FR3040438A1 - HYBRID COMBINED CYCLE ELECTRICITY PRODUCTION INSTALLATION, IMPROVED - Google Patents

Abstract

The invention relates to an installation for producing electricity from a combined cycle of a combustion turbine and a steam turbine, the installation comprising: A first water circuit, comprising said steam turbine and a steam generator; vapor recovering heat from a gas from the combustion turbine. The combined cycle is further hybridized and the installation comprises for this purpose: A second circuit of a heat transfer fluid heated by solar energy transmission. The installation comprises in particular a heat exchanger (ECH) between fluid of the second circuit and water of the first circuit, as well as: A third thermal storage circuit comprising a heat exchanger (ECH23) with fluid of the second circuit.

Description

Hybrid combined cycle power generation system, improved Field of the invention

The present invention relates to a hybrid combined cycle, improved, especially for application in a hybrid combined cycle power plant.

State of the prior art prior to the invention

Such a plant is usually a combination of a combined cycle production plant as illustrated in Figure 1, which is added a heliothermodynamic plant, for example equipped with cylindro-parabolic mirrors (often but not necessarily) as shown in FIG. 2.

With reference to FIG. 1, the principle of a combined cycle power plant is such that, at the exit of a first cycle (called "Topping") involving a gas turbine TG, the working fluid of the first cycle (called "Topping") typically) is still able to supply thermal energy to the working fluid (typically water) of a second cycle (so-called "Bottoming") involving an ST steam turbine. The first cycle involving the TG gas turbine may be a Brayton cycle. The second cycle involving the steam turbine ST may be a Rankine cycle. The corresponding installation then comprises, as represented in FIG. 1, in a first part C1 to carry out the first cycle: an air compressor AC, a supply of heat to the air CMF, by combustion of a fuel such as a fossil material MF, and the aforementioned gas turbine TG, also referred to hereinafter as "combustion turbine". The aforementioned installation further comprises, in a second part C2 to operate the second cycle: a regenerative energy steam generator GV, generally including a superheater SH, an evaporator EV cooperating with one or more balloons BA controlled vapor pressure , and an ECO economizer (it is an exchanger that heats the liquid water to its saturation limit), the aforementioned steam turbine ST, and a condenser CD at the outlet of the turbine.

This second part C2 is therefore like a water circuit, hereinafter called "first circuit" for operating the steam turbine ST.

The hot exhaust gases EVAC (typically fumes), from the gas turbine TG pass through the heat recovery steam generator GV to preheat, evaporate and superheat the circuit water in the C2 part. The combination of these two thermodynamic cycles improves the overall efficiency of a single cycle and reduces fuel costs. Nevertheless, it is still desired to reduce the consumption of the MF fossil material, both for an economic balance sheet and for an ecological balance sheet. It is then that in combined cycle plants, but hybridized in particular, the C1 part of Figure 1 is used, and the MF fossil fuel is consumed, only during the nocturnal periods or very little sunshine, while during the other periods (diurnal with a satisfactory degree of sunshine), a solar heating system is also used.

Often, such a system is used to heat the air in the first part Cl and thus improves the efficiency of the heat input of air in the C1 portion upstream of the gas turbine.

According to a first approach of the invention, the solar heating system, rather serves to heat water of the first circuit in the C2 part, to improve the efficiency of the second cycle, as shown in Figure 2.

The solar heating system used for coupling with a water circuit, of the type shown in Figure 2, may be in the form of a linear concentration system. In a system of this type, equipped with one or more MIR reflectors, the solar radiation is concentrated on a receiver tube TR for heating an HTF heat transfer fluid (called "heat transfer fluid" hereinafter), for example from 'oil. A linear concentrator system using one or more cylindro-parabolic mirrors can be used for this purpose. Other solar heating systems may alternatively be used, for example comprising one or more linear Fresnel reflectors, possibly with other types of coolant than oil.

