In early June, the ninth pulverized coal unit with an installed capacity of 225 MW was put into operation at the Cherepetskaya GRES in the Tula Region. The emergence of new coal capacities is rather an exception to the rule. Why in Russia coal generation is being supplanted by gas and nuclear, and in "green" Europe, on the contrary, it is gaining popularity - Peretok.ru figured it out.

Source: sdelanounas.ru

Coal-fired power plants have always played an important role in the Russian energy system. But in recent years, they have become significantly inferior to gas and nuclear counterparts. According to the Energy Research Institute (INEI) of the Russian Academy of Sciences, the share of coal-fired generation in Russia decreased from 27% in the early 2000s to 24% at the end of 2013 (from 19% to 16% in the European part of the country). New thermal capacities introduced in the power system also mainly use gas. Coal power units, however, are also being built - for example, at the same Cherepetskaya, Berezovskaya GRES, Krasnoyarsk CHPP-3, Blagoveshchensk CHPP and other stations, but there are much fewer of them than gas ones.

At the same time, power plants using coal, along with non-fuel sources, make a significant contribution to the diversification of the fuel balance, said Fyodor Veselov, head of the department for the development and reform of the electric power industry of the ERI RAS, speaking at the round table “Gas and coal generation in Russia: realities and prospects”. Today, about 110 Russian CHPPs and GRESs are coal-fired.

Difficulties of competition

Coal plants are important not only for the diversification of the country's fuel balance, but also for the operation of coal mining enterprises. For example, Novocherkasskaya GRES of Gazprom Energoholding is the largest consumer of coal in the Rostov region. According to the ERI RAS, power plants remain the most important consumers of Donetsk and Kansk-Achinsk coal, as well as deposits of Eastern Siberia.

However, the state of affairs for coal-fired power plants today leaves much to be desired. For example: six coal plants with a total capacity of 2.3 GW did not pass the competitive capacity selection for 2015 on general terms. They were "saved" by the status of forced. But the problem is obvious: it is difficult for power plants using coal to compete with more efficient gas generation.

“The key problem for coal-fired generation in the domestic market is the high level of competition from gas capacities. This, in particular, is explained by different pricing methods in the coal and gas markets: coal prices in the domestic market are formed taking into account trends in world markets, gas prices in Russia are regulated by the state,” the head of the sectoral economics department told Peretok.ru Fuel and Energy Complex of the Analytical Center under the Government of the Russian Federation Victoria Gimadi.

In addition, coal plants are more expensive to build and operate than gas plants. Thus, in the government decree on the parameters of capacity supply agreements (CDA), the level of capital costs for the construction of 1 kW of coal capacity is 49-53 thousand rubles, gas - 29-42 thousand rubles. The operating costs of coal-fired power plants are also higher (by about 53% in the CSA decree).

Another problem is environmental. Gas power units are “cleaner” in terms of emissions, and they do not need to have special sites for ash dumps. According to experts, today over 1 billion tons of ash and slag materials have been accumulated at Russian stations, and their processing (for example, for construction needs) has not yet been developed to full capacity.

There is a set of problems that are the same for both coal and other types of generation. In particular, the issue of non-payment by consumers and the inaccessibility of credit resources necessary to cover cash gaps are still acute. “At the same time, a feature of coal-fired generation is that in most cases it operates in the combined generation mode, which, on the one hand, significantly increases its efficiency and is its advantage. On the other hand, the difficulties of the heat market are completely shifted to electricity generation. There is still cross-subsidization between the heat and electricity markets. Low tariffs for thermal power plants for heat lead to a decrease in the economic efficiency of coal-fired plants,” Siberian Generating Company, which consumes approximately 16% of thermal coal in the Russian domestic market, told Peretok.ru.

The lack of stable rules for regulating the market also confuses the power industry - the constant change in the rules makes it extremely difficult to plan long-term investments. Investments in the repair and renewal of fixed assets suffer, which is one of the causes of accidents at power plants.

Sector participants do not ask for direct financial support, only wanting stable rules of the game. “Today, first of all, institutional measures are needed. We do not ask for direct financial support. If the market works properly, then coal-fired generation in itself is efficient enough to make money on its own. When regulating the industry, it is necessary to take into account all factors, including the maintenance of the normal technical condition of the equipment, and not only strive for maximum price containment,” say the Siberian Generating Company.

