434
MODERN GASWORKS PRACTICE
moreover, is subjected to a maximum temperature just before leaving the retort, so that a considerable proportion of the volatile matter is expelled from it. That this is desirable is shown by tests carried out by Davidson, who found that even “ well-burned-off ” coke will give off quite a large amount of gas. Taking an ordinary
Continuous System
I 'Early Stages
Later Stages
coke containing 1-97 per cent, of volatile matter, it was shown that oii further heating this would yield an additional quan-tity of gas equal to 2,900 cubic feet per ton of coke, the com-position of the gas being as follows:—
Hydrogen . . 86-8 per cent.
Methane . . 2-05 „
Carbon monoxide. 6-5 „
Carbon dioxide . 0-6 „
Nitrogen . . 4-05 „
Frø. 264.
Interjfftiitént System,
The temperatures prevail-ing in vertical retorts are now largely governed by the extent to which steaming is carried on. The following table 1 is extracted from actual read-ings taken at Uddingston gasworks with Glo ver-West retorts:—■
Fra. 265.
Temperatubes in Vertical Retort Settings (Degrees Centigrade)
No steaming. Steaming, 13-3 per cent. Steaming, 22*1 per cent. Steaming, 32-7 per cent. Steaming, 44-8 per cent.
Waste gas flues 876 902 964 910 930
Ciroulating flues—middle 1,089 951 1,095 1,081 1,065
„ „ —bottom 1,141 1,005 1,163 1,175 1,126
Combustion flues—top .... 1,180 — — 1,207 —
„ „ —bottom . 1,218 1,131 1,085 1,150 1,033
Secondary air flues—top 755 700 646 637 585
1 Proc. Inst. Gas Eng., June, 1920.