Combined-cycle power plants are called(CCGT), in which the heat of the exhaust gases of the gas turbine is directly or indirectly used to generate electricity in the steam turbine cycle.

On fig. 2.1 shows a schematic diagram of the simplest CCGT of the so-called recycling type. Outgoing gases from the gas turbine are fed into waste heat boiler

Rice. 2.1.

/ - superheater; 2 - evaporator; 3 - economizer; 4 - drum; 5 - steam turbine condenser; 6 - feed pump; 7 - evaporator downpipe; 8 - evaporator riser pipes

torus- a counterflow type heat exchanger, in which, due to the heat of hot gases, steam of high parameters is generated, which is directed to a steam turbine.

The waste heat boiler is a shaft of rectangular cross section, in which heating surfaces are located, formed by finned tubes, inside which the working medium of the steam turbine plant (water or steam) is supplied. In the simplest case, the heating surfaces of the waste heat boiler consist of three elements: economizer 3, evaporator 2 and superheater 1. The central element is the evaporator, consisting of a drum 4 (a long cylinder half-filled with water), several downcomers 7 and fairly densely installed vertical rough of the evaporator proper 8. The evaporator works on the principle of natural convection. The evaporation pipes are located in a zone of higher temperatures than the lower ones, so the water in them heats up, partially evaporates, becomes lighter and rises up into the drum. The vacated space is filled with more cold water downpipes from the drum. Saturated steam is collected at the top of the drum and directed to the superheater tubes. 1. Steam consumption from the drum 4 compensated by water supply from the economizer 3. In this case, the incoming water, before completely evaporating, will repeatedly pass through the evaporator pipes. Therefore, the described waste heat boiler is called a boiler with natural circulation.

In the economizer, the incoming feed water is heated almost to the boiling point (10-20 °C less than the temperature of saturated steam in the drum, which is completely determined by the pressure in it). From the drum, dry saturated steam enters the superheater, where it is superheated above the saturation temperature. The temperature of the resulting superheated steam T 0 is always, of course, lower than the temperature of the gases 0 p coming from the gas turbine (usually by 25-30 ° C).

Under the scheme of the cola-utilizer in fig. 2.1 shows the change in temperatures of gases and the working fluid (steam, water) when they move towards each other. The temperature of the gases gradually decreases from the value 0 Г at the inlet to the value 0 ux of the temperature of the flue gases. The feed water moving towards increases its temperature in the economizer to the boiling point (point A). WITH At this temperature (on the verge of boiling), water enters the evaporator. It evaporates water. At the same time, its temperature does not change (process A-/;). At the point b the working fluid is in the form of dry saturated steam. Further, in the superheater, it overheats to the value / 0 .

The steam formed at the outlet of the superheater is sent to the steam turbine, where, expanding, it does work. From the turbine, the spent bunk enters the condenser 5, condenses and, with the help of a feed pump 6, which increases the pressure of the feed water, is sent back to the waste heat boiler.

Thus, the fundamental difference between a steam power plant (SPU) of a CCGT and conventional CSP TPP consists only in the fact that the fuel in the waste heat boiler is not burned, and the heat necessary for the operation of the PSU CCGT is taken from the exhaust gases of the GTU. However, it is immediately necessary to note a number of important technical differences between the PSU CCGT and the PSU TPP:

1. The temperature of the exhaust gases of the gas turbine 0 G is almost unambiguously determined by the temperature of the gases in front of the gas turbine [see. relation (1.2)] and the perfection of the gas turbine cooling system. In most modern gas turbines, as can be seen from Table. 1.2, the exhaust gas temperature is 530-580 °C (although there are separate gas turbines with temperatures up to 640 °C). According to the conditions of reliability of the economizer pipe system operation when operating on natural gas, the temperature of the feed water 1 p at the inlet to the waste heat boiler should not be less than 60 °С. The temperature of flue gases 0x leaving the waste heat boiler is always higher than the temperature t n V. In reality, it is at the level of 0 х « 100 °С, therefore, the efficiency of the waste heat boiler (HRSG) will be

where for evaluation it is assumed that the gas temperature at the inlet to the waste heat boiler is 555 °C, and the outside air temperature is 15 °C. When operating on gas, a conventional energy boiler of a thermal power plant has an efficiency of 94%. Thus, the waste heat boiler in a CCGT has an efficiency that is significantly lower than that of a TPP boiler.

