676
INDUSTRIAL AND ENGINEERIXG CHEMISTRY
vo= v-Ho -760h - m
X-
273
t
+ 273
where V = volume of water run out of aspirator in cubic centimeters HO= barometric reading corrected to 0" C. lz = vapor pressure of water a t t m = reduction in pressure indicated by the manometer t = final temperature of the aspirator
Table I11 gives the results obtained. From these results curves were plotted (Figure 2) which show clearly the relationship of the vapor pressures between the various nitric esters. Also, the logarithms of these values were plotted against temperature and the resultant curves were found to be practically straight lines. Discussion The results obtained in these tests on nitroglycerin are higher than those reported by hfarshall and Peace (4). This is probably due t o the fact that free liquid glycerol trinitrate either has a higher vapor pressure than nitroglycerin in a nitrocellulose gel, or that their air current never became saturated under conditions of their tests. The results reported by hIarshal1 and Peace are given in comparison with the writer's values:
c. 20 30 40 50
MARSHALL A N D PEACE
CRATER
Mm.
Mm.
0.00028 0.00083 0,0024 0,0073
0.0016 0 0033 0.0068 0.0238
Vol. 21, No. 7
The vapor pressure of ethylene glycol dinitrate as reported by Rinkenbach (6) is 0.0072 mm. a t 0" C., and 0.0565 mm. a t 22" C., as against 0.0465 mm., the value from the curve in Figure 2 for this temperature. He also reported the vapor pressure of diethylene glycol dinitrate ( 7 )as 0.0098,0.0079, and 0.0044 mm., average 0.007 mm., of mercury a t 22.4" C. as against 0.0055 mm. taken from Figure 2. The following arrangement of the nitric esters studied is according to their increasing vapor pressures: (1) glycerol trinitrate, (2) diethylene glycol dinitrate, (3) trimethylene glycol dinitrate, (4)ethylene glycol dinitrate, (5) propylene glycol dinitrate. Because of the higher volatilit'y of the latter esters their use is limited in the explosives industry. For instance, they do not lend themselves to making certain types of propellant powders, which require 'high drying temperatures. On the other hand, if proper care is exercised in the manufacture and if the formulas are adjusted t o care for the higher vapor pressure, ethylene glycol dinitrate, for example, is an excellent substitute for nitroglycerin in dynamite. Literature Cited (1) (2) (3) (4) (8) (6) (7) (8)
Baxter, Hickey, and Holmes, J . A m . Chem. SOL.,29, 127 (1907). Chiaraviglio and Corbino, Gaze. chim. ital., 43, 390 (1913). Marshall, J . SOL.Chem. Ind., 23, 158 (1904). Marshall and Peace, I b i d . , 109, 298 (1916). Regnault, A n n . chim., 15, 129 (1845). Rinkenbach, IND. Esc. CHEX., 18, 1196 (1926). Rinkenbach, I b i d . , 19, 925 (1927). Smithsonian Physical Tables, 6th revised ed.. 3rd reprint, p. 154
Use of Super-Cel in the Sugar Refining Ind u stry1j2 Arthur Elsenbast, R. D. Elliott, and E. J. Sullivan JOHKS-MANVILLE CORPORATION, 292 MADISON A m . , NEW YORK,X. Y .
T
HE application of diatomaceous silica to sugar refining problems was not brought to a satisfactory state until within the last fifteen years. At that time the Celite Section of the Johns-Manville Corporation, through the availability of a tremendous supply of pure diatomaceous silica, was able t o produce the first standardized filter-aid product, known as Filter-Cel. This product, which has been used for many years as a standard in the sugar industry, has now been supplemented by the addition of two mechanically and chemically processed materials known as Standard Super-Cel and Hyflo Super-Cel. This gives the sugar refiner the choice of three entirely different filter materials to meet the conditions existing in a particular plant and on a particular liquid. The recommended filter aid will vary in different plants, according to the layout and the type of sugar being turned out. It was thought that a general survey and summary of the determined and known characteristics of the different sugar filtrations would be of interest to the entire sugar industry. All of these filtrations have now been carried out over long periods of time, and on a factory scale. The costs are known, and the benefits judged. Tables I, 11, and I11 give, in a general way, a summary of the major filtrations. 1 2
silica.
