Modern Gasworks Practice

THE PRELIMINARY PURIFICATION OF COAL GAS 531 TWO SCRUBBERS IN SERIES ft. 100,000 cubic feet . . . . . .5 in. 0 ft. in. 30 0 each 200,000 „ „ . . 6 0 35 0 serubber 300,000 „ „ . . 7 0 40 0 of these 500,000 „ „ . . 9 0 40 0 dimensions. 1,000,000 „ „ . . 12 0 45 0 1,500,000 „ „ . . 14 0 50 0 It will be noticed that for the smaller serubbers the ratio of diameter to lieight is very much greater th.an is the case with. the larger capacity vessels. In the case of single serubbers it will be seen. that works making up to 300,000 cubic feet per diem have only been considered, as it is inconceivable that larger concerns than this would be provided with one serubber alone. The same remarks apply to the two serubbers, where the limit has been placed at million cubic feet per day. It cannot be urged too strongly that the process of condensation should be carried out in an adequate and scientific manner. Effective condensation means an enormous reduction in the requisite serubber capacity. amount of water required No hard and fast rule can be laid down in connection with the amount of water necessary to remove completely the ammonia from the gas. Much, must depend on the amount of this compound present, and on the proportion of it which is elimin-ated and thrown down. in the virgin liquor of the condensers, etc. It has been stated that, theoretically, the whole of the ammonia may be removed by admit-ting 3 gallons of water per ton of coal carbonized, but in practice such a result is never attained. In the ordinary way, the whole of the water employeel is admitted to the final or clear-water serubber, and in normal cases this amounts to 10 to 13 gallons per ton of coal carbonized. Much, however, depends upon the type of serubber in use, coke Alling requiring a greater quantity of water than is the case with board Alling. Much variation is shown. in the direction of water con-sumption, and the author can point to cases where, with no other washing appara-tus but serubbers in use, the quantity admitted amounts to only 4 gallons per ton of coal. The horizontal washer-serubber does not effeet any marked economy in water, and in most cases requires an amount equal to about 10 gallons per ton of coal. Vertical washer-serubbers of the centrifugal type are, however, very much more efficient in this respect, and a small quantity of water, admitted at the top, will, if desired, remove the whole of the ammonia. At Salisbury it was found that with clean water admitted to a vertical machine at the rate of 3J- gallons per ton of coal carbonized 90 per cent, of the ammonia present in the gas at the inlet was retained, wliilst the water passed off as a 16 oz. liquor. Thos. Glo ver has given figures for the quantity of liquor which should be distributed in serubbers in order that tliese vessels may perform tlieir work most efficiently. He states that the liquor distributed per square foot of cross-sectional area of the serubber should be 0-145 gallons per minute. This is less the clean water addeel to the final serubber.