682
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
would be a valuable aid t o anybody having occasion t o make use of a reference library, and the aboveproposed small portable machines carried by investigators and translators may very well be used as “feeders” for the large machine in the home plant. The cost of the bromide paper is about $ 1 . 7 j per I O O f t . , and a Ioo-ft. roll of paper measures only 4 . 3 7 5 in. wide by 4 in. diameter and has a capacity of about 300 exposures. The entire apparatus weighs but a few pounds and does not occupy more than the table space allotted t o any one reader or the space occupied by a large dictionary or several volumes of some periodical, and no reasonable objection t o its use can be interposed by any librarian, the argument, if any, being on the side of the reader, inasmuch as the boog t o be copied may be released for issue t o another reader in an incredibly short time after “pushing the button.”
1701.
12,
NO. 7
wood distillation, experience showed t h a t i t was not suitable for kelp. However, an interesting collection of data was obtained which is summarized in t h e paragraphs which follow. Reference t o the specimen log of a distillation run which is here reproduced, as well as a glance a t t h e composite time-distillate curve, will show how the high moisture content of the dried kelp prevents a rapid rise of temperature when the kelp starts t o distil. This gradual expulsion of water vapor with its accompanying organic matter undoubtedly tells a story of the volatile kelp constituents t h a t the more rapid heating in a much hotter retort would fail t o do. The retort was preheated b y lighting the gas flames of the retort the evening before the run was t o be made.
CONCLUSION
There is apparently a need for a portable and cheaply operated photographic device for copying illustrations and articles on file in reference librariesfor the purpose of compiling the technical data needed in a n investigation. The experiments described indicate t h a t the use and manufacture of such a device are both within the range of commercial possibility. It is believed t h a t a device combining the operating principles of the existing bromide paper copying machines and the self-illuminated meter-reading cameras would prove t o be a valuable aid in data compilation, and simple enough in operation for use by nontechnical clerical assistants. There appears t o be no reason why i t should not be possible t o simply “push the button-and read the book a t home.” POTASH FROM KELP. 11-THE EXPERIMENTAL DISTILLATION OF KELP AT L O W TEMPERATURES1 By G. C. Spencer U. S. KELP POTASHPLANT,SUMMERLAND, CALIFORNIA Received March 9, 1920
A study of the experimental, destructive distillation of dried kelp was undertaken t o determine whether or not under carefully controlled conditions any relationship could be established between the temperature a t which distillation was taking place and the nature of distillation products. The work was done in the Forest Products Laboratory of the U. S. Department of Agriculture, Madison, Wis., in order t h a t the apparatus and technique developed there in the destructive distillation of wood might be available for the research in hand.2 Kelp was distilled in an oil-jacketed retort which was built for experimental wood distillation, which has been fully described and illustrated by L. F. Hawley and R. C. Palmer.3 While this retort was adapted for 1 The first paper of this series entitled “The Experimental Plant of the U . S. Department of Agriculture,” b y J. W. Turrentine and Paul S. Shoaff, appeared in THISJOURNAL, 11 (1919). 864. *Acknowledgments are due to Director Winslow, t o Drs. Hawley, Mahood, and others at the Forest Products Laboratory for assistance and courtesies extended, and t o Prof. 0.L. Kowalke of the University of Wisconsin for the use of laboratory space and apparatus for supplementary
work. 8 “Yields from the Destructive Distillation of Certain Hardwoods,” U. S. Dept. of Agr., Bulletin 129.
