CHAPTER XIV
NAPHTHALENE IN COAL GAS
To the majority of gas engineers the naphthalene question. is still one of extreme importance, chiefly owing to the faet that no really definite solution of the trouble has yet been reached, while matters have not been improved by the modern practice of curtailing or eliminating altogether the oil formerly used with a fairly free hand for the carburation of water gas. It is enough. to say that modern methods of car-bonization have certainly tended to lessen. the trouble, but the whole problem stands on somewhat unsatisfactory ground—so much so that a method which is ■effective at one works may be absolutely useless at another.
The amount of naphthalene in coal gas varies considerably, in aceordan.ee with. the coal made use of and the system of carbonization employed. The following, however, may be taken as exemplifying the average quantities at the various stages of manufacture when horizontal retorts containing moderately full charges are in use and no special method of extraction. is employed :—
Inlet of condensers .... 60-80 grains per 100 cubic feet of gas.
Outlet ...... 20-25 „ „ „ „
Outlet of purifiers .... 8-15 „ „ „ „
On the other hand, tests on the gas stream coming from a system of intermitten* vertical retorts 1 have shown the following figures for naphthalene :—
Outlet of primary condenser . . . .9-9 grains per 100 cubio feet.
Outlet of Pelouze and Audouin condenser .7-5 „ „ „
Outlet of secondary condenser. . . 7-0 „ „ „
Outlet of washers ...... 3-5 „ „ „
District gas ....... 3-2 „ „ „
The results obtained from contimious vertical retorts are still lower, as is instanced by the figures obtained at the Droylesden works of the Manchester Corporation:—
Naphthalene in Purified Gas, Grains per 100 Cubic Fbet
Lancashire coal . . . . . . • . • • .2-77
Yorkshire coal ........... 1'98
Derbyshire coal . . . . . . ■ ■ ■ ■ .2-35
1 American Gas Institute News, Sept., 1917. 460