Throughout this book, we have repeatedly offered guidelines for sizing and operating small-scale distilling apparatus. These guidelines (3.75 - 5 cm column diameter, 750-1000 Watts operating power once at temperature) are admittedly conservative, but are known to be safe, reliable and to produce an excellent quality product with minimal attention and intervention. These guidelines are an excellent starting point if you're interested in producing high-quality ethanol for botanical extracts, beverages or perfumes.
Many people are interested in distilling ethanol for fuel use, an activity that is even legal in the United States (but under strict licensing requirements). Fuel alcohol must be high purity to burn correctly, but must also be made in large quantities. Most fuel alcohol stills operate continuously, and have columns 150 mm (six inches) in diameter.
We recognize that in any activity or hobby, some people are primarily interested in the process: how to perfect it, how to expand it, how to best run it and how to speed it up. This interest and spirit of enquiry leads to new discoveries including better methods and equipment for us all. For those of you interested in scaling up or speeding up the process, we offer two words of caution, and then some helpful information.
Before you build a bigger mousetrap, consider carefully what you really need and want! This sounds simple and straightforward, but more than a few home brewers have built equipment that turned out to be much bigger than any batch they really wanted to make. Size your equipment to produce the actual amount of products you will use. Yes, you can build a 100 liter (25 gallon) boiler with a 150mm (six inch) column, and produce 20 liters (5 gallons) of 95% ethanol in eight hours, but what are you going to do with it? Fuel a car? Go for it (with your fuel producer's license securely in your pocket)! Store it for years until it is used up? Probably not a great idea.
As you scale up any process, interesting things happen. Within certain boundaries, you can increase all the parameters proportionately, and things will work well. At a certain size, though, things will suddenly quit working properly, and a complete redesign is needed. You have entered a new operational domain, where the ground rules are different. Once you have a design that works well in that domain, it can be scaled up easily until you find the upper edge of the domain.
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