Low-Temperature Power Plant and Process for Operating a Thermodynamic Cycle

The invention concerns a mechanism for operating a thermodynamic cycle, particularly a low-temperature power plant, as well as a related process, whereby a low-temperature mass stream (1) feeds a first heat stream to a working fluid (6) circulating in a first cycle at an initial temperature level (T1), whereby subsequent to an expansion of the working fluid in an expansion machine (7) a second heat stream is extracted from the working fluid (6) at a lower expansion temperature level (T5) with respect to the initial temperature level (T1) for an improvement of the energy exploitation of the thermodynamic cycle or the low temperature power plant, which is pumped to a higher pump temperature level and is fed to the low temperature mass stream (1) and/or fed at least partially to the first cycle.

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Description

The invention concerns a mechanism for operating a thermodynamic cycle, particularly a low-temperature power plant, as well as a related process, whereby a low-temperature mass stream feeds a first heat stream to a working fluid that circulates in a first cycle at an initial temperature level and whereby subsequent to an expansion of the working fluid in an expansion machine, a second heat stream is extracted from the working fluid at a lower expansion temperature level relative to the initial temperature level, especially in a cooling device.

Thermodynamic cycles of this type are used especially in low-temperature power plants for recovering the energy from a low-temperature mass stream, for example, with a turbine, which serves as an expansion machine. Low-temperature power plants find application, for example, in geothermal energy, solar energy, in energy recovery from biomass, and waste heat which is created, for example, in rotting or fermenting processes, i.e. in a landfill or similar. In the course of saving fossil fuels and in the course of an attempt of dispensing with such fossil fuels completely, interest in processes of this type is growing steadily.

Based on the smaller temperature difference in the operation of a thermodynamic cycle compared to a high-temperature power plant, the degree of effectiveness of a low-temperature power plant is naturally always significantly lower than in a high-temperature power plant. Even more, as the temperature of a low-temperature mass stream is specified based on circumstances, for example, a geothermal heat source or a process that conveys waste heat, there are attempts to improve the energy exploitation of a low-temperature power plant with optimization measures.

It is the objective of the present invention to improve the energy exploitation of operating a low-temperature power plant, especially, with only small changes to the apparatus of existing thermodynamic cycles.

According to the invention, this objective is solved by a thermodynamic machine, particularly a low-temperature power plant with the characteristics of claim 1, as well as by a process for operating a thermodynamic cycle, particularly a low-temperature power plant with the characteristics of claim 6. Advantageous embodiments and further developments are indicated in the respective dependent claims.

In a thermodynamic machine according to the invention, particularly in a low-temperature power plant with at least one first cycle for circulating a working fluid, the first cycle has at least one expansion machine and at least a first heat exchanger for feeding the first heat stream from a low-temperature mass stream into the first cycle, whereby at least one heat transformer is provided with its colder side between the expansion machine and the cooling mechanism or in the cooling device, which is, in particular, a condenser that is in heat stream connection with the cycle, and with its warmer side with the low-temperature mass stream or is in heat stream connection with the first cycle. As heat stream connection, the heat transformer has, for example, a heat exchanger on its colder side and on its warmer side respectively, Preferably, this makes an increase in the degree of effectiveness or a heat throughput of a thermodynamic cycle possible, particularly of a low-temperature power plant. Especially, existing low-temperature cycles can be retooled with little time and effort by the use of a heat transformer.

For example, a water stream of geothermal brine is used as a low-temperature mass stream. At sufficient temperature of the geothermal brine, [Note: original says “Sonde” instead of Sole=brine.] the low-temperature mass stream can also be present in the form of steam. However, in place of water, other fluids can also be used as low-temperature mass streams. Alternatively to a geothermal brine [Note: original has Sonde], the low-temperature mass stream can also be brought to its application temperatures with solar heat, waste heat from biomass processes, waste heat from other processes or the like.

In particular, the working fluid is selected in such a way that at a temperature of the low-temperature mass stream it is present in vaporized form, whereas it is present in liquid phase at one of the lower temperature levels of the cycle. Depending on the application temperature, commonly used cooling agents are used, for example, pentane, butane, other hydrocarbons or the like. In a simple cycle, for example, the working fluid is vaporized in a first step in a heat exchanger by the low-temperature mass stream, in a second step it is expanded in a turbine that acts as an expansion machine and subsequently it is condensed again, so that it can be heated anew by the low-temperature mass stream in the heat exchanger.

For example, the cycle can be operated as an organic Rankine cycle, an ORC. In the process, an ORC fluid, for example, pentane, butane or another cooling agent, is heated in a pre-heater, vaporized in a vaporizer that is heated by the low-temperature mass stream, conveyed to a turbine that acts as an expansion machine and expanded there, and cooled down in a condenser so that it can be fed into the cycle anew. In this process, a recuperator is provided between the turbine and the condenser which serves to recover residual heat from the exhaust emission of the turbine. The amount of heat that is generated in this process is used to feed the pre-heater. In a process according to the invention, a heat transformer is provided in addition, which extracts a second heat stream from the working fluid subsequent to the turbine or the expansion machine and after the recuperator and prior to a cooling device, which is, in particular, a condenser, and pumps such to a higher pump temperature level and again feeds it into the cycle or the low-temperature mass stream.