Experts believe that so far there are no prerequisites for the intensive development of coal-fired generation in Russia. “We should not expect a significant increase in the share of coal-fired thermal power plants in the country's fuel balance, most likely, their role will not change in the future (it will remain at about 25% in fuel consumption at thermal power plants),” Victoria Gimadi believes. In her opinion, coal stations will be built in the regions of Siberia and the Far East, which is determined by the relative territorial proximity of sources of coal consumption and its production. It was there that the project of the export-oriented Erkovetskaya TPP was conceived - a large power plant that can use coal from the field of the same name. Electricity generated by the thermal power plant is expected to be supplied to China. “The large-scale development of coal-fired generation in other areas (for example, in the central part of Russia) is unlikely due to low economic efficiency: a high level of competition between various types of generation, high transportation costs,” Victoria Gimadi believes.

Coal moved gas

Considering the prospects for coal generation, it is interesting to pay attention to Europe. On the one hand, the EU is one of the most vocal advocates of green energy technology – and yet a significant amount of coal capacity has been introduced there in recent years (coal is probably the last thing that comes to mind when thinking about clean technologies). Economic factors played their role. As Alexander Grigoriev, Head of the Fuel and Energy Complex Department at the Institute for Problems of Natural Monopolies (IPEM), noted, firstly, the gap between gas and coal prices has significantly decreased in the EU. According to the Institute, if in 2007 the ratio of gas and coal prices was 1.6, then in 2013 it reached 3.0. Secondly, the fall in prices for carbon quotas played a role (investments in gas generation are effective when the cost of quotas is more than 34-38 euros per ton of CO2). Thirdly, the economic crisis of 2008 also had an impact, which led to a decline in industrial production and, accordingly, electricity consumption.

These factors led to the fact that gas thermal power plants were underloaded. The owners mothballed many stations, some even dismantled. And it has become more profitable to build coal-fired thermal power plants. In addition, in Germany, the largest consumer of energy resources in Europe, after the Fukushima accident in March 2011, the government decided to gradually close all nuclear power plants.

Thus, according to IPEM, from 2012 to April 2015, 10.1 GW of coal generation was commissioned in European countries (mainly in Germany), which is almost six times more than the number of gas capacities commissioned. Another 8.6 GW of coal capacity is under construction: 3.3 GW in Poland, 2.7 GW in the Netherlands, 1.8 GW in Germany.

But one must understand that most EU countries do not have their own gas (except Norway), so the development of coal-fired generation is largely a forced measure due to economic factors. Thus, on the sidelines of the SPIEF, the head of the Italian energy company Enel, Francesco Starace, said that the situation with the growth of coal consumption in the electric power industry instead of gas will not last long, gas will be used more in the energy sector of European countries in the coming years. “I don’t think it will last long, this is a temporary situation. We do not plan to transfer our stations from gas to coal. I think that in the coming years gas will be much more important than coal in Europe,” Interfax quotes Starace.

Other related materials

Dancing on the corner

The rapid increase in the share of gas generation in the Russian energy system should stop in the coming years, and in the long term, the share of plants operating on blue fuel will completely decrease relative to the capacity of coal-fired thermal power plants. This is a sensible choice by the Russian authorities, which is based on the diversification of the fuel balance, the development of the domestic market for the coal industry, as well as the prospects for using new technologies to make coal-fired generation not only efficient, but also environmentally friendly.

March 27, 2014 at 02:12 pm

By studying the search queries of "Yandex", you can find interesting features of the dissemination of information about the energy sector. Search engine users search for “renewable energy” and “electric vehicles” 5-12 times more often than “coal energy”. In real life, the opposite is true - in 2017, coal-fired power plants generated in the world one and a half times more electricity than gas, and almost as much as all the others taken together, including nuclear power plants, hydroelectric power plants and renewable energy sources.

Indeed, since the days of the industrial boom in Great Britain and Germany, coal-fired generation has remained the backbone of the global electric power industry - it traditionally develops where it is necessary to ensure rapid economic growth "here and now" and where there is cheap and affordable thermal coal. Today, solid "black gold" is the dominant source of electricity in China, India, and the countries of Southeast Asia.

