The future of coal-fired power plants. Thermal power plants Tes works on

Abstract on the discipline "Introduction to direction"

Made by student Mikhailov D.A.

Novosibirsk State Technical University

Novosibirsk, 2008

Introduction

Power plant is a power plant used to convert natural energy into electrical energy. The type of power plant is primarily determined by the type of natural energy. The most widespread are thermal power plants (TPPs), which use thermal energy released during the combustion of fossil fuels (coal, oil, gas, etc.). Thermal power plants generate about 76% of the electricity produced on our planet. This is due to the presence of fossil fuels in almost all regions of our planet; the possibility of transporting fossil fuel from the production site to a power plant located near energy consumers; technical progress at thermal power plants, ensuring the construction of thermal power plants with a large capacity; the possibility of using the waste heat of the working fluid and supply to consumers, in addition to electrical energy, also thermal energy (with steam or hot water), etc. Thermal power plants designed only for the production of electricity are called condensing power plants (IES). Power plants intended for combined generation of electric energy and supply of steam, as well as hot water to a heat consumer, have steam turbines with intermediate steam extraction or with back pressure. In such installations, the heat of the exhaust steam is partially or even completely used for heat supply, as a result of which the heat loss with the cooling water is reduced. However, the fraction of steam energy converted into electricity, with the same initial parameters, at plants with cogeneration turbines is lower than at plants with condensing turbines. Thermal power plants, in which the spent steam, along with the generation of electricity, is used for heat supply are called combined heat and power plants (CHP).

Basic principles of TPP operation

Figure 1 shows a typical thermal diagram of a fossil-fueled condensing unit.

Fig. 1 Schematic thermal diagram of TPP

1 - steam boiler; 2 - turbine; 3 - electric generator; 4 - capacitor; 5 - condensate pump; 6 - low pressure heaters; 7 - deaerator; 8 - feed pump; 9 - high pressure heaters; 10 - drain pump.

This circuit is called a steam reheat circuit. As is known from the course of thermodynamics, the thermal efficiency of such a circuit with the same initial and final parameters and the correct choice of reheat parameters is higher than in a circuit without reheat.

Let's consider the principles of TPP operation. Fuel and oxidizer, which is usually heated air, continuously enter the boiler furnace (1). Coal, peat, gas, oil shale or fuel oil are used as fuel. Most TPPs in our country use coal dust as fuel. Due to the heat generated as a result of fuel combustion, the water in the steam boiler heats up, evaporates, and the resulting saturated steam enters the steam turbine through the steam line (2). The purpose of which is to convert the thermal energy of steam into mechanical energy.

All moving parts of the turbine are rigidly connected to the shaft and rotate with it. In a turbine, the kinetic energy of the steam jets is transferred to the rotor as follows. High pressure and high temperature steam, which has a large internal energy, from the boiler enters the nozzles (channels) of the turbine. A jet of steam at a high speed, often higher than the sonic one, continuously flows out of the nozzles and enters the turbine rotor blades, mounted on a disk rigidly connected to the shaft. In this case, the mechanical energy of the steam flow is converted into the mechanical energy of the turbine rotor, or, more precisely, into the mechanical energy of the turbine generator rotor, since the shafts of the turbine and the electric generator (3) are interconnected. In an electric generator, mechanical energy is converted into electrical energy.

After the steam turbine, water steam, having already low pressure and temperature, enters the condenser (4). Here, steam is converted into water by means of cooling water pumped through tubes located inside the condenser, which is supplied to the deaerator (7) by a condensate pump (5) through regenerative heaters (6).

The deaerator serves to remove gases dissolved in it from water; at the same time in it, as in regenerative heaters, the feed water is heated by steam taken from the turbine extraction. Deaeration is carried out in order to bring the oxygen and carbon dioxide content in it to permissible values ​​and thereby reduce the corrosion rate in the water and steam tracts.

Deaerated water is supplied to the boiler plant by the feed pump (8) through the heaters (9). The condensate of the heating steam formed in the heaters (9) is bypassed in a cascade into the deaerator, and the condensate of the heating steam of the heaters (6) is supplied by the drain pump (10) to the line through which the condensate flows from the condenser (4).

The most difficult from the technical point of view is the organization of the operation of coal-fired TPPs. At the same time, the share of such power plants in the domestic energy sector is high (~ 30%) and it is planned to increase it.

The process flow diagram of such a coal-fired power plant is shown in Fig. 2.

Fig. 2 Technological diagram of a pulverized coal TPP

1 - railway cars; 2 - unloading devices; 3 - warehouse; 4 - belt conveyors; 5 - crushing plant; 6 - raw coal bunker; 7 - pulverized coal mills; 8 - separator; 9 - cyclone; 10 - bunker of coal dust; 11 - feeders; 12 - mill fan; 13 - boiler combustion chamber; 14 - blower fan; 15 - ash collectors; 16 - smoke exhausters; 17 - chimney; 18 - low pressure heaters; 19 - high pressure heaters; 20 - deaerator; 21 - feed pumps; 22 - turbine; 23 - turbine condenser; 24 - condensate pump; 25 - circulation pumps; 26 - receiving well; 27 - discharge well; 28 - chemical shop; 29 - network heaters; 30 - pipeline; 31 - condensate drain line; 32 - electrical switchgear; 33 - dredge pumps.

Fuel in railway cars (1) goes to the unloading devices (2), from where it is sent to the warehouse (3) with the help of belt conveyors (4), from the warehouse fuel is supplied to the crushing plant (5). It is possible to supply fuel to the crushing plant and directly from the unloading devices. From the crushing plant, the fuel enters the raw coal bunkers (6), and from there, through the feeders, into the pulverized coal mills (7). Coal dust is pneumatically transported through a separator (8) and a cyclone (9) to the coal dust bin (10), and from there by feeders (11) to the burners. Air from the cyclone is sucked in by the mill fan (12) and supplied to the boiler combustion chamber (13).

