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Previous Next The best candle and soap tips online! TECHNICAL TREATISE ON SOAP A5D CANDLES. RECOVERY OF REFUSE FATS. 131 SECTION IV. THE RECOVERY OF OFFAL AND OTHER REFUSE FATS AND GREASES. IT is a peculiarity of modern times, that science and industry are constantly endeavoring to utilize otherwise useless Hnd rejected offal and refuse matters for various objects. This is a gain which eliould be all the more prominent, since it advances the national welfare, and also aids in the removal of such matters which, having become putrefied, infect the air with poisons which are often the cause of disease and epidemics. Tn the vicinity of large cities, establishments which attend in a rational manner to working up and utilizing the offal of orgar.ic nature, are a great blessing. Thus Paris has in its environs such manufactories on a grand scale. The largest and most important of them is the one of Sonttriee & Co., at St. Denis. It would be very interesting to state here what ii variety of tilings are manufactured in that establishment. In tie year 1862 they began to utilize the remnants and the offal from the slaughter-houses, from which they drew a yearly yield of 120,000 franca ($24,000). The year following they gave their attention to the scum, dross, ami dregs of the river Seine. In consideration of the vast advantages which this undertaking wculd have on the state of the public health, the Prefeet of the Seine granted to this tirni, for it nominal revenue, the sole yield accruing from the work of clearing the river of cadaverous and floating fats, as well as other stuffs injurious to health. In December, 1864, Pouffrit-e./t Co. umlurtiiok the removal of the putrid waters, the sweepings iind the vegetable remnants from twenty-live public institutions of Tsiris. Tue vegetable refuse was purified by steam, and used for feeuing hogs. In this way the firm mentioned was enabled to fatten 3000 hogs per annum. In December, I8f>7, they constructed two distilling apparatuses for the manipulation of the black residues of the refined rape-seed oil, and obtained thereby an annual production of 500,000 pounds of pure sebacic ucida, which are a suitable ingredient for the manufacture of soaps. They furthermore purchased from the railway companies the old wheel grease, to obtain the fat contained therein, and paid for it annually 100,000 francs ($20,000). Besides the fats and eobacic acids, the chief product of the establishment is sn azotic fertilizer. Of this, thousands of tona are annually manufactured. THE YIELD OP OFFAL FATS BY XBAHS OF SULPHURET OF CARBON. For the recovery of fat from refaee matter the introduction of sulphuret of carbon has wrought a great service, since by its aid it has become possible to extract fat from such substances as contain but small portions of it, and which by further pressing will no longer yield it. Some time ago Deisa bad his aim directed to it,and applied the eulphuret of carbon in the manner indicate!. Thus he extracted fat from the black tar-like residues, which are yielded bj->the distillation of fata in the stearine manufactories, from the aawduat which had served for the filtering of oil, from the lirty remnants, which wore formed by refilling the oiln with sulphuric acid, from wagon grease, and from oily polishing rags. The residuum of the distillation of fat which, by a faulty saponification, often contains upwards of twenty per cent, of fat, must, before the treatment with sulphuret of carbon, be mixed with sawdust iu order to enhance the filtration of the dissolved fat. The sediment from the treatment of oils with sulphuric acid often contains fifty per cent, of sebacic acid. In order to gain this the residuum is treated by washing out the sulphuric acid with hot water, then dried, mixed with sawdust and extracted. The sawdust, which is used for filtering oil, still X$B TECHNICAL TREATISE ON SOAP AND CANDLES. yields with sulphuret of carbon, even after being pressed as much as possible, a further 15 to 18 per cent, of oil. The old wagon grease is first treated with sulphuric acid, then washed and dried and finally extracted. Fatty rags are, without any farther manipulation, at once treated in sulphuret of carbon. This treatment has a threefold advantage: the gaining of the fat, cleansing of the rags, so that they may again be used, and averting great danger of fire, which originates frequently from spontaneous combustion in heaping up these oily rags in the work-rooms. For all the above mentioned purposes benzine might also be used in lieu of sulphuret of carbon, but the latter lias the advantage of possessing a greater power to dissolve fats. Besides this, it should be noticed that offals, which have been lying in dampness, and contain glutinous fat, cannot be worked up with benzine, idiile worked with sulphuret of carbon they furnisli good re3ults. WOOL-FAT AND FULLER/S-FAT. Already in the second decade of this century, Kurrer, von Westrumb, and others, had drawn attention to the fact that immense quantities of fat were lost from the wasliing vats of the cloth manufactories, spinning establishments, dyeing factories, etc., and they recommended that these losses be redeemed. In the washing of the wool must also be estimated the sebacic acid, which the not unimportant quantity of soap furnishes, and is requisite for the process of scouring, as well as the comparatively high amount of the wool yolk or suint. The oldest method for the utilization of the fatty substances of the soap waters, consisted in leading the water running from the washing-tuba into especial