SE510115C2 - Power plant and method for regulating its effect - Google Patents

Abstract

A gas turbine (15,21,26) is driven with the combustion gases. The plant also includes an after-burner arrangement (8,23) for increasing the temperature in the combustion gases to that suitable for the gas turbine. A conduit (9) feeds a combustible gas to the after burner and at least one generator (16) is driven by the gas turbine for production of electrical effect. DESCRIPTION OF DRAWING - The figure shows schematically the complete power plant complex. After-burner (8,23), gas feed conduit (9), gas turbine (15,21,26), electrical effect regulating device (37).

Description

20 25 30 35 510115 2 facility under favorable conditions from an environmental and economic point of view.

A problem with the PFBC technology is the difficulty of achieving rapid regulation of the output power. Due to the large gas volume that the plant encloses, the many components that are included as active parts in the plant, and the properties of the fuel, it takes a long time to change pressure and temperature during a load change.

Another limiting factor of the PFBC technology, which has prevented the achievement of a really high efficiency, is that the upper temperature limit, at which combustion of, for example, carbon takes place in a fluidized bed, usually amounts to about 850 to 950 ° C depending on the carbon quality. tet. At high temperatures, the bed mass sinter, which prevents further fluidization. This means that the propellant gas for the gas turbine included in the PFBC power plant has a temperature that is approximately equal to the temperature in the fluidized bed. Since the turbine power increases sharply with increasing temperature of the propellant gas, it is desirable to have a higher gas temperature, up to 1200 to 1500 ° C in order for the power output from the plant's gas turbine section to reach an optimal level. To remedy this weakness, it has been proposed to raise the temperature of the combustion gases leaving the PFBC combustion chamber and to supply the gas turbine with the aid of an afterburning chamber in which a fuel is combusted.

Power plants with a gas turbine to generate mechanical energy are traditionally regulated by controlling the combustion, ie controlling the supply of fuel to the beds. Gas turbines can quickly change the output power but are often expensive to operate because they require exclusive fuels, such as gas and oil. PFBC plants, where it is known to regulate combustion by adjusting the height of the fluidized bed, have the disadvantage that they react slowly to changes in power demand. However, they are cheap to operate.

Furthermore, in connection with such an initially specified PFBC power plant, which has a high-pressure turbine and a low-pressure turbine, it is known from SE-B-469 039 to regulate the plant by influencing the gas flow to the low-pressure turbine by means of a rotatable guide ring ring at the inlet to the same. With such a control, the speed of the low-pressure compressor can be adjusted and in this way the flow of combustion air to the combustion chamber is controlled. However, when a load rise from partial load operation is desired, an adjustment of the guide rail ring, in such a way that the flow through the plant increases, will initially result in a decrease in power since a larger part of the available power is then taken out in the low pressure turbine. .

WO 97/21916 discloses a power plant with an afterburning chamber and a reheat combustion chamber for raising the temperature of the combustion gases before these are supplied to a high-pressure turbine and an intermediate pressure turbine, respectively. Combustible gas is generated in a gasification reactor and can be temporarily stored in a storage tank before it is fed to any of the afterburning devices. This document also shows the possibility of temporarily supplying combustible gas to one of the afterburners in order to achieve a rapid increase in power at the plant.

WO 97/21914 discloses a similar power plant and relates to the control of a booster compressor for adjusting the air flow to the gasification reactor. With the known booster compressor, the pressure in the gasification reactor can be increased quickly, which leads to a greater flow of combustible gases to the afterburning chamber and the reheat combustion chamber. This results in a more intensive combustion in these chambers and the temperature of the combustion gases can be increased rapidly, which enables higher power to be extracted from the plant. By reducing the flow by means of the speed control or the guide rail device, the pressure in the gasification reactor can be quickly reduced and thus the plant can be quickly adapted to a lower power requirement in a corresponding manner.

SUMMARY OF THE INVENTION The object of the present invention is to eliminate the above-mentioned problems and more particularly to create possibilities for a continuous regulation which is fast and compliant.

