To ensure good ventilation and plenty of space above the vats wherein to work or install suitable vatting machinery, the walls should be at least twelve feet in height. Outlet openings should be formed around the base of the room leading to the outer air and closed by controllable shutters. These are to allow the escape of the carbonic acid gas evolved during fermentation. These should be most carefully constructed, however, to prevent drafts.
The walls and floor of the fermenting rooms should be so made that they may be easily washed down and kept clean. Concrete floors are excellent for this purpose and the walls also may be faced with concrete or cement covered with a coating composed of a mixture of asphalt and coal tar. This mixture may be also applied to plaster walls with good results.
The fermenting vats, as before stated, are made of wood for small plants, and of iron for larger plants, and are usually from three and a half to four and a half feet in height. After the chief fermenting period, it is necessary that the temperature of the mash be prevented from rising beyond 86° F. and to that end movable cooling tubes, coils and stirrers are used. These consist of parallel frames made up of tubes, preferably of copper, through which cold water is passed and which are moved about in the vat, either vertically or rotatively. There must be space above the vats, therefore, for the introduction and removal of these cooling frames, and for the gearing whereby they are driven.
As previously stated, mashes to-day are mostly prepared by steaming and disintegrating in a mash cooker of the type shown in Figs. [1] and [41] or in Henze steamers, from which the mash is blown into the preparatory mash vat, where it is stirred and brought to the proper temperature for fermentation. A convenient arrangement of mash cooker, coolers, pump and vats is shown in Fig. [1]. Where Henze steamers are used they are arranged in batteries, the blow-off pipes being connected to the preparatory mash vats. These are preferably provided with water cooled stirrers consisting of a frame of straight and vertical tubes mounted on a tubular arm projecting from a tubular shaft, and rotated in a horizontal plane within the closed mash vats, by suitable gears. The rotation of the arm stirs and automatically mixes the mash while cooling it. Another form of cooler is shown diagrammatically in Fig. [4].
Whatever form of cooling apparatus is used, attention should be paid to the ease with which the stirrers or tubes can be kept clean, and to the strength of the apparatus, gears, etc. Concentrated or thick mashes require that the stirrers be of massive construction, capable of being rapidly rotated in the liquid.
In preparatory mash vats for use with concentrated mashes, means must also be provided for clearing the mash. These mash cleaners and husk removers usually form part of, or are attached to the vat itself and are driven by gearing from the main shaft carrying power to the mashing room.
A good idea of the general arrangement and correlation of the various apparatus of a plant may be gathered from the sectional view of a grain distillery shown in Fig. [55]. It will be seen from this that the mashing apparatus, steamers and mixers are located on the several floors of one building and in such relation to each other that the several operations of saccharifying are carried on in a continuous movement of mash towards the fermenting vats.
Fig. 55.—Continuous Grain Alcohol Distillery—Barbet’s System.