COMPOSITE TIME-TEMPERATURE CURVE OB KELP DISTILLATION IN JACKETED RETORT REPRESENTINQ RUNS2, 3, S , 6 , AND 7
OIL-
The kelp was charged into the retort in a cylindrical iron cage 3 f t . long and I f t . in diameter, inside dimensions. This cage was lined with heavy wire netting preparatory t o distilling the dried kelp, and two partitions of the same material were set lengthwise in the middle of the cylinder t o provide a n air space for the escape of vapors from the middle of the kelp charge. Sixteen distillations of kelp (average weight of charge 30.2 lbs.) were made in this manner. The first runnings of distillate were always clear and of a bright green color. This condition continued with only a slight increase in density until a temperature, usually above 15oO C., was reached, when a turbidity became noticeable in the liquid, which also changed from green t o amber. This turbidity indicated a change
July, 1920
T H E J O U R N A L OF I N 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
i n the nature of the distillate and the first distillation c u t was accordingly made a t this point. As the distillation progressed the turbidity increased until a light brown flocculent precipitate separated, which gradually settled out. Experience showed t h a t the next cut should logically be made a t the temperature where the t a r commenced t o come over, but for convenience two and sometimes three fractions were taken before this point was reached. The density of the liquids increased from approximately 1.01 to 1.065, and the amounts of dissolved substances also increased as long as the aqueous distillate continued t o flow. I t can be seen t h a t the liquor driven off up t o the point indicated as turbidity is mostly water. The amount of dissolved material i n this fraction is necessarily low, and in all probability this turbidity point represents the first stage of the cellular decomposition. There was a t no time any evidence of a n exothermic reaction. Reference t o the time-distillate curve will show t h a t , from the point where the first turbidity appears t o t h a t where the t a r begins t o flow, the distillation rate is pictured by a nearly straight line. Above the “tar point” the curve begins t o bend and the volume of distillate decreases. The nearly straight line may indicate the passing over of somesubstance of nearly cons t a n t composition, and this belief is substantiated by t h e isolation of the glycerol-like liquid which will be described in another paper.’ The tarry substances were emulsified with a n approximately equal quantity of the aqueous distillate and consequently always floated on the watery layer. A sharp separation was impossible, however, since the t a r showed a strong tendency t o adhere t o the glass of the cylinder or of the separatory funnel and t o conceal the actual amounts of water and tar. When kelp is distilled a t high temperatures the liberated gas is always combustible. This gas has never been analyzed, but its calorific power has been determined and found t o be sufficient for use as a fuel.* Such gas, if properly applied, would go far toward reducing fuel costs in a k e l p plant. Samples of gas from the low temperature distillations were analyzed and tested but in no case were t h e evolved gases inflammable. The following analyses of gas fractions show t h a t the composition of the gases evolved a t different temperatures is nearly the same:
co*.. . . . ...... eo.. . . . .
02,
ANALYSESOF GAS FRACTIONS 131 O-13So 163”-167O 226’-229’ Per cent Per cent Per cent 80.5 85.5 85.0 0.0 0.0 0.0 11.3 10.3 11.4
271 ‘-275‘ Per cent 82.8 0.6 10.2
The residual gases were in each case mixed with an excess of air in a n explosion pipette but in no case was there a contraction of volume. The last distillation of kelp t h a t was made in t h e oil-jacketed retort was modified by mixing 24.1 lbs. of kelp with j lbs. of quicklime and carrying out t h e “The Preliminary Examination of Kelp Distillates.” J. W. Turrentine, “Note on the Distillation of Kelp,” Intern. Congt. A p p l . C h e m . , 15, 313. 1 2
Proc. 81h
683
distillation like those preceding. The aqueous distillate differed from those of the former runs by being alkaline, although a t no stage was there any odor of ammonia. Two gas fractions were taken a t 158’ t o 1 7 3 ’ and 2 5 5 ’ t o 2 6 0 ° , respectively. They differed in composition from those described above in containing less carbon dioxide, which was kept back by the lime, and more carbon monoxide, which would naturally be higher in percentage under such circumstances. N o advantage was apparent from mixing lime with the kelplcharge. IGNITION OF CHAR I j I N A CLOSED R E T O R T
Inasmuch as none of the charcoal produced in t h e oil-jacketed retort had been heated sufficiently t o remove all of its volatile matter, a portion of the charcoal from Run ~j was heated in an iron retort t o as high a temperature as could be attained by a flat burner and a Meker burner together. The retort was set in a holder t h a t prevented air currents from interfering with the flames, but even with this advantage the retort did not appear t o be heated t o redness. Three and three-tenths pounds (1.5 kg.) of No. I j char were heated for an hour and a quarter. The retort was not entirely tight and a little of the gas was lost by leakage. The first drop of distillate appeared when the off-take temperature was 98’ C. A t the same time white vapors began t o come over through the condenser. After 40 min. the temperature of the distillate had risen t o I O I O C. At this temperature the aqueous distillate was brown in color and a darkcolored oil floated thereon. A flocculent precipitate appeared in the watery distillate. When the char had been heated an hour the white vapors stopped coming over, and the temperature rose t o 10gO C. After this the off-take temperature dropped t o 80’ C. and no more distillate came. The watery distillate contained ammonium salts. Weight of char after igniting.. . . . . . . . . . . . . 3 . 0 1 lbs. ( I . 36 kg ) Total weight of distillate.. ............... 5 4 . 2 g. ( 3 . 6 per cent) Weight of t a r . . 1 1 . 5 g. 4 2 . 7 g. Weight of water..
