AT510809A1 - DEVICE FOR WASTE USE - Google Patents

Abstract

The invention relates to a device for waste heat recovery based on ORC thermal cycle processes, which are implemented by means of ORC-operated ORC circuits, wherein an ORC circuit at least one working fluid pump, at least one heat exchanger, at least one expansion device for driving a generator and at least one condensation device, at least one first ORC circuit (42) and at least one second ORC circuit (43) each having at least one working fluid pump (32, 32 '), at least one preheating heat exchanger (33, 33'). , at least one evaporative heat exchanger (34, 34 ') are provided, wherein the ORC circuits (42, 43) via at least one common expansion device (36) are coupled together and have a common condensation device (38). The invention further relates to a mixing condenser (18) for use as a condensation device in such a device for waste heat utilization.

Description

PI 1925

Device for waste heat utilization

The invention relates to a device for waste heat recovery based on ORC thermal cycle processes, which are implemented by means of ORC-operated ORC circuits, wherein an ORC circuit at least one working fluid pump, at least one heat exchanger, at least one expansion device for driving a generator and at least one condensation device.

The invention also relates to a mixed condensing apparatus for use as a condensing apparatus in the above-mentioned waste heat recovery apparatus.

As will be explained in more detail below, the mentioned ORC fluid may be a medium of various states of aggregation, for example liquid or gaseous or vaporous.

The use of the waste heat of thermodynamic processes, such as residual or waste heat of industrial plants or the internal combustion engine of a combined heat and power plant (CHP), by waste heat recovery systems using ORC (Organic Rankine Cycle) processes is well known, the ORC process is essentially a process for the operation of expansion devices such as gas or steam turbines with a working fluid other than water vapor, namely organic or synthetic liquids with a low evaporation temperature.

Waste heat refers to heat flows that originate from other process flows. Heat flows are fluids that are either static in containers or dynamically moved by currents. Heat flows have temperatures that are higher than the ambient temperatures. Heat flows are thus fluids in the liquid or gaseous state, which provide heat convective, radiant or conductive.

The use of these heat flows takes place by transferring the heat to other fluids, which are used as working fluid for generating mechanical or (subsequently) electrical energy. Such use in the form of the water-steam cycle is well known.

In the following remarks, the terms low temperature (NT) and high temperature (HT) are used. Low temperature refers to temperatures of 50 ° C to 90 ° C. High temperature refers to temperatures of 135 ° C to 400 ° C and higher. Processes using the abovementioned waste heat recovery systems therefore produce waste heat which is classified as low temperature up to a maximum of 90 ° C and as high temperature at temperatures of 135 ° C to 400 ° C.

The structure and function of the water-steam cycle underlying the ORC process are well known and well known. Therefore, this technology will not be discussed further here. In ORC, no water is used as the working fluid (hereinafter also referred to as ORC fluid), but organic fluids, such as e.g. 1, 1, 3, 3, 3 pentafluoropropane (R245fa), carbon dioxide (CO2, or R744 - in the following text these terms are used synonymously for carbon dioxide), butane (R600) and propane (R290). The ORC fluids carbon dioxide, butane and propane are natural ORC fluids. The fluids R245fa and R227ea (1,1,1,2,3,3,3-heptafluoropropane) are synthetic organic ORC fluids.

Butane has significant disadvantages, as its flammability makes extensive technical measures necessary. Another disadvantage of butane and propane are the low operating temperatures, or the areas of use. For propane, for example, only a low temperature application is possible. Although butane can be used up to temperatures of 145 ° C, but a direct contact with a waste heat carrier is technically difficult to realize, since the flammability represents a significant disadvantage.

Although the synthetic ORC fluid R245fa can be used up to an evaporation temperature of 145 ° C, it is highly toxic and has a very high global warming potential. In addition, higher evaporation temperatures are possible only in the trans-critical range, which is technologically difficult to implement and therefore excretes for use in power generation.

The synthetic ORC fluid R227ea is similar to the behavior and use of propane. Although R227ea is not flammable and flammable, it can only be used in the low-temperature range, just like propane. Furthermore, it is highly toxic and has a high global warming potential.

The ORC fluids Propane and R227ea can therefore only be used in the low-temperature range up to a maximum evaporation temperature of 85 ° C. A combination of low-temperature and high-temperature ORC fluids requires a separate circulation and thus disadvantages in the process control and equipment. The mixture of two such fluids in the expansion device is not possible. -3- PI 1925

On the one hand, there is a lack of ORC fluids in the state of the art that can exploit the full range of theoretically available heat flows while being safe in operation.

