The principle of operation of a combined heat and power plant (CHP) is based on the unique property of water vapor – to be a coolant. When heated, under pressure, it turns into a powerful source of energy, driving the turbines of thermal power plants (TPPs) – a legacy of such a distant era of steam.
The first thermal power plant was built in New York City on Pearl Street (Manhattan) in 1882. The motherland of the first Russian thermal station, a year later, was St. Petersburg. Strange as it may seem, even in our era of high-tech power plants there has never been a full replacement: their share in the world energy industry is more than 60%.
And this is a simple explanation, in which the advantages and disadvantages of thermal energy are concluded. Its “blood” – organic fuel – coal, fuel oil, oil shale, peat and natural gas are still relatively affordable, and their reserves are large enough.
A big downside is that fuel combustion products cause serious damage to the environment. Yes, and the natural pantry once exhausted, and thousands of TPPs will turn into rusting “monuments” of our civilization.
Principle of work
For a start, it is necessary to determine the terms “CHP” and “TPP”. Speaking in clear language – they are sisters. “Clean” thermal power plant – TPP is designed exclusively for electricity generation. Its other name is “condensation power plant” – IES.
Cogeneration plant – CHP – a kind of TPP. It, in addition to generating electricity, provides hot water to the central heating system and for domestic needs.
The scheme of the CHP plant is quite simple. In the furnace at the same time, fuel and heated air – the oxidizer. The most common fuel at Russian CHP plants is ground coal. Heat from the combustion of coal dust turns the water entering the boiler into steam, which is then supplied under pressure to the steam turbine. A powerful stream of steam causes it to rotate, driving the rotor of the generator, which converts mechanical energy into electrical energy.
Then the steam, which has already lost its initial values - temperature and pressure – gets into the condenser, where after a cold “water shower” it again becomes water. Then the condensate pump pumps it to the regenerative heaters and then to the deaerator. There, water is released from gases – oxygen and CO2, which can cause corrosion. After that, the water is again heated from the steam and fed back to the boiler.
The second, no less important function of the CHP is the provision of hot water (steam) for central heating systems of nearby settlements and household use. In special heaters, cold water heats up to 70 degrees in summer and 120 degrees in winter, after which the network pumps are fed into the common mixing chamber and then through the system of heat mains to the consumers. Reserves of water at the CHPP are constantly replenished.
How do TPPs work on gas
Compared with coal-fired power plants, TPPs where gas-turbine plants are installed are much more compact and environmentally friendly. Suffice it to say that such a station does not need a steam boiler. The gas turbine plant is essentially the same turbojet engine, where, unlike it, the jet is not discharged into the atmosphere, but rotates the rotor of the generator. At the same time emissions of combustion products are minimal.
New technologies for coal combustion
The efficiency of modern CHP is limited to 34%. The absolute majority of thermal power plants are still operating on coal, which is very simple – coal reserves on the Earth are still huge, therefore the share of TPPs in the total amount of generated electricity is about 25%.
The process of coal combustion for many decades remains virtually unchanged. However, new technologies also came here.
The peculiarity of this method is that, instead of air, pure oxygen is used as an oxidizer when burning coal dust. As a result, a harmful impurity – NOx – is removed from the flue gases. The remaining harmful impurities are filtered out during several purification steps. The remaining CO2 is pumped into the tanks under high pressure and is subject to disposal at a depth of 1 km.
“oxyfuel capture” method
Here, also, when burning coal, pure oxygen is used as the oxidizing agent. Only in contrast to the previous method at the time of combustion, steam is generated, leading the turbine into rotation. Then ash and sulfur oxides are removed from the flue gases, cooling and condensation are carried out. The remaining carbon dioxide at a pressure of 70 atmospheres is converted to a liquid state and placed under the ground.
Coal is burned in the “normal” mode – in a boiler mixed with air. After that, the ash and SO2-sulfur oxide are removed. Further, CO2 is removed with a special liquid absorbent, after which it is disposed of by disposal.
Five of the world's most powerful thermal power plants
The championship belongs to the Chinese TPP Tuoketuo with a capacity of 6,600 MW (5 en / bl. X 1200 MW), covering an area of 2.5 square meters. km. It is followed by its “compatriot” – Taichung Thermal Power Plant with a capacity of 5824 MW. The three leaders are the largest in Surgutskaya GRES-2 – 5597.1 MW. In fourth place, the Polish Belchatuvskaya TPP – 5354 MW, and the fifth – Futtsu CCGT Power Plant (Japan) – a gas thermal power plant with a capacity of 5040 MW.