INDUSTRIAL A S D ENGINEERING CHELMIXTRY
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treated fuels are capable of use in automobile engines of efficiency far higher than the average efficiency now obtainable. Scientific Research
The advances in the petroleum industry during the last half-century have been made in spite of the lack of any sustained broad program of pure scientific research, similar to the movement upon which the coal-tar industry and its dependents, the modern dye, synthetic, pharmaceutical, and explosive industries, were founded. ILIr. Rockefeller
Vol. 18, No. 9
having taken the initiative by establishing a fund of $260,000 for the promotion of pure scientific research in fields related to the petroleum industry, it is hoped that among chemists, a t least, petroleum will be a preferred field for investigation during the next generation. Given a foundation knowledge of the chemistry of petroleum and its COQstituents comparable to the existing knowledge of the identity and chemical behavior of the homologs of benzene, i t is hoped that progress will be made a t an accelerated ratecommensurate with the ever-growing importance of petroleum to civilization.
The Cotton Seed and Its Products' By David Wesson SOUTHERNCOTTONOIL Co., NEW YORK,N. Y.
OMEBODY has called the cotton seed the southern
S
farmers' pocket money, because it is the only part of his crop for which he receives ready cash, after he has met his obligations for fertilizer and the necessities of life, against which he has pledged the staple. I n round figures there is a ton of cotton seed for every two bales of cotton made. The cotton is the big crop. At 20 cents per pound, a 500-pound bale brings the farmer one hundred dollars. With seed a t thirty-two dollars per ton, which has been the ruling price during the past year, the seed has been worth sixteen dollars for every bale of cotton grown. I n other words, during the past season the seed was roughly worth about 16 per cent as much as the cotton. It was not always thus. Many people now living well remember the time when the seed was considered a nuisance, and was thrown into the streams or burned, while the more progressive farmers made it into compost and used it for fertilizer. Some of the states passed laws forbidding the throwing of the seed into streams used for drinking water and fishing. I n other places gin owners were fined for allowing the seed to remain in the neighborhood of towns and villages after it had commenced to decompose. Although cotton oil mills were started in various parts of the South early in the last century, it was not till about 1870 that the seed was worked to any extent. I n that year about 4 per cent of the entire seed crop was milled into oil and cake. At the present time about SO per cent of the seed crop goes to the mills, the balance being saved for planting. During the past season the cotton crop was 16 million bales. This would have made about 8 million tons of seed worth something like 256 million dollars delivered a t the mills. Probably not over 6.5 million tons found their way to the oil mills, where it was worked into oil cake, meal, hulls, and linters. Notwithstanding the vast importance and great value of the cottonseed crop, the commercial dealings in the seed have always been carried on under the supposition that seed is seed, and the price has been regulated by supply and demand rather than by the contents of the seed in oil and ammonia, As a result great losses have been sustained by the mills and unfair receipts by the farmers who, selling on this basis of supply and demand, frequently obtain better prices for poor seed than for that rich in oil. The intelligent mill owner can protect himself to some extent 1
Received July 17, 1926.
by obtaining seed analyses on the seed from various districts and buying only from those districts where the seed shows a good percentage of oil. The composition of the seed is affected by character of the soil, fertilizer used, weather, and the closeness with which it is ginned. The more staple removed in the ginning the smaller the percentage of hulls and the higher the percentage of meats. The Department of Agriculture has been making a careful investigation of the practicability of grading cotton seed in the same manner as corn and wheat. I n a very interesting report before the Interstate Cottonseed Crushers Convention in New Orleans, May 13, 1926, G. s. Illeloy, of the Bureau of Agricultural Economics, bases his grades on the assumption of the proportional ralues of the various seed products as follows: oil 52.5, meal 34.5, hulls 7.1, linters 5.9 per cent. He gives tables showing percentages of meats running from 41 to 60 per cent with oil ,n meats running from 33 to 39 per cent, or from 270.6 pounds to 468 pounds of oil per ton of seed. With these enormous variations it is evident that the mill manager who does not know the content of his seed is buying a pig in a poke. Milling
I n the operation of milling the seed is first cleaned by passing over shaking screens to remove the sand and trash and then over magnets to remove the nails and pieces of iron that are often present. The cleaned seed then goes to the linter, which is a kind of gin for the removal of the short staple left on the seed by the cotton gins. The amount of lint removed depends on the demand and also on how closely the seed was ginned before delivery to the mill. Where a very long staple is desired, only 20 or 30 pounds of lint are cut per ton. Such linters can be worked into yarn and bring a high price. Ordinary practice, however, is to cut 50 to 75 pounds per ton. Such lint is short of staple and contains more or less hull particles. During the war it was common practice to cut from 100 to 150 pounds of lint per ton. This contained considerable impurity which did not interfere with working up the lint with caustic soda and chlorine for munition purposes. When peace was declared, large quantities of this lowgrade lint, left on hand a t the mills, was worked up for paper stock of a choice quality which competed with that made from rags. After the war there was a demand for better quality lint and when the munition linters were exhausted the paper stock manufacture died a natural death.
