Heat pump device for generating steam and heat

Abstract

The invention relates to a heat pump device that makes it possible to utilize waste heat from technical processes or from the environment to simultaneously generate useful steam (12) and useful heat. The heat pump device comprises a heat pump module (1), a low-pressure steam generator (2) for generating low-pressure steam (11), a steam jet compressor (3) for generating useful steam (12) from high-pressure steam (10) and the low-pressure steam (11), and a first heat exchanger (4) for providing the useful heat. The heat pump device is suitable for applications where there is a simultaneous demand for both steam and heat.

Description

[0001] The invention relates to a heat pump device according to the preamble of claim 1 for the combined generation and provision of useful steam and useful heat using waste heat from technical processes or waste heat from the environment.

[0002] According to their conventional design, heat pumps consist of a compressor, a condenser, an expansion valve, and an evaporator, all connected in a refrigerant circuit. The refrigerant flows in this circuit from the compressor through the condenser, the expansion valve, and finally the evaporator back to the compressor. At the evaporator, heat from a heat source, such as waste heat from industrial processes or ambient heat, is fed into the refrigerant circuit. At the condenser, the heat of condensation is released as usable heat, with the heat release at the condenser occurring at a higher temperature than the heat absorption at the evaporator. This principle and the design of heat pumps are well-known.

[0003] It is also known, for example from DE 10 2011 108 260 A1 or DE 10 2015 117 492 A1, to use the condensation heat of heat pumps for steam generation. In this process, feedwater is heated and evaporated by means of the heat pump's condenser, whereby usable steam at a pressure level suitable for technical applications is generated directly through evaporation.

[0004] Also known are steam jet generators, also called steam compressors or steam jet compressors, which make it possible to raise the pressure level of low-pressure steam to a higher pressure for its technical use. The steam jet generator operates on the principle of a jet pump, whereby a jet of high-pressure steam is supplied to the generator as the motive medium, which draws in the low-pressure steam acting as the suction medium. High-pressure and low-pressure steam mix in the steam jet generator, producing technically usable medium-pressure steam.

[0005] The object of the invention is to provide a heat pump device that makes it possible to efficiently utilize waste heat from technical processes or from the environment for the simultaneous generation of useful heat and useful steam, wherein the useful steam should have a pressure in the range of 3 bar to 11 bar preferred for further technical use.

[0006] This problem is solved by a heat pump device with the features according to claim 1. Advantageous further developments of the invention are listed in claims 2 to 10.

[0007] According to the invention, the heat pump device comprises a heat pump module, a low-pressure steam generator for generating low-pressure steam from feedwater, a steam jet compressor for generating usable steam, and a first heat exchanger for generating usable heat in the form of heated water. To provide the usable heat, the heat pump device has a heating circuit connection that is connected to the first heat exchanger. The heating circuit connection forms the part of a heating circuit belonging to the heat pump device, in which the heating water circulates.

[0008] The heat pump module contains the conventional components of a heat pump, namely at least one compressor, one condenser, one expansion valve, and one evaporator. These are connected by a refrigerant circuit in which a refrigerant circulates. The refrigerant is routed from the compressor through the condenser, the expansion valve, and finally the evaporator back to the compressor. The heat pump module can have one or more compressors in parallel.

[0009] The evaporator of the heat pump module is connected to a waste heat source for the indirect transfer of heat from the waste heat provided by the heat source to the refrigerant. The heat source can be either an external component not belonging to the heat pump device or an integral part of the heat pump device.

[0010] The low-pressure steam generator has a connection for supplying feedwater and a connection for discharging the low-pressure steam generated from the feedwater by evaporation. The thermal energy for evaporating the feedwater is supplied from the refrigerant circuit of the heat pump module. For this purpose, the low-pressure steam generator acts as the condenser of the heat pump module; that is, the low-pressure steam generator is designed such that the heat released during the condensation of the refrigerant, i.e., the heat of condensation, is transferred from the refrigerant to the feedwater via indirect heat transfer within the low-pressure steam generator, which functions as the condenser. The heat of condensation of the refrigerant circulating in the refrigerant circuit of the heat pump module is released in the low-pressure steam generator to directly generate the low-pressure steam.

