不同方法制备氧化锌高温煤气脱硫剂的原位再生动力学

Kinetics study of zinc oxide sorbent prepared by different methods for hot coal gas desulfurization

分别采用室温固相法和均匀沉淀法原位制备氧化锌脱硫剂前体,并在热天平装置上研究了再生温度及反应中氧气浓度对氧化锌高温煤气脱硫剂的原位再生行为的影响。采用收缩核模型对脱硫剂前体氧化再生过程的动力学进行了描述,并计算其反应级数及表观动力学参数,结果表明:脱硫剂原位再生的过程中动力学控制步骤发生了转移,当再生转化率低于80%时,再生反应主要为表面化学反应控制阶段;当再生转化率高于85%时,再生反应主要是颗粒内扩散控制。室温固相法和均匀沉淀法所制备脱硫剂的表观化学反应速率常数的指前因子ks0分别为4.45m/s、1.01m/s,化学反应活化能E_a分别为43.12kJ/mol、65.76kJ/mol,有效扩散系数因子D_(e0)分别为5.42×10^(–2)m^2/s、1.29×10^(–3)m^2/s,内扩散表观活化能Ep分别为38.38kJ/mol、43.29kJ/mol。此外,通过表征发现均匀沉淀法制备的脱硫剂内部活性组分更加分散、粒径更小、孔隙发达,提高了脱硫剂的再生性能。

In this paper the different methods,such as ambient solid-state method and homogeneous precipitation method,were used to prepare the precursor of zinc oxide sorbent.The effects of reaction temperature and oxygen concentration on the in-situ regeneration of zinc oxide sorbent were investigated on the thermal balance device.Shrinking core model was employed to describe the kinetics of in-situ regeneration process of the precursor.The result showed that when the regeneration conversion rate was less than80%,the regeneration reaction was mainly controlled by surface chemical reaction.When the regeneration conversion rate was higher than85%,the regeneration reaction was mainly controlled by intra-particle diffusion.According to Arrhenius equation,the pre-exponential factors and activation energies of chemical reaction of the apparent reaction rate constant were4.45m/s,43.12kJ/mol for ambient solid-state method and1.01m/s,65.76kJ/mol for homogeneous precipitation method,respectively.The effective diffusivity factor and apparent activation energy of internal diffusion of the ambient solid-state method were5.42×10-2m2/s and38.38kJ/mol,and those of homogeneous precipitation method were1.29×10-3m2/s and43.29kJ/mol,respectively.