RU2084644C1 - Method of enhancing efficiency of steam-gas plant - Google Patents

Abstract

FIELD: power engineering. SUBSTANCE: method comprises heating water in the economizer of the boiler when afterburning degree is higher than optimal one for a given parameters of steam. The flow rate of heated water is equal to its optimal flow rate when the afterburning degree is an optimal. The remainder portion of water is heated in air cooler up to a temperature that is not as low as the boiling temperature. The flows are then mixed in the drum of the boiler. EFFECT: simplified method. 2 cl, 2 dwg

Description

 The claimed invention relates to energy, in particular to the generation of electric energy in combined cycle plants with afterburning.

Known methods of generating electric energy in combined cycle gas turbine units (CCGT) of the utilization type, consisting in using the heat of the exhaust gases of a gas turbine unit (GTU) to obtain additional electric energy in a steam turbine adjustment [1] 2 There is a method of increasing the power of a steam turbine adjustment, which consists in TU exhaust gases, an additional fuel combustion is carried out in front of the boiler [2]
The well-known CCGT with afterburning, selected as a prototype, contains a gas turbine unit consisting of low and high pressure compressors with an intermediate air cooler between them, a combustion chamber, a gas turbine, a boiler, and a steam turbine [3]. The disadvantage of this method and installation is that afterburning leads to a decrease in the efficiency of CCGT units, and when afterburning the maximum possible amount of fuel (waste CCGTs), the efficiency of the CCP decreases by 8 10% compared to the efficiency of the cogeneration plant of the utilization type. Such a decrease in efficiency in CCGT with afterburning is due to the fact that afterburning leads to an increase in the consumption of steam produced in the boiler, and therefore to an increase in the flow rate of feed water through the economizer, which leads to an increase in the temperature head at the “hot” end of the economizer and, as a result, to reduce the efficiency of heat use in the installation.

 The invention is aimed at increasing the efficiency of using heat in combined cycle plants, and as a result, increasing the efficiency of combined cycle gas turbine with afterburning compared to the efficiency of combined cycle gas turbine utilization.

 The technical result is ensured by the fact that in combined cycle plants with afterburning and an intermediate gas cooler with a degree of afterburning, expressed in relation to the amount of heat supplied in the afterburner of the gas turbine boiler to the amount of heat supplied in the combustion chamber, it is higher than the optimal value for the steam parameters (pressure, temperature), with which the steam turbine installation works, feed water is supplied to the economizer of the gas boiler in an amount equal to its flow rate with the optimum degree of afterburning. The remaining part of the feed water is sent to the GTU air cooler, in which it is heated to boiling point. At the same time, it is necessary to supply such a quantity of heat in the gas turbine cooler that it is possible to fulfill the inequality condition.

где i₀, i_k энтальпия пара в начале и в конце расширения в паровой турбине;
i_во энтальпия пароводяной среды за воздухоохладителем ГТУ;
η $\genfrac{}{}{0ex}{}{\text{en}}{\text{пгу}}$ коэффициент полезного действия ПГУ утилизационного типа.

where i ₀ , i _{k the} enthalpy of steam at the beginning and at the end of expansion in a steam turbine;
i _the enthalpy of the steam-water medium behind the GTU air cooler;
η $\genfrac{}{}{0ex}{}{\text{en}}{\text{pgu}}$ the efficiency of the CCGT utilization type.

 At lower initial parameters of the steam of the turbine adjustment in the air cooler, not only is the feed water heated to a temperature not lower than the boiling point, but also its partial evaporation.

 Then in the boiler drum there is a mixture of feed water flows, then the total flow passes through the evaporative and overheating surfaces of the boiler and enters the steam turbine.