On the other hand, the (electrical) efficiencies of known ORC processes are still very poor due to the similarity to the water-steam cycle. There are therefore increasingly attempts to develop devices with which this efficiency can be increased. For example, DE 10 2008 013 545 A1 describes a device for utilizing the waste heat from internal combustion engines by means of an ORC process, the efficiency of which is to be improved with a supplementary lubricant circuit. WO 2010/106089 A2 describes a method for steam generation, for example with an ORC steam generator, which is preceded by a thermal generator to increase the efficiency. DE 199 07 512 A1 describes a device for energy conversion on the basis of thermal ORC cycle processes, wherein the efficiency is to be improved by an at least two-stage cascaded arrangement of ORC cycle processes.

All these solutions have in common that they either require expensive devices or can not increase the efficiency sufficiently. On the problem of suitable ORC fluids is not discussed in the prior art.

It is therefore an object of the invention to provide a device for waste heat utilization, which allows a higher efficiency and is simple in construction.

This object is achieved with an aforementioned device for waste heat recovery (hereinafter: waste heat recovery system) according to the invention that at least a first ORC cycle and at least a second ORC cycle, each with at least one working fluid pump, depending at least one preheating heat exchanger, at least one Evaporating heat exchangers are provided, wherein the ORC circuits are coupled to each other via at least one common expansion device and have a common condensation device.

The invention allows the combination of different ORC cycles of different pressure levels, different mass flows and thus the use of heat potentials with different temperatures and heat flows. The coupling by means of a common expansion device is carried out in such a way that the vaporous ORC fluids from the circuits at a suitable location or at the appropriate time into the expansion device -. be introduced so that an optimal conversion of the energy of the ORC fluids takes place.

In a variant of the invention, at least one superheating heat exchanger and / or at least one separating device are provided in the first ORC cycle and / or in the second ORC cycle between the evaporative heat exchanger and the expansion device. This ensures that only superheated steam and no liquid portions reach the expansion device, which is beneficial because liquid fractions can damage the expansion device (e.g., when using linear piston expanders).

In principle, therefore, the above variant per ORC cycle allows at least one superheating heat exchanger or a separating device, which can also be provided together. Each ORC circuit can be equipped with one or both components independently of the other circuit.

With the provision of a separation device separating vaporous and liquid components, the liquid fractions may be reintroduced into the circuits at a different location, for example, after expansion of the ORC fluid in the expansion device or elsewhere, where the ORC fluid is predominant is liquid.

The ORC circuits can be operated with different heat flows, namely high and low temperature heat flows. In a variant of the invention, the first ORC cycle is operated with a high-temperature heat flow and the second ORC cycle is operated with a low-temperature heat flow. The heat flows define the thermal power which is available in each case and which can be used for power generation by the device according to the invention with coupled ORC circuits. The reference temperature is always the ambient temperature (25 ° C or 298.15 ° K).

Thus, the waste heat recovery system can be depending on the present waste heat situation-in most processes falls heat of different temperatures and with different heat flows; By way of example, the gas engine of a combined heat and power plant can be called a waste heat source - and the efficiency (especially electrical) of such a plant can be increased considerably in comparison to known plants. Furthermore, such a system can be realized structurally very simple.

In a variant of the invention, the preheating heat exchanger, the evaporating heat exchanger, the superheat heat exchanger of the second OR circuit and the Vor¬ αιατζ ··· * ·· ** ·· 1 liyAZ) · «* * · · * * • 4 ι »4 4 1 ·· II · 4 4 ♦ · 5 heat exchangers of the first ORC circuit are operated with a low-temperature heat flow and the evaporative heat exchanger and the overheating heat exchanger of the first ORC circuit are equipped with a high-temperature heat flow operated.

By the solution according to the invention an optimal utilization of different heat potentials can be achieved. Thus, on the one hand, a system-technically optimized solution can be found by means of this combination. The combination of both circuits makes it possible to react to different heat flows and temperature levels with appropriate flexibility and high efficiency.

To increase the efficiency of the device, at least one recuperator heat exchanger for preheating the ORC fluid supplied to the working medium pumps of the first and second ORC circuits is provided between the expansion device and the condensation device. The expanded gaseous ORC fluid present after the expansion device is passed through the recuperator heat exchanger, through which passes the liquid ORC fluid originating from the condensation device, which is supplied again to the ORC circuits. In the Recuperator so the liquid ORC fluid is preheated by the gas or vapor ORC fluid.

The ORC fluid is selected from the group consisting of carbon dioxide (R744), butane (R600) and propane (R290). Of the fluids mentioned, carbon dioxide is often referred to as a universal ORC fluid, since it can be used both in the high-temperature and in the low-temperature range.

Carbon dioxide is particularly useful as an ORC fluid. Its advantages are so far-reaching, since the application is limited neither in the low-temperature range nor in the high-temperature range. Carbon dioxide is practically usable and usable for energy cycles and waste heat recovery applications.

The realizable high pressure range is advantageous because it allows the systems to be kept very small and compact and can be technically easily implemented.

Another big advantage is that R744 is neither toxic nor flammable or flammable and therefore does not present a hazard to the environment if it is released as a result of a technical problem. Furthermore, it only changes from the vapor state to the plasma state at 2500 ° C. Applications of the plasma, however, are not covered by the system according to the invention.

