RU2520762C1 - Combined cycle plant - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: this plant has two working circuits: combined cycle composed by gas turbine plant and steam cycle including heat exchanger-condenser mounted at gas turbine pant inlet channel, heat exchanger-heater mounted at gas turbine plant outlet channel, steam turbine and high-pressure pump, all being loop-backed. Gas turbine plant working medium is the mix of air and steam formed by water evaporation in heat exchanger-condenser. Steam circuit working medium is steam formed by water evaporation in heat exchanger-heater and condensation in heat exchanger-condenser. Water evaporation and fluid condensation in heat exchanger-condenser occur simultaneously.

EFFECT: higher efficiency.

10 cl, 8 dwg

Description

The invention relates to a power system.

The purpose of heat engines is to convert fuel energy into useful work. The ratio of this work to the amount of heat released during the complete combustion of the fuel is called effective efficiency. heat engine η _e .

The aim of the invention is to increase effective efficiency thermal machines (gas turbine units).

In gas turbine units (GTU), energy costs for own needs make up a significant share of the unit's useful work. This fraction decreases with increasing specific enthalpy (heat content) of the working fluid. The heat content of the working fluid increases if water vapor is added to the composition of GTU combustion products.

Known gas-vapor installation (patent RU 2272916 C2, 2006), in which the conversion of water into steam is carried out in a heat exchanger-evaporator located behind the turbine. This allows for the regeneration of the heat of exhaust gases - to increase the effective efficiency. installation. The disadvantage of the installation is the high water consumption and the associated energy losses spent on its heating and vaporization, which does not allow to increase the effective efficiency more than 50%.

A steam-gas installation is known (utility model patent No. 50603, 2006), comprising an input device, a compressor, a combustion chamber, a compressor drive turbine, an output device, a heat exchanger-heater located in the channel of the output device behind the compressor drive turbine, and a heat exchanger-condenser cooled water. These heat exchangers are looped through a steam turbine and a high pressure pump: on one side, the heat exchanger-condenser is connected to the output receiver of the steam turbine, and on the other hand, to the inlet to the high pressure pump; the heat exchanger-heater is connected on one side to the inlet receiver of the steam turbine, and on the other hand, to the outlet of the high pressure pump. A liquid circulating inside the heat exchangers, passing into the steam and vice versa. Effective Efficiency setting ~ 50%.

The essence of the invention lies in the fact that to increase effective efficiency in a combined cycle plant, internal thermodynamic cycles, efficiency are used which in the composition of the heat engine tends to unity (Pismenny VL Internal thermodynamic cycles // Conversion in mechanical engineering, 2006, No. 3. P.5-10).

This goal is achieved by the fact that in a gas turbine containing an input device, a compressor, a combustion chamber, a compressor drive turbine, an output device, a heat exchanger-condenser is located in front of the compressor in the input device channel, and a heat exchanger-heater in the output device channel behind the compressor drive turbine. Heat exchangers are looped through a steam turbine and a high pressure pump: on one side, the heat exchanger-condenser is connected to the output receiver of the steam turbine, and on the other hand, to the inlet to the high pressure pump; the heat exchanger-heater is connected on one side to the inlet receiver of the steam turbine, and on the other hand, to the outlet of the high pressure pump. A fluid circulates inside the looped system, passing into steam and vice versa. Water is supplied to the inlet channel (in front of the heat exchanger-condenser). In this case, the liquid pressure at the inlet to the high-pressure pump is not less than 0.15 MPa, and the temperature of the working fluid at the inlet to the compressor is more than 100 ° C (conditions under which liquid condensation and water evaporation occur simultaneously in the heat exchanger-condenser).

As the fluid circulating in the heat exchangers, it is preferable to use water.

Preferably

the degree of pressure increase in the compressor was more than 18;

the gas temperature in front of the turbine was more than 1700 K;

water consumption was more than 15% of air consumption;

the fluid pressure at the outlet of the high pressure pump was more than 15 MPa;

fuel was supplied to the combustion chamber through a heat exchanger located in the channel connecting the steam turbine to the heat exchanger-condenser;

cryogenic liquid was used as fuel;

hydrogen was used as fuel.