This object is achieved with the initially stated power plant which is characterized by a control device which is arranged to regulate in a substantially continuous manner the electrical power produced by said generator by controlling the supply of combustible gas to the afterburning device. With such a control device, it is possible in essentially every operating situation to achieve a rapid adaptation of the plant's power to the power requested from an electricity network. By increasing the supply of combustible gas to the afterburner, the temperature of the combustion gases can be raised almost instantaneously, which immediately means that the power produced by the gas turbine rises. In this case, said conduit means may comprise a valve device which is arranged to be set by means of the control device for said control of the supply of combustible gas to the afterburning device.

According to an embodiment of the invention, the control of said supply of combustible gas can be realized in that the control device comprises a power sensing means, which is arranged to sense the electric power produced by said generator for producing a power sensing device arranged in 510115. to form a first control signal which takes into account an effector value, a first regulator, which is the effect setpoint and said effect value and with which the valve device is adjustable. In this case, the control device can be arranged to form said power setpoint, taking into account the load of the system.

According to a further embodiment of the invention, which is arranged to sense the temperature of the combustion control device comprises a temperature sensing means, the sensing gases in the area of the gas turbine device inlet for producing a temperature value, and a second regulator which is arranged to form a second control signal. which takes into account a temperature setpoint and said temperature value and with which the valve device is adjustable.

In this case, the control device can advantageously comprise a selector means which is arranged to select the smallest of the first and second control signal for controlling said supply of combustible gas to the afterburning device.

According to a further embodiment of the invention, the control device comprises a first calculation unit which is arranged to form a setpoint for the height of the fluidized bed by supplying the power setpoint for controlling the height of the bed. In this way, the bed height can be quickly adapted to the system's required power.

According to a further embodiment of the invention, the power plant comprises a compressor device driven by the gas turbine device which is arranged to supply a flow of an oxygen-containing gas to the combustion chamber, the control device comprising a second calculation unit which is arranged to form a setpoint for said flow by supplying the power setpoint for controlling said flow.

In this way, the gas flow to the combustion chamber and through the 10 15 20 25 30 35 U1 ... A 0115 power plant can also be quickly adapted to the plant's required demand.

According to a further embodiment of the invention, the power plant comprises a gasification device which is arranged to produce said combustible gas and a line means which is arranged to supply oxygen-containing gas to the gasification device, the control device being arranged to control the supply of oxygen-containing gas with regard to to the supply of combustible gas to the afterburner. Advantageously, the control device is arranged to control the supply of oxygen-containing gas to the gasification device in such a way that a pressure drop of a certain is obtained. With a pressure drop, the control of the supply of calorific value over the valve device is facilitated. such a bare gas because it provides a good predictability of the relationship between the degree of opening of the valve device and the flow.

The above-mentioned object is also achieved with the initially stated method which is characterized in that the electric power produced by said generator is regulated in a substantially continuous manner by means of a control device by controlling the supply of combustible gas to the afterburning device.

Advantageous embodiments of the method are set out in the dependent claims 12 - 18.

BRIEF DESCRIPTION OF THE DRAWINGS Various embodiments, by way of example, of which the invention will now be explained, will be further illustrated by the accompanying drawings, in which Fig. 1 schematically shows a PFBC power plant with a combined gas and vapor cycle and Fig. 2 schematically shows the construction of a part of a control device of the plant in Fig. 1.

