Aug., 1916
T H E J O C R S d L O F I N D U S T R I A L z4.VD E N G I Y E E R I N G C H E M I S T R Y
V-That hydrogen is produced from a n oil even when the cracking takes place in hydrogen. VI-That considerable absorptions of hydrogen t a k e place when a n oil is. cracked in an atmosphere of hydrogen, and this absorption is greater t h e higher t h e concentration of hydrogen, t h e higher t h e temperature (within t h e range studied), and t h e lower t h e oil rate. VII-That propylene and higher olefins constitute approximately one-third b y volume of t h e illuminants of t h e gas. VIII-That the proportion of t a r increases with decrease in temperature, and with increasing oil rate, particularly a t the lower temperatures. IX-That no marked and consistent difference in t h e amount of tar formed when an oil is decomposed alone or in hydrogen a t temperatures of 723' C. or below is noticeable. At 8 2 j ' C. less t a r is formed when t h e oil is cracked in hydrogen. The tars formed below 7 2 3 ' C . are in large part unchanged or partly changed oil, whereas those t a r s formed above 800' C. are essentially composed of synthetic products. X-That the reactions which result in decreasing t h e proportion of illuminants are t h e most rapid. XI-That the presence of hydrogen during t h e decomposition of an oil has t h e effect of increasing largely t h e proportion of the carbon of t h e oil appearing as hydrocarbons in t h e gas. XII-That v i t h i n the temperature range studied the volume of illuminants produced per volume of oil increases with t h e temperature with one slight exception. The formation of methane is gre'ater t h e higher t h e temperature. The formation of ethane is not large a t a n y temperature and therefore t h e primary decomposition of a n oil involves chiefly a splitting off of methane rather t h a n ethane or higher homologues. XIII-That a temperature of 823 ' C.is desirable in decomposing an oil provided t h a t too great opportunity for extensive secondary and tertiary change is not given. XIV-That with correct design of apparatus, a n d proper adjustment of temperature, rate of oil feed, and concentration of hydrogen it is possible t o obtain gases of widely varying compositions. The authors wish t o extend t o Professor Floyd J. Metzger, Professor Samuel A. Tucker and Dr. Clive M. Alexander their thanks for valuable help a n d suggestions received. DEPARTMENT OF CHEMICAL ENGINEERIBG COLUMBIA UBIVERSITY, NEW YORK CITY ~~~~
STUDIES ON THE EXTRACTION OF ROSlN FROM WOOD. I-EXPERIMENTS USlNG A PETROLEUM SOLVENT By R. C. P A L Y E RA~ N D H. R . BOEHMER?
Received April 2 1, I9 16
PURPOSE O F W O R K
From a technical viewpoint, t h e process of extracting rosin from wood with chemicals offers a promising possibility for t h e utilization of "fat" stumps and 1 Chemist in Forest Products, Forest Products Laboratory, Madison, Wisconsin. 2 T h e d a t a obtained in these experiments mere submitted b y this author in partial fulfilment of the requirements for the degree of B.S.in Ch.E. in the University of Wisconsin.
695
other waste resinous wood. I n the simple steam distillation process only t h e volatile constituents of the wood are recovered and this method is no longer industrially feasible on this account. I n the destructive distillation process, the products are charcoal, t a r , and a turpentine more or less contaminated with products from the destructive distillation of t h e rosin and wood substance. This turpentine, a t best, does not bring as high a market price as steam-distilled wood turpentine, although the recent introduction of temperature-controlled processes has removed this objection t o a large extent. Compared with these two processes. t h e so-called solvent or extraction process affords t h e recovery of wood turpentine and pine oil comparable in quality and value with t h e oils from steam distillation and also a medium grade rosin whose market value, under normal conditions, is practically equal t o t h e combined value of charcoal and t a r from t h e destructive distillation process. However, t h e market value is less likely t o fluctuate for t a r and charcoal t h a n for rosin. Strictly speaking, t h e extraction and distillation processes are not comparable, because t h e products are quite different. These processes represent the two types which taken together cover most of the possible products t o be obtained from resinous wood. Of t h e several different processes proposed for treating wood. t h e destructive distillation method, which is b y far t h e oldest, is also a t t h e present time apparently t h e best established from t h e standpoint of profitable commercial 0peration.l The principal difficulties t h a t have been encountered in t h e extraction process have been: ( I ) an unstable market price for rosin, and ( 2 ) high cost of operation, due largely t o a n excessive loss of solvent. I n attempting a solution of these difficulties, there are then a t least two lines of attack which may give this process a better opportunity for commercial success: ( I ) obtaining another product which would not be subject t o very great market variations, and ( 2 ) decreasing the operating cost. The use of the extracted wood as a raw material for paper pulp has been suggested several times as a possible solution of the problem of obtaining another product. Extraction b y t h e usual method requires wood so finely divided (shredded wood) t o yield a high proportion of the rosin t h a t t h e extracted material is not suitable for pulp. If t h e wood is large enough for pulp, the yield of rosin is decreased. Considering the high operating costs as due largely t o t h e loss of solvent, i t would seem t h a t the problem here is largely mechanical, and its solution should not offer very great difficulties. With these ideas in mind, it was felt t h a t a careful study should be made of some of t h e fundamental operating variables of the process. The experiments were carried on a t the Forest Products Laboratory, Madison, Wisconsin. The material consisted of longleaf pine stumps from Louisiana, donated b y t h e Long-Bell Lumber Company of Kansas City, Missouri. Acknowledgment is made t o Mr. S. D. Wells, Engineer in Forest Products, of t h e section ,
1 'I'HIS
JOURN.4L.
