EP2136040A2 - Low temperature power plant and method for operating a thermodynamic cycle - Google Patents

Abstract

The machine has an organic Rankine cycle (20) comprising an expansion machine and a heat exchanger (24) for feeding heat flow from a low temperature mass flow (1) into the cycle. A thermal transformer (21) is in heat flow connection with the cycle at a cold side (23) of the transformer, which is downstream to the expansion machine. The thermal transformer stays in a heat connection with the low temperature mass flow or the cycle at a hot side (22) of the transformer. Another organic Rankine cycle is arranged sequentially to the organic Rankine cycle (20). An independent claim is also included for a method for operating of a thermodynamic loop in a low temperature power plant.

Description

The invention relates to a device for operating a thermodynamic cycle, in particular a low-temperature power plant, and an associated method, wherein a low-temperature mass flow to a circulating in a first cycle working fluid at a Ausgangstemperaturniveau a first heat flow and wherein after an expansion of the working fluid in an expansion machine the Working fluid is withdrawn at a lower than the Ausgangstemperaturniveau expansion temperature level, in particular in a cooling device, a second heat flow.

Such thermodynamic cycles are used in particular in low-temperature power plants to gain energy from a low-temperature mass flow, for example by means of a turbine, which serves as an expansion machine. Low-temperature power plants find, for example, in geothermal, solar thermal, energy from biomass, in the generation of energy from waste heat, which, for example, in digestion or fermentation processes such. arises in a landfill, or the like. Application. In the course of saving fossil fuels and in the pursuit of a complete abandonment of such fossil fuels find such processes steadily growing interest.

Due to the smaller in comparison to a high temperature power plant temperature difference in the operation of the thermodynamic cycle, an efficiency of a low temperature power plant is naturally always significantly lower than in a high temperature power plant. Especially since the temperature of a low-temperature mass flow is predetermined on the basis of the conditions of, for example, a geothermal heat source or a waste heat-conducting process, There are efforts to improve the energy yield of a low-temperature power plant through optimization measures.

The object of the present invention is to improve an energy yield during operation of a low-temperature power plant with, in particular, only minor changes in the apparatus of existing thermodynamic cycles.

This object is achieved by a thermodynamic machine, in particular a low-temperature power plant, with the features of claim 1 and by a method for operating a thermodynamic cycle, in particular a low-temperature power plant, with the features of claim 7. Advantageous embodiments and further developments are specified in the respective dependent claims.

In a thermodynamic machine according to the invention, in particular a low-temperature power plant, with at least one first circuit for circulating a working fluid, the first circuit at least one expansion machine and at least a first heat exchanger for feeding a first heat flow from a low-temperature mass flow in the first circuit, wherein at least one Heat exchanger with its colder side between the expansion machine and the cooling device or in the cooling device, which is in particular a condenser, is provided in heat flow communication with the circuit and with its warmer side with the low-temperature mass flow or the first circuit (upstream of the expansion machine) in Heat flow connection is. As a heat flow connection, the heat transformer, for example, on its colder side and its warmer side each have a heat exchanger.

A heat transformer is a device or a component that from a mass flow with a first temperature level, a smaller mass flow generated with a relation to the first temperature level higher temperature level and another smaller mass flow with respect to the first temperature level lower temperature level. As a colder side of the heat transformer, the side is called the first temperature level, and the warmer side of the heat transformer, the side is referred to the higher than the first temperature level temperature level. For supplying a heat flow into the heat transformer (on its colder side) and / or for delivering a heat flow from the heat transformer (on its warmer side) may each be provided heat exchangers, which may be in communication with the circuit or the low-temperature mass flow.

Preferably, this makes it possible to increase the efficiency or heat throughput of a thermodynamic cycle, in particular of a low-temperature power plant, by, for example, bringing the mass flow supplied to the expansion machine to a higher temperature level and / or increasing this mass flow. In particular, existing low-temperature cycles can be converted by using a heat transformer with little effort.

As a low-temperature mass flow, for example, a stream of water from a geothermal brine is used. If the temperature of the geothermal brine is sufficient, the low-temperature mass flow may also be in the form of steam. However, instead of water, other fluids may also be used for the low-temperature mass flow. As an alternative to a geothermal brine, the low-temperature mass flow can also be brought to its operating temperatures by means of solar thermal energy, waste heat from a biomass process, waste heat from another process or the like.

In particular, the working fluid is selected to be in a vaporized form at a temperature of the low temperature mass flow, whereas in a lower temperature level of the circuit, it is in a liquid phase. Depending on the temperature used for this purpose according to common refrigerants are used such as pentane, butane, other hydrocarbons or the like. In a simple circuit, for example, the working fluid is vaporized in a first stage in a heat exchanger by the low-temperature mass flow, in a second stage in an expansion machine acting turbine expands and then condensed again to be heated again by the low-temperature mass flow in the heat exchanger.

