I N D U S T R I A L A NLD E N G IN E E R IN G C H E M I S T R Y
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FIGURE9. CORRELATION CURYEOF THERMAL VISCOSITY TESTWITH BAKEFLOW TESTFOR CELLULORE LITE-OLSEN ACETATEP L l s T I C S
cosity. The relation is nearly linear in the range 50 to 80 per cent. Figure 8 gives the temperature-viscosity relation of certain polyvinyl acetate-chloride, methyl methacrylate, and polystyrene plastics. This viscosity test may be correlated with standard flow tests on similar groups of materials and serves as an inexpensive method of flow determination. A typical correlation curve for cellulose acetate is shown in Figure 9. The curve is linear and nearly a t a 45" slope, which indicates that the viscosity curves are nearly parallel over the temperature range involved, However, as Bakelite-Olsen tests are carried out a t lower temperatures, there are some inversions due to the differing rates of decrease in viscosity with increase in temperature of some groups of plastics (7).
Vol. 33, No. 11
Experience has shown that for each forming machine or process there is a characteristic viscosity which a plastic must possess if optimum results are to be obtained. Thus when the best operating temperatures for several different plastics are found by experiment on a machine under similar production rates, reference to a viscosity-temperature chart of those plastics will give a fairly definite viscosity which may be considered as characteristic of the machine. TT'hen once the characteristic viscosities of several machines or processes are known, a laboratory determination of the viscosity-temperature relation will prophesy all of the various operating temperatures required for a plastic. I n experimental work, a known operating temperature in conjunction with a stability temperature will render valuable savings in many instances. I n large high-speed machines much material may be wasted in determining operating temperatures by cut-and-try methods. With a laboratory guide, this waste may be considerably reduced.
Acknowledgment The writer wishes to acknowledge the assistance of James Bailey and the Plax laboratory staff, Literature Cited (1) Bender, Wakefield, and Riley, A. S. T. M.Symposium on Consistency, p. 67 (1937). (2) Burgers, J. &I.,1st Rept. on Viscosity and Plasticity, pp 67-72, Amsterdam, Aoad. of Sei., 1935. (3) Gloor, W. E., private communication, Nov. 9, 1940. (4) Houwink, "Elasticity, Plasticity and Structure of l l a t t e r " , p . 12, London, Cambridge Univ. Press, 1937. (5) Ibid., p. 144. (6) Lillie, H. R , J . Am. CeTam. Soc., 14, 502 (1931). (7) Meysr, L. W. A., AIodern Plastics, 18, No. 4, 59 (1940). (8) Penning and Meyer, A. S. T. M . Symposium on Plastics, p. 23 (1938). (9) Trouton, F. T., Proc. Roy. Soe. (London), A77, 426-40 (1906).
Heat Requirements for Steam Distillation of Turpentine Gum E. L. PATTON AND R. A. FEAGAN, JR. Naval Stores Station, Bureau of Agricultural Chemistry and Engineering, U. S. Department of Agriculture, Olustee, Fla.
I
N MODERN gum naval stores plants turpentine gum, either crude or refined, is converted by distillation into products long familiar to commerce-turpentine and rosin. Heat may be supplied to the still by direct fire, by hot oil, or other heat-conveying liquid in coil or jacket, or by a condensing vapor in coil or jacket. The direct-fired still is always hazardous, even when properly designed, and since steam-heated stills are easily controlled and are relatively free from fire hazard, the use of the steam still will undoubtedly become more common. In the development work of the Kava1 Stores Station we had occasion to determine the steam consumption of a tur-
pentine still, and the data are presented here for the benefit of those wishing to design steam-heated kettles for the batch distillation of turpentine gum. The still was a copper, pot-bellied kettle containing about 100 square feet of coil area and was insulated with a 2-inch layer of 85 per cent magnesia lagging. In the distillation of turpentine gum, water or open steam is added to the charge to start the distillation of the turpentine a t a temperature below its own boiling point. The rate of addition of water or open steam (or both) is controlled so that the temperature of the charge rises gradually and all the turpentine is off when the charge temperature reaches the turning-out point (300' to 330" F.).
November, 1941
INDUSTRIAL A N D ENGINEERING CHEMISTRY
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pentine, and to vaporize the water. The latent heat of turpentine was obtained from Perry (g), and the specific heats of turpentine and rosin were taken from VBzes and Dupont (3). I n every case the calculated heat ranged from 8 to 20 per cent lower than the measured heat requirement. This is partly accounted for by the loss in heat t o the air and by the heat required to isomerize the gum acids to rosin acids. These factors were not considered in making the calculations. The turpentine content of the gum charges ranged from about 13 to about 34 per cent, thus covering all gum compositions encountered in present-day gumprocessing plants. INTERIOR OF WORKSLABORATORY BUILDING. NAVALSTORESSTATION. To illustrate the usefulness of these OLUSTEE,FLA. data consider the following example: A turpentine still is to be heated by steam and must handle a 4000-pound charge of turpentine gum I n the tests considered here, the open steam was metered to in one hour. How much steam at 200 pounds per square the charges by a 3/4-inch, calibrated, Flocontrol valve, and inch gage must be supplied? What size boiler will be the condensates from the coils were weighed. These weights, necessary? together with steam pressure measurements and steam table For a conservative estimate, the highest value of steam convalues (I), allowed the calculation of the total heat required to sumption listed in Table I can be used to show that 0.992 X run the charges. Values obtained from several runs are shown 4000, or 3970 pounds of 200-pound steam will be required to in Table I. Heat requirement has also been expressed as distill a 4000-pound charge of gum. Since the charge is to be pounds of 200-pound steam per pound of gum distilled. distilled in one hour, the boiler must be of a size sufficient to produce at least 3970 pounds of 200-pound steam per hour. This is equivalent to a boiler rating of approximately 100 FOR STEAM DISTILLATION OF TABLEI. HEATREQUIREMENTS TURPENTINE GUM boiler horsepower. Due allowance should be made for heat Lb.of 200losses that might occur between the boiler and the steam still. Lb. Steam Required These data are presented for the assistance of engineers Still Charge Running per Lb. Charge Weight, Time, Heat Required of Still faced with the problem of designing naval-stores processing No. Lb. Ilr. B. t. u. X lo-; Charge equipment. Further information on this or other naval stores problems can be obtained from the Naval Stores Research Division, Bureau of Agricultural Chemistry and Engineering, United States Department of Agriculture, Washington, D. C.
Literature Cited A heat balance was calculated as a check on the measured values listed in Table I. The calculated heat requirement included that needed to heat the charge, to vaporize the tur-
(1) Keenan, J. H., “Steam Tables and Mollier Diagram”, New York, Am. SOC. Mech. Engrs., 1930. (2) Perry, J. H., et al., Chemical Engineers’ Handbook, N e w York, MoGraw-Hill Book Co.,1934. (3) Vbzes and Dupont, “Les resines e t t&kbenthines”, Paris, J. B . Baillibre & Fils, 1924.
MAIN PLANTOF NAUGATUCK CHEMICAL DIVISION, UNITEDSTATES RUBBER COMPANY (SEEPAGE1347)
