EVALUATION OF CARBON-BLACK SLURRIES AS CLEAN BURNING FUELS

Experiments were performed to examine the pumpability, atomization and combustion characteristics of slurries made of mixtures of carbon bla ck with No. 2 fuel oil and methanol. Carbon black-No. 2 fuel oil and c arbon black-methanol slurries, with carbon black contents of up to 50 and 45 wt%, respectively, were pumped and atomized by means of a peris taltic pump and air atomizing scheme, and burned in an 82 kW laborator y combustor. Measurements of slurry spray droplet size distributions i ndicated mean droplet diameters of approximately 100 and 30 mu m for t he carbon black-No. 2 fuel oil and carbon black-methanol mixtures, res pectively. Particulate emissions from the combustion of slurries conta ining 47 wt% carbon black in No. 2 fuel oil and 42 wt% carbon black in methanol were approximately 40 and 28 mg dm(-3), respectively. These particulate emissions are significantly higher than corresponding emis sions from 'base case' No. 2 fuel oil and methanol tests (0.75 and 0 m g dm(-3), respectively). However, in spite of the increased particulat e emissions, carbon monoxide emissions from all tests were similar (le ss than 50 ppm dry, corrected to 0% oxygen, for furnace stoichiometric ratios of 1.05 or greater). In addition, at 20% excess air, nitric ox ide emissions from the combustion of the carbon black-No. 2 fuel oil a nd carbon black-methanol (approximately 50 and 15 ppm, respectively) w ere approximately half of those measured from the combustion of No. 2 fuel oil and methanol (105 and 30 ppm, respectively). Although not exa mined here, the use of dispersants, stabilizers and modifications to t he atomization equipment could improve the burning characteristics of carbon black slurries.