COMBUSTION CHARACTERISTICS OF HEAVY OIL-WATER EMULSIONS

The combustion of heavy oil and its emulsions with water was investiga ted in experiments on a semiindustrial scale. Two comparisons between heavy oil and oil-water emulsion flames are presented that, due to the different initial conditions of the spray, provide complementary info rmation. Reported results include spatial distributions in the flame o f temperature and species concentrations (O-2, CO, UHC, NOx) as well a s gaseous and solid emissions in the flue gases. The measurements insi de the emulsion flame display a remarkable improvement in the combusti on process with respect to that of the neat oil with poor atomization; differences are much less important if a fine spray is achieved with the heavy oil. Solid emissions are significantly reduced in the emulsi on tests and the morphology of the particle samples demonstrates the f ragmentation of the drops and/or the coke particles initially formed. The flame temperatures are reduced by similar to 65 K. The heal absorb ed by the water injected in the emulsion and enhanced radiative heat t ransfer due to the higher particle number density could explain this d ifference. The spatial distribution of NO, indicates that a significan t reduction is obtained in the final part of the flame; this may be at tributed to a decrease in the rate of thermal-NO formation as a conseq uence of lower gas temperatures. No measurable difference in NOx conce ntration is found in the inner core of the flames. Copyright (C) 1996 Elsevier Science Ltd.