DURING the military maneuvers last summer it often happened that the mitraillcur--a quick-firing machine gun for the infantry--arrived too late at the point of destination. This deficiency was caused by the difficulty of transport; for the gun with support weighs 175 pounds, the gun being 42 pounds and the support 133 pounds. This is a heavy load for men to carry, combined or separate. To remedy the difficulty the Dutch army authorities are now making experiments with the invention of a Belgian officer, i. e., a very light cart drawn by two strong dogs. This device has already been adopted by the Belgian army for the transport of infantry mitrail-Icurfi and has been found eminently satisfactory--even more so than the transport by horses of this same kind of guns for the artillery. The very light cart, whose construction can be plainly seen in the photograph, weighs 220 pounds. Dogs and cart can very easily jump across any obstacle in the way, and the gun can be placed in position by two men. The same kind of carts and dogs are used to transport the ammunition. The way the dogs are harnessed is plainly shown in the picture. So proud are the dogs of their task and so faithful, that none other than the men of the com- pany to which they belong will dare to touch the gun. IN a series of experiments carried out several years ago by Parr and Francis at the University of Illinois it was found that by coking coal at a comparatively low temperature, say 700 deg. Fahr. or less, the heavy hydrocarbons--those chiefly responsible for the formation of smoke--could be driven off, yielding a gas of high illuminating power and a tar with a high percentage of volatile oil. The solid residue in the still, however, was too friable to be adapted for ordinary tise as a fuel. At the same time it was observed that an important role was played by small amounts of oxygen in the gases surrounding the heated mass of coal. More recently this line of investigation has been followed out further by Prof. S. W. Parr in collaboration with H. L. Olin. They find that under suitable conditions it appears to be feasible, to prepare from Illinois coals, by coking at low temperatures, a coke satisfying all ordinary requirements as regards texture and firmness. We say "under suitable conditions"--for it appears to be essential to maintain an oxygen-free atmosphere around the coal during the process. This was accomplished in the experiments of Parr and Olin by heating by means of steam introduced directly into the retort. At the temperatures employed there was no chemical action between the coal and the steam. The authors conclude from their observations that "the fusible substance of Illinois coals is the true binding material in the coking process; that it is present in such abundance as to produce a coke of too open and spongy a character as a result of the evolution of the large amount of gaseous products which result from its decomposition. In this respect, it is paralleled by the behavior of sugar in the process of coking, which yields as a result of the large volume of escaping gases a very porous mass of sugar-coke or carbon. However, if the raw coal is mixed with a considerable amount of material which has already gone through the coking process, or which has at least given off the larger part of its gases, and then has been reduced to a fine division like breeze, the cementing material of the fresh coal is able to disseminate throughout the mass, and the gases may also escape without blowing it into a spongy mass, with the result that a coke of good texture is formed. Exactly in a similar way, if molasses or other sucrose or glucose material be substituted for the fresh coal, we shall have again the formation of a dense coke capable of retaining its shape under conditions of firing much better than where a plastic binder is used. In both cases a strongly cohering mass is produced which meets the requirements of handling, storage, and combustion with the greatest efficiency and the least formation of smoke. A small admixture of raw coal may thus be made to serve the purpose of a binder for material otherwise wasted as coke breeze, at a cost which would enable it to compete with the pitch binders now in use. This suggests a process of fractional coking, or coking in two stages. The first result at the lower temperature furnishes a product which, when ground to a moderate degree of fineness and mixed with a small portion of fresh raw coal, would furnish the essential conditions for producing a coke of dense nature with a binder so distributed as to give the material a strength quite comparable with that produced by coals of the regular coking variety. Moreover, an advantage would be evident in such material, especially for use in household appliances, in that it would be more lively in combustion and less difficult of manipulation in the matter of maintaining a fire than coke made by the usual methods." For further information regarding this important investigation the reader must be referred to our current SUPPLEMENT. We shall here only add a brief reference to the work of another investigator, Dr. F. R. Bergius, who has shown that by working under pressure and at a moderate temperature we can accomplish in the brief space of a few hours a result closely analogous to that produced by nature in a long time. He heated cellulose at '!50 degrees in water in a closed electrically heated furnace until the pressure became 400 atmospheres. Samples were taken from time to time and it was found that the cellulose had been changed to peat. The result was obtained in twenty-four hours, no further change being obtained in sixty hours. By applying the Van't Hoffi-Nernst law of reaction velocity, it is found that the same change from cellulose to peat at 10 deg. Cent, requires 7,000,000 years--a geological period.
This article was originally published with the title "The Coking of Coal at Low Temperatures" in SA Supplements 75, 1946supp, 353 (April 1913)