Another thing is also true. In the 20th century, coal-fired power plants operated much more quietly than they do now. People are becoming more and more sensitive to clean air, and old coal-fired power plants, with their low chimneys, are ideal for the role of the main air pollutants. This is almost always not the case - factories and cars emit just as much, but coal energy has to become cleaner and cleaner: put in expensive filters, trap sulfur in gypsum, restore nitrogen. On the other hand, more and more countries (already more than 40 and 20 subnational entities) agree on the need to reduce carbon dioxide emissions in order to avoid global climate change, and coal-fired thermal power plants are the first to come under pressure because they emit more CO 2 than gas. Carbon payments make coal energy less competitive, especially against the backdrop of natural gas and cheaper renewable energy. As a result, many investors are announcing the termination of financing projects in coal generation, the governments of a number of countries are announcing their abandonment, in developed countries, the volume of electricity from coal is decreasing.

Does this mean that tomorrow coal plants can be replaced by windmills? Definitely not, although there are indeed serious changes in this largest sector of the world's electric power industry, in the perspective of 20-30 years a massive exit from coal is unrealistic, even taking into account all the existing challenges. Over the years, the coal energy industry will have to seriously modernize and become cleaner, by widely introducing "clean coal" technologies. Coal plants can be cleaner than some gas plants, highly agile and flexible, and operate in peace and harmony with the townspeople living close to their fence - this has already been proven in Japan, Germany and other countries, but has yet to be realized in all others. Thus, the Isogo coal plant, comparable in capacity to the once coal-fired Kashirskaya GRES, is located 7 km from the center of Yokohama, the largest port in Japan with a population of 3.7 million people (Muscovites, for comparison, can try to imagine the Kashirskaya GRES somewhere in Sokolniki).

According to most forecasts of international agencies, the share of coal generation in the world will noticeably decrease (from 38% in 2017 to 20-25% by 2040), but in terms of generation, coal generation will remain approximately at the current level - with large-scale reductions in developed countries, a number of developing countries the economy will continue to grow. Will coal, which has a number of advantages - cheapness, availability, storage capacity, withstand global challenges? Obviously, there will be no unequivocal answer to this question, it all depends on which source in a particular region will show the greatest economic and environmental efficiency.

And what about in Russia? About the same thing is happening in our country: urban ecology was the main cause of the problems of coal thermal power plants from Moscow and St. Petersburg to Vladivostok, and cheap, accessible and convenient gas is gradually replacing coal from the fuel basket where gas pipelines reach. But not everywhere this method of solving environmental problems works. You can't gasify all of Siberia, for example, and it doesn't really want to: dozens of coal-fired single-industry towns operate only in Kuzbass, millions of Siberians receive not only electricity, but also heat from coal-fired thermal power plants.

A study by the Energy Center of the Moscow School of Management Skolkovo looks at three options for coal-fired generation in Russia in the future.

In the “let it go” scenario, gas will continue to gradually displace coal from the fuel mix of power plants, but in general, the output of coal-fired thermal power plants will remain at the current level until 2040. The other two options are polar and are already causing fierce debate.

The “green” scenario, in accordance with the study, involves the launch of a system of carbon fees in our country (by the way, the corresponding bill was sent to the departments for approval in early December 2018 by the Ministry of Economy) and the tightening of environmental policy in the energy sector. Coal generation will predictably become the first victim of such a development of events, and after a step, society and the government will have to decide the issue of supporting coal-producing regions.

The "coal" scenario may consist in stimulating coal energy, "tied" to increasing its efficiency and "cleanliness". We can talk about the development of coal-fired CHP plants with the closure of coal-fired boilers, the development of domestic “clean coal” technologies, a serious modernization of the industry, including using already launched mechanisms in the heat energy market (alternative boiler house) and electric energy (DPM-2) and additional sources.

Society, authorities, energy companies must decide which option they are leaning towards. It's not a question of what news and queries will be at the top of the search engines. This is a question of the quality of life of millions of people directly or indirectly connected with coal generation.

