Fluidized bed opposed jet mills are capable of meeting the continuously growing demand for contamination-free fine particles. In this type of jet mill, the solid material is entrained and accelerated by expanding gas jets that are focused onto a focal point inside a fluidized bed. The resulting particle collisions induce breakage. The process is affected by the relative particle velocities and the number of particle–particle collisions. Clearly, both quantities are distributed. However, to date, neither relative particle velocities nor collision frequencies in such units have been determined. The present work introduces an innovative method to assess the stressing conditions in jet mills experimentally. To this end, mixtures of glass and ductile metal microspheres were used, with the latter employed in small amounts. Inter-particle collisions between the aluminum and glass spheres lead to the formation of dents on the microparticles. The size and number of these dents are associated with the individual collision velocities and overall collision frequencies. The correlation between dent size and collision velocity was obtained from finite element calculations based on empirical data. The proposed approach was validated using particle image velocimetry during secondary gas injection into a fluidized bed reactor. In this case the effect of the distance between two opposed nozzles was examined. For a lab-scaled fluidized bed opposed jet mill the effects of gas pressure and hold-up were investigated. Relative particle velocities were found to be significantly lower than the gas velocities, while the number of contacts per particle was determined to be extremely high.

流化床对置射流磨机能够满足对无污染细颗粒的不断增长的需求。在这种类型的气流粉碎机中，通过使聚焦在流化床内部焦点上的气体喷射流膨胀并带走并加速固体材料。产生的粒子碰撞会导致破裂。该过程受相对粒子速度和粒子间碰撞次数的影响。显然，这两个数量都是分布的。然而，到目前为止，还没有确定这种单位的相对粒子速度或碰撞频率。本工作介绍了一种创新的方法，可以通过实验评估喷射磨中的应力条件。为此，使用玻璃和易延展的金属微球的混合物，并以少量使用。铝和玻璃球之间的粒子间碰撞导致微粒上形成凹痕。这些凹痕的大小和数量与各个碰撞速度和整体碰撞频率相关。凹痕大小与碰撞速度之间的相关性是根据经验数据通过有限元计算获得的。在将二次气体注入流化床反应器期间，使用粒子图像测速法验证了所提出的方法。在这种情况下，检查了两个相对喷嘴之间的距离的影响。对于实验室规模的流化床对置喷射磨，研究了气体压力和滞留率的影响。发现相对速度明显低于气体速度，