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stability in solutions of concentrated acids and bases, near maximum wetting in one per cent solutions, and ease of manufacture. Acknowledgment
The authors wish t o thank the Reilly Tar and Chemical Corporation for the generous supply of material for this investigation. Literature Cited (I) Dz;iewo&ki, K., Schoenw6na, J., and Waldmann, E., Ber., 58B, 1211-18 (1925). (2) DziewoAski, K., and Wulffsohn, A., Ann. chim., [l] 9, 78 (1929). (3) Euwes, P. C., Rec. trau. chim., 28,395 (1909).
(4) Groggins, P. H., “Unit Processes in Organic Synthesis”, pp. 319,626, New York, McGram-Hill Book Co., 1938. ( 5 ) Mair, B. J., and Streiff, A. J., J . Research A-atl. Bur. Standards,
34, 395 (1940). ’ (6) Shriner, R., and Fuson, R., “Systematic Identification of Organic Compounds”, .. PD. 159-161, New York, John Wiley & Sons. 1940. (7) Vesely, V., and Kapp, J., Chem. Listv, 18,201-5, 244-9 (1925). ( 8 ) Vesely, V., and Pac, J., Collection Czeehoslou. Chem. Commun., 2, 471-85 (1930). (9) Vesely, V., and Strusa, F., Ibid., 6, 137-44 (1934). (10) Weiss, J. M., and Downs, C. R., IND. ENG.CHEX., 15, 1022-3 (1923). (11) Weizmann, C., and Bentley, W. H., J . Chem. Soc., 91, 99 (1907). (12) Wendt, G., J . prakt. Chem., [ 2 ]46,317 (1892). BASEDupon a thesis submitted b y John H. Lux t o t h e faculty of Purdue University in partial lulFlllment of the requirements for t h e degree of doctor of philosophy.
CTIVE DISTILLATI Donald
Vol. 35, No. 3
OF
F. O t h m e r and G e o r g e A. Fernstrom
POLYTECHNIC INSTITUTE, BROOKLYN, N. Y.
I
N THE manufacture of sugar from cane, one residual product is the fiber bagasse, sometimes known in the
British colonies as “megasse”. The origin of the name “bagasse” [Tas traced back to Provence, France, where it \vas applied to refuse from olive oil mills-hence, anything worthless. One investigator ( 2 ) reports that the Louisiana varieties of sugar cane yield 400 to 580 pounds of wet bagasse per ton of cane, or an average of 20 to 30 per cent of the total amount of cane ground. In the case of a sugar central producing 1000 tons of sugar per day, about 480,000 pounds of wet bagasse would be produced. Bagasse is a stratv-colored, bulky fibrous substance. It consists of 25 to 40 per cent fiber cellulose, 0.1 to 0.15 per cent unknowns (albuminoids, gums, etc.), 6 to 10 per cent sugar, and 40 to 55 per cent water. Its ultimate analysis ( 3 ) on the dry basis is: carbon, 43 to 47 per cent; hydrogen, 5.4 to 6.6; oxygen, 45 to 49; ash, 1.5 to 3 per cent. The heating value of dry bagasse is 8300 B. t. u. per pound (a). For bagasse containing 42.8 per cent moisture, the heat value was found to be 4800 B. t. u. per pound and for that containing 56.7 per cent moisture, it was 3620 B. t. u. per pound. The net heating values are 2200 to 3350 B. t. u. per pound. Thus, 1 pound of wet bagasse will evaporate 2 to 3.5 pounds of water from and a t 212” F. Assuming coal 1 Present address E. I. du Pone de Nemours & Company, Inc., Wdmington, Del.
Bagasse and Products (India Ink Bottle for Size Comparison) Lower left, raw bagasse; lower right, charcoalr above left, fractured briquet using starch binder; above right, briquet using molasses binder.
