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V I E W I N FVOOD
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ROSINREFINERY;
B4TTERY O F
FULLER’S E.4RTH FILTERS ON RIGHT
Turpentine and Rosin from Wood Wastes by the Steam and Solvent Process R. C. PALMIER, Newport Industries, Inc., Pensacola, Fla. ginning into a highly technical HE steam a n d s o l v e n t .Vlan,y details hace necessarily had to be chemical engineering industry, naval stores industry had omitted f r o m this brief technical picture of a involving probably in t h e i t s b e g i n n i n g nearly steam und solcent process plant. It has also n e i g h b o r h o o d of 15 million twenty-five years ago. At that been impossible to include the many chemical dollars capital investment, and time almost the only source of control methods without which the main process produces about 15 per cent of t u r p e n t i n e and rosin was the the t o t a l naval stores in the long-leaf-pine forests. However, and its rapidly increasing secondary processes Cnited States. the timber was being rapidly cut would be impossible. There has been indicated, The raw material is preferably by the lumber men, and, while however, ihe general operation at present emcollected from forest lands which the need of replacement by reployed by this chemical industry utilizing the have been cut over for a considerforestation was fully recognized pine wood waste as a source of naval stores. able time. Old wood is always by foresighted interests, it was m o r e r e s i n o u s for the simple not then beingpracticed. These The natural tendency is more and more to reason that i t has resisted decay facts turned t h e a t t e n t i o n of go beyond the simple recovery of turpentine and because of its high resin content. chemists and engineers to a porosin, and the steam and sohent industry m a y The limbs are usually ready for tential supply of t u r p e n t i n e eventually become almost wholly chemical plants collecting without any mechaniand rosin the exact quantity of manufacturing specialty products with turpencal preparation. Large trunks which was not known, b u t of trees are reduced to handling which mas obviously very great. tine, rosin, and pine oil as the raw materials. size’by the axe. T h e s t u m p s This source was the fat resinous which constitute 60 to 75 Der cent wood left behind by this same destruction of the pine forests If successful methods of of the total wood waste are either removed by stump pullers, manufacturing these potential products from waste wood in which case further reduction in size is necessary to facilitate could be devised, it meant the possible clearing of large areas handling, or the stumps are removed from the ground by of land for agricultural purposes a t low cost. The steam and means of explosives. If this latter operation is properly solvent process plants in operation a t present have a total done, the material does not require much further reduction. The wood is transported by wagon, motor truck, or railroad, capacity of around 2000 tons of waste pine wood per day. To keep these plants operating a t full capacity would require depending on the proximity to the plants of the land being cleared. Relatively large stocks of wood are generally mainthe clearing of about 200,000 acres of cut-over land per year. Plants are now located in Georgia, Florida, Alabama, tained a t the plants in case of any interruption of the supply Mississippi, and Louisiana. This branch of the naval because of unfavorable weather or other unusual conditions. stores industry, though relatively small in the number of The raw material is bought entirely on a weight basis instead operating plants, has developed from a more or less crude be- of the more common cord unit because of its irregular form.
