Four coal chars were prepared in a flat flame flow reactor (FFR), which can simulate the temperature and gas composition of a real pulverized coal combustion environment. The pore structure of chars was measured by mercury porosimetry and nitrogen adsorption, and the Hg and Brunauer-Emmett-Teller (BET) surface areas were obtained. The kinetics of NO-char was studied in a drop-tube furnace (DTF) and thermogravimetric analyzer (TGA). In the TGA experiments, the random pore model (RPM) was applied to describe the NO-char reactions and obtain the intrinsic kinetics. By presenting the data of DTF and TGA experiments on the same Arrhenius plot, it can be concluded that TGA is an available tool to study the kinetics of a high-temperature NO-char reaction. With respect to the DTF experiments, in comparison to the BET surface area, the Hg surface area is a better basis for normalizing the reactivity of different coal chars because of less scatter in the measured values, better agreement with TGA experimental data, and more stable values during the process of reaction. Moreover, by comparing the Hg surface area of chars before and after reactions, it is believed that the Hg surface area basis is more appropriate for high-rank coal chars. The determined kinetic rate constants are in good agreement with other data in the literature, and a new rate constant expression is proposed.

Five Chinese coal chars were prepared in a flat flame flow reactor that can simulate the conditions of real pulverized coal combustion. The kinetics of the NO-char reaction at 1273, 1373, 1473, and 1573 K was studied in a drop tube furnace. A new model of the high-temperature NO-char reaction that took into account the pore diffusion and thermal annealing of char was proposed. The NO-char reaction was predicted by a combination of the model and computational fluid dynamics. Through the comparison of experimental and predicted results, the kinetic parameters for all chars were determined. The predicted results agree well with experimental results at 1273, 1373, and 1473 K, but the model largely underestimates the experimental data at 1573 K. This behavior is explained by a new mechanism of the high-temperature NO-char reaction. In addition, the model successfully normalizes the reactivity of chars with different ranks at high temperature, which is considered to be valuable in predicting the NO reduction on char surface at high temperature.

Five coal chars were prepared in a flat flame flow reactor (FFR) which can simulate the temperature and gas composition of a real pulverized coal combustion environment. Reactivity of these chars with NO in the temperature range of 1273–1573 K has been characterized by experiments in a high-temperature drop tube furnace (DTF). Two normalized parameters (X̅ and m c) are proposed to analyze the effect of inherent metal content on char reactivity. The inherent metal catalysts in chars, such as magnesium, potassium, sodium, calcium, and iron, can significantly increase reactivity of char by reducing the activation energy. The reactivity of NO–char reaction increases with m c value monotonously and linearly in a certain range. Experimental results showed that the catalytic activity of magnesium, potassium, sodium, calcium, and iron at the temperatures of 1273–1573 K were in decreasing sequence. In this study, the magnesium, which was rarely studied in other literature, appears to have a great catalytic effect on the reduction of NO by chars.

Two Chinese coals were used to prepare chars in a flat flame flow reactor which can simulate the temperature and gas composition of a real pulverized coal combustion environment. Acid treatment on the YB and SH chars was applied to obtain demineralized chars. Kinetic characterization of NO-char reaction was performed by isothermal thermogravimetry in the temperature range of 973-1,573 K. Presence of catalytic metal matter can increase the reactivity of chars with NO, which indicates that the catalytic effects of inherent mineral matter play a significant role in the NO-char reaction. The discrete random pore model was applied to describe the NO-char reactions and obtain the intrinsic kinetics. The model can predict the data for all the chars at various temperatures well, but underestimate the reaction rates at high carbon conversions for the raw YB and SH chars, which can be attributed to the accumulation of metal catalyst on char surface.

Two Chinese coals (YB lignite coal and SH bituminous coal) were used to prepare the chars. The chars were obtained in an entrained flow reactor which can simulate the temperature and gas composition of a true pulverized coal combustion environment. The kinetic characterization of NOchar reaction was performed by isothermal thermogravimetry in the temperature range 1073-1573K. It was confirmed that the reactions were under chemical kinetic control in the lowtemperature regime (1073-1273K) for SH char. The discrete random pore model was applied to describe the NO-char reactions. The model can predict the data at 1073 and 1173K very well, but underestimate the reaction rates at high carbon conversions, which can be attributed to the catalysis of inherent minerals in chars. However, the influence of the catalysis on reactions of SH char is moderate. Ultimately, the determined intrinsic activation energy of NO-char is 111 J/mol.