Description

The main purpose of coal-fired mini-CHPs is to solve the problems of providing heat, steam and electricity to industrial facilities in which, according to the conditions of the technological process, steam is needed, especially for areas that, for a number of reasons, do not have enough gas or liquid fuel (or use this type of fuel is unprofitable or difficult), and areas of direct coal mining. Design, construction and reconstruction of coal-fired boiler houses and mini-CHPs in a special way differs from similar work on gas and diesel boiler houses and requires the solution of additional tasks to ensure reliable performance and high efficiency. furnace KSOMOD. Further, from the bunker, coal is fed in portions in automatic mode to the KSOMOD combustion chamber (loading window 1200x250). In the KSOMOD combustion chamber with a screw bar, coal burns in a fluidized bed. Flue gases give off heat in the hot water boiler and economizer. Flue gases with the help of a smoke exhauster are sent to the common gas duct, and then to the steel chimney of the boiler room. The remains of burnt coal - slag and ash are removed by a conveyor to the slag accumulator bunker. The slag is removed from the bunker by trucks. All electrical equipment in the coal-fired boiler house, as well as the boiler unit, is controlled from the control cabinet. The circulation of water in the boiler room is forced, carried out using a centrifugal pump of the primary circuit. The return water of the primary circuit, which has given off heat to the network water in the plate heaters, returns to the inlet to the economizer of the boiler, where it heats up to 70 degrees C and is fed into the lower collectors located at the back of the boiler. The heated water exits the boiler in the upper part and enters again to the inlet of plate heat exchangers - network water heaters. The boiler is supplied with prepared water. The control panel provides automatic control of the boiler house operation (starting and stopping according to a given program), as well as an emergency stop (blocking the fuel supply, operation of a blower fan, smoke exhauster). If you are in need of a reliable and efficient heating system, technology, then you will find the best solution for modular CHP boilers to coal-fired mini-CHPs using energy-saving steam turbines to generate heat and electricity cheaply (See section steam turbines and turbo drives).

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The main advantages of using coal in boiler houses and mini-CHPs are: 1. Patented technology for fuel supply and combustion of coal in mini-CHPs; 2. Reliable system of mechanization and automation for coal-fired mini-CHP; 3. Efficient combustion at low coal quality (omnivorous technology XOMOD is used); 4. Low cost of generated electricity, heat; 5. Possibility of fast construction; 6. Low fuel consumption; 7. Long service life of the equipment; 8. Environmental safety.

Thermal power plants produce about 80% of electricity in our country. These stations operate on coal, peat, shale, natural gas. Consider, for example, the principle of operation of a coal-fired thermal power plant. Hard coal is brought to the station by rail, unloaded and stored.

It is known that large pieces of coal burn poorly and slowly.

It is possible to significantly improve the combustion process by burning coal dust. Therefore, the imported coal is first crushed, and then in ball mills, heavy steel balls turn the pieces of coal into the smallest dust. This dust is blown into the furnace of the steam boiler by a stream of hot air through special burners. Burning on the fly, the dust turns into a bright torch of flame with a combustion temperature of up to 1500 degrees. The flame heats the water in thin tubes that cover the side walls of the boiler furnace from the inside. Hot flue gases rush through the chimney, meeting boiling tubes on their way.

In them, the water heated by the flame turns into steam.

Further, the gases enter the economizer - a device for replenishing water reserves in the boiler, and heat the water in it. Then the gases enter the air heater, which heats the air that enters the burners of the boilers together with coal dust.

Coal burns well if there is good draft in the furnace. Strong traction gives a high pipe. However, for powerful boilers, the pipes are not enough - you have to additionally install powerful smoke exhausters. Flue gases carry a lot of ash. Therefore, they are cleaned in ash collectors, and the ash is transported to ash dumps.

The complexity of the above coal combustion process is fully justified by the high efficiency. such a thermal power plant - up to 90% of the heat contained in coal is converted into electrical energy.

So, the fuel burned down, transferring its energy to the water. The water in the boiler turned into steam. But this steam cannot yet be allowed into the turbine - it is not hot enough and, cooling down, will quickly turn into drops of water. Therefore, steam enters the coils of the superheater located in the chimney between the boiler pipes and the economizer. There, the steam is additionally heated to a very high temperature of 500-600 degrees at a pressure of 150-250 atmospheres. Such compressed and superheated steam is sent through steam pipelines to steam turbines.

Turbines at thermal power plants come in not only different capacities, but also different designs. There are small single-stage turbines with a capacity of tens of kilowatts. And there are also multi-stage turbines - giants with a capacity of 500 to 1500 kilowatts.

The higher the steam temperature and pressure at the turbine inlet and the lower they are at the outlet, the more steam energy the turbine uses.

To reduce the temperature and pressure of the steam at the outlet of the turbine, it is not released into the air, but is sent to the condenser. Inside the condenser, cold water circulates through thin brass tubes. It cools the steam, turning it into water, called condensate. From this, the pressure in the condenser becomes 10-15 times lower than atmospheric pressure.

So, steam, which has given up almost all of its energy, turns into condensate - very pure water that does not contain chemical or mechanical impurities. This purified water is needed in boilers, so the condensate is pumped back into the boiler, closing the cycle of water movement at the thermal plant.