Then, once heated, the heat transfer fluid HTF transfers its heat to the water of the first circuit in a heat exchanger ECF1 (whose hot part is referenced CFI and contains HTF fluid, and the cold part is referenced FR and contains the water). The water circulating inside the cold side FR of the heat exchanger ECH is heated by the HTF fluid until evaporation, and then superheated to implement the second cycle mentioned above.

Thus, with reference to FIG. 3, the thermal coupling then takes place between the steam generator (bottom circuit, hereinafter referred to as "first circuit" and bearing the reference 1) and the circuit including the solar thermal concentrator TR ( top circuit, hereinafter called "second circuit" and bearing the reference 2).

It will thus be understood that the second solar heating circuit 2 is added to the equipment operating the first cycle (including the TG combustion turbine), and can not completely replace these equipment in case of strong sunlight. For lower degrees of sunlight, the two thermal inputs can operate simultaneously: thermal input of the hot gas from the combustion turbine and thermal input by solar energy transmission in the second circuit. For typical nocturnal periods, only the thermal input of the gas from the combustion turbine is available.

In case of strong sunshine, when starting the "solar part" of a hybrid combined cycle, with solar input only (noted ISCC below for "Integrated Solar Combined Cycle"), the HTF fluid circulating in the solar part is cold. When sunshine is strong in particular, the HTF fluid heats up quickly. The temperature gradient between the hot HTF fluid and the water at the heat exchanger ECH (FIG. 2) is too great and risks mechanically damaging the heat exchanger ECH. One technique to avoid this disadvantage is to de-focus the mirrors to slow the temperature increase of the HTF fluid. This de-focusing leads to a potential loss of power. Currently, no solution has been provided to this problem and the power losses must simply be suffered.

On the other hand, a hybrid solar hybrid cycle works best when some solar irradiation is present. On the other hand, when the energy supplied by the sun decreases, as during a cloudy passage for example, the combustion turbine TG continues to operate under-rev (or is simply extinguished) and the yield is no longer optimal. In addition, when reaching the operating limits at low speed of the turbine TG, such as a technical minimum, it can go out. However, the frequent extinction and restart of such a combustion turbine deteriorate rapidly. Moreover, in case of low fuel prices MF, the plant may not behave optimally because it is not fully benefited from a reduction in fuel prices to save money.

The present invention improves overall this situation.

According to a second approach of the invention, a thermal storage circuit is further used in coupling with the solar thermal circuit.

Presentation of the invention

Thus, the invention proposes for this purpose a power generation plant from a combined cycle of combustion turbine and steam turbine, the installation comprising: A first water circuit, comprising said steam turbine and a steam generator recovering heat from a gas from the combustion turbine.

The combined cycle is further hybridized solar and the installation comprises for this purpose:

A second circuit of a heat transfer fluid heated by solar energy transmission. The installation within the meaning of the invention comprises a heat exchanger between the fluid of the second circuit and the water of the first circuit.

This embodiment already makes it possible to have control over the circuit of the steam turbine while leaving a form of operating independence to the combustion turbine. However, in order not to lose any surplus of thermal energy supplied to the water circuit by the gas coming from this turbine, a thermal storage circuit is provided in the installation but which is coupled to the second circuit (solar), to both to: protect the heat exchanger between the fluid of the second circuit and the water of the first circuit, and store any excess heat transmitted to the water circuit, then to the second circuit (solar) via the aforementioned exchanger .

Thus, the installation in the sense of the invention furthermore comprises:

A third circuit, thermal storage, coupled to the second circuit.

In one embodiment, the third circuit comprises for example a heat exchanger with fluid of the second circuit. In a variant, the solar thermal input can be carried out directly on a thermal storage circuit (for example in the case of a solar tower supplying solar thermal energy to a storage circuit based on molten salts).

FIG. 4 shows a possible embodiment of the installation, more completely in FIG. 4. In FIG. 4, the third aforementioned thermal storage circuit bears the reference 3 and its heat exchanger with fluid of the second circuit 2 has the reference ECH23, in this embodiment.