6 (1914), 151.
696
T H E J O U R N A L OF I N D U S T R I A L A.VD E.VGI.VEERING C H E . M I S T R Y
of pulp and paper, for making t h e experiments on t h e suitability of extracted chips for pulp. D E S C R I P T I O N OF PROCESS
About fifteen patents have been granted in the United States for extraction processes and a p p a r a t u s since 1909, and one qr two plants were built a n d h a d been operated before t h a t time. The different p a t e n t s vary chiefly in t h e t r e a t m e n t of the wood hefo:e and after applying t h e solvent, in t h e manner of applying t h e solvent, and in t h e solyent itself. In general, t h e process, as carried o u t in t h e commercial plant, consists in first steaming t h e finely divided wood t o recover t h e volatile constituents (turpentine and pine oil), followed in some cases b y evaporating o u t of t h e wood as much of t h e condensed steam as possible. T h e solvent is then applied t o t h e wood t o dissolve o u t the rosin. After extraction, t h e wood is treated t o recover t h e solvent adhering to: or absorbed b y t h e chips. Evaporation of t h e solvent leaves t h e rosin as a residue, t h e solvent being recovered for subsequent extractions.
Vol. 8, No. 8
I t was found, however, t h a t t h e material contained a t least 20 per cent boiling under i o o , a portion hoiling as ION as 3 0 O . l T h e solvent was, therefore, fractionated in a laboratory column (4 in. in diameter), t h e fraction below i o o C. being removed. By distillation in a Hempel column t h c solvent used gave 4 per cent boiling below ioo and 9j per cent boiling below l j o o . ExTRAcrIos-It was desired t o make t h e laboratory study as comparable as possible with extraction in a continuous commercial extraction battery. In an extraction system of this type, all units receive exactly t h e same t r e a t m e n t and in no case is fresh solvent run on t o fresh material, b u t t h e solvent most nearly saturated with t h e substance being extracted is run on t o fresh material a n d t h e most nearly spent material
EXPERIMEXTAL
APPARATUkThe apparatus used in t h e rxper;ments was a n extraction b a t t e r y composed of three retorts, A , B , a n d C, shown in Fig. I. T h e chips were placed in the perforated baskets, D , each retort holding f r o m 3 0 t o 35 Ibs. of wood. T h e b a t t e r y was so arranged t h a t t h e solvent could be forced b y means of a pump, E , t o a storage t a n k , F ,from which i t flowed b y gravity into a n y one of t h e retorts a n d from t h a t retort t o each one below it. Each u n i t was independent of t h e others so t h a t different operations could he carried on a t t h e same time. Each retort was also connected t o a vacuum p u m p , G, through a condenser, H. a n d receiver, I , and equipped with a n open coil for direct steam a n d closed coils for heating t h e solvent. As i t was desired t o boil t h e solvent in contact with the chips t h e a p p a r a t u s was so arranged t h a t this could be done without decreasing t h e solvent b y evaporation. This was accomplished b y connecting the vapor outlet line of each unit t o a condenser, J , and receiver or t r a p , K , placed above t h e battery. T h e t r a p was connected o t h e b o t t o m of each retort and t h u s allowed t h e vaporized solvent, after i t was condensed, t o flow continuously back into t h e retort as in a reflux condensing apparatus. By connecting the t o p of each retort t o t h e t o p of t h e trap, t h e vapor conditions were equalized and t h e solvent was prevented from backing up. With these “equalizers” open, t h e solvent in a n y retort could be boiled under pressure for a n y desired length of time with a constant reflow of t h e condensed vapors. The simple still, L , was used for t h e evaporation of t h e saturated solvent t o recover t h e rosin. T h e still was equipped with a steam jet and was connected through t h e receiver, M , t o t h e vacuum p u m p t o facilitate t h e removal of water and heavy oils from t h e rosin. soLvEw-Since a petroleum distillate has been most frequently used commercially a s a solvent there was selected for t h e experimental work, a special gasoline furnished on a guarantee t o boil between 70 and I j o o C.
Fro. I - - E r r a ~ c n o a BATIBXY
receives a final t r e a t m e n t with fresh solvent. This. condition was approximated in a laboratory test, providing a system of four washes for each unit b y . employing six solvents. Three of these were distilled a t t h e end of each r u n and three were used for thenext r u n without recovering the rosin. The method may he better explained diagrammatically b y referring t o Table I. Solvents I, I 1 and I11 in each r u n were distilled for t h e recovery of rosin, having extracted t h e rosin f r o m t h e wood in four retorts, while Solvents IV, V I In purchnriog solvents of this type comm~rdally.the importanceof contracts calling for cxtremcly rigid specifcations is indicated by this experience. With such a large proportion 01 e very low boiling lrnclion I in the solvent it would be irnporriblr to prevent a high solvent loss.
