EP3420288A1 - Improved heat pump and process of heat pumping - Google Patents
Improved heat pump and process of heat pumpingInfo
- Publication number
- EP3420288A1 EP3420288A1 EP17716061.1A EP17716061A EP3420288A1 EP 3420288 A1 EP3420288 A1 EP 3420288A1 EP 17716061 A EP17716061 A EP 17716061A EP 3420288 A1 EP3420288 A1 EP 3420288A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- stream
- heat
- refrigerant
- absorber
- evaporator
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000000034 method Methods 0.000 title claims description 36
- 230000008569 process Effects 0.000 title claims description 34
- 238000005086 pumping Methods 0.000 title claims description 16
- 239000006096 absorbing agent Substances 0.000 claims abstract description 105
- 239000007788 liquid Substances 0.000 claims abstract description 98
- 239000003507 refrigerant Substances 0.000 claims abstract description 98
- 239000002904 solvent Substances 0.000 claims abstract description 31
- 230000005540 biological transmission Effects 0.000 claims abstract description 14
- 238000004891 communication Methods 0.000 claims abstract description 13
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical group N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 52
- 229910001868 water Inorganic materials 0.000 claims description 32
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 26
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical group O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 16
- 229910021529 ammonia Inorganic materials 0.000 claims description 14
- 238000001704 evaporation Methods 0.000 claims description 12
- 239000001569 carbon dioxide Substances 0.000 claims description 8
- 239000002253 acid Substances 0.000 claims description 5
- 230000005587 bubbling Effects 0.000 claims description 4
- 239000000314 lubricant Substances 0.000 claims description 4
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 2
- -1 ammonium ions Chemical class 0.000 claims 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical compound OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 claims 1
- 239000011541 reaction mixture Substances 0.000 claims 1
- 238000004064 recycling Methods 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 abstract description 23
- 238000009833 condensation Methods 0.000 abstract description 7
- 230000005494 condensation Effects 0.000 abstract description 7
- 238000012546 transfer Methods 0.000 description 31
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- 238000010521 absorption reaction Methods 0.000 description 17
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 12
- 230000009286 beneficial effect Effects 0.000 description 11
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 9
- 239000004202 carbamide Substances 0.000 description 9
- 239000012071 phase Substances 0.000 description 8
- 230000008020 evaporation Effects 0.000 description 6
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- 238000002156 mixing Methods 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 5
- 239000012530 fluid Substances 0.000 description 5
- 238000012856 packing Methods 0.000 description 5
- KXDHJXZQYSOELW-UHFFFAOYSA-M Carbamate Chemical compound NC([O-])=O KXDHJXZQYSOELW-UHFFFAOYSA-M 0.000 description 4
- 230000006835 compression Effects 0.000 description 4
- 238000007906 compression Methods 0.000 description 4
- 238000004090 dissolution Methods 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 239000007791 liquid phase Substances 0.000 description 4
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 4
- 239000002918 waste heat Substances 0.000 description 4
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 235000011114 ammonium hydroxide Nutrition 0.000 description 3
- 238000009835 boiling Methods 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000013461 design Methods 0.000 description 3
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- 230000002441 reversible effect Effects 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 239000000498 cooling water Substances 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- NNPPMTNAJDCUHE-UHFFFAOYSA-N isobutane Chemical compound CC(C)C NNPPMTNAJDCUHE-UHFFFAOYSA-N 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
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- 241000183024 Populus tremula Species 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 238000004378 air conditioning Methods 0.000 description 1
- 239000001273 butane Substances 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-N carbonic acid Chemical compound OC(O)=O BVKZGUZCCUSVTD-UHFFFAOYSA-N 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000003889 chemical engineering Methods 0.000 description 1
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- 230000001419 dependent effect Effects 0.000 description 1
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- 230000002349 favourable effect Effects 0.000 description 1
- 239000001282 iso-butane Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000010687 lubricating oil Substances 0.000 description 1
- 238000005461 lubrication Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 230000009972 noncorrosive effect Effects 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
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- 229920000151 polyglycol Polymers 0.000 description 1
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- 239000012808 vapor phase Substances 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B25/00—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00
- F25B25/02—Compression-sorption machines, plants, or systems
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/04—Arrangement or mounting of control or safety devices for sorption type machines, plants or systems
- F25B49/043—Operating continuously
Definitions
- the invention relates to a heat pump comprising a closed circuit configured for flow of a solvent and a refrigerant, which closed circuit comprises an evaporator and an absorber, which are mutually interconnected with a first line configured for the transport of vapour from the evaporator to the absorber, and second line configured for the transport of an enriched liquid from the absorber, wherein said evaporator is typically in heat communication with an input stream for transmission of heat into the evaporator and wherein said enriched liquid being brought in heat communication with a output stream for transmission of heat thereto, particularly at high pressure.
