JPS5849685B2 - Power - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to thermodynamic power generation, and more particularly to a superheated steam cycle and a second or one topping seven cycle using another working medium that allows the inlet temperature to be higher than the steam. binary that has both
Concerning steam power plants.

In conventional power plants, the working medium is water.

However, with respect to the thermodynamic properties of water, increasing the superheat temperature is not expected to result in any real efficiency improvement.

Heat sources that are currently available, or will be available in the near future, can provide temperatures that significantly increase the theoretical efficiency of the cycle, but this theoretical efficiency cannot be achieved without water being used as the refrigerant. In these cases, this cannot be achieved because of the irreversible flow of heat that occurs in the supercritical cycle, among other things.

In particular, in contrast to light water, CO2 and graphite reactors, which occur only at moderate temperatures, nuclear reactors currently in use or still in design (among others, metal-cooled fast neutron reactors,
High temperature gas furnaces, liquid salt furnaces) can generate temperatures of 8500C or higher.

Similar considerations can be applied to planned oxygen torch boilers.

In the future, the combination of atomic nuclei will become another means of producing very high temperatures.

In all such cases, using a single cycle with steam as the working medium makes it impossible to obtain high temperature effects.

The use of binary cycles has already been proposed.

Specifically, a topping mercury cycle was added to the low pressure steam cycle.

The mercury has the effect of being liquid at ambient temperature and has a low saturated vapor pressure.

On the other hand, it has drawbacks, among others, in terms of its cost and toxicity.

A dual cycle of potassium and water has also been proposed.

Unfortunately, potassium has significant drawbacks.

That is, it is susceptible to corrosion. It also requires reverse steam cycles associated with significant irreversibility.

Additionally, it requires very low absolute turbine exhaust pressures that are difficult to maintain at normal turbine exhaust temperatures.

Another conventional dual steam power plant (David R
．． U.S. Patent No. 3,218,802 to Mr. Saul)
has a boiling sulfur reactor.

Evaporated sulfur expands in the turbine, flows through a steam superheater heat exchanger, and condenses in a heat sink.

The condensed sulfur is then returned to the reactor.

The sulfur used as the working fluid in the topping cycle is sent to the turbine as saturated steam, thereby reducing the irreversible flow of heat.

Due to the special thermodynamic properties of sulfur, its steam is superheated at the exhaust of the turbine and irreversible phenomena in the steam heat exchanger are consequently reduced.

The temperatures and pressures at the exhaust of a sulfur steam turbine are consistent with today's technology.

Finally, sulfur is less reactive than potassium, much cheaper and less toxic than mercury.

On the other hand, sulfur has a negative effect on nickel at the temperatures in the totting cycle and therefore corrodes these austenitic steels with a high nickel content, and structural members that come into contact with sulfur are not made of such steels.

However, Or and Mo alloy steel has poor resistance to creep at temperatures above 550°C.

Even if the surface of Or, Mn, or Mo alloy ferrite steel is coated, the temperature is higher than 700°C (even this temperature is insufficient).

) have long-term resistance to creep, but they are not suitable for use in the manufacture of replacement tubes to accommodate pressure differentials of more than 20 par.

Simply put, US Pat. No. 3,218,802 specifically does not provide instructions to those skilled in the art on how to design a plant using excavated tinder.

Finally, the neutronic and thermal properties of sulfur make the development of boiling sulfur power reactors at least dubious.

It is, therefore, an object of the present invention, among other things, to improve upon conventional dual cycle thermodynamic power generation devices.

Therefore, the present invention provides that a heat source is used to evaporate sulfur, which expands in a turbine and is condensed into its vapor phase by heat exchange with water before it returns to the heat source. expands in a turbine with a condenser, from where the water returns to the heat exchanger where its heat is transferred from the first fluid to the sulfur at a pressure substantially equal to the pressure of the vaporized sulfur.

