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The Oxy-fuel combustion of Yunfu bituminous (YFB) chars was studied by isothermal thermogravimetric experiments at 1273K-1573K. The surface area of coal chars prepared at different stages of Oxy-fuel combustion was determined by BET methods. The pyrolysis temperature leads to a slight increase in the average pore diameter and surface area, and the average pore diameter of YFB increases with increasing carbon conversion. Pore structure parameters were calculated by random pore model. Compared to the experimental data, it is found that the random pore model has good ability to depict the reactivity of coal chars Oxy-fuel combustion under high temperature, indicating the random pore model was used to depict the reactivity of coal char combustion in Oxy-fuel. Introduction The combustion of coal chars for energy production results in the generation of greenhouse gases, with CO2 as the major contributor, which are emitted to the atmosphere [1] . There is a general agreement on the need to reduce the emissions of CO2; although the ways approach the problems are rather different. Combustion of fossil fuels in an Oxy-fuel environment is one of several promising new technologies for having a significant impact on reducing greenhouse emissions [2, 3] . Non-catalytic gas-solid reaction, such as coal combustion as well as gasification, which is influenced by many factors (such as atmosphere, pyrolysis time, temperature), is a very complicated phenomenon, particularly to coal char [4, 5] . It has an abundance of submicropores, of which the surface areas have been thought to be predominant in the char reactions [6-8] . Coal characterization has been extensively studied over the years [9, 10] . The combustion of a porous carbon particle is a kinetic process. Coal char properties not only directly have impact on combustion and/or gasification reactions, but also intensify the complexity of the reaction [5, 6, 8] . Moreover, some researchers have conducted researches to study the emission of NO in Oxy-fuel combustion, and the main factors influencing NO emission have also been carefully investigated [2, 3] . This can be of importance in revealing in-depth reaction mechanism in Oxy-fuel combustion atmosphere. In this work, the combustion of Yunfu bituminous chars in Oxy-fuel was studied by isothermal thermogravimetric experiments. The characteristics of coal chars combustion at different temperatures were examined in Oxy-fuel. Experimental Section Yunfu Bituminous (YFB) coal was used in the present study as the representatives of coal. Coal samples were first crushed and sieved. Fractions in the size range of <0.175mm was used in the experiments. Elemental analysis and proximate analysis were carried out in vario EL-2 and TGA2000 (Navas Instruments, Spain), respectively. Coal properties are shown in Table 1. 2nd Annual International Conference on Advanced Material Engineering (AME 2016) © 2016. The authors Published by Atlantis Press 968 Tab.1 Coal Sample Analysis Sample Proximate Analysis(wt%, air-dried) Ultimate Analysis (wt%, air-dried) Moistur e Volatil e Ash Fixed Carbo n C H N S O Yunfu Bituminous (YFB) 10.65 25.91 17.1 0 46.34 58.03 3.97 1.00 1.26 7.99 Pyrolysis and combustion in the TGA: The experiments were carried out on thermogravimetric balance (STA 409) of Germanic NETZSCH Corporation. Firstly, coal samples were heated at a heating rate of 30k/min up to the final temperature range of 1273K, 1373K, 1473K, 1573K at N2 atmosphere, and then atmosphere was changed to the mixed gas of O2/CO2 with the ratio of 1:4 for 20~30 minutes with a flow rate of 100ml/min. Chars preparing in a tubular furnace: The tube furnace was first heated up to the temperature range of 1273K-1573K, and then pumped in the mixed gas of O2/CO2 with the ratio of 1: 4 at a flow rate of 100ml/min, and finally moved coal chars into heating zone rapidly to stay at predetermined time. BET surface area analysis: The BET surface area of different coal chars was measured with a Micromeritics ASAP2020 automated gas adsorption apparatus. The adsorption/desorption isotherms (N2, -196°C) were determined using the TriStar 3000 gas absorption analyzer from Micromeritics. To ensure the reproducibility and accuracy of analysis, repeated experiments were accomplished. Results and Discussion The influence of temperature: Carbon conversion can be calculated by following equation

Reactivity and Kinetic Analysis of Coal Chars Combustion under Oxy-fuel Conditions