[0011] For indirect heat transfer, the low-pressure steam generator (which acts as the condenser of the heat pump module), the first heat exchanger, and the evaporator of the heat pump module are each designed as heat exchangers that achieve heat transfer through fluidic separation of the fluids acting as heat transfer media. These heat exchangers are referred to here as mass flow-separated heat exchangers.

[0012] The steam jet compressor has a motive medium inlet for supplying high-pressure steam in the form of a jet of high-pressure steam as the motive medium, a suction medium inlet for supplying low-pressure steam as the suction medium, and an outlet for discharging the useful steam generated in the steam jet compressor from the high-pressure and low-pressure steam in the form of medium-pressure steam.

[0013] Within the scope of this disclosure, low-pressure steam is understood to mean steam with an absolute pressure in the range of approximately 1 bar to 5 bar, medium-pressure steam is understood to mean steam with an absolute pressure in the range of approximately 3 bar to 11 bar, and high-pressure steam is understood to mean steam with an absolute pressure of at least 20 bar.

[0014] The high-pressure steam introduced as a jet at the propellant inlet preferably has an absolute pressure of at least 60 bar.

[0015] The heat pump system utilizes existing waste heat potential to simultaneously generate usable steam at an absolute pressure of up to 11 bar and heating water at a temperature of up to 95 °C. This makes the heat pump system suitable for applications with a simultaneous demand for steam and heat, particularly those requiring significantly more usable steam than could be generated solely from the waste heat of the heat source. By combining the heat pump module with the low-pressure steam generator and the steam jet compressor, which has no moving parts, it becomes possible to efficiently generate usable steam from waste heat or renewable heat sources with significantly better performance figures than would be possible with heat pumps that use the heat of condensation for direct usable steam generation.To generate low-pressure steam, it is sufficient to operate the heat pump module with a maximum condensation temperature of 145 °C. This allows the heat pump module to achieve significantly better performance figures than heat pumps that directly generate usable steam using a steam generator at condensation temperatures greater than or equal to the saturated steam temperature. Steam generation within the heat pump module occurs at a considerably lower temperature compared to a heat pump that generates usable steam directly. This enables performance figures (COP) of greater than 3.0 for the heat pump module.

[0016] The steam jet compressor, driven by a jet of high-pressure steam, also called the motive jet, generates the usable steam from the energy-efficiently produced low-pressure steam by mixing it with the high-pressure steam. The usable steam exiting the steam jet compressor as medium-pressure steam thus possesses the pressure level required for common technical applications.

[0017] To generate high-pressure steam, the heat pump device can include a high-pressure steam generator. This is preferably a conventional steam generator, which is, for example, electrically heated or gas-fired. The high-pressure steam generator is preferably designed to generate high-pressure steam at an absolute pressure of at least 60 bar. The additional energy required to generate the high-pressure steam at 60 bar is negligible in the overall energy balance for generating the same quantity of usable steam at medium-pressure steam level.

[0018] In addition to its high efficiency, the heat pump unit is characterized by its small installation space requirements and low operating costs compared to heat pumps designed for 100% steam demand coverage. One reason for this is that the compressor of the heat pump module requires a smaller displacement volume than a compressor in a heat pump that directly generates usable steam.

[0019] Any natural or synthetic refrigerant is suitable as a refrigerant, provided that its critical temperature exceeds at least the low-pressure vapor temperature – preferably a temperature of 120 °C.

