THE DRY PURIFICATION OF COAL GAS
a remedy; and if the box is made first “ taker,” the satur-ated gas coming away from the scrubbing plant will deposit its moisture on the material and the purifier cover, tilis in time percolating through the layers, with the desired results. On the other hånd, when gas is admitted to the bottom of the vessel, the water is merely de-posited in the box, and runs away through the seals. The top tier of oxide in a downward-current purifier is frequently found to be in a muddy condi-tion for a depth of two or three inches when the box is working as first “ taker.”
Fig. 352b.
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Fig. 352a.—Milboubne’s Valvb for Ur ob Down Flow.
A small point worthy of notice is that of revivification. When air is admitted to a box, it is the material at the bottom wliich (under the common system) derives the greatest benefit from this, and is, consequently, revivi-fied to a somewhat greater extent than the upper tiers. If alternate flow is provided for, liowever, the uppermost layers are able to de-rive full benefit from the oxygen present.
Reversal of current is, of course, not to be recommended in the case of oil gas purification.
Purifiers which are fitted for the travel of gas in the usual upward direction. may readily be modified so as to cause the gas to