HIGH TEMPERATURE CARBONIZATION OF COAL 387
instructive, in that, with. the present tendency towards mass carbonization in gas-works, they probably approach, more nearly the actual state of affairs. Short’s researches show the following distribution :—
Nitrogen in coke ..... . 43-3 per cent.
» 99 tar ..... . 3-0 ?»
„ „ ammonia .... . 15-2 99
„ „ cyanogen .... 1-4 99
Free nitrogen in gas .... . 37-1 99
F. Sommer 1 states that the maximum yield of ammonia is obtained between 800° and 900° C., and shows the distribution of nitrogen at this temperature to be as follows :—
Westphalian coal. Silesian coal.
Best distillation temperature, ° C Nitrogen in dry ash from coal „ „ ammonia „ „ hydrocyanic acid „ „ tar „ „ coke . „ „ gas (by difference) 800 to 850 1-896 per cent. 17-85 0-47 1’63 72-23 6-82 „ 900 1-5485 per cent. 19-19 1-05 2-66 60-32 16-78
In recent tests with a moderate quality coal in continuous vertical retorts the Gas Investigation Committee 2, has given the following figures for the distribution of nitrogen:—
Coal charge unsteamed. Steaming at 32*7 per cent.
Nitrogen in coke >, „ tar » „ liquor (as NH3) » „ „ (as cyanide) » „ gas and lost 99 „ „as cyanogen 60-1 per cent. 6’8 „ 17-9 1-5 „ 13-2 „ 0’5 „ 49-7 per cent. 8’9 „ 19-5 1-1 „ 20-0 0-8 „
In all cases the results conclusively show that by far the greater proportion of nitrogen remains behind in the coke; but with the prolonged periods and high temperatures of modem distillation methods the proportion, remaining in th.e solid residue is undoubtedly far less than was the case some few years ago. The effect of a long-sustained heat such, as exists with the present-day 12-hour charge was shown by Watson Smith, to be conducive to the most complete expulsion of the nitrogen from
1 Stahl und Eisen, 1919, pp. 261, 294, 349. 2 Proc. Inst. Gas Eng., June, 1920.