The cooling tower of a large power plant is generally its most visible part. A natural draft tower for a 1600 MW plant is quite tall and its plume is visible from many kilometers around. An induced draft cooling tower for a similar power plant consists of many cells arranged in blocks. Such a cooling tower requires a very large ground surface and is energy-consuming. Plume visibility and generated noise have adverse environmental effects, which can be corrected using a plume abated cooling tower.
The Moorburg cooling tower, a huge project in Germany with one cooling tower for two units of 800 MW each, cumulates the advantages of different systems for an environmentally friendly purpose: limited visibility (small total height), limited ground surface, limited power consumption, low plume, and low noise emission.and noise reduction systems.
The owner's first idea was to build a classical wet cooling tower above the river. The tower operation was in open circuit mode. This project was finally rejected. The tower was complicated, and difficult to run with the variation of the river water level. The visibility constrain was such that a natural draft CT could not be built in view of its height and the emitted plume. A classical hybrid cooling tower required too much space to avoid the recirculation and could not fit in the allocated space. The solution that finally came as evidence was a round hybrid cooling tower. In order to reduce the power consumption, a fan assisted natural draft cooling tower was selected and as far as the noise limit is concerned, the tower would have to be completely protected with noise attenuators.
The concrete shell has an hyperbolic shape. The total height is limited to 60 m to remain smaller than the boiler building. The bottom of the shell is perforated by 36 holes for the fans of the wet part. Above, at dry level, there are 36 square holes in the shell which include noise attenuators. The cooling tower is divided into two independent halves corresponding to one unit each. It can be completely isolated by quarters, air and water. The water flow repartition between the flumes was calculated with CFD tools so that the design of the elbows could guarantee an even water supply to the distribution. To avoid the plume, the quality of the mixing between the oversaturated air coming from the wet part and the dry air coming from the dry part wasssential. Many CFD calculations were done in parallel with model tests to optimize the design.