Over the past several years, as many of you already know, there's been a tremendous amount of public interest in homeproduced fuel alcohol, especially among people in the agricultural community. Unfortunately, a small—scale operation—such as that which might be set up by a handy individual with a limited budgetoften isn't as time—and energy—efficient as are commercial plants . . . simply because a backyard facility likely doesn't have the twin advantages of large capacity and state-of-the-art engineering.

As a result, the owner of an "appropriate"—sized fuel factory—though enjoying the satisfactions of lower initial plant cost and energy independence—might still have to "pay the piper" in terms of operating convenience and production expense. So, in an attempt to combine the desirable features of a homestead backyard still and an industrial behemoth, MOTHER's researcher Clarence Goosen has spent the better part of a year designing and building a distillation system that operates under vacuum . . . to deliver a contin uous flow of 185 proof ethanol at the lowest possible operating expense.

CONVENTIONAL CONSTRUCTION

In essence, the cost-conscious designerdeveloped an efficient atmosphere still, which he then modified to incorporate a vacuum system. Thus the unit's "negative pressure" capability is an option that can bechosen or discarded by the builder.

Clarence's still uses [1] a reboilerheated by MOTHER's multifuel hot-oil furnace (see issue 65, page 126)—to serve as the "steaming vat" from which vapors rise, [2] a stripper column, filled with polypropylene pall rings, to remove the alcohol from the mash, [3] a rectifier column, also pall-ring packed, which further fractionates (that is, upgrades to a higher proof)the rising vapors, [4] a refluxing section (this assembly includes an internal heat exchanger and a high-proof-alcohol feed line) to keep the upper part of the rectifierat a constant temperature below that found in the lower section of the tube, and to provide a source of high-grade con densed ethanol that serves to enrich and thus strengthen—the ascending vapors, and [5] a two-stage condenser column, which uses incoming mash and cold water, respectively, to remove the final product first from the driven vapor and then from the discharge air (that which is drawn through the vacuum pump). You'll notice, too, that the relatively compact design utilizes an interconnecting pipepositioned between the stripper and the rectifier column—in order to halve the total height of the tower . . . which would otherwise be over 30 feet tall!

HOW IT WORKS

In operation, MOTHER's newest distillery has proved to be quite effective, thanks to a combination of the vacuum system and several other desirable energy- and timesaving features. Briefly, here's how it works: Heat is constantly being added to the reboiler via an internal tubing network filled with hot oil. Because this chamberalong with all the other "sealed" components in the still-is under a vacuum of approximately 22 inches of mercury, the mash within the container will boil at only 125°F (this, of course, is due to the fact that the liquid requires less heat to come to a "roll" under a negative pressure condition).