A is a vessel, preferably of cylindrical form, and containing an upper perforated diaphragm, a, and lower perforated diaphragm, b, the former having a central opening, through which the material to be treated may be introduced between the two diaphragms, and this opening having a detachable perforated cover, d.
On the top of the vessel there is an opening, e, furnished with a detachable cover, f, and at the bottom of the vessel there is an outlet-pipe, h, furnished with a suitable cock or valve, i.
Liquid hydrocarbon, preferable such as is of a volatile character—benzine, benzole, or gasoline, for instance—is introduced into the vessel above the diaphragm a through a pipe, H, and perforated ring, I, or otherwise, the hydrocarbon passing through the diaphragm and falls in a shower on the substance contained in the vessel.
The hydrocarbon will trickle through the mass, taking up whatever oily, resinous, or fatty matter it comes in contact with until it falls through the lower diaphragm into the space D, whence it may be drawn off from time to time through the outlet-pipe, h.
In extracting oily, fatty, or resinous matter from vegetable or animal substances by hydrocarbons, it has been the practice either to subject them to hydrocarbon vapors, or to immerse or steep the substances in hydrocarbon until the latter takes up the oily, fatty, or resinous matter.
The vapor plan is preferable in treating wet animal substances, such as offal; but for dry vegetable or animal matter—seeds, for instance, or the residuum resulting from the rendering of tallow—we prefer the plan before described.
The flooding or steeping of animal or vegetable matter in liquid hydrocarbon results in a mixture or emulsion of gelatinous, albuminous, and fatty or oily matter, combined with animal or vegetable tissues, the whole forming an amalgamated mass; hence, whatever fatty or oily matter is extracted is accompanied by more or less of the suspended gelatine or albumen, either of which is more difficult to remove from the oil or fat, and has a tendency to discolor the same.
This difficulty, it has been found, can be obviated by preventing the hydrocarbon from remaining in a quiescent state in contact with the material; in other words, by causing it to trickle through the mass, which, by this plan, retains its granular condition, and gives out its oil or fat to the hydrocarbon without the albuminous or gelatinous matter.
In the apparatus before described, for instance, an occurrence of the objectionable flooding of the material, tending to bring about the results previously mentioned, is obviated by never permitting the extract in the lower portion of the vessel A to reach the lower diaphragm b. By drawing off the extract from time to time, any impediment to the free discharge of the hydrocarbon with such oily and resinous matter as it has taken up, through the lower diaphragm, is prevented, and a continuous dripping of the hydrocarbon through the mass secured.