碱及碱土金属对准东煤热解特性及动力学影响分析

利用程序升温热重(TG)技术对准东原煤(R-form)和酸洗煤(H-form)样品的热解过程进行了研究,同时,采用分布活化能模型(DAEM)法对两者的热解动力学参数进行了计算。结果表明,准东煤在热解过程中保持了丰富的孔隙结构;碱及碱土金属(AAEM)的存在不会对准东煤大分子网络结构造成显著影响,但会提高准东煤的平衡水分含量及二次脱气阶段挥发分释放速率,降低其主热解阶段挥发分释放速率及热解最终失重率;DAEM法可以在较宽的温度范围内对准东煤的热解过程进行准确的描述,R-form和H-form煤样品的热解活化能均随转化率的增大而升高;相同转化率下R-form煤样品的活化能高于H-form,前者活化能分布函数的最大值出现在261.85kJ/mol处,而后者出现在264.51kJ/mol处;AAEM的存在使准东煤的热解活化能升高且分布更加集中,使其热解反应活性降低;准东煤热解的频率因子与活化能之间呈现明显的动力学补偿效应。

Effects of alkali and alkaline earth metallic species on pyrolysis characteristics and kinetics of Zhundong coal

The pyrolysis process of raw (R-form) and acid-washed (H-form) Zhundong coal was investigated by temperature-programmed thermogravimetry, and the kinetic parameters were calculated using distributed activation energy model (DAEM). The results show that the pore structures of Zhundong coal keep abundant in pyrolysis. The presence of alkali and alkaline earth metals (AAEM) has no significant influence on the macromolecular network structure of Zhundong coal, but raises its equilibrium moisture content and release rate of volatiles during the secondary degasification stage. AAEM lowers release rate of volatiles during the main pyrolysis stage and final weight loss. The pyrolysis behavior of Zhundong coal could be described by the DAEM accurately within a wide range of temperature. The pyrolysis activation energy of R-form and H-form coal increases with increasing conversion. The activation energy of R-form coal is higher than that of H-form coal at the same conversion. The maximum value of activation energy distribution function of R-form and H-form coal is 261.85 and 264.51 kJ/mol, respectively. AAEM elevates the pyrolysis activation energy, makes its distribution more concentrated, and reduces the pyrolysis reactivity. The relationship between frequency factor and activation energy presents obvious kinetic compensation effect.