The main cooling requirements in the power plant occur in the condensation of steam in the turboine condenser. Due to the condensation of the steam, the water suddenly assumes a very reduced volume. A strong pressure loss, far below the air pressure, is the result.
The temperature gradient increases in relation with the thermal efficiency (Carnot formula). For the efficiency of the steam power plant this effect is very important. A typical main cooling water system consists of the main condenser, cooling tower, coolant discharge, cooling water pump and cooling water treatment plant. The cooling water is extracted from a river and treated in the treatment plant. Subsequently, it is routed into the cooling circuit. The main cooling water pumps convey it to the main condenser. The condenser is a heat exchanger with integrated pipe system, through which the cooling water flows. The water steam from the trubine condenses on the "cold" pipewalls of the condenser. The condensation heat is transferred to the cooling water. Here it effects the cooling and condensation of the steam, which leaves the low pressure part of the turbine. The warmed cooling water subsequently reaches the cooling tower. In the cooling tower, often more than 100 m in height, the water is cooled. For this purpose it is routed to a height of between 10 and 20 m over distribution pipes into the cooling tower from where it trickles through a plate system (trickler installation) to the bottom against the rising air current. In this process, a small portion evaporates and escapes as vapour into the atmosphere. The remaining cooling water is collected in cooling tower basins. From here it can be rerouted into the extraction waters (discharge operation) or else it is again rerouted into the cooling circuit. The volume of cooling water of a coal power plant is substantial: per 100 kW power plant performance ,approximately 3 - 4 m3 water per second flow through the condenser (>600MV requires approximately 75 000 m3/h cooling water. |
 |