Typically, a powerful steam turbine has a speed of 3000 revolutions per minute and its shaft is directly connected to the shaft of an electric generator that produces three-phase alternating current with a frequency of 50 cycles per second and a voltage of 10-15 thousand volts. Electricity is the main and most important product of a thermal power plant.

At most stations, the generated electricity is divided into three streams

Part of it is sent by cable to consumers located nearby. Another small part - up to 8% - goes to meet the station's own technological needs. Most of the generated electricity is intended for cities and industrial enterprises located at a great distance - tens and hundreds of kilometers from the station. Over long distances, electricity is transmitted via high-voltage lines at a voltage of 110, 220, 400, 500 and 800 thousand volts. To create such a high voltage, the station has a step-up transformer substation and a high voltage switchgear. High-voltage power lines diverge from it to cities and enterprises.

The described power plant has a closed water cycle, produces only electric current, and is called a "condensing" plant (because all the steam goes to the condenser).

However, in addition to electricity, steam and hot water are also needed. For their production at power plants, special heating turbines are installed. They consist of two parts - high and low pressure cylinders. It exhausts steam in the high-pressure cylinder, and only part of the steam enters the low-pressure cylinder. The other part is taken from the turbine and sent to the heat exchanger. There, very hot turbine steam heats the water, turning it into secondary steam. Then the turbine steam goes on its way to the condenser, and the secondary steam is sent to the consumer.

In the city, part of the secondary steam enters heat exchangers - boilers, in which it heats water for space heating and domestic needs in residential buildings.

Thermal power plants that simultaneously provide electricity and heat are called combined heat and power plants (CHP). It is advantageous to build condensing power plants near rich coal deposits, peat bogs, if there are suitable reservoirs nearby.

Despite the remoteness of such a station from the city, it is much easier and more profitable to transmit electric current through wires than to carry fuel (peat, coal, etc.).

And near cities and large factories, it is profitable to build a thermal power plant. These stations will supply the city with heat and electricity. Modern thermal power plants operating on natural gas practically do not pollute the air and are indispensable companions of any city or large industrial enterprise. In addition, the construction of a thermal power plant is much cheaper and takes less time than, for example, the construction of a hydroelectric power station. Gas-fired CHP plants can be quickly built in any area, being the safest source of energy.

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13.12.2010
  Russian President Dmitry Medvedev at a meeting of the country's Security Council on December 13, instructed the government to develop energy security doctrine. This is reported RIA News
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The President noted that now in Russia, gas is unreasonably often used at power plants. "We are still unjustifiably spending our gas reserves, switching to "blue fuel" even those thermal power plants and boiler houses where coal could be used efficiently," the president is quoted as saying. "Interfax". There are such constructive solutions on the basis of which it is possible to modernize existing and build new thermal power plants, while reducing the cost of electricity production and reducing harmful emissions into the environment

RICHARD E. BOLZHEISER, KURT E. IGER
"In the world of science" (Scientific American) No. 11 1987

In 1879, when Thomas Alva Edison invented the incandescent lamp, the era of electrification began. Generating large amounts 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) ran on coal. As more and more stations were built in the country, dependence on coal increased. Since the First World War, about half of the annual electricity production in the United States came from coal-fired thermal power plants. In 1986, the total installed capacity of such power plants was 289,000 MW, and they consumed 75% of the total (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 to come (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. 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 effects, in particular acid rain. Since the end of the 1960s, the attractiveness of coal-fired thermal power plants has declined sharply due to the tightening of requirements for environmental pollution by gaseous and solid emissions in the form of ash and slag. The costs of addressing 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 mainly aimed at increasing the capacity of existing installations. At the same time, completely new processes are being developed for the waste-free combustion of coal, 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 periods.