to have 14,000 B. t. u. per pound, 4 to 6 pounds of bagasse are equivalent to a pound of coal. The bagasse from a sugar central producing 1000 tons of sugar in 24 hours will generate from 1160 t o 1440 boiler horsepower during that time. About 60 tons of coal per day would be needed to do the same work. Bagasse is also processed by cooking and then fashioned into sheets of building or insulating board, approximately inch thick and 4 feet wide, which are cut into lengths of 8 x 12 feet. This material bears the trade name “Celo-
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attained if the bottom had been closed so that only enou h air for combustion cod$ enter the furnace. b b Bagasse is the wood stem of the sugar TEMPERATURE MEASUREcane after expressing the juice. Unlike the stalks MENT. The retort temperature was measured by a of most other types of plants which are also waste Bristol thermocouple in the cellulosic material, it is readily available in large well in the top of the can and an indicating pyromequantities at single points, the sugar centrals. ter. They were calibrated, Furthermore, most of the countries in the tropics and temperatures could be read to 5" F. where bagasse is produced use charcoal in large RECEIVERS.Three bottles quantities as a domestic fuel. were placed in series as Experiments were undertaken to determine receivers. The first bottle was a side-arm flask caliyields of several products when bagasse is carbrated for rough measurement of volume by a scale bonized in a retort under different conditions of pasted on the side and attemperature and time. Per short ton of dry batached to the bottom of gasse, approximately 1050 pounds of charcoal, the condenser by a rubber stopper. The noncondens11/, gallons of crude methanol, and 53 pounds able gas passed through the flask and left by means of of acetic acid were obtained. The amount of the side arms. charcoal was considerably greater than would be To remove all tar before produced from an equivalent weight of dry wood; allowing the gas to ass t o the meter, a seconf small while the volatile constituents were in each case collecting bottle was used considerably lower. with a short inlet tube and an outlet tube which The charcoal was formed into experimental extended into the center of Carbonization Apparatus briquets by the addition of a small amount of the bottle. During several of the tests it became coated RETORT.The heatstarch or molasses before compression and drying. with tar, indicating the need ing chamber or retort (FigIt appears that the carbonization o f bagasse could for such a trap. ure 1) consisted of a heavv Finally, the gas bubbled iron can with an airtight be profitable in those locations where it is available through about 100 cc. of cover. One-gallon whitein quantity. water in an %ounce bottle lead paint cans were used, and then passed to the gas since they are made of commeter. The solution in the paratively heavy sheet and third receiver became slightly have no soldered seams. acid during the run. T h e c o v e r s of t h e s e IMPORTANCE OF CLEANING. cans have rolled lips, which The tar driven off had a tendwere made a i r t i g h t ency to clog the pipe lines. The condenser and connections were by packing the overlapping cover with a plumber's packing compound. A layer of asbestos cement was laid outside of cleaned by forcing a metal bar through the pipe to break u any solid itch clinging to it, Pieces of cotton waste, either d?y or this. Two holes were drilled through the cover. One, with */4-inch soakes in methanol, were pushed through the pipe to clean off iron pipe bushing, served as an outlet for the distillation products; fluid tar, which is done more readily immediately after a run, the other, with a 1/2-inch iron pipe bushing, held a thermocouple since the tars harden to pitch after several days. well. The junction between the bushings and the can cover was made Plan of Distillation airtight by placing large metal washers on each side of the cover. A layer of l/s-inch asbestos paper was placed between the metal PROCEDURE. A weighted amount of bagasse was added, washers and the cover. A metal nut was used to press the the retort was sealed, and the outer shell was placed around washers and two asbestos strips against the cover. All joints were then given a coating of plumber's a l e r and finally a layer of the retort. The condenser, collecting bottles, thermocouple, asbestos. and MBker burner were arranged. The burner was lit; A a/,-inch iron pipe was inserted inside the larger bushing. and the retort temperature, volume of distillate, and disThis pipe line was attached to the condenser by a union, two change temperatures were recorded at definite time intervals. elbows, and three short pieces of pipe. In later experiments the volume and composition of the The thermocouple well was made by placing a '/Z-inch capped pipe inside of the smaller bushing and rojecting into the retort. gas were also determined periodically. The retort rested on several sheets ofmetal, to protect it from Three products are obtained: charcoal, condensablethe direct flame. The assembly was supported by a large laboraliquids, and noncondensable gases. The charcoal remained tory tripod. in the retort and was removed and weighed after cooling; CONDENSER.The Liebig type condenser (Figure 1) consisted of 27.5 inches of copper tubing of a/,-inch iron pipe size, jacketed the condensable distillate was collected mainly in the first by a 11/2-inch-diameter copper tube and having an inlet and an receiver; and the noncondensable gas was measured, anaoutlet for cooling water. lyzed, and vented to a n exhaust FURNACE SETTING. An outer shell was made from a 5-gallon duct. iron can container by removing the bottom. Two holes were The liquid product was later disdrilled in the top of this container to correspond to the condenser and thermocouple outlets from the retort. A larger hole protilled away from the accompanying vided for the escape of the products of combustion. The outside tar, and the volatile product was and top were covered with a 1/2-inchmesh screenin ; it served as weighed. The distillation was a foundation for an asbestos paste which was forced in and usually continued until the tar around the screening to a thickness of I .5-1.75 inches. A cotton net was placed on the outside of this asbestos layer. showed signs of decomposition. Three metal legs were fastened by bolts to the shell to support The tar residue solidified upon it in position over and around the retort. cooling. The distillate was tiTemperatures up to 1000° F. were attained in the retort by a trated for total acidity with large MBker burner. Greater heat economy would have been
tex". However, this process consumes only a small fraction of the total bagasse available. Paper pulp has also been made with low alphacellulose content. I n some regions-for example, Puerto Ricobagasse is returned to the soil as a very poor fertilizer. Experiments t o develop bagasse as ensilage, as a food itself, or as a carrier for molasses have been unsuccessful. The tremendous amounts of bagasse available at single points and the fact that charcoal is a n important domestic fuel in most tropical countries made desirable the investigation of the carbonization of this waste plant fiber.