With respect to the fundamentals of an ORC process, reference is made to DE 692 18 206 T2, to the entirety of which reference is made within the framework of the revelation. Preferably, use of an ORC cycle makes it possible to retool existing systems that work according to this principle at little expense to improve their degree of effectiveness.

In a different embodiment, the cycle can be operated as a Kalina cycle. In doing so, the Kalina process uses a method that is similar to an ORC process, whereby the working fluid is first heated, vaporized, in the expansion machine, for example, a turbine, pressure is released, it is condensed and subsequently conveyed to heating again. In contrast to an ORC process, the working fluid in the vaporizer or desorber is split into a steam phase and a watery phase with a subsequent separator, whereby the steam is conveyed through the expansion machine, while the tension of the fluid phase is released after a potential recovery of heat by a restrictor of the exit pressure of the expansion machine, particularly the turbine. Subsequently, the two partial streams are united again and stream back through an internal heat exchanger to a condenser or absorber. After the condensation/absorption, pressure is increased again, for example, by a feed pump. With respect to the fundamentals of an ORC process, reference is made to US 2004 0182084 A1, to the entirety of which reference is made in the revelation.

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

Particularly downstream of the expansion machine, a cooling device is provided, for example, a condenser or the like, whereby the second heat stream is extracted from the low-temperature mass stream prior to or in the cooling mechanism.

As heat transformer, a system with at least two ejector-adsorbers is used, as described in patent specification DE 34 08 192 C2, to the entirety of which reference is made within the framework of the revelation. Alternatively, a power heating machine with an at least essentially adiabatic compression step of a working fluid can be used.

According to a further development, a second cycle, particularly an ORC cycle with a second heat transformer which is mounted in the same way as the first heat transformer, located sequentially to the first cycle, whereby the first and second heat transformer with their warm side respectively are in heat stream connection with the low-temperature mass stream between the first and the second cycle. For this purpose, the heat transformers are, for example, respectively provided with heat exchangers at their ends, which are, for one, in heat stream connection on the warmer side of the heat transformer with the low-temperature mass stream, and for another, on the colder side of the heat transformers they are in heat stream connection with the respective cycle. The temperature on the warmer side of the second heat transformer is thereby preferably lower than the temperature on the warmer side of the first heat transformer. Preferably, the heat exchangers of the heat transformers are located in the low-temperature mass stream in such a way that first the heat of the second heat transformer is given off to the low-temperature mass stream and subsequently the heat of the second heat transformer. Thereby, the temperature of the low-temperature mass stream preferably increases stepwise upstream of the second cycle.

In a further embodiment, a second cycle is provided, which is fed downstream of the first cycle by a branch stream of the low-temperature mass stream, whereby the first heat transformer with its warmer end is in heat stream connection with the branch stream upstream of the second cycle and whereby a down-stream feedback of the branch stream is provided downstream of the second cycle into the low-temperature mass stream. For example, an existing heat cycle, particularly according to the ORC principle, can be improved in its energy exploitation by coupling it with a second heat cycle, particularly according to the ORC principle, so that only a feeder line must be placed from one outlet of the first cycle to the inlet of the second cycle and a downstream line from the second cycle again to the first downstream line, whereby in addition to the basically ordinary heat cycles according to, for example, the ORC principle, a heat transformer is used in such a way that its warm end is in heat stream connection with the inlet line of the second heat cycle. Preferably, electricity exploitation can thereby be improved by approximately 15%.

In order to realize a closed low-temperature mass stream cycle, a second cycle can be provided which shows a downstream feedback to its inlet, which is in heat stream connection with the warmer end of the first heat transformer. The first and second cycle stream separately, in particular, they are completely separate from one another and are only connected with one another in heat stream connection by the first heat transformer.

In a further development, at least one feedback line for feeding back a partial stream from the low-temperature mass stream is provided downstream of the first cycle, whereby the warm side of the first heat transformer is in heat stream connection with this partial stream. Thereby, the low-temperature mass stream is preferably increased upstream of the first cycle. Particularly, heat transformers and feedback lines are to be dimensioned such that the recycled partial stream can be heated precisely to the initial temperature level, i.e. the first temperature of the low-temperature mass stream.

In another embodiment, the warm side of the first heat transformer is in heat stream connection with the first cycle in a section between the vaporizer and the expansion machine. In particular, in this section a corresponding heat exchanger is provided which is fed by the warm side of the first heat transformer. For this reason a temperature of the working fluid directly before entry into the expansion machine is preferably increased and thereby the energy exploitation of the expansion is improved.