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, coal is crushed into dust, due to which almost the same combustion efficiency is achieved as when burning combustible 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 produce 1 million kWh of electrical energy. During the same time, the boiler emits about 100,000 m3 of gases into the atmosphere.
The generated steam passes through the superheater, where its temperature and pressure increase, and then enters the high pressure turbine. The mechanical energy of the turbine rotation is converted by an electric generator into electrical energy. In order to obtain a higher energy conversion efficiency, the steam from the turbine is usually returned to the boiler for reheating and then drives one or two low pressure turbines and only then is condensed by cooling; the condensate is returned to the boiler cycle.
Thermal power plant equipment includes fuel feeders, boilers, turbines, generators, as well as sophisticated cooling, flue gas cleaning and ash removal systems. All these main and auxiliary systems are designed to operate with high reliability for 40 years or more at loads that can vary from 20% of the plant's installed capacity to maximum. The capital cost of equipping a typical 1,000 MW thermal power plant typically exceeds $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 electricity produced has decreased by eight times. Accordingly, there was a decrease in the cost of 1 kW of installed capacity of thermal power plants: if in 1920 it was $ 350 (in 1967 prices), then in 1967 it decreased to $ 130. The price of electricity supplied also fell over the same period from 25 cents to 2 cents for 1 kW tea.
However, since the 1960s, the pace of progress has begun 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 the materials from which boilers and turbines are made. Since the beginning of the 1970s, these technical factors have been aggravated by new economic and organizational reasons. In particular, capital expenditures have risen sharply, electricity demand growth has slowed down, requirements for environmental protection from harmful emissions have become more stringent, and the timeframe for implementing power plant construction projects has lengthened. As a result, the cost of generating electricity from coal, which had been declining for many years, has risen sharply. Indeed, 1 kW of electricity produced by new thermal power plants now costs more than in 1920 (in comparable prices).

Southern California Edison's "Cool Water" DEMONSTRATION PLANT processes 1,000 tons of hard coal daily to produce zero-burn gas.
The products of combustion drive the gas turbine of the electric generator. The waste heat from the exhaust gases is used to produce steam, which drives a steam turbine in another power generator.
The photo shows two coal bunkers (center). To their right is a gasification plant, a gas cooling system and power generating equipment.

In the past 20 years, the cost of coal-fired thermal power plants has been most affected by increased requirements for the removal of gaseous,
liquid and solid waste. The gas cleaning and ash removal systems of 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 the flue gas desulfurization plant, often referred to as a wet scrubbing system. The wet dust collector (scrubber) retains sulfur oxides, which are the main pollutant formed during the combustion of coal.
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 sulfite or calcium sulfate (gypsum). Gypsum can be easily removed or, if clean enough, can be marketed as a building material. In more complex and expensive scrubber systems, gypsum sludge can be converted into sulfuric acid or elemental sulfur, more valuable chemicals. Since 1978, the installation of scrubbers has been mandatory at all thermal power plants under construction using pulverized coal fuel. As a result, the US energy industry now has more scrubber installations 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. Installation of scrubbers at existing plants, originally designed without wet scrubbing, costs 10-40% more than at new plants. The operating costs of scrubbers are quite high whether they are installed in old or new plants. Scrubbers generate huge amounts of gypsum sludge that must be kept in settling ponds or dumped, creating a new environmental problem. For example, a thermal power plant with a capacity of 1000 MW, operating on coal containing 3% sulfur, produces so much sludge per year that it 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, the water flow 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 spent on driving pumps and smoke exhausters and on heating flue gases after gas cleaning, which is necessary to prevent condensation and corrosion in chimneys.
Widespread use of scrubbers in the American power industry was neither easy nor cheap. The first scrubber installations were much less reliable than the rest of the station equipment, so 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 explained by the fact that industrial application of scrubber technology was started prematurely. Only now, after 25 years of experience, the reliability of scrubber systems has reached an acceptable level.