2. Further, the efficiency of the steam turbine plant (STP) of the considered CCGT is significantly lower than the efficiency of the STP of a conventional TPP. This is due not only to the fact that the parameters of the steam generated by the waste heat boiler are lower, but also to the fact that the CCGT PTU does not have a regeneration system. And she, in principle, cannot have it, since the temperature increase t n c will lead to an even greater reduction in the efficiency of the waste heat boiler.

An idea about the structure of a power plant with a CCGT is given in Fig. 2.2, which shows a TPP with three power units. Each power unit consists of two adjacent gas turbines 4 type V94.2 from Siemens, each of which directs its high-temperature flue gases to its own waste heat boiler 8. The steam generated by these boilers is sent to one steam turbine 10 with electric generator 9 and a condenser located in the condensation room under the turbine. Each such power unit has a total capacity of 450 MW (each gas turbine and steam turbine has a capacity of approximately 150 MW). Between outlet diffuser 5 and waste heat boiler 8 install a bypass (bypass) chimney 12 and gas-tight gate b. The damper allows you to cut off the waste heat boiler 8 from the gases of the gas turbine and send them through the bypass pipe to the atmosphere. Such a need may arise in case of malfunctions in the steam turbine part of the power unit (in the turbine, waste heat boiler, generator, etc.), when

Rice. 2.2. The device of a power plant with a CCGT (prospect of the company Siemens):

1 - combined air handling unit (KVOU); 2 - block transformer; 3 - GTU generator; 4 - GTU type U94.2; 5 - transitional diffuser from the gas turbine to the bypass pipe; 6 - gate valve; 7 - deaerator; 8 - waste heat boiler of vertical type; 9 - steam turbine generator; 10 - steam turbine; 11 - rain damper of the charcoal boiler; 12 - bypass pipe; 13 - room for liquid fuel purification equipment; 14 - liquid fuel tanks

it needs to be disabled. In this case, the power of the power unit will be provided only by the gas turbine, i.e. the power unit can carry a load of 300 MW (albeit with reduced efficiency). The bypass pipe is also very helpful during power unit start-ups: with the help of a gate, the waste heat boiler is cut off from the gases of the gas turbine, and the latter are brought to full capacity in a matter of minutes. Then you can slowly, in accordance with the instructions, put into operation the waste heat boiler and the steam turbine.

During normal operation, the gate, on the contrary, does not let the hot gases of the gas turbine into the bypass pipe, but directs them to the waste heat boiler.

The gas-tight gate has a large area, is a complex technical device, the main requirement for which is high density, since every 1% of heat lost through leaks means a decrease in the efficiency of the power unit by about 0.3%. Therefore, sometimes they refuse to install a bypass pipe, although this significantly complicates operation.

Between the waste heat boilers of the power unit, one deaerator is installed, which receives condensate for deaeration from the steam turbine condenser and distributes it to two waste heat boilers.

As in any other car that uses a similar device, the main task of the clutch is to make life easier for the driver, and more specifically, the pneumohydraulic booster makes it so that the driver has to spend less effort when depressing the clutch pedal. And for heavy vehicles, such relief is very helpful.

Consider, for example, the clutch device and other MAZ models. The principle of operation is as follows - pressing the pedal causes an increase in pressure on the hydraulic piston, and the piston of the follower experiences the same pressure. As soon as this happens, the automation of the tracking device turns on and changes the pressure level in the power pneumatic cylinder. The device itself is mounted on the crankcase flange.

There are a lot of options for amplifiers, but if we talk specifically about Minsk trucks, then most of them are united by one not-too-pleasant feature - it often happens that liquid begins to leak from the CCGT during operation. Naturally, the first thought that comes to mind is that this may be a sign of a breakdown due to overloads, and a serious one at that.

If there were no such overloads after installing (replacing) the amplifier, another version immediately arises - they slipped a defective one! And what, today everyone is forging, even individual or 238, even Brabus SV12 assembled to the "gelding" of the six hundredth. Probably, only components for the Russian "Kalina" and the Ukrainian "Tavria" are not faked - the material turns out to be more expensive.

But jokes aside, especially since the leakage of fluid from the pneumohydraulic amplifier is a serious symptom. In fact, everything is not so tragic, the fact is that this may not be evidence of a breakdown, but just an incorrect adjustment. “Only”, because the repair of the CCGT MAZ clutch is not difficult and, with certain skills, will not take much time.

