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MODERN GASWORKS PRACTICE
(1) There is no machinery to break down.
(2) The retorts are accessible at any time for repairs, etc.
(3) Wear and tear is less, as there are no contimiously working parts.
(4) Retorts are said to last longer, as no abrasion takes place by continuous movement of the coke.
THE WOODALL-DUCKHAM SYSTEM
This system, wliich, with the Glover-West, has made more headway tliaii any other type in this country, has undergone considerable modification since its intro-duction in 1903. Continuous charging and discharging was then arranged for ; the base of the retort was water-sealed, and the coke, after passing the extractor, was quenched in the seal and removed by means of a short length. of conveyor. Five years later the present system of coke extraction was introduced and the water-seal abolished. The amount of coal passing into the retort and the rate at which the charge descends are automatically governed by the speed of the coke extractor. The coal occupies from eight to ten hours in its passage through the retort, the speed depending upon the dass and character of the coal employed.
The retorts are about 25 feet in length and of rectangular tapered shape, the three sizes of 3, 5 and 7 tons per day capacity respectively varying practically only in the length of the major axis.
Below are given particulars of the three standard sizes of retorts :—
Size. No. 1. No. 2. No. 3.
Braadth and Width of
Retort. Top . 2 ft. JOi in. X 7 in. 4 ft. 3 in. X 7 in. 5 ft. in. X 7 in.
„ „ Bottom . 4 ft. 3 in. X 1 ft. 7 in. 5 ft. 3 in. X 1 ft. 7 in. 6 ft. 6 in. X 1 ft. 7 in.
Length .... Coal carbonized per 25 ft. 25 ft. 25 ft.
day (according to dass of coal in use). 2J to 3| tons 4J to 5J tons 6| to 7i tons
Average yield of gas per retort per day . Number of retorts in 30,000 to 40,000 cu. ft. 60,0C0 to 70,000 cu. ft. 80,000 to 90,000 cu. ft.
each setting Three to five Two or four One 1
Grate area of Pro- | Approxim ately 1 sq. ft. per ton of Coal
ducers .... carbonized per day
The taper of the retort is not uniformly from top to bottom, the greater part of the taper being confined to the upper ten feet where the maximum swelling of the coal takes place. The actual width of the retort on the minor axis increases from 7 inches at the mouthpiece to 1 foot 4 inch.es at a point 10 feet down. The
1 Each 7-ton retort is a self-contained unit.