[0020] According to one embodiment of the invention, the heat pump module further comprises a second heat exchanger arranged as an aftercooler in the refrigerant circuit between the condenser and the first heat exchanger for preheating the feedwater by indirect heat transfer of residual heat from the refrigerant to the feedwater. For indirect heat transfer, the second heat exchanger is again designed as a fluid-flow-separated heat exchanger, which achieves heat transfer through fluidic separation of the respective heat transfer fluids. The second heat exchanger is connected to the low-pressure steam generator to supply it with the preheated feedwater. By using the first and second heat exchangers as aftercoolers in the refrigerant circuit, the residual heat of the refrigerant present after its condensation in the low-pressure steam generator can be utilized particularly efficiently.Preheating the feedwater also increases the efficiency of low-pressure steam generation.

[0021] Furthermore, the heat pump device may be designed to include at least one preheating stage or at least one preheating unit for preheating the waste heat provided by the heat source. The respective preheating stage or preheating unit can be, for example, a heat pump or another type of heating element.

[0022] In particular, the heat pump device can include one or more preheating stages designed as heat pumps, which are connected to the refrigerant circuit of the heat pump module in a cascade configuration. The cascade comprises the refrigerant circuit of the heat pump module and the preheating stages in series. The refrigerant circuit of the heat pump module forms the final stage of the cascade; the preheating stages are the preceding stages. The cascade gradually raises the temperature level of the waste heat transferred from the heat source to the evaporator of the heat pump module.

[0023] The heat pump device with preheating stages or units is particularly suitable for use with low-temperature heat sources. The version without preheating stages or units, also known as a single-stage version, should ideally be operated with a heat source temperature of at least 60 °C. In the case of a heat pump device without preheating stages or units, the heat pump device can include the heat source, which is designed to provide waste heat at a heat source temperature of at least 60 °C.

[0024] Furthermore, the heat pump module may be provided with a third, internal heat exchanger, through which additional heat is extracted from the refrigerant after the first heat exchanger, acting as an aftercooler in the refrigerant circuit. This extracted heat is then used to preheat the refrigerant immediately before it enters the compressor of the heat pump module. For this purpose, the third, internal heat exchanger is designed to divert a portion of the residual heat from the refrigerant circuit after the first heat exchanger via indirect heat transfer and feed it into the refrigerant circuit immediately before the compressor, also via indirect heat transfer.

[0025] The invention is explained in more detail below with reference to an exemplary embodiment and the drawing; for this purpose, the Fig. 1the schematic fluidic circuit diagram of a single-stage design of the heat pump device, i.e., a design of the heat pump device without preheating stages or units and without an internal heat exchanger.

[0026] The design of the heat pump device according to Fig. 1 The heat pump module 1 has a refrigerant circuit represented by a dotted line. The direction of circulation of the refrigerant 1.7 in the refrigerant circuit is indicated by the arrows.

[0027] The heat transfer of the waste heat provided by heat source 8 into the refrigerant circuit of the heat pump module 1 takes place via the evaporator 1.4 of the heat pump module 1, which is designed as a mass flow-separated heat exchanger. The heat source 8, which in the single-stage version of the heat pump device according to Fig. 1The component of the heat pump device should be designed so that the heat source temperature is at least 60 °C.

[0028] The evaporated refrigerant 1.7 travels in the refrigerant circuit from the evaporator 1.4 to the compressor 1.1. In the compressor, the refrigerant 1.7 is compressed, which also heats it up. The compressed, gaseous refrigerant 1.7 then flows in the refrigerant circuit to the condenser 1.2, where it condenses and releases heat of condensation.

[0029] According to the invention, the low-pressure steam generator 2 forms the condenser 1.2 of the heat pump module 1 or operates as such, wherein the condensation heat released during the condensation of the refrigerant 1.7 in the condenser 1.2 is transferred by means of indirect heat transfer to the feedwater 7 supplied to the low-pressure steam generator 2 for its evaporation. For indirect heat transfer, the condenser 1.2 is designed as a mass flow-separated heat exchanger. For the implementation of the heat pump device according to Fig. 1 The operating temperature of the condenser 1.2, and consequently that of the low-pressure steam generator 2, lies in the range of 100 °C to 145 °C. The low-pressure steam 11 generated in the low-pressure steam generator, according to the exemplary embodiment shown, has a temperature of 100 °C to 145 °C. Fig. 1 an absolute pressure in the range of 1 bar to 4.5 bar.