The thermodynamic power generation plant of the present invention includes a heat source, a sulfur first loop that receives heat from the heat source for converting the sulfur into saturated steam, and a sulfur first loop that receives the saturated steam and converts a portion of the heat of the sulfur into mechanical energy. an expansion turbine, a heat exchanger through which the sulfur is returned in liquid form, and a heat exchanger through which water and steam flow, the heat exchanger being located downstream of the heat exchanger and expanding the steam; and a second loop having a device for condensing the water and a device for returning the water to the heat exchange device, the heat source further including a substantially isobaric heat exchange device.

A steam cycle typically involves evaporation and superheating in the heat exchanger, then reheating in the exchanger, and steam draining.

Sulfur steam cycles also use reheating or draining or both to reduce irreversible heat flux.

Along with the temperature of the heat source that heats the sulfur to 750-800°C,
Due to the very special properties of sulfur, the following continuum occurs:

Saturated steam at a pressure of about 25 to 30 bar is introduced into a steam turbine resulting in an isentropic expansion of the sulfur vapor and, at the outlet of the turbine, the superheated sulfur vapor superheats and reheats the steam. can be used.

The desuperheated sulfur vapor is also used to evaporate the second cycle steam.

Rankine cycle efficiencies of 65% are therefore possible, and that figure gives a total efficiency of the order of 60% in terms of boiler organic efficiency.

The nature of the heat exchanger used here depends on the nature of the heat source.

In the case of a nuclear reactor, the reactor coolant and sulfur flow through an exchanger.

An interesting property here is that sulfur, which is virtually inert to sodium and water, provides extra safety in reactors cooled with liquid sodium by acting as a barrier between the sodium and water. .

In the case of boilers, air must be introduced at equilibrium pressure,
This is very easily achieved due to the low sulfur vapor pressure (20-25 bar).

Also, to withstand air pressure, the boiler enclosure is constructed of prestressed concrete, thus eliminating much of the framework required for conventional boilers and to which the exchange tubes are fixed. Creep problems in the framework steel can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more clearly understood from the following detailed description of an apparatus, which is given by way of example only and without limitation, and is explained in conjunction with the accompanying drawings in which: FIG.

Referring now to FIG. 1, a fast neutron nuclear reactor cooled by a liquid alkali metal, usually sodium, at near atmospheric pressure is shown, the reactor 10 having a fuel element can rupture. It is connected to a heat exchanger 11 for transferring heat between a first refrigerant of the nuclear reactor, which in case of contamination with radioactive products, and a second refrigerant, which is liquid sodium.

The reactor 10 and heat exchanger 11 are enclosed within a secure enclosure 12.

The first sodium refrigerant has, for example, an exit temperature of 850'C and an absolute pressure of approximately 1 bar.

The second sodium refrigerant has, for example, an outlet temperature of 820° C. and an absolute pressure of 25 bar maintained by the nitrogen atmosphere pressurization device 13, which also serves as an expansion vessel.

The system integrated by nuclear reactor 10 and heat exchanger 11 forms a heat source.

The second refrigerant loop includes a heat exchanger 14 for sodium and sulfur, and a heat exchanger 11 for the sodium that has left the heat exchanger 14.
Pump 15 is returned to the inlet of the pump.

As mentioned above, the heat exchanger chinabs in contact with sulfur cannot be made of nickel-containing alloys.

This is because nickel corrodes and continuously creates nickel sulfate.

As a result, nickel steel, which is commonly used to withstand high pressures at temperatures above 550° C., should not be used for the tubes of heat exchanger 14.

However, the intermediate heat exchanger 11, which must be provided anyway, acts as a pressure compensation device, so that in the case of the schematic diagram shown in FIG. 1 the pressure is significantly lower.

The heat exchanger 11, which is in contact only with sodium, is made of austenite a with a high nickel content and is devised to withstand creep at the same pressure as that of the heat exchanger tubes through which sulfur flows.

