SPENCER ON SUGAR MANUFACTURE CONTROL APPARATUS.
THE MILLING OF CANE IN SUGAR MANUFACTURE CONTROL APPARATUS. By G. L. SPENCER.
Received April 1 , 1910,
Wifh very few exceptions, cane sugar factories use heavy mills in the extraction of the juice. I n very modern plants the milling equipment consists of a crusher and four mills arranged in tandem. Each mill has three rolls so arranged that the cane receives a double crushing in passing through it. The crusher has two corrugated rolls which break the hard stalks and extract a cons'derable part of the juice from them, preparatory to the milling. The pressure upon the rolls is usually controlled by hydraulic devices, that upon the top roll of a mill seven feet long often exceeding 500 tons. The woody residue or bagasse is usually sprayed with water after leaving each mill, except the last of the series, from which it is conveyed directly to the boiler furnaces. The water dilutes the residual juice in the bagasse and facilitates its removal in the subsequent milling. The quantity of juice that may be extracted varies with the setting of the mills, the quality of the cane, care in eeding the cane to the mills, and the quantity o water sprayed upon the bagasse. A careful laborat o w control is necessary to keep a milling plant operating a t its highest efficiency. The control includes the calculation of extraction numbers based upon the weight and analysis of the cane afid juice; the calculation of the percentage of saturation or maceration water , i. e., the water sprayed upon the partly extracted bagasse; the calculation of the dilution number, i. e., the percentage of water required to reduce the density of the undiluted or so-called normal juice to the density of the mixed juices. -4n efficient control requires special apparatus, some very efficiat types of which are described below. Juice Sampler. -The most efficient sampler in the writer's experience is one designed by an engineer of the Calumet Plantation, Louisiana. This instrument (Fig. I) samples in proportion to the quantity of cane ground. It rarely clogs or fails to operate. The Calumet sampler is shown in section in the illustration. It consists essentially of a plunger with a perforation near one end and so arranged that this perforation is alternately plunged into the stream of juice and withdrawn with a sample. The reciprocating motion is imparted by a crank or eccen-
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tric driven by a belt off one of the mill-roll shafts. Fig. I is from a working drawing of a sampler arranged to draw juice from the inclined canal or' chute from a crusher. The projecting lip, inside the canal, insures the filling of the hole in t,he plunger. The sample is discharged from the bottom of the plunger into a gutter leading to a storage vessel containing a preservative. Various modifications of this sampler permit its use in sampling from canals and pipes. Juice Scales.-Automatic scales have been used, usually with indifferent success, in weighing the mill juice. The "hammering" of the heavy charges requires very substantial and expensive construction in an automatic scale and almost constant skilled attention. The hopper- or tank-scale with type registering beam, is inexpensive and efficient. The tanks should be provided with a hot water spraying device to keep them clean. Apfiaratus /or Bagasse Analysis.-Bagasse is necessarily sampled by hand, owing to milling conditions and the nature of the material. It is usually prepared for analysis by cutting with a butcher knife, a knife mounted similarly to the old-fashioned feed cutters, or by chopping devices. An efficient machine is made in Delft, Holland, especially for preparing bagasse for analysis. The customary quantitative tests are moisture, fiber (marc) and sucrose. The writer has devised the apparatus described below to minimize labor and to reduce the personal errors and especially to
Fig. 1.
enable chemists to promptly obtain the desired data. The oven shown in Fig. z j l in section, from a working drawing, will dry zoo-gram samples in about 90 minutes. Efficient vacuum ovens require from__4 t o 1
Suggested by the Soxhlet oven.
T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY.
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6 hours and in order to obtain results promptly with the usual types of ovens, the portion dried must be very small, large samples requiring 24 hours drying. The oven is best described in an outline of the method of using it: 100-200 grams of bagasse are placed in a tared’ brass tube. The tube has a perforated bottom, 625 round holes per square inch, or is of IOO mesh gauze, also a perforated cover. The cover is held in place by bayonette catches. It should enter the tube and have a narrow flange to make a good joint with the edge of tube “ A ” of the oven. The sample tube is inserted into tube A ” and steam
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5-6-20
but for sugar-factory purposes this is unnecessary. Tubes “ A ” and “ B ” should be closed with tight covers when not in use. I n the fiber (marc) determination sample tubes similar to those for moisture are used. These hold from 50 to IOO grams of bagasse. The tube and contents are placed in a stream of boiling-hot water, after a preliminary digestion in cold water; or a syphon apparatus similar to the Soxhlet extractor, without the condenser, into which boiling water is passed, may be used. After the extraction of the water-soluble content of the bagasse, the sample is
A
SECTION
N-L
June, 1910
C-D S T E A M D R Y I N G OVEN
CENTRAL
N U E V A L-UISA.
THE CUDANAWERICANSUCARCO. NEW TORY &CUBA M A R.16, I 9I 0.
