Caterpillar Microstructured Mixer-reactors

Caterpillar microstructured mixer-reactors owe their name to their total micro-channel shape, characterized by alternately up- and down-lifting ramps at the floor and ceiling of the fluid path, which as a whole resemble the fringes along the body 

The caterpillar micromixer consists of a number of serial oriented unit cells that repeat and complete the same type of mixing process. Eight such cells are serially combined in the standard version that is commercially available. Dependent on the mixing problem, however, more or less units may be appropriate, which, especially for production, needs to be optimized to reduce the pressure drop to the limit really needed and for efficient power dissipation. For this reason, caterpillar devices (600 pm width and depth) with 0, 2, 4, 6, and 8 mixing cells have been manufactured to test mixing efficiency by a standardized protocol (Fig. 6.3) ]27]. 

There are two ways for scale-out with caterpillar mixers. One is to enlarge the mixing unit cell, i.e., the corresponding channel width, depth and length, while keeping the width-depth length ratio constant, i.e., maintaining the type of ramp 

For better visualization, the end of the units is marked by a black line [27]. From there, a simple unstructured channel follows until the outlet connector. The combined length of structured and unstructured sections is always kept the same. Dotted lines show the respective increase in mixing length for the mixer devices from left to right. 

These mixers have been tested for their mixing efficiency (Fig. 6.5) [27]. 

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Reactor type Caterpillar mini mixer-tube reactor, 1st generation Microstructure in one plate initial depth maximum depth 600 pm 850 pm... 

The Caterpillar micro mixer is an example of a simple, pilot-sized micro mixer-tube reactor that has an internal microstructure with a ramp-like shape inducing recirculation flow patterns, whereas the overall channel structure can be kept fairly large. The volume varies between 1 L/hr to several hundred liters per hour. Several hundreds of precision-engineered, star-shaped platelets can be stacked, and the flow can be distributed. 

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