Received M a y 18, 1929. Super-Cel is t h e trade name of a patented processed diatomaceous
Application of Hyflo Super-Cel to Sugar Liquids The sugar refiner very early recognized that 'a high-quality sugar could not be obtained except from clear, sparkling liquids. A pure, colorless, white sugar could not be boiled except from clear, sparkling sirups. A good grade of plantation white sugar can be boiled from a comparatively highly colored 75 to 85 purity sirup if the sirup is clear. The art of manufacturing filter presses has also received a very marked advance within the last ten years. A combination of improved filter materials and filter presses has now made i t possible to filter economically every different type of sugar sirup produced in the various refining processes. The basis of most clarification systems is t o obtain a precipitate which can either be settled or filtered out of suspension. The Hyflo Super-Cel is a neutral, inert, and ready-made precipitate which acts mechanically t o make filtration possible. In various sugar refining processes it has been found of decided economic advantage to filter the liquors a t various stages, and the reasons for the filtrations specified in the tabulations are outlined in the following discussion. Refinery Cane Sugar from Raw 96" Test Cane Sugar The flow chart shows the general diagrammatic handling of the cane-sugar liquors in a modern bone-black refinery. The two most important liquids that are filtered are the washed sugar liquor, which totals 85 per cent of the total
I X D U S T R I A L ALVDENGINEERISG CHEMISTRY
July, 1929
Table I-Filtration HYFLOSUPER-CELUSEDo b BRIX S O L I D S
LIQUOR hIin
Max
7c
XV
-1
677
of Refinery Cane Sugar
TEMPERATURE FILTRATION DFNsITV Brix.
Washed sugar Affination sirup Remelt, !ow grade White-sugar remelt Granulated sirup Thick sweet water Soft liquor Melted raw sugar
!
FILTER AREAPER 500 TONSSUGAR PER 24 HOURS Filter area
TvDica! installation
sq. JL.
2500 2500
I500 500
Three 850-sq. ft. presses Three 850-sq. ft. presses Two 800-sq. ft. presses One 500-sq. ft. press
Conversion factors: 1 square foot = 0.09 square meter; 1 short ton = 0.907 metric ton
sugar, and the wash sirup, or affination sirup, which com- white sugar from the melt, it is necessary t o filter the affination sirup. The affination sirup is diluted to 50" to 55" Brix prises about 15 per (cent of the total solids. WASHEDSCGARLIQr-oR-The washed sugar liquor is corrected, heated to 186" F., limed the same as the washed heated to 185" F. and milk of lime is added until the liquor sugar liquor, and treated, on the average, with 1 per cent is neutral to litmus or acid to phenolphthalein, or, on the of Super-Cel on Brix solids. The resulting liquid is a clear, hydrogen-ion scale, from 7.0 to 7.4 pH. The Elyflo is added brilliant, highly colored sirup, which is in the proper conto the heated liquor and pumped through the press. The dition to run over the bone char. Based on the melt, this resulting washed sugar liquor is brilliantly clear and is filtration requires approximately the same amount of filter then sent directly over the bone char for bleaching. Quanti- area and filter aid as the washed sugar filtration. Owing ties of filter aid are given in the tabulation. The filter- to the concentration of impurities in this sirup, it is a very press cycles will vary, according to the quality of the raw difficult liquor to clarify, and to date the mechanical clarificasugar, from 4 to 15 hours. At the end of the cgde the excess tion with Super-Cel is the most economical process for its sirup in the press is removed and the cake is either sweetened clarification. This mechanical filtration has displaced lime off in the press or is sluiced from the press :md refiltered and phosphoric acid defecation and bag filtration of this liquid. and sweetened off in a second press. This is standard procedure and many millions of tons of Cane Sugar Refining sugar are handled by this method. ADVASTAGES OF SUPER-CEL WASHEDSUGARFILTRATIOK(1) A minimum amount of lime is the only chemical required; ( 2 ) there is a minimum re-solution of impurities from heat and processing; (3) liquor is in condition for efficient and economical bone-char operation; (4)decolorized bone-black liquor is absolutely brilliant, and in condition to produce the highest quality white sugar. COST OF OPERATION-By this mechanical process the sugar is run through the filters in a continuous stream with no loss by inversion during the process. The labor cost for handling one million pounds of sugar through the filter station is cut down to that of two men per shift. The sugar losses are cut down to the sucrose in a porous press cake, which can be washed down to a 0.5 per cent sucrose content with a minimum amount of wash water, making a loss of about 60 pounds of sugar per million pounds of melt. The washed sugar liquor is filtered for three reasons: (1) because the bone-char cisterns must be supplied with clear, brilliant sirup so that the bone char itself will perform its maximum decolorizing action and retain its life for the longest time; (2) so that the sugar can be washed from the bone char with the niinimum amount of water and sugar loss: (3) the pans must be supplied with a uniform and continuous IS>rup !o W h i v P m i W R ~ m r l r stream of absolutely clear, brilliant liquor. V ~ w h
