Improved thermal power plant

Abstract

The present invention relates to a thermal power plant for producing electricity or motive power comprising at least one boiler (1) using fuel or heat recovery, at least one turbine, at least one main circuit for circulating a working fluid, at least one tank (6) located in the boiler (1) on said main circuit, at least one reheating module (8) and at least one secondary circuit (9) in which a reheating fluid circulates, in which: said main circuit comprises at least one initial section (3c) located in said at least one boiler (1), at least one first section (3a) for sending working fluid from said at least one boiler (1) to a first set of at least one turbine section (2a), and a second section (3b) for sending working fluid from said first set of at least one turbine section (2a) to a second set of at least one turbine section (2b),said working fluid in said tank (6) being at the nominal load point at a main pressure level, andsaid reheating module (8) comprises at least one downstream heat exchanger (11) located at the second section (3b) of the main circuit, characterized in that said secondary circuit (9) comprises at least one upstream heat exchanger (10) located in said boiler (1), said reheating fluid circulating in said secondary circuit (9) between the upstream (10) and downstream (11) heat exchangers, said reheating fluid being at the outlet of the upstream heat exchanger (10) at the nominal load point at a secondary pressure level, and said secondary pressure level being at least ten bars higher than said main pressure level. The present invention also relates to a method for producing electricity in a thermal power station according to the invention. Abstract figure: Figure No. 1,

Description

Title of the invention: Improved thermal power station

[0001] The present invention relates to the field of electricity or motive power production. It relates more particularly to a thermal power plant for producing electricity or motive power.

[0002] A thermal power plant usually comprises one or more boilers in which fuels are burned and / or one or more recovery boilers. The heat produced in the boiler(s) is used to heat a working fluid, which is then conveyed to at least one turbine to set it in motion. The movement of the turbine produces motive power or enables an alternator to produce electricity. In the particular case of a waste incineration power plant, the working fluid is usually in the boiler(s) at a pressure level of between 20 and 85 bars.

[0003] In order to increase the efficiency of thermal power plants, they can operate according to a Rankine cycle with reheating. In this case, the turbine(s) comprises at least two sections, and at least one reheating module makes it possible to reheat the working fluid between two sections of the turbine. To do this, said reheating module can be of various designs. In the most common case (internal reheating), it is located at least partly in the boiler and reheats the working fluid in contact - for example - with combustion fumes. In other cases, it can be external to the boiler and be supplied by various heat sources, for example from external processes or from the working fluid itself. For example, in the case of thermal power plants for waste incineration, attempts have been made to use a working fluid at a high pressure level, for example greater than 70 bars, associated with external reheating.In the case of thermal power plants using other types of fuel or waste heat, the use of reheating cycles is also very frequently coupled with high working fluid pressure levels. This improves efficiency, but managing this pressure level has a number of drawbacks, particularly noticeable when it comes to waste fuels: .

[0004] - the investment cost of a boiler and a working fluid circuit at high pressure level is higher than for a conventional pressure level, - a high pressure boiler has a higher wall temperature, which results in faster degradation of the refractories and a higher wear rate of the first pass tubes. More maintenance is therefore required, and the unavailability rate is not The boiler's programmed pressure is higher than for a conventional pressure level. - the turbine unavailability rate is higher than in a plant without reheating, because the turbine most often cannot operate when the reheating stage is unavailable, due to the high condensation rate in the low-pressure stages of the turbine in the absence of reheating. The main causes of unavailability of the reheating stage are failures of any pumps linked to reheating and leaks at a reheating exchanger. For plants with internal reheating, a leak at a reheating exchanger can also lead to unscheduled unavailability of the boiler.

[0005] Finally, the gain in electrical efficiency is partly cancelled out by these additional costs and by the reduction in electrical production caused by these additional unavailabilities.

[0006] In the case of a thermal power station where part of the fuel is waste, or an energy recovery unit (UVE), these problems are even more significant because the fumes are corrosive, which already poses problems of wear on the boilers at a conventional pressure level.

[0007] An object of the present invention is to provide a thermal power plant with improved efficiency while reducing manufacturing and operating costs.

[0008] Another object of the present invention is to provide a thermal power plant compatible with the combustion of waste with improved efficiency.

