WO2018153981A1

WO2018153981A1 - Apparatus for converting thermal energy

Info

Publication number: WO2018153981A1
Application number: PCT/EP2018/054377
Authority: WO
Inventors: Arthur FLÜCK
Original assignee: Agronorm Vertriebs Gmbh
Priority date: 2017-02-24
Filing date: 2018-02-22
Publication date: 2018-08-30
Also published as: BR112019017292A2; EP3366894B1; US20200040771A1; CA3054250A1; EP3366894A1

Abstract

In an apparatus for converting thermal energy from a heat source into mechanical energy by means of a thermodynamic cycle using a working medium which is guided in the cycle and in that context experiences a changing pressure, wherein a saturated steam temperature value of the working medium is associated with the respective pressure, and an expansion device for expanding the working medium from an elevated pressure to a lower pressure, wherein after expansion to the lower pressure the working medium has a waste steam temperature, there is provided an adjustment device for setting the waste steam temperature to a defined waste steam temperature value above the saturated steam temperature value associated with the lower pressure.

Description

description

Device for converting thermal energy

Background of the invention

The invention relates to a device for converting thermal energy from a heat source into mechanical energy by means of a thermodynamic cycle with a working medium, which is guided in the cycle and thereby exposed to a varying pressure, wherein the respective pressure Sattdampftemperaturwert the working medium is associated, as well as a An expander for expanding the working fluid from an elevated pressure to a lower pressure, the working fluid having an exhaust temperature after expanding to the lower pressure. Furthermore, the invention relates to a corresponding method for converting thermal energy into mechanical energy.

Generic devices and methods are used for generating electrical energy from thermal energy to a so-called heat generation. As a thermodynamic cycle process usually a Clausi- us Rankine cycle is performed, which runs in steam power plants widely used with water as a working medium. The water is heated to about 600 ° C by means of high temperature heat sources, such as coal, natural gas, petroleum and nuclear energy. If an organic working medium is used instead of water, this is called the ORC process (Organic Rankine Cycle Process). Organic working media can have a much lower boiling point than water and at evaporate at lower temperatures. Therefore, ORC processes are used to recycle thermal energy from low temperature heat sources that have temperatures of 60 ° C to 200 ° C. Such heat sources are solar thermal or geothermal sources and waste heat from engines, industrial production processes and biogas plants. They can be used only insufficiently with conventional devices and methods.

In a thermodynamic cycle, the working medium undergoes periodic changes in its thermodynamic state variables such as temperature and pressure. Depending on the change in the state variables can be absorbed by the working medium energy from the environment or discharged into the environment. In this case, the working medium is therefore exposed to a changing pressure. It is first pressurized as a liquid working fluid and then vaporized and superheated by transferring thermal energy from the heat source. The result is a high-energy compressed working medium vapor, which can give its absorbed energy in an expansion of the increased pressure to a lower pressure by means of an expansion device again. The emitted energy can drive a generator to generate electrical energy in the form of mechanical energy.

After the expansion or the expansion process, the working medium vapor as the exhaust often has a proportion of liquid working medium. This proportion of liquid working medium lowers the efficiency and life of many expansion devices. One major reason for this is that most expansion devices, such as positive displacement machines and, in particular, vane cell expander, typically require oil lubrication with a lubricating oil. By means of the lubricating oil, a friction between movable components of the expansion device can be kept low and leakage gaps can be sealed in an expansion space leading the working medium. If, on the other hand, the lubricating oil accumulates with the proportion of liquid working medium, the lubricating properties and sealing capabilities of the lubricating oil decrease. Lower lubricating properties increase wear on the moving parts. Lower sealing capabilities lead to higher leakage losses of the working medium in the expansion device and thus to a lower efficiency. In addition, an additional heating energy for a subsequent thermal expulsion of liquid working medium from a recirculated

Lubricating oil necessary, which further reduces the efficiency.

It is the object of the invention to provide an apparatus and a method for a thermodynamic cycle with a working medium for converting thermal energy. In this case, the thermodynamic cycle should be optimized, in particular in terms of life and efficiency of the expansion device and the expansion process.

Inventive solution

This object is achieved according to the invention with a device for converting thermal energy from a heat source into mechanical energy by means of a thermodynamic cyclic process with a working medium which is guided in the cyclic process and exposed to an alternating pressure, the respective pressure being associated with a saturated steam temperature value of the working medium. and an expander for expanding the working fluid from an elevated pressure to a lower pressure, the working fluid having an exhaust temperature after expanding to the lower pressure. In this case, an adjusting device is provided for setting the evaporation temperature to a defined exhaust-steam temperature value above the saturated-steam temperature value associated with the lower pressure. By means of the device according to the invention, the working medium guided in the cyclic process is exposed to a changing pressure, which in particular periodically see changes is subject. In this case, each respective pressure to which the working medium is exposed, a saturated steam temperature value of the working medium associated. The saturated steam temperature value is the temperature value at which liquid working medium is in equilibrium with gaseous working medium. It depends on the respective pressure, which is called the saturated steam pressure value. The dependence on saturated steam pressure value and saturated steam temperature value can be represented as a phase boundary line between liquid and gaseous working medium in a vapor curve. The steam curve is specific to each working medium.

If the working medium has a temperature below the saturated steam temperature value of the respective pressure to which it is currently exposed, then the working medium is liquid. If the working medium has a temperature above the saturated steam temperature value of the respective pressure, then the working medium is gaseous. Upon cooling of the gaseous working medium, first condensation drops of the working medium form when the saturated steam temperature value is reached.

By means of the expansion device, the circulating process medium is to be expanded or expanded from an increased pressure to a lower pressure. During expansion, not only the pressure of the working fluid decreases to the lower pressure, but also the temperature of the working fluid. The temperature which the working medium has after expanding to the lower pressure is referred to as evaporation temperature.