T H E J O C R S AL OF I N D U S T R I A L A S D EXGI-VEERING C H E M I S T R Y
Aug., 1916 RETORT
SOLVENT
1,
i
i
7--Ri~~ 1
:I 111
I--
2
TABLEI 3
,----RUN 1
2-
2
3
+ I1
+ I11 + I11
1v + 1v 1'
--+I1 I + IV --f + I1 --f I11 + I11 + 111 I V * IV + I V
+ vV I
v + v
vI
a n d VI become Solvents I , I1 and 111, respectively, for t h e next run. Solvent I , in Retort I ; 11, in Retort 2 ; and 111, in Retort 3 > represent t h e action of nearly saturated (theoretically) solvents on wood which has not been previously extracted. Solvent I\'. in Retort I ; V , in Retort 2 ; and V I , in Retort 3, represent t h e final extraction of nearly spent chips with fresh solvent. Before beginning t h e first run, a preliminary r u n was necessary in order t o secure Solvents I . 11, and 111, for t h e first test. After t h e retorts were charged in these tests, they were not opened until the dried extracted chips were removed. The procedure used in conducting a n y test was briefly as follows: T h e chips were first steamed under 30 lbs. pressure' until no more turpentine and pine oil were obtained; t h e retorts were then connected t o the vacuum p u m p from 30 t o 60 min. t o remove as much of t h e moisture as possible, steam being kept in t h e closed coils t o facilitate evaporation. The solvent was t h e n introduced until the chips were just covered and was t h e n brought t o boiling b y means of t h e steam in t h e closed coils. The reflux system was open so t h a t t h e vaporized solvent would condense, a n d flow back into the retort. In case t h e extraction was conducted under pressure t h e valves connecting t h e retort t o t h e reflux were closed until the desired pressure in t h e retort was reached. The line connecting t h e retort with t h e reflux was then opened a n d t h e pressure controlled b y t h e amount of steam passed into t h e closed coils. After extraction t h e solvent was transferred t o t h e next retort, or in case i t was t h e last extraction for t h a t solvent, it m7as passed through a condenser which delivered i t cold t o t h e container. When t h e extraction was made under pressure, it was better t o relieve t h e pressure before drawing out t h e solvent; this was readily done b y turning off the s t e a m and allowing condensation t o continue in the reflux. When t h e solvent was drained o u t after t h e last extraction, t h a t remaining in t h e chips was removed b y steaming first at atmospheric pressure until no more solvent came off, and finally a t 30 lbs. pressure for a few minutes. To insure t h a t all t h e solvent was removed, t h e retort was t h e n connected t o t h e vacuum pump for about one hour. I n only a few cases, however, was any more solvent recovered in this last step. As soon as each solvent was removed after final extraction it was thoroughly stirred, and a sample taken. The weight of each solvent was taken before it was used in a n y r u n and after its final use in t h a t run. T h e intermediate weights when a solvent passed from one retort t o t h e next were not taken. In other words, t h e total amount of wood in t h e three units THISJOURNAL, 4 (1912). 789; also F S Bull 109, "Distillation of Resinous Wood with Saturated Steam "
697
of the battery was considered as t h e charge for t h e r u n rather t h a n t h a t in e a c h ' r e t o r t as a separate unit. Since only three solvents were redistilled in a n y run and these contained some rosin from a previous run, it was not possible t o determine t h e rosin yield from the actual rosin recovered b y t h e redistillation of t h e solvent. The yields were determined b y a n analysis of the solvents. T h e total yields from several runs checked very well with t h e analyses. ANALYSES
The efficiency of any extraction was based on a comparison of the amount of rosin in the solvents, as determined b y an analysis, and the amount of rosin contained in the charge, as determined b y an analysis of an average sample of the wood. WOOD--A sample of t h e charge was taken b y quartering t h e wood in each retort until the desired amount (about '/2 lb.) was obtained. X portion of the sample from each retort was &hen ground t o the fineness of sawdust and a moisture determination made by the xylol method,' generally employed in estimating moisture in wood which contains a volatile oil. An equal portion of the finely ground sample from each retort was extracted in a Soxhlet with chloroform. On drying the extracted sample t o constant weight a t 110' C. the weight of t h e wood free from moisture, rosin, and volatile oil mras obtained. The extract from the Soxhlet was then evaporated in an oil b a t h kept a t I j o ' C. After t h e chloroform had all distilled off a small jet of steam a t slightly reduced pressure was passed through t h e rosin. This was continued for '/* hr. and the residue was then dried by using a much higher vacuum for i,'2-hr. intervals, without t h e steam, until t h e rosin showed a loss of less t h a n 0.2 per cent for two successive treatments. Continued heating caused some decomposition, so t h a t drying could not be carried t o constant weight.. T h e final residue was t h e n taken as rosin. Since moisture and rosin and t h e extracted wood were determined t h e volatile oil was estimated b y difference. T h e method is not entirely satisfactory, b u t since it is not practicable t o determine volatile oil in so small a sample, and thus determine rosin b y difference, it was felt t h a t rosin could be determined as t h e nonvolatile chloroform extract. Duplicates checked within 0.003 t o 0.005 per cent and errors t h a t were large enough t o be of consequence t o the experiment fell back on t h e sample itself. I t is, furthermore, not strictly correct t o compare t h e petroleum extraction with t h e chloroform control since there were probably small portions of t h e rosin t h a t were insoluble in petroleum b u t were soluble in chloroform.2 T h e extraction efficiencies were, therefore, lower t h a n if based on the total petroleum soluble rosin present in t h e wood. EXTRACTIOK-The yield of rosin in the tests was determined, as stated above, by an analysis of t h e different extracts. The amount of rosin in a weighed portion (about 2 0 0 g . ) was determined in practically t h e same manner described for estimating t h e rosin 1
F. S. C ~ Y C 134, . "Estimation of Moisture in Creosoted Wood '' .Men, "Commercial Organic Analysis." chapter on Colophony.
