T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
Nov., 1915
When wood is heated sufficiently in the atmosphere it tends to burn of course to residual ash, steam and carbon dioxide, for the most part. If the air is partially excluded we obtain residual charcoal and volatile products varying widely in composition, depending upon the extent of air exclusion, from the condition of almost complete combustion of volatile products, to practically entire elimination of combustion or atmospheric oxidation when air is excluded as completely as possible. The problem of the industry may be met therefore by heating the wood sufficiently to carbonize it and in such a way as to eliminate as far as possible any atmospheric oxidation of the volatile products, and a t the same time handle the distillates in such a way as to minimize refining or purification difficulties. Modern chemical engineering skill has met the conditions of reasonably efficient solution of the problem with fair success as is shown by the extent of the industry’ and without doubt it will advance still further. Every problem, however large, is merely a series of smaller sub-problems and each of these in turn is often resolvable into still other problems. I n studying the problem of any chemical industry it is natural to divide it as far as possible into: I-The nature of the demand or market for the products, or objectives of the industry; a-The chemistry involved; 3-The operations or engineering involved. The chemistry of the hardwood distillation industry finds its basis in the phenomena attending destructive distillation. Much more should be known about destructive distillation than is known. Our concern a t this time, however, is with the engineering. problems involved in the utilization of this chemistry. Suffice it to say in the matter of the chemistry involved, that the products of heating the wood, as is usually the case in destructive distillation, are gaseous, liquid (condensate) and solid (residual charcoal). The gas as a whole is combustible. The liquid is acid and in two (or three) nearly non-miscible phasestar (and oil) and dilute alcoholic acetic acid, with dissolved tar and other substances. CHEMICAL ENGINEERING OPERATIONS
The engineering operations of the industry group themselves mainly into four divisions as follows: I-Preliminary handling of raw material. 11-Destructive distillation proper or so-called primary distillation. 111-Treatment of the liquid distillate or secondary distillation. IV-Refining operations and derived product production. The latter is not generally connected with what is known as the Crude Hardwood Industry and will, therefore, be indicated with great brevity. The engineering operations themselves are as follows : I-PRELIMINARY HANDLING OF WOOD I-Harvesting
the timber
{ ~~~~~~g
2-Seasoning, transportation and storage 11-PRIMARY DISTILLATION (Destructive distillation. proper) 1-Loading oven cars 2-Charging and sealing ovens 3-Firing ovens (Distillation) &Condensation and fuel gas recovery 5-Pulling ovens (Discharging hot charcoal cars) &Cooling charcoal 7-Pulling charcoal coolers 8-Ageing charcoal 9-Screening charcoal Final Product: CHARCOAL FOR THE MARKET 111-SECONDARYDISTILLATION (of condensate obtained in II, 4 ) 1-Settling “ R a w Liquor” (condensate II. 4 ) 2-Separation of t a r (and oil) from “Raw Liquor” (continuous decantation) 3-Redistillation of settled t a r Cfor further recoziery of “ R a w Liquor”) from copper or wooden stills. 1 THIS JOURNAL,
7 (1915). 47.