According to the invention, an adjustment device is provided with which this evaporation temperature can be set to a defined exhaust-steam temperature value above the saturated-steam temperature value associated with the lower pressure. With such an adjusting device, the evaporation temperature value of the working medium can be adjusted in a targeted manner above the saturated steam temperature value associated with the lower pressure. The working medium, which has an evaporation temperature value above the saturated steam temperature, is gaseous. Condensation of the working medium from its gaseous to its liquid state during and after expansion can be reliably avoided. Thus, in the associated expansion device a consistently condensate-free working medium vapor is achieved without a proportion of liquid working medium. In and on the expander existing and usually liquid lubricant, such as in particular a lubricating oil can not be contaminated with liquid working fluid. The thus kept clean lubricant safely prevents friction between the movable components of the expansion device and seals the expansion space against leakage of working fluid reliably. In addition, a subsequent heating to expel an otherwise occurring liquid working fluid in the usually recycled lubricant is not necessary. Thus, both the efficiency and the life of the expansion device according to the device according to the invention compared to conventional generic devices are significantly improved.

The solution according to the invention initially surprises, since additional components and additional energy expenditure are required for the adjustment device. In addition, a higher Abdampftemperaturwert results in comparison to conventional generic devices. Such a higher evaporation temperature value results in an energy loss. It can be released according to comparatively less energy during expansion, which can be used as mechanical energy. According to the invention, however, it has surprisingly been found that the advantage of the consistently condensate-free working medium vapor in the expansion device far outweighs the additional energy expenditure and the resulting energy loss.

Furthermore, with the solution according to the invention, the condensation of the gaseous working medium after expansion can be avoided independently of various external and internal conditions of the thermodynamic cycle. No matter what thermal energy the heat source has and no matter what temperature and pressure the working medium has on entry into the expansion device, the Abdampftemperaturwert the working medium is always set above the Sattdampftemperaturwerts associated with the lower pressure. It is therefore the Abdampftemperaturwert defined as a function of the lower pressure, which may vary depending on the inlet temperature and inlet pressure of the working medium in the expansion device. The inlet temperature and the inlet pressure are often dependent on the thermal energy of the heat source. In addition, the Abdodenemperaturwert is defined as a function of the associated with the lower pressure saturated steam temperature value. This saturated steam temperature value is specific for each working medium, so that the condensation of the gaseous working medium after expansion, regardless of the type of working medium can always be reliably avoided. According to the invention, the defined evaporation temperature value is preferably kept constant above the saturated steam temperature value associated with the lower pressure. With the evaporation temperature value kept constant in this way, the expansion and a condensation following the expansion in the cyclic process can be carried out particularly uniformly without great temperature fluctuations. In particular, only a small amount of internal friction losses in the working medium and little external friction losses occur with respect to a line carrying the working medium. Otherwise occurring energy losses can be saved. In accordance with the invention, the defined Abdampftemperaturwert is between 2 K and 12 K, preferably between 4 K and 8 K, and more preferably between 5 K and 6 K above the Sattdampftemperaturwerts associated with the lower pressure. It has been found that even such a small difference between the Abdodenemperaturwert and the relevant Satt- vaporftemperaturwert sufficient to safely avoid condensation in the working medium vapor in the expansion to the lower pressure. For a larger difference would require setting a higher evaporative temperature value, which would cause unnecessary energy loss.

Furthermore, it is advantageous according to the invention to increase by means of the adjusting device a temperature of the working medium in such a way that the evaporation temperature has the defined exhaust-steam temperature value above the saturated-steam temperature value associated with the lower pressure. Such a temperature increase is easy to carry out. As is known, the working medium guided in a thermodynamic cyclic process is to be set in its liquid state of aggregation from a lower pressure to an elevated pressure. Thereafter, the working medium set under the increased pressure is isobaric to evaporate and overheat. The temperature of the working medium rises. Upon expansion of the compressed and superheated working medium vapor to the lower pressure, the temperature of the working medium vapor drops to the evaporation temperature.

According to the invention, the temperature of the working medium circulated in the cycle process is now to be increased after evaporation and before or during expansion by means of the adjusting device in such a way that the evaporation temperature then has the defined evaporating temperature value above the saturated steam temperature value associated with the lower pressure.

According to the invention, the temperature of the working medium within the expansion device is to be increased by means of the adjusting device. Thus, the temperature during the expansion process can be increased, which is more energy efficient than a temperature increase of the superheated working medium vapor before expanding. In particular, the temperature of the working medium is to increase towards the end of the expansion process. Towards the end of the expansion process, the temperature of the relaxing working medium vapor is lower than at the beginning or in the middle of the explosion. pansionsprozesses. Thus, the temperature of the working medium can be increased energy-saving from a relatively low temperature to the required temperature value with which the defined Abdampftemperaturwert is to be achieved after expansion.

Furthermore, the adjusting device according to the invention advantageously comprises a steam feed for supplying steam to the working medium, wherein the steam is in particular superheated steam. The vapor-forming vapor molecules move quickly and transmit their motion in a collision to the working medium / vapor molecules correspondingly fast, which reduces the temperature of the vapor

Working medium vapor increased accordingly fast. In addition, depending on the temperature and amount of supplied steam, the temperature of the working medium vapor can be adjusted very targeted to the defined Abdampftemperaturwert. If the steam is overheated, the temperature increase is even faster.

Preferably, the steam supply is adapted to supply the steam in the expansion device, in particular after supplying the guided in the cycle process working medium vapor in the expansion device. Thus, the temperature of the working medium vapor can be increased energy-saving during expansion. A preferably leading towards the end of expansion in the expansion device steam supply is particularly energy-saving according to the above-described embodiments. In addition, the steam supply into the expansion device has the advantage that the supplied steam can expand as additional steam. This results in an additional expansion of the additional steam, which can be delivered in the form of additional mechanical power to the expansion device. Higher performance and associated higher efficiency of the expansion device can be achieved, which increases the efficiency of the entire device. Furthermore, according to the invention, the vapor is advantageously a vapor of the working medium. Thus, despite the supply of additional steam, the working medium remains a pure working medium which is not contaminated with the vapor of another medium. Preferably, the vapor of the working medium comes from the same cycle as the working medium vapor itself, which is to be led into the expansion device at the beginning of expansion. It is energy and component saving only a single steam generation needed, for which particularly efficient thermal energy can be transferred from the heat source.