The gases formed during combustion in the combustion chamber, after leaving it, pass sequentially through the gas ducts of the boiler plant, where in the superheater (primary and secondary, if a cycle with intermediate superheating of steam is carried out) and the water economizer give off heat to the working fluid, and in the air heater - supplied to the steam boiler to air. Then, in the ash collectors (15), the gases are cleaned from fly ash and through the chimney (17) by smoke exhausters (16) are released into the atmosphere.

Slag and ash falling out under the combustion chamber, air heater and ash collectors are washed off with water and are fed through channels to dredging pumps (33), which pump them to ash dumps.

The air required for combustion is supplied to the air heaters of the steam boiler by a blower fan (14). Air is usually taken from the upper part of the boiler room and (with steam boilers of high capacity) from the outside of the boiler room.

Superheated steam from the steam boiler (13) is fed to the turbine (22).

Condensate from the turbine condenser (23) is supplied by condensate pumps (24) through low pressure regenerative heaters (18) to the deaerator (20), and from there by feed pumps (21) through high pressure heaters (19) to the boiler economizer.

Steam and condensate losses are replenished in this scheme with chemically demineralized water, which is fed into the condensate line downstream of the turbine condenser.

Cooling water is supplied to the condenser from the water supply well (26) by circulating pumps (25). The heated water is discharged into the waste well (27) of the same source at a certain distance from the intake point, sufficient so that the heated water is not mixed with the withdrawn water. Devices for chemical treatment of make-up water are located in the chemical shop (28).

The schemes may include a small network heating installation for heating the power plant and the adjacent village. Steam is supplied to the network heaters (29) of this unit from the turbine extractions, the condensate is discharged through the line (31). Mains water is supplied to and removed from the heater through pipelines (30).

The generated electrical energy is diverted from the electric generator to external consumers through step-up electrical transformers.

To supply electric power to electric motors, lighting devices and devices of the power plant, there is an electrical switchgear for its own needs (32).

Conclusion

The abstract presents the basic principles of TPP operation. The thermal diagram of a power plant is considered on the example of the operation of a condensing power plant, as well as a technological diagram on the example of a coal-fired power plant. The technological principles of electric energy and heat production are shown.

Climate Analytics continues to insist that coal energy in Europe must be eliminated by 2030 - otherwise the EU will not meet the goals of the Paris climate agreement. But which stations should you close first? Two approaches are proposed - ecological and economic. "Oxygen.LIFE" took a closer look at the largest coal-fired thermal power plants in Russia, which no one is going to close.

Close in ten years

Climate Analytics continues to insist that in order to achieve the goals of the Paris Agreement on climate, EU countries will have to close almost all operating coal-fired power plants. The energy sector in Europe is in need of total decarbonization, since a significant part of the total greenhouse gas (GHG) emissions in the EU is generated in coal energy. Therefore, phasing out coal in this industry is one of the most cost-effective methods of reducing GHG emissions, and such actions will also provide significant benefits in terms of air quality, public health and energy security.

Now in the EU there are more than 300 power plants with 738 coal-fired power units operating at them. Naturally, they are not evenly distributed geographically. But in general, coal and lignite (brown coal) provide a quarter of all electricity generation in the EU. The EU's most dependent on coal are Poland, Germany, Bulgaria, the Czech Republic and Romania. Germany and Poland account for 51% of installed coal capacity in the EU and 54% of GHG emissions from coal energy in the whole of united Europe. At the same time, there are no coal-fired thermal power plants in seven EU countries.

“The continued use of coal for power generation is incompatible with the implementation of the goal of drastically reducing GHG emissions. Therefore, the EU needs to develop a strategy to phase out coal faster than it currently is, ”summarizes Climate Analytics. Otherwise, total EU emissions by 2050 will grow by 85%. Climate Analytics' simulations indicated that 25% of currently operating coal-fired power plants should be closed by 2020. In another five years, it is necessary to close 72% of thermal power plants, and completely get rid of coal energy by 2030.

The main question is how to do it? According to Climate Analytics, “the critical question is what criteria should be used to determine when to close certain TPPs? From the point of view of the earth's atmosphere, the criteria are irrelevant, as GHG emissions will decline at the right rate. But from the point of view of politicians, business owners and other stakeholders, developing such criteria is a crucial moment in decision making. ”

Climate Analytics offers two possible strategies for eliminating the use of coal for power generation. The first is to first shut down those TPPs that are leading in terms of GHG emissions. The second strategy is to close the plants of the least business value. An interesting infographic has been drawn for each of the strategies, showing how the face of the EU will change over the years following the closure of coal plants. In the first case, Poland, Czech Republic, Bulgaria and Denmark will be under attack. In the second - also Poland and Denmark.

There is no unity

Climate Analytics also plotted closure years for all 300 stations in accordance with two strategies. It is easy to see that these years differ significantly from the periods of operation of these stations in the usual mode (the so-called BAU - businnes as usual). For example, the largest in Europe station Belchatow in Poland (with a capacity of more than 4.9 GW) can operate at least until 2055; while it is proposed to close it already by 2027 - the same term under any scenario.

In general, it is precisely five Polish thermal power plants that can calmly smoke until the 2060s that Climate Analytics proposes to close three to four decades ahead of schedule. Poland, whose energy sector is 80% dependent on coal, is unlikely to be satisfied with such a development of events (recall, this country is even going to challenge the climate obligations imposed on it by the EU in court). Five more stations from the Top 20 are in the UK; eight in Germany. Also in the top twenty for closure - two thermal power plants in Italy.