The third circuit 3 may comprise for example a heat transfer fluid comprising molten salts (for example fluorides, chlorides and / or nitrates). In a variant, it is possible to provide a solar thermal input directly to the water of the first circuit with Fresnel mirrors on a branch of the first circuit and, in this case, the third circuit mentioned above may itself be presented as another branch of the first circuit, water, and include a steam accumulator for thermal storage.

In general, the arrangement of the circuits and the heat exchangers, as presented above, advantageously makes it possible to control the installation globally and not individually and separately each of the three subsystems: solar, thermal storage and steam. For this purpose and by way of example, the third circuit may comprise, for example, a cold coolant (RF) reservoir and a hot coolant (RC) reservoir, and the installation then comprise a level control module. fluid in the cold reservoir (C33) and a fluid level control module in the hot reservoir (C34). We will see later in examples of controlled control of the installation how these two parameters intervene. The aforementioned control modules can act on valves and / or pumps adapted for this purpose, provided in the third circuit.

In Figure 4, the reference "C" designates pumps provided as an exemplary embodiment in the various circuits. The valves are conventionally represented by two inverted triangles.

Furthermore, the second circuit (2) may comprise a charge control module (C31) and a fluid discharge control module (C32) of the second circuit in the heat exchanger (ECH23) with the third circuit, in the embodiment illustrated in Figure 4. Again, these control modules can act on valves and / or pumps adapted for this purpose, provided in the second circuit. In particular, these control modules are here intended to control together the two parameters corresponding to: the enthalpy in charge, noted hereinafter hch, and the enthalpy in discharge, hereinafter referred to as hdch, of the HTF fluid in the coupling with the third circuit (3). These two parameters intervene in the regulated control of the installation, as presented in the exemplary embodiments detailed below.

Furthermore, the installation can furthermore comprise an input control module (C22) and an outlet control module (C21) of water of the first circuit in the heat exchanger (ECH) with fluid of the second circuit. Again, these control modules can act on valves and / or pumps adapted for this purpose, provided in the first circuit. In particular, these control modules are here intended to control together the two parameters corresponding to: the enthalpy, denoted hereinafter h, and the flow rate, denoted hereinafter Q, of the steam in the coupling with the second circuit ( 2). These two parameters intervene in the regulated control of the installation, as presented in the exemplary embodiments detailed below.

Furthermore, the steam generator comprises a plurality of water flasks (liquid and / or vapor) at respective pressures, and the installation comprises a plurality of control modules (Cl2, Cl3, Cl4) of respective levels of water in the balloons. More specifically, in one exemplary embodiment, an HP high pressure balloon is provided, the level of which is controlled by a module Cl4, a medium pressure balloon MP whose level is controlled by a module Cl3, and a low pressure balloon. BP whose level is controlled by a Cl2 module. These three water level parameters in the balloons are noted below respectively CNHP, CNMp and CNBp and are also involved in the controlled control of the installation in the examples given below.

Furthermore, the installation may further comprise a power generation control module for combustion and steam turbines (Cil). This parameter is noted RP below and is also involved in the controlled control in the examples given below.

Furthermore, in addition or alternatively, the installation may furthermore comprise an individual power generation control module of the combustion turbine (C4) for controlling the installation in the event of transients related to a variation in sunshine. Such an embodiment will be described in detail later, in an example of controlled control of the installation in such a situation of variation of sunshine and / or in the case of low-speed operation of the combustion turbine notwithstanding a strong degree of sunshine. The installation can then comprise a computer circuit (for the hardware part) for generating instructions for equipment control modules of the installation. Thus, as illustrated in FIG. 5, this computer circuit can be in a computer typically comprising an ECR screen, an input means (SOU mouse, a keyboard, a touch screen, or other), and a central processing unit UC. Many other embodiments are possible. It can be an ASIC or other circuit. In the example of FIG. 5, the computer circuit is in the central processing unit UC and typically comprises a processor PROC and a working memory MEM which can store, in addition to calculation data, computer program instructions for preparing instructions. control of an installation within the meaning of the invention. For this purpose, the aforementioned computer circuit further comprises an interface INT connected to the processor on the one hand, and to the various control modules C4 to C34. The invention thus also relates to a method of controlling an installation comprising such a computer circuit, and comprising N equipment control modules of the installation (C4 to C34). In particular, the method comprises the steps, with reference to FIG. 6: a) determining an overall operating speed of the installation (typically a nominal operating reg regime, referred to in step S1), and b) elaborating , as a function of said overall speed, a set number (Ci in step S2) less than or equal to the number N, these setpoints being intended for equipment control modules of the installation, to arrive at said overall operating regime .

