ILVD USTRIAL AND ENGINEERISG CHE-IfISTRY
September, 1926
gloss which is its most striking characteristic. It is different with acetate silk. I n this the fiber refuses to take any of the ordinary dyestuffs except the basic colors, and the basic colors, though very beautiful, are extremely fugitive. Therefore, the chemist has been called upon to produce a totally new type of dyestuff for the specific purpose of dyeing this
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new fiber. I n this he has succeeded and we have an excellent range of colors for acetate silk which are all new and allow of producing very interesting and beautiful effects. I n an up-to-date dye house nothing is done just as it was fifty years ago; the improvement is almost entirely to the credit of the chemist.
Fifty Years of Wood Distillation’ By L. F. Hawley U. S. FOREST PRODUCTS LABORATORY, MADISON, Wrs.
I K E many other chemical industries, wood distillation has accomplished most of its development in the last fifty years. I n this country the hardwood and resinous wood distillation industries have developed independently and are still distinct in raw materials and in products. They will therefore be considered separately.
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Hardwood Distillation
I n 1876 hardwood distillation was just beginning as a real chemical industry having as its object the recovery of by-products as well as the production of charcoal. It was differentiating itself along lines of two distinct processesone a modification of the immemorial ldln process, the other a very different operation in which the wood is distilled in iron retorts. The modified kiln process has remained with very little further change until today, but retort distillation has been greatly improved. The old-fashioned horizontal cylindrical retorts required much hard labor in charging. They were just long enough to hold two lengths of 4-foot wood, and the proper piling of the wood in the back of a hot retort was no job for a weakling or a n amateur. I n order to increase daily capacity, the charcoal was not allowed to cool in the retorts but was removed while still hot by raking into large iron cans. The cans were then covered, luted with clay, and wheeled aside for cooling. As soon as the retort door was opened the charcoal ignited, so that this method of discharging and cooling the charcoal added to the severity of the labor. I n order to reduce labor costs, the modern oven retort or “Jumbo” was developed. I n this oven the wood is charged on cars and after the distillation is finished the charcoal, on the same cars, is moved into contiguous coolers of the same size as the ovens. The latter have been gradually improved and enlarged until today the standard distilling apparatus is a 10-cord oven. Many other types of retorts have been tried out, especially some designed for the distillation of sawdust or other smallsized pieces of wood, but of all these only one installation survives. This is a comparatively new system, which has yet to show its superiority over the established process. I n refining processes for the crude distillate there has been great improvement since the early days. At first acetate of lime was the only chemical product recovered, largely in the form of “brown acetate” obtained by simply neutralizing the pyroligneous acid with lime and evaporating the solution. The product was very impure, being contaminated by the tarry material dissolved in the pyroligneous acid. Gradually more and more of the purer ligray acetate” was made by distilling the pyroligneous acid to separate it from the dissolved tar before neutralization. Gradually also the methanolthen called wood spirits, wood naphtha, or wood alcoholcame to be recovered from the neutralized liquor. 1
Received June 14, 1926.
Many of the first stills used in distilling the pyroligneous acid and the neutralized liquor were heated by direct fire. It is reported by old-timers that the still men developed a secret method of firing the acid stills so as to keep the “ball of tar off the bottom” until the distillation was nearly finished. Later steam-heated stills were used, with consequent saving of fuel and still bottoms and with less demand on the skill of the operator. For many years no fractionating columns were used in separating the methanol except the “Burcey pan,” a crude dephlegmator not found outside the industry. With the Burcey pan it was possible to concentrate the iialcohol liquor,” distilled from the calcium acetate solution in a n ordinary pot still, to a standard 83 per cent crude alcohol in one operation, or at most with only a little redistillation of the tails. The crude alcohol was commonly shipped to a central refinery for conversion into the commercial article, since the crude plants, operating on a small scale, could not afford the complicated stills and technical skill required for the refining process. Until about fifteen years ago the wood distillation plant used only the simplest types of apparatus-pot stills, Burcey pans, steam-jacketed evaporating pans, and an acetatedrying floor on top of the retorts. Of recent years the chemical engineer has introduced triple-effect evaporators, continuous column stills, and drum and belt driers, so that the leading plants are now thoroughly modern in efficient equipment. Most of the larger plants are equipped also with methanol-refining apparatus, and some of them have become real chemical manufacturing plants by making the refined products (acetic acid, acetone, formaldehyde) from their crudes. There have been remarkable changes in the demands and uses for the products of hardwood distillation. At first, acetate of lime was the main chemical product wanted, but the wood alcohol demand became an important factor in the great growth of the industry during the first thirty years of the modern period. The industry enjoyed a sort of indirect subsidy on account of the excise tax on ethyl alcohol. The tax was so large that ethyl alcohol could not compete with wood alcohol as a solvent or a fuel, and the well-remembered odor of our spirit varnishes and alcohol lamps testifies to the wide use of the latter. I n 1906 the excise tax was removed from ethyl alcohol denatured for industrial purposes, and wood alcohol was thus brought into direct competition with a cheaper solvent and fuel. This was naturally a severe blow to the industry, but higher prices for acetate of lime allowed it to survive until new and increasing chemical uses for wood alcohol came to the rescue. Hardwood distillation long enjoyed a n absence of competition in the manufacture of all its products. Methanol, acetone, and acetic acid (except in the form of vinegar) were produced from no other source. When the late war vastly increased the demand for these products, however,