At the same time, the British Fiddler's Ferry (with a capacity of 2 GW) should be closed already in 2017, and the rest of the British thermal power plants, as stated by the government of this country, by 2025. That is, only in this country the process can be relatively painless. everything can stretch until 2030, the implementation of the two strategies will differ depending on the specifics of the land (there are coal-mining regions) .In the Czech Republic and Bulgaria, coal generation will need to be phased out by 2020, primarily due to substantial emissions.

Renewable energy sources should come to replace coal. Reducing the cost of solar and wind generation is an important trend that needs to be supported and developed, according to Climate Analytics. Renewable energy sources can transform the energy sector, including by creating new jobs (not only in the industry itself, but also in the production of equipment). Which, among other things, will be able to employ the personnel released from the coal energy sector.

However, Climate Analytics admits that there is no unity in Europe regarding coal. While some countries have significantly reduced production and announced a complete rejection of this type of fuel in the next 10-15 years (among them, for example, the UK, Finland and France), others are either building or planning to build new coal-fired power plants (Poland and Greece). “Great attention is paid to environmental issues in Europe, but it will hardly be possible to quickly abandon coal generation. First, it is necessary to put into operation replacement capacities, because heat and light are needed by both the population and the economy. This is all the more important because earlier decisions were made to close a number of nuclear power plants in Europe. Social problems will arise, it will be necessary to retrain some of the employees of the stations themselves, a significant number of jobs in various industries will be cut, which will undoubtedly increase tension in society. The closure of coal-fired power plants will also affect the budgets, since there will not be a significant group of taxpayers, and the operating indicators of those companies that previously supplied them with goods and services will significantly decrease. If any solution is possible, then it may consist in a prolonged rejection of coal generation, while continuing to work on improving technologies in order to reduce emissions from coal combustion, improve the environmental situation at coal-fired power plants, "- says on this occasion Dmitry Baranov, Leading Expert of Finam Management Management Company.

Top-20 coal-fired power plants in Europe, which, according to Climate Analytics, will need to be closed

What do we have?

The share of thermal generation in the structure of electricity generation in Russia is more than 64%, in the structure of the installed capacity of UES power plants - more than 67%. However, in the TOP-10 largest thermal power plants in the country, only two stations operate on coal - Reftinskaya and Ryazanskaya; in the main, thermal energy in Russia is gas. “Russia has one of the best fuel balance structures in the world. We use only 15% of coal for energy production. On average around the world, this figure is 30-35%. In China - 72%, in the USA and Germany - 40%. The task of reducing the share of non-carbon sources to 30% is being actively pursued in Europe as well. In Russia, this program, in fact, has already been implemented, "- said the head of the Ministry of Energy of the Russian Federation Alexander Novak speaking at the end of February at the panel session "Green Economy as a Vector of Development" at the Russian Investment Forum 2017 in Sochi.

The share of nuclear energy in the total volume of the country's energy balance is 16-17%, hydroelectric generation - 18%, gas accounts for about 40%. According to the Institute of Energy Research of the Russian Academy of Sciences, coal in electricity generation has long been actively replaced by gas and atomic energy, and most rapidly in the European part of Russia. The largest coal-fired power plants are located, however, in the center and in the Urals. But if you look at the picture in the energy sector in the context of regions, and not individual stations, the picture will be different: the most "coal" regions are in Siberia and the Far East. The structure of territorial energy balances depends on the level of gasification: it is high in the European part of Russia, and low in Eastern Siberia and beyond. Coal as a fuel is usually used in urban CHP plants, where not only electricity is generated, but also heat. Therefore, generation in large cities (like Krasnoyarsk) is entirely based on coal. In general, the share of thermal power plants in the IES of Siberia alone currently accounts for 60% of electricity generation - this is about 25 GW of "coal" capacities.

As for renewable energy sources, now the share of such sources in the energy balance of the Russian Federation accounts for a symbolic 0.2%. “We plan to reach 3% - up to 6 thousand MW due to various support mechanisms,” Novak made a forecast. Rosseti gives more optimistic forecasts: the installed capacity of renewable energy sources in Russia by 2030 may grow by 10 GW. Nevertheless, a global restructuring of the energy balance in our country is not expected. “According to forecasts, by 2050 there will be about 10 billion people in the world. Already today, about 2 billion do not have access to energy sources. Imagine what humanity's need for energy will be in 33 years, and how renewable energy sources should develop in order to meet all demand, "- this is how Alexander Novak proves the viability of traditional energy.

“There is definitely no talk of“ giving up coal ”in Russia, especially since, according to the Energy Strategy until 2035, it is planned to increase the share of coal in the country's energy balance,” reminds Dmitry Baranov from UK Finam Management. - Along with oil and gas, coal is one of the most important minerals on the planet, and Russia, as one of the largest countries in the world in terms of its reserves and production, is simply obliged to pay due attention to the development of this industry. Back in 2014, at a meeting of the Russian government, Novak presented a program for the development of the coal industry in Russia until 2030. It focuses on the creation of new coal mining centers, primarily in Siberia and the Far East, improvement of scientific and technical potential in the industry, as well as the implementation of projects in coal chemistry. "

The largest coal-fired TPPs in Russia

Reftinskaya GRES (Enel Russia)

It is the largest coal-fired thermal power plant in Russia (and the second in the top 10 thermal power plants in the country). Located in the Sverdlovsk region, 100 km northeast of Yekaterinburg and 18 km from Asbest.
Installed electric capacity - 3800 MW.
Installed heat capacity - 350 Gcal / h.
Provides power supply to the industrial regions of the Sverdlovsk, Tyumen, Perm and Chelyabinsk regions.
The construction of the power plant began in 1963, the first power unit was launched in 1970, and the last in 1980.

