FUELS.
As a general rule the major operating cost in the operation of steam locomotives is for fuel which to a considerable extent comprises different kinds of many grades. The kind of fuel used plays an important part in the pro portioning of the boiler and furnace and should Wood which has not been specially dried contains considerable moisture, generally be tween 20 and 40 per cent. It is advisable, therefore, to dry the wood and keep the same protected as it will absorb about 15 per cent of water when exposed to the atmosphere.
Comparative value of different kinds of wood for fuel are given in the following table: Fuel OIL—Fuel oil has been used to a limited extent and more especially in the ter ritory adjacent to oil wells. Where economic and commercial conditions permit it is the most desirable fuel. The absence of smoke and ashes, prompt kindling and extinguishing of fires, extreme rate of combustion and ease with which it can he handled and controlled are marked advantages in favor of fuel oil. The reduction in volume and weight over an equiva lent quantity of. coal for heating value and the increase in boiler efficiency are factors of no mean importance.
Crude oil consists mainly of hydrocarbons together with small quantities of nitrogen, oxygen, sulphur and water. The average com position by weight of typical American fuel oils is as follows: One barrel of crude oil contains 42 gallons and weighs from 310 to 350 pounds. Com pared with coal, oil occupies 50 per cent less that fuse together and become pasty on being heated. They are rich in hydrocarbons and arc used in gas manufacture. °Non-Coking Coals° do not fuse together during combus tion and are free burning. "Cannel Coals" are rich in carbon, burn readily and with a bright flame. It is very homogeneous, breaks without any definite line of fracture and has a dull, resinous lustre. It is a valuable gas coal and is used but to a small extent for steaming purposes.
The principle bituminous coals used are mined in Ohio, West Virginia, Pennsylvania and Illinois.
Powdered or Pulverized The value of powdered coal as a fuel for steaming pur poses has long been known. Despite the many advantages of powdered fuel, little progress has been made toward its general adoption.
Among the advantages obtained in burning powdered coal are: Complete combustion and total absence of smoke.
A cheaper grade of bituminous coal can be burned.
The locomotive boiler may be rapidly forced above its rated capacity. The labor of firing is reduced to a minimum. The constantly in creasing demand for the better grades of coal and oil throughout the country has brought about a condition where it is difficult to obtain such fuel at reasonable, prices. The yearly expenditure for fuel used in locomotives of the United States exceeds $300,000,000. The limited supply of oil should of necessity be con served for other purposes.
Investigations show that any fuel in a dry powdered state 663.5 per cent combustible is suitable for generating steam. Anthracite, bituminous and semi-bituminous coals, lignite, peat, anthracite culm, dust and slush slack, screenings and dust may all be burned in a pul verized state. They should all be in about the same condition as dry Portland cement.
The raw fuel is dried, pulverized and stored in fireproof containers. It is handled with the same care as fuel oil. For firing up a lo comotive the usual steam-blower is turned on in the stack, a piece of lighted waste is put through the firebox door opening and placed on the furnace floor, just ahead of the pri mary arch, after which the pressure blower and one of the feeders is started. Less than an hour is generally sufficient for getting a full head of steam. The powdered fuel., hav ing been supplied to the enclosed tank on the tender, gravitates to a helicoidal conveyor which conveys it to the feeders where it is commingled with air under pressure which forces the mixture through the connecting hose to the nozzles leading into the fuel and air mixers. Additional air is supplied in the mixers and the mixture is then drawn into the furnace by the flue draft and combustion takes place.
The maximum temperature is from 2500° to 2900° F. under the main arch. Liquid ash runs down the front and sides of the combus tion zone and is precipitated into self-cleaning slag pans where it is cooled and solidifies.
Many experiments are being conducted and various applications for burning powdered fuel are being tried out. Extensive developments