913
of acid distillate [Oil added to “Boiled T Q Y , ”water added to original “ R a w Liquor” (condensate IZ, 411 5-Redistillation of settled “ R a w Liquor” Lfo? furthev Larry bodies elimination) from continuous copper stills 4-Condensation
&Condensation of “boiled liquor” 7-“Mixing” “boiled liquor” with lime (Seulralization) 8-Distillation of neutralized “boiled liquor” in lime-lee still (iron) 9-Condensation of weak alcohol-acetone IC--Settling or filtering lime-lee still residue (aqueous calcium acetate) 1I-Evaporation and crystallization of lime-lee residues 12-Drying (sacking, weighing, analysis) crystallized acetate of lime Product: GRAYACETATEOF LIME(80 PER CEKT) F O R TIIE h f A R K E T 13-Redistillation of weak alcohol-acetone for oil separation and concentration (Burcey pans, fractionation) 14-Condensation of alcohol-acetone in fractions Product: CRUDE8 2 P E R CENT ALCOHOL-ACETONE F O R i’dARKET OR REFIXERY IV-REFINING A K D DERIVEDPRODUCT MANUFACTURE
( a ) Alcohol: 1-Chemical treatment of crude alcohol (NaOH or HzSOa) 2-Distillation and condensation for elimination of chemicals, etc. 3-Fractional distillation in column still &Condensation with “heads and tails” elimination Product: REFINED METHYL ALCOHOLA N D ACETONE-ALCOHOL FOR MARKET
(b) Gray Acetate: 1-Distillation with sulfuric acid (or HCl) 2-Dust elimination from vapors 3-Condensation of acetic acid (Commercial) 4-Refining by redistillation and fractionation a f t r r chemical or electrical treatment ACETICACID FOR MARKET Product: REFINEDA N D CONCENTRATED ( c ) Gray Acetafe: I-Destructive distillation 2-Dust elimination from vapors 3-Condensation of crude acetone and oils +Separation of oils from acetone 5-Chemical treatment for acid elimination 6-Redistillation for “white oil” elimination 7-Fractional distillation of acetone 8-Condensation Product: ACETONE FOR THE MARKET
Each and every one of these operations calls for its own special form of apparatus or construction and modifies to a varying extent the design and operation of the plant. They are the essential operations or chemical engineering proper which must be carried out to secure the results obtained in firstclass practice. There has been indicated also, in a limited way, how some of these operations must be carried out. Sufficient preliminary discussion of the development of the industry has been given to illustrate the connection which appears to have existed between the development of both chemical knowledge and engineering skill, and the growth and development of this industry. I n concluding I must express my indebtedness to Mr. Edward H. French, to whom I owe my first opportunity (a number of years ago) of working upon the problems of this industry, upon which he was himself engaged, and who has been of much assistance in securing plant photographs from which slides have been prepared. OHIO STATE UNIVERSITY, COLUMBUS
WHAT CHEMISTRY HAS DONE TO AID THE UTILIZATION OF WOOD By S. F. ACREE
An attempt to discuss fully the influence of chemistry on the utilization of waste wood leads so deeply into practically all fields of Chemistry that a paper of this kind must necessarily be limited t o a small number of topics. Attention is given, therefore, to those phases of this subject which are of most importance commercially and which seem t o show greatest promise for the future. The number of eminent chemists who have contributed to the few subjects to be discussed is so large that i t is impossible to treat their individual researches as they deserve. Such being the case, a brief mention here and there of a few investigations by the Forest Service, with which the writer
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T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
is personally familiar, will not be understood as a failure to appreciate the work of others. The technical processes involved in the apparently simple distillation and extraction of woods lead both into the abstruse problems of thermodynamics and into the most refined technique of organic chemistry, and advances in these investigations have been described by Klason, Wislicenus, Klar, Withrow, Palmer, and others. The distillation of waste hardwoods is now one of the most important industries in this country and has reached a high state of efficiency in the hands of Messrs. Stevens, Quinn Brothers, Troy, Gaffney, Clawson and the Cleveland Cliffs Chemical Company. There are over roo plants in operation, in which about I,ZOO,OOO cords of wood are distilled annually. The chief products obtained are charcoal, acetic acid, methyl alcohol, wood oils, and wood tars, and these are so valuable that extended researches have been made by the Forest Products Laboratory to increase the yields. The quantitative studies on the regulation of the reactions have resulted in improved processes and increased earnings. Charcoal is the least valuable by-product of the wood distillation industry, but is used in large quantities as a household.fue1, in decolorizing grain alcohol and other liquids, in the manufacture of gunpowder and lubricants, and in’ the manufacture of fine charcoal steel. The acetic acid is utilized for the production of such substances as mordants for dyes, acetanilide, and sugar of lead. Acetone is produced by the distillation of calcium acetate and is used to the extent of 