Another major advantage of using R744 is that it does not require any additional heat transfer medium in the form of hot water, hot water or thermal oil. Instead, R744 can be brought into direct contact with a waste heat stream.

In principle, however, both carbon dioxide and butane and propane can be used.

Advantageously, at least one generator connected to the expansion device is provided, which emits the energy from the expansion device. A suitable frequency converter transforms the electrical energy to the required frequency.

In a further variant of the invention, the condensation device is a mixed condensation device comprising at least one ORC fluid storage tank and at least one expansion tank connected to a jet compressor, ORC fluid coming from the direction of the expansion device being supplied to the expansion tank via a supply line is supplied and the jet compressor through-flowing ORC fluid is at least partially supplied to the working fluid pump via a discharge line. Essentially, in such a mixed condensation device, liquid ORC fluid from the storage tank and gaseous ORC fluid coming from the expansion device are fed to the jet compressor, where mixed condensation occurs and consequent condensation of the gaseous ORC fluid. In this case, an external cooling is advantageously arranged in the storage tank. This external cooling can be designed for example as a chiller.

This cooling keeps the liquid ORC fluid at a low temperature. In the mixed condensation so a total cooling is achieved because the cold, liquid ORC fluid absorbs the heat of condensation.

The cold ORC fluid that occurs during this co-condensation can be removed and used for various cooling tasks in the plant (e.g., cooling the bearings of the expansion device).

The object of the invention is further achieved with an initially mentioned mixed condensation device for use in a waste heat recovery system as described above, wherein the mixed condensation device comprises at least one storage tank for liquid media, at least one expansion tank and at least one jet compressor consisting of a suction chamber and a mixing nozzle, wherein the expansion tank has at least one supply line for vaporous media and at least one suction line and the suction line is connected to the suction chamber of the jet compressor and wherein the storage tank is connected to the jet compressor and the expansion tank and liquid media after the jet compressor via at least one discharge line are laxative-bar.

In a variant of the invention, the jet compressor on a diffuser, which is arranged in the flow direction of the media after the mixing nozzle. The diffuser serves to increase the pressure of the resulting from the mixing nozzle liquid ORC fluid.

In a further variant of the invention, at least one bearing line is furthermore provided, via which the outlet of the jet compressor is connected to the storage tank. Thus, the storage tank can be refilled.

In the following the invention will be explained in more detail with reference to a non-limiting embodiment, which is illustrated in the drawing. In this shows schematically:

Fig. 1 shows a waste heat recovery system according to ORC according to the prior art;

2 shows a variant of the waste heat recovery system of FIG. 1 according to the prior art,

Fig. 3 shows a waste heat recovery system according to the invention, and

4 shows a mixed condensation device according to the invention.

In the figures, identical or corresponding areas, components, component groups or method steps are identified by the same reference numerals. The flow directions in lines are marked with arrows.

Fig. 1 shows a waste heat recovery system 1 according to the prior art. Shown is an ORC with the following components: Work fluid pump 2 for compressing the ORC fluid circulating in ORC, preheat heat exchanger 3, evaporative heat exchanger 4, superheat exchanger 5, expansion device 6 with generator 7 and condensation device 8. The expansion device 6 is, for example a gas turbine having a high pressure (HD) stage 61 and a low pressure (ND) stage 62.

The mode of operation of the illustrated ORC is known in principle: the working medium pump 2 compresses the ORC fluid to the vaporization pressure associated with the evaporation temperature to be achieved. After the pump, the ORC fluid is preheated in a preheat heat exchanger 3. Low or high temperature heat flows can be used here. Thereafter, the ORC fluid is passed through an evaporative heat exchanger 4 where it is vaporized. The heat source is the process heat or waste heat from upstream machines such as. Internal combustion engines in combined heat and power plants. To ensure that the liquid ORC fluid is completely vaporized, an overheat heat exchanger 5 is then used.

Instead of an overheating heat exchanger 5, a separating device such as a separating bottle 9 (hereinafter always only the term Abscheidcflasche used - of course, the deposition can also be done by other solutions) can be used (shown in phantom), in front of the expansion device 6 in incomplete evaporation to separate the liquid ORC fluid from the vaporous ORC fluid. The resulting liquid ORC fluid is fed via a flash valve 10 to the liquid ORC fluid before the working fluid pump 2.

Separator bottles 9 are particularly necessary for those ORC fluids whose maximum evaporation temperature is below the critical point temperature. In such cases, it is advisable to replace the overheating heat exchanger 5 by a separating bottle 9 and to feed the saturated steam of the expansion device 6, while the liquid portion of the ORC fluid derived and again the circuit (preferably before the working fluid pump 2) can be supplied. The separation bottle 9 thus separates vaporous from liquid ORC fluid. Their use is therefore particularly necessary if the trans-critical evaporation process in the upstream heat exchangers is not completely completed.

