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Another term mesoreactor has also been used to describe small channel reactors with channels on the order of 1mm in size. While lab scale mesoreactors offer flexibility, and tolerance to solids--as well as some of the engineered scalability, that increase in size comes at the costs of requiring much more reagent per experiment than small volume microreactors.
In both micro and meso reactors, the channel volumes are very small which means even at very high flow rates turbulent flow is impossible to achieve. Under laminar flow conditions, mixing is achieved by bends, or other directional impedance which cause a vortex to form in the fluid flow. These vortices allow independent streams of fluid to fold over on themselves allowing for mixing to occur via diffusion. Maintaining and understanding the mixing characteristics of microreactors is a critical aspect of scaling processes. Chemtrix KilowFlow® reactors scale directly from the Labtrix® up to 800X on mixing down to 1/100th second!
Solids, and gases can be handled in microreactors but careful attention must be given to how the process is designed to ensure success. At low net flow, solids may foul or settle in the reactor and cause blockage. Depending on pressures, gases may drastically displace the liquid inside the reactor and reduce residence times in an unpredictable manner.
With all static mixers, net process flow effects the way in which the material moving through the reactor are mixed and how well heat transfer can occur. Viscosity of the materials in the reactor can also create very high pressure drops. While pressure drop can be alleviated to some extent by splitting and recombining the flow in a wider channel, the overall pressure drop becomes a significant issue when the process becomes larger. Pumping systems, materials of construction, as well as control systems all need to be engineered to create a scalable process.
For rapid transition to industrial scales, Chemtrix Plantrix® and Protrix® reactors incorporate highly chemically resistant ceramic Silicon Carbide. This material is tolerant of the most aggressive acidic conditions, including Hydrogen Fluoride and fuming Nitric Acid--even at high heat. Utilizing 3M’s patented diffusion bonding process, the reactors use no cement or gasketing material to hold the plates together. The SiC material has 5X greater conductivity than Hastelloy allowing for uniform heat transfer.
Scalability with these reactors is similar to all Chemtrix products. As process scale and channel dimensions increase, the ability to duplicate results becomes more challenging. Protrix® reactors scale directly to the MR 555 platform (340X scale up) allowing the user to go from gram scale development to ton scale production faster than ever before.
Microreactors offer distinct advantages over conventional heat exchanged tubular mixers(static mixer) with respect to heat transfer. Utilizing a meandering path, that may be linear or may split and recombine, microreactors consist of very small channels that are surrounded by a heat exchanged surface. At lab scale microreactor channel diameters can be in the 10’s of microns, whereas at industrial scale the channels are typically 1-5 mm wide. Enjoying a 3-4X heat exchanged surface area to internal volume ratio advantage, microreactors are a much more efficient when heat transfer is a critical processing parameter. Moreover, service jacket flow can be tuned in order to improve efficiency over and above simple increase in jacket volume. The Labtrix® series of lab scale micro reactors are so small that a simple peltier/heating element can be used to effect heat transfer in a highly scalable manner. With reactor volumes of 1uL up to 25 uL these reactors development of continuous processes on milligrams of material. As a result conventional tubular flow chemistry systems, while excellent for developing chemistry in the lab may offer 10-50X scale-up factors, whereas carefully designed Chemtrix Microreactors offer scalability factors of up to 10,000X.
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