For example, the circuit may be operated as an Organic Rankine cycle, ORC. In this case, an ORC fluid, which z. As pentane, butane or other refrigerant is heated in a preheater, evaporated in a heated by the low-temperature mass flow evaporator, fed to a functioning as an expansion engine turbine and expanded there, and cooled in a condenser to be fed to the cycle again. Between turbine and condenser while a recuperator is provided, which serves to recover residual heat from the exhaust stream of the turbine. The amount of heat gained is used to feed the preheater. In a method according to the invention, a heat transformer is additionally provided which extracts a second heat flow from the working fluid after the turbine or the expansion machine and after the recuperator and before or in a cooling device, which is in particular a condenser, and pumps it to a higher pump Temperature level pumps and the circuit or the low temperature mass flow again leads.

Regarding the basics of an ORC process will be on the DE 692 18 206 T2 referenced, to which reference is made in the context of the disclosure is taken. Preferably, the use of an ORC cycle makes it possible to retrofit existing and existing systems based on this principle with little effort to improve the efficiency.

In another embodiment, the cycle can be operated as a Kalina cycle. The Kalina process works a bit similar to an ORC process, where the working fluid is first heated, evaporated, in the expansion machine, such as a turbine, is relaxed, condensed and then fed back to the heating. In contrast to an ORC process, the working fluid in the evaporator or desorber is split with a subsequent separator in a vapor phase and an aqueous phase, wherein the steam is passed through the expansion machine, while the liquid phase after a possible heat recovery via a throttle to the outlet pressure the expansion machine, in particular the turbine, is relaxed. Subsequently, both partial flows are reunited and flow back via an internal heat exchanger to the condenser or the absorber. After the condensation / absorption, the pressure is increased again, for example by means of a feed pump. Regarding the basics of an ORC process will be on the US 2004 0182084 A1 referenced, to which reference is made in its entirety in the context of the disclosure.

In addition to these embodiments, any other type of low-temperature power plant can be operated according to the invention.

In particular, a cooling device is provided on the downstream side of the expansion machine, for example a condenser or the like, wherein the second heat flow is withdrawn from the low-temperature mass flow before or in the cooling device.

As a heat transformer, for example, a system with at least two expeller Adsorbem is used, as described in the patent DE 34 08 192 C2 is described, which is fully incorporated by reference in the disclosure. Alternatively, a force-heat engine may be used with an at least substantially adiabatic compression step of a working fluid.

According to a development, a second circuit, in particular an ORC circuit, with a second heat transformer, which is arranged in the same way as the first heat transformer, arranged sequentially to the first circuit, wherein the first and second heat transformer each with its warm side with the low-temperature Mass flow between the first and second circuit are in heat flow connection. For this purpose, the heat transformers are provided for example at their ends with heat exchangers, which are on the warmer side of the heat transformer on the one hand with the low-temperature mass flow in heat flow connection and on the colder side of the heat transformers on the other hand with the respective circuit in heat flow connection. The temperature of the warmer side of the second heat transformer is preferably lower than the temperature of the warmer side of the first heat transformer. Preferably, the heat exchangers of the heat transformers are arranged in the low-temperature mass flow, that first the heat of the second heat transformer is discharged to the low-temperature mass flow and then the heat of the second heat transformer. As a result, preferably takes place a stepped increase in temperature of the low-temperature mass flow upstream of the second circuit.

In a further embodiment, a second circuit is provided, which is fed from a branch stream from the low-temperature mass flow downstream of the first circuit, wherein the first heat transformer with its warmer end is in heat flow connection with the branch stream upstream of the second circuit and wherein a downstream recycling of the branch stream downstream of the second circuit is provided in the low-temperature mass flow. For example, an existing heat cycle, in particular according to the ORC principle, thereby be improved in its energy yield, that this is coupled to a second heat cycle, in particular according to the ORC principle, only one feed line from one output of the first circuit to the input of the second Circuit must be placed and an outflow line from the second circuit must be placed back to the first downstream line, in addition to the principle of ordinary heat cycles, for example, the ORC principle, a heat transformer is used such that its warm end with the input line of the second heat cycle is in heat flow connection. Preferably, this can improve a current efficiency of about 15%.

In order to realize a closed low-temperature mass flow circuit, a second circuit may be provided which has a downstream feedback to its input, which is in heat flow communication with the warmer end of the first heat transformer, the first and the second circuit are fluidically separated in particular completely and are only in heat flow connection with each other via the first heat transformer.

In a further development, at least one return line for returning a partial flow from the low-temperature mass flow downstream of the first circuit is provided, wherein the warm side of the first heat transformer is in heat flow connection with this partial flow. As a result, preferably the low-temperature mass flow upstream of the first circuit is increased. In particular, the heat transformer and the return line such that the recirculated partial flow can be heated to exactly the starting temperature level, ie the first temperature, of the low-temperature mass flow.

In another embodiment, the warm side of the first heat transformer in a section between an evaporator and the expansion machine with the first circuit in heat flow connection. In particular, a corresponding heat exchanger is provided in this section, which is fed by the warm side of the first heat transformer. Thus, a temperature of the working fluid is preferably increased immediately before entering the expansion machine and thus improves an energy yield during expansion.