The most important thing is to determine the working stroke for the booster rod. To do this, you will need to pull the rod itself away from the lever, while moving it to the side so that it completely comes out of the body. After the clutch lever must be turned in the direction from the rod, choosing all possible gaps. Then the distance between the surface of the lever and the end of the stem is measured.

If this distance is less than 50 mm, then this means that in operation the plunger of the rod will go out to the stop, thereby opening the fluid outlet. All that is required is to move the lever one slot closer to the amplifier. If the distance is greater, then the cause of leakage is different, and it is better to conduct a more detailed check in a car service. However, we repeat, but most often there will be plenty of adjustment.

Device, scheme CCGT MAZ

1 6430-1609205 Cylinder body
2 6430-1609324 Cuff
3 6430-1609310 Ring
4 6430-1609306 Washer
5 6430-1609321 Cuff
6 6430-1609304 Sleeve
7 Ring 033-036-19-2-2 Ring 033-036-19-2-2
8 6430-1609325 Cuff
9 Ring 018-022-25-2-2 Ring 018-022-25-2-2
10 6430-1609214 Follower piston
11 Ring 025-029-25-2-2 Ring 025-029-25-2-2
12 6430-1609224 Spring
13 Ring 027-03 0-19-2-2 Ring 027-03 0-19-2-2
14 6430-1609218 Saddle
15 500-3515230-10 Clutch booster valve
16 842-8524120 Spring
17 Ring 030-033-19-2-2 Ring 030-033-19-2-2
18 6430-1609233 Support
19 6430-1609202 Cylinder
20 373165 Stud M10x40
21 6430-1609203 Sleeve
22 375458 Washer 8 OT
23 201458 Bolt М8-6gх25
24 6430-1609242 Spring
25 6430-1609322 Cuff
26 6430-1609207 Piston
27 6430-1609302 Ring
28 Ring 020-025-30-2-2 Ring 020-025-30-2-2
29 6430-1609236 Shaft
30 6430-1609517 Seal
31 6430-1609241 Stem
32 6430-1609237 Cover
33 6430-1609216 Cylinder plate
34 220050 Screw М4-6gх8
34 220050 Screw М4-6gх8
35 64221-1602718 Protective cap
36 378941 Plug M14x1.5
37 101-1609114 bypass valve
38 12-3501049 Valve cap
39 378942 Plug M16x1.5
40 6430-1609225 Breather
41 252002 Washer 4
42 252132 Washer 14
43 262541 Plug kg 1/8"
43 262541 Plug kg 1/8"
44 Ring 008-012-25-2-2 Ring 008-012-25-2-2
45 6430-1609320 Tube
46 6430-1609323 Seal
Link to this page: http://www..php?typeauto=2&mark=11&model=293&group=54

Combined-cycle power plants are those in which the heat of the exhaust gases of the gas turbine is directly or indirectly used to generate electricity in the steam turbine cycle. It differs from steam-powered and gas turbine plants by increased efficiency.

Schematic diagram of a combined cycle plant (from a lecture by Fomina).

GT EG steam

compressor Waste heat boiler K

air EG

feed water

CS - combustion chamber

GT - gas turbine

K - condensing steam turbine

EG - electric generator

Combined-cycle plant consists of two separate units: steam power and gas turbine.

In a gas turbine plant, the turbine is rotated by the gaseous products of fuel combustion. Both natural gas and products of the oil industry (fuel oil, diesel fuel) can serve as fuel. On the same shaft with the turbine is the first generator, which, due to the rotation of the rotor, produces electricity. Passing through the gas turbine, the combustion products give it only a part of their energy and still have a high temperature at the outlet of the gas turbine. From the outlet of the gas turbine, the combustion products enter the steam power plant, into the waste heat boiler, where they heat water and the resulting steam. The temperature of the combustion products is sufficient to bring the steam to the state required for use in a steam turbine (a flue gas temperature of about 500 degrees Celsius makes it possible to obtain superheated steam at a pressure of about 100 atmospheres). The steam turbine drives a second electric generator.

Prospects for the development of CCGT (from Ametistov's textbook).

1. Combined-cycle plant is the most economical engine used to generate electricity. A single-circuit CCGT with a GTP having an initial temperature of about 1000 °C can have an absolute efficiency of about 42%, which will be 63% of the theoretical efficiency of the CCGT. Coefficient useful action A three-circuit CCGT with reheating of steam, in which the temperature of the gases in front of the gas turbine is at the level of 1450 °C, already today reaches 60%, which is 82% of the theoretically possible level. There is no doubt that the efficiency can be increased even more.