T H E JOURNAL OF IiVDUSTRIAL A N D ENGINEERING CHEMISTRY
698
FIG 11-EFFECT
OF
Chip, 8/18 in. Pressure, 0 lbs
TIME
FIG 111-EFFECT
OF
PRESSURE Chip, 3 / l h in. Extraction, 15 min.
FIG 1x7-EFFECT
OF
CHIP Pressure, 30 Ibs. Extraction. 1 5 min OF
in t h e chloroform extract, except t h a t t h e residue was not steam-distilled because no appreciable amount of high boiling oils, such as pine oil. was left in t h e wood and rosin after the chips were thoroughly steamed.
SIZE
FIG V-EFFECT
OF
MOISTURE Chip, 3/16 in , Pressure, 30 Ibs , Extraction, 15 min.
T'ol. 8, S o . 3
FIG VI-EFFECT
OF R O S I N CONTENT Chip, 8/16 in , Pressure, 3 0 Ibs , Extraction, 15 min
traction. The curve is obtained b y plotting the percentages of rosin recovered as ordinates, and t h e time t h e solvent was in contact with t h e wood as abscissas. Referring t o Table I, which shows t h e procedure used in t h e test, it is seen t h a t in any run Solvent I SCOPE O F EXPERIMENTS is in contact with t h e wood only for the unit time, Solvent 11, howThe experiments in this first series included a study which is 1 5 min. for R u n I . of the more important fundamental operating variables ever, is in contact with the wood twice as long as on the efficiency of t h e extraction: ( I ) time, ( 2 ) pres- Solvent I! Solvents I11 and I'I' three t i m e s a s l o n g as sure, (3) size of material, (4) moisture. and (5) effect Solvent I ? and Solvents V and V I for t h e same t i m e of rosin content on the percentage yield of rosin, as Solvents I 1 and I , respectively. The units on t h e based on t h e amount originally present. The tests abscissa, therefore, represent t h e progress of extracalso included a preliminary study of t h e suitability tion. Since each solvent was analyzed before i t s of t h e extracted material for paper pulp. Two sizes first and after its last application, the proportion of chips, averaging 3,'16 in. and j l s in. with the grain of the total rosin extracted b y each solvent in any of t h e wood, were selected for the tests. The 3/i6-in. run could be determined. chip is larger t h a n t h e usual commercial chip used I t will be seen t h a t t h e effect of increasing the t i m e in the extraction process, b u t is considered the minimum from I j t o 45 min. is slight for the three sets of condisize for making pulp. T h e material was prepared tions used, and for practical purposes I j min. is eviin a semi-commercial pulp chipper. The wood in dently the maximum time necessary. I n Runs 3 and each case comprised t h e whole of the s t u m p including 4. which gave t h e highest yields, the efficiency was inthe outer bark All of t h e stumps had the roots re- creased only 2.1 per cent when the time was inmoved and were practically free from earth and sand. creased threefold. I n Fig. I 1 it will be noticed t h a t in the I j-min. extraction a larger proportion was reTABLE 11-EFFECT O F \'.4RIOIJS FACTORS Ob EXTRACTIOR OF R O S I N covered with the first two solvents t h a n when the time PRES% ROSIN EFFECT R u n TIME CHIP SURE ROSIN YIELD was 4 j min. This same condition was shown in ILLUSTRATED h-o Min. In Lbs. IN W o o n Per cent 29.92 72.6 3/16 0 1 15 TIXE corresponding curves for Runs 3 and 4 and 1 1 and 12, 25.10 75.0 3x16 0 2 4.5 23.00 91.60 3,16 30 3 15 but no logical explanation of this was made evident 3;16 30 25.92 93.70 4 4.5 during the experiment. 5.8 30 12.90 68.5 11 15 30 12.23 68.9 518 12 45 E F F E C T OF PRESSURE-The progress O f t h e extrac29.92 72.6 3/16 0 1 15 PRESSURE 30 27.43 94.3 3/16 6 15 tion for Runs I , j and 6 , shown in Fig. 111, is typical 55 3/16 5 15 29.35 82.3 of t h e effect of pressure. The figure shows t h a t the 13.0 0 25.1 2 45 3/16 93.7 30 25.92 3/16 4 45 rosin recovered was increased from 7 2 . 6 per cent 88.8 15 3/16 30 10.73 SIZE OF C H I P . . . . . . . . . . . 9 t o 94.3 per cent b y increasing the pressure from 68.5 15 30 12.9 I1 o t o 30 lbs. At g j lbs. pressure there is an ap68.9 45 5/8 30 12.5 12 parent break in the curve, and a decided decrease 88 2 30 10.i3 9 1.5 3, 16 MOISTURE,H i g h , . . . . . 10.7 72.1 3/16 30 in per cent recovery as compared with 30 lbs. pressure. 