The invention also relates to a method for operating a thermodynamic cycle, in particular a low-temperature power plant, in particular according to one of the above-described embodiments, in which circulates a working fluid, which is supplied by a low-temperature mass flow at a Ausgangstemperaturniveau a first heat flow, wherein after expansion of the working fluid in an expansion machine with delivery of mechanical energy to the working fluid at a second, lower than the Ausgangstemperaturniveau lower expansion temperature level, especially before entering a cooling device, a second heat flow is withdrawn, which in at least one heat transformer to a pump temperature level which is higher than or equal to Output temperature level is pumped and the low-temperature mass flow and / or the first circuit is at least partially recycled. In other words, the second heat flow is withdrawn downstream of the expansion machine and after pumping to the pump temperature level, for example, immediately before (upstream) of the expansion machine fed back into the cycle or in the low-temperature mass flow.

Advantageously, this allows an increase in efficiency or heat throughput of the thermodynamic cycle, in particular a low-temperature power plant.

The starting temperature level, which corresponds to the temperature level of the low-temperature mass flow, is for example at temperatures between an ambient outside temperature and about 200 ° C, for example 120 ° C. The pump temperature level is preferably at least as high, but advantageously higher than the initial temperature level.

In order to pump the second heat flow to the higher pump temperature level, a temperature of a heated by the second heat flow heat transformer fluid is raised by at least two expeller adsorbents on or above the higher pump temperature level.

In this case, for example, the heat transformer fluid is expelled at a relatively low first pressure from a solid adsorbent, the gaseous Wärmetransformatorfluid formed during expulsion at a relatively low first temperature with the release of heat in a liquid phase and in a liquid phase present Wärmeransformatorfluid at a mean second temperature and at a relatively higher pressure with heat absorption in the gas phase, the gaseous working fluid adsorbed with release of useful heat at a relatively high third temperature in a solid adsorbent and the process by cyclically expelling and adsorbing working fluid in the adsorbent or parts thereof, wherein at least two, at different temperatures and pressures expeller adsorber means of heat exchange devices heat from the heat transfer fluid rich to the heat transformer fluid poorer Exchanging exchanger adsorber, which is then exchanged between the heat exchanger exchange between these expeller adsorbers heat exchanger fluid between these expulsion adsorbent, which is expelled from the heat-transforming fluid-rich adsorbent under heat absorption and adsorbed in the heat-transforming fluid-poor adsorbent with evolution of heat.

In another variant, a heated by the second heat flow heat transformer fluid is at least substantially adiabatically compressed and thereby heated to or above the pump temperature level to pump the second heat flow to the pump temperature level. Depending on the temperature range, a suitable refrigerant such as, for example, pentane, butane or another suitable hydrocarbon compound is used as the heat transformer fluid.

According to one embodiment, it is provided that a temperature of the low-temperature mass flow and / or a temperature of the working fluid in the first circuit is increased by the second heat flow raised to the pump temperature level. This preferably allows an increase in the efficiency of the thermodynamic cycle, in particular low-temperature power plant. For this purpose, for example, the second heat flow is pumped to the higher pump temperature level, which is above the Ausgangstemperaturniveaus, the temperature of the low-temperature mass flow. In this way, the temperature of the low-temperature mass flow is increased. Similarly, an increase in the temperature of the working fluid at one point in the circuit may also be provided. Preferably, a maximum temperature of the working fluid is increased within the thermodynamic cycle.

Alternatively or additionally, it can be provided that the low-temperature mass flow is increased by partial recycling of a low-temperature mass flow effluent heated with the second heat flow. Preferably, the partially recirculated low-temperature mass flow effluent is pumped to the same temperature level as the incoming low-temperature mass flow. It goes without saying that the volume flow or mass flow delivered from, for example, a geothermal source does not change. By recycling, however, the mass flow or volume flow which passes through the circuit is increased.

For an operation of the circuit, various embodiments and procedures or arrangements may be provided. In a first proposed method, at least two circuits, in particular ORC circuits, are fed sequentially from the low-temperature mass flow, whereby a return of the second heat flows respectively pumped to the higher pump temperature level into the low-temperature mass flow between the first and the second circuit. This preferably allows a temperature increase of the low-temperature mass flow, which has passed the first circuit, in particular the ORC process, and an improved energy yield of the second ORC process.

In a further variant, at least two circuits, in particular ORC circuits, are provided, wherein a branch stream for supplying the second circuit is branched off from the low-temperature mass flow downstream of the first circuit, which downstream of the second circuit is reunited with the low-temperature mass flow downstream wherein the pumped to the higher pump temperature level second heat flow of the first circuit is supplied to the branch stream. This preferably makes it possible to improve an existing system by coupling a second thermodynamic circuit, in particular an ORC circuit.

