蜂窝状催化剂中空结构对固定床反应器压降的影响

压降是衡量固定床反应器优劣的重要指标，直接影响了反应性能和综合能耗，催化剂颗粒的外形和尺寸是影响固定床反应器压降的关键因素。采用颗粒分辨计算流体力学模型，研究了工业上常用的蜂窝状催化剂颗粒上中空结构对固定床反应器压降的影响规律。首先，通过对比实验测量的催化剂床层空隙率和压降，验证了建立的颗粒分辨计算流体力学模型的合理性和准确性，其中模型计算获得的压降与实验值相差5%以内。接着，研究了蜂窝状催化剂颗粒开孔个数的影响，发现在催化剂颗粒体积和开孔体积相同的情况下，开孔个数不会显著影响催化剂床层的空隙率，但开孔个数增加会导致压降增大，这主要是由于孔径变小后增大了流体在孔内的动量损失。最后，考察了单孔柱催化剂颗粒尺寸的影响，发现可通过调变外圆柱半径、内孔半径和高度，进而大幅度改变催化剂床层空隙率和压降，当单孔柱壁面越薄时，空隙率越大，致使压降越低。研究结果可以为催化剂颗粒外形的优化设计提供强大的模型工具和一定的理论指导。

Influence of hollow structure of honeycomb catalysts on the pressure drop in packed bed reactors

The pressure drop is an important indicator to measure the pros and cons of the fixed bed reactor, which directly affects the reaction performance and comprehensive energy consumption. The shape and size of the catalyst particles are the key factors affecting the pressure drop of the fixed bed reactor. In this work, the effect of hollow structure of honeycomb catalyst pellets (one type of pellets commonly used in the industry) on the pressure drop in packed bed reactors is investigated by using particle-resolved computational fluid dynamics (PRCFD). Firstly, the PRCFD model built in this work is validated by comparing with the voidages and pressure drops obtained from experiments. The deviation between the pressure drops calculated by PRCFD model and obtained from experiments is less than 5%, proving the rationality and accuracy of the PRCFD model. Then, the effect of pore number is investigated. The results show that pore number only very slightly affects the voidage but significantly affects the pressure drop under the same volumes of pore and catalyst. With the increase of pore number, the pressure drop goes up, as the loss of momentum is higher when fluid flows through a smaller pore. Eventually, the effect of pore structure of a Raschig ring catalyst pellet is studied. The voidage and pressure drop can be significantly regulated by adjusting outer cylinder radius, inner pore radius, and height. When the wall of the Raschig ring is thinner, the voidage is higher, resulting in the lower pressure drop. This work can provide a powerful model and some theoretical guidance for the optimal design of catalyst pellet shape.