Deterministic ratchets for larger scale separation of suspensions

Introduction

A sustainable process takes care of (aqueous) waste streams. Separation of the ingredients and particulates from the liquid makes valuable ingredients available and gives an opportunity for water reuse. The regeneration process should meet the following criteria: low consumption of energy, water and chemicals.

A theoretical research showed that deterministic ratchets are a promising method to fractionate suspensions. Simulations and experiments using micro ratchet devices have already provided proof of principle for the technology itself and guidelines for large-scale application. In the movie below you see a simulation of particle movements in one periodic array of a ratchet.

Deterministic ratchets are a very new class of separation devices. They consist of periodic arrays of obstacles, spaced such that components having a minimum size are forced from their streamlines. The slightly tilted arrangement gives a larger particle a slight off-set from each streamline at each row of obstacles, which after several rows gives a microscopic translation of particles. An experimental result of particle displacement is given in the figure below.

Aim of the project

The aim of this project will be to investigate ratchet technology for large-scale application and test it for particulate removal and possibly also for ingredient fractionation from aqueous streams.

Approach

New ratchet designs will be designed and experimentally evaluated on small and larger scale with ‘model’ laundry suspensions. Different manufacturing methods allowing low-cost-up-scaling will be reviewed. Specific attention will be paid at operation of ratchets at high particle concentrations. The particle trajectories in the ratchet devices are visualized by a microscope equipped with a high speed camera.

Acknowledgements

This project is in collaboration with Wetsus, Leeuwarden.