cisterns, mixing it there with milk of lime, then letting it settle until it had cleared oft*. After removing the liquid above, the slimy sediment was taken out, strained through coarse canvas for removing the sand, hair, etc., and well dried. The slime having assumed a doughy consistency, it was straightened out into pieces of the size of half a brick, and dried in the air. The dry 18'3 RECOVERY OF REFUSE FATS pieces, called "auinter," from the French word "suint" (wool-sweat) were then dried in retorts, for the fabrication of illuminating gas. This manufacture of sninter, as simple as ma}' appear its manipulations, requires great space and appointments. The drying of the limy fat masses, which can only he accomplished in thin layers, proceeds in damp weather but slowly, and is during the winter season only manageable in artificially warmed and ventilated localities. To this must yet be added, the slow settling of the fatty masses, but loosely combined with lime, and the difficulty, on account of the ever varying amount of fat of the soap-water, to guesa the right proportion of the precipitation. Either too much or too little lime may be applied, and hence suffer in the first case disadvantage for the fabrication of illuminating gas, in the latter case great loss of the sebacic acid. For this reason this method of fabrication has been abolished, and the fat is at present gained from the rinsing waters by decomposing the same with sulphuric tcid. A compact, creamy mass is separated, which is mainly composed of sebacic acids, and, according to its respective origin, is either called wool-fat or fuller's-fat. 3y the first appellation is designated the fat obtained from the offal liquids of the wool-washing establishments, while the soap-waters of the cloth manufactories, dyers' establishments, etc., furnish the fiiller's-fat. From the suint, potash is now obtained in France in paying quantities. For recovering these offal fats, the following process is pursued: The soap-water is put into reservoirs of pins wood. Such a reservoir, which is 2.70 metres (8.85 feet) long, 1.73 metres (5.57 feet) wide, and 1.57 metres (5.15 feet) deep, holds up to the filling level 7000 litres (1349 gallons). Sulphuric acid is added, and, in order to hasten the separation, steam is admitted for a period of from one to tivo hours. The use of sulphuric acid depends, as is self-evident, on the amount of alkali contained in the soap-urater; but a little surplus ia always allowed, since by it a quicker and more complete separation, and in consequence thereof a more solid refined mass is obtained. On an average 50 pounds of BUI- 134 TECHNICAL TREATISE ON SOAP AND CANDLES. phuric acid of 66° B. are sufficient for a complete separation of 7000 litres of soap-water, and furnish 390 to 410 pound a, on an average; hence _400 founds of fat substance, according as this is allowed time to drop oft* into the filtering basins. The filtering vessels consist of baskets, which, are filled with coarse hemp cloth. "When now the caseous doughy mass is amply drained of water, by filtration, and has reached the requisite plastic consistency necessary for forming it into pressed cakea, it is wrapped up in hump cloths, and in the usual way laid between plates in a hydraulic press, and, at first cold, somewhat later with admission of steam, pressed until the complete exhaustion of the liquid contents is reached. In the press cloths remains thereby a solid residuum about one-half of the mass which had been taken, while an equal mass of watery fat runs into the reservoir. The latter quantity reduces itself likewise by the various operations of the refining process to one-half of its weight, whereby a yield of 25 per cent, of salable wool-fat from the pressed mass, i. e., 7.1 grammes (0.25 oz.) per litre (2.1 pints) soap-water may be accepted aa the mean value of fabrication. The crude aqueous fat contained in the press reservoirs yet needs the purifying and draining of water. For the purpose of purifying, the fat is placed in iron tanks of 3£ feet diameter and 5 feet in height, which are inserted into iron housings. According to the greater or lesser purity of the fat the fifth or fourth part of its volume of water and from 2 to 3 per cent, of its weight of sulphuric acid of 66° B. are added, and heated by a direct introduction of steam to a moderate boiling, and kept up for one hour. Thereupon the steam is cut off, the mass allowed to settle for a few hours, and then the lower dull and slimy stratum is drawn oft". The liquid drawn off is replaced by a like quantity of pure water, and with it boiled up moderately in order to remove the sulphuric acid traces. Xow the whole is allowed to deposit, and, after removing the watery stratum, the clear mass of fat is then drawn off. The fat thus gained is still very aqueous. For removing the water the fat is put into kettles in which pipes, either of iron or copper, and of a spiral shape, are RECOVERY OF REFUSE FATS. 135 placed, and through these serpentine pipes the steam vapors circulate and evaporate the water. Frequently the wool-fat is bleached before draining, because it receives a better appearance, and thereby a correspondingly increased commercial value, and is, moreover, freed from its disagreeable smell. The bleaching is performed in wooden vats, which are lined inside with lead, and provided with a stirring apparatus as well as with a heating serpentine. The bleaching liquid is composed of a solution made acid by sulphuric acid and chromate of potash—3 parts of sulphuric acid of 60° B. to one part of chromate of potash—of which, in most cases, a small quantity