- the invention also relates to the use of said heat pump for pumping of heat from an input flow at a first temperature to an output flow at a second temperature.
- the invention further relates to a process of heat pumping comprising the steps of
- Heat pumps are means for upgrading a first heat flow, typically a low temperature waste heat flow, to useful high temperature heat.
- the operating principle of a heat pump is based on the physical property that the boiling point of a fluid increases with pressure. By lowering the pressure, a medium can be evaporated at low temperatures, while an increase of pressure will lead to a high boiling point. At high pressure, the vapour is condensed, which results in a useful source of energy.
- Different types of heat pumps exist, known in the art as the mechanical heat pump, the absorption heat pump and also a hybrid type of heat pump.
- the mechanical heat pump is the most widely used. Its operating principle is based on compression and expansion of a refrigerant.
- a mechanical heat pump thereto is provided with a compressor and an expansion device that are arranged upstream and downstream of a condenser.
- an absorption heat pump the refrigerant is first evaporated, and then brought into contact with an absorption medium or solvent. The absorption process releases useful heat.
- the enriched liquid stream is then compressed and further heated in a generator. This results in evaporation of the refrigerant, which is subsequently condensed and expanded to bring it back in a liquid form ready for another cycle of evaporation.
- a heat pump is for instance disclosed in GB2169069 A.
- the input stream is first heat exchanged and warmed up, so as to extract waste heat.
- the mixture of refrigerant and solvent is then separated, to form a vapour stream primarily or substantially comprising refrigerant and a liquid stream primarily comprising solvent.
- the vapour stream and the liquid stream are compressed and pumped to higher pressure respectively, after which both are combined and useful heat is released. Finally, the resulting stream is expanded and the input stream is again obtained.
- refrigerants are known. All refrigerants are known with an R number.
- Well-known refrigerants include R134a, an organofluor compound, R600 and R600a, being butane and isobutane, R717 or ammonia, R744 or carbon dioxide. The latter is particularly used for low temperature freezer applications, and in applications wherein a potential user allows for heating at non-constant temperatures, as condensation above the transcritical temperature of 31°C occurs over a temperature range.
- a well-known solvent is water.
- ammonia is the most common refrigerant.
- Heat pumps are normally reviewed on the basis of their efficiency, which is expressed as the coefficient of performance (COP). It is determined by the rate of the energy usage (particularly for compressor and/or pump) and the amount of useful heat or cooling released from the condenser or absorber.
- the COP depends on several factors. Especially the temperature difference between waste heat source and potential user is an important factor: the smaller the temperature difference between condensation and evaporation temperature, the higher the efficiency. It is observed that these condensation and evaporation temperatures can often not be chosen freely, but depends on the process of use.
- a most interesting application for a heat pump is the heat pumping from for instance an input temperature in the range of 50-90°C to an output temperature in the range of 100-150°C, preferably at least 110°C.
- the temperature of 100-150°C is often needed as process water.
- These processes generally produce vapors which have to be condensed destroying partly the valued heat into lower grade heat.
- Typical processes are distillation, refining stripping of C02 and the like.
- the net consumption of heat in the 100-150 °C range is a large part of the costs of these industrial processes.
