really do is provide you with a sediment free solution to distill. However, if you separate the yeast from the wort first, and then push the yeast slurry through a VMF, this may prove economic. I do not believe it would be worth the extra kit, as you will end up with less alcohol than pushing all fermented wort straight into the still. You cannot use the VMF to recover the yeast for repitching. If you are really interseted, I can draw up some diagrams etc for you, but as I am away for a couple of weeks from this weekend, it will not be an immediate response.
If you need the yeast for repitching, then you are likely to be using bottom cropping yeast, that is, yeast than when fermentation has finished, settles to the bottom of the fermenter. I supect that if you are fermenting purely for alcohol production, you will not be looking to control fermentation temperature accurately, and will not want to waste energy cooling the stuff down just before you boil the bulk of it up again. If you don't control the fermentation temperature, the yeast is not likely to be fit for repitching anyway, so why bother separating ?
Separated yeast contains plenty of alcohol. We used to mix up yeast cake with water, leave for 24 hours and then pass through a membrane filter and obtain approx 5% alcohol out of it. This would then have to be distilled to concentrate of course.
I can provide loads of info on yeast removal (cropping) and processing if you want it, but I really think you will be wasting a lot of time, energy and capital expenditure in separating the yeast out in the first place.
Hope this helps
Yeast is not typically removed prior to distillation in alcohol production. There is a great book actually called, "Alcohol" on this particular subject. It was written by a guy who is a fuel alcohol producer, and most of the book is about the subject of fuel alcohol production, but there are also great chapters on whisk(e)y, tequila, rum, vodka, and gin.
I highly reccomend this book as a good investment for your project. It really has everything you need to know.
Book Title, Author
Thanks for the information, sounds like the sort of book I definitely need
Just had a look at Amazon and the title "Alcohol" brings up about 3000 books mainly about preventing alcohol abuse
Do you have an author name or publisher or an idea when it was written.
Thanks again for the help
OK, you're in luck. Although I don't know the publisher, I have an excerpt of the book on my website. Go to www.scocia.com and click on the link, "My Research". You can then get a link to the excerpt titled, "ScotchWhisky" that has a lot of information on continuous distillation, including yeast stuff.
Since you are a student there is no problem reprinting a small part of the book.
If you have any other questions about distillation, I worked in the whisky business for a bit, so please feel free to ask. I don't always have time to respond, but I do my best.
Alltech- Bio also offers an excellent textbook called (surprisingly) "The Alcohol Textbook". It's a little pricey at $150.00, but worth the investment if you are pursuing a career in the industry.
You can order it at:
They also have a Newsletter called Alcohol Times, which may have so information for you too. It is free online.
And no, I am not affiliated with them.