The use of hydrogen as a fuel makes it possible to obtain a new CCGT quality, namely: the heat utilization coefficient (fraction of usable heat) tends to unity (the product of hydrogen combustion is water vapor, which, together with steam formed from water, is used to heat rooms and other purposes )

The disadvantage of CCGT is that the energy of water vaporization is not used to obtain useful work.

The disadvantage is reduced if a heat exchanger-evaporator is installed behind the heat exchanger-heater, which converts the energy of vaporization of water into the energy of steam of an easily evaporating liquid with its subsequent conversion into useful work.

The essence of the invention lies in the fact that the working fluid in the heat exchanger-evaporator is ethyl alcohol or other liquid having a boiling point lower than the boiling point of water at a pressure corresponding to the gas pressure in the channel of the outlet device.

This goal is achieved by the fact that in a gas turbine installation containing an input device, a compressor, a combustion chamber, a compressor drive turbine, an output device, a heat exchanger-condenser is located in front of the compressor in the input device channel, and a heat exchanger-heater in the output device channel behind the compressor drive turbine . Heat exchangers are looped through a steam turbine and a high pressure pump: on one side, the heat exchanger-condenser is connected to the output receiver of the steam turbine, and on the other hand, to the inlet to the high pressure pump; the heat exchanger-heater is connected on one side to the inlet receiver of the steam turbine, and on the other hand, to the outlet of the high pressure pump. A fluid circulates inside the looped system, passing into steam and vice versa. Water is supplied to the inlet channel in front of the heat exchanger-condenser. A heat exchanger-evaporator is installed in the outlet channel behind the heat exchanger-heater, which is looped through the turbine, heat exchanger and pump: the heat exchanger-evaporator is connected on one side to the turbine inlet receiver and, on the other hand, to the pump outlet; the output receiver of the turbine is connected to the inlet to the heat exchanger, the output of which is connected to the inlet to the pump. A volatile liquid circulates inside the ring system, passing into steam and vice versa.

Preferably, the pressure behind the turbine is below atmospheric.

Figure 1 shows a diagram of a combined cycle plant;

figure 2 shows the dependence of effective efficiency η _e from the relative water flow δ and gas temperature in front of the turbine Tg *;

figure 3 shows the dependence of the specific power of the CCGT Ne _beats on the relative water flow δ and the gas temperature in front of the turbine Tg *;

figure 4 shows the thermodynamic cycle of CCGT;

figure 5 shows a diagram of a combined cycle plant;

figure 6 shows the dependence of effective efficiency η _e from the relative water flow δ and gas temperature in front of the turbine Tg *;

Fig. 7 shows the dependences of the specific power of CCGT Ne _beats on the relative water flow δ and the gas temperature in front of the turbine Tg *;

on Fig shows a diagram of the effectiveness of CCGT.

Combined-cycle plant (Fig. 1) consists of an input device 1, a water collector 2, a heat exchanger-condenser 3, a compressor 4, a combustion chamber 5, a compressor drive turbine 6, a heat exchanger-heater 7, an output device 8, a steam turbine 9, and a high pressure pump 10, heat exchanger 11, electric generators 12, pumps n. The heat exchanger-condenser 3 is installed in the channel of the input device 1 in front of the compressor 4. The water collector 2 is installed at the inlet to the heat exchanger-condenser 3. The heat exchanger-heater 7 is installed in the channel of the output device behind the compressor drive turbine 6. Steam turbine 9, heat exchanger-condenser 3, the high pressure pump 10 and the heat exchanger-heater 7 are looped: the heat exchanger-condenser is connected on one side to the output receiver of the steam turbine, and on the other hand, to the inlet to the high pressure pump; the heat exchanger-heater is connected on one side to the inlet receiver of the steam turbine, and on the other hand, to the outlet of the high pressure pump. Inside the ring system, water circulates, passing into steam and vice versa.