According to the invention, the expansion device is designed as a positive-displacement machine for passing the working medium into at least one expansion space or volume space that enlarges when passing through. In this case, an inlet for the admission of the set under the increased pressure working medium vapor is provided in the expansion space. The recessed working medium vapor then displaces a component which limits the expansion space. As a result, the expansion space is increased and at the same time moves the component for performing mechanical work. Increasing the expansion space causes expansion of the working medium vapor from the increased pressure to the lower pressure.

In such a positive displacement machine, the working medium vapor may be passed through the inlet and the additional steam through a steam supply positioned between the inlet and the outlet into the expansion space. In this case, the working medium vapor can expand when passing through the enlarging expansion space and can be reheated during the enlarging expansion space by means of the supplied steam. Along with the supplied steam, the reheated working medium vapor may continue to expand toward the outlet. Especially targeted, the steam supply can be designed in such a positive displacement machine with two or more expansion spaces. The steam supply may in this case be designed so that additional steam is to be directed into the expansion space in a targeted manner when the expansion space has reached a desired size. According to this size is then there correspondingly expanded and cooled working medium vapor, which is then specifically to heat. The heated working medium vapor can then continue to expand in the expanding expansion space until, with the expansion space, an outlet is reached, from which the working medium vapor and the additional steam can escape. In this case, at least the inlet for the working medium vapor is spatially arranged so far away from the steam supply that an expansion space located at the inlet is spatially separate from an expansion space located in the steam supply. Preferably, the outlet is arranged spatially far enough away from the steam supply that an expansion space located at the outlet is spatially separate from the expansion space located in the steam supply. This allows a particularly targeted increase in temperature during expansion in a defined expansion zone. The defined expansion zone corresponds to the size of the expansion space at the steam supply.

Moreover, according to the invention, advantageously, by means of the adjusting device, a back pressure is to be generated on the working medium in such a way that the steaming temperature has the defined steaming temperature value above the saturated steam temperature value associated with the lower pressure. A structure of such a back pressure is particularly energy-efficient.

With the counterpressure of this kind, the lower pressure is initially not reached during expansion, but rather a lower pressure which is increased in accordance with the counterpressure. The increased lower pressure is associated with a correspondingly increased saturated steam temperature value of the working medium. By means of the back pressure of the working medium vapor is initially maintained at the increased lower pressure and thereby has an evaporation temperature which corresponds to this increased saturated steam temperature value. Upon further expansion, the increased lower pressure corresponding to the backpressure is then to be restenized or expanded to the lower pressure. After the residual expansion, the working medium vapor has an evaporation temperature which corresponds to the defined exhaust-steam temperature value above the saturated-steam temperature value associated with the lower pressure. Condensation of the working medium vapor is safely avoided throughout the expansion process. For this purpose, an expansion device is preferably provided for expanding the working medium from an elevated pressure to a lower pressure, in which the lower pressure can be achieved by means of a two-stage expansion process. The increased pressure is to be expanded in a first expansion stage, first by means of the generation or build-up of back pressure to a first lower pressure. Thereafter, the first lower pressure in a second expansion stage is to be expanded to a second lower pressure, the second lower pressure corresponding to the above-mentioned lower pressure after expansion. In this case, the first and the second expansion stage can take place in a single expansion device. Particularly preferably, the first expansion stage in a first expansion device and the second expansion stage are carried out separately in a second expansion device. The first expansion device is designed in particular with a positive displacement machine and the second expansion device structurally simple as a line element within a line carrying the working fluid. The first and second expansion means then represent the total expansion device.

Furthermore, the adjusting device according to the invention advantageously for generating the back pressure on the working fluid, a blocking element, in particular with a valve for selectively opening and closing a working medium leading line is designed. By means of the blocking element, a working medium flow or working medium flow of the working medium conveyed in the cyclic process can be shut off in a structurally particularly simple and rapid manner. After such shut-off, the desired back pressure builds up on the working medium. The back pressure can be broken down again with short reaction times if necessary, by the blocking element is designed with a valve that can be easily reopened.

Preferably, the blocking element is arranged within the expansion device between see the first and second expansion means, whereby then the described two-stage expansion process is possible.

In addition, in accordance with the invention advantageously the working medium is guided in a circulation direction and in the direction of circulation after the expansion device, a condensation device for condensing the expanded working medium is provided, wherein the adjusting means a temperature measuring element for measuring a temperature of the working medium in the direction of circulation after expanding and before condensing and / or a pressure measuring element for measuring the pressure of the working medium in the circulation direction after the expansion and before the condensation. With such a temperature measuring element and / or pressure measuring element, a control device is provided, with which the adjusting device is to be regulated as a function of the measured temperature and / or the measured pressure. In this way, the steaming temperature can always be set to the desired defined steam temperature value as required and reliably with the adjusting device.

In this case, the temperature measuring element measures in particular the evaporation temperature of the working medium after expansion. The evaporation temperature is also dependent on the temperature of an inlet vapor of the working medium when entering the expansion device. In addition, the temperature of the working medium before condensing or the condensation temperature can be determined. The con- In this case, the condensation temperature value corresponds in particular to the saturated steam temperature value associated with the lower pressure. With the pressure measuring element, a currently valid saturated steam pressure value or condensation pressure value of the working medium can be measured, in particular shortly before condensation, which is dependent on a cooling capacity of the condensation device.

Furthermore, the invention is directed to a method for converting thermal energy from a heat source into mechanical energy by means of a thermodynamic cyclic process, with a working medium which is guided in the cyclic process and thereby exposed to an alternating pressure, wherein the respective pressure Saturated steam temperature value of the working medium is associated, and a step of expanding the working medium of an increased pressure to a lower pressure, wherein the working medium after expanding to the lower pressure has an evaporation temperature. The evaporation temperature is set to a defined Abdampftemperaturwert above the lower pressure associated Sattdampftemperaturwerts.

The advantages of such a method according to the invention will become apparent from the advantages already described in the description of the device according to the invention.

