异形甲烷蒸汽转化催化剂传质传热耦合数学模型

Coupling Process of Mass Transfer and Heat Transfer for Irregular Shape Methane Steam Reforming Catalyst

针对甲烷蒸汽转化催化剂异形化过程中理论研究困难、性能数据主要依靠实测的问题,建立了适用于异形甲烷蒸汽转化催化剂的传质-传热耦合三维数学模型,用有限元法求解,求解方法简单、快速、精确。应用本模型计算了七孔球形转化催化剂的效率因子,获得了催化剂粒内的浓度、温度、反应速率、温度梯度分布。效率因子模型值与实验值较为吻合,平均相对误差8 22%。模拟结果表明:七孔球形催化剂效率因子在0 2～0 4之间,粒内存在10～16℃的温差,不能视为等温;催化剂粒内浓度、温度变化剧烈,有效反应区仅存在于靠近催化剂外表面的较小范围内,粒内存在较大的死区。

A 3D reaction-diffusion model for irregular methane steam reforming catalyst is developed. The model was solved in non-isothermal condition with finite element method (FEM). FEM is simple, accurate and especially suitable for irregular geometries. The simulation was carried out over seven-channel spherical catalyst. Intraparticle concentration, temperature, reaction rate and temperature gradient profile are calculated. The effectiveness factor of the catalyst is 0.2～0.4. The simulation data of the model are in good agreement with the experimental results. The average absolute deviation between the calculated efficiency factors and those of experiments is 8.22%. Temperature difference of 10-16℃ exists within the catalyst. The parameters within the catalyst keep constant in a large area of central part, contrasting with the sharp change in the surface layer of the catalyst particle. A large equilibrium dead zone exists inside the steam reforming catalyst.