The installation is as follows. Air from the atmosphere into channel 1 is mixed with water entering the same channel through manifold 2. In the heat exchanger-condenser, the mixture is heated to 100 ° C or more, as a result of which the water in the mixture turns into dry steam. The vapor-air mixture is compressed in the compressor to a pressure of ~ 2 MPa (pressure is limited by the temperature of the compressor blades) and is supplied to the combustion chamber, and fuel is supplied through the internal channel of the heat exchanger 11 there. The resulting air-fuel mixture (mixed with steam) burns out, as a result of which the gas temperature in front of the turbine rises to 1700 K and more. In the turbine 6, the temperature and pressure of the combustion products are reduced. The pressure approaches atmospheric, and the temperature remains either higher or close to critical for water. The turbine does a useful job. From the turbine 6, the combustion products enter the heat exchanger-heater 7, through the internal channels of which, under the action of the pump 10, water moves. Water (in the heat exchanger 7) as a result of heat exchange with the combustion products turns into superheated steam. The temperature of the combustion products at the outlet of the heat exchanger 7 decreases (~ 140 ° C). Combustion products are removed to the atmosphere.

Superheated steam enters the steam turbine 9. In the turbine, the pressure and temperature of the steam decrease. The turbine does a useful job. The pressure in front of the turbine (behind the high pressure pump) is selected so that the steam at the outlet of the turbine at a pressure of ~ 0.2 MPa is dry (this is ~ 15 MPa). The steam passes through the heat exchanger 11 and enters the heat exchanger-condenser 3. In the heat exchangers 11 and 3, heat is removed from the steam. As a result of heat removal, the steam cools and passes into a liquid state - water. Water is pumped out by the pump 10, which ensures a decrease in pressure in the line behind the turbine 9, as well as a pressure drop across the specified turbine.

Heat transfer in the heat exchanger-condenser 3 occurs due to the temperature difference of the working fluid inside (steam passing into water) and outside (mixture of air and water passing into steam) of the heat exchanger 3. Heat transfer occurs sequentially in three stages. At the first stage, as a result of heat transfer, the vapor temperature decreases ~ to 120 ° C (vapor pressure ~ 0.15 MPa), and the temperature of the mixture increases ~ to 100 ° C (mixture pressure - atmospheric). Upon reaching the indicated temperatures (the second stage), steam condenses with the release of heat and water evaporates with the absorption of the indicated heat (the energy of vaporization is transferred from one working fluid to another). In the third stage (after completion of the condensation and evaporation processes), the condensate temperature decreases (due to heat transfer) and the temperature of the vapor-air mixture increases to values (more than 100 ° C) at which thermal equilibrium sets in. As a result of the described processes, a stationary heat flow is established in the heat exchanger-condenser, the basis of which is the energy of vaporization of water entering the CCGT unit through collector 2.

The useful work done by the combined-cycle plant is converted into electrical energy in electric current generators 12.

Figure 2 and figure 3 shows the dependence of the effective efficiency and specific power Ne _yd (power per kilogram of air consumption) CCP (Fig. 1) on the parameters of the working process: relative water consumption δ (water consumption per kilogram of air consumption) and gas temperature in front of the turbine Tg * with a degree of pressure increase in the compressor πк = 20, which is limited by the strength of the compressor blades. Fuel is kerosene. In calculating the losses, the corresponding efficiency was taken into account. thermodynamic processes: 0.85 - for compression; 0.92 - for expansion; 0.98 - for combustion; 0.99 - mechanical efficiency The calculation was performed for standard conditions: t _n = 15 ° C and P _n = 760 mm Hg It can be seen that η _e for δ = 0.2 reaches 63%, and the specific power is 1200 kW / kg.