10 15 Low. . , . , . , Since, in a study of the penetrance of creosote in longROSIX C O X T E N T . .. . . . , , 7 I5 3/16 0 13.32 i0.8 1 15 3/16 0 29.92 73.6 leaf pine heartwood a t t h e Forest Products Labora30 10.73 88.8 9 15 3/16 3 15 3/16 30 23.00 91.6 tory,l a decided decrease was noted as t h e pressure 6 IS 3/16 30 27.43 94.8 was increased from 50 t o 7 j lbs., the cause of t h e deRESULTS creased efficiency of extraction may be a physical E F F E C T OF TIafE--Fig. 11, based on t h e results of : U. S. D e p t . of Agric., Bull. 101, "Relative Resistance of Various Runs I and z (Table 11), shows t h e progress of t h e ex- Conifers t o Injection with Creosote."
,4ug.,
I9 I6
T H E J O C R N A L OF I Y D C ' S T R I A L - 4 N D E N G I S E E R I N G C H E M I S T R Y
one. I t seenis more probable, however, t h a t t h e explanation is more of a chemical nature a n d may be due t o a n increase of t h e insoluble constituents of t h e rosin a t t h e higher temperatures, although there mas no apparent effect of t h e higher temperatures on t h e quality of t h e rosin recovered. T h e effect of increasing t h e pressure in t h e 45-min. extraction was practically t h e same as for t h e shorter time. E F F E C T O F S I Z E O F CHrP-Fig. I v shows t h e curve of extraction for Runs 9 a n d 11. Increasing t h e size of t h e chip t o 5 / 8 in. decreases t h e efficiency of extraction from approximately 90 t o about 7 0 per cent, a n d t h e result is practically independent of t h e time of extraction. I n t h e studies of t h e penetrance of creosote i n longleaf pine heartwood referred t o above, i t was also shown t h a t t h e ratio of longitudinal t o radial penetration was 26 : I , a n d of longitudinal t o tangential was I O O : I . For practical purposes t h e action of t h e solvent is, therefore, almost entirely in t h e longitudinal direction, which is also t h e same direction as most of t h e resin ducts, t h a t is, with t h e grain in t h e wood. T h e decrease in t h e rosin removed from t h e longer chips is t h e n undoubtedly a question of decreased penetration of t h e solvent into longer resin ducts. Since giving t h e solvent a longer time t o penetrate does not increase t h e yield, as seen in Runs 11 a n d 1 2 , ~it seems safe t o predict t h a t additional pressure is necessary t o penetrate t o t h e center of t h e longer chips. A continuation of those studies will determine t h e accuracy of this supposition. E F F E C T O F MOISTURE-After steaming t h e chips for t h e removal of volatile oil preparatory t o extraction, it was t h e usual procedure t o pull a vacuum of about 20 in. on t h e retort for '/z hr., t h e retort being kept hot b y means of steam in t h e closed coils in order t o remove as much as possible of t h e excess moisture caused b y steaming. I n general, t h e water removed in this way was equivalent t o about 30 per cent of t h e dry weight of t h e wood, b u t t h e ratio of this amount t o t h e total moisture in t h e chips after steaming was not determined. As several patents call attention t o this feature of t h e process i t was desired t o determine its effect. A run was made, therefore, in which t h e vacuum was omitted a n d t h e solvent was r u n directly on t o t h e chips after steaming. The results of this run compared t o a similar run in which t h e vacuum was used are given in Table TI a n d t h e progress of t h e extraction for t h e two runs i; shown in Fig. V. T h e effect of removing a comparatively small i m o u n t of moisture by t h e vacuum t r e a t m e n t is more pronounced t h a n might be supposed, since t h e efficiency is increased over I j per cent. I t will be noted in t h e curve t h a t t h e extraction is most retarded a t t h e s t a r t ; a n d it is, therefore, quite possible t h a t t h e excess of moisture is removed b y t h e first wash, after which t h e extraction proceeds more normally. When t h e water has once boiled off with t h e gasoline vapor 1 T h e more pronounced effect of increasing t h e time used in R u n 4 t o t h a t used in R u n 9 m a y be largely explained b y t h e higher rosin content of t h e wood used in R u n 4, a s will be shown in t h e discussion to foiiow.
