Abstract

The internal friction among unfluidized particles makes them polymorphic, thus confusing measurements of minimum fluidization velocity (U_mf) and segregation index (S). Such a polymorphic characteristic of the packed bed caused the ΔP_b–U_g↑ curve measured subsequently to be poorly reproducible. The poor reproducibility of determining U_mf from this curve resulted eventually from the ambiguity in the traditional definition of U_mf. It did not clearly indicate which of the many states the particles should be initially packed into before measuring the ΔP_b–U_g↑ curve. The internal friction caused it difficult to accurately measure S for low gas velocities. The corresponding stable fluidization states could not be obtained through reducing the gas flow slowly from complete fluidization to these velocities. Some particles lost the capability to move before reaching their stable equilibrium positions. Only some steady states which could not represent the given U_g were obtained. Many states of the unfluidized particles were demonstrated to be metastable and belong to the amorphous/glass state. They could not recover/restore themselves after relatively large perturbations.

摘要

未流化颗粒之间的内部摩擦使它们具有多态性，从而混淆了最小流化速度 ( U _mf ) 和分离指数 ( S ) 的测量值。填充床的这种多晶型特征导致随后测量的 Δ P _b – U _g ↑ 曲线重现性差。从该曲线确定U _mf的重现性差最终是由于U _mf的传统定义中的歧义造成的。它没有明确指出在测量 Δ P _b – U _g之前，粒子最初应该进入许多状态中的哪一个↑曲线。内部摩擦导致难以准确测量低气体速度的S。通过将气流从完全流化缓慢降低到这些速度，无法获得相应的稳定流化状态。一些粒子在到达其稳定的平衡位置之前就失去了移动的能力。仅获得了一些不能代表给定U _g的稳态。未流化颗粒的许多状态被证明是亚稳态的并且属于无定形/玻璃态。在相对较大的扰动之后，他们无法恢复/恢复自己。