The catalytic gasification of carbon in incinerator fly ash

The formation of dioxins in combustion systems

“…The results of Vogg et al [110] are indicative of the behaviour of the reaction carbon with O 2 . The order of this reaction with respect to oxygen has been found to be 0.54 for carbon burnoff from a flyash [65], which is similar to the value of 0.5 found for petroleum coke and 0.7 for a coal ash. After testing three flyashes with 18 O 2 in the gas, Wilhelm et al [81] found that some were better at incorporating this 18 O than others, for which the 16 O oxygen came from the ash.…”

“…The mean order of reaction of oxygen with carbon was 0.54. Milligan and Altwicker [65] found that the activation energy fell with time when burning activated carbon and carbon black in similar tests, but this did not occur with any of the carbon from MSW ash. The ashes were far more reactive than a coal ash tested at the same time, and the ratio of CO 2 to CO in the product gas was of the order of 10 rather than 2.…”

“…The carbon content of a MSW flyash from a well-operated incinerator is usually in the range of 2 to 5% by mass. Those ashes used by Milligan and Altwicker [65] to measure oxidation kinetics contained 1.9, 2.0, and 7.4% carbon, and those by Hell et al [66] 1.75 and 4.2%. The total organic carbon contents of two MSW flyashes are reported as 2080 and 1830 ppm or µg g −1 [67].…”

“…The results from a test program on a mixed feed under controlled conditions undertaken by Marklund's group at Umeå university provide some of the most comprehensive data available [56][57][58][59][60][61][62][63][64][65][66][67][68]. The tests involved burning 5 kg h −1 of artificial MSW in a pilot-scale fluidised bed.…”

“…The carbons present in three flyash samples taken from MSW precipitators were burned by Milligan and Altwicker [65] in a stream of 10 mol% oxygen. The oxidation rate fell only slightly over a time of 30 min, and after 1 min of burning at 300 • C was 0.00012 g g −1 s −1 .…”