Dry Coolers for Thermal Power Plants (Air Cooled Units)

Dry Coolers for Thermal Power Plants (Air Cooled Units)

After the turbine in a thermal power plant has done its work, the exhaust steam (low pressure saturated steam at about 40-50°C) needs to be condensed into water (condensate) before it can be reintroduced into the boiler cycle. Traditional wet-cooled units use cooling water (e.g., cooling tower circulating water) to condense the steam, but the water consumption is huge; air-cooled units use dry coolers to condense the exhaust steam directly/indirectly through the air, resulting in significant water savings (up to 70%-90%).

Key features of dry cooler in air-cooled units

Significant water-saving advantages:

Only a small amount of water is needed for system replenishment (e.g., evaporation of circulating water, leakage replenishment), compared with wet-cooled units (about 1.5-3kg of water consumption for each degree of electricity), the water consumption of air-cooled units can be reduced to 0.1-0.3kg/degree, which is suitable for water-scarce areas such as Northwest China, North China, and so on.

Highly affected by ambient temperature:

In summer high temperature (e.g. above 35℃), the heat absorption capacity of air decreases, and the cooling efficiency of dry cooler decreases, which may lead to the increase of turbine exhaust pressure (decrease of vacuum), and the unit power generation efficiency decreases (about 2%-5%);

In winter low temperature, the efficiency is high, but it is necessary to prevent freezing of the tube bundles (by adjusting the fan, heating the steam, and other measures).

Layout and energy consumption:

Direct air-cooled dry cooler (ACC) is usually located on the top of the plant, which saves land but the energy consumption of the fan is higher; indirect air-cooled dry cooler can be used with natural ventilation cooling tower, which consumes less energy but occupies a large area.