Optimization of Spray Nozzles in Flue Gas Scrubbers

Project Number 230

In power plant technology modern gas scrubbers are used for flue-gas desulphurisation of coal or heavy fuel fired plants to absorb pollutants into aqueous solutions. The scrubbing liquid is atomised with the help of numerous nozzles. Different nozzle types like helix, hollow and full cone nozzles are used for this process. In this connection the fluid dynamics indicates an optimisation potential. With a certain nozzle alignment in several different levels a spray overlapping can be achieved. The effect of secondary dispersion that occurs at the overlapping of sprays during atomisation in the flue-gas scrubber can be effectively used to improve atomisation efficiency and mass transfer at the absorption of the flue-gas.

Up to now secondary dispersion was neglected in modelling of flue-gas scrubbers and for this reason it could not put into practice. The described effect of secondary dispersion is not noticed at research scrubbers though technological reasons. It is therefore necessary to give plant manufacturers and operating companies support with the help of adequate and robust CFD-simulation to profit from this effect.

This should be achieved with the development and optimisation of the simulation program developed in the research and development project "REA-Fluiddynamik" (202) and attendant experimental measurements at a pilot plant designed especially for that reason.

The aim of this research project is to achieve a reduction in energy demand with the same degree of absorption. In addition the reduction of SO2-emission can be increased with the same energy demand. It can be necessary through burning low calorific coal respectively sulfur-rich coal as well as a change in existing regulations like the directive 2002/80/EC of the European Parliament becomes effectively. The limit for new plants and old plant with additional biomass combustion is 200 mg/Nm3 SO2 . The limit for the biomass gas component is 50 mg/Nm3 SO2. The combined limit is between 150 and 185 mg/Nm3 SO2.

The project is carried out from July 2002 to December 2004 by the Chair of Environmental Technology of the Dortmund University (person in charge: Dr. Joachim Neumann). The project is accompanied by a working group of the Working Panel "Flue Gas Cleaning Technology".