September, 1926
I X D VSTRIAL A N D EA’GINEERING CHEMISTRY
Linters are used in the manufacture of rayon, smokeless powder, celluloid, photographic films, lacquers, artificial leather, mattresses, upholstery, batting, and absorbent cotton. The production of linters for the past season, t o May 31, was 1,090,367 bales of 500 pounds each. The seed on leaving the linters goes to the hullers, which are cutting mills where the seed is chopped u p fine before passing over the screens which separate the meats from the hulls. In practice some of the hulls are allowed to go into the meats, as in this way the valuable meats are more easily kept out of the hulls. The hulls are either baled or sold loose for corn fodder. They are of value chiefly :is roughage and have about the feeding value of poor hay. The separated meats are conveyed to the crushing rolls which rupture the oil cells, after which they are cooked in steam-jacketed kettles. I n most modern mills these are arranged one above the other, so that cooking is practically a continuous process. The cooked meal is made into cakes in the cake formers and placed between the plates of the hydraulic: presses in camel’s-hail mats known as press cloth. Under slowly increasing pressure of‘ 1500 to 2000 pounds per square inch, the oil flows from the presses, leaving behind a hard dense cake, carrying an alerage of 6 per cent of oil. The cake contains an average of 37 to 42 per cent of protein and is usually bold on a fat and protein basis for export or ground into meal for domestic use. I n this form it is the cheapest known source of protein for cattle food. When made from sound seed and fed with the proper forage it can be used safely and with splendid results. Improvements in Milling Practice
The increasing demand for cottonseed oil has brought about a number of improvements in the practice of milling cotton seed during the past twenty-five years. Greatly improved machinery has been developed for the separation of the meats from the hulls. Under the old system of milling,
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run on the continuous system and are almost automatic in their action, largely eliminating the old rule-of-thumb method in vogue in the older mills. The old system of cooking required a number of separate kettles, each one being run on a batch basis. This resulted in very irregular work, as the seed often varied considerably in composition, especially in moisture content. The “cook” was the most important man in the press room, and on him depended
Heaters of 1900
largely the successful operation of the meal, as it was due to his judgment that the meal was cooked to just the right point to yield the most oil. With the French cookers the irregularities due to the change of the character of the seed are largely eliminated and uniformity of product is the result. The accompanying table gives comparative results of oilmill practice of twenty-five years ago and today for eastern seed. Mill Yields per Ton of Seed 1901 300 675 950 30 45
Oil Cake (or meal) Hulls Linters Loss
1026 337.5 1010 373 155 1211
Refining
Cottonseed Huller of 1900
when seed mas very cheap, frequently a large percentage of meats was allowed to go into the hulls. Now the case is just the reverse; this of course results in a poorer quality of meal, but a great saving in the valuable part of the seed. Comparisons between the d d type of huller and those used a t the present time are shown in the accompanying illustrations. Probably the greatest improvement in oil-mill operation has been the adoption of the French heaters. These are
The crude oil as it runs from the presses is claret colored and, when made from sound seed, sweet and pleasant in flavor. It contains, however. coloring matters and various materials from the seed, which not only destroy its keeping qualities, but interfere with its use as a food. The oil is easily refined with caustic soda. The soda combines \Tit11 free fatty acid, coloring matters, and other organic impurities and, under proper conditions of agitation and temperature, causes a flocculent precipitate which rapidly settles leaving a clear, yellow, supernatant oil. This briefly is the principle underlying refining of crude cottonseed oil, which has been employed ever since the oil has been used for edible purposes. Application of the principle has varied from time to time and in different refineries. The process is carried on in large tanks, holding from 60,000 to 100,000 pounds of oil, and provided with agitating machinery and heating coils. Caustic soda in correct amounts determined by analysis of the oil is run into the tanks and thoroughly mixed, after which, by continuous agitation and the raising of the temperature, “the soapstock” coagulates into flakes, which keep increasing in size. The operation is stopped when the flakes separate and drop rapidly. The styles of tanks and design of agitators vary considerably in different refineries. Twenty-five years ago i t was quite customary to use a blast of air for agitation, but this has
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I N D CSTRIAL A N D EhTGIiVEERING CHEMISTRY
Vol. 18, No. 9 I
