“KOSOVO” Dispersion Calculations
Date: 07.05.2007
Page 10
5 Calculation of the Additional Pollutions In Accordance With the Technical Instructions on Air Quality The dispersion calculations for gases and dusts were performed using the Lagrange particle model of VDI Guideline 3945 Sheet 1 (LASAT: AUSTAL 2000 Version 2.3.6 WI-x) in accordance with Appendix 3 of the Technical Instructions on Air Quality. For the data input and presentation of the results the “WinAUSTAL2000” program (Version 1.8.4) from engineering consultants Lohmeyer GmbH & Co. KG in Karlsruhe was used. The dispersion model LASAT (Lagrange-Simulation of Aerosol-Transport) calculates the dispersion of pollutants in the atmosphere on a local and a regional scale. Emitted particles (gases) are followed on their way through the atmosphere. The particles are following the mean wind flow, turbulence and an additional flow. With the additional flow the sedimentation and deposition can be computed. The model used, contains a boundary layer model for flat areas and a diagnostic wind-field-model, which simulates the impact of uneven areas on the wind-fields. Emission sources can be defined as point-, line, area-, or volume-sources. The plume rise is includes in the model and comprises the aerodynamic plume rise and the plume rise due to buoyancy. Therefore also the discharge of exhaust gases via cooling towers can be simulated. The model can be adjusted to site specific conditions by adjusting surface parameters (surface roughness) and terrain characteristics. The impact of buildings like cooling towers on the air flow pattern und dispersion is simulated with a meteorological pre-processor which includes a diagnostic wind-field-model. The chemical transformation for NO oxidation to NO2 is taken into account in the model to evaluate the actual NO2-concentrations in the ambient air. Nitrogen oxides (NOx) emitted by burning fossil fuels consist largely of nitric oxide (90-95 % NO) and a smaller part of nitrogen dioxide (5 – 10 % NO2). After exhaust from flue the percentage of NO2 increases through oxidation of NO mainly by atmospheric ozone, oxygen and radiation. In this study the initial fraction of NO in the emission is assumed to be 90 % of the volumic rate of the NOx-emission. NO conversion is approximated via empirical relation from NO-lifetime measurements conducted at several power plants according to the VDI guideline 3782/1. For the determination of pollutant concentrations the assessment area is covered with a three-dimensional enumeration grid, where the particles are moving. Residence time and amount of particles give the concentration within the grid volume.
GfA Consult GmbH
Report No.: 40207-01.B01