As a result, heat exchanger 14 is an isobaric device, e.g.
Made of ferritic steel containing chromium, molybdenum and mankan.

Furthermore, the steel can be surface treated by chromium bonding or chromium coating or other well known methods to increase its resistance to sulfur corrosion.

Downstream of the heat exchanger 14, the sulfur loop has a multi-stage sulfur steam turbine 16.

These turbine parts, which come into contact with the high temperature, high pressure sulfur vapor, must be made of materials that resist corrosion and creep, but in contrast to the heat exchangers, they are made of expensive alloys because the volumes used are quite different. It can be used.

In particular, movable fins or ribs made of titanium or tantalum alloys can also be used for high pressure stages.

The sulfur vapor leaving the turbine is sent to the sulfur and water exchanger 17 where the sulfur is liquefied for return to the sulfur and sodium exchanger 14.

The loop is typically such that the sulfur vapor is saturated at the inlet to the turbine 16 and superheated at the outlet, and in the exchanger 17, which acts as a steam generator, the steam is superheated by superheated sulfur and the water evaporates by condensation of the sulfur. It is designed as a

One method is to have a temperature of 750° C. and a pressure of 25 bar absolute at the inlet of the turbine and a temperature of 475° C. and a pressure of 0.16 bar absolute at the outlet of the turbine.

The second loop is similar to that of a conventional supracritical steam plant, with the following differences:

That is, for the steam generator and the superheater feed, it has a multistage turbine 18 with a condenser 19 from which condensed water is returned to the exchanger 1γ by a feed pump 20.

These turbines drive one or several alternators 21, the number depending on the number of shaft lines.

For example, the temperature and pressure of the turbine population are each 530
°C and 110 bar (after passing through the bleed fed superheater) and the temperature at the condenser is 25 °C.

The device so produced has a very high Rankine efficiency of more than 65% for the main cost compared to that of a single-cycle power plant above critical u with a reactor with an output temperature of more than 750 °C. issue.

Additionally, adding a sulfur loop to separate sodium and water increases safety.

The apparatus of FIG. 2, in which like parts are designated by the same reference numerals as in FIG. 1, uses as a heat source the combustion gases of excavation fuels, such as coal, which tend to replace oil products.

The water loop is similar to the loop in Figure 1 and does not need to be explained again.

The upstream, ie one topping "loop" consists of a combustion gas and sulfur exchange tube bundle 14, which serves as a sulfur vapor generator and must not be subjected to substantial pressure differences.

However, the sulfur vapor flowing along the exchange tube must be slightly above atmospheric pressure to avoid air intrusion when the tube breaks.

Pressurized air is delivered to boiler 22 at a flow rate corresponding to a slight excess of air over stoichiometric combustion conditions.

The hot combustion gases leaving the boiler 22 circulate through one to several gas turbines before it enters the heat exchanger 25 for heating the combustion air.

Each gas turbine in which the gas is expanded and cooled, for example from 750'C to 200°C, allows the size of the air heater 25 to be significantly reduced, from which the gas is cooled at a temperature of, for example, 130°C. Flows into storage.

For example, air taken from the atmosphere at a temperature of 15 DEG C. is compressed by a multistage interstage cooled compressor 24 driven by a gas turbine 23.

The excess power of the gas turbine is used to drive an alternator 26 connected to the turbine shaft.

The air delivered by the compressor 24 at a pressure of, for example, 24 bar, which is necessary for pressure equalization in the exchanger 14, is heated by the air heater 25 to a temperature of approximately 180°C.

The very simple diagrams in Figures 1 and 2 show only the main parts of the installation, omitting all the auxiliary parts which serve, in particular, to reduce the irreversible flow of heat and increase the overall efficiency of the plant. .

FIG. 3 is a more detailed drawing of the plant which corresponds to the simple schematic diagram of FIG.

