THE PRELIMINARY PURIFICATION OF COAL GAS 515
types of washer-scrubber now in use, but in many cases a strong resemblan.ee is shown. Essentially, the machines consist of a series of cylindrical bays, made from cast-iron, and bolted together so as to form a number of compartments. A rotating shaft carrying some form of agitating gear runs through the centre of the cylinder. The erude gas entering at one end passes out at the further end of the cylinder deprived of the greater portion of its ammonia, while clean water (flow-ing in at the opposite end to the gas) travels from bay to bay, being converted into-a liquor of gradually inereasing strength. In the most effeetive machines, clean water running into the final bay will be worked up to a liquor of about 12 oz. strength by the time it reaclies the opposite end of the cylinder.
Fig. 319.—Kirkham, Hulett axii Chandmb’s “ Standard” Washbb-Scrubber.
Modern washer-serubbers may be classified into two distinet groups:—
(a) Horizontal types.
(&) Vertical centrifugal types.
Type (a) was introduced many years ago by Paddon, and although it is still very mueh in evidence on gasworks, there is some tendency for the more effeetive centrifugal type to take its place. Of type (a) the original machine of Kirkham, Hulett and Chandler (Fig. 319) is, perhaps, the best known. In its latest and im-proved form it consists of a number of concentric cast-iron rings bolted together and divided into separate compartments by means of circular division plates having openings in the centre to permit of the passage of the gas. The machine is con-structed in two sections with intermediate bearings at the centre, whilst a connecting main from section to section is provided for the passage of the gas. In the original machine the central shaft was carried on bearings inside the washing chambers, which rendered the bearings extremely difficult of access, and frequently resulted.