Fig. 2 .
is turned into the ejector. The oven door must fit tightly against a soft rubber gasket. The ejector draws air through the distributing pipe, over the steam coils, and through the bagasse sample. The heatingpurface is ample to maintain a very strong current:of air a t a temperature of 1o5O C. The air currentyshould be as strong as the coils will heat sufficiently; this is usually as much as the ejector will draw. The air should be strained through fine gauze before admitting it to the oven. Moisture-free air would doubtless reduce the time required for drying,
drained a few seconds and these placed in tube “ B ” of the oven. The drying is usually completed in less than four hours, notwithstanding saturated condition of the sample. Obviously this type of oven may be constructed for samples of any size and could be readily adopted for certain classes . of work in agricultural laboratories. The wire tray is for use in drying samples of molasses and other materials that are not disturbed by a strong current of air. The writer’s experimental oven was built of 2-inch
BERRY ON FURNACES AND RHEOSTAT. planks, but he has since equipped the laboratories with ovens of cast iron, as per Fig. 2 . The oven should be insulated with magnesia covering. It is very essential that all joints be well made and that air enter the oven only a t the distributing pipe. The nozzle of the ejector is designed for steam of about 70 lbs. pressure, and for low pressure; the opening may be larger than indicated. Failure to obtain the desired temperature, given a good steam pressure, is usually due to leakage of air a t the joints or to drawing too little air over the coils. In the usual method of estimating the sucrose in the bagasse, 50 grams of the material are digested in a flask, a t boiling temperature, with 500 grams of water containing 5 cc. of a 5 per cent. solution of carbonate of sodium. The flask is fitted with a reflux condenser. The time consumed in introducing the bagasse into the flask and the errors involved, the large item of breakage and occasional loss of tests, led the writer to prepare special copper apparatus. This apparatus is a copper beaker 4 inches in diameter by 6 inches deep and provided with a flange and ground joint brass cover. The cover should be heavy and have a hole in it to receive a cork and tube condenser. A straight tube about four feet long forms a suitable condenser. A thin metal tube fixed permanently to the cover may be used but glass is more c.onvenient in controlling the temperature. Clamps are only necessary for holding the cover, when the apparatus is placed in an inclined position in a water bath. An electric hot-plate is the most convenient heating device. It is probable that the new Sachs-LeDocte digesters, but of large size, used in the analysis of sugar beets, would answer in bagasse analysis, especially where a water bath is used in heating. I n this apparatus a brass ring cover is used. A thin rubber
Fig. 3.
cap is slipped over the ring. I n placing the cover in position on the beaker, the rubber is bulged downwards by pressure of the thumbs and on releasing it a partial vacuum is formed in the vessel. This
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vacuum is sufficient to hold the cover in position, providing the contents of the beaker are not heated to boiling. The Sachs-LeDocte apparatus as arranged for use in beet analysis is shown in Fig. 3. A plain copper beaker with a rubber cap slipped over its edges would answer the purpose in bagasse analysis, though the life of the rubber would probably be short. C U B A N - - 4 J I E R I C A N S U G A R COMPANY,
SEW YORKAND CUBA.
AN ELECTRIC COMBUSTION FURNACE, LABORATORY TREATING FURNACE AND RHEOSTAT. By GEORGEM. BERRY.
Received February 1 7 , 1910.
On account of the increased demands upon an already well loaded gasolene gas generator with the attendant impoverishing of the air in the room, where among about one hundred burners six combustion furnaces were kept going constantly during the day, the cost involved owing to the use of high grade gasolene, and on account of the lack of an asuredly sufficient heat to yipld complete combustion, without especial preparation of samples, a t times when the gasolene in generator was getting “thin” the writer determined to use some form of furnace heated electrically. Knowing something of the workings, but nothing of the construction of the furnaces used by Mr. C. M. Johnson,’ and something of the platinum wound furnace described a t the May 1908 Meeting of the Iron and Steel Institute, but not feeling satisfied with either of these, the writer, in July, 1908, set about some experiments with a view to making a more satisfactory furnace. A brief summary of the more important steps of the work and a detailed description of the furnace as adopted, together with some salient points concerning the making and materials, are here given. The first furnace had a IO” x 3” diameter iron cylinder as the outer casing. As the heating element it had a 24IJ x ”i,” bore quartz tube covered for the middle I I ’ ~with asbestos cloth and wound for the middle 73/aNa t twelve turns to the inch with 2 2 gauge (B. & S.) nichrome wire, using twenty-seven feet of the wire. The :pace between the heating wire and the three-inch iron cylinder was filled with chemically pure powdered magnesium oxide. This furnace lasted forty-five ten-hour days. At 115 volts it took 3 . 5 amperes a t first, gradually dropping to 2 . 4 amperes on the forty-fourth day, and yielded a temperature of about 1750’ F., which gradually dropped to about 1 4 5 0 ~ . Furnace No. 2 had a 12’’ x 6:’ diameter iron cylinder as outer casing. As the heating element a 24” x “I,” bore quartz tube covered for the middle 13” with asbestos cloth and wound for the middle y3/[ with 1
J . A m . C h m . Sac.. 80, 773.
