Modern Gasworks Practice

VERTIC AL RETORTS AND CHAMBER O VENS 157 in detail. First, tlie retorts are elliptical in section instead of rectangular, and are built up bf concentric rings of silica, the top and bottom of the retorts being of hard burnt fireclay. The bottom portion of the retorts is in the regeneration chamber for the secondary air entering the combustion chamber. The passage of the gas will be readily understood from Fig. 82, an outlet being provided at the base of each coal-feeding hopper, wh.en.ce the gas is conducted by a 7-inch pipe to a dry main. Each outlet pipe is fitted with a valve, which is brought into use when a retort is out of action for scurfing purposes. Coke extraction is, of course, contimious, and governs tlie rate at which the coal is delivered. The extractor consists of a slowly revolving vertical worm, driven by gas or electric motor of 3 h.p. for an installation not exceeding twenty retorts, 4| h.p. for an installation of six settings or forty-éight retorts, and 5 h.p. for an installation of ten settings or eighty retorts. The worm extractor, which. makes one revolution in about thirty to forty minutes, is made in two halves, so that it can be opened to perinit the retort to be readily in-spected. A novel feature enables the speed of the individual extractors to be regulated, so that if different types of coal are m use in the retorts, the speed of each. worm can be adjusted to suit the particular dass of coal. Dropping from the extractor the coke passes into the chamber fitted with a self-sealing lid (Fig- 81), all(J is remoyed from tilis at intervals of about two hours. The system of heating the retorts differs from that of Woodall and Duckham in that combustion takes place in a mim bor of chambers, and the waste gases (atter leaving the combustion chambers) pass around the upper portions of tlie retorts into horizontal circulating chambers before finding their way to the chimney. On account of tlie cooling action of the secondary air passing around the base of the retort, no water-quenching is necessary, and the coke is discharged from the lower chambers practically cold. The producers are charged up with this cold coke at intervals of about four hours. The more important details of the system are summarized below :— Type 1. Type 2. Type 3. Shape of retorts . Elliptical Elliptical Elliptical Breadth and width of 40 in. X 10 in. to 33 in. X 10 in. to 24 in. X 10 in. to retorts .... 46 in. X 18 in. 39 in. X 18 in. 30 in. X 18 in. Length of retorts 21 ft. 21 ft. 16 ft. Number of retorts in 8 8 8 each bed in units of 4 in units of 4 or 2 in units of 2 Coal throughout per retort per diem (when producing coal-gas) 4 tons 3 tons 2 tons Grate area (efiective) per producer 1,600 sq. in. 1,275 sq. in. 850 sq. in. The several types of retorts and settings designed to fulfil the requirement of both large and small installations.