Brief description of the drawings

Exemplary embodiments of a solution according to the invention will now be explained in more detail with reference to the attached schematic drawings. It shows:

1 is a simplified process schematic of a prior art thermal energy conversion apparatus;

2 is a schematic pressure (log) -Enthalpie diagram of the thermodynamic see cycle process of FIG. 1,

3 shows a vapor curve of a working medium guided in a cyclic process, 4 shows the detail IV according to FIG. 1 of a first embodiment of a device according to the invention, FIG.

5 is a schematic pressure (log) -Enthalpie diagram of the thermodyna mixing cycle process of FIG. 4,

6 shows a cross section of a displacement machine of the device according to FIG. 4, FIG.

Fig. 7 shows the detail IV of FIG. 1 of a second embodiment of a device according to the invention and

8 is a schematic pressure (log) -Enthalpie diagram of the thermodyna mixing cycle process Fig. 7th

Detailed description of the embodiment

In the figures, a device 10 and an associated method 12 for converting thermal energy from a heat source 14 are shown. The device 10 forms a closed system of a process plant in which a thermodynamic cycle 16 is to be carried out by means of a working medium guided in the cycle 16.

The illustrated thermodynamic cycle 16 is a modified Organic Rankine cycle (ORC) process in which the working medium is an organic working medium. In the present case, the working medium is designed with ammonia, preferably with anhydrous ammonia (Nhb, R 717) in a concentration of more than 99, 6 percent by mass. With such an almost pure ammonia, the physical and thermodynamic properties of ammonia can be exploited without interfering with other substances. Thus, liquid ammonia has a high enthalpy of vaporization, with which relatively much energy must be expended to convert ammonia from its liquid to its gaseous state. Accordingly, a corresponding amount of energy can be stored in the gaseous ammonia and then converted into mechanical energy upon expansion. As a heat source 14 are low-temperature heat sources. In this case, the heat source 14 may be a single heat source 14 or with two different heat sources 14 and 17 designed. In the illustrated embodiments, two different heat sources are utilized in which the heat source 14 has a lower temperature than the heat source 17. In this case, the heat source 14 is an engine waste heat and the heat source 17 is an exhaust heat of an internal combustion engine of a combined heat and power plant.

In a collection container 18 belonging to the cycle 16, the working medium is provided in the form of a pressure-liquefied gas. In this case, the working fluid is under a pressure that represents a lower pressure 20, a lower pressure level of the thermodynamic cycle process 16. Starting from the collecting container 18, a line 22 leads the working medium in a circulation direction 24 to a pressure increasing device 26. With the pressure increasing device 26, the pressure to which the working medium is subjected to increase from the lower pressure 20 to a pressure which is increased Pressure 28 represents an upper pressure level of the cycle 16.

Subsequently, in the circulation direction 24, the liquid working medium is pumped by the pressure increasing device 26 through the line 22 to a heat transfer device 30. The heat transfer device 30 comprises a first heat exchanger 32 and a series-connected second heat exchanger 34. The first heat exchanger 32 is heat-transmitting coupled by means of a guided through a line 36 transmission medium with the heat source 14. Accordingly, the second heat exchanger 34 is coupled to the heat source 17 by means of a transmission medium carried by a line 38.

Between the two heat exchangers 32 and 34, a separator 40 with a lower space area 42 and an upper space area 44 is arranged. In the upper space region 44, the liquid working medium by means of the line 22nd guided. The liquid Arbeitsmediunn separates from any existing gaseous working fluid and sinks into the lower space portion 42. From there, a line 46 leads the thus separated liquid working fluid into the first heat exchanger 32, which serves as a preheater and evaporator. There, the liquid working medium is preheated by transferring thermal energy from the first heat source 14 and largely evaporated. Such produced working medium vapor is a wet steam. This means that even small drops and finely distributed liquid working medium are present as condensate in the gaseous working medium. The wet steam is guided out of the first heat exchanger 32 through a line 48 into the upper space region 44 of the separator 40. In this case, the condensate fraction sinks into the lower space region 42 and collects there as a liquid working medium, while in the upper space region 44 only gaseous working medium remains. So it can be generated a particularly dry gaseous working medium. The liquid working medium passes from the lower space region 42 through the line 46 back into the first heat exchanger 32 for reheating.

With the separator 40, the leading in its upper space portion 44 lines 22 and 48 and the leading from the lower space portion 42 line 46 evaporation according to a thermo-siphon principle is possible. This principle is based on the fact that during evaporation in the first heat exchanger 32, the density of the working medium located there is reduced due to the wet steam formed. Thus, the wet steam forced through the line 48 into the separator 40. Furthermore, always flows just as much liquid working fluid from the lower space portion 42 of the separator 40 through line 46 into the heat exchanger 32, which is just needed for evaporation. In the separator 40, an unillustrated level controller is provided with which the pressure increasing device 26 is to be regulated so that only as much working fluid is pumped to the first heat exchanger 32, which can also be evaporated. From the separator 40, the gaseous working medium from the upper space region 44 is guided through a line 50 into the second heat exchanger 34. The second heat exchanger 34 serves as a superheater with which the gaseous working medium is to be overheated when transferring thermal energy from the heat source 17. The superheated working medium vapor is then passed from the second heat exchanger 34 through a conduit 52 by means of an inlet valve 54 in an expansion device 56.

With the expansion device 56, the superheated working medium vapor from the increased pressure 28 to expand to the lower pressure 20, at the same time the temperature of the working medium decreases. The released energy is transmitted as mechanical energy to the expansion device 56, which serves as a drive unit for a coupled to the expansion device 56 generator 58 for generating electrical energy.

In the present case, a further expansion device connected in parallel to the expansion device 56 is provided into which the compressed and superheated working medium vapor is guided by means of an associated further inlet valve. For a better overview, the further expansion device with its associated components is designated by the same reference numerals as the expansion device 56. With such a parallel connection of the expansion devices 56, a particularly uniform expansion over time of the superheated working medium vapor without large pulsations is possible over time. If necessary, in addition, a larger amount of working medium steam can be expanded. Thus, a total of a uniform and high performance can be removed from the cycle 16. To improve this effect, more than two parallel expansion devices 56 may be provided.