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All pine wood waste is not acceptable, and there is usually some grading and culling based upon the visible resin content. GENER.4L
PROCESS
The first step in the manufacture is the preparation of the wood for processing. Reduction to comparatively small size is essential for good recovery of products, and this is usually accomplished by a two-stage hogging and shredding operation. This gives a large proportion of chips of the splinter type, the largest pieces being approximately 0.25 inch in diameter and 1.5 inches long. These chips contain long resin ducts, which
TOP FLOOREXTRACTOR BUILDING
is a condition that does not lend itself to the best recovery of rosin. Considerable study has been given to preparing the wood in other ways, such as chipping across the grain, as in pulp wood preparation, or shaving the wood across the grain, and also high-pressure mechanical crushing. The objects are, of course, to insure short resin ducts and secure higher extraction efficiencies. The hog and shredder preparation is still most commonly practiced because of greater economy. The prepared chips are conveyed either from storage bins or directly from the reduction machines into the processing vessels. These are tanks or retorts of various size and shape and are provided with steam coil and some means of introducing live steam. The chips are held up on a false perforated bottom below which the live steam enters. Iron or steel processing vessels have a high depreciation due to acetic acid vapors from the wood, and in recent years in some plants replacements have been made with the acid-resistant stainless alloys. The first step in the processing is the separation of the bulk of the volatile oil present in the wood by means of steam distillation. Steam is introduced in the bottom of the vessel, the steam and oil vapors pass out of the top to condensers, and the condensate runs to automatic gravity separators. The technical control of the process begins with the steaming step. Steam may be either saturated or superheated, and the operation is conducted under low, moderate, or high pressure, depending upon the results desired. Steaming is continued to a point of steam economy by determining the proportion of oil to water in the distillate. Extraction of the rosin from the steamed chips is the next step in the operation. The contact with steam serves t o heat the wood thoroughly and to draw to the surface a portion of the rosin, thus making it available for easy extraction. The extraction is, in most cases, of the countercurrent type. Several extraction units, connected in series, are each in a different stage of the operation; the head one is the latest to
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be put in cycle and receives the most nearly saturated extract, while the last one which has been under extract the longest time receives a final wash of fresh solvent. There is a large variation in detail of this operation a t the different plants, but the general principle is to treat the chips with successive applications of hot solvent until the extraction of rosin is economically complete. The efficiency of the extraction is governed by a number of factors. These include the preparation of the chips, the removal of moisture, the duration of the operation, and the volume of solvent employed. It, does not necessarily follow that it is most profitable to obtain the greatest yield. Each individual plant has to work out its proper operating balance of efficiency against total output. The type of solvent has been the subject of much investigation and numerous patents, but a t the present time most plants are using a petroleum naphtha boiling between 100’ and 1.50’ C. After extraction the free solvent is removed either by pumping or draining, and the chips are again subjected to steam distillation. Most of the solvent is recovered by separating the rosin from the extract and this, together with the solvent recovered in the final steam distillation of the chips, is reused for extraction. I n a well-designed plant having good mechanical supervision, the efficiency of solvent recovery is high. One of the early discoveries in connection with this new source of supply of turpentine and rosin which played an important part in the development of the new industry was the fact that from the resinous wood could be recovered a pine product not produced by the living pine tree. This was steam-distilled pine oil.