been superseded almost entirely by mechanical stirrers. Aside from improvements in the shapes of the kettles and a more intelligent use of caustic soda, there has been little improvement in the refining of the crude oil during the past twenty-five or thirty years. Soapstock under the average conditions carries down with it 20 to 25 per cent of entrained oil. Until about ten years ago this was always lost as, ,soapstock. The best modern refineries are now equipped w i t h centrifugal apparatus, which saves about 60 per cent of the oil thus carried down in the soapstock. This means a saving of 1 to 1.5 per cent of oil on the average good quality of crude oil worked. The yellow oil as received from refining kettles is too dark for use in cooking fats and other products, and has to be removed by filtration. Up to t h e p r e s e n t time fuller's earth has been found to be the most efficient b l e a c h i n g material. Its action seems to be that of an adsorbent. It also seems t o a c t as a I p o 1y m e r i z er. The earth is used as a fine Modern A u t o m a t i c Cooker Dowder added to the oil in kettles provided with agitators. Temperatures range from 90" to 110' C. After agitation with the oil the earth is removed by filter presses, leaving the oil nearly white. The chief improvement in bleaching has been due to the addition of small quantities of activated carbon, which removes the reddish cast from the filtered oil. The white oil has a characteristic flavor of fuller's earth. This is removed by passing steam through the oil a t high temperatures in closed vessels which may or may not be operated under reduced pressure. Deodorizing by steam was started in 1893 and was carried on in tanks under atmospheric pressure. Vacuum kettles were first used in 1900, and have been in use ever since. The details of deodorizing oil vary in different refineries, and are more or less guarded as trade secrets. The fundamental principles are naturally the same, but owing to the variations in application there are considerable differences in the results obtained. Further Treatment for Various Uses
HYDRoGEmTIox-The deodorized oil is used largely for the manufacture of lard substitutes by the addition of either oleostearin or hydrogenated cottonseed oil, which gives the product the proper consistency when rapidly shelled. Hydrogenation, introduced about 1910, revolutionized the manufacture of cooking fats. By this process cottonseed oil acquires the consistency of lard without the tendency to oxidation inherent in the untreated oil. Such products are used to a large extent in the baking industries and for domestic purposes.
PRODUCTION OF WIPU'TER OIL-Cottonseed oil as received from the refinery always carries about 25 per cent of unsaturated glycerides, which cause it to congeal a t low temperatures. By cooling the oil slowly a large proportion of glycerides crystallize out, so that they can be removed by filter-pressing. The resulting oil will remain clear for a long time, a t 0" C., and is known as winter oil. The residue in the filter presses, known as cottonseed stearin, is utilized in the manufacture of cooking fats. Winter oil is used in the manufacture of salad oils, mayonnaise dressings, and certain well-advertised proprietary brands of oil sold on the American market. SOAPSTOCK TREATMENl-The soapstock removed from the crude oil in the process of refining is decomposed by sulfuric acid, which also precipitates certain impurities. The remaining neutral oil in it is hydrolyzed by the Twitchell process, and the dark, impure fatty acids are submitted to distillation under vacuum. The usual results are 20 per cent of pitch, which is used in roofing material, paints, and rubber substitutes. The distilled fatty acids are light in color and form a valuable material for soap-makers and manufacturers of lubricating compounds. Utilization of Protein Meal as Food
To date, chemistry has been applied largely to refining and improving the oil. There is little more to be done except to improve economies in production and improve the color. The latter will not add to its value as a food. The residue after extraction of the oil-namely, the cottonseed cake-has received little attention except for the purpose of determining oil and protein. The protein of the cottonseed has been found to have a high biologic value, which means i t can largely replace meat in the diet. It has been found possible by means of solvents to extract the meats of the cottonseed so as to increase the yield of crude oil
Bauer Bros. Co.
Modern Disk Huller
something like 50 pounds per ton of seed, and leave behind a meal with little taste and the color of light corn meal. This material, carrying about 60 per cent of protein, has been tested as a meat substitute and found to be a palatable nutritious food. It is believed that the future improvements in the cottonseed oil industry will be the utilization of this valuable protein material as a human food. It is a t present far more easy of accomplishment than was the conversion of crude cottonseed oil into edible salad oils and lard substitutes twenty-five years ago, and when i t is accomplished there will be another triumph added to those of the American chemist.