......................... .......................
This experiment shows t h a t the charcoal produced in the oil-jacketed retort still contains about g per cent of volatile matter, which renders it unfit for many purposes. For instance, its aqueous extract is brown in color when i t should be water-white, and i t is furthermore not sufficiently ignited t o be a good filtering medium or absorbent. The residual charcoal from this ignition, on the other hand, is jet-black and its water extract is free from any color whatsoever. I n June 1918 about I O lbs. of unleached kelp char from Run 6 were forwarded t o Dr. F. W. Zerban, of the Louisiana State Sugar Experiment Station a t New Orleans, La. Dr. Zerban reignited this char in a closed iron container and leached the residue with water and acid, then made tests on the resulting charcoal t o determine its value as a decolorizing agent for sugar solution.’ 1
F . W. Zerban and E. C. Freeland, THISJOURNAL, 10 (1918), 812.
T H E J O U R N A L OF I N 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
684
The kelp char made in the oil-jacketed retort did not prove as satisfactory as those originally prepared a t higher temperatures. I n the specimen distillation log t h a t follows, t h e column named “middle temperature,” indicates t h e temperature a t t h e center of the kelp charge, while “maximum temperature” refers t o t h e oil bath surrounding the retort. DISTILLATIONO F KELP Log of Run 7, May 17, 1918 CONDITIONS:Retort Dreviouslv heated to 220’ C. Stronelv heated a t first Middle Max. Total Time Temp. Temp. Distillate c. cc. REMARKS A.IM. c. 8:20 140 182 , Charged retort 175 Distillation commences but 8:35 104 soon stops 102 Minimum temperature 8:45 187 114 9:oo 211 2 15 118 Distillation recommences 9.02 ~~. 134 23 1 9:15 36.5 148 9.30 97 Clear, green 244 158 9:45 177.5 260 170 190.5 273 Becoming turbid. Fraction 1o:oo 104°-1700, 497 g. Flaky precipitate 285 191 10:15 180 184.5 10:30 191 296 183 10:45 201 305 213 319 188 1 1 :oo Fraction 170°-2130, 745 g. 225 333 185 11:15 340 173 23 1 11 :30 345 166 Reduced flame’ 11 :45 247 Tar coming over. Fraction 350 144 12:oo 256 213’-256’, 668 g.
-_
.. ...
... ...
P.M.
2:15 2:30 2:45
267 273 281 289 295 300 304 308 310 311 313
352 353 354 354 355 355 352 350 346 345 350
162 ’ 119 136 115 109 87 73 59 48 43 43.5
3:oo 3:30
317 320
352
34
12:15 12:30 12:45 1 :oo 1:15 1 :30 1:45 2:oo
...
Tar, 19 g. Water fraction 530 g. Tar, 50 g.
256O-295‘,
Tar, 55 g. T a r , 29 g. Shut off gas. Water fraction, including drip next morning, 373 g.
...
Tar, 71 g. Total weight of tar, 224. g. (1.4 per cent) 1 There are two kinds of tar oil: the first t h a t comes over is dark brown with a penetrating though faint odor resembling a n essential oil or certain ketones; the second is blacker and has a more unpleasant odor.
............... .. ................................ ............. ........... ..................... ........ ..................... ANALYSES OF WATER CUTS Fractios Degrees 104-170 170-213 2 13-256 256-295 295-320
Specific Gravity 1 .007 1.013 1.032 1 .os0 1.063
27.5 lbs. 107.6 lbs. 90.0 lbs 17.6 lbs. 9 . 9 lbs. 12,500 g. 3,042 g.