2. Combined-cycle plant is the most environmentally friendly engine. First of all, this is due to the high efficiency - after all, all the heat contained in the fuel, which could not be converted into electricity, is released into the environment and its thermal pollution occurs. Therefore, the reduction in thermal emissions from a CCGT compared to a steam power plant will be exactly to the extent that fuel consumption for electricity generation is less.

3. Combined-cycle plant is a very maneuverable engine, which can only be compared in maneuverability by an autonomous gas turbine.

4. With the same capacity of steam-powered and combined-cycle TPPs, the consumption of CCGT cooling water is approximately three times less.

5. CCGT has a moderate cost per installed unit of capacity, which is associated with a smaller volume of the construction part, with the absence of a complex power boiler, expensive chimney, systems for regenerative heating of feed water, using simpler steam turbines and service water systems.

6. CCGT units have a significantly shorter construction cycle. CCGTs, especially single-shaft ones, can be introduced in stages. This simplifies the investment problem.

Combined-cycle plants have practically no drawbacks; rather, we should talk about certain limitations and requirements for equipment and fuel. The installations in question require the use of natural gas. For Russia, where the share of relatively inexpensive gas used for energy exceeds 60% and half of it is used for environmental reasons at thermal power plants, there are all possibilities for the construction of a CCGT.

All this suggests that the construction of CCGT units is the prevailing trend in modern thermal power engineering.

Efficiency of utilization type CCGT:

ηPGU = ηGTU + (1- ηGTU)*ηKU*ηPTU

PTU - steam turbine plant

KU - waste heat boiler

In the general case, the CCGT efficiency:

Here - Qgtu is the amount of heat supplied to the working fluid of the gas turbine;

Qpsu - the amount of heat supplied to the steam medium in the boiler.

1. Principal thermal schemes for the supply of steam and heat from a CHP. Heat supply coefficient α CHP. Ways to cover the peak heat load at CHP,

CHP (combined heat and power plants)- designed for centralized supply of consumers with heat and electricity. Their difference from IES is that they use the heat of the steam exhausted in the turbines for the needs of production, heating, ventilation and hot water supply. Due to this combination of electricity and heat generation, significant fuel savings are achieved in comparison with separate energy supply (electricity generation at IES and heat at local boiler houses). Thanks to this method of combined production, a sufficiently high efficiency is achieved at the CHPP, reaching up to 70%. Therefore, CHP plants have become widespread in areas and cities with high heat consumption. The maximum capacity of a CHPP is less than that of a IES.

CHP plants are tied to consumers, because the radius of heat transfer (steam, hot water) is approximately 15 km. Country CHPPs transmit hot water at a higher initial temperature for a distance of up to 30 km. Steam for production needs with a pressure of 0.8-1.6 MPa can be transferred to a distance of no more than 2-3 km. With an average heat load density, the CHP capacity usually does not exceed 300-500 MW. Only in major cities, such as Moscow or St. Petersburg with a high heat load density, it makes sense to build plants with a capacity of up to 1000-1500 MW.

The capacity of the CHP plant and the type of turbogenerator are chosen according to the heat demand and the parameters of the steam used in the production processes and for heating. Turbines with one and two controlled steam extractions and condensers have received the greatest application (see fig.). Adjustable extractions allow you to regulate the production of heat and electricity.

CHP mode - daily and seasonal - is determined mainly by heat consumption. The station operates most economically if its electric power corresponds to the heat output. At the same time, a minimum amount of steam enters the condensers. In winter, when the demand for heat is maximum, at the estimated air temperature during the hours of operation of industrial enterprises, the load of CHP generators is close to the nominal one. During periods when heat consumption is low, for example, in summer, as well as in winter when the air temperature is higher than the calculated one and at night, the electric power of the CHPP, corresponding to heat consumption, decreases. If the power system needs electrical power, the CHP must switch to mixed mode, which increases the steam supply in part low pressure turbines and condensers. At the same time, the efficiency of the power plant is reduced.

The maximum generation of electricity by cogeneration stations "on heat consumption" is possible only when working together with powerful CPPs and HPPs, which take on a significant part of the load during hours of reduced heat consumption.

comparative analysis of ways to regulate the heat load.

quality regulation.