The expanded working medium vapor is led out in the circulation direction 24 after the expansion device 56 through a line or exhaust steam line 60 from the expansion device 56 and through a condensation device 62 headed. With the condensation device 62, the expanded working medium vapor is cooled and condensed. The condensed working medium is passed into the collecting container 18, which is arranged in the line 22 in the direction of circulation 24 after the condensation device 62. Condensation of the thermodynamic cycle 16 is closed and can be repeated as often as necessary.

Furthermore, the device 10 has an oil supply circuit 64, each with an oil supply line 66, through which an oil is to be guided by means of a respective associated oil inlet valve 68 into the respectively associated expansion device 56. The oil serves to seal and lubricate components of the expander 56. During expansion of the working medium vapor, the oil in the expander 56 may enter the working medium vapor. Therefore, the expanded working medium vapor is guided together with the oil from each expansion device 56 through the associated exhaust steam line 60 in a respective associated Olabscheider 70. With the oil separator 70, the oil is to be separated from the expanded working medium vapor. For this purpose, a separating element 71 is designed as a mechanical oil separator in the oil separator 70 at the top. The separating element 71 separates the oil as liquid from the expanded working medium vapor as gas mechanically and due to different densities of liquid and gas.

The expanded working medium vapor thus purified is led from the oil separator 70 through the exhaust steam line 60 further in the cyclic process 16 to the condensation device 62.

The separated oil is led from each oil separator 70 through an associated oil discharge line 72 into an oil collecting tank 74. In this case, the separated oil may contain a proportion of liquid working medium, which has formed during expansion of the working medium vapor in a conventional manner. To remove this proportion of liquid working medium is in the oil collecting ter 74 a Olheizer 76 is provided. With the Olheizer 76, the separated oil is heated for so long and until the proportion of liquid working medium has almost completely evaporated or expelled from the oil. A resulting working medium vapor is guided by means of a steam line 78 from the Ölsam- melmel 74 in the direction of circulation 24 between the oil separator 70 and the condenser 62 back into the exhaust steam line 60 and thus into the cycle 16.

In addition, an oil pump 80 is arranged in the oil feed line 66, with which the separated oil, which has been cleaned of liquid working medium, is led through the oil feed line 66 again into the expansion device 56. In addition, the oil heater 76 comprises a heating medium-carrying heating circuit line 82, which is coupled to transmit heat to the second heat source 17. 2 shows a schematic pressure (log) enthalpy diagram of the thermodynamic cycle 16 of the method 12, which can be carried out by means of the device 10 according to FIG. In this case, the logarithm of the pressure 83 is plotted on the ordinate axis and the enthalpy 84 is plotted on the abscissa axis. The illustrated arcuate line represents a phase boundary line 85 of the working medium. As long as the phase boundary line 85 increases, this is the boiling line at which a transition from saturated liquid working medium to wet steam takes place. If the phase boundary line 85 falls, it represents the dew point, which marks a transition of the wet steam to a saturated working medium vapor. In the case of such a transition, the steam is also referred to as saturated steam. A surface enclosed by the phase boundary line 85 and the axis of abscissa is a wet steam region 86 of the working medium, in which working medium vapor as gaseous phase and liquid working medium as liquid phase are present at the same time. Starting from the liquid working medium which is under the lower pressure 18, in a method step or step 88 of the pressure increase set the working fluid by means of the pressure increasing device 26 under the increased pressure 28. Ammonia is set from a lower pressure 18 of about 8.4 bar and a temperature of about 23 ° C under an elevated pressure 28 of about 37 bar and a temperature of about 30 ° C.

All pressure values given here are to be understood as absolute pressure values.

With the first heat exchanger 32, in a step 90 of the preheating, the working medium under the increased pressure 28 is heated isobarically to an evaporation temperature value associated with the increased pressure 28. For ammonia, this value is around 76 ° C. Subsequently, in a step 92 of the evaporation, the still liquid, preheated to the evaporation temperature value working medium isobaric evaporated. During step 92, the majority of the thermal energy is supplied to the working medium. During evaporation, the temperature of the working medium remains the same.

Subsequently, by means of the second heat exchanger 34, in a step 94 of overheating, the working medium vapor generated in step 92 is isobarically superheated to an end temperature. The final temperature for ammonia is about 120 ° C.

The thus superheated working medium vapor is adiabatically expanded as superheated ammonia gas in a step 96 of expansion by means of the two expansion devices 56 connected in parallel. Adiabatic or adiabatic means that no heat is exchanged with the environment during expansion. During expansion, the actual conversion of thermal energy into mechanical energy takes place. In this case, the working medium entering the expansion device 56 has the increased pressure 28 as the inlet pressure and the temperature of the superheated working medium vapor as the inlet temperature. The working medium emerging from the expansion device 56 then indicates the lower lower pressure 20 as Abdampfdruck and an evaporation temperature, which is lower than the inlet temperature. Entering ammonia has the increased pressure 28 of about 37 bar and the inlet temperature of about 120 ° C and exiting ammonia has the lower pressure 20 of about 8.4 bar and the evaporation temperature of about 23 ° C. In this case, a liquid fraction in the exhaust steam is contained in the exiting working medium vapor, since both the inlet temperature and the evaporation temperature are subjected to certain tolerances. Already at a slightly lower inlet temperature condensate forms in the exhaust steam. The then reached evaporation temperature, ie the end point of the step 96 of the expansion, is located in the wet steam region 86.

Subsequently, the expanded working medium leaving the expansion device 56 is isobarically condensed in a step 98 of condensation by means of the condensation device 62 and thus again reaches its initial state in the cyclic process 16.

FIG. 3 shows a saturation vapor pressure curve or vapor pressure line or vapor curve 100 of the working medium guided in the cyclic process 16, in this case the vapor curve 100 of ammonia. The temperature is plotted on the ordinate axis and the pressure on the abscissa axis. The curved line represents the vapor curve 100 of the working medium and is the phase boundary line between liquid and gaseous working medium. Accordingly, it can be read on the steam curve 100 which saturated steam temperature value is associated with a respective pressure of the working medium at which gaseous working medium begins to condense. The lower pressure 20 includes the saturated steam temperature value 102, which for ammonia has a value of 23 ° C. at a lower pressure 20 of 8.4 bar.

