COKE, one of the products of the dis tillation of coal in ovens and retorts. It bears the same relation to coal that char coal does to wood. Coke was originally produced by burning coal in piles, with a limited supply of air, much after the modern method of charcoal burning. This plan occasioned a considerable loss of coal, and led to the building of coke ovens, the coke so produced being found to be much harder and denser than that made in open heaps. This open heap or yard-coke, and that produced in retorts, when coal is distilled for gas and other volatile matters, may be used in place of oven coke with a proper blast.
The most efficient method of coking is by the use of coke ovens. The Beehive oven is probably the simplest. Ovens of this pattern are either circular or rec tangular in form and the height and diameter vary upward to 10 feet. These ovens are built of brick, with dividing walls 2 feet thick, lined with fire brick. They are charged from the top, from coal cars running on rails on the top of the ovens. The volatile matter es capes through the charging openings and the coke is removed through a door in the front of the oven. Air is admitted through the door for about 24 hours after firing, when all openings are plas tered up. The entire process occupies about 36 hours, at the end of which the coke is raked out and quenched with water. The heat required to carry on the combustion is usually obtained by burning the volatile gases given off by the coal. The oven most used in the United States is the Semet-Solvay. This
is long and narrow with a door at each end; the roof is supported by heavy masonry. A zigzag flue of four turns runs along each side of the oven, and the gases pass alternately from front to back through the flue to a return flue leading to the chimney at the back. The coal is charged through three charging holes in the roof, which are then closed. The distilled gases pass through an out let at the end of the roof (the only hole left open), into a hydraulic main, where they mix with the gases from other ovens, and are passed through purifiers for the removal of tar and other con densable matter. From the purifier the gas is blown by fans through pipes pass ing beneath the ovens to branch pipes where it is burned, heating the ovens. The air used in the blast is pre-heated by passing through channels in the heated masonry. The coking lasts about 24 hours, at the end of which time a mechanical ram is brought behind the oven and the coke is pushed out by it to a space in front of the oven where it is quenched. The ram is then withdrawn, the doors closed, and the oven recharged while still hot. Coking is carried on to a large extent throughout the United States, both by the use of ovens and as a by-product of gas producers. The total production of coke in the United States in 1918 was 56,478,372 short tons. The State producing the largest amount was Pennsylvania, with a production of 26,