Advantage: stable hydraulic mode of heating networks.

Flaws:

■ low reliability of sources of peak thermal power;

■ the need to use expensive methods of treatment of make-up water of the heating network when high temperatures coolant;

■ an increased temperature schedule to compensate for the withdrawal of water for hot water supply and the associated reduction in electricity generation for heat consumption;

■ large transport delay (thermal inertia) of regulating the heat load of the heat supply system;

■ high intensity of corrosion of pipelines due to the operation of the heat supply system for most of the heating period with coolant temperatures of 60-85 °C;

■ fluctuations in indoor air temperature due to the influence of the DHW load on the operation of heating systems and the different ratio of DHW and heating loads for subscribers;

■ decrease in the quality of heat supply when the heat carrier temperature is regulated according to the average outdoor air temperature over several hours, which leads to fluctuations in the indoor air temperature;

■ at a variable temperature of network water, the operation of compensators is significantly complicated.

What are the reasons for the introduction of CCGT in Russia, why is this decision difficult but necessary?

Why did they start building a CCGT

The decentralized market for the production of electricity and heat dictates the need for energy companies to increase the competitiveness of their products. The main importance for them is the minimization of investment risk and the real results that can be obtained using this technology.

The abolition of state regulation in the electricity and heat market, which will become a commercial product, will lead to increased competition between their producers. Therefore, in the future, only reliable and highly profitable power plants will be able to provide additional capital investments in the implementation of new projects.

CCGT selection criteria

The choice of one or another type of CCGT depends on many factors. One of the most important criteria in the implementation of the project is its economic viability and safety.

An analysis of the existing market for power plants shows a significant need for inexpensive, reliable in operation and highly efficient power plants. The modular, pre-configured design of this concept makes the plant highly adaptable to any local conditions and specific customer requirements.

Such products satisfy more than 70% of customers. These conditions are largely met by GT and SG-TPPs of the utilization (binary) type.

Energy dead end

An analysis of the Russian energy sector, carried out by a number of academic institutions, shows that even today the Russian electric power industry is practically losing 3-4 GW of its capacities annually. As a result, by 2005, according to RAO "UES of Russia", the volume of equipment that has worked out its physical resource will amount to 38% of the total capacity, and by 2010 this figure will already be 108 million kW (46%).

If events develop exactly according to this scenario, then most of the power units due to aging in the coming years will enter the zone of a serious risk of accidents. The problem of technical re-equipment of all types of existing power plants is exacerbated by the fact that even some of the relatively “young” 500-800 MW power units have exhausted the service life of the main units and require serious restoration work.

Read also: How do GTU and CCGT efficiency differ for domestic and foreign power plants

Reconstruction of power plants is easier and cheaper

Extending the life of plants with the replacement of large components of the main equipment (turbine rotors, heating surfaces of boilers, steam pipelines), of course, is much cheaper than building new power plants.

It is often convenient and profitable for power plants and manufacturing plants to replace equipment with a similar one that is being dismantled. However, this does not take advantage of the opportunities to significantly increase fuel economy, does not reduce pollution environment, modern means of automated systems of new equipment are not used, the costs of operation and repair increase.

Low efficiency of power plants

Russia is gradually entering the European energy market, joining the WTO, but at the same time, we have had an extremely difficult situation for many years. low level thermal efficiency of electric power industry. The average level of efficiency of power plants when operating in the condensing mode is 25%. This means that if the price of fuel rises to the world level, the price of electricity in our country will inevitably become one and a half to two times higher than the world price, which will affect other goods. Therefore, the reconstruction of power units and thermal stations should be carried out in such a way that the new equipment being introduced and individual components of power plants are at the modern world level.

Energy chooses combined cycle technologies

Now, despite the hard financial position, in the design bureaus of power engineering and aircraft engine research institutes, the development of new equipment systems for thermal power plants was resumed. In particular, we are talking about the creation of condensing steam-gas power plants with an efficiency of up to 54-60%.

Economic assessments made by various domestic organizations indicate a real opportunity to reduce the costs of electricity production in Russia if such power plants are built.

Even simple gas turbines will be more efficient in terms of efficiency

At CHPPs, it is not necessary to universally use CCGTs of this type, such as CCGT-325 and CCGT-450. Circuit solutions may be different depending on specific conditions, in particular, on the ratio of thermal and electrical loads.