In FIG. 3, as in FIG. 2, many of the illustrated structural elements actually include a plurality of separate, interrelated units operating in parallel.

For simplicity, the same parts in Figures 2 and 3 have the same symbols, and the air and combustion gas raw circuit, the water main circuit, and the sulfur king circuit are indicated by double lines, dotted lines, and thin lines, respectively. It is shown in

Circuits with small amounts of flow, especially bleeds, are shown in dashed lines.

Starting from the vessel 27 of the boiler 22, the sulfur circuit consists of a high temperature, high pressure turbine 28 which discharges without reheating to an intermediate temperature double case turbine 29.

The circuit discharges to a sulfur and water exchanger 14, similar in construction to a conventional 1 Benson or 1 Sulzer boiler.

In the heat exchanger 14, the superheated sulfur vapor leaving the turbine first flows through a bundle 30 of water superheating tubes.

The desuperheated sulfur then flows to a water evaporation tube bundle 31;
It then leaves the exchanger 14 in fluid form.

Before returning to the boiler, the condensed sulfur is sent by a withdrawal pump 70 to cascade heaters 32-35 where the sulfur is removed in a manner to be described below.

Forced circulation of the sulfur is provided by feed pumps connected to each heater, with the last pump 36 transporting sulfur to the boiler 2.
Return to No. 2 piping.

In one embodiment of the invention, the sulfur loop is prepared at temperature and pressure as follows.

At the outlet of the replacement tube of boiler 22 24 bar, 7
50°C (saturated steam).

At the outlet of the intermediate temperature turbine 29, the pressure is such that the sulfur is superheated and the temperature is 475°C.

At the outlet of exchanger 14 a temperature of 34° C., corresponding to a saturation pressure of 0.16 bar.

At the inlet of the replacement tube of boiler 22, the temperature is approximately 700°C.

The superheated steam sent by the superheated tubing 30 of the exchanger 14 is sent to the exchange tubing 37 of the superheater 38 .
is fed the exhaust from an intermediate pressure sulfur steam turbine 29.

The sulfur vapor that has circulated through the superheater 38 reaches the mixing heater 32 at a temperature of, for example, about 570°C.

The steam leaving the tube 37 is superheated again in the tube 39 of the second superheater 40, which receives the exhaust from the hot sulfur steam turbine 28.

For example, the sulfur vapor leaving the superheater 40 at a temperature of 620° C. is sent to the second preheater 33.

In this case, the last two preheaters 34, 35 are fed directly with the exhaust from the hot sulfur steam turbine 28, for example at temperatures of 670° C. and 720° C., respectively.

For example, at a temperature of 530 °C and a pressure of 110 bar, the tube 39
The superheated steam leaving the reheating tube 4 of the exchanger 14
The steam reaches a high pressure steam turbine 41 which discharges the steam to a high temperature.

Tubing 42 may be the same as tubing 30.

The reheated steam passes through superheater 38 . before entering intermediate pressure steam turbine 43 . 40 (same as tubes 37, 39) where it is distributed between low pressure double case steam turbines 44 and 45.

These steam turbines 44, 45 are connected to a conventional steam condenser 46, which is designated 7
It is cooled by the raw water coming out of the inlet 72 at point 1.

The condenser is, for example, the feed pump 47 with 0.
It is devised to return the water at a temperature of 25° C. with a saturation pressure of 0.035 bar.

In order to reduce the irreversible flow of heat, the water leaving the condenser is passed through a cascade of heaters 48 to 52 fed with the effluent, arranged in a steam turbine, before being returned to the evaporation tube 31 of the exchanger 14. heated.

In the exemplary diagram shown, heater 48 may include, for example, five
The exhaust from the turbine 45 is fed at a temperature of 8°C.

The heater 49 is supplied with the exhaust from the turbine 44 at a temperature of, for example, 180°C.

The heater 50 is supplied with the exhaust from the intermediate pressure turbine 43 at a temperature of, for example, 350°C.

