The following article is intended to provide to all interested people the visual information about how the equipment of a thermal power station is arranged inside. This article describes a relatively new type of power unit PGU-450, that uses in its work the combined cycle (most of heat stations still have only the steam cycle). Pictures presented here were made during the power unit construction, that allows to capture some equipment devices disassembled. Several of the following photos may be used by students and teachers of energetic professions as a methodological material.
The source of energy for this power unit is natural gas. While gas combusts, thermal energy releases, which is then used for the work of all unit equipment. The unit scheme has three power machines: two gas turbines and one steam turbine. Each of three machines is designed for the nominal output electric power of 150 MW. Gas turbines have the similar operating principle as jet aircrafts.
Two components are required for gas turbines: gas and air. The air from the street passes through air vents. Air intakes are closed with lattices to protect the gas turbine unit from birds or litter. They also have the anti-ice system that prevents from freezing in winter.
Then the air goes through air ducts to the compressor inlet of a gas turbine (of the axial type). After that, the compressed air falls into a combustion chamber with natural gas. Two combustion chambers are installed in every gas-turbine unit. They are located on each side.
Each combustion chamber is equipped with 8 gas burners.
The process of burning of the gas and air mixture and the release of thermal energy occur in combustion chambers. Here is a combustion chamber inside. Walls of such machines are covered with the fireproof lining.
At the bottom of the combustion chamber there is a small viewing window, that allows to control the process. This video shows the burning process of the gas-air mixture in the combustion chamber of the gas turbine unit at the time of its launch and at work for 30% of nominal power.
Then heated combustion products get to the gas turbine and rotate it.
The turbine produces more work than it is needed for the compressor, and an excess of this work is used to drive the "payload". An electrical generator with the power of 150 MW serves as such load. So here electricity is generated. A "gray barn" in the photo is exactly the generator. The generator is located on the same shaft with the compressor and turbine. Taken together, they rotate with the frequency of 3000 rev/min.
While going through the gas turbine, combustion products give it some of their heat, but not all the energy of combustion products is used to rotate the gas turbine. Much of this energy can not be used by the gas turbine, so combustion gases at the outlet of the gas turbine (exhaust gases) carry with them lot of heat (the gas temperature at the outlet of the gas turbine is about 500 °C). In aircraft engines this heat is wastefully released into the environment, but at this power unit it is used further in the steam-power cycle. For this purpose, exhaust gases from the output of the gas turbine are "blown" from below into so-called "recovery boilers" ( boiler-utilizers). One such boiler works in each gas turbine. Every boiler looks like a high-rise building.
In these boilers heat energy of exhaust gases is used for heating of water and turning it into steam. Subsequently, this steam is exploited for the work in the steam turbine.
For the heating and evaporation, water flows inside tubes with a diameter of about 30mm, that are placed horizontally, and exhaust gases from the gas turbine "wash" these tubes on the outside. So that is how a transfer of heat from gases to water (steam) takes place.