4 and FIG. 7 show a section of the device 10, in which, in contrast to the device 12 according to FIG. 1, an adjusting device 104 for setting the evaporation temperature of the working medium after the step 96 of FIG. is provided. By means of the adjusting device 104, the Abdampftem- temperature is set to a defined Abdampftemperaturwert 106 above the lower pressure 20 associated Sattdampftemperaturwerts value 102. The defined Abdampftemperaturwert 106 is between 4 K and 8 K above the lower pressure 20 associated Sattdampftemperaturwerts value 102.

4, the adjusting means 104 comprises a steam feed 108 for supplying steam during the step 96 of expanding into each expansion means 56. Such feeding of steam is also referred to as an intermediate injection. With such a steam supply 108, the temperature of the working medium vapor during expansion can be increased such that the evaporation temperature of the working medium after the step 96 has the defined Abdodenemperaturwert 106. For this purpose, the steam supply 108, each with a steam supply line 1 10 and an additional inlet valve 1 12 arranged therein, which lead in the direction of circulation 24 after the inlet valve 54 into the associated expansion device 56. In addition, the steam supply line 1 10 is fluidly connected to the line 52. Thus connected, the superheated by means of the second heat exchanger 34 working medium vapor from the line 52 through the additional

Inlet valve 1 12 are passed into the expansion device 56. In this case, the superheated working medium vapor is passed into the expansion device 56 at an advanced stage, in particular toward the end of the step 96 of expansion.

Furthermore, the adjusting device 104 according to FIG. 4 in each case comprises a temperature measuring element 1 14 belonging to each expansion device 56, which is arranged in the circulation direction 24 after expansion shortly after each oil separator 70. Arranged in this way, the exhaust-steam temperature of the working medium can be determined by means of the temperature measuring element 14. In addition, one is in the direction of circulation 24 arranged shortly before the condensation device 62 Temperaturnneselennent 1 16 and a shortly before arranged pressure measuring element 1 18 provided.

The condensing device 62 associated pressure measuring element 1 18 and temperature measuring element 1 16 are each coupled to the respective expansion device 56 to a temperature measuring element 1 14. For this purpose, the measured values can each be transferred to a control device 120 belonging to each expansion device 56. The control device 120 then opens and closes the additional inlet valve 1 12 for supplying steam into the expansion device 56 as a function of the measurement result.

For this purpose, in each case a pressure value of the lower pressure 20 currently valid in the cycle 16 is measured shortly before the condensation device 62 with the pressure measuring element 1 18. The lower pressure 20 may vary depending on the inlet pressure value of the increased pressure 28 into the expansion device 56 and depending on the condensation temperature of the condensation device 62.

According to the measured pressure value of the lower pressure 20, according to the steam curve 100 stored in the control device 120, the corresponding currently valid saturated steam temperature value 102 results. Depending on the valid saturated steam temperature value 102, the additional inlet valve 12 is adjusted by means of the control device 120 as long and / or until the temperature measuring element 1 14, the defined Abdampftemperaturwert 106 is measured. Depending on the duration and opening width of the inlet valve 12, a corresponding amount of additional steam is thus supplied, until the defined exhaust-steam temperature value 106 is reached and, in particular, kept constant.

Alternatively or additionally, the temperature value of the working medium upstream of the condensation device 62 can be determined with the temperature measuring element 16. This measured temperature value corresponds to a currently valid

Saturated steam temperature value 102, which depends on a cooling capacity of the condensation direction 62 is dependent. The cooling capacity may vary according to the temperature of the coolant. In particular, when the coolant is structurally particularly simple and inexpensive air from the environment, the cooling capacity is directly dependent on the prevailing outside temperature. Depending on the measured, currently valid saturated steam temperature value 102, the additional inlet valve 12 is opened by means of the control device 120 for as long and / or until the defined temperature of the exhaust steam 106 is measured with the temperature measuring element 14. Depending on the measured, currently valid saturated steam temperature value 102, the associated saturated steam pressure value can be determined in accordance with the steam curve 100. This saturated steam pressure value corresponds to the applicable lower pressure 20.

In FIG. 5, in contrast to the diagram according to FIG. 2, additionally lines are entered which correspond to the isotherms, ie lines of the same temperature. In this case, 122 designates the 20 ° C isothermal 122 and 124 the 30 ° C isotherm 124. In addition, it can be seen along the step 96 how the temperature of the working medium increases when supplying superheated working medium vapor towards the end of expansion by means of the steam supply 108 , Upon reaching the lower pressure 20, the working fluid has the defined Abdampftemperaturwert 106 above the lower pressure 20 associated Sattdampftemperaturwerts value 102. Thus, the end point of step 96 is relatively far outside the wet steam region 86, so that condensate in the exhaust steam is reliably avoided. For ammonia, the defined Abdampftemperaturwert 106 about 28 ° C and is thus about 5 K above the saturated steam temperature value 102 of about 23 C at the lower pressure 20 of about 8.4 bar.

Fig. 6 shows the expansion device 56 used in the device 10 according to Fig. 4 and designed with a rotary vane machine as a displacement machine. The rotary vane machine is a rotary piston expander, which sets a rotary piston compressor operates and in the present case is a vane cell expander.

Such a vane cell expander has a ring housing 126 with an inlet 128 and an outlet 130. The inlet 128 serves to admit the working medium vapor under increased pressure 28 and the outlet 130 to discharge the expanded working medium vapor. In this case, each flow direction of the working medium vapor is indicated by a flow arrow. The ring housing 126 is formed with a cylindrical hollow cylinder whose inner circumferential surface forms an inner annular wall 132. In the ring housing

126 eccentrically to the axis of the hollow cylinder, a rotary piston 134 is rotatably mounted centrally about a shaft 136. The rotary piston 134 comprises along its longitudinal extent eight grooves 138, in each of which an associated slider 140 is mounted radially displaceable back and forth.

To limit the ring housing 126, two opposite, not shown boundary surfaces are provided in the axial direction. The two boundary surfaces, together with the rotary piston 134, the inner annular wall 132 and the eight slides 140, delimit eight cells 142, each with a variable volume 144.