699
a n d , on condensing ; n t h e reflux, flows back into t h e bottom of t h e retort, it probably does not interfere t o a n y extent with t h e extraction. By taking t h e condensed solvent from t h e t o p of t h e t r a p in t h e reflux line it would be possible t o get rid of this excess water in a short time, since t h e moisture could be drawn off a t t h e bottom of t h e t r a p a n d t h u s be removed from t h e system. With such a n arrangement, increasing t h e time of extraction should t h e n give almost as high efficiency as when t h e chips are dried b y t h e vacuum unless, in addition t o removing t h e surface moisture, t h e vacuum has some mechanical action of opening u p t h e ends of t h e exposed resin ducts a n d t h u s facilitates t h e penetration of t h e solvent, I t is desired t o test this point in future experiments. EFFECT O F R O S I K CONTENT-These tests on t h e effect of different variables were made on samples of quite different rosin content, one lot being comparatively rich and varying from 23 t o 30 per cent rosin, a n d another lot being comparatively low in rosin a n d varying from IO'/: t o 1 3 1 / 2 per cent. An analysis of t h e d a t a (Table 11) from runs made under t h e same extraction conditions b u t with chips of different rosin content is of interest. R u n s 3, 6 a n d 9, made a t 30 lbs. pressure a n d I j min. extraction, are shown graphically i n Fig. VI. I t is seen from t h e table t h a t a higher percentage of rosin is recovered from woods of greater rosin cont e n t a n d t h e higher recovery is evident throughout t h e progress of t h e extraction as shown in t h e figure. This is probably due t o t h e fact t h a t there is a larger proportion of t h e rosin which has saturated t h e cells surrounding t h e resin ducts proper in t h e richer n7ood a n d this rosin is, therefore, made more accessible t o t h e action of t h e solvent. The wood containing 13.j per cent rosin is about as low in rosin as could be extracted commercially. SOLVEKT LOSS
The apparatus used in t h e test was not found t o be entirely suitable for t h e s t u d y of t h e loss of solvent. Because of errors in construction t h e solvent collected in pockets in t h e piping a n d i t was, therefore, not recovered until another run. There were also noticeable leaks a t several points. I n general it was apparent t h a t extraction under pressure tended t o increase slightly t h e amount of solvent retained in t h e chips b u t there was no difficulty in recovering this solvent on subsequent steaming. With evident leaks in t h e apparatus, increasing either time or pressure Run NO
TABLE111-SOLVENT LOSSESIN VARIOUS R U N S CHIP PRESSURE TIME SOLVENT L o s s ROSINYIELD In.
Lbs. 0 0 30 30 55 30 30 ( a ) Varied from 3.16 t o 3.79.
Min. 15
45 15 45 15 15 45
Per cent 2.38 6.87 3,46(a) 4.30 3.74 3.46 3.85
Per cent 72.6 75.0 91.5 93.7 85.3
68.5 68.9
would, of course, increase t h e solvent loss. The amount lost in several of t h e runs is shown in Table 111. While t h e d a t a do not show clearly t h e effect of t h e different time and pressure conditions on SO!-
T H E J O U R N A L O F I S D C S T R I A L -IATDE . J - G I S E E R I S G C H E M I S T R Y
00
vent loss, it may be noted t h a t a longer time seemed t o give a greater increase in solvent loss t h a n a higher pressure. It was possible t o determine approximately the proportion of this loss t h a t occurred in t h e redistillation of t h e solvent and this averaged about I O per cent of t h e total. The solvent loss will be taken u p in detail in a later study. F O R X A T I O K O F .A P R E C I P I T A T E
An interesting point t h a t came u p in the experimeiits was t h e discovery of a precipitate in the solvent removed from , t h e chips. especially after extracting wood of high rosin content. Yaryan’ calls attention t o a black pitchy substance n-hich precipitates out of t h e rosin solution and which he says is due t o the action of fire on the stumps or lightwood. The precipitate was a t first dark brown, later becoming black; it mas quite sticky. and was first thought to be some constituent of t h e rosin insoluble in petroleum. Further examination indicated t h a t i t was largely basic ferric acetate which carried down a small amount of rosin with it. I t was no doubt formed by the attack of the iron retorts b y the free acetic acid occurring in the old wood. the acetate of iron formed becoming the insoluble basic salt a t the high temperature of t h e boiling solvent. In some of the runs the precipitate amounted t o as much as I per cent of the dry weight of the wood. SUITABILITY OB THE EXTRACTED CHIPS F O R P C L P
Only preliminary experiments have been made with t h e extracted chips. I t was desired first t o determine the quality of pulp t h a t could be obtained from t h e 3/16-in. chip although it seemed t h a t this size would give too short a fiber length for good pulp. By using t h e sulfate process the unscreened chips from Runs 6 and 9 were cooked in a semi-commercial digester. The time of cooking was I hr. in getting u p t h e pressure. and z hrs. a t T O O lbs. pressure. The cooking liquor contained I j . 7 lbs. S a O H and 7 . j lbs. Na2S per 1 0 0 lbs. of wood. The pulp yield was 4 3 . z per cent of the dry chips. Two beater treatments were made on t h e “half stuff,” the duration of beating being j hrs. in each case. I n one run t h e beater roll was hard down during t h e last hour, while in t h e second run the stock was much more dilute and the roll was set so as t o give a comparatively light brush, The pulp was run over the machine and t h e sheets from t h e two beater treatments gave t h e following strength tests. The figures from what may be considered a No. I Kraft are given ;n the following table for comparison. STREXGTHS C H O P P ETEST R FACTORBreaking Length PAPER Points per Ib. in Meter; 5425 Beater R u n No. I.. . . . . 0 . 7 2 4730 Beater R u n No. 2 . . . . . . 0 . 6 5 6000 No. 1 K r a f t , . . . . . . . . . . I . 0 0
FOLDIXG EIGHT TEST Times 800 347
PER
RElM Lbs. 40 38
1500
While R u n I was stronger, R u n z gave a sheet. Both were a very fair grade of No. z Further tests will be made by using the larger b u t since the small chip gives such promise of 1
U S P a t e n t 934 257
40
softer Kraft. chips being
Yo!. 8, S o .
