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INDUSTRIAL A N D ENGINEERING CHEMISTRY
is described by Kershaw.28 The pitch is fed upon a special type of fire bar consisting of a channeled trough sloping slightly from the front to the back of the grate. The same writes mentions the use of pitch in internal-combustion engines in mixture with creosote oil, and claims that satisfactory operation is obtained by the aid of pilot ignition, using 5 per cent of petroleum oil. The use of pitch as a liquid fuel is closely related to the use of tar directly. I n 1920 more than 46 per cent of all the coal-gas and coke-oven tar produced in the United States was consumed a t the point of origin,l largely or entirely as fuel. This large consumption is due chiefly to the popularity of coke-oven tar as a source of fuel for the open-hearth furnace. Here the liquid tar is supplied to a burner or gun where it is atomized under 50 lbs. steam pressure. The flame is thin and light and much hotter than that from producer gas, the tonnage of the furnace is increased, and the fuel consumption diminished. (In mixed metal practice which has come under the writer’s observation, 5 B. t. u. in the form of tar were equivalent to approximately 8 B. t. u. in the form of coal charged to producers, and between 6 and 6.5 B. t. u. in the form of producer gas.) The construction of the furnace is much simplified. Moreover, tar possesses the advantage that it can be used in furnaces in which the gas sewers are burned out, and that it can be stored for use in those plants which are confronted by a seasonal natural-gas Owners of open-hearth furnaces would welcome the pitch in a form as satisfactory as that of the tar. This involves the burning of a soft pitch. Essential factors are the viscosities of the tar and pitch and the yield of tar oil. The change in density is not serious, Under certain conditions tars and pitches undergo very great reduction in their viscosity when heated, and this property is utilized daily in the handling of these materials, but the literature contains very little information upon the rate of change of viscosity with temperature and the magnitude of the change in viscosity with changes in the amount of oil removed. This problem is considered in another paper,aoby the writer, which gives technical Values for the viscosities of a number of coke-oven tars and their soft pitches a t a number of temperatures near the sharp bend in the viscosity-temperature curve, together with mathematical interpolation formulas which permit the calculation of approximate viscosities a t various other temperatures and oil yields. The economic recovery of Diesel fuel distillates with the production of a uniform grade of pitch can best be obtained by a process of continuous distillation. A continuous still has recently been developed which is very suitable for this purpose. The design appears to present a large number of very desirable features, among which may be mentioned the following : 1-Heat is applied upon vertical surfaces only, thereby diminating high temperatures a t points which may be coated with insulating solids deposited by the heated tar. By eliminating “burned out” still bottoms, the life of the still should be materially increased. 2-The entire still charge is subjected to a violent thermal agitation which effectively scours loose debris from all surfaces and prevents its redeposition. This agitation also diminishes local overheating with attendant coke formation, and tends to increase the oil yield and diminish the pitch yield. 3-The ratio of heat-transfer surface to the volume of still is very large, permitting high rates of distillation with small installations and without exposing large volumes of tar to the heat,
** Gas World. 68 (1918), 234; C.A . , 12 (1918),1416. *e Ferguson, Chem. Met. Eng., 21 (1919), 610; C. A . , 14 (19201,520. ( 0 “The Viscosity of Coke-Oven Tars and Soft Pitches.’’ Presented before the Section of G a s and Fuel Chemistry at the New Haven meeting.
Vol. 15, No. 5
4-The absence of local overheating should materially aid in fractionation. The design includes other features which should assist in this, a desideratum not approximated by many designs of continuous tar stills.
EXTENT OF COAL-TARRESOURCES If all the coke-oven and coal-gas tar burned or otherwise consumed by the producers in the United States in 1920calculated as the difference between the tar produced and the tar sold-had been treated in a continuous still for the removal of oil equivalent to 25 per cent of its volume and the production of soft pitch, there would have been obtained about 48,000,000 gal. of distillate, or sufficient fuel to furnish over 100,000 horsepower-years, if the entire distillate were fed to Diesel engines. This, of course, is only a very small fraction of the power which might have been produced from other oil resources. However, by-products from such a distillation might assist materially in overcoming shortages in other fields. Thus, there is to-day a serious shortage of cresol and phenol. If the tar mentioned above contained approximately 2 per cent of phenol plus cresol, there would be available a total of approximately 30,000,000 lbs. of thesesufficient to completely overcome this shortage. Crediting these to the process and assuming reasonable costs and the maintenance of reasonable price levels, it can be shown that the producer would secure his Diesel fuel a t little or no expense, as a profit for the operation. SUGGESTION FOR FURTHER RESEARCH I n closing this account of recent accomplishments bearing upon the use of coal tar as a fuel for internal-combustion engines, it is fitting to suggest for research one phase which apparently remains rich in unsolved problems and poor in accomplishments-namely, the utilization of coal-tar pitches directly for the manufacturer of producer gas. Von der Forst31 states that the tar oils have been used for this purpose in the United States. If so, this is the only instance of such use which has come to the writer’s attention and this use is certainly not extensive. Various processes for gasifying pitch directly have been proposed, but so far as the writer is aware, none have been sufficiently successful to warrant wide-spread adoption. a * Slahl
u. Ekscn, 81 (1911). 1652; C. A , , 6 (1912),1670.
The Magic Wand‘ By Harvey A. Neville UNIVERSITY OF ILLINOIS, URBANA, ILL.
The inevitable lecture experiment and popular trick of “changing water into wine” may be convincingly accomplished by means of a stirring rod made of glass tubing. This instrument, as shown in the accompanying drawing, is easily constructed as follows: The ends of a piece of glass tubing of any convenient size and length are almost closed by heating them carefully in a small flame. The middle portion of the tube is then heated until it collapses and the tubing is pushed toward the center to thicken and close it. One end is to be filled with an acid and the other with an alkali solution. This is done by heating the chamber to drive out some of the air and placing the end in the solution. The liquid which enters is boiled to drive out the remaining air and the solution will now fill the reservoir completely. With phenolphthalein as indicator the color may be made and destroyed by alternating the ends of the stirring rod, the change being made surreptitiously while wiping with a towel. The openings should be so small that the liquids will not drop out, but the acid or alkali will diffuse through. The mystery may be increased by having the acid red (methyl orange) and the alkali blue (ammoniacal copper salt). Other combinations will occur to anyone. 1 Received
April 2, 1923.