TURPENTINE The oils that are recovered in the primary distillation of the chips consist essentially of turpentine and pine oil in varying proportions, depending upon conditions of steaming. This mixture, called “crude turpentine,” is the only source of turpentine. The refinement of turpentine consists of chemical treatment and fractional distillation. The chemical action is one of thorough contact with alkali and may be conducted by agitation with a moderately strong solution of caustic soda or soda ash prior to the distillation, or during the distillation itself. By this treatment any wood acids, such as formic and acetic, are neutralized, and constituents of unpleasant odor are polymerized. The fractional refinement is conducted either by steam or by dry distillation through specially designed fractionating columns, in the latter case under reduced pressure. Turpentine of guaranteed quality and according to strict specifications is made by careful laboratory and plant control of the operation. PIKEOIL After obtaining the turpentine fraction, the distillation of the crude oil is continued to recover the pine oil. Only part of the total pine oil recovered from the wood is obtained in this operation. Where petroleum naphtha is used as rosin solvent, the balance of the pine oil is recovered from the solvent. In the refinement of pine oil by steam distillation, the normal standard oil has a characteristic light straw color. Water-white pine oil is made for special purposes by a redistillation of the oil with steam over alkali or by dry fractional distillation under vacuum. Steam-distilled pine oil contains a few per cent of terpene hydrocarbons boiling above turpentine but is principally tertiary terpene alcohols, such as alpha-terpineol, and also contains the secondary terpene alcohols, fenchol and borneol,
July, 1934
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from the corresponding grade of gum rosin. Its melting point and acid number are somewhat lower, and its ester value is below the average of gum rosin. It also has color INTERMEDIATE OILS characteristics other than the visible color. FF wood rosin The total oil recovered from the fat pine wood is not all contains yellow and brown pigments entirely absent in all turpentine and pine oil. Other terpene hydrocarbons, such grades of gum rosin. These are shown when the rosin is made as limonene, dipentene, terpinene, and terpinolene, are also into soap or paper size and when used as a base for varnishes recovered from pine wood. These terpene hydrocarbons have and enamels. The identity of these pigments is not known, a boiling range between pinene, which is the principal con- although their chemical structure is partly understood. They stituent of the turpentine, and the pine oil, and may be cut out seem to be oxygenated forms of abietic acid or hydroxy abietic in the refining of the crude turpentine or separated during the acid or oxy and hydroxy esters of the abietic acid. While there are many uses for rosin where color, either visfractionation of pine oil. These intermediate oils have become in recent years standard products of the industry as ible or otherwise, is not important, it is obvious that these color properties limit considerably its field of usefulness. It can they are valuable solvents for special purposes. thus be readily understood why the purification and decoloriWOODROSIX zation of the natural wood rosin occupied the serious attention Returning again to the extraction process, the rosin extract of technologists in that field from the very beginning. Howis delivered hot from the extraction vessel. The amount ever, it was not until 5 or 6 years ago that successful wood of rosin in the extract varies considerably with different oper- rosin refining methods were developed. One method of puriating methods and may be as low as 40 or as high as 125 fication now in use has as its basis the fact that, when the rosin pounds of rosin per 100 gallons. This extract is first given a is dissolved in petroleum solvents, a number of organic compreliminary refining in order to remove oxidized resins which pounds immiscible with the rosin solvent have a selective solare soluble in the hot, but insoluble in the cold extract, and vent action on the dark colored constituents. A large number of materials, such as petroleum and regealso t o separate other foreign matter, such as fine wood dust. The operation in effect produces a cold filtered extract and table oils, are commonly decolorized by absorbents, such as carbons and clays, and it has been known for many years that insures a perfectly clean rosin. The rosin is then recovered from the extract by evaporation rosin may be decolorized by fuller’s earth. Although the of the solvent. This is accomplished by dry distillation under petroleum industry has successfully employed the decolorizing reduced pressure in a film type evaporator or by steam dis- action of fuller’s earth for refining lubricating oils for some tillation in a simple pot still or bv a combination of these years, there has been until recently no commercial application methods. I n all cases, however, the finishing or complete of this medium for purifying rosin. It is this process which is removal of solvent and other oils from the residue rosin is con- used in the rosin-refining plant of Xewport Industries, Inc., ducted under carefully controlled conditions in order to insure a t Pensacola. A somewhat detailed description of the process a rosin of desired quality. After the complete removal of