According to a further development, at least two circuits, in particular two ORC circuits, provided, wherein the pumped to the pump temperature level second heat flow of the first circuit is fed to a downstream of the second circuit, which is supplied to the second circuit again as an influx second ORC circuit to be completely separated from the first ORC circuit except for a heat flow connection. The heat flow is transferred without replacing a mass flow between the circuits.

In a further embodiment, it is provided that a branch stream is branched off from the low-temperature mass flow downstream of the first circuit, which is heated by the second heat flow pumped to the higher pump temperature level and returned to the low-temperature mass flow upstream of the first circuit.

In particular, it is provided to dimension the branch flow so that its pump temperature level before returning corresponds to the output temperature level of the low-temperature mass flow. In this way, the low-temperature mass flow upstream of the first circuit is increased. Advantageously, this leads to a higher energy yield. At the same time, in particular, a low-temperature mass flow effluent is not increased despite the higher low-temperature mass flow passing through the first circuit.

In another embodiment, the second heat flow is withdrawn downstream of the expander and fed after pumping to the higher pump temperature level, especially immediately before the expansion machine back into the first cycle. Preferably, this is a temperature in a mass flow of the working fluid in the first cycle between an evaporator and the expansion machine increased. In particular, the heat potential in this mass flow is increased.

In the following the invention will be explained by way of example with reference to the drawing. However, the invention is not limited to the feature combinations shown there. Rather, in each case in the figures and in the description illustrated features within the scope of the claims for further developments can be combined.

Figur 1

den Aufbau eines ORC-Zyklus gemäß dem Stand der Technik,

Figur 2

den Aufbau eines Kalina-Zyklus gemäß dem Stand der Technik,

Figur 3

eine erste Ausführungsform eines erfindungsgemäßen Zyklus,

Figur 4

eine zweite Ausführungsform eines erfindungsgemäßen Zyklus,

Figur 5

eine dritte Ausführungsform eines erfindungsgemäßen Zyklus,

Figur 6

eine vierte Ausführungsform eines erfindungsgemäßen Zyklus,

Figur 7

eine fünfte Ausführungsform eines erfindungsgemäßen Zyklus,

Figur 8

eine sechste Ausführungsform eines erfindungsgemäßen Zyklus, und

Figur 9

eine siebte Ausführungsform eines erfindungsgemäßen Zyklus.

Show it:

FIG. 1

the construction of an ORC cycle according to the prior art,

FIG. 2

the construction of a Kalina cycle according to the prior art,

FIG. 3

a first embodiment of a cycle according to the invention,

FIG. 4

a second embodiment of a cycle according to the invention,

FIG. 5

a third embodiment of a cycle according to the invention,

FIG. 6

A fourth embodiment of a cycle according to the invention

FIG. 7

A fifth embodiment of a cycle according to the invention

FIG. 8

a sixth embodiment of a cycle according to the invention, and

FIG. 9

A seventh embodiment of a cycle according to the invention.

At the in FIG. 1 The structure shown is a construction of an ORC cycle according to the prior art used in a geothermal application. For supplying a low-temperature mass flow 1, a deep pump 2 is provided, which promotes 3 thermal water with a temperature of 80 ° C from a geothermal source. The low-temperature mass flow 1 thus provides a starting temperature level of 80 ° C available and heated by means of a first heat exchanger 4 in an evaporator 5, a working fluid 6, which is brought to evaporate in the evaporator 5. The working fluid 6 is in the embodiment after FIG. 1 to pentane. After evaporation, the working fluid 6 is supplied to a functioning as an expansion turbine 7, in which the evaporated working fluid 6 performs work and is relaxed. This reduces the temperature of the working fluid 6, which subsequently passes through a recuperator 8, to an expansion temperature level. Downstream of the recuperator 8, the working fluid 6 passes through a condenser 9, in which the working fluid 6 is condensed again. After condensation, the working fluid 6 is fed back to the evaporator 5 by means of a feed pump 10 through the recuperator 8 and a preheater 11. The recuperator 8 serves to at least partially remove heat contained in the working fluid 6 after expansion in the turbine 7 and to supply it to the working fluid 6 before it enters the preheater 11.

The in FIG. 2 The structure of a Kalina cycle according to the prior art shown is similar in many parts to that in FIG. 1 constructed ORC structure. A low-temperature mass flow 1 fed from a geothermal source 3 heats a working fluid 6 in a desorber 12, which is then desorbed. Subsequently, this working fluid 6 is split in a separator 13 into a vapor phase 14 and an aqueous phase 15. As working fluid 6 ammonia-water mixture is used. Therefore, the vapor phase 14 is vapor rich in ammonia and the aqueous vapor Phase 15 around a low ammonia aqueous phase 15. The vapor phase 14 is then fed to a functioning as an expansion engine turbine 7, in which the steam 14 is expanded while doing performed. The aqueous phase 15 is brought together again via a high-temperature repulper 16 and a throttle 17 with the vapor phase 14 after leaving the turbine 7 and fed via a low-temperature recuperator 18 to an absorber 19. Subsequently, the working fluid 6 is fed back to the desorber 12 by means of a feed pump 10 via the low-temperature recuperator 18 and the high-temperature recuperator 16 and a preheater 11.

