RU2230921C2 - Method of operation and steam-gas plant of power station operating on combination fuel (solid and gaseous or liquid fuel) - Google Patents

Abstract

FIELD: steam-gas turbines; steam gas electric power stations.

SUBSTANCE: proposed method of operation of steam-gas electric power station operating on combination fuel includes combustion of solid fuel with formation of superheated vapor, mixing of combustion products with steam, expansion of gas-steam mixture with conversion of its potential energy into mechanical energy with simultaneous conversion of the latter into electric energy, recovery of exhaust gas heat, condensing of moisture and compression. Steam obtained owing to recovered heat of exhaust gases is connected with steam of steam circuit before mixing with combustion products. Steam-gas plant contains steam circuit and gas-steam circuit. Gas-steam circuit includes waste heat recovery boiler, heat exchanger for preliminary heating of condensate and condenser, condensate cooling unit and topping-up compressor connected by shaft with gas-turbine engine or steam turbine. Steam-gas plant is furnished with steam bleeding unit connected by its input simultaneously to steam extractions of waste heat recovery boiler and intermediate steam superheater of steam generator and by its output to combustion chamber of gas-steam turbine engine. Heat exchanger for preliminary superheating of condensate is connected by its water input through deaerator to condenser output and by its output, to feed pump of steam generator or intermediate heater.

EFFECT: improved efficiency of electric power station.

3 cl, 1 dwg

Description

The invention relates to the field of steam and gas turbine construction, in particular to combined cycle power plants.

The method of operation of a combined cycle organic fuel (solid + gaseous or liquid) combined gas and liquid processes, compression of gaseous or liquid fuels in it, transformation of the potential energy of the resulting combustion products into mechanical work during their expansion, burning in their stream, was adopted as an analogue solid fuel and steam generation, converting its potential energy into mechanical work during expansion with intermediate overheating, water vapor condensation and mixing Recreatives Products of combustion with atmospheric air (see VYRyzhkin Thermal power stations -.. M .: Energia, 1976, 447 pp.)

The known method has the disadvantage that the temperature (thermal potential) of the generated steam is low (about 600 ° C). As a result, the fraction of thermal energy of the steam converted into work is negligible.

As a prototype, a method of operating a combined power plant was adopted, which includes compressing air in a compressor followed by supplying fuel to a combustion chamber of a gas turbine and into a combustion chamber of a combined cycle gas turbine with a secondary zone, expanding the products of fuel combustion in the turbines, followed by cooling in waste heat boilers, additional cooling of the products of combustion of a combined cycle gas turbine with condensation of water vapor, condensate supply to waste heat boilers with its further heating, evaporation and steam separation in separators and steam overheating and mixing of superheated steam with air supplied to the combustion chamber of a combined cycle gas turbine, and part of the water from the separators is introduced into heat and mass exchange into contact with compressed air taken after the compressor with partial evaporation and cooling of the water and with heating of the vapor-air mixture, the latter is additionally heated with heat of the combustion products before cooling them in waste heat boilers and fed into the combustion chamber of a combined cycle gas turbine, and chilled water is mixed with condensate (see SU 1830421 A1, class F 01 K 21/04, 07/30/93, Bull. 28).

As a prototype, a combined-cycle plant including a compressor, a combustion chamber with a gas turbine, and a combustion chamber with a combined-cycle turbine, which is connected by a shaft to the consumer of work, and recovery boilers located in series after the turbines in the direction of the exhaust gas movement, which are connected with a condenser, which is connected with the gas-vapor mixture to the outlet of the recovery boiler of a gas-vapor turbine. A steam-air mixture heater is installed between the steam-gas turbine and its recovery boiler, which is connected to a heat and mass exchanger, in which steam-air mixture is obtained from hot water taken from the drum-separators of the recovery boilers in a stream of air taken after the compressor.

The combustion chamber of a combined cycle gas turbine is connected by pipelines to a steam-air mixture heater and in pairs to waste heat boilers (see SU 1830421 A1, class F 01 K 21/04, 07/30/93, Bul. 28).

The known method has the disadvantage that it cannot use coal and brown coal as fuel.