Figure 4 shows the thermodynamic cycle of CCGT (figure 1) in TS coordinates. Letters denote the state of the working fluid in characteristic sections of a CCGT unit: n - entrance to the input device; in - entrance to the compressor; to - exit from the compressor; g - entrance to the turbine; t - exit from the turbine; C - exit from the output device (nozzle). The CCGT cycle consists of external L ₁ and internal L ₂ cycles. The internal cycle is a cycle that does not have energy exchange with the external environment (energy is exchanged only with the external cycle), which makes the internal cycle as part of the CCGT unit absolutely efficient (there are no external losses). The inner cycle converts the heat energy of the outer cycle Q _1-2 into work L ₂ and the heat energy Q _2-1 , which is spent on creating the working fluid (vapor-air mixture) of the outer cycle. The steam-air mixture has a higher specific heat than air, which at the same temperatures Tg * allows you to have: a) a higher specific heat content of the working fluid — a smaller fraction of the energy consumed for the auxiliary needs of a CCGT unit, b) a higher work cycle L ₁ - a higher specific power PSU.

The disadvantage of CCGT is that the energy of water vaporization, which is spent on creating the working fluid of the external cycle (the area shaded in gray in Fig. 4), is lost after the cycle is completed.

Figure 5 shows the CCGT, in which the indicated heat loss (vaporization energy) is converted into useful work - heat loss is reduced to the size of the area painted black (figure 4).

CCP (Fig. 5) consists of CCP (Fig. 1), in the output channel 8 of which a heat exchanger-evaporator 13 is installed, which is looped through the turbine 14, heat exchanger 15 and pump 16: the heat exchanger-evaporator is connected on one side to the turbine inlet receiver, on the other hand, with the exit from the pump; the output receiver of the turbine is connected to the inlet to the heat exchanger, the output of which is connected to the inlet to the pump. Ethyl alcohol circulates inside the ringed system, passing into steam and vice versa. The turbine 14 is connected to an electric generator 12.

The installation is as follows. Combustion products, the temperature of which is more than 100 ° C, pass through channel 8 to a heat exchanger-evaporator 13, inside of which ethanol is circulated at a pressure of ~ 0.19 MPa at a temperature of ~ 50 ° C. As a result of heat exchange, the alcohol is heated to a temperature of more than 95 ° C, turning into superheated steam (the boiling point of alcohol is ~ 95 ° C), and the combustion products are cooled to a temperature of less than 95 ° C, at which the water vapor in the combustion products turns into water (between the alcohol and water there is an exchange of vaporization energies). Combustion products (together with water) are removed to the atmosphere.

The superheated steam enters the turbine 14. In the turbine, the pressure and temperature of the steam decrease. The turbine does a useful job. The pressure behind the turbine is below atmospheric (chosen so that the steam at the outlet of the turbine is dry). From the turbine, steam enters the heat exchanger 15. Due to the heat exchange between the steam and cold water circulating inside the heat exchanger 15, the steam condenses (turns into liquid alcohol) and cools (~ 50 ° C). Liquid alcohol is pumped out by a pump 16, which maintains a given pressure drop across the turbine 14.

The useful work done by the turbine is converted into electrical energy in the generator 12.

In Fig.6 and Fig.7 shows the dependence of the effective efficiency and specific power Ne _beats CCP (Fig. 5) on the parameters of the working process: relative water flow δ and gas temperature in front of the turbine Tg * with a degree of increase in pressure in the compressor π _к = 20. Fuel is kerosene. In calculating the losses, the corresponding efficiency was taken into account. thermodynamic processes: 0.85 - for compression; 0.92 - for expansion; 0.98 - for combustion; 0.99 - mechanical efficiency The calculation was performed for standard conditions: t _n = 15 ° C and P _n = 760 mm Hg It is seen that the effective efficiency CCP (Fig. 5) in relation to the basic CCP (Fig. 1) increases by 3 ÷ 4%, and specific power - by 10 ÷ 12%.

The marginal (theoretical) efficiency of the CCGT unit (Fig. 5) depends on the fuel used and can be estimated as

,

,

where α = 1.1 ÷ 1.2 is the coefficient of excess air;

Lo is the stoichiometric coefficient;

Hu is the calorific value of fuel;

δ = 0.2 ÷ 0.3 is the relative flow rate of water;

m = 0.5 ÷ 0.6 is the relative consumption of alcohol;

r = 850 kJ / kg - specific heat of vaporization of alcohol;

c _in = 1.004 kJ / (kg · deg) - specific heat of air;

c _water = 4.18 kJ / (kg · deg) is the specific heat of water.