Moreover, the invention concerns a process for operating a thermodynamic cycle, particularly a low-temperature power plant, particularly according to one of the previously described embodiments in which a working fluid circulates, to which a first heat stream is fed by a low-temperature mass stream at an initial temperature level, whereby after expansion of the working fluid in an expansion machine—by releasing mechanical energy—a second heat stream is extracted from the working fluid at a second lower expansion temperature level with respect to the initial temperature level, particularly prior to entry into a cooling device, which is pumped to a pump temperature level that is higher or equal to the initial temperature level in at least one heat transformer, and is again fed to the low-temperature mass stream and/or the first cycle at least in part.

Advantageously, this makes an increase in the degree of effectiveness or the heat throughput rate of the thermodynamic cycle possible, particularly of a low-temperature power plant.

The initial temperature level which corresponds to the temperature level of the low-temperature mass stream is, for example, a temperature between an ambient exterior temperature and approximately 200° C., for example, 120° C. The pump temperature level is preferably at least equally high, advantageously, however, higher than the initial temperature level.

In order to pump the second heat stream to the higher pump temperature level, according to a further development, a temperature of a heat transformer fluid that is heated by a second heat stream with two ejector adsorbers is raised to or above the higher pump temperature level.

In the process, for example, the heat transformer fluid is driven out of a fixed adsorption means by a relatively low first pressure, the gaseous heat transformer fluid that is created during the ejection at a relatively low first temperature is transformed into a fluid phase by giving off heat and heat transformer fluid that is present in fluid phase at an intermediate second temperature and at a relatively higher pressure is transformed into the gaseous phase by absorbing heat, the gaseous working fluid by giving off useful heat at a relatively high third temperature is adsorbed by a fixed adsorption means and the process is maintained by cyclical ejection and adsorption of working fluid in the adsorption means or parts thereof, whereby at least two ejection adsorbers present at varying temperatures and pressures exchange heat via heat exchange devices from the heat transformer fluid-richer to the heat transformer fluid-poorer ejection-adsorber, whereby subsequent to the heat exchange between these ejector-adsorbers, heat transformer fluid is exchanged between these ejection adsorbers by pressure adjustment, and is driven out of the heat transformer fluid-richer adsorption means by absorbing heat and is adsorbed in the heat transformer fluid-poorer adsorption means by generating heat.

In a further variation, a heat transformer fluid heated by a second heat stream is at least essentially adiabatically compressed and thereby heated to or above the pump temperature level in order to pump the second heat stream to the pump temperature level. A suitable cooling agent such as, for example, pentane, butane or another suitable hydrocarbon compound is used as heat transformer fluid depending on the temperature range.

According to a further development it is provided that through a second heat stream that is raised to the pump temperature level, a temperature of the low-temperature mass stream or/and a temperature of the working fluid is increased in the first cycle. Preferably, this makes an increase of the degree of effectiveness of the thermodynamic cycle possible, particularly the low-temperature power plant. In this process, for example, the second heat stream is pumped to the higher pump temperature level, which lies above the initial temperature level, the temperature of the low-temperature mass stream. In this manner, the temperature of the low-temperature mass stream in increased. Similarly, an increase in the temperature of the working fluid can be provided at one point in the cycle. 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 stream is increased by a partial feedback of a low-temperature mass stream outflow that is heated with a second heat stream. Preferably, the partially recirculated low-temperature mass stream outflow is pumped to the same temperature level as the incoming low-temperature mass stream. It is self-explanatory that the volume stream or mass stream transported out of a geothermal source, for example, is not changed in the process. However, as a result of the recirculation, the mass stream or volume stream that passes through the cycle is increased.

Various embodiments and procedures or arrangements can be provided for the operation of a cycle. In a first provided process, at least two cycles, particularly ORC cycles, are sequentially fed by the low-temperature mass stream, whereby the recirculation into the low-temperature mass stream of the second heat streams that are respectively pumped to the higher pump temperature level takes place between the first and the second cycle. Preferably, this makes an increase in temperature of the low-temperature mass stream possible which has passed through the first cycle, particularly the ORC process, and an enhanced energy exploitation of the second ORC process.

In an additional variant, at least two cycles are provided, particularly ORC cycles, whereby from the low-temperature mass stream downstream of the first cycle a branch stream is branched off for feeding the second cycle, which is reunited again downstream with the low-temperature mass stream downstream of the second cycle, whereby the second heat stream that is pumped to the higher temperature level of the first cycle is conveyed to the branch stream. Advantageously, this makes an enhancement of the existing system possible by coupling in a second thermodynamic cycle, particularly an ORC cycle.

