Enhancing mixing of cohesive particles by baffles in a rotary drum

A soft-sphere discrete cohesive powder model was used to simulate the transverse mixing of particles in a rotary drum. Using this model, the effect of cohesion strength and baffle length was investigated. Mixing time （tR） and mixing entropy were used to characterize the mixing behavior. The results showed that increasing particle cohesiveness increases tR. Baffles enhanced transverse mixing, especially for high- cohesive particles. Moreover, the baffle length played a significant role on mixing. An optimized length of 0.50 （L/R） enhances transverse mixing for high-cohesive particles, Further increases in baffle length only decreases the mixing rate by impeding the surface flow layer. In contrast to high-cohesive particles, low-cohesive particles needed much shorter baffles.A soft-sphere discrete cohesive powder model was used to simulate the transverse mixing of particles in a rotary drum. Using this model, the effect of cohesion strength and baffle length was investigated. Mixing time （tR） and mixing entropy were used to characterize the mixing behavior. The results showed that increasing particle cohesiveness increases tR. Baffles enhanced transverse mixing, especially for high- cohesive particles. Moreover, the baffle length played a significant role on mixing. An optimized length of 0.50 （L/R） enhances transverse mixing for high-cohesive particles. Further increases in baffle length only decreases the mixing rate by impeding the surface flow layer. In contrast to high-cohesive particles, low-cohesive particles needed much shorter baffles.

Using the discrete element method to assess the mixing of polydisperse solid particles in a rotary drum

Despite the wide applications of powder and solid mixing in industry, knowledge on the mixing of polydisperse solid particles in rotary drum blenders is lacking. This study investigates the mixing of monodisperse, bidisperse, tridisperse, and polydisperse solid particles in a rotary drum using the dis- crete element method. To validate the model developed in this study, experimental and simulation results were compared. The validated model was then employed to investigate the effects of the drum rotational speed, particle size, and initial loading method on the mixing quality. The degree of mixing of polydis- perse particles was smaller than that for monodisperse particles owing to the segregation phenomenon. The mixing index increased from an initial value to a maximum and decreased slightly before reaching a plateau for bidisperse, tridisperse, and polydisperse particles as a direct result of the segregation of par- ticles of different sizes. Final mixing indices were higher for polydisperse particles than for tridisperse and bidisperse particles. Additionally, segregation was weakened by introducing additional particles of intermediate size. The best mixing of bidisperse and tridisperse particles was achieved for top-bottom smaller-to-larger initial loading, while that of polydisperse systems was achieved using top-bottom smaller-to-larger and top-bottom larger-to-smaller initial loading methods.

Microfluidic dual loops reactor for conducting a multistep reaction

Precise control of each individual reaction that constitutes a multistep reaction must be performed to obtain the desired reaction product efficiently. In this work, we present a microfluidic dual loops reactor that enables multistep reaction by integrating two identical loop reactors. Specifically, reactants A and B are synthesized in the first loop reactor and transferred to the second loop reactor to synthesize with reactant C to form the final product. These individual reactions have nano-liter volumes and are carded out in a stepwise manner in each reactor without any cross-contamination issue. To pre- cisely control the mixing efficiency in each loop reactor, we investigate the operating pressure and the operating frequency on the mixing valves for rotary mixing. This microfluidic dual loops reactor is integrated with several valves to realize the fully automated unit operation of a multistep reaction, such as metering the reactants, rotary mixing, transportation, and collecting the product. For proof of concept, CdSeZn nanopartieles are successfully synthesized in a microfluidic dual loops reactor through a fully automated mukistep reaction. Taking all of these features together, this microfluidic dual loops reactor is a general microfluidic screening platform that can synthesize various materials through a multistep reaction.