Numerical investigation of flow, heat transfer, and kinetic reaction in a large‐difference bidisperse, circulating fluidized‐bed reactor

Abstract

To study particle bidispersity effect on the comprehensive performance of a gas–solid fluidized system, multi‐field coupling numerical research of large‐difference bidisperse circulating fluidized bed was performed. First, numerical simulation was conducted on the dynamic characteristic of a bidisperse gas–solid system that contained both Geldart A and B particles; heat transfer and reaction performances were then studied with the introduction of a propane dehydrogenation (PDH) kinetic reaction model; and finally, the concept of coupling fluid catalytic cracking (FCC) and PDH processes was proposed, and the feasibility was preliminarily discussed. The results showed that the two particle phases were hierarchically distributed with a pronounced segregation layer due to their large‐difference bidispersity characteristic, the Geldart B‐type particle was in a bubbling fluidizing state, while the Geldart A‐type particle was in a turbulent fluidizing state. With the initialized bed and regeneration temperature set to 973 K, the regenerated catalyst's final, balanced temperature could decrease to 942 K, which demonstrated that a significant decline in contact temperature between the feedstock and catalyst could be achieved in the following FCC risers. Additionally, this coupling process also achieved a nearly complete conversion of propane into propene, with a conversion efficiency of above 95%. The results showed the feasibility of this coupling process, which could optimize FCC riser reaction conditions and further achieve a higher‐valued light gas yield. This research can provide a reference for the study of the bidispersity effect on a gas–solid system, and the introduced coupling process can provide a new model for the FCC process's optimization.

Experimental Investigation on Bubble and Agglomerate Behaviors of Geldart B Particles in a 3D Gas–Solid Fluidized Bed Reactor

“…Meanwhile, the bubble rise velocity is greater in the central region than near the wall. (5) The agglomerate frequency remains below 0.6 Hz for the Geldart B particles while it reaches 25 Hz for the Geldart A particles. The force balance analysis presents that the collision force exceeds the net force of the drag force, the cohesive force, and the gravity−buoyancy force for the Geldart B particles, implying that aggregation is less likely for Geldart B particles.…”

“…Gas–solid fluidized beds have been extensively applied in chemical industries owing to their efficient gas–solid contacting, continuous powder handling capability, and excellent heat and mass transfer characteristics. − Mesoscopic properties related to bubbles and agglomerates have a direct impact on hydrodynamics and reaction conversion in a gas–solid fluidized bed. − …”

Numerical simulation and structure optimization of spiral wound heat exchanger with novel spacing bars

“…Due to the complexity of the shell side of the SWHE, a polyhedral mesh is used for mesh division. [ 20 ] Figures 2 and 3 are the schematic diagram mesh details of the traditional and new structures, respectively. Before the calculation, the grid is verified with the outlet temperature and the pressure drop between the inlet and outlet as indicators.…”

Estimation of Particle Dispersion Characteristics in a Fluidized Bed with the Binary Mixture of Geldart A and B Types Using the Optical Fiber Probe Method

“…17 Song et al carried out numerical research on the fluidization characteristics of a fluidized bed containing a binary mixture of Geldart-A and B type particles, and the influence of superficial gas velocity and particle packing conditions on the particle mixing was addressed. 18,19 In the context of experimental research on mixing and segregation characteristics in a binary mixture or bidisperse fluidized bed, the selection of a suitable measurement method is of significant importance. Previous investigations have commonly employed the rapid shut-off method.…”