Abstract The kinetics of reactions between gases and solids are typically modeled using shrinking-core or shrinking-pore theoretical frameworks, in which the formation of a uniform solid product layer covering the entire solid surface with a sharp interface between the solid reactant and the product is assumed. However, theories involving a uniform solid product layer cannot predict the kinetic transition behavior that occurs in some gas–solid reactions. This work proposes that the growth of solid product islands occurs instead of the progressive formation of a uniform solid product layer in traditional shrinking-core and shrinking-pore models and establishes a general rate equation theory to model the kinetics of gas–solid reactions for solid reactants of various shapes. The growth of the product islands is calculated using the rate equation theory and is integrated into the shrinking-core model and shrinking-pore model, in which the microstructure of the solid reactant is also considered. Elemental steps of chemical reaction, surface diffusion and product layer diffusion are included in the general rate equation theory. The kinetic parameters included in the model are chemical reaction rate constant ks, surface diffusion coefficient Ds, and product layer diffusion coefficient Dp. The resulting model is analyzed at the limits where either the chemical reaction or product layer diffusion is the rate-controlling step. At very small or very high Ds values, the rate equation theory is equal to the kinetics-controlled regime or diffusion-controlled regime in traditional models; therefore, the traditional models represent special cases of this theoretical rate equation model. At intermediate Ds values, the so-called two-stage kinetic behavior occurs. The transition from the fast initial stage to the diffusion-controlled stage depends on the value of Ds, with the conversion at the transition point increasing with increasing Ds. The rate equation theory is demonstrated to successfully predict the CaO carbonation kinetics under a wide range of experimental conditions including temperature, CO2 concentration, sorbent type, and amount of added inert supports as well as for systems that exhibit a temperature rise during the carbonation reaction The rate equation theory is integrated into a particle model to account for the external diffusion of gas around the particle and intraparticle diffusion as well as the effect of particle structural changes on intraparticle diffusion, such as the pore plugging phenomenon. The developed rate equation theory is an analytical model that can be easily used in reactor-scale modeling or computational fluid dynamics simulations.

中文翻译：

---

气固反应动力学的一般速率方程理论及其在CaO碳酸化中的应用

摘要 气体和固体之间的反应动力学通常使用收缩核或收缩孔理论框架进行建模，其中形成覆盖整个固体表面的均匀固体产物层，固体反应物和产物之间具有尖锐的界面。假定。然而，涉及均匀固体产物层的理论无法预测某些气固反应中发生的动力学转变行为。这项工作提出在传统的收缩核和收缩孔模型中发生固体产物岛的增长，而不是逐渐形成均匀的固体产物层，并建立了通​​用速率方程理论来模拟固体的气固反应动力学。各种形状的反应物。产物岛的生长利用速率方程理论计算，并被整合到缩核模型和缩孔模型中，其中还考虑了固体反应物的微观结构。一般速率方程理论包括化学反应、表面扩散和产物层扩散的基本步骤。模型中包含的动力学参数为化学反应速率常数ks、表面扩散系数Ds和产物层扩散系数Dp。所得模型在化学反应或产物层扩散是速率控制步骤的极限处进行分析。在非常小的或非常高的 Ds 值下，速率方程理论等于传统模型中的动力学控制机制或扩散控制机制；所以，传统模型代表了这种理论速率方程模型的特殊情况。在中间 Ds 值处，发生所谓的两阶段动力学行为。从快速初始阶段到扩散控制阶段的转变取决于 Ds 的值，转变点的转化率随着 Ds 的增加而增加。速率方程理论被证明可以成功预测 CaO 碳酸化动力学在广泛的实验条件下，包括温度、CO2 浓度、吸附剂类型、和添加惰性载体的数量以及在碳酸化反应过程中表现出温度升高的系统 速率方程理论被整合到粒子模型中，以考虑粒子周围气体的外部扩散和粒子内扩散以及颗粒内扩散的颗粒结构变化，如孔隙堵塞现象。发展起来的速率方程理论是一种分析模型，可以很容易地用于反应堆规模建模或计算流体动力学模拟。