Energy- and Resource-saving Separation of Unwanted Particles/Aerosols from Air Streams
Energy-efficient air purification process using supersaturation
Common processes for separating particles or aerosols use filter systems, inertial separators and Venturi scrubbers, or work electrostatically by charging aerosols and discharging them by means of electric fields.
All the above mentioned processes have specific disadvantages. Be it that filters have to be cleaned or replaced continuously, that the processes are energetically very unfavorable, that high investments have to be made or that these processes are not suitable in principle - as e.g. in the case of adhesive aerosols.
At the University of Stuttgart, a plant concept has now been developed for a new separation process which avoids the above-mentioned disadvantages and, in particular, demonstrates better energy efficiency compared with the processes normally used. The innovative method makes partial use of so-called heterogeneous condensation. In this process, water condenses onto the particles, multiplying their size. This process takes place when the moist air stream is supersaturated. Supersaturation is achieved by accelerating an air flow in a nozzle due to mass conservation, thereby lowering the pressure. If the air flow is not sufficiently humid, water can be added as an alternative.
The resulting water droplets, which contain the aerosols, are specifically deflected in an inhomogeneous electric field due to the dipole moment of H2O, collected and separated from the air stream. Since water is electrically neutral despite its partial charge shift, virtually no discharges occur during this process, which means that the energy required to maintain an electric field is considered negligible. The energy-efficient air purification process described can also be repeated several times.
Subsequently, in a downstream diffuser, the pressure of the purified gas stream is increased and the velocity is lowered when the flow resistance is low. This compensates for a lower pressure drop, making the process very energy-efficient.
- Energy-efficient aerosol separation
- Separation of sticky aerosols (e.g. in biomass flue gas)
- Capture of ultrafine aerosols
- No mechanical filtration systems required
- In arid regions, the process could also be used for water extraction
Fields of application
ll technical processes that ideally generate moist exhaust air laden with undesirable particles, e.g. in power plants or other combustion processes. The particles can also be in the form of solid aerosols, for example.
The application in biomass power plants is considered particularly suitable, since biomass basically has a water content, i.e. it carries the water required for the innovative process. If the legal requirements for cleaning such flue gases were to be tightened, the innovative process could be used to replace or retrofit existing particulate filters.