For example, the heaters 51 and 52 each have a temperature of 300°C.
The exhaust from the high pressure steam turbine 41 is supplied at a temperature of 420° C. and 420° C.

The feed pump 53 returns water to the evaporation tube 31 of the exchanger 14 at a temperature of, for example, 262°C.

As previously mentioned, austenitic steel, the only economical material that can withstand creep at high temperatures, cannot be used for tubes in contact with sulfur, and the replacement tube must be operated at equilibrium pressure. Must be.

Therefore, a pressurized combustion chamber boiler is used, which is operated such that the combustion gas at the output of the boiler 22 is at a temperature and pressure of the same order of magnitude as for sulfur vapor.

In the embodiment shown in FIG. 3, a compressor or blower 24 compresses atmospheric air introduced at 54 to the appropriate pressure.

The compressor 24 is typically multi-stage with cooling between stages.

For simplicity, the compressor 24 in FIG. 3 is shown connected to a single pipe 55 connected to an exchanger 56 cooled by raw water.

The compressed air leaving the compressor 24 is heated by the exhaust gas in a heat exchanger 25, which will be explained in more detail below.

Air, for example at a temperature of 180° C. and a pressure of 24 bar, is sent to the furnace of the boiler 22.

The combustion of the excavated pimps introduced at 57 generates combustion gases, which first heat the gas and sulfur exchange tubes and then rise to a temperature of e.g. 750'C and 23°C.
It flows through the duct 58 at a pressure of Bar.

The gas is then expanded in a plurality of multi-stage gas turbines 23 arranged to flow in parallel.

Only one turbine is shown, which drives a compressor 24 and an alternator 26 (same as alternator 21).

The gas is then exhausted to the atmosphere through exchanger 25.

In view of the required sulfur pressure and intake air pressure, the air temperature varies over a wide range, e.g. from 25° to 100°C, so that the exchanger provides substantial interstage cooling. It is necessary to provide a compressor 24 having a

On the other hand, the gas turbine 23 does not have the most expensive part of a conventional gas turbine plant, namely a combustion chamber.

This is because boiler 22 works in its place.

Using boiler 22 as a combustion chamber for gas turbine 23 also reduces the significant amount of air normally required to maintain the turbine inlet temperature at an industrially acceptable temperature.

Because extra air is fed into the sulfur steam boiler 22, it can be much smaller than a conventional water boiler.

This reduction in size is particularly advantageous in view of the current trend of increasing unit capacity.

In fact, the boiler 22 can be a prestressed concrete vessel even in a 1200 MW plant using currently well-developed and relatively low cost technology.

In this case, much of the tube support structure required in conventional boilers and accounting for a large portion of the cost can be omitted.

FIG. 6 shows one possible construction of the walls of such a boiler, a prestressed concrete pressure vessel 73 comprising an internal metal skin 74 of the vessel and a sealing sheet metal member lined with a thermally insulating layer 77. 76, the temperature is maintained consistent with maintaining its mechanical strength.

Thermal insulator 77 is separated from a thick insulating layer 79, which can withstand high temperatures and is made of the type currently used in nuclear reactors, by an annular space 7B wide enough to be reached for inspection. , it may not be able to withstand high temperatures.

The inner surface of layer 79 supports heat exchange tubes 80 positioned adjacent to each other through which sulfur flows.

Additionally, the connection between the gas turbine 23 and the air compressor 24 uses the expansion energy of the combustion gas in the turbine 23, thereby significantly reducing the weight of the air and combustion gas exchanger 25 compared to conventional boilers. make it possible to

The bulk of such exchangers is to be avoided in boilers not supplied with compressed air.

If the plant in Figure 3 is a boiler supplied with air,
It can also be supplemented with a special heater, which uses the existing sulfur steam drain on the turbine.