The invention solves the problem of creating a method of operating a combined cycle power plant using combined fuel (solid with gaseous or liquid).

The problem is solved in that in the method of operation of a combined cycle gas-fired power plant, including the combustion of fuel with the formation of superheated steam, partial expansion of superheated steam with the conversion of its potential energy into kinetic and kinetic into mechanical with its simultaneous conversion into electric with further steam supply after expansion to an intermediate superheat in the steam circuit, and including the processes of air compression, burning fuel in it in the combustion chamber, mixing in the combustion chamber of the obtained combustion products with water vapor, expanding the gas-vapor mixture and utilizing the heat of the exhaust gases in the recovery boiler in the gas-vapor circuit, according to the invention, gas or liquid fuel is burned in the combustion chamber, the heat of the exhaust gases after the recovery boiler is recovered from the production of condensate and the compression of exhaust gases, moreover, the steam supplied to the combustion chamber is obtained by preliminary combining the steam of the gas-vapor circuit, forming as a result of heating the condensate in the recovery boiler, and the steam of the steam circuit after intermediate overheating of the gas-vapor circuit condensate obtained from the preheated exhaust gas heat as a result of burning solid fuel, while expanding the gas-vapor mixture, its potential energy is converted into kinetic and kinetic energy into mechanical with simultaneous conversion of the latter to electrical, while the steam of the steam circuit before intermediate overheating is expanded to pressure that exceeds the pressure in the combustion chamber by 3-4 bar.

The problem is solved in that a gas-vapor installation (power plant) containing a steam circuit, consisting of a coupled steam generator, a steam turbine connected by a shaft to a converter of mechanical energy into electrical energy, and an intermediate steam superheater, a system of regenerative heaters, a feed pump, and a gas-steam circuit, consisting from a gas-turbine engine, including a sequentially located compressor, a combustion chamber with a steam supply and a turbine, and sequentially located on the move In accordance with the invention, the gas-steam circuit is additionally equipped with successively arranged condensate preheater heat exchanger, a condenser and a booster compressor in communication with the atmosphere and a coupled shaft with a gas-steam turbine connected by a shaft to a mechanical converter energy into an electric, or steam turbine, capacitor is connected to the input through a deaerator through its water outlet two of the recovery boiler and at the same time its output and input through water is connected respectively to the input and output of the condensate cooling unit, and the combined cycle plant is additionally equipped with a steam collection unit, which is connected simultaneously with its outputs to the steam exits of the recovery boiler and the intermediate steam heater of the steam generator and its an outlet to the combustion chamber of a gas-turbine engine, and the condensate preheater is connected by its inlet through the water through a deaerator to the outlet of the condenser, and by its outlet m through the feed pump and the system of regenerative heaters to the steam generator.

A new set of essential features is absent in the known technical solutions and allows to obtain the following advantages:

- significantly increases the temperature potential of steam obtained due to the thermal energy of solid fuel and thereby significantly (almost 2 times) increases its work, which significantly increases the thermodynamic efficiency of the power plant;

- provides a significant (approximately two-fold) reduction in harmful emissions into the environment;

- significantly reduces the size, weight and cost of a kilowatt of installed capacity of a power plant.

All these advantages are aimed at increasing production efficiency and reducing the cost of electric energy.

The drawing shows a thermal diagram of a combined cycle plant that implements the proposed method.

Combined-cycle plant consists of two circuits of steam and gas-steam. The steam circuit includes a steam generator 1, a steam turbine 2, which is connected by a shaft with a mechanical energy to electric energy converter 3 (electric generator), an intermediate steam superheater 4, a system of regenerative water heaters 5 and a feed pump 6. The gas-steam circuit includes a gas-turbine engine 7 with sequentially arranged compressor 8, the combustion chamber 9 and the turbine 10 and successively disposed by the movement of the exhaust gases, the boiler utilizer 11, the condensate preheater 12, the absorber 13 and the booster compressor 14, which is connected to the atmosphere by its output and is connected to a gas-steam turbine engine 7 or a steam turbine 2. The gas-steam turbine engine 7 is connected by a shaft to a mechanical energy to electric energy converter 15. The condenser 13 is connected to the input of the waste heat boiler 11 through its water outlet through a deaerator (not shown in the drawing) and is simultaneously connected to the input and output of the condensate cooling unit 16 by its output and water inlet. The combined-cycle plant is additionally equipped with a steam collecting unit 17, which is connected simultaneously with its inputs to the steam exits of the recovery boiler 11 and the steam intermediate heater 4 of the steam generator, and the condensate preheater 12 is connected via its water inlet through the deaerator to the condenser 13 inlet, and its output through the feed pump 6 and into the system of regenerative heaters 5 to the steam generator 1.