8
suitable for pulp, they are more desirable, since it is posiible t o get so much higher yields of rosin from the ni by extract ion C O N k L C S I O S S AND
THEIR
COMIIERCIAT,
APPLIC.4TION
T l ’ e results of these experiments seem t o indicate t h a t a solution of t h e problem of obtaining another product in the extraction of resinous wood b y the solvent process may he found in using a larger chip, whose minimum size is 3 , i n . , and extracting under a maximum pressure of 30 lbs. by using four washes of ~j min. each. X closed t y p e of battery in which the vaporized solvent can be returned continuously t o the retort is advantageous for extracting under pressure. Extraction under pressure for a short time is shown t o give much higher yields of rosin t h a n no pressure for a longer time. As noted in the resulx given above, the yields by petroleum extraction are based on control analyses made by using chloroform as solvent. I t x-as observed t h a t certain constituents of the rosin are insoluble in petroleum but are soluble in chloroform. Since it is also shown t h a t increasing the time of estraction has no appreciable effect a t 3 0 lbs. pressure, and since 9 4 . 8 per cent were recovered under those conditions, it would seem possible t h a t practically all of the petroleum-soluble rosin mas extracted a t this pressure. I t is probable, therefore, t h a t a lower pressure would be as efficient as 3 0 lbs. Chips as small as in. are apparently suitable for paper pulp as they gave a good grade of No. z Kraft by the sulfate process. Chips of this size could probably be most advantageously cooked commercially in a rotary type of digester. A plant extracting wood yielding about z j o lbs. or 1 . 0 9 bbls. of “F” grade rosin per ton (89 per cent yield of 1 4 . 0 per cent rosin), which is about t h e minimum for practicable commercial operation, would produce extracted chips suitable for making about, 7 j o lbs. of pulp per ton of wood. A .jo-ton extraction plant would then supply a no-ton pulp mill, or since an extraction plant might require about three-quarters of its extracted chips as fuel in case it were not advantageous t o buy other fuel, a zoo-ton plant would have chips for fuel and still could supply a commercial pulp mill of practicable size. I t is difficult t o give cost figures t o cover the variezy of contingencies met with commercially, b u t the following estimates of average practice show clearly the effect on the net returns of obtaining extracted chips as an additional valuable by-product. COST E S T I M A T PE% R TONOK 200-Tox E X T R A C T I OPNL A S T Prices for past 15 yrs. Returns a t Average Cost of Operation 4 gals. turpentine a n d pine \ToOD. . . . . . . . . . . . . . . $ 2.25 0.90 oil a t 40 c . . . . . . . . . . . . . . . S 2 . 4 0 SOLVEIT. 7 ) 9 gals. a t 12 c 250 lbs. rosin a t 1.5 c . F U E L : 3 i t o n extracted 0 . 0 0 (3.77112 per net bbl. chips a t no c o s t . . . . . . of 230 Ibs.) .. 3 .75 C O O P E R A G.E. .. . . . . . . . . . . . . 0 . 6 5 0 . 8 7 Superintendence and Labor $6 1.5 Selling a n d shippiqa, includ0.72 Cost of operation . . . . 5.92 ing f r e i g h t . . . . . . . . . . . Taxes, insurance a n d depre0.35 hTet profit.. . . . . . . . . . . . . SO 23 ciation over 15 years.. . . 0.18 Selling price 250 Ihs. exRepairs a n d miscellaneous. __ tracted chips a t 51.00 per 55 92 t o n . , . . . . . . . . . . . . 0 25 ~
N e t profit with chips as byproduct.. . . . . . . . . . . . . . . . $ 0 . 4 8
Aug., 1916
*THE JOC'R-li.4L O F I Y D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
701
ing effect of t h e soaps o n t h e fibers by making tensile strength determinations. S U R F A C E TExsIox-In most of t h e theories which have been brought forth t o explain t h e detergent value of soap, surface tension has played a n important part. I n order t o study the relation between surface FOREST P R O D U C T S L.4BORATORY .MADISOX, WISCONSIN tension and concentration, a number of experiments were made b y means of t h e Traube stalagmometer. SOME STUDlES OF SOAP SOLUTIONS Tt7hile the Traube stalagmometer method for surface By VICTOR LENHER A X D MARYV R BUELL tension determinations possesses certain objections, Received April 3, 1916 these errors are of minor rather t h a n major character. The chemical analysis of a soap shows only t h e conIt was found t o suffice in this work. inasmuch as the stituents of which it is composed. T h e results indiresults are comparative. cate t h e content of water, f a t t y acid as soap, unil bulb was blown in t h e stalagmometer so t h a t j saponifiable matter, alkali (combined or free), glyccc. would be t h e quantity delivered, and a device used erin, salt, filler, etc. S o satisfactory method has whereby t h e pressure could b e regulated. T h e whole been proposed for the determination of t h e real value was surrounded b y a water b a t h and t h e outlet' alof a