Chapter XVII

LIQUID FUEL APPLICATION TO STATIONARY AND OTHER BOILERS (HOLDEN'S SYSTEM)

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The Lancashire Boiler.

S already suggested, oil fuel can be best utilized under steam boilers by injecting it in spray form into the furnace by a steam jet or jets. Here perfect combustion can be secured by the proper admission of air and the intervention of a highly heated fire-brick bridge or screen. The furnace can be arranged to burn oil fuel above the ordinary grate, or preferably along the usual level of the firebars, so that the whole of the cubical contents of the furnace can be secured for combustion.

Fig. 29 shows the arrangement of the oil-fuel apparatus with Holden's Burners on a Lancashire boiler. The burners are placed at the front of the brick lined extensions, to which heated air is conveyed from large tubes passing down the outer flues. The fire-brick construction is simple and easily introduced for an ordinary sized boiler with a grate of, say, 7 feet long. A striking bridge pillar with inclined face is built up about 2 feet 6 inches inside the furnace; next, a screen with large clear opening about 1 foot 6 inches behind the former; and finally, a second screen with oblique perforations to direct the gases along the inner surface of the flue. The central portion of this last screen is recommended to be built solid. On boilers thus arranged, with fair working conditions, an evaporation of from 14 to 15 pounds of water per pound of Texas fuel oil (from and at 212°F.) is readily obtained.

On a large boiler of this type burning north country "smalls" and evaporating only 6.5 pounds of water per pound of coal, the Texas fuel oil has secured an evaporation of 15-25 pounds of water per pound of fuel.

The Cornish Boiler.

In fig. 30 a Cornish boiler is shown with liquid fuel and the fire-bars are left in and covered by a layer of fire-brick or chalk as a base for the fire in case it may be necessary to return to solid fuel at any time. Any internally fired boiler may be treated by either method. Where the bars are left in there ought to be a damper fitted to the opening of the ash pit to regulate the admission of air.

In these furnaces the injector is placed about 8 or 10 inches above the grate surface and about inch above the centre of the 4-inch opening cut through the furnace door. The injector is inclined so as to point to the second or third brick from the top of the bridge. Dry steam, preferably superheated, is admitted by a

SILAM

Generally, as regards the firing of internal furnace boilers, the fuel is blown in on a line about parallel with the grate surface and 8 to 10 inches above it, as

valve C1, the cock C2 being to clear the fuel pipe and injector when choked, and the pipe C being for steam to warm the oil in the tank.

shown in the illustration of the Cornish furnace and also in fig. 31 of the stationary form of the locomotive type boiler.

In the vertical boiler of large size the atomizer is usually placed below the

In either case the opposite half circle of the furnace must be lined with fire

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fire-door opening, but in small vertical boilers it must be placed through the door.

brick to the height of about half the furnace diameter to form the necessary incandescent surface on which any unburned oil can strike.

The Water Tube Boiler.

Fig. 32 shows an arrangement of oil burners for a water tube boiler where liquid fuel is intended to be used in conjunction with coal, so that while working

Fig. 32. WATER TUBE BOILER FOR COAL AND OIL BURNING. HOLDEN'S COMBINED SYSTEM WITH GRATE

at full power the evaporation of the boiler may be somewhat increased, by starting the liquid fuel burners, and when the fires become dirty the maximum power can still be maintained by increasing the consumption of the liquid fuel as the fires get dull. Here the steam passes through the superheating coil in the uptake, and from there passes to a stand pipe, called usually the "steam branch pipe," from which small branches are led to each burner and the supply is controlled by five small valves on the steam branch pipe.

For the water tube boiler without grate bars the arrangement of fig. 33 is em