514
MODERN GASWORKS PRACTICE
in their respective compartments, and are then exposed in their wet condition to the crude gas. Effec-tive contact with a large area of wetted surface is tlius ensured. Clean. water is ad-mitted to the top of the machine at the rate of 10 gallons per ton of coal carbonized, and flows out at the base as a liquor of from 16 to 22 oz. strength. The back-pressure thrown by the apparatus is ex-tremely small, amounting to little more than. 1 inch of water.
Mechanical Washer-SCKUBBERS
Plant of this de-scription has been introduced with. aview to combining the func-tions of the washers
Fig. 318.—Walkeb’s Pumfying Machine. and scrubbers. On
the majority of the larger works some apparatus of the kind is now to be found. The increased efficiency of ammonia extraction obtained is largely dependent upon the large area of freshly wetted surface with. which the gas is brought in contact, also the “ breaking-up ” efiect of the mechanically-operated portions. The primary objection to machines of this type is the necessity for employing motive power, whilst the introduction of limning parts accounts for some expenditure on wear and tear. At the same time, the capacity of the machines for dealing with a definite quantity of gas is considerably less than that necessary with the ordinary type of washing and scrubbing plant; tlius. when a large stream of gas is to be treated, substantial saving in Capital out-lay will be efiected by the employment of the washer-scrubber. There are several