DETAILED DESCRIPTION OF DIFFERENT EMBODIMENTS A PFBC power plant, i.e. a particulate fuel combustion plant in a pressurized fluidized bed, Fig. 1 housed in a pressure vessel 2, may have a volume of the order of 104m3. 1, and which can (abs). in the example shown air, is pressurized to, for example, about 16 bar Compressed oxygen-containing gas, is supplied to the pressure vessel 2 for pressurizing the combustion chamber 1 and for fluidizing a bed 3 in the combustion chamber 1. The compressed air is supplied to the combustion chamber 1 from the pressure vessel 2 via schematic The fluidization nozzles 4 smn are arranged at the bottom of the combustion chamber 1 for fluidizing the bed 3 enclosed in the combustion chamber 1. The bed 3 consists of bed material, granular absorbent and a particulate preferably crushed carbon which is combusted at the height of the bed 3 and to bed-made manner, Bed material can be sucked up j. the container 5 fuel, to the bed 3 the fluidizing air fed. material container 5 on per se US-4,530,207. from the bed 3 via a discharge line and is fed into the bed - for example the 3 from the container 5 via a feed line which opens into the bed 3 at the same height as the discharge line. The discharge is achieved by opening a valve 5 'of a connection to the atmosphere. The supply is effected by opening a valve 5 "of a line extending from the pressure vessel 2 to the supply line, whereby the bed material will be fed into the bed 3 by means of ejector action. The combustion gases from the bed 3 are then fed via a treatment plant 6, which in the example consists of a high-temperature filter, which may be of the ceramic type and which is intended for high temperatures, and an intercept valve 7 further to an afterburning device in the form of an afterburning chamber 8. To the afterburner 8 is also fed a combustible gas via a line 9 from a gasification reactor 10 via a further high-temperature filter 11. The gasification reactor 10 is independent, ie arranged separately from the combustion chamber 1 and outside the pressure vessel 2. The flow of combustible gas to the afterburning chamber 8 is regulated by means of the control valve 12. In the afterburner 8, the combustible gases are burned in connection with the supply of compressed air from a high-pressure compressor or 13 with the aid of a combustion burner for the supply of air following a non-increase in the temperature of the gases. the combustion chamber 8 can be regulated by means of a control valve 14. The gases leaving the afterburning chamber 8 have a temperature of about 1200 - 1500 ° C, which makes them well suited as propellant for driving a first gas turbine 15 in the form of a high pressure turbine. Through the afterburning chamber 8, the temperature of said combustion gases has thus been raised from about 850 - 950 ° C to 1200 - 1500 ° C.

The high-pressure turbine 15 and the high-pressure compressor 13 are arranged approximately on the same axis as a generator 16, from which useful electrical energy can be extracted. The high pressure compressor 13 also delivers compressed air to the PFBC combustion chamber 1 via line 17. An intercept valve 18 is arranged between the high pressure compressor 13 and the combustion chamber 1. The high pressure compressor 13 also delivers air via line 19 to the gasification reactor 10. The residual fuel formed in the gasification reactor 10 at the combustible gas generating bed 3 in the combustion chamber 1. via a fuel line 20 can be supplied.

The PFBC power plant shown in the figure is of an advanced type and has an additional gas turbine 21, in the form of an intermediate pressure turbine, which is arranged on the same shaft 22 as the high-pressure turbine 15 and the high-pressure compressor 13. The expansion and temperature in the high-pressure turbine 15 The reduced gas is led to a further afterburning device 23 which comprises a so-called reheat combustion chamber or reheating combustion chamber. The reheat combustion chamber 23 receives a flow of said combustible gases, which is regulated by means of the control valve 24 and originates from the gasification reactor 10, flow of compressed air from the high-pressure compressor 13, which is regulated by means of a control valve 25. The combustible gases are combusted in the heat burner chamber 23 by means of a burner (not shown) and the hot gases thus formed are mixed with the combustion gases from the high-pressure turbine 15 to raise their temperature again before passing them on via a line to On it take the medium pressure turbine 21 drawn power is significantly increased. the medium-pressure turbine 21. the combustion gases expanded from the low-pressure turbine 21 can be fed to a low-pressure turbine 26. The combustion gases leaving the low-pressure turbine 26 still contain energy which can be utilized in an economizer 27. The low-pressure turbine 26 is arranged on a second shaft 28 on which also a low-pressure compressor 29 is arranged. The low-pressure compressor The low-pressure compressor 29 is thus driven by the low-pressure turbine 26. The air 29 is supplied with atmospheric air via a filter 30. and supplies from its outlet the high-pressure compressor 13 with air which has been compressed in a first stage. The inlet of the low-pressure turbine 26 is provided with a flow regulating 31 with guide vanes with which the speed of the second shaft 28 can be varied in a controllable manner in the form of a guide rail ring. Between the low-pressure compressor 29 and the high-pressure compressor 13, an intercooler 32 is arranged to lower the temperature of the air supplied to the inlet of the high-pressure compressor 13.

