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portance of well designed compressors. Exactly the same system is carried out in the ordinary water tube boiler (fig. 47b). This furnace is applicable to the many forms of water tube boiler. In this case the same grate cover of fire-brick is employed, but the bars are lowered considerably to provide room for the concave bridge, which is also split to admit air. The burner points somewhat down so as to strike on the brick floor at about half length, the flames curving round the bridge hollow.

In fig 47c is the setting arranged for a 500 h.p. Heine boiler, which was provided with the Hawley down draught furnace previous to oil being used. The illustration shows how the Hawley grate has been retained and covered with tiling on the middle section only. In this boiler are five fire doors and six atomizers, the middle door having two, and the others one each. The gases from the side furnaces pass between the bars or tubes of the Hawley grate and join the gases from the central section in the combustion chamber. The illustration shows the central section of the furnace.

It may be added here that for English practice the containers of oil pumping systems of fig. 48 type should be of boiler plate and not of cast iron—a material, the use of which for pressure work, and especially for pressure work with liquid fuel, is considered indefensible, and would probably not be passed as safe by the English Boiler Insurance Companies.

Chapter XXI

AMERICAN STATIONARY PRACTICE WITH LIQUID FUEL—(continued). The Kirkwood System.

ATE, JONES & Co., of Pittsburg, make the Kirkwood burner, for which they

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claim that it can be worked by air or steam, does not clog, is easily

and is regulated at the point of combustion. A graduated scale for both oil and steam or air is fitted. Oil is pumped through a coil in the exhaust chamber of the oil pump itself, which is in duplicate.

It is claimed that oil with a fire test of 180°F. to 200°F. (82°C. to 93°) is as safe as coal, which will sometimes ignite spontaneously, that at 250° to 300°F. a red hot poker will not ignite oil stirred by it, nor will hot coals do so if thrown into it. This may all be true, but yet does not of course justify other than great care in regard to the dangers inseparable from any self flowing oil.

Steam is considered the best atomizing agent, but this claim is supported by the now exploded error that it assists the fuel value of oil by itself burning after dissociation.

It is correct, however, to call for superheated steam as more effective than less dry steam, and it need not be disputed that there may be a chemical action which promotes the combustion of hydrocarbons in the presence of moisture, as claimed by Professor Dixon; but this must not be confused with the erroneous claim that steam, being split up, acts as fuel and gives out more heat energy than it absorbed in the process of decomposition.

Professor Deniche, of the University of California, who tested oil at the Western Sugar Refinery in San Francisco, where 700 barrels of oil are used daily, states that there are 32 boilers, of which 22 are 6 feet 6 inches diameter by 21 feet long, and have 27 square feet of grate surface. Each boiler has 113 three inch tubes, giving 688 square feet of heating surface. The ten other boilers are 6 feet 6 inches in diameter by 26 feet long, have the same grate surface and 96 24 inch tubes, giving a heating surface of 1,098 square feet. The plant is rated at 2,540 horse power. but 4,340 horse power is obtained. There are also three Green economizers, which heat the feed water-two with 432 pipes and one of 360 pipes.

When coal was burned, forced draught was supplied by a 4 by 6 foot Sturtevant blower, driven by 11 inch x 16 inch engine.

The oil is received in tank cars containing from 6,000 to 6,500 gallons. The contract price for the oil is $1.30 per barrel, delivered (42 gallons per barrel, weighing 301-33 pounds) = 5s. 6d. per 35 imp. gallons.

"Seven cars are coupled to pipes along the track and the oil flows by gravity to a centrifugal pump, driven by an electrical motor, which pumps the oil into closed steel storage tanks of 10,000 barrels each. These tanks are surrounded by a con

crete dam, the space enclosed containing a little more than the contents of one tank. From these main tanks the oil flows by gravity to a small underground tank near the fire room. A network of fire-brick set on edge is laid directly upon the grate bars, and against this the oil flame is directed. This network can be removed and a coal fire started within twenty minutes, by actual practical trial. When oil was first used it was blown with two or three per cent. of generated steam, but this gave an imperfect flame and set up a vibration. Now eight per cent. is used, and a Bunsen flame is obtained with little vibration."

The fire-room cost of handling the fuel is stated to be less than one-third of that of coal.

When coal was used as fuel, twenty-six firemen were employed; now twelve are needed.

