HIGH TEMPERATURE CARBONIZATION OF CO AL 421
When a gas of the above-mentioned quality was distributed official requirements demanded that the illuminating power sliould not be lower than 14 candles. To-day, of course, the position has completely changed; and, with the passing of the illu-minating power standard, the highly enriched grade of water gas has completely disappeared. The majority of undertakings provided with. water gas plant now employ thern. very largely for the production of blue water gas or a semi-enriched gas (having a calorific power of from 380 to 420 B.Th.U.) in the manufacture of which from 0-75 to 1 gallon of oil per 1,000 cubic feet is used. Accordingly, the gas most commonly supplied to-day by all the larger undertakings consists of a mixture of from 75 to 80 per cent, of straight coal gas and 20 to 25 per cent, of blue water gas. In some instances the proportion of blue water gas is raised to 40 per cent, or more. The question of the production of water gas in situ by steaming the charge is discussed later.
Composition of Mixed Gas consisting oh 80 peb cent. Stbaight Coal Gas and 20 per cent. Blue Water Gas
Hydrogen
Methane
Unsaturated hydrocarbons
Carbon monoxide .
Carbon dioxide
Nitrogen
Oxygen....
Calculated calorific power
Per cent, by volume.
. 48-0
. 22-2
. 2-8
. 13-8
. 3-7)
. 9-3 [13-2
. 0-2 J
. 482 B.Th.U. gross.
The eflect of adding a further proportion of a combustible diluent (in this case blue water gas) is shown by the following analysis. It sliould be noted that wliereas as compared with the above analysis the calorific power is, of course, reduced, the actual proportion of inert constituents undergoes slight reduction.
Composition of Mixed Gas consisting of 70 per cent. Straight Coal Gas and 30 per cent. Blue Wateb Gas
T Per cent, by volume.
Hydrogen..............................................48-5
Methane ......... 19-5
Unsaturated hydrocarbons ...... 2-5
Carbon monoxide ........ 16-83 Carbon dioxide 3-80)
Nitrogen..............................................8-70'-12-67
Oxygen................................................047 )
Calculated calorific power ...... 458 B.Th.U. gross.
The composition of the saturated and unsaturated hydrocarbons in coal gas will necessarily vary in accordance with the coal carbonized and the method of carbonization adopted, as an instance of which måy be quoted the difference found in the case of the vertical retort (when paraffinoid characteristics prevail) and the horizontal retort which tends towards the production of benzenoid products.