Read also: Choice of the cycle of the combined cycle plant and the circuit diagram of the CCGT

In the simplest case, when using the heat of gases exhausted in gas turbines for heat supply or production of process steam, the electric efficiency of CHPPs with modern gas turbines will reach a level of 35%, which is also significantly higher than those existing today. About the differences in the efficiency of GTU and PTU - read in the article How the efficiency of GTU and CCGT efficiency differ for domestic and foreign power plants

The use of gas turbines in thermal power plants can be very wide. Currently, about 300 steam turbine units of CHPP with a capacity of 50-120 MW are fed with steam from boilers that burn 90 percent or more of natural gas. In principle, all of them are candidates for technical re-equipment using gas turbines with a unit capacity of 60-150 MW.

Difficulties with the introduction of GTU and CCGT

However, the process of industrial introduction of GTU and CCGT in our country is extremely slow. main reason- investment difficulties associated with the need for sufficiently large financial investments in the shortest possible time.

Another limiting circumstance is related to the actual absence in the range of domestic manufacturers of purely power gas turbines that have been proven in large-scale operation. GTUs of a new generation can be taken as prototypes of such gas turbines.

Binary CCGT without regeneration

Binary CCGTs have a certain advantage, as they are the cheapest and most reliable in operation. The steam part of binary CCGTs is very simple, since steam regeneration is unprofitable and is not used. The temperature of the superheated steam is 20-50 °C lower than the temperature of the exhaust gases in the gas turbine. At present, it has reached the standard level in the energy sector of 535-565 °С. The live steam pressure is chosen so as to provide acceptable humidity in the last stages, the operating conditions and blade sizes of which are approximately the same as in powerful steam turbines.

Influence of steam pressure on the efficiency of CCGT

Of course, economic and cost factors are taken into account, since the steam pressure has little effect on the thermal efficiency of the CCGT. To reduce the temperature difference between the gases and the steam-water medium and in the best way to use the heat of the gases exhausted in the gas turbine with less thermodynamic losses, the evaporation of the feed water is organized at two or three pressure levels. The steam generated at reduced pressures is mixed in at intermediate points of the flow path of the turbine. Steam reheating is also carried out.

Read also: Reliability of CCGT Combined-Cycle Plants

Influence of flue gas temperature on CCGT efficiency

With an increase in the gas temperature at the turbine inlet and outlet, the steam parameters and the efficiency of the steam part of the GTP cycle increase, contributing to the overall increase in the CCGT efficiency.

The choice of specific directions for the creation, improvement and large-scale production of power machines should be decided taking into account not only thermodynamic perfection, but also the investment attractiveness of projects. The investment attractiveness of Russian technical and production projects for potential investors is the most important and the most urgent problem, on the solution of which the revival of the Russian economy largely depends.

(Visited 3 460 times, 1 visits today)

Above we have considered a CCGT of the simplest and most common type - a recycling one. However, the variety of PGUs is so great that it is not possible to consider them in full. Therefore, below we will consider the main types of CCGT, which are interesting for us either from a fundamental or from a practical point of view. At the same time, we will try to classify them, which, like any classification, will be conditional.

According to their purpose, CCGTs are divided into condensing and heating plants. The first of them generate only electricity, the second ones also serve to heat network water in heaters connected to a steam turbine.

According to the number of working bodies used in CCGT, they are divided into binary and mono. In binary plants, the working bodies of the gas turbine cycle (air and fuel combustion products) and the steam turbine plant (water and water vapor) are separated. In monarnye installations, the working fluid of the turbine is a mixture of combustion products and water vapor.

Scheme Monary CCGT shown in fig. 9.4. The output gases of the GTU are sent to the waste heat boiler, into which water is supplied by a feed pump 5 . The resulting steam enters the combustion chamber 2 , mixes with the products of combustion and the resulting homogeneous mixture is sent to the gas (more correctly, to the steam-gas turbine 3 . The meaning of this is clear: part of the air coming from air compressor and serving to reduce the temperature of the working gases to the permissible strength conditions of the gas turbine parts, is replaced by steam, the increase in pressure of which by the feed pump in the state of water consumes less energy than the increase in air pressure in the compressor. At the same time, since the gas-steam mixture leaves the waste heat boiler in the form of steam, the heat of condensation of water vapor received by it in the boiler and which is a significant amount goes into the chimney.