- this heat is produced from high valued primary energy sources like e.g. natural gas employing not to its full potential the exergy to make also electricity.
- vapour from the turbine is led directly into the absorber, that is integrated with either an evaporator into an absorber-evaporator unit or with a "austreiber".
- the absorbed vapour is, as in an absorption heat pump, brought to higher pressure, and then the sent to a condenser, and is thereafter returned to a heating vessel of the power generator turbine.
- Another part is used via further circuits to win back part of the energy of the waste; depending on the input temperature, a high output temperature may be achieved.
- a system is intended as part and improved of a power generator, rather than as a separate heat pump. Moreover, the system does not appear very simple.
- the invention provides a process of pumping heat from an input stream to an output stream, comprising the steps of: (1) heat exchanging the input stream with a circulating stream comprising a refrigerant; (2) evaporating at least part of the circulating stream to obtain a vapour stream and an - at least primarily - liquid stream; (3) compressing the vapour stream; (4) adding the compressed vapour stream and the liquid stream to an absorber; (5) operating the absorber to generate an enriched liquid stream; (6) transmitting heat from the absorber to the output stream, and (7) transporting the enriched liquid stream for reuse as circulating stream.
- the circulating stream comprises a first and a second refrigerant, and wherein the first and the second refrigerant in the vapour stream are dissolved in the absorber into the solvent and react with each other to generate a pair of a positively and negatively charged ions.
- a heat pump comprising a closed circuit configured for flow of a solvent and a refrigerant, which closed circuit comprises an evaporator and an absorber, which are mutually interconnected with a first line configured for the transport of vapour from the evaporator to the absorber, a second line configured for the transport of a primarily liquid stream from the evaporator to the absorber, and a third line configured for transport of an enriched liquid from the absorber towards the evaporator, wherein said evaporator is typically in heat communication with an input stream for transmission of heat into the evaporator and wherein said enriched liquid being brought in heat communication with a output stream for transmission of heat thereto, particularly at high pressure, wherein a compressor is arranged in the first line and an expansion device is arranged in the third line.
- a first refrigerant inlet and a second refrigerant inlet are present and are configured for supply of a first and a second refrigerant.
- heat is generated by the heat of absorption followed by the heat of reaction released at high pressure while the reverse reaction and subsequently desorption occurs at low pressure.
- the reactive medium can be composed of 2 or more components of which at least 2 react together reversibly releasing the heat of reaction.
- the reaction should be exothermic as not to counteract the temperature increase due to compression.
- the first refrigerant is a source of acid and the second refrigerant is a source of base.
- a combination is a good choice of a reversible reaction, wherein the difference in pressure contributes to shift the equilibrium.
- An example of such a system is a mixture of water, ammonia and C02. Ammonia and C02 react together to form the carbamate ion in water. Next to the heat of absorption of NH3 and C02 in water this reaction releases on average 75 kJ/mole of carbamate formed. This heat of reaction would be absent when C02 is absent in the mixture and in that case the system is reduced to an absorption heat pump.
- the working liquid may contain 30-65 wt% of NH3, 30-65 wt H20 and 5-40 wt .
- the here proposed heat pump will use the thermal energy inside these 60-100°C waste streams to be upgraded to the range of 100-150 °C for reuse in the processes lowering significantly the total heat demand.
- the heat pump works at high Coefficient of Performance (COP) with typical COP from 2-4, which is higher than known heat pumps for pumping heat to temperatures above 100°C. An improvement of 10-30% is deemed feasible without too many further optimizations.
- COP Coefficient of Performance
- Unique of this heat pump is its environmentally friendly working fluid of H20, C02 and NH3. The typical reactions involved in this system allow highly efficient pumping of heat in small equipment.
