Zhenxing Guo

Decomposition kinetics of hydrogen bonds in coal by a new method of in-situ diffuse reflectance FT-IR

Abstract The kinetics of decomposition of hydrogen bonds in a Chinese lignite was studied using a new method of in-situ diffuse reflectance FT-IR (DRIFT) with pulverized coal samples directly. In addition, a new experimental technique in DRIFT measurement to avoid the condensation of volatile matter at high temperatures was introduced and used in this work. Based on two hypotheses, the single reaction model is used to calculate kinetic parameters for decomposition of hydrogen bonds (except OH-π) in coal heated up to 560°C. The results show that the decomposition of carboxylic acid dimers, OH-N and SH-N follows the second order reaction, while the decomposition of OH-OR2, tightly bound hydroxyl tetramers and self-associated hydroxyls follows the first order reaction. The calculated activation energies of some hydrogen bonds agree well with those obtained with other methods in references. Among the six types of hydrogen bonds studied, the decomposition of carboxylic acid dimers, OH-N, SH-N and tightly bound hydroxyl tetramers can be divided into two stages (230-380°C and 380-500°C), while that of OH-OR2 and self-associated hydroxyl groups can be treated as only one stage. Moreover, the mechanism of decomposition of tightly bound hydrogen bond was suggested based on the comparison of decomposition activation energy of self-associated OH with its bond strength in references.

Effect of lime addition on slag fluidity of coal ash

Abstract The ash fusibility temperature (AFT) and slag fluidity of three different coal ash samples through addition of CaO with different amounts were studied. Especially the variation of temperature at critical viscosity was examined at different viscosities. The results show that the fusibility temperatures of coal ashes decrease and then increase with increasing addition amount of CaO, which is consistent with the change of liquids temperature with CaO content calculated by FACTsage. Slag viscosity also decreases with increasing amount of CaO addition above the temperature of critical viscosity ( T cv ). The temperature of critical viscosity firstly decreases with increasing addition of CaO, and then reaches a minimum value when the content of CaO is around 15%. FCATsage was employed to calculate the liquid composition at the temperature of critical viscosity. It indicates that high content of FeO of liquid leads to the low temperature of critical viscosity.