RU2031214C1 - Method of optimization of operating steam-gas power plant - Google Patents

Abstract

FIELD: heat power engineering. SUBSTANCE: flow rate of stem, which is fed to the combustion chamber at nominal regime of operation, is determined by relationships available in the invention description. The relationships allow for nominal air flow rate, amount of air needed for full burning out of 1 kg of fuel, extent of air pressure raising at compression, temperature of steam-gas mixture at the beginning of expansion, and set of empirical coefficients. At peak regime of operation, flow rates of fuel and steam are increased in agreement with the available relationships. Additionally generated steam-gas mixture operates in the turbine of peak power. EFFECT: simplified method. 1 dwg

Description

 The invention relates to combined combined cycle power plants (cycles), and more specifically to methods of operating combined-cycle power plants with steam injection into a gas stream in front of a turbine.

 A known method of operation of a combined combined cycle plant with the discharge of gases after a gas turbine into a steam boiler [1], according to which the products of fuel combustion after expansion in a gas turbine are cooled in a regenerator - steam boiler with the formation of superheated steam, which is sent to a steam turbine. The peculiarity of this combined combined cycle plant is that various working fluids work in it without mixing: in gas-turbine air and fuel combustion products, in steam-turbine water and water vapor. In this method, the heat of the exhaust gases can be used quite fully, which makes it possible to obtain high efficiency of the entire combined installation.

 However, the implementation of this method leads to the need to create a complex system with a steam turbine and a complex of steam cycle equipment, which increases the cost of construction and maintenance of the installation. In addition, such an installation cannot work with power above the nominal.

 There is also a method of organizing the operation of a combined cycle plant [2], which includes compressing air in a compressor, supplying compressed air and fuel to a combustion chamber with the formation of a combustible mixture, supplying a steam-water body (water or water vapor) after the regenerator to the high pressure path before or after the combustion chamber burning a combustible mixture in the presence of a steam-water body with the formation of a gas-vapor mixture, expanding the latter in a turbine with work and cooling the expanded gas-vapor mixture with transferring part of the heat to water and steam y going to the injection into the gas stream in front of the turbine.

 The injection of water (steam) causes a significant increase in the power of the gas turbine unit (GTU), but is accompanied by a decrease in the temperature of the gas flow in front of the turbine. In the specified technical solution, the injection of water (steam) is of a short-term nature and is used as a means to improve the maneuverability of the installation, which is provided primarily by increasing the throttle response and improving starting. When starting up the unit using water injection, the time to increase the load from idle to nominal can be reduced to 30-35% or less. In the future, as the gas temperature rises, the water flow should gradually decrease and turn off. Such dynamic characteristics of gas turbine engines with injection allow us to consider them as an emergency reserve and as a means to improve the dynamics of network load regulation. However, in this case, steam injection does not provide an increase in efficiency in the nominal mode and does not contribute to a long-term increase in the capacity of gas turbines over the nominal.

 The invention is aimed at solving the problem of optimizing the operation of a combined-cycle plant with steam injection, providing a high efficiency of the installation, as well as a long-term increase in power with sufficient simplicity and speed of selection of the main parameters.

, кг/с
(1)
D_н= B_н

кг/с, (2) где В_н и D_н - соответственно расходы топлива и пара в номинальном режиме работы установки, кг/с;
V_н - номинальный расход воздуха, обеспечиваемый компрессором установки, м³/с;
V_о - теоретически необходимое количество воздуха для полного сжигания 1 кг топлива при нормальных условиях, м³/кг;
ε - степень повышения давления воздуха при его сжатии в компрессоре;
а₁,а₂,b₁,b₂ - эмпирические коэффициенты;
τ - условия относительная температура парогазовой смеси в начале расширения, причем последнюю определяют по математическому выражению

, где t - значение в ^оС номинальной температуры парогазовой смеси в начале расширения, а эмпирические коэффициенты выбирают из значений а₁=17,2... 18,4; а₂= 4,6...5,2; b₁=12,9...13,9; b₂=3,7...4,2, при этом в пиковом режиме работы увеличивают расходы топлива и пара в камеру сгорания по соответствующим математическим зависимостям
B_н<B≅β₁