When coal was used careful tests were made, and from the results obtained there has been prepared the following table, which shows a saving of $46,012-15 per year by burning oil. But as it was based on the first test made under poor conditions, since remedied, it is claimed that the minimum saving over coal is $60,000. This does not take into account wear and tear on the boilers and general convenience. Statement of Comparative Value of Oil and Coal.

BASED ON THE FIRST TRIAL TEST. COAL BASIS OF 1897.

Total bituminous coal received during 1897, tons
Average evaporation of that coal from and at 212°F., pounds
Total water evaporated on that basis, pounds

35,347

7.88

Fire room cost of handling that coal, reckoning 300 days at $64-26 Cost of coal for this work on basis of present price, 35,347 tons at $6.55 (have paid as high as $7.25 this month).

624,183,481
$19,278-00

$231,522-85

Total cost of evaporating above quantity of water, coal.

$250,800-85

OIL, BASIS OF $1.30 PER BARREL, AND 13·9 POUNDS EVAPORATION.

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Saving on year's work by burning oil under the above conditions.

$46,012-15

Tate, Jones & Co. give the following working figures for Beaumont oil—

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Theoretical calorific value of Beaumont oil, I lb. will evaporate 15 lb. water.
Calorific value of ordinary Western coal, 1 lb. will evaporate 15 lb. water.
From which it appears, 48 lb. oil will evaporate as much as 100 lb. coal.

They also consider that there should be from 6 to 7 per cent. of oxygen in the

LIQUID FUEL AND ITS COMBUSTION

furnace gases. As with most American systems, the Kirkwood system embodies a heater and pumps. The heater consists of a steam chamber, the steam chamber containing a pipe coil through which the oil passes before reaching the burner, the coil being heated by the waste steam from the pumps. These pumps are in duplicate, so that one may always be in reserve in case of breakdown. The relief valves in the pressure chamber are designed to keep the oil in it and in the supply lines at a uniform pressure of about 20 pounds or more, an automatic by-pass allowing any surplus oil to return to the storage tanks without rise of temperature.

By applying the oil itself both hot and under pressure it is compelled to be admitted through finer orifices and in a more thin and divided state for atomization. The oil must not appear visible as a dark stream at the burner tip, but as an almost imperceptible spray.

The Aerated Fuel Process.

This process is that of the Gilbert and Barker Manufacturing Company of New York, and is simply a system of atomizing by compressed air. The system is used in all manner of industrial arts, the flame being used direct in metal work. glass making, japanning, etc. The apparatus includes an air compressor, oil pump and receiver, storage tank and the burners and necessary pipes.

Compression is to 15 pounds per square inch, a pressure below which it is stated that the fuel is not perfectly atomized.

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The oil pump is itself worked by the air, and serves to keep a full receiver of bout 30 gallons capacity (25 imperial gallons). The receiver also contains compressed air which forces the oil to the burner (fig. 50), where it meets the air coming lirect from the compressor. Valves regulate the proportions and the air pressure preserves even working conditions, whether two or twenty burners are at work. It is claimed that the combustion is really gaseous, clean and smokeless. The main supply is a buried tank outside the building and away from the burners. The oil pump is automatically regulated by a float, and all apparatus is below the burners, so that no gravity flow can take place. The use of gravity is held by some to be bad practice, and this view will bear argument in its favour. Low pressure air is specially condemned as leading to imperfect atomization and large globules, which burn imperfectly and deposit carbon and injure the fire-brick. From 60 to 120 gallons of oil are claimed to do the work of a ton of coal.

The process is held to be very much superior to any steam atomizing process for metallurgical work.

Low pressure air which throws oil upon the fire-brick unconsumed, causes these to shell off and break, and smoke is made also while carbon is deposited in the furnace.

Applied to metallurgy, to forge furnaces, crucible heating, and other industrial work outside steam raising, the advantages of oil fuel are set out, in regard, not merely to the absence of dirt and dust, but that there is no loss of time through men waiting for fires to burn up. There are no times of good or of bad fires, no uneven heat, but a full flowing flame is maintained with an even continuous degree of heat. Then the economy of oil is largely secured by increased production and better work. Oil has the advantage over gas fuel also, which, though equally good in the furnace, cannot be produced without labour and dust and at a considerable outlay in plant and apparatus.

A usual computation of the calorific capacity of various gases is as per following

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Since a gallon of fuel oil (7 pounds) contains 151,000 heat units, the following comparisons may evidently be made. At three cents a gallon (about 1·8d. per English gallon), for instance, the equivalent heat units in oil would be equal to

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