The cost of coal-fired thermal plants has risen not only because of the mandatory emission control systems, but also because the cost of construction itself has skyrocketed. Even taking into account inflation, the unit cost of installed capacity of coal-fired thermal plants is now three times higher than in 1970. Over the past 15 years, the “scale effect”, i.e., the benefit from building large power plants, has been negated by a significant increase in construction costs . In part, this rise in prices reflects the high cost of financing long-term capital projects.
The impact of project delay can be seen in the example of Japanese energy companies. Japanese firms are usually more agile than their American counterparts in dealing with organizational, technical and financial problems that often delay the commissioning of large construction projects. In Japan, a power plant can be built and put into operation in 30-40 months, while in the US, 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 smaller modular plants that can be quickly transported and installed in an existing plant to meet growing demand. Such plants can be put into operation in a shorter time and therefore pay for themselves faster, even if the return on investment remains constant. Installing new modules only when an increase in system capacity is required can result in net savings of up to $200/kW, even though economies of scale are lost with smaller installations.
As an alternative to building new power generating facilities, energy companies have also practiced retrofitting existing old power plants to improve their performance and extend their life. This strategy, of course, requires less capital expenditure than the construction of new plants. This trend is also justified because the power plants built about 30 years ago are not morally obsolete yet. In some cases, they even operate with higher efficiency, since they are not equipped with scrubbers. Old power plants are acquiring an increasing share in the country's energy sector. In 1970, only 20 generating facilities in the US were over 30 years old. By the end of the century, 30 years will be the average age of coal-fired thermal power plants.
Energy companies are also looking for ways to reduce operating costs at stations. To prevent energy losses, it is necessary to provide timely warning of deterioration in the performance of the most important areas of the facility. Therefore, continuous monitoring of the state of units and systems becomes an important part of the operational service. Such continuous monitoring of the natural processes of wear, corrosion and erosion allows plant operators to take timely action and prevent the emergency failure of power plants. The significance of such measures can be correctly assessed if one considers, for example, that the forced downtime of a 1000 MW coal-fired plant could cost the power company $1 million a day, mainly because the ungenerated energy must be compensated by supplying energy from more expensive sources.
The growth of specific costs for transportation and processing of coal and for ash removal has made the quality of coal (determined by the content of moisture, sulfur and other minerals) an important factor that determines the performance and economics of thermal power plants. Although low-grade coal may cost less than high-grade coal, it costs much more to produce the same amount of electricity. The cost of transporting more low-grade coal may outweigh the benefit of its lower price. In addition, low-grade coal usually generates more waste than high-grade coal, and, consequently, high costs for ash removal are required. Finally, the composition of low-grade coals is subject to large fluctuations, which makes it difficult to "tune" the plant's fuel system to operate at the highest possible efficiency; in this case, the system must be adjusted so that it can operate with the worst expected coal quality.
In existing power plants, the quality of coal can be improved, or at least stabilized, by removing certain impurities, such as sulfur minerals, before burning. In treatment plants, the ground "dirty" coal is separated from impurities in many ways, using differences in specific gravity or other physical characteristics of the coal and impurities.
Despite these efforts to improve the performance of existing coal-fired thermal power plants, an additional 150,000 MW of generating capacity will need to be installed in the United States by the end of the century if electricity demand grows at an expected rate of 2.3% per year. To remain competitive with coal in an ever-expanding energy market, energy companies will need to adopt innovative new ways of burning coal that are more efficient than traditional ones in three key areas: less pollution, shorter construction times for power plants, and better plant performance and performance. .