[0009] The object of the present invention is to respond at least in part to the aforementioned objects by proposing a thermal power station comprising, in addition to the conventional main circuit of the working fluid actuating a turbine, a second so-called secondary circuit in which a reheating fluid circulates, the reheating fluid being heated in the boiler and then used to reheat the working fluid. To this end, it proposes a thermal power station for producing electricity or motive power comprising at least one fuel-fired or heat-recovery boiler, at least one turbine, at least one main circuit for circulating a working fluid, at least one tank located in the boiler on said main circuit, at least one reheating module and at least one secondary circuit in which a reheating fluid circulates, in which:

[0010] - said main circuit comprises at least one initial section located in said at least one boiler, at least one first section making it possible to send working fluid from said at least one boiler to a first set of at least one turbine section, and a second section making it possible to send working fluid from said first set of at least one turbine section to a second set of at least one turbine section, said working fluid in said balloon being at the nominal load point at a main pressure level, and - said reheating module comprises at least one downstream heat exchanger located at the level of the second section of the main circuit.

[0011] This power station is particular in that said secondary circuit comprises at least one upstream heat exchanger located in said boiler, said reheating fluid circulating in said secondary circuit between the upstream and downstream heat exchangers, said reheating fluid being at the outlet of the upstream heat exchanger at the nominal load point at a secondary pressure level, and said secondary pressure level being at least ten bars higher than said main pressure level.

[0012] Thanks to these arrangements, the working fluid can be reheated without needing to be itself at a high pressure level in the boiler, which makes it possible to reduce the number of elements of the plant in which a high pressure fluid circulates. This makes it possible to use more elements such as economizers, tanks, superheaters, evaporators and other evaporative exchange surfaces (walls, etc.) not compatible with a high pressure level, and therefore less expensive, and to reduce wear due to the temperatures associated with the high pressure levels in these elements of the plant.

[0013] According to other characteristics:

[0014] - said fuels may include waste such as household waste, waste from economic activities, hazardous waste, biomass, sewage sludge, or even medical waste, said main pressure level being between 20 and 85 bars, and said secondary pressure level being greater than 70 bars, this type of power station being particularly suitable for the invention, because the corrosive fumes do not usually allow internal reheating fed by the fumes from the boiler under satisfactory conditions, - the reheating fluid circulating in said secondary circuit between the upstream exchanger and the downstream exchanger can be in the liquid state, which makes it possible to avoid phase changes in the secondary circuit, and in particular to avoid the installation of a second boiler tank on the secondary circuit, which would make the plant more expensive and more complex to operate, - said boiler can comprise a flue gas circuit, and said upstream heat exchanger can be located in said flue gas circuit of said boiler, this being a simple and effective embodiment of the invention, - said secondary circuit may comprise at least one pump making it possible to reach the secondary pressure level, which is an embodiment simple and robust of the invention, - said secondary circuit can be supplied with reheating fluid by at least two separate sources, the pressure and / or temperature level of the two sources being different, which makes it possible to effectively regulate the flow rate and / or the temperature of the reheating fluid, and thus the temperature of the reheated working fluid, - said thermal power station may also include: - a first temperature sensor on the second section of the main circuit, downstream of said downstream heat exchanger, - a pressure sensor, located on said secondary circuit, - a second temperature sensor, located on said secondary circuit between said upstream heat exchanger and said downstream heat exchanger, and - a regulation system connected to the first and second temperature and pressure sensors, and to at least one valve for regulating the flow rate of a source of reheating fluid of the secondary circuit,

[0015] which is a simple and effective means of regulating the temperature of the reheated working fluid, while making it possible to avoid reaching the boiling point of the reheating fluid in the case where the latter is liquid.

[0016] - said thermal power station may comprise at least one economizer located on the initial section of the main circuit, at least part of the supply of reheating fluid to the secondary circuit coming from an outlet of said economizer and / or from a condensate and feedwater circuit, which are easily accessible sources allowing a diversity of sources for the secondary circuit, - said reheating fluid can be sent after said downstream heat exchanger, to a tank located in said boiler and / or to a condensate and feedwater circuit, which allows a drop in pressure of the reheating fluid, and a recovery of the calories that it transports in the operation of the power station.

[0017] The present invention also relates to a method for producing electricity or motive power in a thermal power station according to the invention, comprising the following steps:

[0018] - combustion of fuels or recovery of heat in at least one boiler, - in said boiler, enthalpy increase of a working fluid in a main circuit, and enthalpy increase of a reheating fluid in a secondary circuit, - sending said working fluid into at least a first set of at least one turbine section, - sending said working fluid from said first set of at least one turbine section to at least one downstream heat exchanger of a reheating module, and sending said reheating fluid from the boiler to said downstream heat exchanger, - heat transfer from said reheating fluid to said working fluid in said downstream heat exchanger, - sending said working fluid from said downstream heat exchanger to a second set of at least one turbine section.