The usefulness of this solution is that it does not operate under normal conditions;
Up to about 17% above its rated load by adding special gas turbines, such as those used at peak loads and in emergencies, to absorb the excess energy of the combustion gases.
It is not possible to improve overall efficiency to the extent that forcing the plant to have a temporary overload capacity that is too high.

In principle, adding a special turbine does not involve any additional major costs.

This is because gas turbines are one of the plant components that are prone to failures, and the number of turbines installed in them is always greater than is actually required.For example, five turbines can be installed instead of four. is equipped.

In the plant of FIG. 3, special heaters can be provided, for example, at the positions indicated by frames 60, 61.

Exchanger 62 shown in FIG. 4 and forming system 60
．． 63 is placed at the outlet of the exchanger 25 and is fed by induction from a steam drain to feed water heaters 51, 52 respectively.

Air leaving heater 63 is passed through a series of extra air heaters 6
5 to 68, and those heaters have superheaters 38.4
0 and mixer superheaters 34-35 (FIG. 5).

Sulfur and oxygen have such a chemical affinity that there is a danger of fire if air and sulfur come into contact at temperatures above 250°C, so the flow of sulfur and the flow of air are It is highly desirable to interpose a flow of barrier fluid, such as steam, which is inert to sulfur.

One option is to use a double-walled exchange tube that allows steam to flow through the gap between the walls at a lower pressure than the sulfur and air; in the event of a leak, the steam will flow along the sulfur , or air, so the presence of sulfur or air is immediately detected.

The walls in contact with the air should withstand compressive stresses resulting from pressure differences, and this is easily accomplished since high strength austenitic steel can be used.

The walls in contact with the sulfur are coated with a protective layer and made of ferritic steel thin enough to be deformable, so that the pressure difference between the sulfur and the steam is exerted on the outer wall and the expansion coefficients of these materials are different. Therefore, the difference in expansion can be followed.

When the deformation plant shown in Figures 4 and 5 is in normal operating conditions, heaters 62, 63 and 65-68 are used.

As an example, in order to incorporate the energy of combustion gas,
Assume that you need several gas turbines.

In order to handle short-term peaks of up to 17% of the rated load,
The air heater feed is cut, resulting in a corresponding reduction in steam and sulfur vapor bleed flows.

At the same time, the flow rate of boiler fuel is increased, for example by the use of extra fuel injectors, and the flow rate of boiler air is increased by the use of a compressor connected to a gas turbine, which is normally retained in case of emergency operations. .

With the extra combustion gas distributed, an emergency gas turbine can also be used and the same output is sent to the alternator 26.

This overload does not result in an increased heat exchange in the boiler 22 between the combustion gases and sulfur, the flow rate being kept constant at the inlet of the turbine 28.

This provides an economical way to devise a plant capable of providing significant overloads but very low main costs, the extra gas turbine having to be equipped anyway as a safety device.

If necessary, the cost of an extra combustion injector is a small fraction of the cost of the plant.

The air and steam heaters 62, 63 and the air and sulfur heaters 65-68 have only a small exchange area and their air pressure is much higher than atmospheric pressure, so the exchange coefficient is also high.

Another advantage of the plant is that the sulfur circuit is easily and quickly heated from ambient temperature.

The plant also has auxiliary equipment (not shown) known to the average designer, especially for cold start.

All parts to which sulfur freezes must have electrically heated lines or cords in accordance with current technology.

This is because it is used in nuclear reactors that are cooled with liquid alkali metals.

Continuous sulfur and water purification equipment is also required to remove impurities removed by the equipment from the stream.

Next, embodiments of the present invention will be additionally described.