According to a further development, at least two cycles, particularly two ORC cycles are provided, whereby the second heat stream that is pumped to the pump temperature level of the first cycle is fed to an outflow of the second cycle, which is fed to the second cycle again as inflow. As a result, the second ORC cycle can be designed completely separate from the first ORC cycle except for a heat stream connection. In this process, the heat stream is conveyed without exchanging a mass stream between the two cycles.

In an additional embodiment it is provided that from the low-temperature mass stream downstream of the first cycle a branch stream is branched off which is heated with the second heat stream that is pumped to the higher pump temperature level and is fed again to the low-temperature mass stream upstream of the first cycle.

Thereby it is provided that the branch stream is dimensioned in such a way that its pump temperature level corresponds to the initial temperature level of the low-temperature mass stream prior to being recirculated. In this way, the low-temperature mass stream is enlarged upstream of the first cycle. Advantageously, this leads to enhanced energy exploitation. Simultaneously, particularly a low-temperature mass stream outflow is not increased in spite of the higher low-temperature mass stream passing through the first cycle.

In a different embodiment, the second heat stream is extracted downstream of the expansion machine and after being pumped to the higher pump temperature level, is again fed into the first cycle particularly directly before the expansion machine. Preferably, a temperature in a mass stream of the working fluid in the first cycle between a vaporizer and the expansion machine is thereby increased. In the process, the heat potential in this mass stream is increased in particular.

In the following, the invention is explained using the drawing. However, the invention is not limited to the combination of characteristics shown there. Rather, characteristics shown in the respective figures as well as the description can be combined with one another within the framework of the protective area of the claims for further development.

Shown are:

FIG. 1 design of an ORG cycle according to prior art,

FIG. 2 design of a Kalina cycle according to 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.

The design shown in FIG. 1 is a design used in a geological application of an ORC cycle according to prior art. For supplying a low-temperature mass stream 1, a deep well pump 2 is provided, which transports thermal water from a geothermal well 3 that has a temperature of 80° C. Thus the low-temperature mass stream 1 thus provides an initial temperature level of 80° C. and heats a working fluid 6 by means of a first heat exchanger 4 in a vaporizer 5, which is brought to vaporization in vaporizer 5. In the embodiment according to FIG. 1, working fluid 6 is pentane. After vaporization, working fluid 6 is fed to a turbine 7 that acts as an expansion machine in which vaporized working fluid 6 works and is being released. In the process, the temperature of working fluid 6, which subsequently runs through a recuperator 8 is decreased to an expansion temperature level. Downstream of recuperator 8, working fluid 6 runs through a condenser 9, in which working fluid 6 is condensed again. After condensation, working fluid 6 is fed again to vaporizer 5 by delivery pump 10 through recuperator 8 and a pre-heater 11. In this process, recuperator 8 serves to at least partially extract heat contained in working fluid 6 after expansion in turbine 7 and feed it again to the working fluid 6 prior to entry into pre-heater 11.

The design of a Kalina cycle according to prior art that is shown in FIG. 2 is in large part similar to the ORC design shown in FIG. 1. A low-temperature mass stream 1 that is fed by a geothermal well 3 heats a working fluid 6 in a desorber 12 which is then desorbed. Subsequently, this working fluid 6 is split into a steam phase 14 and a watery phase 15 in a separator 13.

Ammonia mixed with water is used as working fluid 6. For this reason, the steam phase 14 is ammonia-rich steam and the watery phase 15 is an ammonia-poor watery phase 15. Subsequently, the steam phase 14 is delivered to a turbine 7 that acts as an expansion machine in which steam 14 is expanded and thereby work is performed. The watery phase 15 is put together again with the steam phase 14 via a high temperature recuperator 16 and a restrictor 17 after exiting turbine 7, and conveyed again to an absorber 19 via a low-temperature recuperator 18. Subsequently, working fluid 6 is again fed to desorber 12 by a feed pump 10 via low temperature recuperator 18 and high temperature recuperator 16, as well as pre-heater 11.

Based on this prior art, the invention is shown in the following by using various variants schematically and as examples.

In a first variant as per FIG. 3, a first cycle 20 is provided which is an ORC cycle as it is shown in FIG. 1, for example. Additionally, a first heat transformer 21 is provided which has a warmer side 22 and a colder side 23. The warm side 22 has a heat stream connection with a low-temperature mass stream 1 via heat exchanger 24. This low-temperature mass stream 1 has a mass stream dm1/dt at an initial temperature level T1. Thereby, the initial temperature level T1 is 120° C. After passing through heat exchanger 24, low-temperature mass stream 1 has a temperature T2, which is 126.34° C. The increase of temperature T2 with respect to initial temperature level T1 is a result of, that a heat stream—not shown—in the ORC arrangement as per FIG. 1 between turbine 7 that is shown there and recuperator 8 that is shown there, a heat exchanger—not shown—is used to heat the cold side 23 of heat transformer 21, whereby the second heat stream that is extracted at an expansion temperature level is pumped to a pump temperature level above the initial temperature level T1.

