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Reactivity of lignite could be potentially improved by adding with biomass such as lowering the gaseous pollutant emissions. The combustion behavior of lignite/eucalyptus bark blends and their individuals were studied by simultaneous TG–MS technique. The influences of heating rates and blending ratios on combustion performances and gaseous pollutant emissions were assessed. The combustion kinetics were also evaluated in conjunction with volatile matter and fixed carbon burning periods. The ignition and comprehensive combustion indices increased with increasing blending ratios or heating rates. Adding the eucalyptus bark to the lignite was an effective way in reducing the CO 2 , NO 2 and SO 2 emissions. The dominant mechanisms associated with combustion kinetics of volatile matters and char in the eucalyptus bark and most eucalyptus bark/lignite blends around maximum burning rates were mainly dominated by the three dimension diffusion, while the combustion mechanisms of char in the lignite were mainly described by reaction order models. Blending ratios of 20–40% eucalyptus bark were proposed as optimum values for improving the combustion behavior of the lignite. There were certain synergistic effects between lignite and eucalyptus bark during their co-combustion. [ABSTRACT FROM AUTHOR]

One of the most crucial problems in using biomass fuel is the amount of solid wastes produced, which will cause serious deposition and corrosion. This work is mainly focused on an evaluation of ash fusion characteristics of eucalyptus bark, lignite and their blends by using thermal analysis technique. The ash deformation temperatures of eucalyptus bark and lignite were 1181 °C and 1320 °C. The differences between ash softening temperature and hemispherical temperature were 31 °C and 13 °C for biomass/lignite blends with biomass blending ratios of 20% and 80%. Also, the influences of blending ratio and heating rate on the co-fusion kinetics of eucalyptus bark and lignite were revealed based on two-stage scheme, which referred to pre-peak and post-peak around maximum reaction rate point in the main ash fusion region. The activation energy of ash fusion for eucalyptus bark/lignite blends in the pre-peak stage and the post-peak stage was in the range of 419–828 kJ/mol, and 322–702 kJ/mol, respectively. The biomass blending ratio should be controlled within 40% in order to reduce the possibility of sintering for eucalyptus bark/lignite blends. The ash fusion kinetic characteristics of mixture samples had no linear relation with blend ratios due to interaction between biomass and coal. [ABSTRACT FROM AUTHOR]

The kinetics of co-combustion of two herbaceous biomass species (beetroot and switchgrass) with bituminous coal was evaluated using a non-isothermal thermogravimetric method (TGA). The effects of heating rates, sample kinds and blend ratios on the kinetics of co-combustion were revealed based on two-stage scheme, which referred to the two stages before and after the maximum combustion rate. The kinetic parameters and combustion reaction mechanisms were tested by combining the isoconversional method (Ozawa–Flynn–Wall) and the Coats–Redfern method in order to find out the kinetics characteristics responsible for the combustion of the samples. There were significant difference between combustion kinetics of bituminous coal and biomass. The blending ratios and the heating rates had have certain effect on the mechanisms of switchgrass/coal blends at pre-peak. The dominant mechanisms associated with co-combustion kinetics for beetroot/coal at pre-peak and post-peak were described by the Avrami–Erofeev equations. The mechanisms of co-combustion for switchgrass/coal samples at pre-peak were described by the Avrami–Erofeev equation, Z–L–T equation or Anti-Jander equation; however, at post-peak, their mechanisms were described by the Avrami–Erofeev equation. The general kinetic compensation effect correlations were deduced for all samples within the heating rates of 10–90 °C/min. [ABSTRACT FROM AUTHOR]