Lard-tank.
A vat in which fats are cooked to obtain them free from watery matters and membrane.
Wilson's tank is a vertical cylinder with a charging hole at top; a steam-jacket and steam-coil for heating; try-cocks at different hights for examination of contents; discharge-cocks at different hights for drawing off the liquid oil and the water; discharge-hole, with cover at the bottom, to remove the solid matter from the bones and fibrine.
In
Everett's apparatus (
Fig. 2812) the digester, containing the fat, is surrounded by an outer shell constituting a hot-water and steam space, to which it is connected by stay-rods, which unite the waterspace at bottom with the steam-space at top, and pass through the vertical flues
A B. The vapors from the digester, charged with odors and organic matter, pass through a pipe at top of the apparatus into a super-heating coil over a furnace, into which they are finally discharged and consumed.
A spiral flue surrounds the outer case of the boiler.
Broadnax's apparatus consists of an exterior casing of masonry in which the digester, which may be of the form shown either in the upper or lower figure, is placed.
In the first it is stationary, and consists of an inner and outer shell, between which
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and through flues in the inner one
A A the heat circulates.
The rendered fat, in a fluid condition, descends from shelf to shelf, and is strained through the perforated bottom
C, whence it is drawn off. The furnace has an inclined flue at each side, through which the products of combustion pass to and around the digester.
Gases from the digester are delivered into the furnace.
This may be effected, as shown in the first figure, by an air-pump
J and condenser
K, by which the gases withdrawn from the digester are compelled to pass through a cylinder, heated by a grate
P, in which the watery particles are condensed by a series of plates
i j and drawn off by a pipe; the dry vapor, ascending, passes through another pipe to assist in heating the furnace.
In the lower figure, the perforated digester
G is mounted on trunnions and rotated by a crank; the oil exuding is strained through the diaphragm
E, and the gases pass through the pipe
I to the furnace.
H is the charging manhole.