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Vol. 35, No. 3
for run 6 to be 9.3 per cent. The standard method of difference was used after all combustible matter has been burned off. The ash content of the original bagasse was 3.9 on a dry basis.
Figure 7,
Experimental Carbonizations The rate of heating, time of heating, and maximum temperature were investigated. Table I and Figure 2 show the data obtained. RUN 1. After the bagasse had been heated rapidly for 25 minutes, the rate of heating was reduced slightly. The run continued for a total of 225 minutes and to a final maximum temperature of 840" F. These conditions were not satisfactory; the yields of acetic acid and tar mere well below those obtained under other conditions The yield of charcoal was also low. RUN 2 . Rapid heating for a short time resulted in a distillate which was high in tar and contained an average yield of acetic acid. Although this test was comparatively short, the rate of heating was great enough to make possible a maximum temperature of 755' F. in the retort. The conditions-rapid heating, short time, and, mainly, high maximum temperature-gave a minimum yield of charcoal, approximately 25 per cent belom the best condition (run 8). Rux 3 was not completed and was disregarded. RUN 4. Heat was applied at the same rate as run 2. This was the shortest test made (80 minutes) with the result that the maximum temperature attained \\as much lower than in run 2, The charcoal yield for this test was approximately 16 per cent greater than for run 2. The yield of total distillate was virtually the same for the two tests, but there was a slight decrease (about 9 per cent) in the acetic acid content of the distillate. RUN 5 . The charge was slowly heated to 350" F. Approximately 35 minutes were required to raise the temperature 100", while in run 2, whose temperature-time curve had the greatest slope, only 7 minutes mere needed to effect a similar temperature rise. Above 350' F. the temperature rise was
General Arrangement of Apparatus
sodium hydroxide, using phenolphthalein as both inside and outside indicator. I n later experiments a Beckman p H meter was used to determine the end point. These titrations were not absolute since all acids present were assumed to be acetic acid. Slight errors would also be introduced by the presence of phenols and aldehyde. After the solution was made strongly alkaline, i t was again distilled until all of the methanol present was evaporated, as indicated by a boiling temperature equal to that of water. This distillate was then weighed; and the specific gravities were determined to obtain the percentage of alcohol by volume from the tables. GAS AXALYSESwere made a t 15-minute intervals during the carbonization to study the composition of the gas during the different stages of carbonization. An Orsat apparatus was used to determine carbon dioxide, oxygen, and carbon monoxide. MOISTURNAND ASH. The stock of bagasse to be used was thoroughly air-dried, and the moisture remaining was determined to be 6.5 per cent. The ash content of the finished charcoal was determined
Table I. 1
Run number
Experimental Data 4
5
8
6
326.7 305.5
271.1 253.5
269.5 252.0
281.9 263.6
275 7 257.8
276.4 258.4
92.4 40.66
117.5 38.56
113.5 44.77
100.4 39.84
111.7 42,37
120.88 46.89
135.11 52.29
26.8 29.3 12.90
63.7 71.10 23.27
54.8 58.1 22.92
41 .O 45.8 18.17
76.5 81.3 30.84
55.4 64.55 25.04
67.2 72.51 28.06
121.3 53.39
137.8 45.11
99.5 39.25
123.3 48.93
88.9 33.73
90.27 3S.02
68.78 26.62
20.0 8.80
47.4 15.52
45.9 18.11
33.8 13.41
01.87 23.46
50.40 19.55
EO. 25 23.32
9.3 4.09
23.7 7.76
12.2 4.81
12.0 4.76
19.43 7.37
14 15 5.49
12.26 4.74
0,344 2.665 3.91
2.29 9.72 14.69
2,095 9.13 11.55
1.49 8.26 11.10
2.44 7 90 10.39
... ...
