Simplified description and technological diagram of the electrical energy generation process
The electrical energy generation process boils down to the following energy conversions: fuel chemical energy into heat; heat into mechanical energy; mechanical energy into electrical energy. The process of electrical energy generation can be divided into several stages.
Fuel treatment
The coal transported to the power plant by rail is unloaded by wagon tipplers (1) and by means of Belt conveyors the coal is transported to coal bunkers (3) or the coal storage site (2) where it is blended.
Boiler installations
The notion ‘boiler installations’ refers to a group of facilities used for steam generation by means of converting fuel chemical energy (in our case coal) into heat. This energy is passed to water and steam. The heat exchange in the boiler is carried out by means of heating surfaces: radiant (heat exchange by way of radiation) and convective (heat transfer from the flue gases).
Combustion process
For correct combustion process one needs to supply appropriate volume of coal and air of suitable parameters. The air is fed to the boiler by means of air ventilators (11) after preheating in the rotary air pre-heaters (10). The coal ground in the mill is fed with the air (in the form of coal-air mix) through pulverized coal burners to the boiler (5) where it is fired. Flue gases produced during the combustion process are directed by means of ventilators to the stack (14) or through FGD installation auxiliary ventilators (28) to the flue gas desulphurizing installation (29). Purified flue gases are emitted to the atmosphere through the cooling tower (26).
Steam generation process
The process is carried out in three stages: water pre-heating, vaporization and steam super-heating. Water from the feed water tank flows to the feed water pump suction manifold (25). These pumps pump the water through the high-pressure pre-heater (23) and water pre-heater (9) to the boiler drum and later to the evaporator (6). The generated steam flows from the drum to the primary pre-heater (7).
Conversion of heat into mechanical energy
In order to convert heat into mechanical energy a three cylinder reheat condensing turbine is used. The turbine comprises of three basic parts: high-pressure, medium-pressure and low-pressure part with two outlets. Primary steam is directed onto the vanes of the turbine high-pressure part rotor (15). Then the steam is returned to the boiler to the secondary super heater (8) where the seam is superheated again and then directed via a pipeline to the medium-pressure part (16). The superheated steam works in the turbine medium-pressure part and then it is directed to the low-pressure part (17). In the low-pressure part the steam is divided into two streams and then it is condensed in the condenser (20). Condenser cooling water is pumped through the cooling water pump (27). These pumps are located in the central pump station building from where the water is pumped through the condenser to the cooling tower (26). The water is cooled down in the cooling tower and returned to central pump station suction tank. Condensed steam in the condenser i.e. the condensate is pumped by means the condensate pumps (21) through the low-pressure pre-heater (22) to the feed water tank (24).
Conversion of mechanical energy into electrical energy
The turbine rotor is directly connected by means of a coupling with the alternating current generator rotor (18). The generator is connected by means of busways with the power unit transformer (19). The unit transformer increases the generator voltage to the transmission line voltage (30).
Simplified technological diagram of the electrical energy generation process
English
Polski
