Novel static mixers for surge dampening

The usual goal of a static mixer is to enhance radial mixing. The intended output is a mixture that is uniform in composition (or temperature) across the exiting stream. Time-wise variations, corresponding to axial variations in tube flow, may still exist. Typically, the better a static mixer at radial mixing, the less it dampens axial variations. Relatively few static mixers have a design intent to eliminate axial composition variations. A recent paper by researchers at Air Products coined the term “temporal mixing” and introduced the concept of a “flat” residence time distribution that outperforms a stirred tank when the input disturbance in concentration is periodic. This concept has been extensively utilized to damp surges in pressure swing absorption processes. A comparison of these approaches is given along with the extension to surge dampening combined with chemical reaction. The combination of combined surges in flow rate and concentration is also considered. Pertinent applications include cyclical process in general and those with a strong diurnal variation in demand such as potable water and waste water treatment systems.