716
MODERN GASWORKS PRACTICE
<£ down runs.” In this way the clinker is driven down towards the grate bars and will form in. larger pieces, which. may be more readily dealt with than can a number of small isolated lumps. A “ down run ” should be arranged for after every three orfour “runs” in theupwarddirection; butit isas wellto admitno topsteam for at least an hour betöre clinkering takes place. As regards purity of the material, it may be noted that retort carbon, makes an admirable fuel for water-gas manufacture, entirely obviating the tedious process of clinkering ; but its commercial value and the small quantities in which it is produced on gasworks preclude the possibility of its use. It must be remembered that the fuel-bed and the fireclay walls of the generator are the stores of heat, and the heat retained by them only is available for the reactions. Temperatures must therefore be maintained, the generator being worked up to at least 1,100° C. before the “ run ” is commenced. By the time the “ run ” is completed the temperature will have fallen to 850°-900°-C. The effect of this is shown by the männer in which the make of gas falls off towards the end of the “run,” with a gradual increase in tlie CO 2 content. Stelfox, experimenting with seven-minute and eight-minute “ runs,” forind the following results :—
1 Sevbn-Minute “Run.” Eight-Minute “ Run.”
■Gas made during Ist minute 1,882 cubic feet 1,840 cubic feet
j, 2nd 1,554 1,595
3rd 1,472 1,513
4th 1,472 1,308
<•> ” 5th 1,144 1,103
6th •••••• 982 941
7th 492 410
ff 8th 410
Total 8,998 cubic feet 9,120 cubic feet
As regards the rate of increase of the CO2 content, the author finds that, working under the conditions of a comparatively shallow fuel-bed as suggested above, the following may be taken as an average example with a six-minute “ run. ” :—
Generator Gas
Per cent. CO2. Per cent. CO.
End of Ist minute 2-8 46-1
„ 2nd 4-0 41-5
,, 3rd ,, 7-3 39-3
„ 4th 11-8 31-7
5th „ 14-7 29-4
„ 6th „ ... 15-9 27-3