the and its development is of interest. In the case of petroleum lubricating oils, the total amount solvent, the liquid rosin is then ready for delivery to shipping of m a t e r i a l that is containers. capable either of absorption by the earth YIELDSOF PRODUCTS or that it is necessary to r e m o v e in order The yields of the s u f f i c i e n t l y to imprimary p r o d u c t s , prove the color, comturpentine, pine oil, prises a r e l a t i v e l y and FF wood rosin s m a l l proportion of are n a t u r a l l y t o a large e x t e n t dependt h e oil. A s m a l l amount of earth will, ent on the resin cont h e r e f o r e , purify a t e n t of t h e w o o d considerable amount treated, which varies s o m e w h a t with the of oil. In the case of locality, and also on wood rosin, however, the efficiency of the the total amount of plant. The average material that must be recovery, however, is removed to raise the in the neighborhood grade from FF to WW of 6 gallons of turpenis about 25 per cent by t i n e , 1.5 gallons of weight of the rosin. i n t e r m e d i a t e oils, Since a normal, dry, ENDOF CONTINUOUS DRIERS H O W I N G TEMLOCK BOARD 4.5 gallons of pine oil, active clay becomes and-3.50 to 400 pounds s a t u r a t e d w i t ~ iimpurities when about 10 per cent by weight of the earth has of FF rosin per ton of air-seasoned wood been absorbed, it can be readily seen that t o purify rosin, PURIFICATIOX OF WOODROSIX such as wood rosin, requires a very high ratio of earth to Kood rosin manufactured in this way is low in the rosin rosin-in fact, several times more earth than rosin. Filtrascale of gradr. Beginning with the 1oTvvest grade, gum rosin is tion or percolation rather than contact offered the only posgraded as D, E, F, G, H, I, K, 11, S, WG, WW, and X. sible method since the amount of earth required in relation Wood rosin grade? FF between E and F on the gum scale. to rosin was so great. The earth is made to do its maximum The natural rosin extracted from wood has a characteristic amount of work by employing cycle operation ( 6 ) . The process of purifying the rosin with earth is quite simple. reddish color by transmitted light. Besides its distinguishing viqihle color it has other properties which mark it as different A liquid FF rosin normally ready for packaging is redissolved together with a small amount of a phenol ether, methyl chavicol.
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to about a 15 to 20 per cent by weight solution in petroleum naphtha free of terpenes ( 5 ) ,cooled, and washed with water to coagulate any suspended insolubles, and then allowed to stand until all water has settled out. The grade or degree of purification desired is controlled entirely by the amount of rosin or volume of rosin solution passed through the earth. An analysis of the absorbed material at progressing stages of filtration shows clearly the nature of the selective absorption. There is shown to be an interchange and displacement of the material absorbed by the earth. When the rosin solution is filtered through fresh, dry earth, the first material delivered from the filter is solvent containing little or no rosin; that is, all resinous material has been taken up. But as the filtration proceeds, the concentration of rosin in the filtrate increases and the absorbed material gradually changes from whole initial rosin to whole impurities. The decolorized rosin is obtained by evaporating the solvent from the filtered solution, and the solvent is recovered for re-use. After the earth becomes saturated with impurities, it undergoes a revivification treatment. The revivification operation is probably the most important part of the process, both from the standpoint of earth efficiency and cost of the process, since earth and revivification solvent are, except for small unavoidable losses of rosin solvent, the only ram materials used. A large number of revivification materials were sfudied, but the most practical was found to be a solution of ethyl alcohol in petroleum naphtha (4,the alcohol being sufficiently anhydrous to prevent separation from the petroleum solvent. The amount of alcohol in the alcohol-naphtha solution is about 35 per cent by volume. This is the concentration obtained when alcohol is completely recovered by fractional distillation from a dilute alcohol-petroleum naphtha solution. When a filter is cut out of the decolorization c y l e as ready for revivification, it is full of rosin solution. This solution is first displaced with warm naphtha, the displacement going into the filter next following in the cycle. The naphtha is then displaced with just sufficient alcohol-naphtha t o fill the filter, the solvent being introduced through a preheater at just below the boiling point. The extraction of absorbed pigment is rapid and complete so that the introduction of the revivification solvent is immediately followed by boiling naphtha to wash out the revivification solvent now containing the color bodies which have been removed from the