January, 1927
INDUSTRIAL AND ENGINEERING CHEMISTRY
a t the top in rotation, and the flat circular platform, carrying all the vertical retorts fixed side by side, forming a complete circle, moves around so that the retorts travel in a circular firebrick channel or passage, which is externally heated by a series of gas burners in a concentric combustion chamber contained within an outer wall, the whole forming a very large circular brickwork construction like a kiln. After completing the circuit the retorts are each discharged through the bottom and again pass under the overhead hoppers. It is understood that for a setting with a throughput of 70 tons of coal per 24 hours the temperature in the combustion chambers will be 1202' to 1382' F. (650' to 750' C.), each retort being 5 to 6 feet high and 4 feet 6 inches wide, with a thickness of charge of 6 inches a t the top and 8 inches a t the bottom, while the total period of travel will be about 8 hours, of which, however, approximately one-third will be cooling off in the retort. Wollaston Processes The latest British developments in the fields of low-temperature carbonization and total gasification include the Wollaston processes, primarily the invention of T. Roland Wollaston and controlled by the Wollaston Gas Producers (Manchester), Ltd., the various patents commencmg in 1917. These are of two main types. The first is essentially, with numerous modifications, a combined vertical, mechanically continuous, preheating retort for low-temperature carbonization, placed on the top of a producer gas generator for total gasification on the usual lines by means of a steam and air blast, the gas passing up through the descending charge and mixing with the rich gases and vapors evolved by the advance low-temperature carbonization. The main object of the Wollaston process in its present stage of development is not so much the recovery of low-temperature oils, although this will be a valuable feature, as to render possible the use in producer-gas generators of every description of swelling bituminous or other difficult coals that would otherwise give rise to the familiar troubles of sticking together of the charge and irregular gasification, combined with the recovery of the maximum amount of sulfate of ammonia 70 pounds per 1 per cent nitrogen in the coal. The main feature is the design of the preheating vertical, cylindrical retort, which is arranged by means of transverse division in the form of a series of sections or compartments one above the other with scrapers or ploughs, so that the material is always in a thin layer, while being turned over and agitated as it passes down from one compartment to the other. The hot gases from the generator below enter a t about 1112' F. (600' C.), the time of travel in the preheating retort is 20 to 40 minutes, and the mixed gases and vapors leave the top a t 482' F. (250' (2.). The first plant on these lines was erected a t the Fishwick Dyeworks of George and R. Dewhurst, Ltd., Preston (Lancashire), and has been very successful, while a number of other installations are now a t work. The gas from small bituminous slack averages, without recovery of oils, about 45.5 per cent combustible, (17 per cent CO, 24.5 per cent H2, and 4 per cent CH,, etc.), with a heat value of 183 B. t. u. per cubic foot (net) and a yield of 125,000 cubic feet per ton, The second Wollaston process, which does not include recovery of by-products, is the combination in one setting of a producer-gas generator and a vertical, tubular, or locomotive type of boiler especially intended for the efficient utilization as fuel of coke breeze and general colliery refuse material, both high ash content, and general canneloid products. These are extremely difficult to use efficiently for steam generation in the ordinary way, but it is claimed that with a special design of small producer-gas generator the ma-
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terial can be gassed and all the gas burned direct in the setting with 16 to 19 per cent carbon dioxide, smokelessly and a t high efficiency. The principle of firing furnaces, not with solid fuel direct, but by means of an integral or adjacent generator in which the fuel is first gasified and the gas then burned, is ancient in origin, going back well over half a century. Wollaston, however, in his setting design adopts improved principles, in which, for example, the raw fuel is first preheated in the gasfired combustion chamber itself, any gases or vapors evolved being burned directly. The heated raw fuel then passes down gradually into the generator. Wollaston also uses this principle for vertical water tube and other boilers where it can be used efficiently. This is quite different from the internally fired cylindrical Lancashire boiler, with which so many of the earlier investigators worked. As typical performance figures using coke breeze with 19.5 per cent moisture, 25.5 per cent ash, and 8028 B. t. u. per pound in conjunction with a small vertical boiler, the carbon dioxide averaged 18.3 per cent, the combined efficiency of the generator and boiler being 73.8 per cent without feed water economizer, and 88.8 per cent for the generator only, while the gas had 22.2 per cent carbon monoxide, 13.7 per cent hydrogen, and 6.7 per cent carbon dioxide. Here also a number of installations are a t work and on order.
A Yellow Ink for Marking Rubber Tensile Strips' By Clifton G. Cashion PHILADELPHIA RUBBERWORKS Co., AKRON,OHIO
HE need of a light-colored ink for marking tensile and other test strips has long been felt by many rubber physical testing laboratories. The dark aniline inks and yellow crayons now employed are sometimes useless owing to the nature of the rubber or to the lighting conditions of the laboratory. A satisfactory ink may easily be prepared by any testing laboratory as follows: A soluble lead compound is precipitated as insoluble yellow lead chromate by the addition of potassium chromate. The solution containing the precipitate is boiled and then filtered. After filtering and before entirely dry the lead chromate is ground into glycerol. The proper consistency of the ink is best determined by practice.
This ink is used with a blank pad obtained at stationery supply houses. The pad is covered with the ink and dampened with glycerol as it dries. The right degree of dampness of the ink must be learned by experience, as a too wet or too dry ink will not give clean lines or the lines will be too broad for efficient work. It will be necessary to clean the markers often, if they are to give clear, clean-cut lines. Especially in stress-strain work a blurry line tends to throw the elongation a large percentage off the correct reading. This ink is especially valuable in working with black treads, both new and aged, as they have a tendency to absorb the aniline inks as soon as the rubber has stretched several hundred per cent. The use of this ink has entirely eliminated the loss of stress-strain determinations in this laboratory due to the elongation lines becoming invisible while stretching. In aging work, where the dimensions are marked previous to aging, this ink is valuable as it is permanent in the life oven. It is also permanent to a very high degree in water, steam, and fire. 1
Received September 4, 1026.
