598 MODERN G AS WORKS PRACTICE
feet. A vessel of this description would be capable of dealing with about 2f million cubic feet per diem; consequently, in the case of those works making more than this quantity of gas, it is preferable to split the stream prior to reaching the purifiers and to treat it in two (or a number of) separate units.
An examination of the multitude of formulæ for calculating purifier capacity which have from time to time been suggested shows that in the past the variation in opinion has been remarkable. As an example, it is instructive to note the contra-dictory results which are obtained by working to the following selection of formulæ, all of which were more or less accepted at different periods in the history of gasmaking..
1. Clegg. Allow 1 square foot of purifier area per 3,600 cubic feet of gas per maximum day.
2. Hughes. Allow 1 square yard of sieve area per 1,000 cubic feet of gas per maximum day.
3. Colson. Allow 1 cubic foot internal content of purifier per 376 cubic feet of gas per day.
4. F. Livesey. Allow 1 square foot of area per 2,500 cubic feet of gas per diem.
5. Wyatt. Allow 33 cubic feet, or 50 square feet of area per ton of coal per diem.
6. L. T Wright. Where the Beckton method of eight vessels is employed, allow for eacli box an area of 0-4 square foot per 1,000 cubic feet of gas per day.
7. Reissner. Allow 1-17 square feet per box per 1,000 cubic feet of gas made per day.
8. French Rule. Bulk of oxide sliould be equivalent to one-twentieth of the volume of gas passed per liour.
American Rules
9. Earnshaw. Experiments were coaducted on small purifiers with. gas passed at 1,000 cubic feet per day per 0-4 square foot and 0-5 square foot of area.
In the latter case the efficiency of the oxide was 57 per cent, greater than with the former allowance.
10. E. S. Jones. Volume of oxide required =
Max. make of gas per hour X grains of H2S in gas
Xooo
A recent method of calculation which is employed in America is that known as the Steere formula, namely—
GXS
3,000 (D + C)'
Where A = cross-sectional area in square feet of the oxide bed in each box of a given set.
G = maximum make of gas per hour in. cubic feet.
S = a predetermined factor which is based upon the quantity of sulpliuretted hydrogen in the crude gas at inlet of purifiers.