Starting from this prior art, the invention will be illustrated schematically and exemplified below with reference to various variants.

In a first variant according to FIG. 3 a first circuit 20 is provided, which is an ORC circuit, as shown for example in the FIG. 1 is shown. In addition, a first heat transformer 21 is provided, which has a warm side 22 and a cold side 23. The warm side 22 stands on a heat exchanger 24 with a low-temperature mass flow 1 in heat flow connection. This low-temperature mass flow 1 has a mass flow dm ₁ / dt at an initial temperature level T ₁ . The starting temperature level T ₁ is 120 ° C. After passing through the heat exchanger 24, the low-temperature mass flow 1 at a temperature T ₂ , which is at 126.34 ° C. The increase of the temperature T ₂ relative to the initial temperature level T ₁ results from the fact that an unrepresented heat flow in the ORC arrangement according to FIG. 1 between the turbine 7 shown there and the recuperator 8 shown there by means of a heat exchanger, not shown, for heating the cold side 23 of the heat transformer 21, wherein the thereby dissipated at an expansion temperature level second heat flow to a pump temperature level above the initial temperature T ₁ is pumped.

In one embodiment of the method, the in FIG. 1 shown condenser 9 and the recuperator 8 are also omitted, so that the working fluid 6 is passed to the turbine to dissipate the second heat flow through the heat exchanger, not shown, and from there to the preheater.

Downstream of the ORC circuit 20, the low temperature mass flow has a temperature T ₃ . This temperature is both lower than the first temperature level T ₁ and the second temperature T ₂ .

Instead of the ORC circuit 20, a Kalina cycle can also be used in an embodiment of the invention which is not shown.

Exemplary calculations are given in the following table for a saline brine of water with a salt content of 100 g per liter as low-temperature mass flow 1. The low-temperature mass flow 1 results from the bed in I / s and the density of the brine of 1077.84 kg / m ³ . For the sake of clarity, however, the volume flows are indicated. The inlet temperature, and thus the starting temperature level T ₁ is according to column 2 120 ° C. The outlet temperature T ₃ is according to column 3 75 ° C. From the heat capacity of the brine of 3.2 kJ / (kgK) results in a thermal performance according to column 4. Assuming an efficiency of the power plant according to column 5 results in an electric power according to column 6. The use of a heat transformer 21, which pumped after the expansion in the turbine from the working fluid 6 second heat flow to the higher pump temperature level of 160 ° C, leads to the assumption of a waste heat of 20% to a decoupled second heat flow according to column 7. Assuming that this second Heat flow is coupled after pumping to 160 ° C with a loss of 10% in the low-temperature mass flow, resulting in a coupled heat according to column 8, resulting in a temperature increase of the Low-temperature mass flow 1 according to column 9 of 6.34 K at a power plant efficiency of 12% leads. This results in an improvement in the electrical efficiency of the low-temperature power plant of 14.1%.

For other waste heat dissipated by the heat transformer, other values result accordingly. For example, results in a bed of 100 l / s and a power plant efficiency of 12% at a waste heat of 25%, a temperature increase of the low-temperature mass flow 1 of 7,92K and an improvement in the efficiency of the low-temperature power plant of 17.6%.

With a bed of 100 l / s with a power plant efficiency of 12% and a waste heat of 30% results in a temperature increase of 9.5 K and an improvement in the efficiency of the low-temperature power plant of 21.1%. Bed in l / s Inlet temp. in ° C Austrittstemp. in ° C thermal power in kW KW efficiency in% elec. Power in kW decoupled heat in kW coupled heat in kW Temperature increase in ° C Increase in efficiency 50 120 75 7760 12 931 1366 1093 6.34 14.1% 100 120 75 15521 12 1863 2732 2185 6.34 14.1% 150 120 75 23281 12 2794 4098 3278 6.34 14.1% 50 120 75 7760 14 1086 1335 1068 6.19 13.8% 100 120 75 15521 14 2173 2670 2136 6.19 13.8% 150 120 75 23281 14 3259 4004 3204 6.19 13.8% 50 120 75 7760 16 1242 1304 1043 6.05 13.4% 100 120 75 15521 16 2483 2608 2086 6.05 13.4% 150 120 75 23281 16 3725 3911 3129 6.05 13.4%

At the in FIG. 4 In addition to a first ORC circuit 20, a second ORC circuit 25 is provided, which is arranged sequentially to the first ORC circuit 20 downstream of a low-temperature mass flow 1. Furthermore, a first heat transformer 21 and a second heat transformer 26 are provided, which are each with its warm side 22 in heat flow connection with the low-temperature mass flow 1. The cold sides 23 of the heat transformers are in turn, as in the above embodiment according to the FIG. 3 arranged in the outflow of the turbine. The second heat flows taken out of the exhaust gas streams of the turbine, each at an expansion temperature level, are respectively pumped to a higher pump temperature level in the first heat transformer 21 or the second heat transformer 26. By a corresponding arrangement of a first heat exchanger 24 and a second heat exchanger 27, a stepwise increase in temperature of the first low-temperature mass flow 1 downstream of the first ORC cycle 20 from a temperature T ₂ to a temperature T ₃ and then subsequently to a temperature T _{4 are} provided , The temperature T ₁ is again lower than the initial temperature level T ₁ , wherein the temperature level T ₅ , at which the low-temperature mass flow 1 downstream of the second ORC circuit 25 exits again, is lower than the temperature T ₄ .