In an embodiment of the process, condenser 9 and recuperator 8 that are shown in FIG. 1 can also be omitted so that working fluid 6—after the turbine—is heated for extraction of the second heat stream by the—not shown—heat exchanger and is conveyed from there to the pre-heater.

Downstream of ORC cycle 20, the low-temperature mass stream has a temperature T3. This temperature is lower than the first temperature level T1 as well as the second temperature T2.

In place of ORC cycle 20, in an embodiment according to the invention that is not shown, a Kalina cycle can also be used.

The following table shows exemplified calculations for salt-containing brine with a salt content of 100 g per liter as low-temperature mass stream 1. The low-temperature mass stream 1 is indicated in the first column as delivery in I/s and the density of the brine is 1077.84 kg/m3. For reasons of clarity, however, only the volume streams are indicated. The inlet temperature and thus the initial temperature level T1 is 120° C., as shown in column 2. The outlet temperature T3 is 75° C., as shown in column 3. The heat capacity of the brine of 3.2 kJ/(kgK) results in thermal output as shown in column 4. When a degree of effectiveness of the power plant is assumed as indicated in column 5, electrical output results as shown in column 6. Use of a heat transformer 21, which pumps the second heat stream to the higher pump temperature level of 160° C. after it has been extracted from working fluid 6 subsequent to expansion in the turbine, leads—assuming waste heat of 20%—to an output of a second heat stream as per column 7. Assuming that this second heat stream after it is pumped to 160° C. at a loss of 10% is input into the low-temperature mass stream, input heat as per column 8 results, which leads to a temperature increase of low-temperature mass stream 1 as per column 9 of 6.34 K, at a degree of effectiveness of 12% for the power plant. Thus an improvement of the electrical effectiveness of the low-temperature power plant of 14.1% is the result.

For other waste heat that is dissipated by the heat transformer, other values are attained respectively. For example, at a delivery of 100 I/s and a degree of effectiveness of the power plant of 12% at waste heat of 25%, a temperature increase of the low-temperature mass stream 1 of 7.92K results and an improvement of the degree of effectiveness of the low-temperature power plant of 17.6%.

At a delivery of 100 I/s when the power plant has a degree of effectiveness of 12% and waste heat of 30% a temperature increase of 9.5K results and an improvement of the degree of effectiveness of the low-temperature power plant of 21.1%.

Delivery Inlet Outlet Thermal KW Electrical Output Input Temperature Increase in in Temp. in Temp. in output in effectiveness output in heat in heat in increase in effectiveness l/s ° C. ° C. kW in % kW kW kW ° C. % 50 120 75 7,760 12 931 1,366 1,093 6.34 14.1% 100 120 75 15,521 12 1,863 2,732 2,185 6.34 14.1% 150 120 75 23,281 12 2,794 4,098 3,278 6.34 14.1% 50 120 75 7,760 14 1,086 1,335 1,068 6.19 13.8% 100 120 75 15,521 14 2,173 2,670 2,136 6.19 13.8% 150 120 75 23,281 14 3,259 4,004 3,204 6.19 13.8% 50 120 75 7,760 16 1,242 1,304 1,043 6.05 13.4% 100 120 75 15,521 16 2,483 2,608 2,086 6.05 13.4% 150 120 75 23,281 16 3,725 3,911 3,129 6.05 13.4%

In the variant shown in FIG. 4, in addition to a first ORC cycle 20, a second ORC cycle 25 is provided, which is located sequentially downstream of first ORC cycle 20 relative to a low-temperature mass stream 1. Further, a first heat transformer, 21, as well as a second heat transformer 26 is provided which have a heat stream connection with low-temperature mass stream 1 with their warmer sides 22 respectively. In turn, the cold sides 23 of the heat transformers are located, as in the previous example of an embodiment as per FIG. 3, down-stream of the turbine. The second heat flows extracted from the waste gas streams of the turbine respectively at an expansion temperature level, are pumped respectively to a higher pump temperature level in first heat transformer 21 or in second heat transformer 26. As a result of a corresponding location of first heat exchanger 24 and a second heat exchanger 27, a step-wise temperature increase of the first low-temperature mass stream 1 downstream of first ORC cycle 20 can be provided from a temperature T2 to a temperature T3 and then subsequently to a temperature T4. Thereby in turn, temperature T1 is lower than the initial temperature level T1, whereby temperature level T5, at which low-temperature mass stream 1 exits again downstream of the second ORC cycle 25, is lower than temperature T4.

By using the previously mentioned brine as low-temperature mass stream, at an initial temperature level T1 of 120° C. and an exit temperature T5 of 75° C., the following values result for temperatures T2, T3 and T4, whereby the higher pump temperature level of the first and second heat transformer is respectively 160° C. and 20% of the waste heat of the turbine is dissipated by the heat transformers at a loss of 10%: T2=97.5° C., T3=T2+3.96° C., T4=T2+3.96° C.+4.26° C. Thereby, the degree of effectiveness of the overall system is improved by 11.2%.