The deposition of the liquid fluid in the separation bottle 9 allows the protection of the expansion device 6 from liquid hammer. Such liquid shocks are undesirable particularly in piston engines, as they affect the expansion process and damage the machine.

After evaporation, the ORC fluid is supplied to the expansion device 6. The expansion device 6 can be bypassed if necessary via a bypass fitting 11 (for example, when the expansion device 6 is not ready, or when starting or stopping the device) and the gaseous ORC fluid is fed directly to the condensation device 8. In the condensation device 8, the ORC fluid releases the heat of condensation to a cooling circuit. The heat of condensation can then be supplied, for example, to a district heating network,

The condensation device 8 comprises a condenser 12, which is connected to its own cooling circuit, consisting of a cooling circuit circulation pump 13 and a return heat exchanger 14, the recooling heat exchanger 14 sucks in ambient air and allows it to flow over the heat exchanger surface.

Alternatively, in the condensation device 8, the condenser 12 can also be replaced directly by the re-cooling heat exchanger 14. The recooling heat exchanger 14 then sucks in the air and the condensation of the ORC fluid takes place in the recooling heat exchanger 14. This variant is shown in Fig. 1 with dash-dotted lines. Capacitor 12 and cooling circulation pump 13 remain recessed in this variant.

The liquefied in the condensation device 8 ORC fluid is in turn supplied to the working fluid pump 2 and again passes through the ORC.

When the expansion device 6 is ready for use, the bypass fitting 11 is closed and a fast closing valve 15 upstream of the expansion device 6 (two valves can also be provided, as shown in the figure). The vaporized ORC fluid is then expanded via the high pressure (HD) stage 61 and low pressure (ND) stage 62 of the expansion device 6, thereby driving a generator 7 coupled directly to the expansion device 6. The electrical power thus obtained is converted by a frequency converter 16 in a known manner to the mains frequency.

FIG. 2 shows a variant of the ORC shown in FIG. 1 in the form of a circulation circuit in which a recuperator heat exchanger 17 is additionally used. The purpose of the recuperator heat exchanger 17 is to transfer the existing heat of the expanded in the expansion device 6, but still vaporous ORC fluid to the compressed with the working fluid pump 2 liquid ORC fluid. Thus, the recuperator heat storage 17 allows the use of the resulting heat after the relaxation process on the Kreislaufscite after compression by the working fluid pump. 2

Such a recuperator heat exchanger 17 is advantageous in order to increase the electrical efficiency of the device. This is especially true when using CO2 as ORC fluid.

After the recuperator heat exchanger 17, the thus heated ORC fluid is fed back to a preheat heat exchanger 3. In general, this preheat heat exchanger 3 is a heat exchanger that uses heat flows with very little exergy. Heat flows of low exergy are available in most waste heat recovery systems in very large quantities to -10- P] 1925

Available. More difficult is the supply of heat flows of high exergy - these are available only in small quantities.

Evaporation 4 and superheat heat exchangers 5 are therefore decoupled from the preheat heat exchanger 3. As in the variant illustrated in FIG. 1, a separating bottle 9 (dashed lines) can also be used here if no superheated heat exchanger 5 is used. The liquid ORC fluid can be relieved again via an expansion valve 10 and fed to the circuit via the recuperator heat exchanger 17, while the vaporous part of the ORC fluid is fed to the expansion device 6 as saturated steam.

After the overheating in the superheating heat exchanger 5 (or after the separating bottle 9), the gaseous ORC fluid can again be passed via a bypass fitting 11 past the expansion device 6 directly to the condensation device 8 or via the quick-closing valve 15 of the HD 61 and LP stage 62 the expansion device 6 are supplied.

The expansion device 6 is again directly coupled to a generator 7 (synchronous or asynchronous) and generates via a frequency converter 16 in a known manner electrical power with appropriate network frequency.

After decompression, the liquefaction takes place in the condensation device 8. This device again consists of a circulating pump 13, a forced-circulation heat exchanger 14 with forced convection and a condenser 12, in which the gaseous expanded ORC fluid is condensed. Air is drawn in and blown over the surface of the recooling heat exchanger 14. Alternatively, as in FIG. 1, instead of the condenser 12, the recooling heat exchanger 14 can also be used directly as a condenser.

However, the circuits according to the prior art illustrated in FIGS. 1 and 2 have considerable disadvantages. The cycle processes are modeled on the properties of water (or the water-steam process) and are unsuitable for other ORC fluids such as CO2 (R744, or carbon dioxide). When using R744 for such circuits, only efficiencies of about 10 percent are achieved electrically.