Furthermore, the power plant has a steam circuit 33 which is shown schematically and which comprises a steam turbine for driving a generator for generating electric power and a tube arrangement 34 which is arranged in the fluidized bed 3 and is overheated by heat exchange between the tubes. and bed material in which water is circulated, evaporated and the material for absorbing heat generated during the combustion carried out in the bed 13.

The line 19 coming from the high-pressure compressor 13 for supplying compressed air to the gasification reactor 10 comprises a compressor device 35, which in the example shown consists of a so-called booster compressor and which is driven by an electric drive motor 36. By means of the booster compressor 35, the gas pressure of the air supplied to the gasification reactor 10 is further increased, as it is desirable that the gas flow which the gasification reactor 10 supplies to and / or the reheat combustion chamber 23 arriving the flow of pre has a higher pressure than the afterburning chamber 8 combustion gas. Thereby, the combustible gases in any given pressure situation can easily be supplied to the afterburning chamber 8 and / or the reheat combustion chamber 23. In the gasification reactor 10 a liquid or solid fuel is gasified, in this example as in a subchiometric process of Om coal By generating known particles in this particular coal combustible gases. used, the gasification can take place in whole or in part. a stand-alone gasification reactor 10, operating at a higher pressure than the PFBC bed 3, a pressure drop is obtained across the control valves 12 and 24, which enables efficient control of the fuel flow and an even distribution of the fuel flow in these combustion chambers 8, 23. Thus, at a possible pressure of 16 bar in the PFBC combustion chamber 1, a pressure of about 18-30 bar can be achieved in the gasification reactor 10.

The system further comprises a control device 37 for continuous control of the electrical power produced by the plant generator 16. The control device 37 is then connected to the two control valves 12 and 24 10 15 20 25 30 35 11 510115 for controlling the supply of combustible gas to the afterburner chamber 8 and the reheat combustion chamber 23, respectively, to the drive motor 36 of the booster compressor 35, to the guide rail ring 31 for controlling the flow to the low pressure turbine 26 and and the height of the 5 "bed 3. The control device 37 is also connected to the valves 5 'for controlling the fluidized to a variety of sensing means for sensing various parameters that facilitate the regulation of the installation.

These sensing means comprise a power sensing means 38 which is arranged to sense the electric power produced by the generator 16, a first temperature sensing means 39 which is arranged to sense the temperature of the combustion gases in the area of the inlet of the high pressure turbine 15, a second temperature sensing means 40 which is in corrected to sense the temperature of the combustion gases in the area of the inlet of the intermediate pressure turbine 21, a sensing means 41 which is arranged to sense the current height of the fluidized bed 3, a sensing means 42 which is arranged to sense a parameter of the flow of the combustion gas. bare gas to the afterburning chamber 8 and a sensing means 43 which is arranged to sense a parameter of the flow of combustible gas to the reheat chamber 23. It should be noted that only a selection of the sensing means has been specified here and to control device 37 is connected. There are also many limiting parameters that must be taken into account when regulating the system, the vessel 2, the pressure ratio between inlet and outlet of the compressors such as the pressure in the pressure temperature in the intercooler 32 air outlets, 13 and 29, the temperature of the fluidized bed 3, etc.

Fig. 2 schematically shows the construction of a part of a control device of the plant in Fig. 1. By means of the power sensing means 38 a power value is obtained ea by sensing the electric power produced by the generator 16. A power setpoint eb is formed with regard to 10 15 20 25 30 35 51Û 115 12 12 to the instantaneous load of the system, ie the power required from the mains to which the system is connected. The difference between the power setpoint eb and the power value ea is applied to a first controller 44, which is arranged to comprise a PI controller and which is to form a first control signal.

Correspondingly, a temperature value ten is obtained for the temperature of the combustion gases by sensing the temperature at the inlet of the high-pressure turbine 15 and the medium-pressure turbine 21, respectively. A corresponding temperature setpoint tm is formed and the difference between the temperature setpoint tm and the temperature setpoint tm is applied to a second controller 45, which may also include a PI controller and which is arranged to form a second control signal.

