Fuel Oil. Liquid fuel is chiefly crude petroleum and its residues. Shale oil, coal tars, wood tars and vegetable and animal oils are also used as fuel to a very limited extent. Petroleum as a fuel for use in steam or power plants has considerable variations. Its most distinctive chemical features are the practical absence of mineral matter, water and light gasoline and the presence of a large amount of hydrogen. Ordinarily when fuel oil is mentioned, reference is made to the residue from petroleum distillation, the gasoline and kerosene having first been removed. The chief properties making fuel oil available for use are the ease with which it flows, the low cost of handling and the absence of residue. Fuel oil has a remarkably constant heat of combustion. The heat of combustion in terms of B. T. U. per pound of oil is higher with lighter oils but is lower in B. T. U. per gallon with lighter oils, therefore it is obvious that the heavier oils are cheaper for fuel at the same price per gallon, which is the unit of measure ment. Ordinarily, fuel oil obtained from petroleum when dry and free from sediment has a very definite heating value in relation to gravity as is shown by the accompanying tables on page 318. The chief impurities found in fuel oil are water or brine and asphaltic sediment. The asphaltic sediment or tarry matter has almost as great heating value as the dry oil itself but the brine or water very greatly diminishes the heating value as well as interferes with the mechanical use of the oil. Fuel oil is ordinarily only used under conditions of its greater convenience than coal. In so far as the cost of heat obtained from fuel oil is concerned it is in most localities much higher than coal. The price of coal is the governing feature in the price of fuel oil. In general practice, three barrels of fuel oil are equivalent to one ton of coal screenings. The gravity varies according to the character of the oil and the amount of light constituents that have been distilled out of it. The following table shows typical gravities of fuel oil from different The viscosity of fuel oil is not proportional to the gravity as is indicated by the following tables: Viscosity and Gravity of Fuel Oils. (See Pages 313-4.) .12.6 530 272 88 Residuum from same after cracking. As compared with other sources of heat, the theoretical amount of heat obtainable from petroleum or fuel oil as determined when the combustion is complete and the absorption of heat is complete is as follows: The above is based upon the following: Fuel oil of specific gravity 0.900 25.7° Be', weight per gallon 7.5 lbs., weight per barrel 315 lbs. B. T. U. per lb. 19,225, per ton=38,450,000, per gallon= 144,200, cubic foot=1,078,500, per barrel=6,056,000. Slack coal 11,000 B. T. U. per pound. Theoretical Equivalents. 1 ton of coal-36 bbls. oil-24,500 cu. ft. of natural gas. 12.2 cu. ft. of natural gas. |