This is due in particular to the small two-phase region in the state diagram and the low critical temperature of CO2 compared to water. In contrast to water, CO2 is only liquid at room temperature of 25 ° C if it is kept under a pressure of at least 64 bar. At ambient pressure of about 101325 Pa (= 1.01 bar) and -11- an ambient temperature of 25 ° C (= 298.15 ° K), CO2 is vaporous. Furthermore, CO2 differs from water due to the low densities (volumes) at higher pressures and low density changes (volume changes) in expansion processes in the vapor state. However, these properties are particularly important in the expansion device and other components of ORCs such as valves and heat exchangers.

3 shows a waste heat utilization system 31 according to the invention as a combination of two ORC circuits, namely a first circuit, which is guided as a high-temperature circuit (HT-ORC circuit) 42, and a second circuit, which is a low-temperature circuit (NTC). ORC cycle) 43 is guided. This combination makes it possible to use different heat potentials with high flexibility and very high efficiency.

In most waste heat processes different heat potentials occur. The temperatures and the heat flow of a heat potential determine the maximum achievable mass flow of the ORC fluid in the respective circuit. By the temperature of the resulting heat flow, for example, the maximum evaporation temperature of the ORC fluid is set in the HT-ORC cycle.

The two circuits can basically be operated separately or together. In the exemplary embodiment in FIG. 3, the two ORC circuits are coupled to one another via an expansion device 36. The expansion device 36 comprises a high-pressure (HD) stage 361 for the vaporous ORC fluid of the HT-ORC circuit 42 and a low-pressure (ND) stage 362 for the NT-ORC circuit 43. The HT-ORC Circuit 42 is shown in Fig. 3 with dashed lines, while the NT-ORC circuit 43 is shown in dotted lines.

The HT-ORC cycle 42 comprises, in addition to an HT working fluid pump 32, an HT preheating heat exchanger 33, a HT evaporating heat exchanger 34 and an HT superheating heat exchanger 35. The HT working fluid pump 32 brings the ORC fluid to the for HT-ORC cycle needed higher evaporation pressure. Since vaporization pressure and vaporization temperature are thermodynamically coupled in the two-phase region of the ORC fluid, a higher vaporization pressure results in a higher vaporization temperature. This corresponds to the higher temperature level of the supplied high-temperature (HT) heat flow Q-HT.

The NT-ORC circuit 43 includes an NT work fluid pump 32 '(which produces a lower pressure level suitable for the NT-ORC circuit 43, which also reduces the evaporation rate.) 12- ## «··« · * · 94 «« Is lower, an NT preheat heat exchanger 33 ', an NT evaporative heat exchanger 34' and an NT superheat heat exchanger 35 '.

Instead of or in addition to the superheat heat exchangers 35, 35 'can be provided corresponding Abscheideflaschen 39, 39', from which via appropriate expansion fittings 310, 310 ', the liquid remaining ORC fluid can be drained and recycled to the circuit.

Separator bottles 39, 39 'are particularly advantageous during startup and shutdown of the plant and generally in situations where complete evaporation is not achieved in the evaporative heat exchangers 34, 34' and a multiphase mixture is obtained containing liquid and gaseous ORC fluid are.

The saturated steam is brought in the subsequent superheat heat exchanger 35, 35 'to a temperature which is higher than the evaporation temperature of the respective ORC fluid. This design has the advantage to be used even at very high evaporation pressures.

When using a forced circulation evaporator (not shown in the figures), in which the superheat heat exchanger is arranged downstream of the separating bottle, the separating bottle becomes a steam drum, from which the saturated steam is removed and then overheated. The forced circulation evaporator is a drum evaporator in which the liquid preheated ORC fluid is evaporated; The heat is supplied via a tube bundle coil. At the upper end of the drum evaporator then the saturated steam is removed and fed to the superheat heat exchanger. The disadvantage of such a drum evaporator is that the evaporation pressure is limited to lower pressures.

Since low-temperature (NZ) heat flows Q-NT are usually present in larger quantities in applications of the waste heat recovery system according to the invention, this heat flow to the H l preheat heat exchanger 33, the NT preheat heat exchanger 33 ', the NT evaporative heat exchanger 34 'and the NT superheat heat exchanger 35' divided.

Part of the low temperature (NT) heat flow Q-NT is thus used in the HT preheat heat exchanger 33 to preheat the ORC fluid for the HT-ORC cycle 42. This can increase the efficiency of the system. The remainder of the low temperature (NT) heat Q-NT is used for the NT-ORC cycle 43 to vaporize ORC fluid at a lower pressure. -13-

The HT-42 and the NT-ORC circuit 43 can be relaxed using a HT-311 or NT bypass fitting 311 ', with the expansion device 36 being bridged. Thus, an operation of the circuits without expansion device 36 is made possible to pass after the shutdown and before starting the vaporous ORC fluid to the expansion device 36. In this case, heat is essentially released into the environment (for example, to a heating network) only in the condensation device 38 and no electrical energy is generated.

