Method for operation of combined cycle plant with gas-water and gas-steam heaters

Abstract

FIELD: energy.SUBSTANCE: invention is intended for use in thermal energy in combined-cycle plants with gas-water and gas-steam heaters. During peak electrical load hours, the exhaust gases from the gas turbine are directed to a gas-steam superheater, where steam generated in a gas-water evaporator is supplied. Superheated steam is directed into the medium pressure cylinder of the steam turbine, which allows for the generation of additional electrical energy. After the gas-water evaporator, the exhaust gases enter the gas-water feedwater heater, and then the gas-water main condensate heater. This allows for the displacement of regeneration and, as a result, the generation of additional electrical energy. During off-peak hours of electrical load at night, the steam turbine is unloaded by the release of electrical energy and, if necessary, is switched to motor mode with ventilation steam passage into the condenser. Superheated steam from the gas-steam superheater in motor mode enters the front seal chamber of the high-pressure cylinder and through a high-speed reduction-cooling unit into the extraction chamber of the low-pressure cylinder of the steam turbine for its cooling, which eliminates the need to consume steam from adjacent boilers for this purpose. The regeneration system is displaced by exhaust gases similar to the operating mode of a turbo unit during peak hours. Downstream of the main condensate gas-water heater, the exhaust gases are directed to the mains water gas-water heater, which allows for the generation of additional heat, which will be accumulated by heating networks and buildings.EFFECT: expansion of the control range with the generation of additional electric power during peak hours of electric load and switching the turbine to the motor mode during hours of decreased electric consumption with the accumulation of thermal energy by heating networks and buildings during night off-peak hours of electric load in the power system.1 cl, 1 dwg

Description

[0001] The level of technology to which the technical solution relates

[0002] The invention relates to the field of energy and is intended for use in thermal energy at combined cycle gas turbines (CCGT) with gas-water and gas-steam heaters.

[0003] Technical field

[0004] A combined cycle gas turbine unit for a double-circuit nuclear power plant is known (see Russian Federation Patent No. 2547828, published April 10, 2015), comprising a steam turbine fed with steam from the main steam generator, with high-pressure and low-pressure cylinders interconnected by a steam pipeline with a separator-superheater included therein, a gas turbine and a waste heat recovery steam generator generating steam connected along the heating side to the exhaust gas tract of the gas turbine, characterized in that additional heating of the feedwater is carried out in a steam-water heater connected after the high-pressure feedwater heater, with an intermediate steam coolant supplied from the waste heat recovery steam generator through a heating steam pipeline, while condensate is fed through a main condensate collection pipeline to the waste heat recovery steam generator, in which heating and evaporation occurs incoming condensate with the formation of steam.

[0005] The disadvantage of this technical solution is the low efficiency of heat recovery from gases leaving the gas turbine.

[0006] A method is known for increasing the maneuverability and safety of a nuclear power plant (see Russian Federation Patent No. 2604208, published on 10.12.2016) comprising a steam turbine with high-pressure (HP) and low-pressure (LP) cylinders, high-pressure (HP) and low-pressure (LP) heaters, two steam distribution devices, a separator, an intermediate superheater, wherein the HP inlet is connected by a pipeline to the first steam distribution device, the LPC inlet is connected by a pipeline to the second steam distribution device, an additional steam turbine unit (STU), a high-speed pressure reducing unit (HPR), wherein the additional STU is connected to the first (via the HPR) and second steam distribution device before the HPC and LPC of the main turbine, respectively, by means of pipelines, a compressor, a combustion chamber, a gas turbine unit (GTU), a waste heat boiler (WHB), wherein the WHB is connected to the feedwater path before and after the HPC by means of pipelines, characterized in thatthat in normal operation, part of the feedwater is sent after the feedwater pump to the boiler unit, where it is heated by the exhaust gases exhausted in the gas turbine generating additional electricity, and is sent to the steam generator (SG), while the flow rate of feedwater through the HPH is reduced, as a result of which the consumption of extractions from the main turbine unit is reduced and an excess amount of steam appears, which after the HPH is sent to an additional steam turbine unit, which also works to generate additional electricity, while in emergency situations accompanied by a power outage, the additional steam turbine unit continues to generate electricity for the NPP's own needs, using the steam obtained in the SG due to the energy of the residual heat release of the reactor; in the event of a failure of the steam turbine unit, electricity supply for the own needs is carried out through the gas turbine unit.

[0007] The disadvantage of this technical solution is the low efficiency of heat recovery from gases leaving the gas turbine.