, кг/с (3)
D_н<D≅ β₂B кг/с, (4) где В и D - соответственно расходы топлива и пара в пиковом режиме работы установки, кг/с;
β ₁,β ₂ - эмпирические коэффициенты, причем последние выбирают из соответствующих значений β₁ =0,90...0,97;β₂ =10...13, при этом дополнительно полученную в пиковом режиме парогазовую смесь срабатывают в пиковой турбине.The problem is achieved by the fact that by a method of optimizing the operation of a combined-cycle plant with steam injection, which includes compressing air in a compressor, supplying compressed air and fuel to the combustion chamber with the formation of a combustible mixture, supplying superheated water vapor to the combustion chamber combustion zone, burning the combustible mixture in the presence of superheated steam with the formation of a gas-vapor mixture, expansion of the latter in the turbine with the completion of work, and cooling of the expanded gas-vapor mixture with the transfer of part of the heat to the feed water for the images overheated steam, moreover, the supply of fuel and steam to the combustion chamber is carried out with certain costs, according to the invention in the nominal operating mode, the fuel and steam consumption to the combustion chamber is determined by mathematical dependencies
B _n =

kg / s
(1)
D _n = B _n

kg / s, (2) where B _n and D _n are respectively the fuel and steam consumption in the nominal operating mode of the installation, kg / s;
V _n - nominal air flow provided by the compressor of the installation, m ³ / s;
V _about - theoretically necessary amount of air for complete combustion of 1 kg of fuel under normal conditions, m ³ / kg;
ε is the degree of increase in air pressure during its compression in the compressor;
a ₁ , a ₂ , b ₁ , b ₂ are empirical coefficients;
τ - conditions the relative temperature of the vapor-gas mixture at the beginning of expansion, the latter being determined by mathematical expression

Where t - value ^C nominal temperature gas mixture at the beginning of expansion, the empirical coefficients are selected from the values of a = ₁ 17.2 ... 18.4; a ₂ = 4.6 ... 5.2; b ₁ = 12.9 ... 13.9; b ₂ = 3.7 ... 4.2, while in peak operation, fuel and steam consumption in the combustion chamber is increased according to the corresponding mathematical dependencies
B _n <B≅β ₁

kg / s (3)
D _n <D≅ β ₂ B kg / s, (4) where B and D are the fuel and steam consumption in peak operation mode of the installation, kg / s, respectively;
β ₁ , β ₂ are empirical coefficients, the latter being selected from the corresponding values β ₁ = 0.90 ... 0.97; β ₂ = 10 ... 13, while the steam-gas mixture additionally obtained in peak mode is activated in a peak turbine .

The essence of the invention lies in the fact that as a result of mathematical modeling and research, the conditions are obtained for the optimal nominal operating mode of a combined-cycle plant with steam injection, i.e. mode in which the highest efficiency is achieved for the given basic parameters. Such conditions are fuel consumption V _n and steam consumption D _n determined by dependencies (1) and (2). In peak mode, the conditions for the long-term maximum power of the installation at a nominal air flow rate were identified. Such conditions are the maximum fuel consumption and maximum steam consumption, determined by dependencies (3) and (4). The additionally formed steam-gas mixture stream is separated in peak mode and directed to additional work.

 The drawing shows a schematic diagram of a combined-cycle plant with steam injection, which implements the proposed method for optimizing the operation of the installation.

 A steam-gas installation with steam injection includes a compressor 1, a combustion chamber 2, in which fuel T is burned and combustion products are mixed with water vapor d, a main turbine 3 mechanically connected to a compressor 1 and an electric generator 4, a steam generator 5 using the heat of the exhaust gases ( UG), a pump 6 for supplying water to a steam generator 5, a tank 7 of desalted feed water, a regulating device 8 for supplying a gas-vapor mixture for additional work, a peak power turbine 9, an electric generator 10, regeneration ator 11 HS heat turbine 9 after peak power, valves 12 and 13 to connect the regenerator 11.