[0030] The refrigerant 1.7, liquefied in condenser 1.2, flows in the refrigerant circuit from condenser 1.2 to the second heat exchanger 5, which acts as an aftercooler 1.6 in the refrigerant circuit. In the second heat exchanger 5, the residual heat present in the refrigerant 1.7 is transferred to the feedwater 7 to preheat it. The preheated feedwater 7, 7.1, is then directed from the second heat exchanger 5 to the low-pressure steam generator 2. For indirect heat transfer, the second heat exchanger 5 is designed as a fluid-flow-separated heat exchanger.

[0031] The refrigerant 1.7, which still contains residual heat after leaving the second heat exchanger 5, flows in the refrigerant circuit from the second heat exchanger 5 to the first heat exchanger 4. This first heat exchanger is also designed as a fluid-flow-separated heat exchanger for indirect heat transfer and acts as an aftercooler 1.5 in the refrigerant circuit. In the first heat exchanger 4, the residual heat of the refrigerant 1.7 is transferred to the heating water 6 circulating in the heating circuit. The heated heating water 6 is discharged from the first heat exchanger 4 via the heating circuit connection (not shown or labeled) and thus the usable heat is supplied to the consumer, for example, a heating system. The heating water 6 can be heated to temperatures of up to 95 °C by means of the first heat exchanger 4.

[0032] To complete the cycle process in the heat pump module 1, the refrigerant 1.7 is routed in the refrigerant circuit from the first heat exchanger 4 via the expansion valve 1.3 back to the evaporator 1.4.

[0033] The design of the heat pump device according to Fig. 1The system further comprises the steam jet compressor 3 and the high-pressure steam generator 9. In the high-pressure steam generator 9, high-pressure steam 10 is generated at a pressure of at least 60 bar, which is supplied to the steam jet compressor 3 via its motive fluid inlet in the form of a jet. This jet of high-pressure steam 10, acting as the motive fluid in the steam jet compressor 3, is also referred to as the motive jet. The low-pressure steam 11 generated in the low-pressure steam generator 2 is drawn into the steam jet compressor 3 via the suction fluid inlet of the steam jet compressor 3, which is connected to the low-pressure steam generator 2, by the suction effect emanating from the motive jet. Here, it mixes with the high-pressure steam 10 to form the useful steam 12. The useful steam 12 is medium-pressure steam, which in the exemplary embodiment according to Fig. 1It has a pressure in the range of 6 bar to 10 bar and a temperature in the range of 160 °C to 185 °C. The useful steam 12 is a mixture of the high-pressure steam 10 and the low-pressure steam 11, wherein the proportion of the high-pressure steam 10 in this mixture forming the useful steam 12 is a maximum of 75% by mass and the proportion of the low-pressure steam 11 is at least 25% by mass. Reference symbol list

[0034] 1 Heat pump module 1.1 Compressor 1.2 Condenser 1.3 Expansion valve 1.4 Evaporator 1.5 Aftercooler 1.6 Aftercooler 1.7 Refrigerant 2 Low-pressure steam generator 3 Steam jet steam compressor 4 First heat exchanger 5 Second heat exchanger 6 Heating water 7 Feed water 7.1 Preheated feed water 8 Heat source 9 High-pressure steam generator 10 High-pressure steam 11 Low-pressure steam 12 Useful steam

