738
MODERN GASWORKS PRACTICE
COMPOSITION OF VäRIOUS GäSES
Coal Gas. Carburetted Water Gas. “ Blue ” Water Gas. Mond Gas. Suction Gas. Dowson Gas.
Hydrogen Per cent. 47 Per cent. 350 52-0 26-0 16-0 20-0
Carbon monoxide .... 7-75 32-0 38-0 15-0 34-0 24-0
Carbon dioxide 3-5 4-5 4-5 12-0 3 0 6-0
Methane 27-5 130 1-0 3-0 nil 10
Heavy hydrocarbons (CnHm). 3-5 100 nil nil nil nil
Nitrogen 10-5 5-3 4-3 44-0 47-0 49-0
Oxygen 0-25 0-2 0-2 — — —
Candle-power 13-5 18 nil nil nil nil
Calorific power gross. B.Th.U. per cubio foot .... 520 580 300 165 160 155
WATER-GAS TAR
The quantity of tar thrown down during the scrubbing and condensation of carburetted water gas will amoimt to from 12 to 16 gallons per 100 gallons of oil gasified. This tar is, unfortunately, a frequent source of trouble in two directions. First, the lighter tarry vesicles which are difficult to remove from the gas in the preliminary stages remain suspended therein and are eventually extracted as the
gas passes through, the oxide purifiers.
The tar, being deposited on the oxide, not only reduces its activity and gives rise to excessive back-pressure, but it renders the spent material of little commercial valne. Many mechanical devices have been em-ployed with a view to removing tlie suspended particles of tar before the gas arrives at tlie dry purification plant. One of these is the “ Hmri-cane ” trap shown in. Fig. 453, which. is fitted in a vertical main where the flow of gas is downwards. The apparatus consists of a cone, A,
having its apex against the flow of gas and its base formed into a ring plate, B, about 6 inches in depth. An annular space is formed. around tlie ring plate by fixing a second ring, C, mounted on a foundation plate, D, the otter end of which, E, forms another ring. A second cone, F, is suspended below the upper one, the diameter of this cone being some 3 inches less than that of the main. The
gas to be treated is obliged to pass through, the narrow annular space, wliere it is