催化剂颗粒的力学性能与机械强度

The Mechanical Characteristics and Mechanical Strength of Catalyst Particles

本文将弹性力学方法引入催化剂颗粒内应力分布的计算。实验结果表明：催化剂材料的应力应变关系符合弹性材料的特征；催化剂材料的强度判据可采用最大剪应力准则；催化剂材料的力学性能数据中，弹性模量基本上为常数，泊松系数则明显地随应变变化，这种现象充分表明了多孔催化剂材料随外界压力的变化自动调节其内部孔率这－本质特征。在实验结果的基础上，本文给出了镍催化剂（以水泥作粘合剂）的力学性能数据，并对三种异形催化剂颗粒的侧向承载能力进行了对比。

The mechanical strength of catalyst particles depends not only upon their materials, but also upon their shape and size. The diversity of catalyst materials makes their mechanical characteristics quite differently. So there are no an accepted mechanical approach (or theory) and subsequent strength criterion for predicting the effects of shape and size of particles on their mechanical strength. The conventional method of using crushing force of catalyst particles as the basis of comparison will be too inaccurate as it can not indicate what is the contribution of materials' nature, shape or size of particles to their mechanical stfength. In this paper, the classical elastic theory is introduced into the calculation of the stress distribution inside catalyst particles. Experimental results demonstrate that catalyst material gives the identical strainstress trend as that of elastic material, and that when external force is increasingly exerted, crack will first take place at the angle of 45°with the direction of the exerting force. The latter observation confirms that the theory of maximum shearing stress can be used as the strength criterion. The difference between catalyst material and metal is that the Poisson ratio of metal is a constant, while that of catalyst changes with strain. This feature indicates that the porous catalyst material will automatically adjust its inside porosity when external load changes. For nickel catalyst (for the production of hydrogen by steam reforming reaction of methane), the necessary mechanical properties are: Young'S modulus E=4.3774GPa Poisson ratio μ=0.06133+l. 1970xl0-5 ε-3.3162xl0-9ε2+2.9859×10-13 ε3 ε≤ 15355 μ. Crushing strength ah=75 .010MPa. Safety factor nb ≥1.6 For reference, the radial crushing loads of three kind of abnormal-shaped catalyst particles are Fb=885.02N, 658.68N and 880.42N for ring, wheel-shape, and honeycomb shape respectively.