The individual variable volume 144 is formed in that the respective slide 140 is pressed sealingly against the annular wall 132 in the course of a rotation by acting centrifugal forces. Characterized in that the rotary piston 134 is mounted eccentrically in the annular housing 126, during the rotational movement of the distance between the rotary piston 134 and the annular wall 132. Because of this, the respective slide 140 is rotated during rotation in the associated groove 138 back and forth. At an increasing distance of the slider 140 is pushed out of the associated groove 138 until the maximum of the distance and thus the volume maximum of the volume 144 is reached. Subsequently, the distance decreases again and the slider 140 is sliding along pushed on the annular wall 132 so to speak of the annular wall 132 in the associated groove 138 until the minimum of the distance and thus the volume minimum of the volume 144 is reached. The variable volume 144 increases during the rotational movement from the inlet 128 to the outlet 130, so that when passing the working medium vapor under increased pressure 28, this working medium vapor is expanded. During expansion, the working medium vapor presses in the direction of rotation against a respective slide 140 so that the rotational movement is set in motion and held. Thus, the shaft 136 is driven, which in turn drives the generator 58 for generating electric current.

The variable volume 144 of each cell 142 is dependent in its size on a rotational angle associated with the rotational movement, which can be divided into individual successive rotational angle zones. Thus, the volume 144 in a rotational angle zone 146 has its minimum volume. At the inlet 128, the volume 144 in a rotation angle zone 148 increases slowly during the inflow of the compressed working medium vapor and is expanded in the rotation angle zone 150 up to its maximum volume. When relaxing, the temperature of the working medium vapor decreases. Before reaching the maximum volume, superheated working medium vapor is fed into or interjected by the steam supply line 110 through the steam supply 108 into each cell 142. Thanks to the intermediately injected working medium vapor, the temperature of the relaxing working medium vapor is increased so far that the evaporation temperature of the working medium vapor leaving the outlet 130 has the defined evaporation temperature value 106. The thus moderately heated and relaxed at the maximum volume Arbeitsmedium- steam then flows in a rotational angle zone 152 except for a small residual volume from the outlet 130 from. The working medium vapor exiting through the outlet 130 of each cell 142 is the working medium vapor admitted through the inlet 128 together with the intermediate injected working fluid. mediunn-Dannpf. The residual volume remains in the respective cell 142 and is compressed via the rotational angle zone 146 until at the inlet 128 again compressed working medium vapor flows in. This process repeats periodically. The expansion ratio, that is, the ratio between the volume 144 at the inlet 128 and the volume 144 at the outlet 130 is set to 1 to 3 to 1 to 4 and thus specially adapted for the working medium ammonia.

For sealing and lubricating the radial and axial slide gaps occurring between the respective groove 138 and the associated slide 140, the oil supply line 66 is provided for supplying oil (FIG. 4). With the oil, the running surface of the slider 140 along the annular wall 132 is especially sealed and lubricated. The oil mixes when expanding the working medium vapor as already described with the working medium vapor and is discharged through the exhaust steam line 60 through the oil separator 70 from the expansion device 56 again. In the oil separator 70, the oil separates again to working medium vapor. Because a proportion of liquid working medium is reliably prevented in the separated oil by means of the devices 10 according to FIGS. 4 and 7, the otherwise required oil heater 76 according to FIG. 1 can be omitted cost-effectively and energy-saving.

In the apparatus 10 according to FIG. 7, by means of the adjusting device 104, a counter-pressure to the working medium is to be produced in such a way that the evaporation temperature of the expanded working medium has the defined exhaust-steam temperature value 106 above the saturated-steam temperature value 102 associated with the lower pressure 20. For this purpose, a valve or exhaust control valve 154 is provided as a blocking element 156, with which the exhaust steam line 60 can be shut off. Thus shut off, a reduction of pressure of the working medium in the circulation direction 24 is prevented. The working medium is accumulated in the exhaust steam line 60 counter to the direction of circulation 24 or the flow direction, whereby the desired Counterpressure can be generated. With an opening of the exhaust control valve 154, the back pressure can be reduced again when needed.

For regulating the exhaust control valve 154, the adjusting device 104 of the device 10 according to FIG. 7 comprises the temperature measuring element 1 14 after expanding in the circulation direction 24 shortly before the exhaust control valve 154. After the exhaust control valve 154 and just before the condensation device 62, the temperature measuring element 1 16 is arranged with where the currently valid saturated steam temperature value 102 of the working medium, as described for FIG. 4, can be determined. In addition, the pressure measuring element 1 18 in the direction of circulation 24 after the exhaust control valve 154 and shortly before the condensation device 62 is provided. With the pressure measuring element 1 18, a pressure value of the lower pressure 20 that is currently valid in the cycle 16 can be measured shortly before the condensation device 62 in accordance with the statements relating to FIG. 4.

The temperature measuring elements 1 14 and 1 16 and the pressure measuring element 1 18 are coupled to transmit data to the control device 120, which closes or opens the exhaust control valve 154 depending on the measurement result. In accordance with the measured pressure value of the lower pressure 20 and thus of the currently valid saturated steam pressure, the corresponding currently valid saturated steam temperature value 102 results according to the steam curve 100 stored in the control device 120. Depending on the valid saturated steam temperature value 102, the exhaust control valve 154 is activated by the control device 120 as long and / or closed so far, until with the temperature measuring element 1 14 or 1 16 the defined Abdampfempera- tured value 106 is measured.

In FIG. 8 it can be seen that the exhaust steam pressure is raised to a first lower pressure 158 by means of the exhaust control valve 154, which is slightly higher than the lower pressure 20. Thus, the superheated working medium vapor is concentrated by means of the expansion device 56 first expansion stage 160 initially relaxed to the first lower pressure 158. For ammonia, this is the first lower pressure 158 about 12 bar. This first lower pressure 158 is according to the steam curve 100 a saturated steam temperature of about 33 ° C belonging.