When the expansion device 36 is to be used, the vapor ORC fluid from the HT-ORC circuit 42 enters the HP stage 361 of the expansion device 36 via the HT quick-acting valve 315. The fluid from the NT-ORC circuit 43 enters the LP stage 362 of the expansion device 36 via the NT quick-acting valve 315 '. The HD stage 361 of the expansion device 36 is thus associated with the HT-ORC circuit 42, while the ND stage 362 of the expansion device 36 is associated with the NT-ORC circuit 43.

The expansion device 36 is coupled directly to a generator 37, the resulting electrical power is transformed with the Frequenzumrichtcr 316 to the mains frequency.

The expanded (but still gaseous or vaporous) ORC fluid from HT and NT-ORC cycle 43 is combined after the expansion device and used in a recuperator heat exchanger 317 thermally in such a way that it the circuits after the condensation device 38th newly supplied (liquid) ORC fluid preheats.

This is followed in the condensation device 38 by the condensation of the gaseous ORC fluid by means of classical contact condensation (by means of recooling condenser or heat exchanger 314, see also the explanations regarding FIG. By virtue of the common condensation device 38 for top and NT ORC circuit 43, both circuits therefore expand to a common condenser pressure level which is determined by the condensation device 38 (mixed or contact condensation).

The condensed liquid ORC fluid is then passed over the recuperator heat exchanger 317 and compressed by the HT-32 and NT working fluid pump 32 'and supplied to the respective ORC circuit. -14-

The condensation device 38 is technically feasible, for example, as a combination of electrically operated fans with a heat exchanger. The disadvantage of this is that a large part of the heat of vaporization used in the ORC process must be released as condensation heat to the environment in the context of condensation in order to liquefy the ORC fluid. However, it is possible to use this heat, e.g. by connecting a district heating network. Therefore, this solution of contact condensation in large condensation plants is quite feasible.

The vaporous ORC fluid to be condensed is passed into a condenser 312, which is fed by a separate cooling circuit with a cooling circuit circulation pump 313 and a recooling heat exchanger 314. The refrigeration cycle circulation pump 313 sucks air and allows it to flow across the condenser surface 312, thereby condensing the ORC fluid. The heat of condensation is then released via the recooling heat exchanger 314.

Alternatively, condenser 312 and cooling circulation pump 313 may be omitted and the condensation of the ORC fluid takes place directly in the recooling heat exchanger 314 (this variant is shown in phantom in FIG. 3).

Although the contact condensation can be realized easily, but has only low efficiencies and is highly dependent on the ambient temperature. Therefore, cs may experience variations in power efficiency and efficiency.

The condensation device 38 is surrounded in Fig. 3 by a dotted drawn rectangle. Instead of the device in the rectangle, the method of mixed condensation can also be used. The corresponding mixed condensation device (see FIG. 4 and the associated explanations) then replaces the components arranged in the rectangle. This mixed condensation can be used favorably, especially for smaller ORC capacities and plants.

4 shows the mixed condensation according to the invention, which of course can also be used in ORCs according to the prior art (FIGS. 1 and 2). To explain the function, the use of carbon dioxide as ORC fluid is assumed. In principle, other ORC fluids can also be used with corresponding adaptations.

In the mixed condensation, the ORC fluid to be condensed is mixed with liquid ORC fluid and condensed. The heat of condensation is transferred to the ORC fluid and is thus available to ORC circuits partially or completely for use. P11925 P11925 • * «I • · *» $ Φ ·· • Μ · * · ··

• * * I «·« · · I

«* * · Ι« I • »* 1« «· · · · · · ·« ΜΙ # · «·« -15-

The process utilizes the physical effect of heating the liquid contact fluid. The condensation transfers the heat of condensation to the liquid ORC fluid.

The mixing condenser 18 in Fig. 4 comprises a storage tank 19 in which liquid ORC fluid is stored. Depending on the required temperature an external cooling 20 is provided. Such an external cooling 20 is particularly necessary if the temperature at which the ORC fluid is liquid and which must therefore be present in the storage tank 19 in order to keep the ORC fluid liquid is lower than the prevailing ambient temperature. In such a case, tank and ORC fluid absorb heat from the environment despite isolation and the ORC fluid can evaporate.

When carbon dioxide as ORC fluid, for example, a temperature of 10 ° C is desirable. As external cooling 20, for example, a chiller can be used in accordance with general expertise. The chiller can be cooled in a known manner via the soil or from the groundwater, or with a combination of a cooling and water cycle.

The carbon dioxide is stored at a pressure of about 64 bar. The volume of liquid carbon dioxide is a storage volume and starting point for the implementation of the mixed condensation.

A mixed condenser pump 21 draws in the liquid ORC fluid and compresses it to 70 bar. Via the expansion tank fitting 22, the liquid ORC fluid is expanded or expanded into the expansion tank 23 to a lower pressure. One part of the ORC fluid evaporates, the other part remains liquid and cools by removing the heat of vaporization. The liquid is extracted as much heat as the vaporized portion needed for evaporation {enthalpy of vaporization). In the expansion tank 23, therefore, liquid cold ORC fluid and vaporous ORC fluid collect. The expansion vessel 23 may further be supplied with vaporous ORC fluid after expansion in the expansion device 36 or through the recuperator heat exchanger 317 (see FIG. 3).