On Fig shows the limit values of effective efficiency, which can be obtained using the principle of energy conversion, incorporated in the CCGT (figure 5), for fuels: kerosene, methane, hydrogen.

A positive result of the proposed technical solutions is the expansion of opportunities to increase effective efficiency thermal machines (gas turbine units) up to 60–75% or more, which is 10–15% higher than that of the best analogues.

Claims (14)

1. Combined-cycle plant comprising an inlet device, a compressor, a combustion chamber, a compressor drive turbine, an output device, a heat exchanger-heater located in the channel of the output device behind the compressor drive turbine, and a water-cooled heat exchanger-condenser that are looped through the steam turbine and pump high pressure: the heat exchanger-condenser is connected, on the one hand, to the output receiver of the turbine, and, on the other hand, to the inlet to the high-pressure pump; the heat exchanger-heater is connected, on the one hand, to the turbine inlet receiver, and, on the other hand, to the outlet of the high-pressure pump, inside which the liquid circulates, passing into steam and vice versa, characterized in that the heat exchanger-condenser is located in the channel of the inlet device in front of the compressor, and water is supplied to the channel of the input device in front of the heat exchanger-condenser. 2. Combined-cycle plant according to claim 1, characterized in that the temperature of the working fluid at the inlet to the compressor is more than 100 ° C. 3. Combined-cycle plant according to claim 1, characterized in that the liquid is water. 4. Combined-cycle plant according to claim 1, characterized in that the liquid pressure at the inlet to the high-pressure pump is more than 0.15 MPa. 5. Combined cycle plant according to claim 1, characterized in that the degree of pressure increase in the compressor is more than 18. 6. Combined-cycle plant according to claim 1, characterized in that the gas temperature in front of the turbine is more than 1700 K. 5. Combined cycle plant according to claim 1, characterized in that the water flow rate is more than 10% of the air flow rate. 6. Combined cycle plant according to claim 1, characterized in that the liquid pressure at the outlet of the high pressure pump is more than 15 MPa. 7. Combined-cycle plant according to claim 1, characterized in that the fuel is supplied to the combustion chamber through a heat exchanger located in the channel connecting the steam turbine and the heat exchanger-condenser. 8. Combined-cycle plant according to claim 1, characterized in that the fuel is a cryogenic liquid. 9. Combined-cycle plant according to claim 1, characterized in that the fuel is hydrogen. 10. Combined-cycle plant containing an input device, a compressor, a combustion chamber, a compressor drive turbine, an output device, a heat exchanger-condenser located in the channel of the input device in front of the compressor, and a heat exchanger-heater located in the channel of the output device behind the compressor drive turbine, which are looped through a steam turbine and a high pressure pump: on one side, the heat exchanger-condenser is connected to the output receiver of the turbine, and on the other hand, to the inlet to the high pressure pump; the heat exchanger-heater is connected, on the one hand, to the turbine inlet receiver, and, on the other hand, to the outlet of the high-pressure pump, inside which the liquid circulating into steam and vice versa, water is supplied to the channel of the input device in front of the heat exchanger-condenser, characterized in that a heat exchanger-evaporator is installed behind the heat exchanger-heater channel, which is looped through a turbine, heat exchanger and pump: the heat exchanger-evaporator is connected on one side to the turbine inlet receiver On the other hand - to the outlet of the pump; the output receiver of the turbine is connected to the inlet to the heat exchanger, the outlet of which is connected to the inlet to the pump, inside of which an easily evaporating liquid circulates, passing into steam and vice versa. 11. Combined-cycle plant according to claim 10, characterized in that the volatile liquid is ethyl alcohol. 12. Combined cycle plant of claim 10, wherein the pressure behind the turbine is lower than atmospheric.

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