FIG. 155.—DEODORIZING TANK FOR COTTON SEED OILS.
FIG. 155.—DEODORIZING TANK FOR COTTON SEED OILS.
—The oil is heated to the original temperature and steam of high pressure and temperature introduced into the body of the oil. The length of time required for treating the oil depends largely upon its nature, some oils being more neutral and more nearly odorless than others, consequently no exact rule can be laid down that would fit all cases; it must be left to the judgment of the person handling the oil.
—To obtain the temperature above mentioned a pressure of 150 pounds should be carried, and late practice introduces a superheater for reheating the steam to insure high temperature by adding 100° to 150° F. to the steam temperature.
FIG. 156.—SECTION OF BOTTOM OF DEODORIZING TANK.
FIG. 156.—SECTION OF BOTTOM OF DEODORIZING TANK.
—As soon as the oil is deodorized it is drawn off and allowed to cool. It is pumped into the treating kettle, or what is known in refineries as the “dirt” kettle. There it is brought up to a temperature of 160° F., when the fullers earth is added, generally using from one to two percent of earth with this bleach, following an agitation of about ten minutes. It should then be pumped through the filter press into the receiving tank, where it is held until used. After going through this process the oil is known to the trade as “water white.”
FIG. 157.—SECTION THROUGH EXHAUST HOOD OF DEODORIZING TANK.
FIG. 157.—SECTION THROUGH EXHAUST HOOD OF DEODORIZING TANK.
—Refined tallow or oleo stearine melted and clarified by pumping through a filter press without the use of fullers earth is added to the cotton seed oil so prepared, and the mixed substance, containing proportions previously described, are ready for passing over the cooling roll.
—The filter press (Fig. 158) should not be used more than two or three times until it is taken apart, all the sediment and dirt removed and clean cloths substituted. Continued use of filter cloths, without proper cleaning, has a deteriorating effect upon the material pumped through the presses, and different kinds of products should not be passed through the same press.
—Color is an important feature of compound, when an odorless oil has been produced. The mixture passed to the rolls is usually at a temperature of 120° F. and this heated body of material amounting to 4000 pounds per hour on an eight foot roll requires a very large capacity of refrigerating equipment.
It is desirable to maintain a brine temperature in the shell of from zero to five degrees above. A fifty-ton refrigerating equipment of commercial rating is inadequate for this duty. Consequently compound manufacturers must have ample refrigerating machine capacity.
The lard roll is preferably of the size noted and should operate at not to exceed seven revolutions per minute, provided brine of the above temperature is supplied; fewer revolutions if temperature is higher, which naturally reduces the capacity.
The lard roll, pump, and strainer equipment is the same as described for lard, except that the lard is packed directly from the picker trough without the use of an additional agitator.
—A new process has been devised whereby soft oils, such as cotton seed oil, can be hardened so as to make a purer vegetable product. The substance has quite a large field but it is not intimately connected with the packing business.
—This is a purchasable product and is used at times as a substitute for oleo stearine.
—The production of lard oil used in compoundinglubricating oils and illuminating oils is still carried on to some extent. The process consists of graining the oils in graining tanks or in seeding trucks similar to oleo oil graining trucks.
—The lard cooled to a temperature of 40° F. is placed in cloth wrapper arranged so that all oil is strained through the wrapper. The solid substance contained in the wrapper is lard stearine used to harden pure lard.
FIG. 158.—FILTER PRESS FOR LARD OR OLEO OIL.
FIG. 158.—FILTER PRESS FOR LARD OR OLEO OIL.
—After the fats have been washed they should be drawn into trucks or tierces and placed in a room where there is good ventilation, and kept there for about two days, giving the acid fumes an opportunity to pass off; the fat will then be found to be lowered to about 80° F. and should then be removed to a room that is refrigerated. After remaining in this temperature three or four days the fats will be found to be crystallized, or grained, and of about the temperature of the rooms. It is then ready to go to press.
—The usual pressing temperatures for the several kinds of commodities pressed are as follows:
These and the temperature of the room, however, are subject to variations.
—A lower quality of lard oil is made from hog greases. These are made from condemned hogs, catch basin skimmings and similar sources. The methods are similar to those used for No. 1 lard oil, except that the former is treated as an edible product and the latter as inedible.
The extracted stearine is sold or used for soap purposes.
—It is not customary to speak of any particular cold test of cotton or grease oils; however, in case of pure lard oil, pressed, it would have a cold test of about 42° F. Pure neatsfoot would have a cold test of about 45° F. In case colder degree oils are desired, either pure lard or neatsfoot, it would be necessary to make the lard colder than above; as to neatsfoot oil, if it is desired to make a 30° F. test, it would be best to make two pressings. First chill stock to a temperature of 42° F., pressing it in a room at 45° F. and then take the oil that is made in this way, refrigerating it in a room at 32° F. and pressing it at a temperature of 32° F.
—Before pressing the low grade greases it is necessary to wash with sulphuric acid to eliminate the impurities, such as water, lime soaps, albuminous matters and ordinary dirt. Shallow wooden vats are ordinarily used for this purpose, the vats being of greater width than depth, as the acid water settles best in a shallow receptacle. Where a comparatively small amount of work is to be done an ordinary wooden vat made out of good sound pine, with three-inch staves and well bolted together, is all that is necessary, but where the work is continuous these wooden vats should be lined with ten-ounce lead, as the acid very soon destroys the vats.
—The method of washing with the sulphuric acid is as follows: Into the wooden or lead-lined vat run clear water to the amount of about 10 to 15 per cent of the weight of the grease to be treated, and when the water is in, add one per cent of sulphuric acid to the fat to be washed, the acid to be 66-degree density. It is important that the water be put in first, for if the acid is put into the tank first and the water afterwards run in, an explosion is liable tooccur on account of the intense heat generated by the absorption of the water by the acid. In case of an explosion the acid is liable to be thrown on the attendants. After the water and acid have been mixed, add grease, turn on steam and boil until the fat and acid show clear; at first it will be muddy or cloudy. Usually a boiling of twenty to thirty minutes is sufficient. This work should be done on the top floor of the building, or some place where there is ample room for the escape of the vapor, as the fumes of the acid are very strong and are injurious to the building. After the boiling is finished, allow the tank to settle ten to twelve hours, draw off the acid water from the bottom, and if the same is clear and clean it shows that the fat had little foreign substance and the solution can be used over again. If it shows a great deal of foreign matter in the solution it should be run away.
All pipes leading from such treating vats should be of lead. It is also necessary that the pipes in the vats be of perforated lead coils, as iron pipes would very soon be destroyed.
—At times, for bleaching purposes, and especially on low grade greases, it is usual to refine and bleach the oil. The amount of fullers earth to be used in filtering depends upon the condition of the oil to be filtered. With prime steam lard no fullers earth should be used; it is simply filtered through clean press cloths. In the case of lard oils and tallow oils, the color of the oil desired must also determine the amount of fullers earth to be used, no set rule as to the amount to be used in every case being practicable.
Every manufacturer of these different grades of oils has his own grades and standards established, to which the lard refiners usually work, and the amount of bleaching, etc., which is necessary for each individual lot should be governed by the knowledge of the operator, rather than by any set rules.
In the pressing of these articles the oils generally run from 40 to 52 per cent of stock, the balance being stearine, the percentage of oil obtained varying according to the temperature at which it is pressed, and according to the relative market prices for oils and stearines.