It will thus be understood that, as indicated above, the arrangement of the circuits and of the heat exchangers in the installation in the sense of the invention advantageously makes it possible to control the installation globally (in a closed loop) and not individually and separately (in "open" loop, suboptimal) each of the three subsystems: solar, thermal storage and steam.

The method may further comprise the following step: - at the beginning of use of the second circuit (solar, in step S3), set a constraint (CRsol in step S4) to use the third circuit to limit a temperature gradient between the fluid of the second circuit and the water of the first circuit.

In practice, this new constraint requires reducing the number of instructions that can be given to N-1 (this constraint takes a degree of freedom of management of the installation).

This embodiment makes it possible to manage situations with a high degree of sunshine, which can damage the ECH exchanger between the water circuit (1) and the "solar" circuit (2) and then implements the thermal storage circuit (3). , as will be seen in an example of controlled control below. The invention also relates to a computer program (for the software development of command instructions) comprising instructions for implementing the above method (and a non-transitory memory medium storing such instructions), when this program is executed by a processor (for example the processor PROC of the computer circuit shown in FIG. 5). Figure 6 previously described may correspond to an example of a general flow chart of such a computer program.

Other features and advantages of the invention will become apparent from consideration of the detailed description below, and the accompanying drawings in which: Figure 1 schematically illustrates the operation of a combined cycle; FIG. 2 represents a solar energy supply circuit; FIG. 3 schematically illustrates the operation of a hybridized combined cycle with a solar energy supply circuit of the type shown in FIG. 2; FIG. 4 schematically illustrates an installation according to an exemplary embodiment of the invention, including in particular a thermal storage circuit 3; FIG. 5 schematically illustrates a computer circuit for controlling an installation according to an exemplary embodiment of the invention; FIG. 6 schematically illustrates steps of a method for controlling an installation according to an exemplary embodiment of the invention.

It is therefore proposed here to add a thermal storage means and a coordinated control to assist start-up in solar mode, or to help the operation of the plant in the aforementioned limiting cases of under sunlight in particular.

Coordinated control makes it possible to control the operation of the hybrid combined cycle by coordinating the three circuits of the production plant illustrated in Figure 4, optimally using thermal storage. These three circuits are: a circuit 1 for the combined cycle, with circulation of water, a circuit 2 of the solar thermal concentrator, with for example a circulation of oil as heat transfer fluid HTF, and a thermal storage circuit 3, with circulation of a fluid having thermal storage capacities (for example containing molten salts).

Thermal storage can store excess heat from the oil.

Such an embodiment makes it possible to avoid de-focusing the mirrors in the event of strong sunlight. The loss of power is therefore limited.

Moreover, in the event of a fall in insolation, the coordinated regulation may control one or more control modules of the thermal storage circuit 3 to produce steam in the circuit 1 in place of the solar concentrator 2 (via heat exchangers ECH23 and ECH). The yield then continues to be optimal.

In addition, this thermal storage can be used to prevent stopping of the TG combustion turbine. When the latter must pass under its technical operating minimum, instead of extinguishing it, it blocks the operation of the turbine TG minimum technical to store the surplus energy produced in at least one of the RC tanks of molten salts 3. In the example described here, the thermal storage considered is an indirect storage of molten salts with two reservoirs as illustrated in FIG.

Finally, thermal storage can also make it possible to use the TG combustion turbine at its maximum when the price of MF fuel is cheaper. Indeed, when the price of the fuel decreases, the energy production is used as much as possible by the turbine TG and the excess energy produced can be stored in the circuit 3.

