Influence of Buildings on the Discharging of Flue Gases via Cooling Towers and Additional Considerations for Stacks

Project Number 262

In many cases the discharging of flue gases via cooling towers has proved itself both under ecological and economic criteria and is carried out at a number of power plant locations. Also plannings in the future will take this option into consideration.

The dispersion model (to evaluate the immission additional loading caused by a power plant) of the new Technical Instructions on Air Quality Control (TA Luft) does not include a consideration of the influence of buildings regarding the discharging of flue gases via cooling towers. As according to the Technical Instructions on Air Quality Control this influence is to be considered, however, the operators, in whose plants flue gases are discharged via cooling towers, would be dependent on the engagement of experts in many cases. In such cases typically expensive wind tunnel investigations were carried out in licensing procedures, resulting in delays of these procedures. Dependent on the experts chosen different approaches would be used which could result in an increase of objections and therefore also in delays of the licensing procedures.

Due to legal security the existence of a uniform, generally accepted model is necessary. Therefore, the Technical Committee Air Pollution and Noise Control suggested the realisation of the elaborated research project.

In a preliminary project (VGB no. 242) it was examined if – based on available results of wind tunnel examinations and on new examinations – sets of parameters for amplification factors for the calculation of the additional immission loading of plants could be developed so that in the future wind tunnel examinations could be substituted. The project results showed that the investigations for determining realistic sets of parameters would become too extensive. Choosing one “most pessimistic” standard parameter set would result in an unacceptable overevaluation of the additional immission load.

In this project a programme – developed by the federal environmental agency – considering the influence of buildings shall be examined with the objective of testing its applicability for cooling towers, also beyond the application range of TA Luft (height of emission source > 1.2 x height of relevant building - in such cases in principle an expert had to be employed). The discharging via stacks shall be examined, too.

Should the results show the applicability of the programme in the framework of licensing procedures for power plants discharging flue gas via cooling towers, VGB will make efforts to ensure the acceptance of this approach on the part of the authorities. Experts of the federal environmental agency and the immission committee of the federal states will be members of the panel (installed by VGB TC Air Pollution and Noise Control) overseeing the project.

The project will be carried out by the “Arbeitsgemeinschaft für Umweltmeteorologie und Luftreinhaltung – Bahmann & Schmonsees GbR”. Results are expected by summer 2005. The project is accompanied by the Technical Committee "Air Pollution and Noise Control".