Influence of oxidative treatments on the thermal reactivity of lignites

Influence of wet oxidation on the burning profiles of lignites was investig ated. For this purpose, five different Turkish lignite samples were treated with either 0.2 M sodium carbonate solution or distilled water at 423 K un der 1.5 MPa partial pressure of oxygen for 60 min. TGA technique was applie d to the original and treated lignite samples from ambient temperature to 1 223 K under dynamic dry air atmosphere. Burning profiles of the original an d treated lignite samples were derived from the thermogravimetric curves. I n the case of alkaline conditions, some degradation took place in the organ ic matrix of the lignite samples. Loss of combustible part of the treated l ignite samples led to important changes in the burning profiles of the trea ted lignite samples compared with those of the original lignite samples. Th e presence of sodium carbonate was detected from its decomposition peaks, p redicting that some of sodium carbonate could not be eliminated from the tr eated lignite samples. Sulphuric acid forming asa result of the oxidation o f sulphur compounds, removed some mineral species from the treated lignite samples, affecting burning profile. Oxidation of the lignite samples in eit her alkaline or acidic medium increased thermal reactivity. Consequently, t he ignition temperature was decreased and burning rates increased. (C) 1999 Elsevier Science B.V. All rights reserved.