The control signals thus formed are supplied to a selector means 46 which comprises a so-called min-selector and which is arranged to select the smallest of the first and second control signal as a control control signal. With the selected control signal, the degree of opening of the control valves 12 and 24 is adjusted, ie the supply of combustible gas to the afterburning chamber 8 and to the reheat combustion chamber 23, respectively. To further improve the coordination between the obtained control signals, it is also possible to use so-called tracking, ie the non-regulating control signal is adjusted by means of a separate circuit (not shown) in such a way that it is always slightly higher, for example 2%, than the regulating control signal. In this way, a faster takeover is obtained when the min selector 46 transitions from one control signal to the other.

In order for the bed 3 to be fed to the requested power, the height of the fluidized power setpoint eb is quickly coupled to a third regulator 47 for controlling the valves 5 'and 5 "which regulate the input of the bed material container 5 and discharge of bed material to and from the bed 3. This feed is obtained by means of a calculation unit 48 which comprises a lead-layer function, in which the gain called i.e. a reinforcing unit 49, can vary and which can be constituted by such a function generator, and a derivative unit SO.

In addition, in order to quickly adapt the supply of air to the combustion chamber 1 to the requested power, the power setpoint eb is also fed to a fourth regulator 51 for controlling the guide rail ring 31 with which the gas flow through the plant. can be regulated. This feedback is obtained by means of a further calculation unit 52 which also comprises a lead-lag function, i.e. a amplifying unit 53, can be constituted by a so-called function generator, and a de- in which the amplification can vary and which tearing unit 54 .

The control device 37 further comprises a fifth regulator 55 which is arranged to form a control signal for controlling the speed of the drive motor 36 of the booster compressor 35 in order thus to provide a control of the supply of air to the gasification device 10. With the sensing means 42, 43 an actual value is obtained. for a parameter of the flow of combustible gas, for example the pressure upstream and downstream of the control valves 12 and 24, ie the pressure drop across these valves. Because the booster compressor is controlled in such a way that these pressure drops, at least during stationary operation, always amount to a certain value, the control of the supply of combustible gas to the afterburning chamber 8 and the reheat combustion chamber 23, respectively, is facilitated.

It is also possible, as an alternative or complement to the speed control, to arrange a guide rail device, for example in the form of controllable guide vanes on a guide rail ring by means of an actuator, in or in front of the booster compressor 35 to regulate the size of the air flow through the same and thus the amount of air supplied to the gasification reactor 10. The actuator is then connected to the control device 37. (not vi- The power plant further comprises devices said) for supplying fuel to the combustion chamber 1 and the gasification device 10. In this case, the control device 37 is advantageously also arranged to control the fuel supply to the gasification reactor 10 taking into account the supply of combustible gas to the afterburning chamber 8 and the reheat combustion chamber 23, respectively.

The invention is in no way limited to the embodiment described above, but a number of possibilities for modifications thereof are possible within the scope of the following claims and should be obvious to a person skilled in the art, without this departing from the basic idea of the invention. For example, the invention is also applicable to a plant which has only two gas turbines, ie that the intermediate pressure turbine 26 is dispensed.

Claims (18)

