Page 9 - Case study: Fine dust filtration in Stuttgart, Germany

Key features and design

The pilot project is designed to investigate whether the technology can be used to reduce the local
fine dust pollution and included 17 x 3 Filter Cubes measuring 3.6 meter in height, and these Filter
Cubes were equipped with fine dust particle filters and energy-efficient fans.

It is assumed that the combination filter elements will have to be replaced approximately every 30
days during the pilot project. The exact replacement intervals will be determined within the project
and defined on the basis of the requirements for proof of effectiveness.

On polluted days, a running time of 12 hours is planned. With a consumption of approximately 1.5
kW and an assumed electricity price of 20 cents per kWh, this results in energy costs of only 3.60 €
per day and column.

Filtration Technology:

• Filter columns consist of a number of Filter Cubes stacked on top of each other (e.g. Figure 2
includes two columns each consisting of 3 cubes)

• A filter column with 3 Filter Cubes is able to clean 14,500 m³ of air every hour.

The technology was developed and integrated to a newly developed combifilter medium which
has a filter layer that retains fine dust particles. This also includes additional activated carbon
layers with large surface area to effectively adsorb NO2.

• For the particle filtration layer, an electrically charged filter medium, known as electret medium,
was used for the particle filtration. The deposition of NO on the activated carbon is carried out
2
via the following parallel adsorption mechanisms at the surface of the activated carbon:

o Physisorption: physical adsorption of NO
2
o Chemisorption: chemical binding of NO in the form of HNO
2 3

o Catalytic reduction of NO to NO and CO as well as to N and CO .
2 2 2
Both NO2 and particle filtration technologies are characterized by a particularly low drop in pressure
and therefore able to efficiently clean the air while using a low amount of energy.

Smart Technology:

• The filter column contains several sensors for monitoring ambient conditions such as e.g.
temperature, humidity, and air quality. These measurement data are currently used to control
how the system is used, but with more data and insights, there will be more applications that
can emerge from data usage.

Fine dust filtration - Stuttgart, Germany 3