earth. This extract and wash are collected in the same receiver. The alcohol is then recovered for re-use by fractional distillation of the combined extract and wash. The remaining naphtha is also distilled off and the impurities are thus recovered as a dark resin. Great economy in the use of the alcohol was also effected by making use of the cycle principle in the revivification ( 5 ) ,since the amount of impurities available for extraction in any single filter was not nearly enough to saturate the alcohol-naphtha solvent. The revivification of the earth by this process is so successful that the life of the earth probably exceeds any commercial installation where fuller's earth is employed as a decolorizing agent. Theoretically the earth would last indefinitely. An occasional mechanical accident to screens necessitates replacement. A life of as much as 750 revivifications is about an average in the present plant. As a t present operated, the plant at Pensacola manufactures I grade rosin as the lowest pale grade and also produces all the paler grades, K, M, N, WG, WW, and X. SPECIALPROCESSES The manufacture of a variety of special products for specialized uses has been a natural development in the manufac-
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ture of the primary products, turpentine, pine oil, and rosin. These modified and secondary products are made by various physical or chemical treatments. For example, turpentine is the source of pure pinene by additional fractional distillation. The tertiary alcohols in the pine oil may be subjected to chemical dehydration to produce terpene hydrocarbons. Rosin readily combines with hydroxides of the alkali metals, such as lime, caustic, etc., either by fusion a t moderately high temperatures or even in naphtha solution a t lower temperatures (3). Since the rosin is available both in liquid form and in solution during the recovery process, limed rosins or gloss oils which are solutions of limed rosin, and rosins containing the water-soluble sodium or potassium soaps of the rosin acids are, therefore, readily produced in the course of rosin manufacture. The levo form of abietic acid is preponderant in wood rosin. This is known by the fact that its specific optical rotation is near zero plus or minus. This form of acid is less suitable for many purposes than its dextro isomer. The transformation of levo to the dextro form is accomplished by heating the rosin a t moderately high temperature, and this treatment is a special process frequently conducted in connection with the manufacture of wood rosin (1, 9). UTILIZATION OF EXTRACTED WOOD I n a well-balanced operation, the total steam and power requirements can be readily supplied by the extracted wood and it is used at present a t all plants for this purpose. The possible usefulness of this material for some purpose other than fuel has been the subject of much thought and research. One logical field of investigation has been that of kraft pulp, but, even though the replacement value as fuel makes it a much cheaper raw material than live wood, the results of the studies along this line have so far not been encouraging. Fibrous products of the general mechanical pulp type have been another field of suggested utilization with much more promising results. The first commercial unit of such an operation is in the plant of Newport Industries, Inc., at Pensacola. The chips upon delivery from the extraction retorts are first screened to separate dust and dirt and are then put through a series of fibrating operations and other processes. The resultant pulp finally in wet condition is formed into large sheets and is then delivered to carefully controlled continuous driers. The finished material made in various thicknesses from 0.125 t o 1.75 inches thick is light, strong, and water-resistant. The product is sold under the trade name of Temlok by the Armstrong Cork Company which is jointly interested with Newport Industries, Inc., in this enterprise. Temlok has found a large variety of uses for insulation and building purposes. LITERATURE CITED (1) Logan, W. B. (to Acme Products Co., acquired by Newport Industries, Inc.), U. S. Patent 1,643,276 (Sept. 20, 1927). (2) Logan, W. B. ( t o Newport Industrles, Inc.), Ibid., 1,807,483 (.May 26, 1931). (3) Palmer, R. C. (to Sewport Industries, Inc.), Ibid., 1,787,281 (Dec. 30, 1930). (4) Palmer, R. C. (to Sewport Industries, Inc.), Ibid., 1,794,537 (March 3 , 1931); Palmer, R. C., and Burda, J. L., Ibid.. 1.791.538 (March 3, 1931): Palmer, R. C., Ibid., 1,794,539 (ifarch 3 , '1931). ( 5 ) Palmer, R. C., Burda, J. L., and Oliver, A. F. (to Newport Industries, Inc.), U. s. Patent 1,807,599 (June 2, 1931). (6) Ibid.. 1,903,493 (April 25, 1933). RECEIVEDApril 2 , 1934. Presented as part of the joint Symposium o n Naval Stores before the Divisions of Agricultural and Food Chemistry a n d of Industrial and Engineering Chemistry a t the 57th Ueeting of the American Chemical Society, S t . Petersburg, Fla., March 25 to 30, 1934.
