530
MODERN GASWORKS PRACTICE
SCBUBBERS
When there is no other wet purification plant, a - generally recognized rule for the capacity of tower serubbers states that 9 cubic feet of volume should be allowed for every 1,000 cubic feet of gas passed per diem. For modern requirements, however, so great an allowance will in most cases prove unnecessary; but much depends upon the washing apparatus prior to the scrubbing plant. In the scrub-bers slow contact is desirable, so that the gas should be in contact with. the wetted surfaces for a period of from ten to fifteen minutes, as against about twenty seconds in the modern form of washer-scrubber. When associated with any form of meclianical washing apparatus 5 or 6 cubic feet of serubber capacity per 1,000 cubic feet of gas per diem should prove ampie. In some cases the gas issuing from the power-driven vessel is practically clevoid of ammonia, and is merely passed through a small tower serubber operated with clean. water and working as a catch vessel. Such a scheine, however, is not to be recommended, unless ampie safeguards are provided against the breakdown of the meclianical machine. Where no washer-serubbers are in use the capacity allowed should be as much as 10 cubic feet per 1,000 cubic feet of gas per diem. This includes both washer and serubber capacity in such cases where only board-filled washers and coke or board serubbers are employed, and may be apportioned half to the one type of vessel and half to the serubbers. When washers on the Livesey and such principles are introduced the serubber allowance need be no more than 6 cubic feet per 1,000 cubic feet of gas per diem. In very small works where one tower serubber alone, and no washer, is in operation, the allowance may wisely be inereased to 12 cubic feet.
The following are the sizes of serubbers which may be effeetively employed for the removal of ammonia where no other plant (i.e. washers) is in use for this purpose. In giving the actual size of serubbers this is the only case which can be readily dealt with, when no details of the washing apparatus are known.
Single Scrubbebs
Gas made per Day. SCRUBBER.
Diameter. Height.
ft. in. ft. in.
20,000 cubic feet 3 6 24 0
40,000 4 6 32 0
60,000 J? 6 0 36 0
80,000 5? • 6 0 35 0
100,000 ..... ..... 7 0 35 0
150,000 o. ......... 8 0 35 0
200,000 9 0 40 0
300,000 10 0 40 0