In a variant according to FIG. 5, a first ORC cycle 20 and a second ORC cycle 25 are provided, whereby a branch stream 28 is branched off from low-temperature mass stream 1 downstream of first ORC cycle 20, whereby a heat exchanger 24 is provided which has a heat stream connection with a warm side 22 of a heat transformer 21, and thus heats a mass stream dm2/dt from a temperature T2 to a temperature T3. A cold side 23 of heat transformer 21 is thereby in turn, as in the previously described embodiments, brought in contact with a working fluid of first ORC cycle 20 downstream of a turbine. The second heat stream that is extracted thereby is pumped by a heat transformer 21 to a temperature above temperature T2, so that the mass stream dm2/dT can be heated from temperature T2 to temperature T3. This heated mass stream dm2/dt at a temperature T3 is used for the operation of second ORC cycle 25. An outflow 29 downstream of second ORC cycle 25 is fed again—downstream of the first ORC cycle 20—into first low-temperature mass stream 1.

Thereby, the outflow shows a temperature T4, which is larger than T5, which is shown by low-temperature mass stream 1 at the end. Moreover, temperature T3 is higher than temperature T2.

By using the brine that was already presented as low-temperature mass stream, the following values result in an exemplified calculation. Thereby, a branch stream 28 is provided as per partial delivery according to column 6. The second heat stream which is extracted by heat transformer 21, also amounts to 20% of the heat carried in the outflow from the turbine. This second heat stream is given off again at a loss of 10% by the heat transformer after being pumped to the higher pump level. The input temperature and thus the initial temperature level is 120° C., the exit temperature T5 is 75° C. Thereby, temperatures T2 and T4 are approximately identical to temperature T5.

Delivery Inlet Outlet Thermal Degree of Electrical output Partial Electrical energy Increase in in Temp. in Temp. in output in effectiveness in in KW effectiveness delivery in creation in effectiveness l/s ° C. ° C. kW % 12% l/s KW % 50 120 75 7,760 12 931 9.50 177.01 19.0% 100 120 75 15,521 12 1,863 19.01 354.03 19.0% 150 120 75 23,281 12 2,794 28.51 531.04 19.0% 50 120 75 7,760 14 1,086 9.29 201.82 18.6% 100 120 75 15,521 14 2,173 18.58 403.64 18.6% 150 120 75 23,281 14 3,259 27.86 605.46 18.6% 50 120 75 7,760 16 1,242 9.07 225.29 18.1% 100 120 75 15,521 16 2,483 18.14 450.58 18.1% 150 120 75 23,281 16 3,725 27.22 675.87 18.1%

One possibility of separately streaming cycles is shown in FIG. 6. Thereby, a first ORC cycle 20 and a second ORC cycle 25 are only connected by a heat transformer 21, whereby the warm side 22 of the heat transformer supplies a heat exchanger 24 with a heat stream. This heat stream is fed to a low-temperature mass stream 1, which, via a downstream feedback 29a is again conveyed to an inlet 29b of ORC cycle 20 and thus is continuously circulated. The heat stream supplied to heat transformer 21 is extracted downstream of first ORC cycle 20 from outflow 29.

In a modified arrangement according to FIG. 7, heat exchanger 24, contrary to the embodiment in FIG. 6, is not downstream of first ORC cycle 20, but located in this first ORC cycle 20. Heat exchanger 24 is thereby provided next to or instead of a condenser.

In the variant shown in FIG. 8, no temperature increase of a low-temperature mass stream 1 is undertaken instead, this low-temperature mass stream 1 is increased by partial recirculation 30. For this purpose, a branch stream 28 is branched off from the low-temperature mass stream 1 downstream of an ORC cycle 20, which runs through a heat exchanger 24 that is fed by the warm side 22 of heat transformer 21. A cold side 23 of heat transformer 21 is in turn connected with ORC cycle 20 in the way it was previously described. In heat exchanger 24, branch stream 28 dm3/dt is heated from a temperature T2 to a pump temperature level T1, which precisely corresponds to the initial temperature level T1 of the low-temperature mass stream 1. In this manner, a comparison to the originally present mass stream dm1/dt+dm3/dt results. Simultaneously, the mass stream flowing downstream is only dm1/dt.

The following values are in turn calculated for brine as a low-temperature mass stream with an initial temperature level of 120° C. as inlet temperature. The branch stream is set as per the partial delivery shown in column 7. As pump temperature level of the second heat stream, 160° C. is provided, whereby heat transformer 21 pumps 20% of the waste heat of the turbine to pump temperature level with a degree of effectiveness of 90%.

