A small additional plant is needed, by which a small percentage of the oil is revivified, in order to keep it active for benzol absorption. This consists of a simple tar still and con denser, in which the tar-oil is freed from most of the napthaline and other hydrocarbons in cidentally absorbed. The presence of an exces sive percentage of them in the tar-oil would in terfere with a complete benzol absorption. It is unnecessary to describe here the details of the benzol distilling plant. A great number of these are in operation in connection with German by product plants.
Coke Oven Brick.— Under construction the principal feature of an oven is in the brick used. What is termed silica brick is now being used, and probably will be the standard coke oven brick of the future. It has been deter mined that the fusing point of a silica-alu mina brick reaches the lowest temperature at 60 per cent silica and 40 per cent alumina, but if the silica is increased up to say 90 per cent, an infusible brick of the highest quality is the result.
For all classes of work, a good high grade plastic No. 2 fire clay, with possibly a small amount of flint clay, should be used. This will make a creamy, sticky slip, which will make an excellent joint. The joints are always weak spots, and are therefore a necessary evil. The brick should always be dipped into the mortar, which should be of the consistency of cream, and rubbed on each other to make a good tight contact.
Coking Coals.— There are three principal coal area sections in the United States supply ing good coking coal. The Connellsville section in Pennsylvania was the first developed, and it is reported that this supply is fast disappearing. The second section is that of the Pocahontas field in West Virginia, and the third is in Colo rado. As the good coking coal fields disappear, so will the by-product ovens come into use, for it is possible to coke a coal in a by-product oven that it is practically impossible to coke in the beehive type.
Production.— In 1915, according to the re port of the United States Geological Survey, there were in the United States in active opera tion 48,985 coke ovens of the beehive type and 5,982 by-product ovens. There were also 44,125 beehive ovens and 286 by-product ovens idle; and 557 beehive and 1,191 by-product ovens building. During the year 1,563 ovens were abandoned. The quantity of coke produced in that year was 41,581,150 tons, valued at $105, 503,868, about the usual average production, but an increase of about 20 per cent over the low production of 1914. The beehive ovens con sumed 42,278,516 tons of coal,producing 27, 508,225 tons of coke, valued at $56,945,543, an average value of $2.07 per ton. The by-product ovens consumed 19,554,382 tons of coal, produc ing 14,072,895 tons of coke, valued at $48,558,325, an average value of $3.45 per ton.
Among the coke-making States Pennsylvania ranked first, producing 22,53(),567 tons of bee hive coke, and 4,301,726 tons of by-product coke. Virginia ranked second in the production of beehive coke, with 1,250,235 tons, followed by Alabama with 1,001,479 tons. Indiana was sec
ond in by-product coke, with 2,768,099 tons and followed by Alabama with 2,070,334 tons and Illinois with 1,686,998 tons.
About two-thirds of the entire output of coke in the United States is made in Pennsylvania, and 72 per cent of the Pennsylvania output is made in the Connellsville district, with its upper and lower extensions. In Connellsville in 1915 there were 21,343 ovens active; in Lower Connellsville, 16,037 ovens; and in Upper Con nellsville, 2,552 ovens; and 605 more were under construction.
The value of the by-products of the coke industry in 1915 was $29,824,579, an increase of more than $12,000,000 over the previous high record mark of 1914. The greater part of this increase was in benzol and benzol products, which in 1914 were valued at $997,007, and in 1915 at over $7,000,000. Previous to 1914 the demand for these products had been small and the prices low, the market being supplied almost wholly by the coke ovens of Germany. But the off of this source by the war created an imperative demand at almost any price for the raw material for dyestuffs and high explosives, the products of the distilla tion of coal, and the by-product coke ovens be came of unwonted importance. Among the more valuable by-products of the coke industry in 1915 may be mentioned the following: Gas, illuminating and fuel, 213,667,614,000 cubic feet, valued at $8,624,899; ammonia, anhydrous and liquor, a value of $9,867,475; tar, 138,414,601 gallons, valued at $3,568,384; benzol, 2,516,483 gallons, valued at $1,428,323; toluol, 623,506 gallons, valued at $1,529,803; crude light oils, 13,082,678 gallons, valued at $4,304,281. The yield of coke in the different plants ranged from 1,340 to 1,550 pounds per ton of coal con sumed, and the tar production ranged from 5.5 to 13 gallons per ton. The recovery of ammonia reckoned as anhydrous was from 4.33 to 6 pounds per ton, equivalent to from 13.5 to 25 pounds of ammonia sulphate.
Consumption.—The consumption of coke in the United States in 1915 amounted to 40,394,445 tons, of which 53,222 tons were imported, and the remainder of domestic origin. About 36, 700,000 tons (91 per cent) were used in blast furnaces; 1,665,000 tons (4 per cent) in foundries; and 1,974,000 tons (5 per cent) for domestic purposes. The exports of coke for 1915 amounted to 895,509 tons, of which about 74 per cent went to Canada and 18 per cent to Mexico.
Bibliography.— Byrom, T. H., and Chris topher, J. E., (Modern Coking (Lon don 1910) ; Fulton, J., Treatise on the Manufacture of Coke' (Scranton 1905) ; Gas Machinery Company, 'By-product Coke Ovens' (Cleveland, Ohio, 1915) ; Lewes, V. B., The Carbonization of Coal' (London 1912); Wagner, F. H., 'Coal and Coke' (New York 1916) ; United States Bureau of Mines Tech nological Papers 8 "Methods of Analyzing Coke" and 50 °Metallurgical Coke" (1912-13); United States Geological Survey, "Mineral Re sources of the United States, 1915° (Wash ington 1917).