Conventional steam power plants generating both electricity and heat are called backpressure power plants as a distinction to condensing power plants, which are generating only electricity. In a conventional condensing power plant, high-pressure steam generated in a steam boiler, the so-called live steam, is lead through a steam turbine, where the steam expands and is taken out of the turbine to a condenser at a low pressure. The remaining heat energy in the steam is wasted into the cooling water or cooling air.

 In a backpressure turbine the steam is taken out of the turbine at a higher pressure than in a condensing power plant and the steam is used for heating purposes as shown in the following figure. 		 
 

[enlarge]
Figure 1. Backpressure Power Plant.

 

Backpressure steam can be used directly as process steam in industrial applications such as paper machines or the steam can be condensed in heat exchangers, whereby the heat is transferred to the heating media such as district heating water.

Depending on the above mentioned application, the backpressure power plants are divided into the following two main groups:

 ·                     Industrial backpressure power plants
  ·                     District heating power plants

 

The level of backpressure depends on the required heating temperature and is generally higher in industrial applications than in district heating power plants. The differences of the two backpressure power plant groups are described in the following.