- the invention provides a heat pump comprising a closed circuit configured for flow of a solvent and a refrigerant, which closed circuit comprises an evaporator and an absorber, which are mutually interconnected with a first line configured for the transport of vapour from the evaporator to the absorber, a second line configured for the transport of a primarily liquid stream from the evaporator to the absorber, and a third line configured for transport of an enriched liquid from the absorber towards the evaporator, wherein said evaporator is typically in heat communication with an input stream for transmission of heat into the evaporator and wherein said enriched liquid being brought in heat communication with a output stream for transmission of heat thereto, particularly at high pressure, wherein a compressor is arranged in the first line and an expansion device is arranged in the third line.
- the absorber is configured to have a first outlet to the third line and a second outlet to a fourth line, said outlet and said fourth line being configured for vapour transport back to the evaporator.
- the absorber and the evaporator each having a first inlet for a predominantly liquid stream and with a second inlet for the vapour stream, are configured such for at least partially countercurrent flow of vapour and liquid.
- the invention provides use of the heat pump of the invention for pumping of heat from an input flow at a first temperature to an output flow at a second
- a second temperature in the range of 100-150°C, such as 120-130°C.
- the invention provides a process of pumping heat from an input stream to an output stream, comprising the steps of: (1) heat exchanging the input stream with a circulating stream comprising a refrigerant; (2) feeding a diluted vapour stream to the circulating stream; (3) evaporating at least part of the circulating stream to obtain a vapour stream and an - at least primarily - liquid stream; (4) compressing the vapour stream; (5) adding the compressed vapour stream and the liquid stream to an absorber; (6) operating the absorber such as to create countercurrent flow of liquid and vapour, resulting in an enriched liquid stream for use as the circulating stream and the diluted vapour stream; (6) transmitting heat from the absorber to the output stream, and (7) transporting the circulating stream and the diluted vapour stream for reuse.
- the one or more refrigerants in vapour form are absorbed in the solvent. Because of countercurrent vapour and liquid, a large contact area is obtained resulting in an effective dissolution process, with the concomitant release of heat. Due to the dissolution and condensation of the vapour stream the stream leaving the absorber in vapour form is diluted in refrigerant, i.e. it is a diluted vapour stream, which thus contains comparatively high amounts of solvent, typically water. By combining this diluted vapour stream into the evaporator, evaporation is herewith further stimulated. Reasons for this stimulation may be due to better mixing, facilitating nucleation of vapour bubbles and/or adding of energy.
- the absorber is configured, for instance by means of its inlets and outlets that, under stationary operation, an upper side of the absorber has a lower content of the first and/or second refrigerant than a lower side thereof.
- the evaporator is configured such that, in use under stationary operation, an upper side of the evaporator has a higher content of the first and/or the second refrigerant than a lower side thereof. This is deemed beneficial to create countercurrent flows in the evaporator and the absorber, but it further is deemed beneficial for the setting of the partial pressures in the vapour stream and diluted vapour stream that leave the evaporator and the absorber respectively.
- the size of the absorber and the evaporator vessels are designed in dependence of the mass flow rates of the entering and leaving streams, and in order to achieve a residence time that is sufficient for the desired mass transfer between vapour and liquid and any concomitant reactions.
- a bubbling reactor is a preferred implementation, so as to create a large vapour-liquid interface and to reduce a thickness of a boundary layer between the concentrations of refrigerants in vapour and liquid.
- the term ' diluted vapour stream' refers to a vapour stream wherein the effective mass transfer of the first and/or the second refrigerants is lower than in the vapour stream.
- the lowered mass transfer may result therein that the mass flow rate of the diluted vapour stream is smaller than that of the vapour stream.
- the concentration of refrigerants, particularly refrigerant ions or reaction products in the circulating stream from absorber to evaporator is higher than that in the liquid stream from the evaporator to the absorber.
- this heat is transmitted to an output stream by means of a heat exchanger that is integrated into the absorber.
- the absorber and suitably also the evaporator are embodied as a column into which a heat exchanger is integrated.
- a heat exchanger is integrated.
- the absorber and/or evaporator contains a plurality of stages, each with a mass transfer section and a heat exchanger section.
- heat exchanger tubes that are distributed within the absorber and/or the evaporator.
- the tubes are in use filled with a heat exchanging liquid, more particularly the output stream.