The method is carried out by a combined-cycle plant as follows. The condensate preheated in the heat exchanger 12 and the system of regenerative heaters 5 is fed by a feed pump 6 to the steam generator 1, where it is evaporated, and the resulting steam is overheated and sent to the steam turbine 2, where it is partially expanded to a pressure that exceeds the pressure in the combustion chamber 9 of the gas-turbine engine 7 by 3-4 bars, while converting part of the potential energy of the vapor into kinetic, and kinetic energy into mechanical, which is simultaneously converted in electric generator 3 into electric. After the turbine 2 pairs are sent to the superheater 4 of the steam generator 1 for intermediate overheating due to the heat of solid fuel. At the same time, air is supplied through the compressor 8 of the gas-turbine engine 7 to the combustion chamber 9, where gas or liquid fuel is directed and burned. The resulting combustion products are mixed in the combustion chamber 9 with the steam supplied from the steam collection unit 17. Moreover, part of the steam is fed into the primary zone of the combustion chamber (combustion zone) to suppress nitrogen oxides and is therefore called environmental steam. The vapor-gas mixture obtained in the combustion chamber 9 is sent to the turbine 10, where it is expanded, converting its potential energy into kinetic energy, which is then converted into mechanical energy, and the obtained mechanical energy is simultaneously converted into electrical energy in the electric generator 15. The gas-vapor mixture used in turbine 10 ( exhaust gases) are sent to a waste heat boiler 11, where its heat is utilized to form water vapor, which is supplied to the steam collection unit 17 and mixed there with the steam supplied there from the intermediate steam of the superheater 4 of the steam generator 1, from where the resulting steam mixture is sent to the combustion chamber 9. The exhaust gases cooled in the recovery boiler 11 are sent to the condensate preheater 12, where their heat is utilized with transferring it to the condensate, which is fed through the feed pump 6 and the regenerative heater system 5 sent to the steam generator 1. After the heat exchanger 12, the pre-cooled exhaust gases are fed to the condenser 13, where they are cooled and water vapor is condensed upon contact with the condensate, cooled m at node 16 condensate cooling. The condensate supplied and received in the condenser 13 is divided into two streams: one is sent through the deaerator simultaneously to the inputs of the utilizer boiler 11 and the condensate preheater 12, and the second to the condensate cooling unit 16, and the cooled and dried exhaust gases are sent to the booster compressor 14, where they are squeezed to atmospheric pressure, and discharged into the environment.

Compared with the prototype, the proposed method of operation of a combined cycle plant provides the power plant with combined (solid with gaseous or liquid) fuel. Compared with the analogue, the proposed method of operation of a combined cycle fossil-fired power plant can significantly increase its efficiency, i.e. thermodynamic efficiency. This is due to the fact that the fraction of heat converted into work, supplied to the working fluid, clearly depends on its temperature.

L = Q (1-T _o / T _t ),

where L is the work (the fraction of heat converted into work);

Q is the heat supplied to the working fluid;

T _about , T _t - absolute temperatures, respectively, of the environment and the working fluid at the entrance to the turbine.

The dependence is seen that at constant temperature environment That the more heat is converted into work, the higher the T _m, the working fluid temperature at the turbine inlet. In the considered analogue and other known analogs, T _m does not exceed 873 K and no growth prospects are expected. Therefore, the theoretical amount of heat converted into work does not exceed 67%. In the proposed method, when using modern combined-cycle plants T _t = 1523 K, which increases the proportion of heat converted into work up to 81%. With a further new increase in T _{t, the} proportion of heat converted into work will increase further. In addition, at the same time, the specific power of the power plant will increase by about 1.7–2 times, which significantly reduces capital investments, and therefore reduces the cost of a kilowatt of installed capacity. This is confirmed by the dependence below, from which it follows that the power of the combined cycle plant increases in proportion to the increase in the temperature of the working fluid at the turbine inlet.