...
243.0 227.2
U ct
Total dyst. basis Dist. minus tar basis Total vol. gas produced, cu. it. M a x . temp. attained, p F. Total heating time. min.
2
840 ' 225
755 115
...
630 80
0.3663 2.01 2.73
...
800 230
...
785 260
1.735 6.92 S.8i
2.64 9 43 11.35
0.616 2.455 3.15 0.52 750 110
0,422
1,503 1.81 0,205 618 120
9 270.9 253,3
...
...
... ... I . .
0.34 571 130
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the final temperature was only 618" F., a high yield of charcoal was obtained. This yield was approximately 10 per cent greater than in run 7 and about 35 per cent greater than run 2, which had the poorest yield. The highest yields of acetio acid and tar were also obtained. The yield of methanol was, however, below that of run 7. I n Figure 3 the total volume of noncondeneable exhaust gases and the volume of carbon dioxide and carbon monoxide are plotted against time during runs 7, 8, and 9. The maximum percentages of carbon monoxide obtained were 8.1, 4.5, and 5.3, respectively. The gas in each case burns with a blue flame, but the heat content is evidently low.
Trends Shown by Tests
TIME-MINUTES
Figure 2. Temperature of Retort e t Progressive Times during the Destructive Distillation o f Bagasse
much more rapid-15 minutes for a 100" rise. I n this test the distillate separated into two distinct layers-an oily tar and a clear red water layer. The distillates obtained for runs 1, 2, and 4 were pale yellow and did not separate by gravity. RUN 6. The rate of heating was changed; a high initial rate was continued for 80 minutes, followed by 30 minutes a t approximately constant temperature, 340" F., and then about 140 minutes of moderate heating. The yields of acetic acid and tar were high, but only an average amount of charcoal was produced. The tar was very oily and light brown in color; the tars obtained from the other tests mere black. RUN 7 . The time and final temperature were approximately the same as those for run 2, but the rate of heating was not so high initially. The charcoal yield was high, being inferior only to that of run 8, while only average amounts of acetic acid and tar were produced. The yield of methanol was somewhat higher than that obtained for runs 5 and 8. RUN 8. This test was made to determine the effect of applying heat a t a moderate rate for a short time. Since
It is difficult to specify conditions for which the highest yields of acetic acid, tar, charcoal, and combustible gas may be obtained because of the many variables. However, possible trends may be deduced. Charcoal yields are shown, as would be expected, t o be lower with a higher rate of heating and with a higher maximum temperature attained in the retort. A higher rate of heating probably causes the driving off of more of the carbon in the form of heavier molecules with a higher ratio of carbon t o hydrogen and oxygen while a slower rate probably allows the cracking or decomposition of these molecules to give a correspondingly higher carbon residue. A lower final temperature simply allows more volatile material to remain in the charcoal. The effect of maximum temperature is best illustrated by comparing runs 2 and 4, where the rate of heating was virtually the same, the only variation being the total time and maximum temperature. I n run 4 the total time was 80 minutes with a maximum temperature of only 630" F.; the maximum temperature in run 2 was 755" F. As a result, the quantity of charcoal obtained at the lower temperature was 14 per cent greater than that a t the higher temperature. The trend toward higher charcoal yields for low rates of heating is demonstrated by runs 7 and 2; the total time and final temperatures were virtually the same, but the rate of heating for run 7 was lower than for run 2. The charcoal yield for run 7 was approximately 18 per cent greater than that obtained for run 2. The trend toward increased charcoal yields for low rates of heating is further substantiated by comparison of run 1with run 5, where the rate of heating was considerably lower. The charcoal produced for the two tests are practically the same despite the fact that the charge for run 1 was heated 40" higher. Thus the statement that the charcoal yield is improved by slow heating is indirectly substantiated. The maximum retort temperature seems to have a more important effect on the amount of charcoal produced than the rate of heating. The importance of maximum temperature is illustrated by run 8 where the highest charcoal yield was obtained. I n this test the rate of heating was moderate, but owing to the shortness of this run the final temperature attained was only 618" F. If the above results are classified according to the rate of applying heat-for example, high rate and low rate-and these general headings are subdivided according to the time required to complete the test, analysis of the problem of determining the best operating conditions is simplified.