In order to prevent an increase in the vapor pressure in the expansion tank 23 vaporous ORC fluid is sucked through a suction line 24 and fed to a jet compressor 25, which acts as a liquid jet pump. The jet compressor 25 comprises a suction chamber 26, a mixing nozzle 27 and a diffuser 29. In addition to the vaporous ORC

Fluid from the expansion tank 23 is supplied to the jet compressor 25 via the jet compressor fitting 28 liquid ORC fluid from the storage tank 19.

By introducing liquid ORC fluid into the jet compressor 25, the vaporous ORC fluid is sucked into the suction chamber 26 (physical effect of the dragging action) and passed further into the mixing nozzle 27. There it comes to a thorough mixing of the liquid and the vaporous ORC fluid and there is a mixed condensation.

So that there is no evaporation of the liquid ORC fluid in the mixing nozzle 27, the circulating mass flow (and in particular the proportion of liquid, cold ORC fluid) is maximally high, so that the temperature reached in the condensate of the mixed condensation is still lower than that to the local pressure in the jet compressor 25 associated steam temperature of the condensate.

The amount of vapor to be condensed and the flow temperature of the liquid ORC fluid in front of the jet compressor 25 determine the circulating liquid fluid flow. In the design, the ratio is preferably 1: 3, ie about 25 percent of the gaseous ORC fluid can be liquefied with liquid ORC fluid (condensed). The circulating mass flow must therefore be about 3 times greater than the accumulating ORC fluid steam mass flow.

Subsequent to the mixing nozzle 27, a diffuser 29 is arranged for compression, which slows down the flow velocity and increases the gas or liquid pressure. In this case, a pressure is reached which is higher than the pressure in the storage tank 19th

The liquefied ORC fluid is partly recycled via a bearing line 30 into the storage tank 19. For this purpose, the pressure achieved by the diffuser 29 must be higher than the pressure in the storage tank 19, so that after overcoming the pressure losses and the geodetic height, the ORC fluid can be brought into the storage tank 19. The rest of the ORC fluid is returned to the ORC (or HT-42 and NT-ORC circuit 43).

The liquid in the expansion tank 23 ORC fluid can be used for cooling purposes, for example, for cooling Gasurbincnlagern, combustion chamber walls and the like. For a cooling pump 40 are shown for compression on storage tank pressure and a cooling heat exchanger 41 for cooling. If no cooling is needed, the supercooled liquid ORC fluid can be brought into the storage tank 19. As a result of this recycling, the cooling of the fluid in the storage tank 19 can be partially or completely saved. The cooling still required is very low and thus contributes to a very high efficiency of the system.

In principle, the waste heat recovery system according to the invention can be operated with various known expansion devices 36, which convert the thermal energy of the ORC circuits into mechanical energy. The person skilled in a number of expansion devices is known, which will therefore not be discussed further.

Depending on the size of the circulating mass flows, various expansion devices may be advantageous. For example, with very small mass flows (less than 2 kg / sec), the use of an axial turbine is not technologically possible; instead, a piston expander can be used. In the expansion devices, the efficiency can be increased by cooling with cold ORC fluid from low process pressures.

The design of the turbine depends on the pressure levels of the individual ORC circuits, which are to be coupled together. In the presence of two different pressure levels (HT-42 and NT-ORC cycle 43), the two ORC circuits are coupled via the low-pressure stage (NT-ORC circuit 43). The condensation pressure for the turbine, derived from both ORC circuits, is the same and determined by the inventive mixed condensation.

The invention thus comprises the combination of ORC circuits 42, 43 of different pressure levels and different mass flows for the utilization of heat potentials with different temperatures and heat flows using adapted expansion devices. In one variant, a suitable mixed condensation with a corresponding mixing condenser is used.

Vienna, the [} & November 2010 • P11925 • * * * • • • • • I I · · · · t -18-

REFERENCE LIST 1.31 From heat utilization system 2 Working medium pump 3 Preheating heat exchanger 4 Evaporating heat exchanger 5 Superheating heat exchanger 6, 36 Expander 7.37 Generator 8, 38 Condenser 9, 39, 39 'Separating bottle 10, 310, 310' Maturation valve 12, 312 Capacitor 13, 313 Cooling circulating pump 14,314 Recooling heat exchanger 15 Quick-action valve 16, 316 Frequency converter 17,317 Recuperator heat exchanger 18 Mixing condensor 19 Storage tank 20 External cooling 21 Mixing condenser pump 22 Expansion vessel fitting 23 Expansion vessel 24 Suction line 25 Jet compressor 26 Suction chamber 27 Mixing nozzle -19- PI 1925 • «· 28 Blast Packing Valve 29 Diffuser 30 Lagcrleitung 32 HT-Working Fluid Pump 32 'NT- Working Pump 33 HT - Preheating -Wär exchanger 33' NT-Preheating-Heat Exchanger 34 HT -V er vaporization heat exchanger 34 ' NT Underground Heat Exchanger 3 5 HT overheating heat exchanger 35 'NT superheating heat exchanger 40 Cooling pump 41 Cooling heat exchanger 61, 361 High pressure (HP) stage 62, 362 Low pressure (LP) stage 311 HT bypass fitting 311' NT / C mixing valve 315 HT High-speed shut-off valve 315 'NT quick-acting valve 42 HT ORC circuit 43 NT ORC circuit 44 Supply line 45 Drain line

