ABSTRACT
The Coats-Redfern method is commonly used to calculate the activation energy of the thermal degradation from a single non-isothermal thermogravimetric curve since its first proposal in 1964. This paper represents the accurate expressions, sound derivation process and proper usage of the Coats-Redfern equations, based on the critique into the Coats-Redfern's original article, Djalal Trache's incorrect comments on Reza Arjmandi et al.'s article, and the flaw in Reza Arjmandi et al.'s work per se.
Subject(s)
Cellulose , Nanocomposites , Bentonite , PolyestersABSTRACT
Chemical kinetic modeling was applied to simulate N transformation in the pressurized oxy-fuel combustion process of pulverized coal. Modeling accuracy was validated by experimental data at different operation pressures. The key reaction paths from fuel-N to different N products were revealed by analyzing the rate of production. NO formation was synergistically affected by six elementary reactions, in which NCO and other intermediate species were involved. The reactions among N, NH, NH2, and NO were the key paths of N2 formation. After pressurizing the combustion system, NO and N2 contents decreased and increased, respectively. High operation pressure inhibited the diffusion of NO from the internal to the external part of char. This condition prolonged the residence time of NO inside the char, triggered a typical heterogeneous reaction between gaseous NO and unburned char, and reduced the conversion from fuel-N to NO. Moreover, modeling was performed to predict NO x emission in pressurized oxy-fuel combustion as a function of various operating parameters, including temperature and excess air and recycling ratios. This study may provide guidance for reducing NO x emissions and improving combustion efficiency in oxy-fuel combustion, and it can serve as a reference for industrial applications that involve pulverized coal combustion.
