Properties of Some Kinds of Slurry Fuels and Their Combustion Behavior

Abstract

Some kinds of slurry fuels, which are comprising about 70% coal, oil pitch, vacuum residue (asphalt) or biomass such as wood chips, and about 30% water containing small amount of chemicals. were investigated in terms of fuel properties and combustion characteristics. Those slurry fuels have wide particle size distribution of sub-micron to 500μm, heating values of 20000 to 28000 kJ/kg, viscosities of 200 to 800 mPa·s@20°C and sulfur of 0.1 to 4wt%, depending on properties of raw feedstocks. From combustion tests using the pilot scale combustion furnace, steady flame and good combustion were observed for coal water mixture (CWM) and asphalt-residue water mixture (As-RWM), on the other hand, a few sparkles and long period combustion of char were observed for pitch-residue water mixture (Pi-RWM). Such different combustion characteristics, depending on slurry oils, were elucidated in terms of microexplosion, combustion characteristic times, and thermal decomposition by the combustion of a single droplet in the electrically heated furnace and the thermo-gravimetric analysis (TG/DTA). In order to obtain fundamental data in prediction of practical furnace combustion for biomass slurry fuel (BSF), the combustion behavior of BSF droplets was obsrved in the electric furnace and its combustion characteristics time was discussed in comparison with those of CWM, As-RWM, and Pi-RWM.