после чего в барабане котла происходит смешение этих потоков, позволяющее обеспечить КПД ПГУ с дожиганием выше КПД ПГУ утилизационного типа.Fulfillment of the listed conditions, which are distinguishing features, namely: the direction in the economizer of the boiler for these parameters of steam (pressure, temperature) at a degree of afterburning above the optimum amount of feed water equal to its amount at an optimal degree of afterburning, heating the remaining part of the feed water behind the gas turbine cooler to a temperature not lower than boiling point under the conditions of inequality

after which, in the boiler drum, these flows are mixed, which allows ensuring the efficiency of the CCGT unit with afterburning higher than the efficiency of the CCGT of utilization type.

 In FIG. 1 shows a thermal diagram of a combined cycle gas turbine unit with afterburning and an intermediate gas cooler. In FIG. Figure 2 shows the curves of the processes of expansion of steam in a steam turbine in the i-s diagram for various initial parameters.

 The thermal circuit consists of a gas turbine unit, which includes a low-pressure compressor 1, an air cooler 2 with a heating surface for feed water 12, a high-pressure compressor 3, a combustion chamber 4, a gas turbine 5, an afterburner 6, a waste heat boiler 7 with a steam superheater 8, an evaporator 9, an economizer 10, and a drum 11, a steam turbine 13, a condenser 14, a feed pump 15 and electric generators 16, a chimney 17, valve 18.

 Installation works as follows. Air from the atmosphere is compressed in a low-pressure compressor 1, cooled in an air cooler 2, compressed again in a high-pressure compressor 3 in a combustion chamber 4, fuel is burned, and then hot gases expand in a gas turbine 5, the exhaust gases of a gas turbine enter the afterburner 6, in which additional fuel combustion occurs. After that, the gases enter the waste heat boiler 7, where they pass the steam superheater 8, the evaporator 9 and the economizer 10 in series, giving up their heat and are released into the atmosphere through the chimney 17. The steam from the waste heat boiler 7 enters the steam turbine 13, condenses into the condenser 14 and the feed pump 15 is directed to the valve 18, in which the flow is divided into two parts, the first part, which is equal in value to the steam flow rate in the steam turbine tuning with the optimal degree of afterburning for these steam parameters, is sent to economy jerez 10, and the other part is sent to the heating surface of the feed water 12 of the air cooler 2, where it is heated to parameters allowing the condition of formula (1) to be fulfilled, but not lower than the boiling temperature for a given pressure of FIG. 2 curve 1, and if necessary for lower parameters and its partial evaporation of FIG. 2 curve 2. The mixing of flows occurs in the drum 11, after which the entire flow passes through the evaporator 9 and superheater 8 and enters the steam turbine 13.

 Using the proposed method for generating electric energy in combined cycle gas turbine with afterburning makes it possible to increase the efficiency by 2–3% compared with the efficiency of a CCGT utilization type with a degree of afterburning higher than optimal.

Claims (2)

1. A method of increasing the efficiency of a gas-vapor plant with afterburning and an intermediate air cooler of a gas turbine installation, which consists in heating after a steam turbine installation of one part of the feed water in the economizer of the gas-vapor installation, its other part in the air cooler of the gas turbine installation, characterized in that for these parameters of steam (pressure, temperature ) in the economizer of the boiler with a degree of afterburning above the optimum, feed water enters in an amount equal to its optimal flow rate with an optimal degree of after burning, heating the remaining part of the feed water is carried out in the air cooler of the gas turbine unit to a temperature not lower than the boiling point, provided that the inequality

after which there is a mixture of flows in the drum of the boiler of a combined cycle plant. 2. The method according to claim 1, characterized in that to fulfill the conditions of inequality

at lower steam parameters in the air cooler of the gas turbine installation, not only is the feed water heated to boiling point, but also its partial evaporation,
where i ₀ , i _{k the} enthalpy of steam at the beginning and at the end of expansion in a steam turbine;
i _{in the} enthalpy _{of the} steam-air cooler environment for a gas turbine plant;
η $\genfrac{}{}{0ex}{}{\text{en}}{\text{pgu}}$ - Efficiency of a combined cycle gas recovery plant.

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