Ryazanskaya GRES (OGK-2)

Fifth in the top 10 largest thermal power plants in Russia. Works on coal (first stage) and natural gas (second stage). Located in Novomichurinsk (Ryazan region), 80 km south of Ryazan.
Installed electric capacity (together with GRES-24) - 3,130 MW.
Installed thermal power - 180 Gcal / hour.
Construction began in 1968. The first power unit was commissioned in 1973, the last on December 31, 1981.

Novocherkasskaya GRES (OGK-2)

Located in the Donskoy microdistrict in Novocherkassk (Rostov region), 53 km southeast of Rostov-on-Don. Powered by gas and coal. The only thermal power plant in Russia that uses local waste from coal mining and coal preparation - anthracite mine.
Installed electric capacity - 2,229 MW.
Installed thermal power - 75 Gcal / hour.
Construction began in 1956. The first power unit was commissioned in 1965, the last - the eighth - in 1972.

Kashirskaya GRES ("InterRAO")

Located in Kashira (Moscow region).
Powered by coal and natural gas.
Installed electric capacity - 1,910 MW.
Installed heat capacity - 458 Gcal / h.
Commissioned in 1922 according to the GOELRO plan. In the 1960s, a large-scale modernization was carried out at the station.
The pulverized coal-fired power units No. 1 and No. 2 are planned to be decommissioned in 2019. By 2020, the same fate awaits four more power units operating on gas-oil fuel. Only the most modern block No. 3 with a capacity of 300 MW will remain in operation.

Primorskaya GRES (RAO ES of the East)

Located in Luchegorsk (Primorsky Territory).
The most powerful thermal power plant in the Far East. Works on coal from the Luchegorsk coal mine. Provides most of the energy consumption of Primorye.
Installed electric capacity - 1467 MW.
Installed heat capacity - 237 Gcal / hour.
The first power unit of the station was commissioned in 1974, the last in 1990. The GRES is located practically “on board” a coal mine - nowhere else in Russia has a power plant been built in such close proximity to a fuel source.

Troitskaya GRES (OGK-2)

Located in Troitsk (Chelyabinsk region). Favorably located in the industrial triangle Yekaterinburg - Chelyabinsk - Magnitogorsk.
Installed electric capacity - 1,400 MW.
Installed thermal power - 515 Gcal / hour.
The first stage of the station was launched in 1960. The equipment of the second stage (for 1200 MW) was decommissioned in 1992-2016.
In 2016, a unique pulverized coal power unit No. 10 with a capacity of 660 MW was commissioned.

Gusinoozerskaya GRES ("InterRAO")

Located in Gusinoozersk (Republic of Buryatia), it provides electricity to consumers in Buryatia and neighboring regions. The main fuel for the station is brown coal from the Okino-Klyuchevsky open-cast mine and the Gusinoozyorsky deposit.
Installed electric capacity - 1160 MW.
Installed heat capacity - 224.5 Gcal / h.
Four power units of the first stage were commissioned from 1976 to 1979. The commissioning of the second stage began in 1988 with the launch of power unit No. 5.

In 1879, when Thomas Alva Edison invented the incandescent lamp, the era of electrification began. The production of large quantities of electricity required cheap and readily available fuel. Coal met these requirements, and the first power plants (built at the end of the 19th century by Edison himself) operated on coal.

As more and more stations were built in the country, the dependence on coal increased. Since World War I, roughly half of the US's annual electricity production has come from coal-fired power plants. In 1986, the total installed capacity of such power plants was 289,000 MW, and they consumed 75% of the total amount (900 million tons) of coal mined in the country. Given the existing uncertainties regarding the prospects for the development of nuclear energy and the growth of oil and natural gas production, it can be assumed that by the end of the century, coal-fired thermal power plants will produce up to 70% of all electricity generated in the country.

However, despite the fact that coal has long been and will be the main source of electricity for many years (in the United States, it accounts for about 80% of the reserves of all types of natural fuels), it has never been the optimal fuel for power plants. The specific energy content per unit weight (i.e., the calorific value) of coal is lower than that of oil or natural gas. It is more difficult to transport and, in addition, burning coal causes a number of undesirable environmental consequences, in particular, acid rain. Since the end of the 60s, the attractiveness of coal-fired power plants has sharply declined due to the tightening of requirements for environmental pollution with gaseous and solid emissions in the form of ash and slag. The costs of solving these environmental problems, along with the increasing cost of building complex facilities such as thermal power plants, have made their development prospects less favorable from a purely economic point of view.

However, if the technological base of coal-fired thermal power plants is changed, their former attractiveness may be revived. Some of these changes are evolutionary in nature and are aimed primarily at increasing the capacity of existing installations. At the same time, completely new processes of waste-free combustion of coal are being developed, i.e. with minimal damage to the environment. The introduction of new technological processes is aimed at ensuring that future coal-fired thermal power plants can be effectively controlled for the degree of environmental pollution, have flexibility in terms of the possibility of using various types of coal and do not require long construction times.

In order to appreciate the significance of advances in coal combustion technology, consider briefly the operation of a conventional coal-fired thermal power plant. Coal is burned in the furnace of a steam boiler, which is a huge chamber with pipes inside, in which water turns into steam. Before being fed into the furnace, the coal is crushed into dust, due to which almost the same completeness of combustion is achieved as when burning flammable gases. A large steam boiler consumes an average of 500 tons of pulverized coal per hour and generates 2.9 million kg of steam, which is enough to generate 1 million kWh of electricity. During the same time, the boiler emits about 100,000 m3 of gases into the atmosphere.
The generated steam passes through a superheater, where its temperature and pressure are increased, and then enters a high-pressure turbine. The mechanical energy of the turbine rotation is converted by an electric generator into electrical energy. In order to obtain higher energy conversion efficiency, steam from the turbine is usually returned to the boiler for reheating and then drives one or two low pressure turbines before being condensed by cooling; condensate is returned to the boiler cycle.