N _T = GС _r T _t (1-1 / P $\genfrac{}{}{0ex}{}{\text{k-k1 / k}}{\text{t}}$ ) η _t

where G is the flow rate of the working fluid;

With _p is the isobaric heat capacity of the working fluid;

T _t - gas temperature at the entrance to the turbine;

P _t - the degree of expansion of the working fluid in the turbine;

η _t - adiabatic efficiency of the turbine;

N _t - power on the turbine shaft.

At the same time, emissions of harmful substances into the atmosphere are reduced by more than 2 times per unit of work performed.

The table shows the comparative data of a technical training college with a discharge of the exhaust gases of a gas turbine into the furnace of a steam generator (analogue) and the proposed combined-cycle plant

From the above data it follows that the proposed method of operation of a combined cycle gas turbine power plant not only provides operation on combined fuel, but significantly increases its thermodynamic efficiency (increase in efficiency) and at the same time significantly increases specific power, which significantly reduces the cost of a kilowatt of installed capacity of the power plant.

Claims (3)

1. The method of operation of a combined cycle gas-fired power plant, including the combustion of fuel with the formation of superheated steam, partial expansion of superheated steam with the conversion of its potential energy into kinetic, and kinetic energy into mechanical energy with its simultaneous conversion into electrical energy with further steam supply after expansion to intermediate overheating in the steam circuit and including processes of air compression, burning fuel in it in the combustion chamber, mixing in the chamber combustion of the obtained combustion products with water vapor, expansion of the gas-vapor mixture and utilization of the heat of the exhaust gases in the recovery boiler in the gas-vapor circuit, characterized in that gas or liquid fuel is burned in the combustion chamber, the heat of the exhaust gases after the recovery boiler is recovered to produce condensate and booster exhaust gases, moreover, water vapor supplied to the combustion chamber is obtained by preliminary combining the steam of the gas-vapor circuit formed as a result of heating condensate in the recovery boiler and steam of the steam circuit after intermediate overheating obtained from the condensate of the gas-steam circuit preheated by the heat of the exhaust gases as a result of burning solid fuel, while expanding the gas-vapor mixture, its potential energy is converted into kinetic energy and kinetic energy into mechanical energy simultaneous conversion of the latter into electrical. 2. The method of operation of a combined cycle power plant according to claim 1, characterized in that the steam of the steam circuit before intermediate overheating is expanded to a pressure that exceeds the pressure in the combustion chamber by 3-4 bars. 3. Combined-cycle plant (power plant), comprising a steam circuit, consisting of a coupled steam generator, a steam turbine connected by a shaft with a mechanical energy to electric converter, and an intermediate steam superheater, a system of regenerative heaters, a feed pump, and a gas-steam circuit, consisting of a gas-turbine engine, comprising a sequentially located compressor, a combustion chamber with steam supply and a turbine and a recovery boiler located in series along the movement of exhaust gases OR, characterized in that the gas-steam circuit is additionally equipped with successively arranged exhaust gas after the recovery boiler condensate preheater, a condenser and a booster compressor, connected by its output to the atmosphere and connected shaft with a gas-turbine engine, connected by a shaft with a mechanical energy to electrical energy converter or steam turbine, the condenser is connected to the input of the recovery boiler through its water outlet through a deaerator and simultaneously a water outlet and water inlet are connected respectively to the inlet and outlet of the condensate cooling unit, and the gas-vapor unit is additionally equipped with a steam collection unit, which is connected simultaneously with its outputs to the steam exits of the recovery boiler and the intermediate steam superheater of the steam generator and its output to the combustion chamber of the gas-turbine engine , and the condensate preheater heat exchanger is connected by its water inlet through the deaerator to the condenser outlet, and by its output through the feed pump and the system egenerativnyh heaters to the steam generator.