The technical difficulty of organizing the condensation of steam from a gas-vapor mixture and the associated need for constant operation of a powerful water treatment plant is the main disadvantage of a mono-type CCGT.

Rice. 9.4. Principal diagram of a mono CCGT

Abroad, the described monar installation was called STIG (from Steam Iniected Gas Turbine). They are mainly built by General Electric in combination with gas turbines of relatively low power. In table. 9.1 shows data from General Electric, illustrating the increase in engine power and efficiency when using steam injection.

Table 9.1

Changes in power and efficiency when steam is introduced into the combustion chamber of a mono-type CCGT

It can be seen that when steam is injected, both power and efficiency increase.

The shortcomings noted above did not lead to the widespread use of mono-type CCGTs, at least for the purposes of generating electricity at powerful TPPs.

At the Yuzhno-Turbine Plant (Nikolaev, Ukraine) a demonstration mono-type CCGT unit with a capacity of 16 MW was built.

Most CCGTs are of the binary type. Existing binary CCGTs can be divided into five types:

Utilization CCGT. In these units, the heat from the exhaust gases of the gas turbine is utilized in waste heat boilers to produce steam of high parameters used in the steam turbine cycle. The main advantages of utilization CCGTs compared to CCGTs are high efficiency (in the coming years, their efficiency will exceed 60%), significantly lower capital investments, less need for cooling water, low harmful emissions, and high maneuverability. As shown above, utilizing CCGTs require highly economical high temperature gas turbines with high flue gas temperatures to generate high performance steam for a steam turbine plant (STP). Modern gas turbines that meet these requirements can still operate either on natural gas or on light grades of liquid fuel.

CCGT with discharge of gas turbine outlet gases into a power boiler. Often such CCGTs are called briefly "dump", or CCGT with low pressure steam generator(Fig. 9.5).

Rice. 9.5. Scheme of waste CCGT

In them, the heat of the exhaust gases of the GTU, containing a sufficient amount of oxygen, is sent to the power boiler, replacing the air in it supplied by the boiler's draft fans from the atmosphere. At the same time, there is no need for an air heater of the boiler, since the exhaust gases of the gas turbine have a high temperature. The main advantage of the waste circuit is the possibility of using inexpensive energy solid fuels in the steam turbine cycle.

In a waste CCGT, fuel is sent not only to the combustion chamber of the GTP, but also to the power boiler (Fig. 9.5), and the GTP runs on light fuel (gas or diesel fuel), and the power boiler runs on any fuel. In the waste CCGT, two thermodynamic cycles are realized. The heat that enters the combustion chamber of the gas turbine along with the fuel is converted into electricity in the same way as in the utilization CCGT, i.e. with an efficiency of 50%, and the heat supplied to the power boiler - as in a conventional steam turbine cycle, i.e. with an efficiency of 40%. However, a sufficiently high oxygen content in the gas turbine exhaust gases, as well as the need to have a small excess air ratio behind the power boiler, lead to the fact that the share of the steam turbine cycle power is approximately 2/3, and the share of the gas turbine power is 1/3 (in contrast to the utilization CCGT , where this relation is inverse). Therefore, the efficiency of a waste CCGT is approximately

those. significantly less than that of a recycling CCGT. Tentatively, it can be considered that, in comparison with a conventional steam turbine cycle, fuel savings when using a waste CCGT unit are approximately half as much as fuel savings in a utilizing CCGT unit.

In addition, the scheme of a waste CCGT turns out to be very complicated, since it is necessary to ensure autonomous operation of the steam turbine part (in the event of a GTP failure), and since there is no air heater in the boiler (after all, hot gases from the GTP enter the power boiler during CCGT operation), it is necessary to install special heaters that heat the air before supplying it to the power boiler.

Main literature:

Your own abstract;

Fundamentals of modern energy: A course of lectures for managers of energy companies. In two parts. / Under the general editorship of Corr. RAS E.V. Ametistova. ISBN 5-7046-0889-2. Part 1. Modern thermal power engineering / Trukhniy A.D., Makarov A.A., Klimenko V.V. - M.: MPEI Publishing House, 2002. - 368 p., ill. ISBN 5-7046-0890-6 (part 1). Part 2. Modern electric power industry / Ed. professors A.P. Burman and V.A. Stroeva. - M.: MPEI Publishing House, 2003. - 454 p., ill. ISBN 5-7046-0923-6 (part 2)