Using the above-mentioned brine as a low-temperature mass flow resulting at an initial temperature level T ₁ of 120 ° C and an outlet temperature T ₅ of 75 ° C, the following values for the temperatures T ₂ , T ₃ and T ₄ , wherein the higher pump temperature level each of the first and second heat transformers is 160 ° C and 20% of the waste heat from the turbine is released from the heat transformers at a 10% loss: T ₂ = 97.5 ° C, T ₃ = T ₂ + 3.96 ° C, T ₄ = T ₂ + 3.96 ° C + 4.26 ° C. An improvement in the efficiency of the entire system is 11.2%.

In the variant according to FIG. 5 a first ORC circuit 20 and a second ORC circuit 25 are provided, wherein a branch stream 28 is branched off from the low-temperature mass flow 1 downstream of the first ORC circuit 20 from this low-temperature mass flow 1, wherein a heat exchanger 24 is provided which is in heat flow connection with a warm side 22 of a heat transformer 21 and so heats a mass flow dm ₂ / dt at a temperature T ₂ to a temperature T ₃ . A cold side 23 of the heat transformer 21 is in turn brought into contact with a working fluid of the first ORC cycle 20 in the outflow of a turbine, as in the previously described embodiments. The thereby removed second heat flow is pumped by means of the heat transformer 21 to a temperature above the temperature T ₂ , so that the mass flow dm ₂ / dT from the temperature T ₂ to the temperature T ₃ can be heated. This heated mass flow dm ₂ / dt with the temperature T ₃ is used to operate the second ORC circuit 25. A downstream flow 29 downstream of the second ORC circuit 25 is fed back into the first low-temperature mass flow 1 downstream of the first ORC circuit 20. The effluent in this case has a temperature T ₄ , which is greater than the temperature T ₅ , which has the low-temperature mass flow 1 at the end. In addition, the temperature T _{3 is} greater than the temperature T ₂ .

Using the brine already described as a low-temperature mass flow, the following values result in an exemplary calculation. In this case, a branch stream 28 is provided in accordance with column 6 as a partial fill. The second heat flow, which is dissipated by the heat transformer 21 is again 20% of the entrained in the turbine exhaust heat. This second heat flow is returned to the higher pump level with a loss of 10% from the heat transformer after pumping. The inlet temperature and thus the starting temperature level is 120 ° C, the outlet temperature T ₅ is 75 ° C. The temperatures T ₂ and T ₄ are approximately identical to the temperature T ₅ . Bed in l / s Inlet temp. in ° C Austrittstemp. in ° C thermal power in kW Efficiency in% elec. Power at KW efficiency 12% Partial load in l / s el. power generation in KW Increase in efficiency 50 120 75 7760 12 931 9.50 177.01 19.0% 100 120 75 15521 12 1863 19,01 354.03 19.0% 150 120 75 23281 12 2794 28.51 531.04 19.0% 50 120 75 7760 14 1086 9.29 201.82 18.6% 100 120 75 15521 14 2173 18.58 403.64 18.6% 150 120 75 23281 14 3259 27.86 605.46 18.6% 50 120 75 7760 16 1242 9.07 225.29 18.1% 100 120 75 15521 16 2483 18.14 450.58 18.1% 150 120 75 23281 16 3725 27.22 675.87 18.1%

One possibility of fluidically separated circuits is in FIG. 6 shown. In this case, a first ORC circuit 20 and a second ORC circuit 25 are connected only via a heat transformer 21, wherein the warm side 22 of the heat transformer feeds a heat exchanger 24 with a heat flow. This heat flow is supplied to a low-temperature mass flow 1, which is guided via a downstream return 29a again to an input 29b of the ORC circuit 20 and thus continuously circulates. The heat flow supplied to the heat transformer 21 is taken from the effluent 29 downstream of the first ORC circuit 20.

In a modified arrangement according to FIG. 7 is the heat exchanger 24 contrary to the embodiment in FIG. 6 not downstream of the first ORC cycle 20, but arranged in this first ORC circuit 20. The heat exchanger 24 is provided adjacent or instead of a capacitor.