t.lie indostry could nut expand rapidly enough to ineet the situation, and the opportuiiit,y was ofrered for developing other processes. Several others were put into production, and two of them survived the war period-a synthetic process for making acetic scid and a fermentation process for acetone. More recenbly an imported synt.lietic methanol has given severe compctition to methanol in& from wood. Tlir only products now remaining free from competition are,
Tlie promoter has also been rcspoiisible ior inany unsuccessful attempts to use unsuitable species and forms of wood, althougl~it has been commercial practice for inany years to use loiigleaf pine exclusively. Eveii with tliis very resinous wood, it has been found profitable to distil only selected material, such as “lightwood” and stumpwood. Tho distillation of such w d was represented largely by tar pits or kilns in 1876, with retort distillation just h e gimiing. The only iniportant ad\rantage of the retort rriethod lay in the recovery of the turpentine and other lighter oils and in higher yields of charcoal. The development of the retort was diificult because it manufactured citlier suhst,itutcs for s t a n h i d products with different properties (the turpcntine arid tar) or else new, complex products OS variable and unkiiowii value (the oils intermediate bctweari tar and turpmltine). The turpentine has fiMlly found its glace as an admittedly different product from stamlnrd gum turpentine, and the tar has for some time sold on a parit,y with, or eveii a t a premium over, tlie former standard kiln product. The miscellaneous oils have also foiind proper markets, althougt! they have not yet become xwll staiidardiacd. In nn attempt to produce a turpentiiie nimontarninated wit,li decomposition products of tlie wood aiid rosin, the stcain distillatioil process was dcveloped. By this process the volatile oils occurring in the wood are removed without contarnin:ition. It w?s souii Sound tliat along with the turpentine occurred a previously uirkriown component of the resin with higher boiling points and gravity. Tlius was discovered an eiitirely new commercial product, which has been riamad “pine oil.” l l i e steam distillation process as first dsvclopcd was not long successful, since o d y the volatile oils u-ere recovered; hut when an additional operation was added to extract slid reeoirer the rosin, a new and perniancnt. industry, the extraction process, was set on foot. Its pruduets are steam-distilled wood t.urpentine, pine oil, arid wood rosin. Summary
The Parent of the Woad 1)isfillafion Charcoal Kiln
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tlir:rt!fr,re, the cl~arrodand tar, and 110 grea.t proportion of tlie latt,er has ever been utilizcd except as fuel at dhe plant. Ilcre we have ai1 industry which has dereloped remarkably in size, purity of products, and efficiency of operation-only to meet finally, from three separate sources, scwre competition in three of its main products.
Resinous Wood Distillation
The dist,illation of resinous woods has been handicapped its development by the enthusiasm of 1.he inventor and the promoter. I n this industry it ia apparently easier to raise capital fur radical departures from common practice t.lian for an adrlitiomal plant using a process of kiiowii value, and for the manuf:xt.ure of new but unkiiown products of supposedly fabulous value than for turning out staiidard items of known marketability. Consequently, the developnient of commonplace dependable processes has been hampered aiid the industry given n bad reputation. The notion of new, secret processes with wonderful yields of very valuable prodnebs is still active, although the only plants still operating successfully have used the simple, common principles of chemical engineering in working out their present processes. iii
From the first feeble attempts to improve the charcoal kihi and tar pit which were being made in 1876, the art has progressed until it now embraces three distinct and welldeveloped chemical industries-hardwood distaatiou, the destructive distillation of resinous wood, and the steam distillation and extraction of resinous wood. Although these may not be large as compared with some other chemical industries, they are important in furnishing a large number of >.aluahle chemical products, many of which are indispensable in the technical and manufacturing field.
National Wealth -4 recent report oi the Federal Trade Cominissioii estimates a marked increase in the national wealth as of 1932, which, after allowing far the difference in the purchasing power of the dollar,
gives a total oi 353 billiotis, an increase of 49 billions over 1912. In the same period our population has increased 15 per cent and OUT national wealth 16 per cent. Anyone with a liking far statistics will find in these data much that can be interpreted in terms of what scicnce does in creating national wealth. The report gives dwelling houses, furniture, and pcrsonal eRects 88 billions, agriculture 64, miiiing and manuiacturing 49, railroads and public utilities 46, government property 43, and all other wealth 64 billions. It is interesting to note that the wealth of noxiprofit institutions totals 14.5 billions, of which 7.6 billions are invested ir! educatioiial institutions, 1.2 billions in funds and community trusts, 8W millions in libraries, and 2W millions in museums. It would he interesting to know what the investment in our institutions of learning and allied organizations earns nhen measured by the constant additions being made to our nation’s wealth. It would give a complete answer to the question-does research pay ?