Claims

1. Heat pump device with a heating circuit connection (6) carrying heating water for the provision of useful heat and with a heat pump module (1) which has one or more parallel compressors (1.1), a condenser (1.2), an expansion valve (1.3) and an evaporator (1.4), which are connected to each other in a refrigerant circuit of the heat pump module (1) which carries a refrigerant (1.7) from the compressor (1.1) via the condenser (1.2), the expansion valve (1.3) and finally the evaporator (1.4) back to the compressor (1.1), wherein the evaporator (1.4) of the heat pump module (1) is connected to a heat source (8) for the indirect heat transfer of waste heat provided by means of the heat source (8) to the refrigerant (1.7), characterized by the fact thatThe heat pump device further comprises: - a low-pressure steam generator (2) forming the condenser (1.2) of the heat pump module (1) for generating low-pressure steam (11) with an absolute pressure in the range of 1 bar to 5 bar by evaporating feedwater (7) supplied to the low-pressure steam generator (2) by means of indirect heat transfer of the heat released during condensation of the refrigerant (1.7) from the refrigerant (1.7) to the feedwater (7) within the condenser (1.2) the low-pressure steam generator (2) forming the heat pump module (1), and - a steam jet compressor (3) for generating useful steam (12) with an absolute pressure in the range of 3 bar to 11 bar from a jet of high-pressure steam (10) as motive medium and the low-pressure steam (11) generated in the low-pressure steam generator (2) as suction medium, wherein the high-pressure steam (10) has an absolute pressure of at least 20 bar, and wherein the steam jet compressor (3) has a motive medium inlet for supplying the high-pressure steam (10), a suction medium inlet for supplying the low-pressure steam (11) and an outlet for discharging the useful steam (12) generated in the steam jet compressor (3), wherein the heat pump module (1) further comprises an aftercooler (1.5) in the refrigerant circuit between the condenser (1.2) and the expansion valve (1.3) arranged first heat exchanger (4) connected to the heating circuit connection for heating the heating water (6) by indirect heat transfer from residual heat of the refrigerant (1.7) to the heating water (6).

2. Heat pump device according to claim 1, characterized by the fact that The heat pump module (1) further comprises a second heat exchanger (5) arranged as an aftercooler (1.6) in the refrigerant circuit between the condenser (1.2) and the first heat exchanger (4) for preheating the feedwater (7) by indirect heat transfer from residual heat of the refrigerant (1.7) to the feedwater (7), wherein the second heat exchanger (5) is connected to the low-pressure steam generator (2) for supplying the preheated feedwater (7, 7.1) to the low-pressure steam generator (2).

3. Heat pump device according to claim 1 or 2, characterized by the fact thatthe heat pump device shall have at least one preheating stage or at least one preheating unit for preheating the waste heat provided by the heat source (8) before the heat transfer of the waste heat to the refrigerant circuit.

4. Heat pump device according to claim 3, characterized by the fact that the heat pump device comprises one or more preheating stages designed as heat pumps, which are connected in a cascade to the refrigerant circuit of the heat pump module (1).

5. Heat pump device according to claim 3, characterized by the fact that the heat pump device comprises one or more preheating units, wherein the respective preheating unit is a heat pump or other heating energy generator.

6. Heat pump device according to claim 1 or 2, characterized by the fact that the heat pump device comprises the heat source (8), wherein the heat source (8) is configured to provide waste heat at a heat source temperature of at least 60 °C.

7. Heat pump device according to one of claims 1 to 6, characterized by the fact that the low-pressure steam generator (2) is designed to generate the low-pressure steam (11) at an absolute pressure in the range of 1 bar to 5 bar.

8. Heat pump device according to one of claims 1 to 7, characterized by the fact that The heat pump device comprises a high-pressure steam generator (9) for generating the jet of high-pressure steam (10).

9. Heat pump device according to claim 8, characterized by the fact that the high-pressure steam generator (9) is designed to generate the high-pressure steam (10) at a pressure of at least 60 bar.

10. Heat pump device according to one of claims 1 to 9, characterized by the fact thatthe heat pump module (1) has a third, internal heat exchanger for preheating the refrigerant (1.7) before its compression, wherein the third, internal heat exchanger is designed to divert a portion of the condensation heat or residual heat from the refrigerant circuit after the condenser (1.2) by indirect heat transfer and feed it into the refrigerant circuit immediately before the compressor (1.1) by indirect heat transfer.

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