At the in FIG. 8 shown variant, no temperature increase of a low-temperature mass flow 1 is made, but this low-temperature mass flow 1 increased by partial recirculation 30. For this purpose, branched off from the low-temperature mass flow 1 downstream of an ORC circuit 20, a branch current 28 which passes through a heat exchanger 24 which is fed by the warm side 22 of the heat transformer 21. A cold side 23 of the heat transformer 21 is in turn connected to the ORC circuit 20 in the manner described above. In the heat exchanger 24, the branch current 28 dm ₃ / dt is heated from a temperature T ₂ to a pump temperature level T ₁ , which exactly corresponds to the output temperature level T _{1 of} the low-temperature mass flow 1. This results in a mass flow dm ₁ / dt + dm ₃ / dt compared to the original mass flow. At the same time, the outflowing mass flow is only dm ₁ / dt.

The following values are in turn calculated for a brine as a low-temperature mass flow with an initial temperature level of 120 ° C as the inlet temperature. The branch stream shall be set according to the partial packing specified in column 7. As a pump temperature level of the second heat flow 160 ° C are provided, the heat transformer 21 pumps 20% of the waste heat of the turbine with an efficiency of 90% to the pump temperature level. Fill in I / s Inlet temp. in ° C Austrittstemp. in ° C thermal power in kW KW efficiency in% elec. Power in kW Partial load in l / s Increase in efficiency 50 120 75 7,760.45 12 931.25 9.50 19.0% 100 120 75 15520.90 12 1,882.51 19,01 19.0% 150 120 75 23281.34 12 2,793.76 28.51 19.0% 50 120 75 7,760.45 14 1,086.48 9.29 18.6% 100 120 75 15520.90 14 2,172.93 18.58 18.6% 150 120 75 23281.34 14 3,259.39 27.86 18.6% 50 120 75 7,760.45 16 1,241.67 9.07 18.1% 100 120 75 15520.90 16 2,483.34 18.14 18.1% 150 120 75 23281.34 16 3,725.02 27.22 18.1%

At the in FIG. 9 As shown, a working fluid 6 is brought directly upstream of a turbine 7 by means of a heat transformer 21 to a higher temperature level. In detail, it is again an ORC cycle, in which a low-temperature mass flow 1 heats an evaporator 5 at an initial temperature level, whereby the working fluid 6 is evaporated and fed to the turbine 7 after additional heating by a warm side 22 of the heat transformer 21 becomes. There is an expansion, whereby work is done, which is converted into electrical energy in an electrical generator 31. After exiting the turbine 7, the expanded working fluid 6 is fed to a heat exchanger 24 which is in heat flow communication with a cold end 23 of the heat transformer 21. As a result, a second heat flow is withdrawn from the expanded working fluid 6 exiting the turbine at an expansion temperature T ₅ which is pumped by means of the heat transformer 21 to a pump temperature level above the temperature T ₃ . As a result, the temperature T ₄ before entering the turbine 7 is above the temperature T _{1 of} the low-temperature mass flow 1 in the evaporator.

The following values are again calculated for a brine as a low-temperature mass flow with an initial temperature level T ₁ of 120 ° C as the inlet temperature. The pumping temperature level of the second heat flow 160 ° C are provided, the heat transformer 21 pumps a 20% of the waste heat of the turbine with an efficiency of 90% to the pump temperature level. The outlet temperature T ₅ is 75 ° C. Bed in l / s Inlet temp. in ° C Austrittstemp. in ° C thermal power in kW KW efficiency in% elec. Power in kW decoupled heat in kW coupled heat in kW Increase in efficiency 50 120 75 7760 12 931 1366 1093 14.1% 100 120 75 15521 12 1863 2732 2185 14.1% 150 120 75 23281 12 2794 4098 3278 14.1% 50 120 75 7,760.45 14 1,086.46 1,334.80 1,067.84 13.8% 100 120 75 15520.90 14 2,172.93 2,669.59 2,135.68 08.13% 150 120 75 23281.34 14 3,259.39 4,004.39 3,203.51 13.8% 50 120 75 7,760.45 16 1,241.67 1,303.76 1,043.00 13.4% 100 120 75 15520.90 16 2,483.34 2,607.51 2,086.01 13.4% 150 120 75 23.281.34 16 3,725.02 3,911.27 3,129.01 13.4%

LIST OF REFERENCE NUMBERS

1

Low-temperature mass flow

2

pumpjack

3

geothermal source

4

first heat exchanger

5

Evaporator

6

working fluid

7

turbine

8th

recuperator

9

capacitor

10

feed pump

11

preheater

12

desorber

13

separator

14

vapor phase

15

aqueous phase

16

High-temperature recuperator

17

throttle

18

Low temperature recuperator

19

absorber

20

first ORC cycle

21

first heat transformer

22

warm side of the heat transformer

23

cold side of the heat transformer

24

(first) heat exchanger

25

second ORC cycle

26

second heat transformer

27

second heat exchanger

28

branch current

29

effluent

29a

downstream feedback

29b

Input (of the ORC circuit)

30

Partial repayment

31

electric generator

Claims (15)