soap, namely, its cleansing power. From t h e lowed t h e drops t o form in t h e air or in a given liquid. timk of Chevreul, one of the first t o s t u d y soap, t o I n t h e measurements made b y this method, t h e numt h e present d a y , considerable literature has accumulaber of drops were counted and t h e time taken when ted on t h e cleansing power of soap. Some of t h e work a definite volume of liquid was allowed t o flow out is experimental, and some is purely speculative, b u t through t h e pipette. with all t h e thought and energy which has been exSodium oleate solutions were prepared from pure pended on this subject i t must be confessed t h a t sodium hydroxide and very pure oleic acid. When we do not possess sufficient d a t a t o explain satisfacsoap solutions are made t o form drops under the surtorily t h e phenomena ordinarily exhibited b y soap face of a n oil or of a liquid immiscible with water, solutions, nor can t h e chemist tell t h e laundry how t h e nufnber of drops formed is much greater t h a n when much soap is required t o remove a definite amount of a n equal volume of water is made t o form drops under dirt or wash a given weight of soiled clothing. similar conditions, t h a t is, t h e surface tension beVarious phases of t h e question as t o how soap tween oil and water is much greater t h a n the surface acts as a detergent have been studied a t different tension between oil and soap solution, or, the surface times. These studies are well summarized b y Bancroft tension is inversely proportional t o t h e number of in his papers on ernulslfication, now running in t h e drops formed. The relation between concentration Journal oj' Physical Chemistry. of soap solutions and their surface tensions toward T h e various methods which have been suggested some liquids immiscible with water is shown in t h e from time t o time for t h e evaluation of soaps, have accompanying curves. I n all cases t h e temperature depended largely on t h e use for which t h e soap is inwas controlled a t 2 j '. tended. Hillyer' divides soaps into two classes: T h e first point on each of t h e curves is not as accurate those used with cold or lukewarm water, such as as t h e others because a t t h e N/IO concentration toilet soaps; and those used with boiling water, as hydrolysis is fairly rapid. The significance of the laundry soaps. His method for determining t h e de- points is t h a t they show the general direction of t h e tergent value of soap is by t h e Traube stalagmometer curves. The error of t h e observations is considered method for determining t h e surface tension of a soap t o be approximately 0 . j per cent. Theoretically, solution against a kerosene which he arbitrarily t h e point of minimum surface tension should be a t adopted as a standard. The number of drops formed t h e point a t which t h e maximum number of drops is in a given length of time is regarded as a measure formed. I n all of t h e cases investigated, with the of t h e amount of soap in solution, t h e emulsifying single exception of t h e experiment with air, t h e surpower of t h e soap, and its cleansing power. The numface tension was lower with the concentrated solutions ber of drops is referred t o a curve obtained b y running t h a n with t h e dilute solutions, and t h e general direcstandard solutions of neutral sodium palmitate through tion of t h e curves is t h e same. standard kerosene and t h e relative efficiency of t h e I t has been observed t h a t t h e surface tensions soap is t h u s approximated. I n testing soaps intended of sodium oleate solutions toward air are increased for use with hot water, t h e whole of t h e apparatus is surrounded b y a water b a t h which is kept a t t h e de- with t h e dilution. The actual surface tensions of various concentrations of sodium oleate solution sired temperature. toward air were found b y t h e Traube stalagmometer Luksch2 attempted t o determine t h e efficiency of a soap b y coloring pieces of chiffon of different method t o be a t z j" as follows, expressed in dynes sizes and washing t h e m under t h e same conditions per centimeter: h7/S0 X/10 N/20 N/40 N/160 N / 3 2 0 N / 6 4 0 N/1280 in a washing machine. T h e results varied I O per cent, 2 8 20 26 21 25 33 24 17 24 77 25.55 41 2 8 24 91 b u t were sufficiently accurate t o show t h e difference By t h e same method water showed 7 1 . 7 8 toward between different soaps, H e also studied t h e weakenair. It is interesting t o note t h a t with N I I O t o W 3 2 0 1 J A m Chem. S a c , 25, 1256 sodium oleate there is such a small variation in t h e 2 Sezfensiedeu-Ztg , 40, 413, 444.
T h e plant would pay j . j per cent on a n investment of Szjo.ooo without t h e chips and 1 1 . j per cent assuming the chips t o be worth $ 1 . 0 0per t o n for pulp, which is a low estimate since the material would be in condition for immediate pulping.
