A Practical Handbook on the Distillation of Alcohol from Farm Products

by F. B. Wright

The Steamer. One of the earliest forms of steamer was that of Hallefreund devised in 1871, and adapted for working on a large scale. A modified form of the apparatus known as Bohn’s steamer and masher is illustrated in Fig. [45]. This comprises a steaming cylinder A, having a securely closed opening D for the introduction of the potatoes. Centrally through the cylinder passes a hollow shaft B, which is rotated by the power pulley K. Hollow arms b project radially from the shaft B. These act as mixers of the mash and as coolers. The shaft B at one end is connected to a cold water supply pipe M as by a coupling C, the supply pipe being provided with a cock. E designates a discharge opening for the mash. A pipe F provides for the entrance of steam into the cylinder. G is a pipe through which malt is put in to be mixed with the pulp. L is a steam gauge and J a safety valve. H designates a water pipe. For the relation of the steamer to other apparatus, see Fig. [1].

In operation the potatoes are placed in the cylinder A and submitted to the action of steam at about 46 lbs. to the square inch, and at a temperature of from 266° F. to 275° F.

When disintegrated, the steam is blown off, and the potatoes crushed by rotating the stirring shaft. As the pulp must be reduced from 275° F. to 149° F., the mashing temperature, cold water is forced into the stirrer which chills the blades and quickly cools the mass.

In the vacuum mash cooker shown in Fig. [1], the steaming cylinder is partly filled with hot water at 140° F. to 150° F. The potatoes to be mashed are fed into the cylinder whole. The steamer is then closed and steam admitted while the mash is stirred until a pressure of 65 pounds is reached, when the dissolution of the starch is complete. The steam is then exhausted and the temperature reduced to 212° F. To reduce this temperature to the proper saccharifying point of 145° F., the hot air is exhausted.

Barley malt meal in the proportion of 6 to 10 per cent. is used. This has been previously mixed with cold water in the small grain masher. The malt is admitted to the cylinder and thoroughly mixed with the potato, when the mixture is withdrawn into a drop tub, where it is still further stirred. It is then cooled as described on page [15] and then fermented.

While the crushed potatoes are being cooled and stirred, a mixture of green malt with water is prepared in an adjacent vat, and when the pulp in the cylinder has been reduced to 149° F. the malt mixture is introduced into the cylinder through the pipe G, and thoroughly mixed with the crushed potatoes. The mass is now left to saccharify; the stirrer being operated at intervals throughout this period. This machine might be readily modified so that the steam should enter through the stirrers, by tubes attached to the arms, then the steam may be shut off and cold water sent into the arms themselves to cool the mash.

A variety of steamer used in various forms and modifications in all the larger distilleries, is known as the Henze steamer, Fig. [2]. In this, there are no stirrers. The cylinder is conical, and has steam pipes leading to the interior. At the end of its cone-shaped bottom it terminates in a blow-off tube, having in it a grate formed of sharp-edged bars. In operation, steam is introduced at a pressure of one to two atmospheres until the potatoes are cooked. More steam is then suddenly admitted at high pressure and the softened potatoes forced through the grating at the bottom and into the mashing apparatus in a finely divided state.

In steaming under pressure it is best that the safety valve be so regulated that the steam will constantly blow off as this action keeps the potatoes in motion and facilitates disintegration. Care should also be taken to see that everything about the apparatus is in good condition, as in working under the high pressures used in the last apparatus there is liability of explosion. Rust should be particularly guarded against.

With this apparatus a preparatory mash vat is used into which the contents of the steamers are blown out, malt and water to form milk having been previously let into the mash vat. Blowing out is accomplished in 45 or 50 minutes at 130° F. and about one-sixth of the charge in the steamer is retained in the steamer. The mash in the vat is stirred and cooled and the remainder of the mash blown in raising the temperature to 145° F. when the mash is left to stand from half an hour to an hour. With heavy mashes, rich in sugar, even higher temperatures than 145° F. can be used for saccharifying.