In the recirculation direction 24 after the exhaust control valve 154, the first lower pressure 158 is then restressed in a second expansion stage 162 to a second lower pressure corresponding to the lower pressure 20. The lower pressure 20 is the condensation pressure of the working medium, that is, the pressure at which the working fluid is condensed in the condenser 62. It can be seen from FIG. 8 that the temperature of the working medium after the residual expansion at the lower pressure 20 has the defined exhaust-steam temperature value 106 above the saturated-steam temperature value 102 associated with the lower pressure 20. The end point of step 96 is thus outside of the wet steam region 86, whereby condensation of the working medium vapor is prevented.

In a further embodiment, not shown, the pressure-increasing device 26 is designed with a steam pump. The steam pump is used to increase the pressure on the working fluid under the action of steam on the working fluid. For this purpose, the steam pump is heat-transmitting coupled by means of the heat transfer device 30 and a Dampfüberführmittels to the heat source 14. The working medium vapor formed with the heat transfer device 30 is partly to be transferred from the vapor transfer means into the vapor pump. Thus, the thermal energy of the heat source 14 can be particularly well exploited and also an otherwise required electrical energy for the Druckhohungsreivchtung 26 can be saved. Overall, the efficiency can be increased again.

In addition, by means of the solution according to the invention, a drying process for drying a substance can also be optimized in terms of energy. For this purpose, released energy of step 98 of condensing the working medium is coupled in an energy-transmitting manner to the drying process. In addition to drying the substance used as further heat sources 14 and 17, the engine waste heat and the waste heat of a combustion process of fuel, in particular biogas.

LIST OF REFERENCE NUMBERS

10 Device for converting thermal energy

12 procedures

14 heat source

16 thermodynamic cycle

17 heat source

18 collection containers

20 lower pressure

22 line

24 cycle direction

26 pressure increasing device

28 increased pressure

30 heat transfer device

32 first heat exchanger

34 second heat exchanger

36 line

38 line

40 separators

42 lower room area

44 upper room area

46 line

48 line

50 line

52 line

54 inlet valve

56 expansion device

58 generator

60 line or exhaust steam line 62 condensation device

64 oil supply circuit

66 Olzuführleitung or feeder

68 oil inlet valve

70 oil separator

71 separating element

72 oil discharge line

74 oil sump

76 oil heater

78 steam line

80 oil pump

82 heating circuit line

83 logarithm pressure

84 enthalpy

85 phase boundary line

86 wet steam area

88 step of increasing pressure

90 step of preheating

92 step of evaporation

94 step of overheating

96 step of expanding

98 step of condensing

100 steam curve

102 saturated steam temperature value

104 adjustment device

106 defined Abdodenemperaturwert

108 steam supply

1 10 steam supply line

1 12 inlet valve

1 14 Temperature measuring element

1 16 temperature measuring element Pressure sensing element

control device

Isotherm at 20 ° C

Isotherm at 30 ° C

ring case

inlet

outlet

inner ring wall

rotary pistons

wave

groove

pusher

cell

volume

Rotational angle zone

Valve or exhaust control valve

blocking element

first lower pressure first expansion stage second expansion stage

Claims

claims

1 . Device (10) for converting thermal energy from a heat source (14, 17) into mechanical energy by means of a thermodynamic cycle (16)

- A working medium, which is guided in the cycle (16) and thereby exposed to a varying pressure, wherein the respective pressure a saturated steam temperature value of the working medium is associated, and

- an expansion device (56) for expanding the working fluid from an elevated pressure (28) to a lower pressure (20), wherein the working medium after expanding to the lower pressure (20) has an evaporation temperature,

characterized in that an adjusting device (104) for setting the Abdampftemperatur to a defined Abdampftemperaturwert (106) above the lower pressure (20) associated Sattdampftemperaturwerts (102) is provided.

2. Apparatus according to claim 1,

characterized in that the defined Abdampftemperaturwert (106) between 2 K and 12 K, preferably between 4 K and 8 K and particularly preferably between 5 K and 6 K above the lower pressure (20) associated Sattdampftemperaturwerts (102).

3. Apparatus according to claim 1 or 2,

characterized in that by means of the adjusting device (104), a temperature of the working medium is to be increased such that the Abdampftemperatur the defined Abdampftemperaturwert (106) above the lower pressure (20) associated Sattdampftemperaturwerts (102).

4. Apparatus according to claim 3,

characterized in that the temperature of the working medium within the expansion device (56) is to be increased by means of the adjusting device (104).

5. Device according to one of claims 1 to 4,

characterized in that the adjusting means (104) comprises a steam supply (108) for supplying steam to the working medium, the steam being in particular superheated steam.

6. Apparatus according to claim 5,

characterized in that the steam is a vapor of the working medium.

7. Device according to one of claims 1 to 6,

characterized in that by means of the adjusting device (104) an opposing pressure on the working medium is to be generated such that the Abdampftemperatur the defined Abdampftemperaturwert (106) above the lower pressure (20) associated Sattdampftemperaturwerts (102).

8. Apparatus according to claim 7,

characterized in that the adjusting means (104) for generating the

Counterpressure on the working fluid comprises a blocking element (156), which is designed in particular with a valve (154) for selectively opening and closing a line leading to the working medium (60).

9. Device according to one of claims 1 to 8,

characterized in that the working medium is guided in a circulation direction (24) and in the circulation direction (24) after the expansion device (56) a condensation device (62) for condensing the expanded working medium is provided, wherein the adjusting device (104) a temperature measuring element ( 1 14, 1 16) for measuring a temperature of the working medium in the circulation direction (24) after expanding and before condensing and / or a Pressure measuring arm (1 18) for measuring the pressure of the working medium in the circulation direction (24) after expanding and before condensing.

10. A method (12) for converting thermal energy from a heat source (14, 17) into mechanical energy by means of a thermodynamic cycle (16) with a working medium, which is guided in the cyclic process (16) and thereby exposed to a varying pressure wherein the respective pressure is associated with a saturated steam temperature value of the working medium,

and a step (96) of expanding the working fluid from an elevated pressure (28) to a lower pressure (20), the working fluid having an evaporation temperature after expanding to the lower pressure (20),

characterized in that the evaporation temperature is set to a defined exhaust temperature value (106) above the saturated steam temperature value (102) associated with the lower pressure (20).