Hybrid cooling tower
A hybrid cooling tower is the design of a cooling tower that combines the advantages of wet and dry cooling towers . The heat of condensation is dissipated to the environment via a circuit through the cooling tower. The steam that escapes is greatly minimized by dry cooling .
construction
The hybrid cooling tower is built on two floors in a cylindrical shape with a truncated cone-shaped chimney. In the lower part of the hybrid cooling tower is the wet section level with classic cooling installations such as cooling installation made of plastic, water distribution with spray fittings and the drip catcher. The upper level of the hybrid cooling tower, the so-called dry section, is used exclusively for steam drying and only contributes a small part to the total cooling capacity of the hybrid cooling tower.
Wet part
The wet part of the hybrid cooling tower consists of water distribution, cooling components and a drip trap. The warm cooling water conveyed by the main cooling water pumps reaches the water distribution level via the riser duct (s) and is trickled out there. Fans convey cold air into the interior of the cooling tower and thus ensure cooling (evaporation and convection) of the cooling water raining down. The cooling installation can be bypassed via the 100% bypass during start-up and shutdown processes, as well as during low-load operation in winter. Sound baffles are attached to the suction side as well as behind the drip catcher in order to reduce the sound emissions. The wet part of a hybrid cooling tower corresponds to the classic design of a normal natural draft or cell cooling tower.
Dry part
In the dry part of the hybrid cooling tower (upper level) heat exchanger packages (finned tube bundles) are arranged. Warm cooling water (approx. 20% of the main cooling water mass flow), which is taken directly from the riser shaft with pumps, flows through these. The fans in the dry area draw in cold air from outside. This air is passed through the finned tube bundle, heated and blown into the upper area of the cooling tower. The moist, saturated cooling tower swaths are dried by the supply of warm air. This means that the supply of warm air shifts the saturation point into the unsaturated area and the visible cooling tower swath disappears. The cooling water passed through the finned tube bundle of the dry section is directed into the wet area and also trickled there. Since the elements of the dry section are operated in a frictional connection, air and inert gases must be sucked out of the upper water chamber by evacuation pumps. In order to ensure good heat transfer on the water side, the pipes, as in the condenser, are continuously cleaned by sponge rubber balls ( taprogg system ).
Operating mode
Three operating states are possible for a hybrid cooling tower. The first operating state is bypass operation when starting up or shutting down the power plant or the hybrid cooling tower. The entire cooling water is passed through the bypass and reaches the cooling tower base without being cooled. Wet and dry parts are out of order. The second operating state is pure wet operation. The entire cooling water mass flow is trickled into the wet section of the cooling tower, the dry section is out of operation (fans dry section off and no flow through the finned tube bundle). The cooling tower plume is not dried and is therefore usually visible. If the dry section is also put into operation, it is called hybrid operation. The visible cooling tower plume is reduced by the supply of warm air.
Usually at night or in damp, cold weather, the vehicle is driven in pure wet mode, and in normal ambient conditions in hybrid mode.
By regulating the speed of the fan motors and switching individual cooling tower areas (partial areas) on and off, very fine control of the hybrid cooling tower and thus adaptation to the required operating mode is possible. In winter, when the ambient air temperature is cold, or when district heating is decoupled, the fan speed is reduced to prevent the cooling tower from freezing. The decommissioning of partial areas and the bypass operation also ensure the necessary reduction in cooling capacity.
Advantages and disadvantages
advantages
- Low construction height (approx. 50–65 meters) compared to a natural draft wet cooling tower (100–200 meters)
- Avoidance of vapor plumes and the associated change in the microclimate, associated with an improved ability to approve
- Optimization of the cold water temperature and the condenser pressure as well as reduced own requirements for pure wet driving
- Good controllability and adaptation to required operating modes
- Round cooling tower to generate a compact column of steam with a high exit speed, depending on the size, is approx. 6 m / s for wet operation, 11 m / s for hybrid operation
disadvantage
- High investment costs due to a very high proportion of mechanical components. The costs are around five to eight times that of a natural draft cooling tower of the same capacity.
- High internal electrical consumption and thus a marked reduction in power plant efficiency (e.g. the hybrid cooling tower of the 1640 MW coal-fired power plant Moorburg (built in 2011) requires approx. 10 MW el output. The hybrid cooling tower 1300 MW nuclear power plant Neckarwestheim (block 2) from 1988 requires approx. 25 MW el power.)
- High noise emissions due to the operation of the fans and a high rain density. Compliance with acoustic requirements is only possible through the installation of extensive noise protection measures.
distribution
Hybrid cooling towers are so far not very common. The Altbach / Deizisau power plant and Block 2 of the Neckarwestheim nuclear power plant were the first power plants in Germany to be equipped with hybrid cooling towers.
The coal-fired power plant Moorburg in Hamburg also has a hybrid cooling tower.
RWE planned to equip the intended new construction of the BoAplus block in the Niederaussem power plant with a hybrid cooling tower. These plans were discontinued in April 2019.
The planned, but currently suspended, new buildings for the Swiss nuclear power plants Niederamt , Beznau 3 and Mühleberg 2 should also have hybrid cooling towers.
In the RAG mines on the Rhine and Ruhr, hybrid cooling towers were sometimes used in combination with cell coolers for the cooling capacity for ventilation .
| fuel | Power plants with hybrid cooling tower |
|---|---|
| Hard coal | Moorburg coal-fired power station |
| Hard coal | Altbach / Deizisau power plant |
| uranium | Neckarwestheim nuclear power plant |
Web links
Individual evidence
- ↑ Hybrid cooling tower for Moorburg approved! City of Hamburg Authority for Urban Development, December 23, 2010, accessed on May 22, 2012 .
- ↑ BoAplus stays cool with new cooling tower technology. RWE, accessed on May 22, 2012 .
- ↑ For Boaplus for Kölner Stadt Anzeiger, April 26, 2019
- ↑ Axpo and BKW are planning replacements for Beznau and Mühleberg