Thermodynamic machine, in particular low-temperature power station, with at least one first circuit (20) for circulating a working fluid, the first circuit (20) comprising at least one expansion machine (7) and at least one heat exchanger (24; 27) for supplying a first heat flow from a low-temperature Mass flow (1) into the first circuit (20), wherein at least one heat transformer (21; 26) is provided with its colder side (23) downstream of the expansion machine (7) in heat flow communication with the first circuit (20), and with its warmer side (22) with the low-temperature mass flow (1) or the first circuit (20) is in heat flow connection. Thermodynamic machine according to claim 1, characterized in that a second circuit (25), in particular an ORC circuit, with a second heat transformer (26), which is arranged in the same way as the first heat transformer (21), sequentially to the first circuit ( 20) is arranged, wherein the first (21) and second heat transformer (26) each with its warm side (22) with the low-temperature mass flow (1) between the first (20) and second circuit (25) are in heat flow connection. Thermodynamic machine according to claim 1, characterized in that a second circuit (25) is provided, which is fed from a branch stream (28) from the low-temperature mass flow (1) downstream of the first circuit (20), wherein the first heat transformer (21 ) with its warmer end (22) with the branch stream (28) upstream of the second circuit (25) is in heat flow connection and wherein a downstream recirculation of the branch stream (28) downstream of the second circuit (25) in the low-temperature mass flow (1) is provided. Thermodynamic machine according to claim 1, characterized in that a second circuit (25) is provided, which has a downstream feedback (29a) on its input (29b), which with the warmer end (22) of the first heat transformer (21) in heat flow connection stands. Thermodynamic machine according to one of the preceding claims, characterized in that at least one return line (30) for returning a partial flow (28) from the low-temperature mass flow (1) downstream of the first circuit (20) is provided, wherein the warm side (22) the first heat transformer (21) is in heat flow connection with this partial flow (28). Thermodynamic machine according to one of the preceding claims, characterized in that the warm side (22) of the first heat transformer (21) in a section between an evaporator (5) and the expansion machine (7) with the first circuit (20) is in heat flow connection. Method for operating a thermodynamic cycle, in particular in a low-temperature power plant according to one of the preceding claims, comprising at least one circuit (20, 25) in which a working fluid (6) circulates, through which a low-temperature mass flow (1) having a starting temperature level becomes a first Heat flow is supplied, wherein after an expansion of the working fluid (6) in an expansion machine (7) under release of mechanical energy to the working fluid (6) at a compared to the Ausgangstemperaturniveau a second heat flow is withdrawn at a lower expansion temperature level, characterized in that the second heat flow in at least one heat transformer (21, 26) is pumped to a pump temperature level which is higher or equal to the outlet temperature level and the low-temperature mass flow (1). and / or the at least one circuit (20, 25), in particular immediately before the expansion machine (7), at least partially fed back. A method according to claim 7, characterized in that by the raised to the pump temperature level second heat flow, a temperature of the low-temperature mass flow (1) and / or a temperature of the working fluid (6) in the at least one circuit (20, 25) is increased , A method according to claim 7 or 8, characterized in that the low-temperature mass flow (1) by partial return of a heated with the second heat flow low-temperature mass flow effluent (29) is increased. Method according to one of the preceding claims 7 to 9, characterized in that the at least one circuit (20, 25) is operated as Organic Rankine cycle (ORC) or Kalina cycle. Method according to one of the preceding claims 7 to 10, characterized in that at least two circuits, in particular two ORC circuits (20; 25), are sequentially fed by the low-temperature mass flow (1), wherein a return to the respective pump temperature level pumped second heat flows of the circuits in the low-temperature mass flow (1) between the first (20) and the second circuit (25). Method according to one of the preceding claims 7 to 10, characterized in that at least two circuits (20, 25), in particular two ORC circuits, are provided, wherein from the low-temperature mass flow (1) downstream of the first circuit (20) a branch stream (28) for supplying the second circuit (25) is branched off, which downstream of the second circuit (25) again with the low-temperature mass flow (1) is combined downstream, wherein the pumped to the pump temperature level second heat flow of the first circuit (20 ) is supplied to the branch stream (29). Method according to one of the preceding claims 7 to 10, characterized in that at least two circuits (20, 25), in particular two ORC circuits, are provided, wherein the pumped to the temperature level pumped second heat flow of the first circuit (20) an outflow the second circuit (25) is supplied, which is supplied to the second circuit (25) again as an influx. Method according to one of the preceding claims 7 to 13, characterized in that from the low-temperature mass flow (1) downstream of a circuit (20) a branch stream (28) is branched off, which is heated with the pumped to the pump temperature level second heat flow and the low-temperature mass flow (1) is supplied upstream of the circuit (20), wherein preferably the branch stream (28) is dimensioned so that its pumping temperature level before the return corresponds to the starting temperature level of the low-temperature mass flow (1). Method according to one of the preceding claims 7 to 14, characterized in that a temperature of a heated by the second heat flow Wärmetrarisformatorfluids is raised by at least two expeller adsorbers on or above the pump temperature level to the pumping the second heat flow to the pump temperature level, or at least substantially adiabatically compressing a heat transformer fluid heated by the second heat flow while being heated to or above the higher pump temperature level to pump the second heat flow to the pump temperature level.

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