Thermal destruction kinetics of coal and solid biomass mixtures

Abstract

Introduction. The work deals with the research on the kinetics of constituent stages of the combustion process of biomass as an individual fuel and as blends with low reactive anthracite coal from the Donetsk Coal Basin. Materials and methods. The samples of biomass (including the wastes of agricultural and food industries) and Ukrainian from the coal Donetsk Basin were studied by means of nonisothermal TGA. Kinetic studies of the samples was carried out on the Paulik-Paulik-Erdei Q-1000 system derivatograph with the integrated complex of the synchronous data analysis of the STZ 449 Jupiter NETZSCH in the air atmosphere with the heating rate of 20 °C/min within the temperature interval 25-1000 °С. Results and discussion. Raw data were processed and generalized within differential and integral approaches. It has been shown that the differential method of data processing has to be used coupled with the determination of current normalized values of mass change rate derivative, which presents a serious difficulty. In this respect the integral approach looks more acceptable. Comparison of approximations has been presented. It has been shown that the Coats-Redfern approximation in a form of a series does not increase the approximation accuracy if an increased number of the series members is taken into account. The appropriate range of correlations has been determined by means of the parameter E/RT>4 which is valid for the dehumidification and devolatilization regions. For the processes of the coke burnout the correlation of Senum-Yang looks more appropriate. The obtained set of kinetic constants were used with the appropriate form of the Arrhenius type differential equation and the sample mass loss thermal histories were calculated. The deviation between calculated and experimental values of the sample mass loss does not exceed 10% within a whole temperature range 0-700 K. Conclusions. The methodology of the constituent stages distinguishing and obtained kinetic constants can be used in engineering calculations of the combustion constituent stages duration and fuel components balance as well as development of process sub models for 3-d simulations.

Carbon burnout from the char of a single cylindrical pellet

“…In studies into pellet burning, two approaches can be identified: (1) crushing pellets to small (thermally thin) particles and thermogravimetric study of their thermal destruction and carbon burnout at a relatively slow heating rate [8]; such studies were carried out as to the torch [9,10] or fluidised bed burning [11]; (2) study into thermal destruction and carbon burnout from larger particles and whole pellets (thermally thick particles) relating to their burning in a fixed fuel bed [12][13][14][15].…”