[0019] Thanks to these arrangements, the working fluid can be reheated without needing to be at a high pressure level in the boiler itself, which makes it possible to reduce the number of elements of the plant in which a high pressure fluid circulates. This makes it possible to use more elements such as economizers, tanks, superheaters, evaporators and other evaporative exchange surfaces (walls, etc.) not compatible with high pressure, and therefore less expensive, and to reduce wear due to the temperatures associated with high pressure in these elements of the plant.

[0020] The present invention will be better understood on reading the detailed description which follows, with reference to the appended figures in which:

[0021] [Fig-1] [Fig.l] is a diagram of the operation of a thermal power station according to a preferred embodiment of the invention.

[0022] The thermal power station according to the invention, illustrated in a preferred embodiment in [Fig.l], makes it possible to produce electricity or motive power from the combustion of fuels or recovered heat in at least one boiler 1.

[0023] The fuels may include fossil fuels such as coal, natural gas, or fuel oil. They may also include biomass, biogas, or syngas. In a preferred embodiment of the invention, the fuels include waste such as household waste, waste from economic activities, hazardous waste, biomass, sewage sludge, or medical waste. The thermal power plant includes at least one turbine, comprising at least two sets of at least one turbine section 2a, 2b, and a main circuit for supplying enthalpy to a working fluid in the boiler 1 and for circulating the working fluid from the boiler 1 to the turbine. The working fluid is, for example, water, which may be in liquid form at certain stages and in steam form at other stages.The turbine converts the thermal energy from boiler 1 via the working fluid into movement. This movement can then be recovered by an alternator to generate . electricity or be used as motive power.

[0024] The main circuit comprises, downstream of the boiler 1, at least two sections, including a first section 3a for sending working fluid from the boiler 1 to the first set of at least one turbine section 2a, and at least one second section 3b for sending working fluid from the first set of at least one turbine section 2a to the second set of at least one turbine section 2b. A particular embodiment of the invention will be described below using the example of a single first section 3a and a single second section 3b, but the invention is implemented without difficulty in a similar manner with several first sections 3a and several second sections 3b, for example in the case of a multi-stage reheating cycle, or parallel sections due to the number of turbines or the number of reheating modules 8 in the thermal power plant.

[0025] Upstream of the first section 3a, the main circuit comprises an initial section 3c located in the boiler, making it possible to increase the enthalpy of the working fluid. The initial section 3c comprises a tank 6, possibly several tanks 6, making it possible to separate the phases of the working fluid. The initial section 3c may comprise one or more economizers 4, in order to heat the working fluid when it is in the liquid state and / or one or more evaporating surfaces, in order to change the working fluid from a liquid state to a gaseous state and / or one or more superheaters 5, making it possible to heat the working fluid when it is in the gaseous state. A tank 6 may be arranged for example between an economizer 4 and a superheater 5.

[0026] In the embodiment of [Fig.l], the initial section 3c comprises three economizers 4, four superheaters 5, a tank 6 and evaporator surfaces (not shown) connected to the tank.

[0027] The working fluid in the tank 6, at the nominal load point, is at the main pressure level, for example between 20 and 85 bars in the case of waste incineration. In the second section 3b, after having transferred part of its energy to the first set of at least one turbine section 2a, the working fluid is at a so-called intermediate pressure level, lower than the main pressure level. In the case of a waste incineration thermal power plant without a reheater, the working fluid is typically at a temperature between 320 and 480°C in the first section 3a, the temperature of the working fluid in the first section 3a being higher than in the second section 3b.

[0028] After entering the first set of at least one turbine section 2a, respectively the second set of at least one turbine section 2b, the working fluid drops in temperature and / or pressure by setting the first set of at least one turbine section 2a, respectively the second set of at least one turbine section 2b in motion.

