TAR FOR FIRING RETORTS.
The attention of gas engineers has been forcibly directed to the use of tar as a fuel for the firing of retorts, now that this once high-priced material is suffering, like everything else (but, perhaps, to a more marked extent), by what is called "depression in trade." In fact, it has in many places reached so low a commercial value that it is profitable to burn it as a fuel. Happily, this is not the case at Nottingham; and our interest in tar as a fuel is more experimental, in view of what may happen if a further fall in tar products sets in. I have abandoned the use of steam injection for our experimental tar fires in favor of another system. The steam injectors produce excellent heats, but are rather intermittent in their action, and the steam they require is a serious item, and not always available.
Tar being a pseudo liquid fuel, in arranging for its combustion one has to provide for the 20 to 25 per cent. of solid carbon which it contains, and which is deposited in the furnace as a kind of coke or breeze on the distillation of the volatile portions, which are much more easily consumed than the tar coke.