It’s a time-worn dilemma for many industrial, research, and environmental cleanup efforts: how to efficiently filter particles out of liquid slurries to keep unwanted solids or chemicals from downstream processes. Or conversely, how to separate the right particles for specific treatment or processing. In some settings, chemical separation methods are used, but this creates additional process streams or byproducts that must also be treated. To separate particles by size, liquids and very small solids are typically pushed through filters that quickly clog and need to be rinsed or replaced. This clogging problem is an expensive and rate-limiting step for operational efficiency.

The patent-pending Mesofluidic Separator—Clog-Free Filtration System developed by PNNL researchers could eliminate the filtration bottleneck for a host of applications including fracking sands, nuclear waste cleanup, waste water treatment, food processing, microplastic removal, marine species monitoring, and many others. Unlike current filters that often plug in days if not cleaned, the Mesofluidic Separator—Clog-Free Filtration System is projected to operate for more than three years without a substantial drop in flow rates.

From the outside, the device resembles a hollow hockey puck with slats running through it. But the slats are actually row after row of very tiny, thin individual posts. Each row of descending posts is slightly offset from the row above it. As a slurry flows through the device, small particles glide along between the posts, but larger particles “bump” into them. These larger particles follow the flow fields created by the posts, cascading in the designed direction and eventually emerging out of the intended side of the device—the express lane. An express lane configuration, comprising approximately 15-20% of the cross section, removes large particles from the slurry. The device works in both horizontal and vertical mode for top-down and bottom-up flows.

In PNNL tests at various scales with several different solid-liquid mixtures, the system quickly and successfully separated larger particles from smaller ones. Full-scale tests for 300-micron particles worked at a rate of 90 gallons per minute—the optimal flow for waste treatment operations. A full-scale system can separate particles in the millimeter to submicron range.

Applicability

The Mesofluidic Separator—Clog-Free Filtration System is suitable for industries ranging from food processing to advanced manufacturing, for environmental cleanup applications involving chemical waste treatment, and for research applications including, aerosol science, supercritical fluids, and oil and gas extraction, to name a few. It can be designed to separate and collect particles in the millimeter to submicron range, depending on the desired size range.