Delivery Inlet Outlet Thermal KW Electrical Partial Increase in in Temp. in Temp. in output in effectiveness performance in delivery in effectiveness l/s ° C. ° C. kW in % kW l/s % 50 120 75 7,760.45 12 931.25 9.50 19.0% 100 120 75 15,520.90 12 1,862.51 19.01 19.0% 150 120 75 23,281.34 12 2,793.76 28.51 19.0% 50 120 75 7,760.45 14 1,086.46 9.29 18.6% 100 120 75 15,520.90 14 2,172.93 18.58 18.6% 150 120 75 23,281.34 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 15,520.90 16 2,483.34 18.14 18.1% 150 120 75 23,281.34 16 3,725.02 27.22 18.1%

In the arrangement shown in FIG. 9, a working fluid 6 is brought to a higher temperature level directly prior to a turbine 7 by a heat transformer 21. In detail, this is again an ORC cycle in which a low-temperature mass stream 1 heats a vaporizer 5 at an initial temperature level, whereby working fluid 6 is vaporized and after an additional heating by a warm side 22 of heat transformer 21 is fed to turbine 7. There, an expansion takes place on account of which work is performed that is transformed into electrical energy by an electric generator 31. After exiting turbine 7, expanded working fluid 6 is supplied to a heat exchanger 24, which has a heat stream connection with a cold end 23 of heat transformer 21. As a result, from expanded working fluid 6 exiting the turbine at an expansion temperature T5, a second heat stream is extracted which is being pumped to a pump temperature level above temperature T3 with the help of heat transformer 21. Thus, temperature T4 prior to entering turbine 7 is above temperature T1 of low-temperature mass stream 1 in the vaporizer.

The following values are in turn calculated for brine as low-temperature mass stream at an initial temperature level T1 of 120° C. as inlet temperature. As pump temperature level of the second heat stream, 160° C. is provided, whereby heat, transformer 21 pumps 20% of the waste heat of the turbine to pump temperature level with a degree of effectiveness of 90%. The outlet temperature T5 is 75° C.

Delivery Inlet Oulet Thermal KW Electrical Output Input Increase in in Temp. in Temp. in output in effectiveness output in heat in heat in effectiveness l/s ° C. ° C. kW in % kW kW kW % 50 120 75 7,760 12 931 1,366 1,093 14.1% 100 120 75 15,521 12 1,863 2,732 2,185 14.1% 150 120 75 23,281 12 2,794 4,098 3,278 14.1% 50 120 75 7,760.45 14 1,086.46 1,334.80 1,067.84 13.8% 100 120 75 15,520.90 14 2,172.93 2,669.59 2,135.68 13.8% 150 120 75 23,281.34 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 15,520.90 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%

REFERENCE Numbers

    • 1 Low-temperature mass stream
    • 2 deep well pump
    • 3 geothermal source
    • 4 first heat exchanger
    • 5 vaporizer
    • 6 working fluid
    • 7 turbine
    • 8 recuperator
    • 9 condenser
    • 10 fee pump
    • 11 pre-heater
    • 12 desorber
    • 13 separator
    • 14 steam phase
    • 15 watery phase
    • 16 high temperature recuperator
    • 17 constrictor
    • 18 low-temperature recuperator
    • 19 absorber
    • 20 first ORC cycle
    • 21 first heat transformer
    • 22 warm side of heat transformer
    • 23 cold side of heat transformer
    • 24 (first) heat exchanger
    • 25 second ORC cycle
    • 26 first heat transformer
    • 27 second heat transformer
    • 28 branch stream
    • 29 outflow
    • 29a downstream recirculation
    • 29b inlet (of ORC cycle)
    • 30 partial recirculation
    • 31 electric generator

Claims

1. Thermodynamic machine, particularly a low-temperature power plant, with at least one first cycle (20) for circulating a working fluid, whereby the first cycle (20) has at least one expansion machine (7) and at least one heat exchanger (24; 27) for feeding a first heat stream from a low-temperature mass stream (1) into the first cycle (20), whereby a first heat transformer (21; 26) is provided in heat stream connection with the first cycle (20), with a colder side (23) downstream of the expansion machine (7), and has a heat stream connection with a warmer side (22) with the low-temperature mass stream (1) or the first cycle (20).

2. Thermodynamic machine according to claim 1 further comprising a second cycle (25), particularly an ORC cycle, with a second heat transformer (26), which is located in the same way as the first heat transformer (21), sequentially to the first cycle (20), whereby the first (21) and the second heat transformer (26) respectively have a heat stream connection with the low-temperature mass stream (1) between the first (20) and the second cycle (25) with their warmer side (22).

3. Thermodynamic machine according to claim 1 further comprising a second cycle (25) that is fed by a branch stream (28) by the low-temperature mass stream (1) downstream of the first cycle (20), whereby the first heat transformer (21) with its warmer end (22) has a heat stream connection with the branch stream (28) upstream of the second cycle (25), and whereby a downstream feedback of the branch stream (28) is provided downstream of the second cycle (25) into the low-temperature mass stream (1).