In addition to the gas turbine required for normal operation, there is an emergency gas turbine driving the compressor, said additional air heating device being activated when the emergency gas turbine is operated to increase the flow rate of fuel supplied to the boiler. 3. A dual cycle thermodynamic power plant according to claim 2, wherein the dual cycle thermodynamic power plant is arranged such that it is not operated at the same time when the power plant temporarily reaches a peak load.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a power plant with a dual cycle of sulfur and water, where the heat source is a nuclear reactor cooled with liquid sodium, and Figure 2 is a schematic diagram of a power plant with a dual cycle of sulfur and water, where the heat source is a boiler with excavated fuel. FIG. 3 is a detailed view of the apparatus corresponding to the schematic diagram of FIG. 2, and FIG.
FIG. 5 is a detailed view of two parts of the device of FIG. 3 with an additional air heater, and FIG. 6 is a schematic representation of a possible construction of the boiler wall of the device shown in FIG. 10: Fast neutron reactor, 11: Heat exchanger, 12: Safety enclosure for reactor and heat exchanger, 13 Pressurizing device for dinitrogen and atmospheric air, 14: Sodium and sulfur heat exchanger, 15: Pump , 16: Sulfur steam turbine, 17: Sulfur and water exchanger,
18: Multi-stage turbine, 19: Condenser, 20.4
7, 53: Feed pump, 21: AC generator, 22:
boiler, 23: gas turbine, 24: compressor, 25: air heater, 27: container, 28: high temperature high pressure turbine, 29: intermediate temperature double case turbine, 30: water superheating tube bundle, 31: water evaporating tube bundle, 32-35:
Cascade heater, 36 pipes, 37: Replacement tube, 38: Superheater, 39: Second superheater tube, 4
0: Second superheater, 41: High pressure steam turbine, 42 Two reheating tubes, 44, 45: Low pressure double case steam turbine, 48-52: Cascade heater, 73:
Prestressed concrete pressure vessel, 80: heat exchange tube.

Claims (1)

[Scope of Claims] 1. A heat source, which receives sulfur in a substantially liquid state, performs heat exchange between the heat source and the sulfur for converting the sulfur into saturated vapor, and is non-reactive with respect to sulfur. a main heat exchanger having pipes for sulfur, which are relatively soft and have a relatively low resistance to creep; and at least one sulfur turbine; a first closed loop for sulfur circulation having a first heat exchange device for condensing water; said first heat exchange device in which water is evaporated and superheated;
a second loop for water and steam circulation comprising a heat engine device for expanding and condensing steam and a device for returning condensed water to the first heat exchange device; , a dual cycle thermodynamic power plant comprising a main heat exchange fluid and a circulation device for circulating the sulfur and the main heat exchange fluid at substantially equal pressures within the main heat exchange device. 2. A heat source and a heat exchanger between the heat source and the sulfur for receiving sulfur in a substantially liquid state and converting the sulfur into saturated vapor, and wherein the surface in contact with the sulfur is non-reactive with respect to the sulfur. at least one sulfur expansion turbine, and condensing the sulfur exhausted by the at least one sulfur turbine; a closed first/L-pipe for circulating sulfur, having a first heat exchange device for circulating sulfur;
a first heat exchange device in which the water is evaporated and superheated; a heat engine device to expand and condense the steam; and a device to return the condensed water to the first heat exchange device. a second loop for circulation, the heat source including a main heat exchange fluid and a circulation device for circulating the sulfur and main fluid at a pressure substantially equal to the pressure in the main heat exchange device; The heat source is an excavated fire pit with heat exchange tubing through which sulfur flows;
a device for supplying combustion support air to the boiler at a pressure such that the discharge pressure of the combustion gases is at least substantially equal to the pressure of the discharged sulfur vapor, said combustion support air supply device following an air heater; an air compressor and a gas turbine device that receives combustion gas emitted from the boiler and drives the air compressor, the combustion gas leaving the boiler being expanded in the gas turbine device and removed from the turbine. exhaust gas is delivered to the air heater as its heating fluid, and the combustion support air supply device is supplied with combustion gas on an air passage and heated by the exhaust gas from the heat engine device. A dual cycle thermodynamic power plant including an additional heating device located downstream of the boiler to heat the air delivered to the boiler.