Claims (14)

Claims 1. Apparatus for utilizing waste heat on the basis of thermal ORC cycles, which are implemented by means of ORC-operated ORC circuits, wherein an ORC circuit - at least one working fluid pump, - at least one heat exchanger, - at least one expansion device for driving a generator and - at least one condensation device, characterized in that at least one first ORC circuit (42) and at least one second ORC circuit (43), each with at least one working fluid pump (32, 32 '), each at least one preheating heat exchanger (33, 33 ') and in each case at least one evaporating heat exchanger (34, 34') are provided, wherein the ORC circuits (42, 43) via at least one common expansion device (36) are coupled together and have a common condensation device (38). 2. Apparatus according to claim 1, characterized in that in the first ORC circuit (42) and / or in the second ORC circuit (43) between the evaporating heat exchanger (34, 34 ') and expansion device (36) depending at least one superheat heat exchanger (35, 35 ') and / or at least one separating device (39, 39') are provided. 3. A device for waste heat recovery according to claim 1 or 2, characterized in that the ORC circuits (42, 43) with different waste heat streams (Q-HT, Q-NT) are operated. 4. Device for wastewater utilization according to one of claims 1 to 3, characterized in that the first ORC circuit (42) is operated with a high-temperature heat flow (Q-HT) and the second ORC circuit (43) with a low-temperature Heat flow (Q-NT) is operated. 5. Waste heat recovery device according to claim 2, characterized in that the preheating heat exchanger (33), the evaporation heat exchanger (34 '), the superheat heat exchanger (35) of the second OR circuit (43) and the preheating heat exchanger (33) - 21- PI1925 of the first ORC circuit (42) are operated with a low-temperature heat flow (Q-NT) and the evaporation heat exchanger (34) and the superheat heat exchanger (35) of the first ORC circuit (42) having a high temperature Heat flow (Q-HAT) are operated. 6. A device for waste heat recovery according to one of claims 1 to 5, characterized in that between the expansion device (36) and condensation device (38) at least one Recuperator heat exchanger (317) for preheating the working fluid pumps (21, 21 ') of the first (42 ) and second ORC circuit (43) supplied to liquid ORC fluid. 7. A waste heat recovery device according to any one of claims 1 to 6, characterized in that the ORC fluid is selected from the group consisting of carbon dioxide (R744), butane (R600) and propane (R290). 8. A device for waste heat recovery according to one of claims 1 to 7, characterized in that at least one with the expansion device (36) connected generator (37) is provided. 9. Waste heat recovery device according to one of claims 1 to 8, characterized in that the condensation device (38) is a mixed condensation device (18), comprising at least one storage tank (19) for ORC fluid and at least one expansion tank (23 ), which are connected to a jet compressor (25), wherein from the direction of the expansion device (36) coming ORC fluid is supplied to the expansion tank (36) via a feed line (44) and the jet compressor (25) flowing through ORC fluid at least partially Working medium pumps (32, 32 ') via a discharge line (45) is supplied. 10. A device for waste heat recovery according to claim 9, characterized in that in the storage tank (19) an external cooling (20) is arranged. 11. A device for waste heat recovery according to claim 10, characterized in that the external cooling (20) is designed as a chiller. 12. mixed condensing device (18) for use in a device for waste heat recovery according to one of claims 1 to 11, comprising at least one storage tank (19) for liquid media, at least one expansion tank (23) and at least one Strahlv he poet (25). consisting of a suction chamber (26) and a mixing nozzle (27), the expansion tank (23) having at least one feed line (44) for vaporous media and at least one suction line (24) and the suction line with the suction chamber (26) of the jet compressor ( 25) is connected and wherein the storage tank (19) with the jet compressor (25) and the expansion tank (23) is connected and liquid media after the jet compressor (25) via at least one discharge line (45) can be discharged. 13. mixing condenser (18) according to claim 12, characterized in that the jet compressor (25) has a diffuser (29), which is arranged in the flow direction of the media after the mixing nozzle (27). 14. mixing condenser (18) according to claim 12 or 13, characterized in that further comprises at least one bearing line (30) is provided, via which the output of the jet compressor with the storage tank (19) is connected. Vienna, the T \ 0t Nov. MV!