4. Thermodynamic machine according to claim 1 further comprising a second cycle (25) that has a downstream feedback (29a) to an inlet (29b), which has a heat stream connection with the warmer end (22) of the first heat transformer (21).

5. Thermodynamic machine according to claim 1 further comprising at least one recirculation line (30) provided for feedback of a branch stream (28) of the low-temperature mass stream (1) downstream of the first cycle (20), whereby the warm side (22) of the first heat transformer (21) has a heat stream connection with the branch stream (28).

6. Thermodynamic machine according to claim 1 wherein the warm side (22) of the first heat transformer (21) in a section between a vaporizer (5) and expansion machine (7) has a heat stream connection with the first cycle (20).

7. Process for operating a thermodynamic cycle, particularly in a low-temperature power plant according to claim 1, with at least one cycle (20, 25), in which a working fluid (6) circulates, to which a first heat stream is fed by a low-temperature mass stream (1) at an initial temperature level, whereby after an expansion of the working fluid (6) in an expansion machine (7) releasing mechanical energy a second heat stream is extracted from the working fluid (6) at an expansion temperature level that is lower compared to the initial temperature level wherein the second heat stream in at least one heat transformer (21, 26) is pumped to a pump temperature level which is higher or equal to the initial temperature level and is at least partially fed back to low-temperature mass stream (1) and/or the at least one cycle (20, 25).

8. Process according to claim 7 wherein the second heat stream, which is raised to the pump temperature level, increases a temperature of the low-temperature mass stream (1) and/or a temperature of the working fluid (6) in the at least one cycle (20, 25).

9. Process according to claim 7 wherein the low-temperature mass stream (1) is increased by a partial feedback of a low-temperature mass stream outflow (29) that is heated by the second heat stream.

10. Process according to claim 7, wherein at least one cycle (20, 25) is operated as an organic Rankine cycle (ORC).

11. Process according to claim 7 wherein the at least one cycle (20, 25) is operated as a Kalina cycle.

12. Process according to claim 7 wherein at least two cycles, particularly two ORC cycles (20; 25), are sequentially fed by the low-temperature mass stream (1), whereby a feedback into the low-temperature mass stream (1) of the second heat streams of the cycles that is pumped to the respective pump temperature level takes place between the first cycle (20) and the second cycle (25).

13. Process according to claim 7 wherein at least two cycles (20, 25), particularly two ORC cycles, are provided, whereby from the low-temperature mass stream (1) downstream of the first cycle (20) a branch stream (28) for feeding a second cycle (25) is branched off, which downstream of the second cycle (25), is reunited downstream with the low-temperature mass stream (1), whereby the second heat stream that is pumped to the pump temperature level of the first cycle (20) is fed to the branch stream (29).

14. Process according to claim 7 wherein at least two cycles (20, 25), particularly two ORC cycles are provided, whereby the second heat stream of the first cycle (20) that is pumped to the pump temperature level is fed to an outflow of the second cycle (25), which is fed again to the second cycle (25) as inflow.

15. Process according to claim 7 wherein a branch stream (28) is branched off from the low-temperature mass stream (1) downstream of a cycle (20), which is heated by the second heat stream to the pump temperature level and is fed to the low-temperature mass stream (1) upstream of the cycle (20).

16. Process according to claim 15 wherein the branch stream (28) is dimensioned in such a way, that its pump temperature level prior to recirculation corresponds to the initial temperature level of the low-temperature mass stream (1).

17. Process according to claim 7 wherein the second heat stream is extracted downstream of the expansion machine (7) and after being pumped to the pump temperature level, is fed back into the cycle (20), particularly directly before the expansion machine (7).

18. Process according to claim 7 wherein a temperature of a heat transformer fluid is heated by the second heat stream and raised by at least two ejector-adsorbers to or above the pump temperature level to pump the second heat stream to the pump temperature level.

19. Process according to claim 7 wherein a heat transformer fluid heated by a second heat stream is at least essentially adiabatically compressed and thereby heated to or above the higher pump temperature level to pump the second heat stream to pump temperature level.

20. Thermodynamic machine, according to claim 1, with the at least one heat transformer (21; 26) being configured such that from a first mass stream with a first temperature level a second mass stream with a second temperature level is produced with the second mass stream being equal or less than the first mass stream and with the second temperature level being higher than the first temperature level.

Patent History
Publication number: 20090211251
Type: Application
Filed: Jan 22, 2009
Publication Date: Aug 27, 2009
Applicant: E-POWER GMBH (Langen)
Inventors: Helge B. Petersen (Frankfurt am Main), Ingo Schroter (Dreieich)
Application Number: 12/357,444
Classifications
Current U.S. Class: Process Of Power Production Or System Operation (60/645); Motive Fluid Energized By Externally Applied Heat (60/643)
International Classification: F01K 27/00 (20060101);