10 15 20 25 30 35 15 510115 A power plant comprising combustible material in a pressurized fluidized bed (3) from a combustion chamber arranged to burn a hot combustion gas formation, (15, 21, 26), is driven by said combustion gases, 23), the temperature of said combustion gases to a temperature suitable for a gas and gas turbine device arranged at an afterburning device (8, which is arranged to raise the turbine device (15, 21, 26), (9), combustible gas to the afterburning device (8, 23) a conduit means son1 is arranged to supply a combustion therein for effecting said temperature rise, and at least one generator (16), which is arranged to be driven by the gas turbine device (15, 21) to produce electric power, a control device (37 substantially continuously the electrical power which (16) supplies the supply of combustible gas to the afterburning device (8, 23), which is arranged to regulate on a produced by said generator by controlling characteristics. nad_ay that said (12, 24) as (37) for said control of the supply of combustible gas to 23). Plant according to claim 1, conduit means comprising a valve device arranged to be set by means of the control device the afterburning device (8, 3. A plant according to claim 2, characterized in that the control device comprises (38), which is arranged to sense the electrical power produced by said generator (16) (ea), a power sensing means for generating an power value. 51Û 115 16 (44), which is arranged to form a first control signal which takes into account a power supply first regulator and said power value and with which (12, 24) value (eb) (ea) the valve device is adjustable. Plant according to claim 3, characterized in that the control (37), taking into account the demand device of the plant, is arranged to form said power (eb) power. value Ba "includes a Plant according to any one of claims 2 to 4, characterized in that the control device (37) (39, 40), which is arranged to sense the temperature of the combustion gases in the region of gas (15, 21) (tm), (45) , second control signal which takes into account a temperature set (tib) (tia) ken valve device is adjustable. temperature sensing means, the inlet of the turbine device for generating a temperature value and a second regulator which is arranged to form a value and said temperature value and with resting (l2, 24) A plant according to claims 3 and 5, characterized in that (37) (46) is arranged to select the smallest of the first and second control devices comprising a selector means as the control signal for said setting of the valve device (12, 24). Plant according to any one of the preceding claims, known; It is noted that the control device (37) comprises a (48) which is arranged to form a setpoint for the height of the fluidized bed (3) by first calculating unit feeding the power setpoint (eb) for controlling the height of the bed (3). Plant according to any one of the preceding claims, known; According to one of the gas turbine device (15, 21) driven 10 (25, 29) which is arranged to supply a flow of an oxygen-containing gas to the combustion chamber (1) compressor device and that the control device (37) comprises a second calculation (52) said flow by feeding the power setpoint (eg unit which is arranged to form a setpoint for controlling said flow). Plant according to any one of the preceding claims, known; a gasifying device (10) for producing said combustible gas and a conduit means (19) the gasifying device (37) gas taking into account the supply of combustible gas to 23). is set up which is set up to supply oxygen-containing gas to pre- (10), is set up to control this supply of oxygen-containing and by the control device the afterburning device (8, is set up to control the supply (10) means that a pressure drop of a certain value obtained above (12, 24). Plant according to claims 2 and 9, (37) of oxygen-containing gas to the gasification device, the control device on the valve device 11. ll. A method for regulating the power of a power plant, comprising the steps of - burning a combustible material in a pressurized fluidized bed in a combustion chamber to form hot combustion gases, - operating a gas turbine device by means of said combustion gases, - raising the temperature of said combustion gases by means of an afterburning device to a temperature suitable for the gas turbine device, - supplying a combustible gas to the afterburning device for combustion therein to effect said temperature increase, and producing electrical power by at least one of gas turbine device driven generator, that the electrical power produced by said generator is regulated in a substantially continuous manner by means of a control device by controlling the supply of combustible gas to the afterburning device. that the electrical power produced by said generator is Method according to claim 11, it is felt for generating an effect value that a first control signal is formed by means of a first regulator taking into account a power setpoint and said effect value and that the power plant is regulated at least during a first operating condition by supplying combustible gas to the afterburner is set by means of the first control signal formed. 13. A method according to claim 12, characterized in that said power setpoint is determined by the required power of the power plant. A method according to any one of claims 11 to 13, is felt; that the temperature of the combustion gases in the area of the inlet of the gas turbine device is sensed to produce a temperature value, that a second control signal is formed by means of a second regulator taking into account a temperature setpoint and said temperature value and that operating ratio is regulated by the supply of combustible gas during a second burning device is set by means of the formed second control signal. lO 15 20 25 19 510115 15. A method according to claims 12 and 14, characterized in that it is set by means of the smallest of the first control signal supply of combustible gas afterburning device len and the second control signal. A method according to any one of claims 11 to 15, comprising; egknat_ay that a setpoint for the height of the fluidized bed is formed by coupling said power setpoint for controlling the bed height. feels; teg3naL_ay that a flow of an oxygen-containing gas is supplied to the combustion chamber by means of one driven by the gas turbine device A method according to any one of claims 11 to 16, a compressor device and that a setpoint for said flow is formed by coupling said power setpoint for controlling said flow. A method according to any one of claims 11 to 17, through; tegKnat_ay that said combustible gas is produced by means of a gasifier which is supplied with oxygen-containing gas, and that this supply of oxygen-containing gas is controlled in such a way that a certain pressure drop is obtained over a valve for setting said supply of combustible gas to the afterburning device.