[0029] At the outlet of the first set of at least one turbine section 2a, all of the working fluid can be entirely returned to the second section 3b of the main circuit. Alternatively, only a portion of the working fluid can be returned to the second section 3b of the main circuit and another portion can be withdrawn to a condensate and feedwater circuit 7 or to other processes external or internal to the thermal power plant making it possible to reuse the working fluid and for example the thermal energy that it still contains. There can also be withdrawals of a portion of the working fluid within the first and second sets of at least one turbine section 2a, 2b to the condensate and feedwater circuit 7 or to other external or internal processes.At the outlet of the second set of at least one turbine section 2b, all of the working fluid can be directed to the condensate and feedwater circuit 7, which can include a working fluid condensation step, or to other external or internal processes. At the outlet of the external or internal processes mentioned above, the working fluid can be returned for example to a condensate and feedwater circuit 7.

[0030] The condensate and feedwater circuit 7 can then be used as a source of fluid for the main circuit, for example by connecting it to the initial section 3c, and / or for the secondary circuit 9 described below.

[0031] The thermal power station also comprises at least one reheating module 8, making it possible to reheat the working fluid between two sets of at least one turbine section 2a, 2b.

[0032] The reheating module 8 is supplied with thermal energy by a secondary circuit 9, in which a reheating fluid circulates. The reheating fluid is for example water, which may be in liquid form at certain stages, and in other stages in vapor form. In the embodiment of [Fig.l], the reheating fluid is in liquid form. The secondary circuit 9 is itself supplied with thermal energy by one or more upstream heat exchangers 10 located in the boiler 1. Thermal energy is therefore transferred from the boiler 1 to the reheating fluid circulating in the secondary circuit 9, via the upstream heat exchanger 10.

[0033] The upstream heat exchanger 10 is for example located in a flue gas circuit of the boiler 1, and the upstream heat exchanger 10 makes it possible to transfer heat from the combustion or recovery flue gases to the reheating fluid circulating in the secondary circuit 9. The upstream heat exchanger 10 can for example be placed between two superheaters 5, or in any other relevant location of the boiler.

[0034] The upstream heat exchanger 10 may comprise one or more elements located on the secondary circuit 9, in the boiler 1, among which one or more eco nomizers, in order to heat the reheating fluid when it is in the liquid state and / or one or more evaporating surfaces, in order to change the reheating fluid from a liquid state to a gaseous state and / or one or more superheaters, making it possible to heat the reheating fluid when it is in the gaseous state. The secondary circuit 9, in the boiler 1, may also comprise one or more tank(s), making it possible to separate the phases of the reheating fluid when it changes to the gaseous state.

[0035] The reheating module 8 comprises one or more downstream heat exchangers 11, located at the second section 3b of the main circuit. In the downstream heat exchanger 11, thermal energy is transferred from the reheating fluid circulating in the secondary circuit 9 to the working fluid circulating in the second section 3b of the main circuit.

[0036] The reheating fluid therefore circulates between the upstream 10 and downstream 11 heat exchangers, in order to transfer thermal energy from the boiler to the working fluid circulating in at least one second section 3b, said second section 3b connecting a first set of at least one turbine section 2a to a second set of at least one turbine section 2b. At the outlet of the upstream heat exchanger 10, the reheating fluid is at a secondary pressure level, for example greater than 70 bars in the case of a waste incineration plant. The secondary pressure level is at least ten bars higher than the main pressure level. Such a differential in pressure levels is advantageous because it makes it possible, in the secondary circuit, to reach the temperatures necessary for reheating, and in the main circuit, to avoid having to use high pressures.

[0037] At the inlet of the reheating module 8, the working fluid is preferably in the form of vapor. In certain embodiments, it may be in two-phase form. In this case, it then comprises, for example, a high percentage of vapor and a low percentage of liquid, for example 98% and 2%, percentages which depend in particular on the vapor characteristics at the inlet of the turbine, the efficiency of the turbine, and the reheating pressure level. A separation of the phases is then carried out in the reheating module 8, and the liquid phase is discharged, typically to the condensate and feedwater circuit 7 or to other processes.

[0038] At the inlet of the downstream heat exchanger 11, the reheating fluid is preferably in liquid form. It can also be in gaseous form. In the latter case, the thermal power station typically comprises a tank located in the boiler on the secondary circuit. In a particular embodiment of the invention, the reheating fluid at the inlet of the downstream heat exchanger 11 is in gaseous form, in a state close to its condensation temperature, for example at a pressure level of between 85 and 145 bars and a temperature of between 300 and 340°C. When the reheating fluid enters the exchanger downstream heat exchanger 11 in gaseous form, it transfers heat to the working fluid, and quickly reaches its condensation temperature; at this point it is in the best conditions to transfer heat, with a condensation heat transfer coefficient. At the outlet of the downstream heat exchanger 11 the reheating fluid has transferred enough heat to the working fluid to return to a liquid state.