....
(24.3%) (11.7%)
LOG 7 Solids in 10 Cc. Grams 0.1699 0.2687 0.9159 1.5961 2.4833
SUMMARY
Sixteen distillations of dried kelp were made in a n oil-jacketed wood retort at temperatures not exceeding 320’ C. These yielded aqueous liquor, t a r , and a noninflammable gas. The residual charcoal was insufficiently heated either for a good extraction of potash or for use as a filtering medium. This work has demonstrated the necessity for distilling kelp a t a much higher temperature.
No. 7
By L. F. Hawley and H. N. Calderwood, Jr. FOREST PRODUCTS LABORATORY, U. S . FOREST SERVICE, MADISON, WISCONSIN Received February 21, 1920
Sometime ago t h e authors carried on efficiency studies a t several wood-distillation plants with t h e purpose of preparing a standard set of directions for the use of t h e refinery foremen and stillmen. The results of t h e work on t h e operation of the t a r still were of special interest. Since these results are directly applicable t o the tar-still operations of many other wood-distillation plants, i t was decided t o publish them. The operation carried out in the tar still is for t h e purpose of recovering the acetic acid t h a t remains in the settled t a r after the pyroligneous acid has been removed. I n general, the method consists of heating t h e tar by means of steam in closed coils until t h e water is driven off, and then, while keeping t h e closed coils still in use, blowing live steam through t h e charge.* It is obvious t h a t the most desirable conditions for running a tar still are those under which the most acetic acid may be produced in t h e shortest time a n d with the greatest degree of concentration. The best conditions for this distillation with respect t o speed, length of time, and pressure of steam in the closed. coils, have never been determined, and the commercial practice varies greatly. E F F E C T OF S P E E D OF DISTILLATION
Two test runs were made with a charge of j I 0 gal. of t a r in a depth of 40 in. The conditions were t h e same in both runs, except t h a t the speed a t which t h e live steam was blown through the tar was different. The results are shown in Tables I and 11. The tables TABLE I-SLOW
(64%) (36%)
12,
TAR-STILL OPERATION IN HARDWOOD DISTILLATION PLANTS
RESULTSO F R U N ? Weight of kelp distilled.. Weight of basket and kelp after heating. %re. Residual kelp (non-volatile) Loss by heating (total volatile) Weight of charge.. Total weight of liquid distillate.. Gaseous distillate..
Vot.
Time Start 12 : 50 1. . ., . ns
2 3 4 5 6 7 8 8 9 9 10 10
: 05
: 05 : 05 : 05 : 05 : 05 : 05 : 35 : 05 : 35 : 05 : 35
Total Speed Distillate Gal. per Hr. Gallons 40 10 .. 30 40 65 25 89 24 112 23 26 138 24 162 185 23 196 22 207 22 219 24 225 12 23 1 12 ~~
SPEED
In Frac-
tion Total Pressure Pounds Pounds in Coils 17.1 17.1 45 4.3 48.1 65.2 .. 19.35 27.6 92.8 46 13.31 112.0 41 9.68 19.2 124.0 43 6.25 12.0 134.0 43 4.62 10.0 35 3.00 139.9 5.9 42 144.0 2.12 4.1 40 145.8 2.08 1.8 40 1.87 147.4 1.6 41 149.0 1 . 6 . 1.69 45 1.61 149.8 0.8 45 1.52 150.6 0.8 Residual tar 0.28 per cent acid
Acid Per cent 20.6
show t h a t t h e speed has a slight effect on the concentration, t h a t is, t h a t a certain number of gallons of water in the form of steam going through t h e charge of t a r will remove more acetic acid when t h e steam 1 There is no mysterious effect of “steam distil1ation”jn this separation of acetic acid from tar. The steam is superheated all the time i t is in contact with the tar and acts like any neutral gas in its effect on the distillation. In fact, as far as the distillation is concerned, the same fractionation of acid and oil would be obtained by direct fire heat in a distillation without steam. The separation of acid from oil actually takes place after t h e condensation of the vapors when the acid is divided between the water and oil according t o its relative solubility in these two substances. This indicates the desirability of washing certain fractions of the oil with water to recover a further quantity of acetic acid.
