A close inspection of the various types of oil burn ers illustrated, will show clearly that it is necessary to heat the oil in order to properly atomize it. Ex periments have proven that fuel oil will not burn in a solid mass, but that it must be broken into minute particles by heat and mechanical action, and then im mediately exposed to air.
Heating the, oil lowers its viscosity, with the re sult that any suspended water more readily separates out.
A temperature of about 125 degrees has been found to produce the best results. When oil is heated above the flash, point, trouble occurs. The carbon will precipitate and settle in the pipe lines and at the burner tip. There is also a danger of explosion, if there are any leaks in the oil line. When the oil is heated before reaching the burner, less air or steam will be required to atomize it. This is an important point, for it has been proven in practice that burners require at least 3 per cent for perfect atomization, and many burners are in practice using from 5 to 10 per cent.
Air pressures as low as 10 ounces are at pres ent being used with excellent results under especially constructed furnaces.
Compressed air has been found more economical than steam as an atomizing agent in brick, lime and cement plants, where the units are a long distance apart.
In many cases the cost of installing and operating an electrically driven air compressor is much less than that of installing and operating steam boilers. The losses due to condensation are also avoided.
Many plants are fitted with burners thatsfiave to be forced to get sufficient steam from the boilers. This is bad practice, for when a burner is forced, ex cessive amounts of steam are required for atomizing.
Incomplete combustion and high stack temperatures, with their attendant losses, are bound to occur, and by forcing the burner and centralizing the heat, tubes and sheets may be blistered.
For all these reasons, the greatest economy can only be secured by installing an ample number of burners to supply all the fuel needed by the furnaces without forcing.