(83e) Performance Improvement of in-Line Flow Chemical Reactors By Modifying Injector Geometry

Continuous-flow or in-line reactors/mixers are ubiquitous in food, beverage, chemical, pharmaceutical, petrochemical, biotechnology, and other industries. They are used to mix two separate fluid streams with the aim to either get a homogeneous mixture or attain a chemical reaction. One of these streams is generally brought in through a “Stinger” or an additive injector which is oriented perpendicular to the direction of the main flow in the reactor and has a circular cross section. This leads to a flow structure which is similar to the canonical case of crossflow around cylinders with flow separation and vortex formation downstream. This work utilizes a combination of computational and experimental tools to study the aforementioned flow around the injector and its influence on the residence time of the additive. It is found that the additive gets “trapped” in a recirculation zone if its injection velocity is low and the injector holes are aligned parallel to the axis of the main reactor pipe. This problem can be solved by (i) increasing the injection velocity, or (ii) orienting the injector holes at an angle to the main pipe axis; such that the additive is injected away from the downstream vortices. Some results are also presented for a novel injector design with a streamlined cross section to delay the onset of flow separation. These results are important with regards to setups where unintended long residence times can cause promotion of undesirable secondary reactions. “Fouling” or deposition of gels/solids is a common symptom of such reacting flows with issues in mesoscale mixing.