produces the desired result. In the first place the deoxidized fat is placed in the vat while it is yet warm, and heated white the diluted acid is added under constant stirring (in small portions) on account of the ensuing ebullitions of the chromate of potash, which is to be diluted in three/old its weight of water. The temperature must during the entire operation— which lasts one hour and a half—not exceed 56° C. (132.8° F.). After standing several hours the bleached fat mass settles on the surface. Thereupon the watery salt containing liquid 13 removed, washing the fat afterwards with pure water, and after the removal of the wash-water the stratum of fat is taken off, which, by heating with indirect steam, is then freed from water. If fuller's-fut is heated and permitted slowly to col off in vessels, a separation of a solid and liquid mass takes place. Li order to attain this the fat is heated to 75° C. (167° F.), placed in large vats of '2\ to S'feet diameter, and 6 to 10 feet high, and its temperature slowly decreased to 9 to 12° C.(48.2 to 53.5° F.). To attain the most perfect separation possible, the cooling ofl' muBt be effected very gradually, otherwise the solid sebacic acids are only kept suspended in the liquid mass as a curd, which is difficult to separate from the liquid mass. By a careful operation the sebacic acids separate on the sides and bottom of the vat in crystals. The liquid part may be drawn off by means of a spigot in the bottom of the vat. The solid masses are then pressed out in order com- TECHNICAL TREATISE ON SOAP AND CANDLES. pletely to remove the oily part. Such a process of separation requires in the summer season—in case a cool cellar is not at disposal—from three to four weeks; during intense winter coldness it may become necessary to surround the vessels for crystallization with non-conductors of heat, thus to delay the cooling off. The liquid fat which is drawn off is called wool-fat train. The value of the pressed residuum, as noted above is equal to 50 per cent, of the weight of the mass, and it may be stated that carefully mixed samples of different pressings in the manufacturing business result in the following composition : Water 10.66 Fatty substances 34.74 Other organic matters 22.37 Fine sand 30.33 Soluble silicate 0.08 Sulphuric acid 0.28 Phosphoric acici .0.09 Oxide of iron and clay 0.99 Lime ......... 0.25 Magnesia 0.10 Alkalies ? . . . .0.12 100.00 According to this, this material is very well suited for manufacturing illuminating gaa on account of its great value iu fat and other organic matter, of which the former furnishes per pound 9, the latter 7, cubit; feet of illuminating gas. Since 100 pounds of gas-coal give on an average 500 cubic feet of illuminating gas, ami 8 cubic feet of wool-fat gas have a lighting capacity of at least 10 cubic feet of coal gas, there will be DO error in considering the press cakes as of equal value with good gas coal, especially if all other accessory circumstances are taken into consideration. Inasmuch as in the pressed residuum, which represents 50 per cent of the msisa, 34.74 per cent, fat substances are contained, therefore 17.37 per cent, of the total fat value of the manufacturing material have only a secondary value; hence the method just described is yet a very faulty one and capable of improvement. Volil has therefox'e proposed to mis 137 RECOVERY OF REFUSE FATS, the soap-water with chloride of calcium, and to decompose the lime-soap thus produced by muriatic acid. He operates as follows:— The soap-water is mixed with an aqueous solution of chloride of calcium as long as a caseous precipitate ensues. The lime-soap thus formed is separated by straining by means of large baskets, which are lined with hemp cloth (not too coarse), and then freed by letting drop off and pressing out the greater part of the water contained therein. The mass drained of its water is then placed in well-«overed vats of 12 feet high and 4J feet wide, and decomposed therein with a corresponding quantity of muriatic acid, which is as free as possible from sulphuric acid By a direct introduction of steam the decomposition is accelerated, and the separated sebacic acid kept liquid. The gasea which during the decomposition of the infused steam vapors are developed, pass through a cooling worm of cast iron, which empties into a tightly closed iron box. The latter contains slaked lime, and is, by means of a pipe conduit, connected with the heating apparatus of the steam-boiler. By this apparatus all noxious gases and vapors are completely destroyed. After the decomposition of the lime-soap hits been completely effected, the mixture is left for six liours to rest, and then, by means of a spigot in the bottom of the vat, the solution of chloride of calcium is drawn off, which in turn is again applied for a new precipitation. The fat mass is now again mixed with one-half of the quantity of diluted muriatic acid of the proportion used for decomposition, and for one-half to three-quarters of an hour steam is again passed through. Thereupon the steam is cut oft' and the entire mass is left at rest. Three strata have now formed, one lower aqueous sour liquid, one upper clear stratum of fat, and one middle emulsion-like stratum, consisting of fat and diluted acid. The clear diluted acid is now drawn off, without, however, allowing the emulsive stratum to pass off with it. The emulsion causes great difficulty in the separation of the sebacic acids from the watery liquid. The sebacic acids are then either freed from water, and at 138 Previous Next
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