Document 93ma0v8wDEMYGke5zvN83aJ9L

302 CHAPTER 16 1948 Guide '/ . Fuels and Combustion Table 5. Approximate Gravity and Calorific Value of Standard Grades of Fuel Oil COMMERCIAL Standard No. i 2 ,3 5 6 Approximate Gbavttt Range A.P.I. 38-40 34-36 28-32 18-22 14-16 Calorific Value PBtu sr Gallon 136,000 138,500 141,000 148,500 152,000 303 .T a b l e 4. D e t a il e d R e q u ir e m e n ts for F u e l O il s ' CLASSIFICATION OF FUEL OILS Fuel oils are produced by distillation from crude petroleum after gasoline, naphtha, and other lighter products have been removed. Fuel oil is composed chemically of about 85 per cent carbon and 12^ per cent hydrogen with small amounts of oxygen, nitrogen, and sulfur. Oils are classified according to their specific gravity, but specific gravity alone is not a sufficient index of the properties that are important for heating purposes. Other characteristics that must be considered in the choice of a fuel oil are the flash point, pour point, water and sediment content, carbon residue, ash, sulfur content, distillation temperatures, and viscosity. The flash point and distillation characteristics are important relative to easy ignition and complete gasification of the oil in a burner. A low pour point and low water content are of interest in connection with the storage of the fuel in outdoor tanks, while a low viscosity permits easy passage through a small orifice. The sediment, carbon residue, and ash content should be low to prevent clogging of strainers and accumulation of unburned material in the burner. The sulfur content may be of im-; portance because of the corrosive effect of sulfur compounds in the burner and heating appliance or in special commercial processes. The Commercial Standard Specifications for Fuel Oils (CS 12-40) of the U. S. Department of Commerce are given in Table 4. These speci fications conform to American Society for Testing Materials Tentative Specifications for Fuel Oils D 396-38T. . The relationship between the A.P.I. gravity of fuel oils and their calorific value is given in Table 5. Fuel oil grades No. 1, No. 2 and No. 3 only are used in domestic heating equipment. Grades No. 5 and No. 6 are used in commercial and industrial burners and usually require pre heating. CLASSIFICATION OF GAS Gas is broadly classified as being either natural or manufactured. Natural gas is a mechanical mixture of several combustible and inert gases rather than a chemical compound. Manufactured gas as dis tributed is usually a combination of certain proportions of gases produced by two or more processes. Representative properties of gaseous fuels commonly used in domestic heating are presented in Table 6. Natural gas is the richest of the gases and contains from 80 to 95 per cent methane, with small percentages of the other combustible hydrocarbons. In addition, it contains from 0.5 to 5.0 per cent of CO%, and from 1 to 12 or 14 per cent of nitrogen. The heat value varies from 1000 to 1200 Btu per cubic foot, the majority of natural gases averaging about 1000 Btu per cubic foot. Table 6 shows typical values for the