Thermal power plant equipment includes fuel feeding mechanisms, boilers, turbines, generators, as well as complex cooling systems, flue gas cleaning and ash removal. All of these primary and secondary systems are designed to operate reliably for 40 years or more at loads that can range from 20% of the plant's installed capacity to maximum. The capital cost of equipment for a typical 1,000 MW thermal power plant is typically in excess of $ 1 billion.

The efficiency with which the heat released by burning coal can be converted into electricity was only 5% before 1900, but by 1967 it had reached 40%. In other words, over a period of about 70 years, the specific consumption of coal per unit of generated electricity has decreased eightfold. Accordingly, the cost of 1 kW of installed capacity of thermal power plants also decreased: if in 1920 it was $ 350 (in 1967 prices), then in 1967 it dropped to $ 130. The price of electricity supplied also fell over the same period from 25 cents to 2 cents per kWh.

However, starting in the 1960s, the pace of progress began to decline. This trend, apparently, is explained by the fact that traditional thermal power plants have reached the limit of their perfection, determined by the laws of thermodynamics and the properties of materials from which boilers and turbines are made. Since the early 1970s, these technical factors have been exacerbated by new economic and organizational reasons. In particular, capital expenditures have sharply increased, the rate of growth in demand for electricity has slowed down, requirements for environmental protection from harmful emissions have become more stringent, and the timeframes for the implementation of power plant construction projects have been lengthened. As a result, the cost of generating electricity from coal, which had a long-term downward trend, has risen sharply. Indeed, 1 kW of electricity generated by new thermal power plants now costs more than in 1920 (in comparable prices).

Over the past 20 years, the cost of coal-fired power plants has been most influenced by stricter requirements for the removal of gaseous,
liquid and solid waste. Gas cleaning and ash handling systems in modern thermal power plants now account for 40% of capital costs and 35% of operating costs. From a technical and economic point of view, the most significant element of an emission control system is a flue gas de-sulphurization plant, often referred to as a wet (scrubber) dust collection system. A wet dust collector (scrubber) traps sulfur oxides, which are the main pollutants formed during coal combustion.

The idea of ​​wet dust collection is simple, but in practice it turns out to be difficult and expensive. An alkaline substance, usually lime or limestone, is mixed with water and the solution is sprayed into the flue gas stream. Sulfur oxides contained in flue gases are absorbed by alkali particles and precipitate out of solution in the form of inert sulphite or calcium sulphate (gypsum). Gypsum can be easily removed or, if clean enough, marketed as a building material. In more complex and expensive scrubber systems, gypsum sludge can be converted to sulfuric acid or elemental sulfur, which are more valuable chemical products. Since 1978, the installation of scrubbers has been mandatory at all pulverized coal-fired thermal power plants under construction. As a result, the US energy industry now has more scrubber units than the rest of the world.
The cost of a scrubber system at new plants is usually $ 150-200 per 1 kW of installed capacity. The installation of scrubbers at existing plants, originally designed without wet gas cleaning, is 10-40% more expensive than at new plants. The running costs of scrubbers are quite high whether they are installed in old or new plants. Scrubbers generate a huge amount of gypsum sludge, which must be kept in sedimentation ponds or dumped, which creates a new environmental problem. For example, a 1000 MW thermal power plant operating on coal containing 3% sulfur produces so much sludge per year that they can cover an area of ​​1 km2 with a layer about 1 m thick.
In addition, wet gas cleaning systems consume a lot of water (at a 1000 MW plant, water consumption is about 3800 l / min), and their equipment and pipelines are often prone to clogging and corrosion. These factors increase operating costs and reduce overall system reliability. Finally, in scrubber systems, from 3 to 8% of the energy generated by the station is consumed for driving pumps and smoke exhausters and for heating flue gases after gas cleaning, which is necessary to prevent condensation and corrosion in chimneys.
The widespread adoption of scrubbers in the American power industry has not been simple or cheap. The first scrubber installations were significantly less reliable than the rest of the station equipment, therefore the components of the scrubber systems were designed with a large margin of safety and reliability. Some of the difficulties associated with the installation and operation of scrubbers can be attributed to the fact that industrial application of scrubber technology was prematurely started. Only now, after 25 years of experience, has the reliability of scrubber systems reached an acceptable level.
The cost of coal-fired power plants has risen, not only because of the mandatory presence of emission control systems, but also because the cost of construction itself has skyrocketed. Even taking inflation into account, the unit cost of installed capacity of coal-fired thermal power plants is now three times higher than in 1970. Over the past 15 years, the "economies of scale", that is, the benefits from the construction of large power plants, have been offset by a significant increase in the cost of construction ... This rise in price partly reflects the high cost of financing long-term capital construction projects.

The impact of the delay in project implementation can be seen in the example of Japanese energy companies. Japanese firms are usually more agile than their American counterparts in dealing with the organizational, technical and financial problems that often delay the commissioning of large construction projects. In Japan, a power plant can be built and commissioned in 30-40 months, while in the United States, a plant of the same capacity usually takes 50-60 months. With such long project implementation times, the cost of a new plant under construction (and, therefore, the cost of frozen capital) is comparable to the fixed capital of many US energy companies.

Therefore, energy companies are looking for ways to reduce the cost of building new power generation plants, in particular by using modular units of lower capacity, which can be quickly transported and installed in an existing plant to meet growing demand. These plants can be brought online in a shorter time frame and therefore pay for themselves faster, even if the ROI remains constant. Installing new modules only when an increase in system capacity is required can result in net savings of up to $ 200 per kW, although economies of scale are lost with smaller units.
As an alternative to building new power generating facilities, utilities have also practiced retrofitting existing old power plants to improve their performance and extend their service life. This strategy naturally requires less capital expenditures than building new stations. This trend is justified also because the power plants built about 30 years ago are not yet morally obsolete. In some cases, they work even with higher efficiency, since they are not equipped with scrubbers. Old power plants are gaining an increasing share in the country's energy sector. In 1970, only 20 electricity generating facilities in the United States were over 30 years old. By the end of the century, 30 years will be the average age of coal-fired thermal power plants.

