Fly ash reactivity modified by nitrogen and sulfur compounds

The inhibitory effect of thiourea (TUA), ammonium thiosulfate (TSA) and amidosulfonic acid (ASA) on the reactivity of fly ash air was investigated using a thermobalance at different heating rates (5, 10 and 20 K min-1). A model fly ash (activated carbon + 50 wt.% CuCl2·2H2O, pyrolyzed at 700 ºC and washed) was used as carbonaceous material. Adding CuCl2·2H2O to the activated carbon led to an increased rate of decomposition with the air’s oxygen. TUA and TSA behaved in a similar way, accelerating the decomposition of the model fly ash. ASA also accelerated the decomposition but to a lower extent. We proof that the increase in decomposition rate is caused by a reaction between carbonaceous material and N- and S-containing compounds. The formation of nitrogenated and sulphured compounds was confirmed by TG-MS. A kinetic model based on a single reaction of order 0.6 showed very good correlations with all the heating rates tested in oxidant atmosphere.