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different ratios of binder to charcoal, and the results compared. I n the first test water was added until the charcoal became moist. Somewhat less than 5 per cent molasses was then added t o produce a suitable briquet. Briquets made with an aqueous solution also proved satisfactory, using a little less than 5 per cent starch. Sufficient water was added t o make the charcoal just fluid enough to be handled. These briquets, however, were not quite equal to these made from molasses. The molasses produced a stronger bond between the charcoal particles; and it is believed that a lower ratio of molasses could be used in plant equipment than was required in the laboratory experiments. I n making briquets from hardwood charcoal, the lump material must be pulverized. This is not necessary with the charcoal from bagasse. After the binding agents have been added to hardwood charcoal dust, the mixture in a plant is sent to a set of rollers having recesses to give the usual biscuitlike or pillow shape. Doubtless this process would also be used with charcoal obtained from bagasse. For the present tests, however, the briquets were in the form of cylinders. They were made by ramming the charcoal into a standard pipe nipple of 1-inch iron pipe size, with a fitted plunger pressed in with a standard machinist's vise. After the briquets were formed and shaped, they were dried in a n electric oven a t 88" to 90" C. They were then examined and found to retain their shape and be capable of withstanding the moderate pressures required of any charcoal briquet.
5 0
.2
I
w
I
2 .I 0
>
Vol. 35, No. 3
0
.3
.2 .I
Destructive Distillation of Bagasse Compared with Other Materials
0 0
20
40
60
80
100
120
T I M E - MINUTES
Figure
3.
Evolution of Gases
Classifying the results in such a manner, a slight trend toJyard increased acetic acid yields were observed for high rates of heating; an exception is run 6. Perhaps this can be explained, since the initial rate of heating for this test was high-that is, for the heating period between room temperature and 250" F. These results are not to be regarded as final or as describing the complete story on the destructive distillation of bagasse. Such factors as size of retort, design of furnace and method of applying heat, method of charging the retort, etc., affect the time, rate of heating, and yield relationship. However, these results indicate a trend and show that the destructive distillation of bagasse gives valuable products, the exact amounts of which will vary somewhat with the design and operation of plant units. The results merely prove that this process is worthy of further consideration. Fuel Briquets from Charcoal
The charcoal produced was fluffy and bulky and given t o dusting. It had no mechanical strength. To reduce the apparent density, fuel briquets were made which utilized even the fine material present in large amounts which mere otherwise almost valueless. Both starch and molasses were tried as binding material for the briquets in preference to other materials such as tars or pitch or sulfite liquors from pulp manufacture. MolasseR has the special advantage that it is produced in large quantities a t the sugar central. The briquets were made of several
HARDWOOD. The carbonization of bagasse is directly comparable t o the carbonization of hardwood as practiced in many parts of this country; and the products (charcoal, acetic acid, and methanol) are the same. The same sequence of operations used for working up the liquors in a hardwood distillhg plant would serve for the handling of the distillate from bagasse. The usual commercial amounts of products from dry hardwood (4,6) are listed in Table I, although much higher amounts have been obtainable (6). Using run 8 as an example, the amounts of products from the same amount of dry bagasse are shown in Table 11. Almost twice as much charcoal, while less acetic acid and much less methanol, are produced. Table It. Comparison of Products from Carbonization of Hardwood, Wheat Straw, Corncobs, and Bagasse (Run 8)
Weight of material, lb. Raw Dry Charcoal produced, lb. Gas cu f t T o t h l dist.: gal. T a r discharged, gal. 85% crude methanol, gal. a c i d as 100% acetic, Ib. a
Wood
Wheat Straw (1)
4000 3000
O 3 0 :
1000
1000 1060 Ib.
7000
250 26 10 120
Cornaobs (7) 3360 3000
104
11
..26
900
600 lb.
144 14.7
4.0 78
Bagasse 3210 3000 1570 1080 93.5 9.74 1.82 77
Moisture content not given.
WHEAT STRAW. Because of the physical similarity of bagasse to wheat straw, it is interesting to compare the products obtained on the basis of 3000 pounds of dry material. The results on wheat straw are those of Faith (1) who states: "The chief objection to the utilization of straw is the cost of collection. With the present trend to the widespread use
