OCR Text |
Show ASH QUANTITY Other than oil being a liquid and coal being a solid, the major difference between the two is the quantity of ash they contain and its size. Residual oil rarely contains as much as 0.5 percent inorganic matter and more frequently contains only 0.1 percent. The contaminants are usually uniformly disseminated throughout the fuel as metallic, organic, oil-soluble compounds or submicron particulates. Bituminous coals, on the other hand, contain 10 to 20 percent ash. When occurring at the higher levels, this coal is frequently washed in jigs to reduce the ash level to 310 percent and increase the Btu content. The size of the ash varies from submicron particles to the largest size fraction to which the coal is crushed. The contaminants are heterogeneously distributed throughout the coal by size and gravity. On the average, the ash level in coal is at least 100 times that of oil. When expressed in terms of Btu content, the difference in levels is even more striking. The ash loading for a residual oil may be only 0.05 lb/106 Btu, whereas coal may have an ash loading of 7.7 lb/106 Btu, greatly increasing the potential for rapid ash accumulation on heat-transfer surfaces.1* OIL The principal ash-forming elements found in crude oil, as given by Bowden et al.2 in Table 1, are the same as those found in coal-with exception for the addition of vanadium, nickel, and zinc. Both inorganic and organic, metallic *Numbers designate references at the end of the paper. 1-4 |