428
MODERN GASWORKS PRACTICE
As regards the effect of the size of nozzle and the pressure at which steam is supplied the folio wing figures (extracted from tests carried out at Uddingston gas-works) are instructive :—
Influence op Nozzlb Size and Steam Press ure on Results
Size of nozzle. Steam pressure (Ib.). Gas yield, cubic feet per ton of coal. Calorific power, B.Th.U. gross.
is-inch 5-6 9,870 560
^--inch 25-30 13,554 500-520
J-inch 25 15,487 506
|-inch 10-12 14,450 480-500
i-inch 25 17,500 430-450
Where steaming is employed considerable use will probably be found for the ■chart given in Fig. 261, which shows the quantity of steam (in Ib. per hour) which. is passed by different sized orifices at a number of different pressures. Again, an idea of the increased quantity of gas per ton of coal which may be expected. with. different types of coal (the straight gas yield of which is known) may be gathered by reference to the curves (specially prepared by Mr. John West), shown in Fig. 262.
The general effect of steaming, and the modifications resulting from the variation of the quantity of steam admitted, is well shown by the following series of figures which. have been. compiled from the series of five tests carried out at the Uddingston gas works by the Gas Investigation Committee.1
Table showing Effect of Varying Quantity of Steam Admitted
Test No. I. II. III. IV. V.
Diameter of nozzles (inoh) .... — ■fk TK tV TO
Steam .pressure at nozzles (Ib.) No steam Normal 5-16 10-02 15-20.
Steam, per cent, on coal used — 13-3 22-1. 32-7 44'8
■Gas made per ton of coal (cubic feet) . 9,367 12,666 15,222 17,814 19,593
Calorific power, B.Th.U. gross 544 482 447 436 410
Coke made per ton of coal (cwts.) . 11-90 11-54 11-13 10-55 10-34
Tar (dry) per ton of coal (galis.) 13-20 16-40 16-80 20-40 21-20
Liquor (10 oz.) per ton of coal (galis.) . 38-80 39-30 41-10 45-10 46-80
Sulphate per ton of coal, 24| per cent. (Ib.) 34-40 34-80 36-40 39-90 41-40
B.Th.U. per ton of coal (in millions) 5-096 6-105 6-804 7-767 8-033
Apart from the substantial increase obtained in British Thermal Units per ton of coal, the remarkable increase in the yield of tar and ammonia should be noted. This is no doubt due to the faet that secondary reactions are largely pre-vented from occurring, partly owing to the faet that the volatile products are rapidly
1 See Proc. Inst. Gas Eng., June, 1920.