Utilities are also looking for ways to reduce plant operating costs. To prevent energy losses, it is necessary to provide timely warning of the deterioration in the performance of the most important areas of the facility. Therefore, continuous monitoring of the state of components and systems is becoming an important part of the operational service. Such continuous monitoring of natural processes of wear, corrosion and erosion allows plant operators to take timely measures and prevent emergency failure of power plants. The significance of such measures can be correctly assessed if we consider, for example, that the forced shutdown of a 1000 MW coal-fired plant could bring the energy company losses of $ 1 million per day, mainly because the unreported energy must be compensated for by supplying electricity from more expensive sources.

The rise in the unit costs of transporting and processing coal and of ash removal has also made the quality of coal (determined by moisture, sulfur and other minerals) an important factor in determining the performance and economics of thermal power plants. Although low-grade coal can cost less than high-grade coal, its consumption for the production of the same amount of electricity is much higher. The cost of transporting more low-grade coal may offset the benefit of its lower price. In addition, low-grade coal usually generates more waste than high-grade coal, and therefore requires high ash removal costs. Finally, the composition of low-grade coals is subject to large fluctuations, which makes it difficult to "tune" the station's fuel system to work with the maximum possible efficiency; in this case, the system must be adjusted so that it can operate at the worst grade expected.
In existing power plants, the quality of the coal can be improved or at least stabilized by removing some impurities, such as sulfur-containing minerals, before combustion. In treatment plants, crushed "dirty" coal is separated from impurities in many ways, taking advantage of differences in specific gravity or other physical characteristics of the coal and impurities.

Despite these efforts to improve the performance of existing coal-fired power plants, an additional 150,000 MW of power capacity will need to be operational in the United States by the end of the century if electricity demand grows at the expected rate of 2.3% per year. To keep coal competitive in the ever-expanding energy market, utilities will have to adopt innovative new methods of burning coal that are more efficient than traditional ones in three key respects: less pollution, less time to build power plants, and better performance and performance. ...

BURNING COAL IN A LIQUID LAYER reduces the need for ancillary emission treatment plants from the power plant. A fluidized bed of a mixture of coal and limestone is created in the boiler furnace by an air flow, in which solid particles are mixed and are in suspension, that is, they behave in the same way as in a boiling liquid. Turbulent mixing ensures complete combustion of coal; in this case, limestone particles react with sulfur oxides and trap about 90% of these oxides. Since the heating coarse of the boiler is directly in contact with the fluidized bed of fuel, steam generation is more efficient than in conventional coal-fired steam boilers. In addition, the temperature of the burning coal in the fluidized bed is lower, which prevents the boiler slag from melting and reduces the formation of nitrogen oxides.

COAL GASIFICATION can be carried out by heating a mixture of coal and water in an oxygen atmosphere. The product of the process is a gas consisting mainly of carbon monoxide and hydrogen. Once the gas has been cooled, de-soldered and freed from sulfur, it can be used as fuel for gas turbines and then to produce steam for a steam turbine (combined cycle). The combined cycle plant emits less pollutants into the atmosphere than a conventional coal-fired thermal plant.

Currently, more than a dozen methods of coal combustion with increased efficiency and less damage to the environment are being developed. The most promising among them are fluidized bed combustion and coal gasification. Combustion according to the first method is carried out in the furnace of a steam boiler, which is arranged in such a way that crushed coal mixed with limestone particles is maintained above the grate of the furnace in a suspended ("pseudo-liquefied") state by a powerful ascending air flow. Suspended particles behave essentially the same way as in a boiling liquid, that is, they are in turbulent motion, which ensures a high efficiency of the combustion process. The water pipes of such a boiler are in direct contact with the "fluidized bed" of burning fuel, as a result of which a large proportion of heat is transferred by thermal conductivity, which is much more efficient than radiative and convective heat transfer in a conventional steam boiler.

