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The ignition and combustion characteristics of anthracite-rice husk (AC-RH) and bituminous coal-rice husk (BC-RH) pellets were investigated in a vertical heating tube furnace under different experimental condition, for gas temperature (873 K–1073 K) and under air and different oxygen concentration (21–70%) in CO 2 /O 2 atmosphere. The investigation of the ignition and combustion characteristics focused on ignition mechanism, ignition delay, ignition temperature and combustion process. AC-RH pellets had two ignition mechanism in CO2/O2 atmosphere: homogeneous ignition of volatile and heterogeneous ignition of char. Heterogeneous ignition region decreased while homogeneous ignition increased as rice husk blending ratio increased in oxygen concentration-gas temperature plane. Only homogeneous ignition was observed when rice husk blending ratio was 30%. As for BC-RH pellets, only homogeneous ignition occurred in all experimental conditions. The effect of the rice husk blending on the anthracite was more pronounced than the bituminous coal for ignition mechanism. As oxygen concentration increased, a significant reduction in ignition delay and ignition temperature was observed at low rice husk blending ratio and low gas temperature. but at 1073 K, high oxidizer temperature weakened the effect of biomass blending and oxygen concentration on ignition delay and ignition temperature. Meanwhile, at 20% and 30% rice husk blending ratio, it also weakened the effect of oxygen concentration and oxidizer temperature on ignition delay and ignition temperature. In contrast, blending ratio had a more significant effect on ignition behavior. The replacement of N 2 by CO 2 at the same oxygen concentration contributed to an increase in ignition delay time and internal ignition temperature, which suppressed the ignition behavior. Different ignition mechanisms corresponded to different combustion processes. • The ignition and combustion behavior of coal-biomass blend pellet was investigated. • The critical condition of the transition for ignition mechanism was found. • The effect of Tg, O2% and BRH on ignition delay and temperature was discussed. • The effect of RH blending on anthracite was pronounced than bituminous coal. [ABSTRACT FROM AUTHOR]

Summary: This study applied the artificial neural networks (ANNs) model to the thermal data obtained by suspension ignition and combustion experiment of single peanut shells (PS, millimeter scale) pellet under O2/CO2 atmosphere. ANN11 was the best ANN model for predicting the relevant parameters of PS combustion. The coincidence between ANN prediction data and experimental data was over 99%. Two modes of biomass pellet ignition were observed: homogeneous ignition of volatiles and hetero‐homogeneous ignition of volatiles and char simultaneously. The ignition mode was transformed from homogeneous ignition to hetero‐homogeneous ignition when oxygen concentration was 50%. In addition, it was observed that ignition at the bottom emerged first, and then the upper end was ignited, finally generating an envelope flame. This phenomenon occurred when gas flow temperature exceeded 873 K or the oxygen concentration was greater than 50%. The reduction of ignition delay time and internal ignition temperature from 21% to 50% oxygen concentration was more intense than that of 50% to 100% oxygen concentration. Increasing oxygen concentration or temperature resulted in a shorter, brighter, and more stable volatile flame of biomass pellets, which reduced volatile burnout time. Nevertheless, the impact of gas flow rate on biomass combustion was intricate and irregular. [ABSTRACT FROM AUTHOR]

Abstract This study investigated the combustion characteristics and kinetics of sewage sludge (SS), wheat straw (WS) and their blends using thermogravimetric analysis, under air condition. Combustion characteristic parameters of SS blended with 5%–50% WS was enhanced, especially revealed by an increase in comprehensive combustion index. A significant synergetic interaction was found in high temperature region through experiments. When proportion of WS was 50%, the synergetic interaction was strongest. And the catalytic effect of alkali metal oxides in WS ash on the combustion of SS residues at high temperature region had a strong effect on synergetic interaction. Metal oxides circulated in different oxide forms to transport oxygen to carbon surface, leading to catalytic effect. Activation energy was evaluated by two isoconversional method: Flynn-Wall-Ozawa and Vyazovkin method. The lowest average activation energies of the blends were obtained at 50% wheat straw blending ratio (89.29 kJ/mol by FWO and 87.48 kJ/mol by V, respectively). The thermodynamic parameters (Gibbs free energy, Entropy and Enthalpy) were also obtained. And two master plots methods were utilized to determine the appropriate fit kinetic model of combustion which can be described by Avarami-Erofeve (A2). Highlights • TG analysis of co-combustion between sewage sludge and wheat straw was studied. • Blending wheat straw improved the thermal behavior of sewage sludge combustion. • Synergetic interaction was found at high temperature in positive manner. • The minimum average activation energy was obtained by blending 50% wheat straw. [ABSTRACT FROM AUTHOR]

The combustion behavior and gas product characteristics of coal gangue (CG) and peanut shell (PS) in air atmosphere were studied by thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR). Artificial neural network (ANN) method was used to establish the optimal prediction model of CG and PS co-combustion. The heating rate of TG-FTIR experiment was set to 10 °C/min, 20 °C/min and 30 °C/min. The mass fractions of PS in the experimental samples were 0%, 25%, 50%, 75% and 100%. Some functional groups in the gas products were detected by Fourier transform infrared spectrometer. Moreover, the apparent activation energy (E) was calculated by Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS). The activation energies of CG and PS mixture combustion are significantly lower than that of pure substance. ANN models have been established to predict the relationship between mass loss and experimental conditions. By comparing errors and correlation coefficients, it is found that the ANN20 model is optimal. Image 1 • First study on application of ANN model to co-combustion of CG and PS. • The predicted data of ANN were in good agreement with the experimental results. • The gas products of co-combustion were detected. • Activation energy was estimated from the KAS and FWO methods. • ANN20 is the best model for predicting CG and PS combustion. [ABSTRACT FROM AUTHOR]

This paper investigates the ignition and combustion characteristics of cattle manure particles under different environmental conditions, and analyses the ash produced by combustion. The cattle manure particles were fixed in a vertical heating furnace, and a thermocouple and camera recorded the internal temperature and combustion process of the particles. The environmental temperature of the combustion chamber was set at 873, 973 and 1073 K, and the oxygen concentrations were 10–80%; the gas flow rate was set to 10, 20 and 30 L/min, respectively. The experimental results show that the effect of environmental temperature on the ignition and combustion of cattle manure particles is most obvious. Under most circumstances, the volatile matter begins to ignite before the particulate matter. As the environmental temperature and oxygen concentration increase, the condition of ignition and combustion were improved, and the internal ignition temperature, ignition delay and volatile combustion time were reduced. In addition, thermogravimetric experiments on powdered cattle manure were also carried out at four heating rates, and four peaks were presented in the derivative thermogravimetric (DTG) curve, corresponding to four different stages of cattle manure combustion. • Thermogravimetric experiment and particle combustion experiment were combined. • The ignition and combustion process of single cattle manure particles was detected. • The skeleton of the single particles remained intact during burning process. • The tendency of slagging and fouling of cattle manure ash is very low. [ABSTRACT FROM AUTHOR]