[0039] In order to achieve the secondary pressure level, the secondary circuit 9 may comprise one or more pumps 12. The use of dedicated pumps 12 makes it possible to pressurize the reheating fluid only in the necessary sections, in order to reduce the number of elements of the power plant which must be compatible with high pressure. Alternatively, the source(s) supplying the secondary circuit 9 may deliver a high-pressure fluid.

[0040] The pump 12 is preferably provided with a bypass 13 equipped with a non-return system. If the pump 12 can no longer operate, the secondary circuit 9 can thus continue to be supplied automatically, although at a pressure level different from the nominal pressure level of the secondary circuit.

[0041] After passing through the downstream heat exchanger 11, the reheating fluid, which has dropped in temperature and / or pressure, leaves the reheating module 8 via a condensate circuit of the reheating module 21. It can then be sent to one or more of the following destinations: the initial section 3c of the main circuit, which corresponds to a preferred embodiment of the invention, where the reheating fluid is sent to the tank 6 located on the initial section 3c, and the reheating fluid is incorporated into the working fluid, the secondary circuit 9 at the upstream heat exchanger 10, the condensate and feedwater circuit 7, or an internal or external process.When the reheating fluid leaves the condensate circuit of the reheating module 21, it may "flash", i.e. partially evaporate, depending on the respective pressure and temperature levels of the condensate circuit of the reheating module 21 and the destination system. This flash phenomenon may require suitable installations, such as a flash tank, or the use of a boiler tank such as tank 6.

[0042] The supply of reheating fluid to the secondary circuit 9 may be provided, in a non-limiting manner, by one or more of the following sources: the condensate and feedwater circuit 7, the condensate circuit of the reheating module 21, an internal or external process having a fluid at relevant conditions at its outlet, or even one or more elements located in the initial section 3c of the main circuit such as an economizer 4, or a tank 6.

[0043] Preferably, the supply of reheating fluid to the secondary circuit 9 is provided by at least two separate sources, each of the sources providing a fluid with different temperature and / or pressure parameters. The secondary circuit 9 then comprises a mixing means 14 to which the different sources are connected. This makes it possible to regulate the secondary circuit 9 by adapting the parameters of the inlet reheating fluid, for example to changes in boiler load, changes in boiler fouling levels and other variations in the boiler operating conditions such as fuel quality, or the O2 level in the flue gases. The plurality of sources makes it possible both to regulate the flow rate and the temperature of the reheated working fluid and to ensure that the boiling point of the reheating fluid is not reached in the secondary circuit 9, in the case where the secondary circuit is designed to be entirely in the liquid phase.To do this, the flow rates of the supply sources of the secondary circuit 9 can be adjusted by one or more control valves 15 controlled by a control system 16. The control system 16 can determine the commands to be sent to the control valves 15 based on one or more measurements originating for example from: .

[0044] - a first temperature sensor 17 on the second section 3b of the main circuit, downstream of the downstream heat exchanger 11, - a pressure sensor 18, located on the secondary circuit 9 downstream of a possible pump 12, - a second temperature sensor 19, located on the secondary circuit 9 between the upstream heat exchanger 10 and the downstream heat exchanger 11.

[0045] In the embodiment illustrated in [Fig.l], the secondary circuit 9 is supplied by a source at the output of an economizer 4, and a source connected to the condensate and feedwater circuit 7.

[0046] The plurality of sources with different pressure and / or temperature parameters makes it possible both to regulate the temperature of the reheated working fluid and to ensure that the boiling point of the reheating fluid is not reached in the secondary circuit 9. If only one source is used to supply the secondary circuit 9, it is not possible to regulate these two parameters independently. The system can then operate by prioritizing the parameters according to the situations.

[0047] The control valves 15 may be three-way valves, or simple two-way control valves. As illustrated in [Fig.l], a three-way control valve 15 may for example be used to recover fluid from the main circuit, in this example between two economizers 4. In this example, the two-way control valve 15 may be used to regulate the temperature of the reheating fluid downstream of the upstream heat exchanger 10, as a function of the pressure level of the secondary circuit 9, which may for example be measured downstream of a pump 12 or downstream of the upstream heat exchanger 10, in order to ensure that the point boiling point of the reheating fluid is not reached in the secondary circuit 9. The three-way control valve 15 can regulate the temperature of the reheated working fluid, also depending on the pressure level of the secondary circuit 9.

