EDropSep

Droplet separators are an integral part of many HVAC systems and in process engineering. Optimization is required for existing droplet separation systems especially due to the high pressure loss forcing up the energy demand for transporting the air through the system. What also contributes to this issue: The emission limits for air purity are continuously decreased; thus, the pressure losses of existing droplet separators are increased even more and the droplet separators reach their design limits.

In the EDropSep research project, a novel separation concept is developed which allows for a higher energy efficiency in the separation of droplets with diameters in the lower µm area.

The operating principle is called dielectrophoresis and is based on the force that has an effect like water on dipole molecules in inhomogeneous electrical fields. This force results from the field gradient of inhomogeneous E-fields. This field gradient leads to varyingly strong field forces on the centers of electrical charges, due to the distance of the atoms in the dipole molecules. The difference of these field forces leads to a resulting force which, in turn, results in an acceleration of the molecules to a higher field force. A prior charging of the droplets, common in conventional wet-working electrostatic precipitators, is not required.

To be able to use the operating principle of the droplet separation, an annular gap geometry is constructed out of the cylindrical inner electrode and outer electrode. The feed material (i.e. the air loaded with droplets) is led in the annular gap geometry. The inner cylinder is the collecting electrode, the outer cylinder is the counter electrode.

In CFD and ANSYS Fluent simulations, the feasibility was already theoretically proven and the high energy saving potential of up to 80 % versus cyclone separators was shown.

Now the physical operating principle, the relevant parameters and their sensitivities are explored in more detail in a test bench which was specifically designed for this purpose. To validate the simulations of the droplet movements (trajectories), a planar electrode geometry with an inhomogeneous E-field is used in the first project phase. This planar electrode geometry allows for an optical access via transparent side panels. With imaging measuring methods, the deflection of the droplets in the E-field can be exactly determined.

Based on these findings, a prototype of the novel droplet separators is constructed, built into the test bench and tested.

If the high efficiency of the novel droplet separator, calculated in simulations, can be verified in the EDropSep research project and technically realized in the prototype, the development of the novel droplet separator will follow. The mature separator could then make a major contribution to an increase in the energy efficiency of the droplet separation in the lower µm area as well as to the compliance with the emission limits for air purity in several industrial facilities.

• 04/2021 – 04/2023 (25 months)

• Institute of Power Transmission and High Voltage Technology (IEH), University of Stuttgart
• MF Microfilter GmbH, Neuenstein, Germany
• Sibel Elektronik GmbH, Kreuztal, Germany

The EDropSep project is funded by the ZIM program (grant number KK5010903BR0) via the German Federation of Industrial Research Associations (AiF). IGTE would like to sincerely thank for their support.