With regard to the coordination of the operation of the installation, a computer circuit (FIG. 5) acting as a coordinator and acting as a controller that retrieves information from different sensors provided in the subsystems of the installation is provided. (combined cycle with circuit 1, solar circuit 2, storage circuit 3), which optimizes a global problem (power generation). The coordinator calculates the instructions for each subsystem. These subsystems each have local controls to fulfill the instructions sent by the coordinator (via the aforementioned control modules).

To ensure a good compromise between control performance and solicitation of commands, a quadratic linear command with an integral action, using states reconstructed by observations, is synthesized.

The coordinator controls the setpoints against reference values that are chosen to satisfy a global demand. For this purpose, integral actions are added to a state vector x, as described below: • The hybrid combined cycle (HCC) power P must follow the desired overall power setpoint RP (commanded by the Hybrid Combined Cycle). by the Cil module). Thus, a new variable is introduced:

• The setpoints (commanded by the modules C12, C13, 04) on the three levels of the balloons (CNbp, CNmp, CNhp) must follow their equilibrium values (RNbp, RNmp, RNhp). The goal is to keep the level in each balloon within a certain range of values. Thus, three new variables are defined:

• The steam flow at the coupling output with the solar part (Q) must follow the value of the input water flow of the solar part (Qin). So, a new variable is added:

• The enthalpy of the steam at the outlet of coupling with the solar part (h) must follow the value of the enthalpy of the vapor in the combined cycle gas (with the turbine TG) (cycle noted CCG) at the injection point (noted hcc below) at the superheater SH. Thus, another new variable is also defined:

The flow rate Q and the enthalpy h are controlled together by the modules C21 and C22 of FIG. 4. The enthalpies of the HTF fluid at the outlet of the charge and discharge line (hch, hdch) from the coupling with the third circuit (piloted by the modules C31 and C32), must follow the enthalpy values of the HTF fluid at the injection point of the charge and discharge line in the solar part (Rhch, Rndch) (at the concentrators TR). This makes it possible to inject HTF oil into the solar part of the second circuit (especially at the TR concentrators) while always respecting the high temperature limits of the HTF oil. This also makes it possible to produce steam in the circuit 1, even possibly in the absence of solar irradiation. We note the new variables:

• The levels of the cold and hot tanks (noted here Lrf and IIe) (controlled by the modules C33 and C34) must follow the equilibrium value of these levels (RLrf, Laugh). This makes it possible to always maintain an equilibrium thermal stock in each of the tanks. In addition, if one tank fills, the second empties all the same and vice versa. Thus, a single integrator is necessary to influence the behavior of the two tanks:

In an exemplary embodiment, the temperature gradient between the oil and the water in the coupling between the circuits 1 and 2 (denoted δτ) can also be controlled. It must follow an imposed reference (RsT) that limits its variation and prevent the solar oil from heating too quickly compared to the solar steam. The corresponding variable is noted:

• In a variant, the power produced by the combustion turbine (Ptac) · The latter must follow a reference (RpTAC) imposed by the control module C4. Most of the time, this reference corresponds to a percentage of the total power produced by the installation, but depending on the case, this reference can be modified and in any case the new variable is noted:

The final order law therefore takes the following form:

with z = [z 1 ··· z10] and K, H the controller gains, calculated by minimizing the quadratic cost function:

where xe = [x z] is the state vector of the extended system: regrouping the states of the system x and the integrators zL.

The weightings Q and R in the integral expression above are chosen to ensure precise control of the outputs with an appropriate action on the control variables while limiting as much as possible the variations in the power produced by the combustion turbine TG.

The advantages associated with the use of a thermal storage, as proposed in the installation within the meaning of the invention, are multiple:

The operating flexibility of the installation as a whole is improved, which makes it possible to relax its technical and economic constraints, to improve the quality of production.

Demand-side management of energy supply and the quality and flexibility required by the power grid operator are better. Energy can be transferred according to time slots according to supply and demand daily, monthly or seasonal. Energy consumption is not constant over a day. In other words, storage allows power to be shifted between peak and off-peak hours, reducing production costs.

The consumption of fossil fuel can then be reduced because the storage can make it possible to use as much as possible the solar energy.