A boiler with a firebox, where coal is fired in a fluidized bed, has a larger area of ​​heat transfer pipe surfaces than a conventional boiler that runs on pulverized coal, which allows to reduce the temperature in the furnace and thereby reduce the formation of nitrogen oxides. (If the temperature in a conventional boiler can be higher than 1650 ° C, then in a boiler with combustion in a fluidized bed it is in the range of 780-870 ° C.) Moreover, limestone mixed with coal binds 90 or more percent of the sulfur released from coal during combustion, since the lower operating temperature promotes the reaction between sulfur and limestone to form sulfite or calcium sulfate. Thus, substances harmful to the environment, formed during the combustion of coal, are neutralized at the place of formation, i.e. in the furnace.
In addition, a fluidized bed boiler is less sensitive to fluctuations in coal quality in terms of its design and operating principle. In the furnace of a conventional pulverized coal boiler, a huge amount of molten slag is formed, which often clogs the heat transfer surfaces and thereby reduces the efficiency and reliability of the boiler. In a fluidized bed boiler, coal is burned at a temperature below the melting point of the slag, and therefore the problem of clogging the heating surfaces with slag does not even arise. Such boilers can operate on lower quality coal, which in some cases can significantly reduce operating costs.
The fluidized bed combustion method is easily implemented in modular boilers with low steam output. According to some estimates, the investment in a thermal power plant with compact boilers operating on the principle of a fluidized bed may be 10-20% lower than the investment in a traditional thermal power plant of the same capacity. Savings are achieved by reducing construction time. In addition, the capacity of such a station can be easily increased with an increase in the electrical load, which is important for those cases when its growth in the future is not known in advance. The planning problem is also simplified, since such compact units can be quickly assembled as soon as the need arises to increase power generation.
Fluidized bed boilers can also be incorporated into existing power plants when generating capacity needs to be rapidly increased. For example, the energy company Northern States Power converted one of the pulverized coal boilers at the station in pcs. Minnesota in a fluidized bed boiler. The alteration was carried out in order to increase the power of the power plant by 40%, reduce the requirements for the quality of fuel (the boiler can even operate on local waste), more thorough cleaning of emissions and lengthen the service life of the station up to 40 years.
Over the past 15 years, the technology used in thermal power plants equipped exclusively with fluidized bed boilers has expanded from small pilot and pilot plants to large "demonstration" plants. Such a plant with a total capacity of 160 MW is being built jointly by Tennessee Valley Authority, Duke Power and Commonwealth of Kentucky; Colorado-Ute Electric Association, Inc. commissioned a 110 MW power generating unit with fluidized bed boilers. If these two projects are successful, and that of Northern States Power, a private sector joint venture with a combined capital of about $ 400 million, the economic risk associated with the use of fluidized bed boilers in the power industry will be significantly reduced.
Another method, which, however, already existed in a simpler form back in the middle of the 19th century, is the gasification of coal to produce "purely burning" gas. Such gas is suitable for lighting and heating and was widely used in the United States until World War II, when it was replaced by natural gas.
Initially, coal gasification attracted the attention of energy companies, who hoped to use this method to obtain fuel that burns without waste and thereby eliminate scrubbing. It has now become apparent that coal gasification has an even more important advantage: the hot combustion products of the generator gas can be directly used to drive gas turbines. In turn, the waste heat of the combustion products after the gas turbine can be utilized in order to obtain steam for driving a steam turbine. This combined use of gas and steam turbines, called a combined cycle, is now one of the most efficient ways to generate electrical energy.
The gas obtained by gasification of coal and freed from sulfur and particulate matter is an excellent fuel for gas turbines and, like natural gas, burns with almost no waste. The high efficiency of the combined cycle compensates for the inevitable losses associated with the conversion of coal to gas. Moreover, the combined cycle plant consumes significantly less water, since two-thirds of the capacity is developed by a gas turbine, which does not need water, unlike a steam turbine.
The viability of coal gasification combined cycle power plants has been proven by the Southern California Edison Cool Water plant. This station with a capacity of about 100 MW was put into operation in May 1984. It can operate on different types of coal. The emissions from the station are no different from those of the neighboring natural gas station in terms of purity. The sulfur oxides in the flue gases are kept well below the target by an auxiliary sulfur recovery system that removes almost all the sulfur in the feed fuel and produces pure sulfur for industrial purposes. The formation of nitrogen oxides is prevented by the addition of water to the gas before combustion, which lowers the combustion temperature of the gas. Moreover, the remaining unburned coal in the gasifier is remelted and converted into an inert vitreous material that, after cooling, meets the California solid waste requirements.
In addition to the higher efficiency and lower environmental pollution, combined cycle plants have another advantage: they can be built in several stages, so that the installed capacity is increased in blocks. This flexibility in construction reduces the risk of over- or under-investment associated with the uncertainty of growth in electricity demand. For example, the first stage of the installed capacity can operate on gas turbines, and use oil or natural gas instead of coal as fuel, if the current prices for these products are low. Then, as the demand for electricity grows, a waste-heat boiler and a steam turbine are additionally commissioned, which will increase not only the capacity, but also the efficiency of the station. Subsequently, when the demand for electricity increases again, it will be possible to build a coal gasification unit at the station.
The role of coal-fired thermal power plants is a key topic when it comes to preserving natural resources, protecting the environment and ways of developing the economy. These aspects of the problem at hand are not necessarily conflicting. The experience of using new technological processes of coal combustion shows that they can successfully and simultaneously solve problems of both environmental protection and reduce the cost of electricity. This principle was taken into account in a joint US-Canadian report on acid rain released last year. Guided by the proposals contained in the report, the US Congress is currently considering establishing a general national initiative to demonstrate and use "clean" coal combustion processes. The initiative, which will combine private capital with federal investment, aims to commercialize new coal combustion processes in the 1990s, including fluidized bed boilers and gas generators. However, even with the widespread use of new coal combustion processes in the near future, the growing demand for electricity cannot be satisfied without a whole range of coordinated measures to conserve electricity, regulate its consumption and increase the productivity of existing thermal power plants operating on traditional principles. Economic and environmental issues that are constantly on the agenda are likely to lead to completely new technological developments that are fundamentally different from those described here. In the future, coal-fired thermal power plants can turn into complex enterprises for the processing of natural resources. Such enterprises will process local fuels and other natural resources and produce electricity, heat and various products, taking into account the needs of the local economy. In addition to fluidized bed boilers and coal gasification plants, such plants will be equipped with electronic technical diagnostics and automated control systems and, in addition, it will be useful to use most of the by-products of coal combustion.

Thus, the opportunities for improving the economic and environmental factors of coal-based electricity production are very wide. The timely use of these opportunities depends, however, on the government's ability to implement balanced energy and environmental policies that create the necessary incentives for the electricity industry. It is necessary to take measures to ensure that new coal combustion processes are developed and implemented rationally, in cooperation with energy companies, and not as it was with the introduction of scrubber gas cleaning. All this can be achieved if costs and risks are minimized through well thought-out design, testing and improvement of small pilot plants, followed by widespread industrialization of the developed systems.

Thermal power plants provide people with almost all the energy they need on the planet. People have learned to receive electricity in other ways, but still do not accept alternatives. It is not profitable for them to use fuel, they do not refuse it.

What is the secret of thermal power plants?