FLUIDIZED COAL BURNING reduces the need for ancillary plants to treat power plant emissions.
A fluidized layer of a mixture of coal and limestone is created in the boiler furnace by an air flow in which solid particles are mixed and in suspension, i.e. they behave in the same way as in a boiling liquid.
Turbulent mixing ensures complete combustion of coal; while limestone particles react with sulfur oxides and capture about 90% of these oxides. Since the boiler heating coils directly touch the fluidized bed of the fuel, steam generation is more efficient than in conventional pulverized coal steam boilers.
In addition, the temperature of burning coal in the fluidized bed is lower, which prevents the melting of boiler slag 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 is cooled, de-solidified and desulphurised, it can be used as fuel for gas turbines and then to produce steam for a steam turbine (combined cycle).
A combined cycle plant emits fewer pollutants into the atmosphere than a conventional coal-fired thermal plant.

Currently, more than a dozen ways of burning coal 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 a steam boiler furnace, which is designed so that crushed coal mixed with limestone particles is maintained above the furnace grate in a suspended ("pseudo-liquefied") state by a powerful ascending air flow.
Suspended particles behave in essentially the same way as in a boiling liquid, i.e., they are in turbulent motion, which ensures the high efficiency of the combustion process. The water pipes of such a boiler are in direct contact with the "fluidized bed" of the burning fuel, as a result of which a large proportion of the heat is transferred by thermal conduction, which is much more efficient than the radiative and convective heat transfer in a conventional steam boiler.
The fluidized bed coal fired boiler has a larger tube heat transfer area than a conventional pulverized coal fired boiler, which lowers the furnace temperature and thus reduces the formation of nitrogen oxides. (While the temperature in a conventional boiler can be above 1650°C, in a fluidized bed boiler it is in the range of 780-870°C.) Moreover, limestone mixed with coal binds 90 percent or more of the sulfur released from coal during combustion, since the lower operating temperature promotes the reaction between sulfur and limestone with the formation of sulfite or calcium sulfate. In this way, environmentally harmful substances formed during the combustion of coal are neutralized at the place of formation, i.e. in the furnace.
In addition, the fluidized bed boiler is less sensitive to fluctuations in coal quality due to 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, the coal burns at a temperature below the melting point of the slag, and therefore the problem of fouling of the heating surfaces with slag does not even arise. These boilers can operate on lower quality coal, which in some cases can significantly reduce operating costs.
The method of combustion in a fluidized bed is easily implemented in boilers of a modular design with a small steam capacity. According to some estimates, the investment in a thermal power plant with compact fluidized bed boilers can be 10-20% lower than in a conventional thermal plant of the same capacity. Savings are achieved by reducing construction time. In addition, the power of such a plant can be easily increased with an increase in electrical load, which is important for those cases when its growth in the future is not known in advance. The problem of planning is also simplified, since such compact installations can be quickly installed as soon as the need arises to increase power generation.
Fluidized bed boilers can also be incorporated into existing power plants when the power generation needs to be increased quickly. 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 plant capacity by 40%, reduce the requirements for fuel quality (the boiler can operate even on local waste), more thorough emissions cleaning and extend the life of the plant 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 semi-industrial plants to large "demonstration" plants. Such a station with a total capacity of 160 MW is being built jointly by the Tennessee Valley Authority, Duke Power and Commonwealth of Kentucky; Colorado-Ute Electric Association, Inc. commissioned a 110 MW power generation plant with fluidized bed boilers. If these two projects are successful, as well as that of Northern States Power, a private sector joint venture with a total capital of approximately $400 million, the economic risk associated with the use of fluidized bed boilers in the energy industry will be significantly reduced.
Another method, which, however, already existed in a simpler form as early as the middle of the 19th century, is the gasification of coal with the production of a "purely burning" gas. Such gas is suitable for lighting and heating and was widely used in the US until World War II, until it was displaced 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 get rid of scrubber cleaning. It has now become clear that coal gasification has a more important advantage: the hot products of combustion of producer 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 to drive the steam turbine. This combined use of gas and steam turbines, called the combined cycle, is now one of the most efficient ways to produce electrical energy.
The gas obtained from the gasification of coal and freed from sulfur and particulate matter is an excellent fuel for gas turbines and, like natural gas, burns almost without waste. The high efficiency of the combined cycle compensates for the inevitable losses associated with the conversion of coal to gas. Moreover, a combined cycle plant consumes significantly less water, since two-thirds of the power is developed by a gas turbine, which does not need water, unlike a steam turbine.
The viability of combined cycle power plants operating on the principle of coal gasification has been proven by the experience of operating the Cool Water plant of Southern California Edison. This station with a capacity of about 100 MW was put into operation in May 1984. It can operate on different grades of coal. The plant's emissions do not differ in purity from those of a neighboring natural gas plant. The sulfur oxide content of the flue gases is kept well below regulatory levels by an auxiliary sulfur recovery system that removes almost all of the sulfur in the feed fuel and produces pure sulfur for industrial use. The formation of nitrogen oxides is prevented by adding water to the gas before combustion, which reduces the combustion temperature of the gas. What's more, the unburned coal remaining in the gasifier is melted down and converted into an inert glassy material that, after cooling, meets California's solid waste requirements.
In addition to higher efficiency and lower environmental pollution, combined cycle plants have another advantage: they can be built in several phases, so that the installed capacity is increased in blocks. This construction flexibility reduces the risk of over- or under-investment associated with the uncertainty of electricity demand growth. For example, the first stage of installed capacity may run 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 put into operation, which will increase not only the power, but also the efficiency of the plant. Subsequently, when the demand for electricity increases again, a coal gasification plant can be built at the plant.
The role of coal-fired thermal power plants is a key topic when it comes to preserving natural resources, protecting the environment and developing the economy. These aspects of the problem at hand are not necessarily conflicting. The experience of using new technological processes for burning coal shows that they can successfully and simultaneously solve the problems of both protecting the environment and reducing the cost of electricity. This principle was taken into account in a joint US-Canadian report on acid rain published last year. On the basis of the report's proposals, the US Congress is currently considering establishing a national general initiative to demonstrate and apply "clean" coal combustion processes. This 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 the emergence of completely new technological developments that are fundamentally different from those described here. In the future, coal-fired thermal power plants can turn into integrated 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 whether the government can pursue a balanced energy production and environmental policy that would create the necessary incentives for the electricity industry. Care must be taken to ensure that new coal combustion processes are developed and implemented rationally, in cooperation with energy companies, and not in the way that was the case with the introduction of scrubber gas cleaning. All this can be achieved by minimizing cost and risk through well thought-out design, testing and improvement of small pilot experimental plants, followed by widespread industrial implementation of the developed systems.