Boiler Fuel Oil

a fuel used in stationary boiler installations, on oceangoing and river ships, and in industrial furnaces of various types. Boiler fuel oils may be classified according to their raw materials as petroleum oils, which are produced from petroleum residue; shale oils, which consist of tars from the semicoking of shale; and coal oils, which are heavy fractions of tars from the semicoking of coal. The fuel oils are distinguished according to their viscosity, sulfur content, ash content, solidification temperature, and heat of combustion.

Petroleum oils, which are classified according to sulfur content as low-sulfur (0.5 percent), sulfurous (2 percent), and high-sulfur (up to 3.5 percent), account for the majority of fuel oils. Low sulfur content is particularly important for fuels used in industrial furnaces (for example, open-hearth furnaces). The advantages of fuel oil as compared with solid fuels are a higher heat of combustion (37—42 megajoules per kg, or 9,000–10,000 kilocalories per kg), the convenience of transportation and storage, the simplicity of supplying fuel to the firebox, and the precise regulation of the thermal operating conditions of the equipment. In this regard boiler fuel is inferior only to gaseous fuels.