Evaluation of carbon black slurries as clean burning fuels

Abstract

Experiments were performed to examine the pumpability, atomization and combustion characteristics of slurries made of mixtures of carbon black with No. 2 fuel oil and methanol. Carbon black-No. 2 fuel oil and carbon black-methanol slurries, with carbon black contents of up to 50 and 45 wt%, respectively, were pumped and atomized by means of a peristaltic pump and air atomizing scheme, and burned in an 82 kW laboratory combustor. Measurements of slurry spray droplet size distributions indicated mean droplet diameters of approximately 100 and 30 μm for the carbon black-No. 2 fuel oil and carbon black-methanol mixtures, respectively. Particulate emissions from the combustion of slurries containing 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 paniculate emissions are significantly higher than corresponding emissions from ‘base case’ No. 2 fuel oil and methanol tests (0.75 and 0 mg dm −3, respectively). However, in spite of the increased particulate emissions, carbon monoxide emissions from all tests were similar (less than 50 ppm dry, corrected to 0% oxygen, for furnace stoichiometric ratios of 1.05 or greater). In addition, at 20% excess air, nitric oxide emissions from the combustion of the carbon black-No. 2 fuel oil and carbon black-methanol (approximately 50 and 15 ppm, respectively) were approximately half of those measured from the combustion of No. 2 fuel oil and methanol (105 and 30 ppm, respectively). Although not examined here, the use of dispersants, stabilizers and modifications to the atomization equipment could improve the burning characteristics of carbon black slurries.