 The combined-cycle plant works as follows.

 Atmospheric air B is compressed by compressor 1 and fed into the combustion zone of chamber 2, where fuel T is also supplied and superheated water vapor is injected d. As a result of combustion of the combustible mixture thus formed in the presence of superheated water vapor, a vapor-gas mixture flows at a temperature t, which is sent to the main turbine 3. The control device 8 is in the closed position and does not pass the gas-vapor mixture into the turbine 9.

In the main turbine 3, the thermal energy of the vapor-gas mixture during its expansion is partially converted into mechanical work, which is spent on the drive of the compressor 1 and the electric generator 4. The gas-vapor mixture with a temperature t ₁ after the turbine 3 enters the steam generator 5 of superheated water vapor, where the mixture is cooled to a temperature t ₂ and then removed in the form of HC in the atmosphere. Water w is fed into the desalted feed water tank 7, from which feed water is pumped to the steam generator 5 by pump 6 and then to the injection into the combustion zone of the chamber 2.

Given the basic parameters of the working process — the temperature t in front of the main turbine and the degree of increase in air pressure ε — the optimal mode is established with strictly defined values of the coefficient of excess air and the specific supply of injected steam. To fulfill these conditions, by means of regulating devices (not shown in the diagram), the nominal fuel supply V _n and steam D _{n are set} according to dependences (1) and (2), at which the highest plant efficiency is obtained at the nominal operating mode of compressor 1. Thus, the nominal operating mode of the entire combined cycle plant, which is characterized by the highest efficiency.

 In order to obtain a plant power that is more than nominal at a nominal operating mode of compressor 1, the fuel consumption B and the flow rate of injected steam D are set according to dependences (3) and (4), moreover, the additionally formed part of the flow is separated from the steam-gas mixture stream by means of a control device 8 and directed it to a peak power turbine 9 leading the electric generator 10. After the turbine 9, the spent steam-gas mixture can be used for heat consumers by means of a regenerator 11, and for the formation of steam supplied to the injection, or removed directly into the atmosphere.

 The proposed method of optimizing the operation of a combined-cycle plant with steam injection allows creating conditions for working with the highest possible efficiency at the nominal installation mode for the adopted main parameters and exceeding the efficiency of gas turbines according to conventional schemes by 4..8%. The proposed method also provides a solution to the problem of long-term peak power, which can exceed the rated power by a maximum of 2 ... 3 times.

Claims (1)

METHOD FOR OPTIMIZING THE WORK OF A STEAM-GAS PLANT, including compressing air in a compressor, supplying compressed air and fuel to a combustion chamber with the formation of a combustible mixture, supplying superheated steam to the combustion zone of a combustion chamber, burning a combustible mixture in the presence of superheated steam to form a vapor-gas mixture, expanding it into a turbine with the completion of work and cooling of the expanded vapor-gas mixture with the transfer of part of the heat to the feed water for the formation of superheated steam, and the supply of fuel and steam to the chamber burning out lead to certain expenditure, characterized in that the nominal consumption mode B _n D _n and p in the combustion chamber is determined by the mathematical relationships

where V _n - nominal air flow provided by the compressor of the installation, m ³ / s;
V _about - theoretically necessary amount of air for complete combustion of 1 kg of fuel under normal conditions, m ³ / kg;
ε is the degree of increase in air pressure during its compression in the compressor;
a ₁ = 17.2-18.4; a ₂ = 4.6-5.2; b ₁ = 12.9-13.9; b ₂ = 3.7-4.2 - empirical coefficients;
τ is the relative relative temperature of the vapor-gas mixture at the beginning of expansion, the latter being determined by mathematical expression

where t is the value of the nominal temperature of the gas mixture at the beginning of expansion, ^o C,
while in peak operation, fuel consumption B and steam D increase in the combustion chamber according to the corresponding mathematical dependencies

D _n <D≅ β ₂ B,
where β ₁ = 0.90-0.97;
β ₂ = 10-13,
- empirical coefficients,
while the steam-gas mixture additionally obtained in peak mode is activated in a peak turbine.

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