3,000,000 gallons annually in the manufacture of denatured .alcohol, chloroform, photographic films, celluloid, and, especially, explosives. Wood alcohol is one of the most striking illustrations which we have today of the value of chemistry and chemical methods in the purification and utilization of a waste product. When Mr. E. B. Stevens, President of the Wood Products Company of Buffalo, N. Y., constructed his first still out of a tin can and attempted to purify the evil-smelling distillate from a near-by wood distillation plant, he little realized what a tremendous future awaited his efforts as a n enthusiastic boy of seventeen. Today, crude 82 per cent wood alcohol is changed by simple chemical and physical methods into a product which has a purity of 99.95 per cent. This substance is used all over the world and new fields are being discovered for its utilization. The ~o,ooo,ooogallons produced in this country are used for making celluloid and similar products, dyestuffs, denatured alcohol, photographic films, formaldehyde, artificial leather, varnishes, shellacs, artificial rubber, and other substances too numerous t o mention, in whose manufacture and use hundreds of millions of dollars and large numbers of men are employed. European countries use nearly as much wood alcohol as the United States but chiefly for denaturing ethyl alcohol, for the manufacture of formaldehyde, for the methyl group of aniline colors, and for other purely chemical purposes. There is a t present no substitute for wood alcohol in the preparation of the methyl groups of various dyes, especially the violets and blues, and hundreds of millions of dollars are invested in the dyestuff business and in the wool, cotton, linen, and silk cloth industries and others using these colors. These dyes are used today in many cases of disease in staining tissues and bacteria, thus allowing medical men to make a proper diagnosis. Wood alcohol acts as a poison when taken internally, or when its concentrated vapors are inhaled in enclosed spaces, and sometimes produces blindness and death under these conditions. The wood alcohol manufacturers themselves condemn its use as such in any article of food, drink, or medicinal or toilet preparation. When, on the other hand, these objectionable properties are destroyed by chemical changes, it becomes one of the substances necessary for the production of other products for the protection of the health of the community. Pure methyl (wood)
Vol. 7, No.
II
alcohol is the only substance which can be converted on a commercial scale into formaldehyde, which is used universally for disinfection against such contagious diseases as smallpox, scarlet fever, diphtheria, tuberculosis, infantile paralysis, and spinal meningitis in its epidemic form. It should, furthermore, be pointed out that many native and alien crop diseases are becoming epidemics in this country and destroying yearly from ten to twenty million dollars worth of foodstuffs, besides infecting the farming lands and rendering them far less valuable for the production of certain crops. The United States and State Governments prescribe formaldehyde as the disinfectant for the seeds, which are sterilized before planting. By this disinfection crop losses, due to certain fungi, can be greatly reduced. Formaldehyde is practically the only efficient disinfectant which can be legally employed in embalming the dead and preventing the spread of contagious diseases causing their deaths. Formaldehyde and phenol are the basis of the manufacture of bakelite which is now used in tremendous quantities in large chemical apparatus in certain industries, and is finding wide use as insulating material in the electrical world. Formaldehyde is, furthermore, used in large quantities in the preparation of various dyes discussed above. Another by-product from wood distillation, which has received little consideration up t o this time, is the hardwood tar. This substance has a large percentage of derivatives which should find wide use in chemical industries. Already we find small quantities of these tars in use as wood t a r creosotes for the preservation of wood, and the insufficient production of coalt a r creosote in this country will, without doubt, enable wood tar creosote to come into its own, especially as it has been found to have a high toxicity toward certain fungi. I n the field of distillation of softwoods, we find that some of our most important commercial products are obtained by this combination of physical and chemical methods. The chief products are turpentine, pine oils, t a r oils, rosin and charcoal. The turpentine is used chiefly in the production of paints, varnishes, and shellac. The pine oils are used t o a large extent as solvents and as medicine. The t a r oils are used for treating such things as rope and fish nets in order t o preserve them in salt water. The rosin is used in making soaps, paper sizing, varnishes, and shellacs. Charcoal is used chiefly for fuel. The value of the paper and pulp industry in this country is apparent immediately when we think of the benefit derived from the tremendous number of books, periodicals and of newspapers Wood pulp is used for making men’s summer clothes, papers of all kinds, binder twine to replace sisal, sacks, filter papers, and rugs. It is used for making fiber