[0048] One or more control valves 15 may be doubled with a bypass system, for example by means of one or more manual valves 20 or automatic valve or control valve, in order to allow a degraded operating mode in the event of a problem with the control valve(s) 15.

[0049] The present invention also relates to a method for producing electricity or motive power in a thermal power station according to the invention, comprising the following steps:

[0050] - combustion of fuels and / or recovery of energy, where appropriate from waste, in at least one boiler 1, - in said boiler 1, enthalpy increase of a working fluid in a main circuit, and enthalpy increase of a reheating fluid in the secondary circuit 9, the secondary circuit being at a pressure level higher than that of the main circuit, the difference in pressure level between the circuits being at least 10 bars, - sending said working fluid into at least a first set of at least one turbine section 2a, - sending said working fluid from said first set of at least one turbine section 2a to at least one downstream heat exchanger 11 of a reheating module 8, and sending said reheating fluid from the boiler 1 to said downstream heat exchanger 11, - heat transfer from the reheating fluid to the working fluid in said downstream heat exchanger 11 of the reheating module 8, - sending said working fluid from said downstream heat exchanger 11 to a second set of at least one turbine section 2b.

[0051] Various technical problems may result in the target reheating temperature of the working fluid downstream of the downstream heat exchanger 11 not being reached. This may be, for example, the unavailability of the pump 12 or another pump, a leak in the downstream heat exchanger 11, or an incident on a control valve 15. In a conventional thermal power plant with a reheating cycle, the failure to reach the target reheating temperature at this location may require the shutdown of part of the turbine. The reason for this shutdown is the need to avoid damaging the last section of the second set of at least one turbine section 2b in the event of excessive condensation due to the absence of reheating. The shutdown of the last section of the set of at least one turbine section 2b may result in a shutdown of the electricity production of part or all of the turbine. In the thermal power plant according to the invention, for example in the particular case of waste incineration and the preferred embodiment, the steam parameters of the main circuit and the pressure and temperature level of the secondary circuit make it possible to adjust the vacuum setpoint of the turbine exhaust, for example by means of a regulation based on the temperature measurement of the working fluid at the outlet of the reheating module 8, in order to avoid the excessive condensation levels mentioned above. It may therefore be possible, in a thermal power plant according to the invention, to avoid the shutdown of part or all of the turbine when there is no reheating.

[0052] The present invention allows the reheating fluid in the secondary circuit 9 to be at a higher pressure level than the working fluid in the main circuit. As a result, most of the elements located in the boiler can be designed for a conventional pressure level, corresponding to the main pressure level, where appropriate the economizers 4, the tank 6, the evaporator surfaces, the evaporators, the superheaters 5, and only a small part of the exchange surface of the boiler, in particular the upstream heat exchanger 10, must be designed for a high pressure level corresponding to the secondary pressure level, which significantly reduces the investment costs compared to a high pressure boiler. This also makes it possible to maintain the temperature level of the walls of the boiler and therefore of the refractories at a conventional level, for example in the case of waste incineration between 21 OC and 290C.

[0053] The present invention is particularly suitable for waste-type fuel power plants. Indeed, this type of power plant does not usually include a reheater, because the corrosive fumes do not favor the use of reheaters located in the fumes. Some waste-type fuel power plants have therefore been built with high-pressure boilers whose high-pressure steam (from the main circuit) feeds the reheaters. This type of power plant is faced with higher investment costs (high pressure) and higher operating costs (more frequent unscheduled downtime, higher maintenance costs).

[0054] Although the above description is based on particular embodiments, it is in no way limiting of the scope of the invention, and modifications may be made, in particular by substitution of technical equivalents or by different combination of all or part of the characteristics developed above.

