INVERTED WEIR 45 N Furnace. Fig. 27 Lyswa Furnace. Fig. 28 Dimensions of Hearth ............ 16X2. 1 =33 m2 6 13X2 =26 rn2 Production per 24 hours . . ..... f 3,800 pouds 2,900 pouds Per sous/re meter I 62,300 kg 1,860 kg 47,400 kg 1 850 kg Coal consumed per 24 hours f 800 pouds 409 pouds -J Coal consumed per second . ... I 13,000 kg 0 kg 154 6,700 kg 0 kg 079 Ratio between weight of coal and weight of ingots .......... 21.1 per cent 16 8 per cent Gas volume per kilogram of coal burned with 50 per cent excess air supply ........ 14 m3 04 9 m3 89 Gas, volume burned per second reduced to 0° Qo = 2m3 16 Qo — 0 m3 78 Gas, volume burned per second at / = 1200° . ....... Q1200 = 4 m3 2 Height of roof above hearth at the right of the strangulation, computed by Yesmann's formula for a temperature of 1200° ......... hizooo ~ 0 m 530 Effective height ..... . .......... 0 m ffgff Gas, volume per second at t = 700° . Height of roof at chimney or waste gas opening by Yesmann's formula £ = 700° Q7oo = 7m3697 /J,7QO = () ft). 01 Q700 = 2m3780 &7oo — Om 479 Effective heieht ................. tnm-0 m,90 h™ — 0 m 850 " N " works. To what may this greater fuel consumption be attributed. Evidently to the greater height between the roof and the hearth of these furnaces. Why was it found necessary at the " N " works to raise the roof to a certain height above the hearth, while at the Lyswa works it was found necessary to lower the roof to accomplish the same result? An examination of the design of the " N" furnace (Fig. 27) leads to a negative conclusion. Indeed, according to Yesmann's formula a furnace will require less combustible wb^n the roof is closest to the hearth. Accordingly the roof should be brought down as low as possible. The hot gases consist of a mixture of air, combustible gases and the products of their reaction upon each other. The combustion takes place while the hot gafces are passing through the furnace; C1) The quality of the coal is not considered in this computation.