Thermal power plants it is no coincidence that they remain irreplaceable. Their turbine generates energy in the simplest way, using combustion. Due to this, it is possible to minimize construction costs, which are considered fully justified. There are such objects in all countries of the world, so one should not be surprised at their distribution.

The principle of operation of thermal power plants built on the combustion of huge amounts of fuel. As a result, electricity appears, which is first accumulated and then distributed to certain regions. The schemes of thermal power plants remain almost constant.

What kind of fuel does the station use?

Each station uses a separate fuel. It is specially shipped so that your workflow is not disrupted. This moment remains one of the problematic ones, as transport costs appear. What types of equipment does it use?

• Coal;
• Oil shale;
• Peat;
• Fuel oil;
• Natural gas.

Thermal circuits of thermal power plants are based on a certain type of fuel. Moreover, minor changes are made to them, ensuring the maximum efficiency. If they are not done, the main consumption will be excessive, therefore, the resulting electric current will not justify.

Types of thermal power plants

The types of thermal power plants are an important issue. The answer to it will tell you how the necessary energy appears. Today, serious changes are gradually being made, where the main source will be alternative types, but so far their use remains inappropriate.

1. Condensing (IES);
2. Combined Heat and Power Plant (CHP);
3. State regional power plants (GRES).

The TPP power plant will require a detailed description. The views are different, so only consideration will explain why construction of this scale is being carried out.

Condensing (IES)

The types of thermal power plants start with condensing ones. Such CHP plants are used exclusively for generating electricity. Most often, it accumulates without spreading immediately. The condensation method provides maximum efficiency, therefore such principles are considered optimal. Today, in all countries, separate large-scale facilities are distinguished, providing vast regions.

Nuclear installations are gradually appearing to replace traditional fuel. Only replacement remains an expensive and time-consuming process, since fossil fuel operation differs from other methods. Moreover, the shutdown of any station is impossible, because in such situations, entire regions are left without valuable electricity.

Combined Heat and Power Plant (CHP)

CHP plants are used for several purposes at once. They are primarily used to generate valuable electricity, but burning fuel also remains useful for generating heat. As a result, cogeneration power plants continue to be applied in practice.

An important feature is that these types of thermal power plants are superior to others with a relatively small capacity. They provide separate areas, so there is no need for bulk supplies. Practice shows how profitable such a solution is due to the laying of additional power lines. The principle of operation of a modern thermal power plant is unnecessary only because of the environment.

State District Power Plants

General information about modern thermal power plants do not mark the state district power station. Gradually, they remain in the background, losing their relevance. Although state-owned district power plants remain useful in terms of energy production.

Various types of thermal power plants provide support for vast regions, but their capacity is still insufficient. During the Soviet era, large-scale projects were carried out, which are now being closed. The reason was the inappropriate use of fuel. Although their replacement remains problematic, since the advantages and disadvantages of modern thermal power plants are primarily noted for large amounts of energy.

Which power plants are thermal? Their principle is based on fuel combustion. They remain indispensable, although the calculations are actively carried out on an equivalent replacement. Thermal power plants continue to prove their advantages and disadvantages in practice. Because of this, their work remains necessary.

What is a coal-fired power plant? This is such an enterprise for the production of electricity, where coal (coal, brown) is the first in the energy conversion chain.

Let us recall the energy conversion chain at power plants operating in a cycle.

The first in the chain is fuel, in our case coal. It possesses chemical energy, which, when burned in a boiler, is converted into heat energy from steam. Thermal energy can also be called potential. Further, the potential energy of the steam at the nozzles is converted into kinetic energy. We will call kinetic energy velocity. This kinetic energy at the outlet of the turbine nozzles pushes the rotor blades and rotates the turbine shaft. This is where the mechanical energy of rotation is obtained. The shaft of our turbine is rigidly coupled to the shaft of the electric generator. Already in an electric generator, the mechanical energy of rotation is converted into electrical energy - electricity.

The coal-fired power plant has both advantages and disadvantages in comparison, for example, with a gas-fired one (we will not take into account modern CCGTs as usual).

Benefits of coal-fired power plants:

- low fuel cost;

- comparative independence from fuel supplies (there is a large coal warehouse);

- and ... that's it.

Disadvantages of coal-fired power plants:

- low maneuverability - due to additional restrictions on the output of slag from, if it is with liquid slag removal;

- high emissions compared to gas;

- lower efficiency for the supply of electricity - this adds losses in the boiler and an increase in own electrical needs due to the system of coal pulverization;

- more than at gas stations, the costs are due to the fact that abrasive wear and a greater number of auxiliary installations are added.

From this small comparison, it can be seen that coal-fired power plants lose out to gas-fired ones. Nevertheless, the world does not refuse to build them. This is primarily due to the economic point of view.

Take our country, for example. We have some places on the map where coal is mined in large quantities. The most famous is Kuzbass (Kuznetsk coal basin), also known as the Kemerovo region. There are quite a few power plants, the largest - and, besides them, there are also several smaller ones. All of them run on coal, with the exception of a few power units, where gas can be used as a backup fuel. In the Kemerovo region, such a large number of coal-fired power plants is due, of course, to the fact that coal is mined “close by”. There is practically no transport component in the price of coal for power plants. In addition, some owners of thermal power plants are also owners of coal enterprises. It seems clear why gas stations are not being built there.

In addition, the proven reserves of coal are incomparably greater than the proven reserves of natural gas. This already applies to the country's energy security.

Developed countries have taken a step further. So-called synthetic gas, an artificial analogue of natural gas, is made from coal. Some have already adapted to this gas, which can work as part of a CCGT unit. And here there are already completely different efficiency factors (higher) and harmful emissions (lower), in comparison with coal stations, and even with old gas stations.

So we can conclude that coal, as a fuel for the production of electricity, humanity will always use.