Thermal behaviour and kinetics of coal/biomass blends during co-combustion

Abstract

The thermal characteristics and kinetics of coal, biomass (pine sawdust) and their blends were evaluated under combustion conditions using a non-isothermal thermogravimetric method (TGA). Biomass was blended with coal in the range of 5-80 wt.% to evaluate their co-combustion behaviour. No significant interactions were detected between the coal and biomass, since no deviations from their expected behaviour were observed in these experiments. Biomass combustion takes place in two steps: between 200 and 360 degrees C the volatiles are released and burned, and at 360-490 degrees C char combustion takes place. In contrast, coal is characterized by only one combustion stage at 315-615 degrees C. The coal/biomass blends presented three combustion steps, corresponding to the sum of the biomass and coal individual stages. Several solid-state mechanisms were tested by the Coats-Redfern method in order to find out the mechanisms responsible for the oxidation of the samples. The kinetic parameters were determined assuming single separate reactions for each stage of thermal conversion. The combustion process of coal consists of one reaction, whereas, in the case of the biomass and coal/biomass blends, this process consists of two or three independent reactions, respectively. The results showed that the chemical first order reaction is the most effective mechanism for the first step of biomass oxidation and for coal combustion. However, diffusion mechanisms were found to be responsible for the second step of biomass combustion.

Characterization of Selected Nigerian Biomass for Combustion and Pyrolysis Applications

“…The kinetic parameters for the pyrolysis of the fuels were estimated from the TGA mass loss curves obtained and are listed in Table 6. For this, it was assumed a global first-order reaction rate [36][37][38][39][40][41] and the pre-exponential factors A (s -1 ) and activation energies Ea (kJ/mol) were calculated according to the reaction rate constant method [41][42][43]. The correlation coefficients (R 2 ) are also reported in Table 6.…”

Review of experimental methods to determine spontaneous combustion susceptibility of coal – Indian context

“…These factors are subsequently compared with other parameters, including: the heating rate, peak temperature, different temperature zone, reaction interval, particle size and weight loss Gil et al, 2010;Idris et al, 2012;Idris et al, 2010;Khare et al, 2011;M. V. Kok, 2012;.…”

“…Basil Beamish, Barakat, & St. George, 2001;Clemens, Matheson, & Rogers, 1991;Cliff, Rowlands, & Sleeman, 1996;Cudmore, 1988;Humphreys et al, 1981 ;Ren, Edwards, & Clarke, 1999;Rosin, 1929;A. C. Smith & Lazzara, 1987;); thermal analysisdifferential thermal analysis (DTA), differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA) (S. C. Banerjee, 2000; S.C. Banerjee & Chakraborty, 1967;Gil, Casal, Pevida, Pis, & Rubiera, 2010;Idris, Rahman, & Ismail, 2012;Idris et al, 2010;Khare, Baruah, & Rao, 2011;M. V. Kok, 2012;C.…”

“…Mine regulators as well as mine operators requires these tests to predict spontaneous combustion/ fire risk to minimise hazards for ensuring safety of miners and machine for sustainable growth. The oxygen avidity studies mainly include the performance of a peroxy complex analysis (S. C. Banerjee, 2000;Sen, Srivastava, & Singh, 2009), rate of reaction studies Gil et al, 2010;Idris et al, 2012;Idris et al, 2010;Khare et al, 2011;M. V. Kok, 2012;, the determination of the Russian U-index (S. C. Banerjee, 2000).…”

Gaseificação de microalgas: estudo termogravimétrico e modelagem matemática do processo em reator solar.

“…onde Té a temperatura absoluta; f (α) representa um modelo hipotético do mecanismo de reação (Gil et al, 2010); αé a razão de conversão da biomassa alimentada e dα/dté a velocidade da reação, ou seja, a taxa isotérmica da mudança do grau de transformação (conversão) com o tempo.…”