Claims

Claims

1. Thermal power plant for producing electricity or motive power comprising at least one boiler (1) using fuel or heat recovery, at least one turbine, at least one main circuit for circulating a working fluid, at least one tank (6) located in the boiler (1) on said main circuit, at least one reheating module (8) and at least one secondary circuit (9) in which a reheating fluid circulates, in which: - said main circuit comprises at least one initial section (3c) located in said at least one boiler (1), at least one first section (3a) making it possible to send working fluid from said at least one boiler (1) to a first set of at least one turbine section (2a), and a second section (3b) making it possible to send working fluid from said first set of at least one turbine section (2a) to a second set of at least one turbine section (2b), and - said reheating module (8) comprises at least one downstream heat exchanger (11) located at the level of the second section (3b) of the main circuit, characterized in that said secondary circuit (9) comprises at least one upstream heat exchanger (10) located in said boiler (1), the upstream heat exchanger (10) making it possible to transfer heat from the combustion or recovery fumes to the reheating fluid circulating in the secondary circuit (9), said reheating fluid circulating in said secondary circuit (9) between the upstream (10) and downstream (11) heat exchangers, said plant being designed so that the reheating fluid can be, at the outlet of the upstream heat exchanger (10), at the nominal load point, at a pressure level at least ten bars higher than the pressure level at the nominal load point of the working fluid in said tank (6).

2. Thermal power plant according to the preceding claim, in which said fuels comprise waste such as household waste, waste from economic activities, hazardous waste, biomass, sewage sludge or even medical waste.

3. Thermal power station according to one of the preceding claims, in which said secondary circuit (9) comprises at least one pump (12) configured to bring the pressure level of the reheating fluid, at the outlet of the upstream heat exchanger (10), to a level at least ten bars higher than the pressure level at the nominal load point of the working fluid in said tank (6).

4. Thermal power station according to one of the preceding claims, in which said secondary circuit (9) is supplied with reheating fluid by at least two separate sources, the pressure and / or temperature level of the two sources being different.

5. Thermal power station according to the preceding claim further comprising: - a first temperature sensor (17) on the second section of the main circuit (3b), downstream of the downstream heat exchanger (11), - a pressure sensor (18), located on the secondary circuit (9), - a second temperature sensor (19), located on the secondary circuit (9) between the upstream heat exchanger (10) and the downstream heat exchanger (11), and - a regulation system (16) connected to the first and second temperature (17, 19) and pressure (18) sensors, and to at least one regulation valve (15) of the flow rate of a source of reheating fluid of the secondary circuit.

6. Thermal power station according to one of the preceding claims comprising at least one economizer (4) located on the initial section (3c) of the main circuit, at least part of the supply of reheating fluid to the secondary circuit (9) coming from an outlet of said economizer (4) and / or from a condensate and feedwater circuit (7).

7. Thermal power station according to one of the preceding claims, comprising a tank (6) located in the boiler (1) and / or a condensate and feedwater circuit (7), said power station being configured so that the reheating fluid can be sent after the downstream heat exchanger (11), to said tank (6) located in the boiler (1) and / or to said condensate and feedwater circuit (7).

8. A method of producing electricity or motive power in a thermal power plant, comprising the following stages: - combustion of fuels or heat recovery in a boiler (1), - in said boiler (1), enthalpy increase of a working fluid in a main circuit, said main circuit comprising a tank (6), said working fluid being in said tank (6) at a main pressure level, and enthalpy increase of a reheating fluid in a secondary circuit (9), said secondary circuit (9) comprising at least one upstream heat exchanger (10) located in the boiler (1), the upstream heat exchanger (10) making it possible to transfer heat from the combustion or recovery fumes to the reheating fluid circulating in the secondary circuit (9), said reheating fluid being at a secondary pressure level at the outlet of said upstream heat exchanger (10), said secondary pressure level being at least ten bars higher than said main pressure level, - sending said working fluid into a first set of at least one turbine section (2a), - sending said working fluid from said first set of at least one turbine section (2a) to at least one downstream heat exchanger (11) of a reheating module (8), and sending said reheating fluid from the boiler (1) to said downstream heat exchanger (11), - heat transfer from said reheating fluid to said working fluid in said downstream heat exchanger (11), - sending said working fluid from said downstream heat exchanger (11) to a second set of at least one turbine section (2b).

9. A method of producing electricity or motive power according to the preceding claim, wherein said fuels comprise waste such as household waste, waste from economic activities, hazardous waste, biomass, sewage sludge or medical waste, said main pressure level being between 20 and 85 bars, and said secondary pressure level being greater than 70 bars.

10. Method for producing electricity or motive power according to one of claims 8 to 9, in which said reheating fluid circulating in said secondary circuit (9) between said upstream exchanger (10) and said downstream exchanger (11) is in the liquid state.

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