THE COKING INDUSTRY IN HOKKAIDO

The coke (including gas coke) produced in Hokkaido amounts to about 170,000 tons per year, which corresponds to about 16% of the total coke produced throughout Japan, that of the Imperial Iron Works at Yawata excluded. The oven system of the coking plants in Hokkaido is not well developed as yea; it includes 84 Semet-Solvay, 60 Miike type of Koppers, 77 horizontal retorts and about 260 beehives. The consumption of coke is headed by blast furnace working, which requires 104,000 tons, and the following come thereafter, viz : - Calcination……………‥22,000 tons. Domestic uses‥‥‥‥‥‥‥‥21,000 " Foundry………………‥4,000 " The use of coke for household purposes has been appreciably increased during these three past years, and most of it is supplied from the gas companies. The Hokkaido coal such as is mined in Yubari, Sorachi and Tannai, has strong coking properties but possesses high volatiles and produces fingery coke when carbonised alone. It is therefore used mostly blended with Saghalien coal to produced a compact and hard coke. The Nippon Steel Works situated near Muroran, is the largest among the coking plants in Hokkaido, where about 130,000 tons, i.e., 75% of the total, are produced by 60 ovens of the Miike type of Koppers chamber (see Fuel, 1928, 187), The washed coal slime, containing 33% of water, is successfully dewatered by a Hoyl centrifugal dryer, using brushes inside or mixing lump coal with slime. In this plant, benzol is recovered from coke oven gas by scrubbing with creosote oil, which is obtained by distilling tar in a Raschig still. The benzol yield is very high owing to the careful control of the gas temperature, and also to the selection of a suitable wash oil. The author gives much practical data on the coke manufacture with Hokkaido coal, and also detailed explanations on the working of the Raschig continuous tar still which is the only plant in the Orient of its kind.