(589c) A Numbering-up Strategy for Scale-up of Slug Flow Cooling Crystallization Process

Microdevices gained interests not only from academic investigations but also from chemical and pharmaceutical industry. When two mutually immiscible fluids are simultaneously fed into a microchannel, various flow patterns such as annular, dispersed and slug flows are generated as to the design and operating conditions. Among these, slug flow, also called Taylor flow or segmented flow, is especially attractive in a broad range of applications, due to its narrow residence time distribution and large interface area per fluid volume. In addition, rapid mass transfer between two phases is achieved because the liquid interface is constantly renewed by the circulation flow inside the slug. These characteristics of slug flow in microdevices can bring benefits to reaction and separation processes. For example, slug flow crystallizers have been reported to narrow size distribution, minimize agglomeration, and increase yield. Despite these advantages, the low throughput of microdevices remains a challenge for practical application, which can be addressed by scale-up strategies such as numbering-up. The numbering-up of microdevices has been studied, e.g. for hydrogenation, fluorination, coupling reaction. However, to our knowledge, no numbering-up system has been reported for slug flow crystallization so far. In this study, for slug flow crystallization, a modular numbering-up system using a split-and-recombine-type fluid distributor (SRFD) was designed with the capability to control and monitor the uniformity of the slug flows. The modular design allows us to systematically scale the slug flow crystallization within n parallel channels (herein, n = 2, 3, 4, ···). The designed system was applied to slug flow cooling crystallization of succinic acid and it was experimentally shown that the slug flow distribution was very good with a standard deviation lower than 10%. The yield of the target succinic acid crystals in the numbering-up system was comparable to the results obtained in a single device demonstrating the feasibility of our approach. In addition, it was shown that the channel where the flow rate shift occurred due to blockage could be accurately identified on the basis of the ratio of the change in the measurements of two pressure sensors installed in the SRFD. The results of this study demonstrated that stable slug flow crystallization operation is possible in the numbering-up system.