Modern Gasworks Practice

18 MODERN GASWORKS PRACTICE Stop-ended retorts, 9 feet to 10 feet long x 15 inches round. . 3,000-4,000 cubic feet. ” » 10 feet long x 16 inches round. . . . 4,000-5,500 ” » 10 feet ]ong x 21 inches x 15 inches Q | or 10 feet long x 22 inches x 16 inches q J ' ' 7’000-8,500 „ “ Through ” retorts, 20 feet long x 24 inches x 16 inches Q . . 18,000-20,000 „ „ Vertical retorts, Woodall-Duckham type . . . . . up to 80,000 „ ” „ Glover-West type ________________________up to 50,000 „ » » Intermittent type (5 metres long) .... 16.000 In the case of vertical retorts in particular th.e capacity per retort may be considerably augmented by judicious steaming of the charge. The figures given for these systems refer to straight coal gas only. __ Instead of speaking of the make per retort per diem, it is usual among gas engineers to work on a basis of “ make per moutlipiece ” per diem. This is particu-larly the case with horizontal and inclined retorts; thus the “ make per mouth-piece ” for a stop-ended retort would be 3,000 to 8,500 cubic feet, the same as the make per retort. For a “ through ” retort it varies from about 6,500 to 10,000 cubic feet, i.e. half the make per retort, this being due to the faet that the retort has two mouthpiecés—one at each end. Coal Storage It is customary, and it has been found advantageous, to pro vide for storage under cover sufficient for twenty-one maximum days’ production. In recent years, owing to the unsefrtled condition of the labour market, the larger Companies have (war conditions apart) endeavoured to store sufficient supplies for their needs for two or three months ; hence recourse has to be had to stacking large heaps out in the open. No undertaking can in normal times allord to risk three weeks’ storage, although this is still a common and sufficient allowance for that kept under cover. The calculation of the cubical capacity required for storing a definite quantity of coal may be.closely arrived at by assuming that 1 ton of average gas coal occupies 42 to 43 cubic feet of space. One ton of gas coke requires a space of about 85 cubic feet. Coal should not be stacked to a greater depth than 20 feet, owing to the danger of spontaneous combustion. (See page 371.) CONDENSEBS Owing to the many advantages attendant upon the use of water condensers, they are now frequently employed in preference to the original atmospheric type; the latter, however, are still used in small and medium-sized works, and are not without their good points. It should be remembered that the initial stages of condensation should be efiected slowly. There are several rules for the capacity of air condensers, and the variable nature of the results they give shows that engineers are by no means agreed on the subject. A common and reliable rule is the folio wing Allow 5 square feet of atmospheric condensing surface per 1,000 cubic feet of gas made per day (maximum day’s production to be taken). This area includes all pipe from the outlet of the hydraulic main to the outlet of the condenser, and permits _______________