vessels, vulcanized fiber for electrical insulation, and is now the basis of viscose which is finding a wide field of application. Viscose is colloidal cellulose which can be made into “fiber silk” thread and sausage coverings. The thread can be woven alone, or in combina‘.ion with cotton or silk, into all kinds of fabrics, such as artificial silk socks, neckties, and cloth, all of which can be dyed beautifully in any color. Surgeons’ thread, and erasers of this material are cheap and efficient. Cellulose can be made in a very pure form from certain woods and has been used extensively in explosives. Not only is i t converted directly into nitrocellulose but we find that wood flour is used very extensively as an absorbent in the manufacture of dynamite. The very finely divided wood flour absorbs 60 per cent of nitroglycerine and is more efficient than kieselguhr. This wood flour is also used in making certain grades of linoleum and is much cheaper than cork. Turning now t o the dyestuffs, we find that the aniline industry of Germany has not entirely driven vegetable colors from the market. A number of West Indian and South American woods, such as the fustic, logwood, Brazil wood, and peach wood, are imported into this country and the Forest Products Laboratory
Nov.,
1915
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
has recently been instrumental in calling the attention of manufacturers to the fact t h a t Oklahoma and Texas contain large quantities of Osage orange' which can be used very cheaply as a source of a valuable yellow dye for textiles and leather. The enormous leather industry is dependent not only upon the use of vegetable dyestuffs but especially upon the tannins obtained from hemlock, oak, chestnut and other materials. Certainly the preparation of tanning material involves the most delicate physical and chemical, as well as biological, operations, a s has been shown by the work of Proctor, Stiasny, Levi, Balderston and others. That the production and consumption of ethyl alcohol in the United States is an important activity is emphasized by the fact that the taxes on distilled spirits and fermented liquors amounted in 1913 to S223,000,000,which was over 6 j per cent of the entire internal revenue of the country. It will be recalled that over IOO years ago Braconnot carried out a n investigation in which wood was hydrolyzed by acids into glucose, which was then fermented into ethyl alcohol. In recent years, this problem has been studied energetically by Simondson, Classen, Cohoe, Ewen and Tomlinson and others, and four plants were erected in the United States. Three of these failed but the experience gained thereby and the research work on this problem by the Du Pont de A-emours Powder Company and the Forest Products Laboratory have now made the outlook for this industry very bright. It is believed that a plant could now be constructed under proper conditions of location, transportation, and other such factors, which would make possible the manufacture of ethyl alcohol from sawdust a t a price which would allow it to compete with the production of ethyl alcohol from molasses. Especially important in this connection is the discovery by the Forest Products Laboratory that western larch contains about IO per cent of a galactan yielding only galactose. If fermentation methods can be devised for the commercial conversion of galactose into ethyl alcohol, the western larch butts, which are a t present waste material, will become a very cheap source of alcohol. The increased efficiency of alcohol a t high pressures in internal combustion engines may thus place this material in a position where it can compete with gasoline when this becomes scarcer. The preservation of woods in railroad ties, telegraph poles, heavy bridge timbers, structural timbers, and in houses, is one of the most important phases of forest conservation before the public today. In this preservation over ~oo.ooo,ooogallons of coal-tar creosote, water-gas-tar creosote, and mixtures of these chemicals with petroleum residues are used. Aqueous solutions of zinc chloride, sodium fluoride, copper sulfate, and many other inorganic chemicals are also used very widely. bIillions of dollars are thus involved in a n industry whose business it is primarily to preserve this investment. It follows then that chemical methods must be developed for the analysis of the creosotes, and that chemical studies should lead to the manufacture of better materials a t lower cost. The Forest Products Laboratory has made investigations on the analysis of creosotes and the isolation of their many constituents, together with tests of the toxicity of these compounds toward wood-destroying fungi, and these researches have shown that great improvements could easily be made in the preservation of wood by the use of better specifications for the materials and methods of treatment. In the above paragraphs, only a few of the industries involving the utilization of chemical methods in the use of waste wood have been discussed. But daily the problems along these lines are being extended and the future will probably show that the application of chemistry t o the utilization of forest products extends into nearly every field of human endeavor. FOREST PRODUCTS LABORATORY A X D UNIVERSITY OF WISCOSSIN MADISON
THIS JOURNAL. 6 (1914), 462.
