The principle of operation of a combined heat and power plant (CHP) is based on the unique property of water vapor - to be a heat carrier. In a heated state, under pressure, it turns into a powerful source of energy that drives the turbines of thermal power plants (TPP) - 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 birthplace of the first Russian thermal station, a year later, became St. Petersburg. Strange as it may seem, but even in our age of high technologies, thermal power plants have not found a full-fledged replacement: their share in the global energy sector is more than 60%.
And there is a simple explanation for this, which contains the advantages and disadvantages of thermal energy. Its "blood" - fossil fuel - coal, fuel oil, oil shale, peat and natural gas are still relatively available, and their reserves are quite large.
The big disadvantage is that the products of fuel combustion cause serious harm to the environment. And the natural pantry will one day be completely depleted, and thousands of thermal power plants will turn into rusting "monuments" of our civilization.
Principle of operation
To begin with, it is worth deciding on the terms "CHP" and "TPP". In simple terms, they are sisters. "Clean" thermal power plant - TPP is designed exclusively for the production of electricity. Its other name is "condensing power plant" - IES.
Combined Heat and Power Plant (CHP) is a type of TPP. In addition to generating electricity, it supplies hot water to the central heating system and for domestic needs.
The scheme of the CHP plant is quite simple. Fuel and heated air - an oxidizing agent - enter the furnace at the same time. The most common fuel in Russian CHP plants is crushed coal. The heat from the combustion of coal dust converts the water entering the boiler into steam, which is then fed under pressure to a steam turbine. A powerful stream of steam causes it to rotate, driving the generator rotor, which converts mechanical energy into electrical energy.
Further, the steam, which has already significantly lost its original parameters - temperature and pressure - enters the condenser, where after a cold "water shower" it again becomes water. Then the condensate pump transfers it to the regenerative heaters and then to the deaerator. There, the water is freed from gases - oxygen and CO 2, which can cause corrosion. After that, the water is reheated by steam and fed back to the boiler.
The second, no less important function of a CHP is to provide hot water (steam) intended for central heating systems in nearby settlements and for domestic use. In special heaters, cold water is heated up to 70 degrees in summer and 120 degrees in winter, after which it is pumped into the common mixing chamber by network pumps and then through the heating main system is supplied to consumers. Water supplies at the CHPP are constantly replenished.
How gas-fired TPPs work
Compared to coal-fired CHPPs, TPPs where gas turbine units are installed are much more compact and environmentally friendly. Suffice it to say that such a station does not need a steam boiler. A gas turbine plant is essentially the same turbojet aircraft engine, where, unlike it, the jet stream is not emitted into the atmosphere, but rotates the generator rotor. At the same time, the emissions of combustion products are minimal.
New technologies for coal combustion
The efficiency of modern CHP plants is limited to 34%. The vast majority of thermal power plants still run on coal, which can be explained quite simply - the reserves of coal on Earth are still enormous, so the share of thermal power plants in the total volume of generated electricity is about 25%.
The process of burning coal has remained practically unchanged for many decades. However, new technologies also came here.
The peculiarity of this method is that instead of air, pure oxygen released from the air is used as an oxidizing agent when burning coal dust. As a result, a harmful impurity - NOx - is removed from the flue gases. The rest of the harmful impurities are filtered out in the process of several stages of purification. The remaining CO 2 at the outlet is pumped into containers under high pressure and is subject to burial at a depth of 1 km.
Method "oxyfuel capture"
Here, too, when burning coal, pure oxygen is used as an oxidizing agent. Only unlike the previous method, steam is generated at the moment of combustion, which drives the turbine into rotation. Then ash and sulfur oxides are removed from the flue gases, cooling and condensation are performed. The remaining carbon dioxide under a pressure of 70 atmospheres is converted into a liquid state and placed underground.
Coal is burned in the "usual" mode - in a boiler mixed with air. After that, ash and SO 2 - sulfur oxide are removed. Then CO 2 is removed using a special liquid absorbent, after which it is disposed of by burial.
The five most powerful thermal power plants in the world
The championship belongs to the Chinese TPP Tuoketuo with a capacity of 6600 MW (5 en / bl. X 1200 MW), occupying an area of 2.5 square meters. km. It is followed by its "compatriot" - Taichzhun TPP with a capacity of 5824 MW. The three leaders are closed by the largest in Russia Surgutskaya GRES-2 - 5597.1 MW. The fourth place is taken by the Polish Belchatuvskaya TPP - 5354 MW, and the fifth - Futtsu CCGT Power Plant (Japan) - a gas-fired TPP with a capacity of 5040 MW.