[0008] The closest in technical essence to the proposed invention is the operation of a combined cycle gas turbine unit during the period of passing the dips in the power consumption schedule (see Russian Federation Patent No. 2757468, published on 10 / 18 / 2021) with regulation of electric power in the cogeneration mode and the use of a gas turbine, a waste heat boiler, a multi-cylinder steam turbine, a condenser, a generator, monitoring and control means as part of the combined cycle gas turbine unit with unloading the power of the gas turbine to the lower limit of the control range and transferring the steam turbine to the motor mode with steam extraction for cooling the flow path, characterized in that when transferring the steam turbine to the motor mode, high-pressure steam is extracted for the network water heater, for the steam inlet of the high-pressure cylinder through the bypass line of the main steam valve, for sealing the high-pressure cylinder through a pressure-reducing and cooling device,and low-pressure steam to the low-pressure cylinder from the network water heater, after passing the minimum load of the power consumption schedule dips, in parallel with the increase in load on the gas turbine, in the advanced mode, they monitor the temperature state of the flow section of the steam turbine and, in accordance with the readings obtained, send into it the amount of high-pressure steam required for rapid increase in load from the waste heat boiler, the temperature of which is maintained above the temperature of the metal of the steam inlet organs by 0-30°C.

[0009] The disadvantages of this technical solution are the consumption of part of the superheated steam for heating water in network heaters, low maneuverability of the steam turbine and the combined cycle plant as a whole, and low efficiency of heat recovery of gases leaving the gas turbine.

[0010] Disclosure of the essence of the invention

[0011] The objective of the invention is to increase the maneuverability of a combined cycle power plant by increasing the supply of electrical energy during peak power consumption and reducing the load on electrical energy supply when the steam turbine is switched to motor mode.

[0012] The technical result is an expansion of the control range with the generation of additional electric power during peak hours of electric load and the transfer of the turbine to the motor mode during hours of decreased electric consumption with the accumulation of thermal energy by heating networks and buildings during night off-peak hours of electric load in the power system.

[0013] The said technical result is achieved due to the fact that in the method of operating a combined cycle plant with gas-water and gas-steam heat exchangers, which consists in regulating the electric power in the cogeneration mode using a combined cycle plant of the following composition: a steam boiler1, high2, medium3 and low4pressure cylinders, an electric generator5, a condenser6, a condensate pump7, low-pressure heaters8, 9, 10, 11, a deaerator12, a feed pump13, high-pressure heaters14, 15, 16, drainage pumps17, network pumps28, network heaters23,24, a peak hot water boiler26, a compressor29, a combustion chamber30, a gas turbine31.To expand the output range of the power plant, the heat from the gas turbine's exhaust gases is utilized in a gas-steam superheater21, a gas-water evaporator20, a gas-water feedwater heater19, and a gas-water main condensate heater18, displacing the regeneration system and thereby increasing power generation. The heat from the gas turbine's exhaust gases is then used in a gas-water system water heater25. Thus, the steam turbine CHP plant is converted into a combined-cycle CHP plant, and the accumulation of thermal energy by heating networks and buildings increases the efficiency of exhaust gas heat recovery from the combined-cycle plant.

[0014] Brief description of drawings

[0015] The essence of the invention is explained in Fig. 1, which shows a thermal schematic diagram of a combined cycle plant operating in accordance with the proposed method.

[0016] In accordance with the proposed method, the combined cycle plant comprises:

[0017] 1 – steam boiler;

[0018] 2, 3, 4 – high, medium and low pressure cylinders;

[0019] 5 – electric generator;

[0020] 6 – capacitor;

[0021] 7 – condensation pump;

[0022] 8, 9, 10, 11 – low pressure heaters;

[0023] 12 – deaerator;

[0024] 13 – feed pump;

[0025] 14, 15, 16 – high pressure heaters;

[0026] 17 – drainage pumps;

[0027] 18 – gas-water heater of the main condensate;

[0028] 19 – gas-water feed water heater;

[0029] 20 – gas-water evaporator;

[0030] 21 – gas-steam superheater;

[0031] 22 – high-speed pressure reducing and cooling unit;

[0032] 23, 24 – network heaters;

[0033] 25 – gas-water heater for network water;

[0034] 26 – Peak hot water boiler;

[0035] 27 – consumer;

[0036] 28 – network pump;

[0037] 29 – compressor;

[0038] 30 – combustion chamber;

[0039] 31 – gas turbine.

[0040] Implementation of the invention

[0041] The combined cycle gas turbine unit includes a steam boiler1, which generates steam that enters the high2, medium3, and low pressure cylinders4, thereby generating electricity in the electric generator5. The condensed steam in the condenser6 is directed by the condensate pump (CP)7 to the low pressure heaters8,9,10,11 (LPH-7, LPH-6, LPH-5, and LPH-4, respectively). Next, the main condensate is directed to the deaerator12, and the feedwater is directed by the feed pump (FP)13 to the high pressure heaters14,15,16 (LPH-3, LPH-2, and LPH-1, respectively). The drained steam from the heaters9 and 10 is directed by the drain pumps17 to the main condensate tract. Network water is directed by a network pump28 to network heaters23 and 24 (SP1 and SP2, respectively), and then to the peak-heating boiler26 and supplied to the consumer27. A compressor29 supplies air to the combustion chamber30 of the gas turbine31.