*915
THE TANNIN CONTENT O F PACIFIC COAST CONIFERS By H. K BEKSONA N D THOS G. THOMPSON
The tannin extract industry of the United States utilizes for its raw material chestnut wood and the bark of the Eastern hemlock and the chestnut oak. From these species a standard extract containing 2 5 per cent tannin is manufactured, annually amounting t o over ZOO,OOO,OOOlbs. An equal or greater quantity of extract is either imported, or made from materials imported, of which quebracho is of chief importance. I n view of the large sources of available supply of tannin-containing materials on the Pacific Coast, a study n a s made of the tannin content of Western hemlock, Douglas fir and Western spruce. WESTERN HEMLOCK
The Western hemlock extends from Slaska to Marin County, California, and eastward, in some places, as far as bIontana, thriving in the cool, moist climate characteristic of western Washington and Oregon. It grows along with spruce, cedar and fir, often being left as useless by the timber cutters. An excellent example of the distribution of these trees is found in a recent survey of the merchantable timber of the Olympic h'ational Forest It was found that out of this forest, containft. of timber, 35 per cent was n'estern heming ~j,~oo,oOO,ooo lock, 37 per cent Douglas fir, and the remainder spruce and cedar The bark of the Western hemlock is thinner than that of the Eastern hemlock, but, as is commonly known, it contains a higher tannin content. This fact was first brought to the attention of the Washington public in 1893 when several samples of the bark were submitted to Dr. H. UT.Wiley, who reported the following analyses: SAMPLE hloisture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Total so!ids.. . . . . . . . . . . . . . . . . . . . . . . . . . Soluble solids., . . . . . . . . . . . . . . . . . . . . . . . Reds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S o n - t a n n i n s . .. . . . . . . . . . . . . . . . . . . . . . . . Available t a n n i n s . . . . . . . . . . . . . . . . . . . . . . \%700dyfiber.. . . . . . . . . . . . . . . . . . . . . . . . .
Ashford 10.55 24.03 22.55 1.44 6.59 16.00 65,42
Enumclaw 10.01 22.16 20.58 1.58 5.76 14.86 6 i . 83
The first results that were published' calling attention to the differences in percentage of the tannin content of the n'estern and Eastern hemlock were the following analyses made by H. G. Tabor of hemlock bark from trees in Washington, Pennsylvania and Quebec: WashSOURCE: ington T a n n i n , . . . . . . . . . . . . . . . . . . . 17.04 Son-tannin... . . . . . . . . . . . . . 6.40 Reds... . . . . . . . . . . . . . . . . . . . 1.56 Woody fiber.. . . . . . . . . . . . . . 75.00
Pennsylvania
13.28 7,52 3.48 i5,72
Quebec 10.16 4.56 1.52 83.36
iVestern hemlock bark has been used as the exclusive tanning agent in a t least one tannery in Washington for a number of years. This concern manufactures chiefly skirting leather for saddles. I t s larger use has been prevented by the lack of tanneries, due to economic reasons, rather than unsuitableness. The prevailing cost of hemlock bark f . 0 . b. tannery has been $1 I.j o per cord. EXPERIMENTAL
Inasmuch as few references to the tannin content of Douglas fir and J\'estern spruce could be found, and as far as is known no effort has ever been made to demonstrate the tannin content of sawmill waste from these species, an experimental study was undertaken. PREPARATION OF SAMPLE-The sawmill Waste taken for analysis consisted of bark, slabs, and sawdust from the crosscut saws. Samples of IOO lbs. were taken for the bark, from 100 to 150 lbs. for slabs, and about z j lbs. for the sawdust. The bark and the slabs were each reduced in a Mitts and Merrill chipper and the chips quartered to obtain an average sample. Before subjecting the sample to analysis it was further reduced to a fine powder in a Grumbaugh mill. 1
H i d e and Leather, June 24, 1893