Moreover, such an installation makes it possible to manage its operation in coordination (in a closed loop) and the advantages associated with co-ordination steering are also numerous:

Optimize the performance of the installation by improving the dynamic performance of the subsystems;

Increase their capacity to participate in systems services (this is the management of the primary and secondary reserve: 90% of demand must be answered in 30 seconds and 50% in 15 seconds). ;

To overcome the problems of intermittency of so-called "fatal" energies, facilitating their integration into the global energy supply;

Optimize the flexibility of the installation; Reduce fuel consumption.

Of course, the present invention is not limited to the embodiments described above by way of example; it extends to other variants.

Thus, as an alternative to using cylindro-parabolic mirrors and indirect storage of molten salts with two reservoirs as illustrated in FIG. 4, it is possible to provide a solar tower with direct solar thermal input to molten salts with two reservoirs on each side. else of the solar tower. Thus, the second and third aforementioned circuits become merged and the solar part becomes a "branch" of a single circuit (with the equivalent of the heat exchanger ECH23 at the solar tower). Moreover, in another variant, the three aforementioned circuits 1, 2 and 3 can be combined into a single water circuit, one branch of which carries Fresnel mirrors for the solar thermal input, and another branch comprises a Steam accumulator for thermal storage.

Claims (13)

claims 1. Installation for generating electricity from a combined cycle of a combustion turbine and a steam turbine, the installation comprising: a first water circuit comprising said steam turbine and a steam generator recovering from the heat of a gas from the combustion turbine, the combined cycle being further hybridized and the installation comprising: a second circuit of a heat transfer fluid heated by solar energy transmission, the installation being characterized in that it comprises a heat exchanger (ECH) between fluid of the second circuit and water of the first circuit, and in that it further comprises: A third thermal storage circuit, coupled with the second circuit. 2. Installation according to claim 1, characterized in that the third circuit comprises a heat exchanger (ECH23) with fluid of the second circuit. 3. Installation according to one of claims 1 and 2, characterized in that the third circuit comprises a heat transfer fluid comprising molten salts. 4. Installation according to one of the preceding claims, characterized in that the third circuit comprises a cold coolant reservoir and a hot heat transfer fluid reservoir, and in that the installation further comprises a level control module. fluid in the cold reservoir (C33) and a fluid level control module in the hot reservoir (C34). 5. Installation according to claim 2, characterized in that the second circuit comprises a load control module (C31) and a fluid discharge control module (C32) of the second circuit in the heat exchanger (ECH23) with the third circuit. 6. Installation according to one of the preceding claims, characterized in that it further comprises an input control module (C22) and an outlet control module (C21) water of the first circuit in the exchanger of heat (ECH) with fluid of the second circuit. 7. Installation according to one of the preceding claims, characterized in that the steam generator comprises a plurality of water balloons at respective pressures, and in that the installation comprises a plurality of control modules (Cl2, Cl3 , Cl4) respective levels of water in the balloons. 8. Installation according to one of the preceding claims, characterized in that it further comprises a power generation control module of the combustion and steam turbines (Cl 1). 9. Installation according to one of the preceding claims, characterized in that it further comprises a control module for individual power production of the combustion turbine (C4) for controlling the installation in case of transients related to a variation. sunshine. 10. Installation according to one of the preceding claims, characterized in that it comprises a computer development of instructions for equipment control modules of the installation. 11. A method of controlling an installation according to claim 10, comprising N equipment control modules of the installation, characterized in that it comprises the steps of: a) determining an overall operating speed of the installation, and b) developing, according to said overall regime, a number of setpoints less than or equal to the number N, for equipment control modules of the installation, to achieve said overall operating regime. 12. The method of claim 11, characterized in that it further comprises the step: - at the beginning of use of the second circuit, set a constraint to use the third circuit to limit a temperature gradient between the fluid of the second circuit and the water of the first circuit, said constraint imposing a number of instructions limited to Nl. 13. Computer program characterized in that it comprises instructions for the implementation of the method according to one of claims 11 and 12, when the program is executed by a processor.