[0042] The operation of the combined cycle power plant during peak hours of energy consumption in the power system in peak load mode with an increase in the load of the steam turbine and during off-peak night hours in unloading mode with the transfer of the steam turbine to motor mode and the accumulation of heat by heating networks and buildings is carried out as follows.

[0043] During peak electrical load hours, the exhaust gases from the gas turbine unit31 are directed to the gas-steam superheater (GSS)21, which receives steam generated in the gas-water evaporator (GWI)20. The superheated steam is sent to the intermediate-pressure cylinder of the steam turbine3, which allows for the generation of additional electrical energy. After the gas-water evaporator, the exhaust gases enter the gas-water feedwater heater (GVPH)19, and then the gas-water main condensate heater (GVOK)18. This allows for the displacement of regeneration, thereby also generating additional electrical energy. During off-peak electrical load hours at night, the steam turbine is unloaded based on electrical power output and, if necessary, is switched to motor mode with ventilation steam bypass to the condenser6.Superheated steam from the gas-steam superheater, operating in motor mode, enters the high-pressure cylinder's front seal chamber2 and, through a high-speed pressure-reducing and cooling unit22, enters the steam turbine's intermediate-pressure cylinder extraction chamber for cooling, eliminating the need to consume steam from adjacent boilers. The regeneration system is displaced by exhaust gases, similar to the turbine unit's peak-hour operation. After the main condensate gas-water heater, exhaust gases are directed to the network water gas-water heater25, generating additional heat that will be accumulated by heating networks and buildings, thereby reducing the capacity of network heaters during peak electrical demand hours and increasing electrical energy production.

[0044] Example of specific implementation

[0045] The invention can be implemented on the T-100 / 120-130-3 steam turbine unit, which operates with the following steam parameters: the pressure of fresh steam entering the steam turbine head is 12.75 MPa at a temperature of 555°C; the steam pressure in the deaerator is 0.6 MPa; the steam pressure in the condenser is 0.0053 MPa. The gas parameters in the gas turbine unit: the air temperature behind the compressor at nominal mode is 295.8°C, at reduced mode - 212.6°C; the gas temperature in front of the turbine at nominal mode is 1040.9°C, at reduced mode - 551.8°C; the gas temperature behind the turbine at nominal mode is 532.1°C, at reduced mode - 283.9°C.The parameters of gas-water and gas-steam heaters are as follows: temperature of exhaust gases after the gas-water heater - 444.85°C, in reduced mode - 212.6°C; steam temperature before the gas-water heater - 239.6°C, after the gas-water heater - 370.8°C; temperature of gases after the gas-water heater - 376.6°C; temperature of feedwater before the gas-water heater - 229°C; steam temperature after the gas-water heater - 239.6°C; temperature of gases after the gas-water heater - 482.2°C; temperature of feedwater after the fire extinguishing unit - 160.8°C; temperature of feedwater at the boiler inlet - 239.6°C; temperature of gases after the gas-water heater - 382.8°C; temperature of the main condensate after the boiler house - 160.8°C; temperature of gases after the gas-water heater - 150.2°C; temperature of network water before the gas-water heater - 50°C; the temperature of the network water for the hot water supply is 100°C.

[0046] The technical result is an expansion of the control range with the generation of additional electric power during peak hours of electric load and the transfer of the turbine to the motor mode during hours of decreased electric consumption with the accumulation of thermal energy by heating networks and buildings during night off-peak hours of electric load in the power system.

Claims

A method of operating a combined-cycle plant with gas-water and gas-steam heaters, which consists of regulating the electric power in the cogeneration mode using a gas turbine, a multi-cylinder steam turbine, a condenser, a generator, monitoring and control means as part of the combined-cycle plant, in unloading the power of the gas turbine to the lower limit of the control range and transferring the steam turbine to the motor mode, characterized in that during night off-peak hours of the electric load, steam for cooling the flow path and for the seals of the high-pressure cylinder is generated in a gas-water evaporator and superheated in a gas-steam superheater, the main condensate and feedwater are heated in a gas-water heater of the main condensate and a gas-water heater of the feedwater, respectively, the network water is heated in a gas-water heater of the network water, which makes it possible to generate an additional amount of heat,which will be accumulated by heating networks and buildings; during the peak period of the electricity consumption schedule, steam after generation in the gas-water evaporator and superheating in the gas-steam superheater enters the input of the medium-pressure cylinder, which makes it possible to generate additional electricity, the main condensate and feedwater are heated in the gas-water heater of the main condensate and the gas-water heater of the feedwater, respectively, displacing regenerative heating, which makes it possible to generate additional electricity, the network water is heated in network heaters with reduced consumption of bleed steam due to the use of heat from exhaust gases in the gas-water heater and the heat that was accumulated by the heating networks and buildings during night off-peak hours, which also makes it possible to generate additional electricity.

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