- the tubes may be arranged in any suitable orientation, thus horizontal, vertical and/or under a suitable angle upwards or downwards.
- An orientation that is substantially horizontal is deemed particularly beneficial.
- substantially horizontal orientation is understood to be an arrangement with an angle between -30 and +30 degrees, suitably with an angle between -15 and +15 degrees or even between -5 and +5 degrees. It is understood by the inventors, that such heat exchanger tubes result in an increase of mass transfer, such the liquid may flow on the tube surface, enlarging the interface between gas and liquid.
- such tubes that are arranged substantially horizontal do not need to be provided with a packing. If the orientation is different than substantially horizontal, such a packing, either random or structured, is suitably applied.
- Particularly suitable is the use of the heat pump in combination with a first and a second refrigerant.
- the first refrigerant is a source of acid
- the second refrigerant is a source of base.
- the use of carbon dioxide as the first refrigerant and ammonia as the second refrigerant is preferred, as both refrigerants are commonly available, and carbon dioxide is not or not substantially corrosive.
- both refrigerants are sufficiently volatile. It is to be understood that the refrigerants as mentioned here are in the form as they are present in the vapour phase.
- the refrigerants are also supplied into the system in pure form and/or as diluted with water, either in vapour phase or in liquid phase.
- Ammonia may be supplied as a vapour or as a liquid.
- first and a second refrigerant that are capable of reacting with each other in a reversible manner, particularly with water, is advantageous, as the heat capacity will therewith further increase; not merely the heat of absorption is released, but also heat of reaction.
- the heat pump has been found to work at high Coefficient of Performance (COP) with typical COP from 2- 4.
- COP Coefficient of Performance
- the friendly working fluid of H20, C02 and NH3 is environmentally friendly, and the typical reactions involved in this system allow highly efficient pumping of heat in small equipment.
- Ammonia and C02 react together to form the carbamate ion in water. Formation of bicarbonate and/or carbonate ions is not excluded, particularly not as a side product.
- the working liquid may contain 30-65 wt% of NH3, 30-65 wt% H20 and 5-40 wt%.
- the stream in the fourth line is a diluted vapour stream, implying that it contains relatively more water than the circulating stream.
- the diluted stream thus contains a lower concentration than the circulating stream, which is the enriched liquid stream.
- the addition thereof, as a vapour form to the circulating stream thus generates the interaction between two phases with a different composition. As a consequence, it may stimulate diffusion between the two phases, and therewith acceleration of refrigerant molecules.
- the compressor is provided with an inlet for a lubricant, said lubricant being supplied via a further line, and wherein said further line is divided from either the second line or the third line. Most preferably, the further line is divided from the third line.
- the conditions in the compressor may be controlled, and particularly the temperature be limited, so as to prevent the formation of urea and/or other side products.
- the formation of urea, that typically occurs at 140°C and higher is better prevented, as urea cannot be decomposed easily and therefore does not contribute to the heat pumping function.
- urea may contaminate the compressor, and even may precipitate, which hampers long term operation.
- Figure 1 shows schematically a first embodiment of a reactive heat pump according to the invention
- Figure 2 shows schematically a second embodiment of a reactive heat pump, wherein the absorber and the evaporator are emboded as two-stage countercurrent contactors with intermediate heat exchange;
- Figure 3 shows schematically a third embodiment of a reactive heat pump, wherein the absorber and the evaporator are embodied as countercurrent (packed) columns with heat exchange means installed inside the columns;
- Figure 4 shows schematically a fourth embodiment, which constitutes a further improvement of the third embodiment.
- FIG. 1 shows the reactive heat pump system of the invention according to a first embodiment.
- the heat pump comprises an evaporator 1 and an absorber 2.
- the evaporator 1 and the absorber 2 are herein embodied as columns suitable for bubbling, for instance as flash vessels known per se.
- a first line 101 configured for transport of a vapour stream leaves the evaporator 1 at its first outlet
- the first line 101 enters the absorber 2 via its first inlet 211.
- a compressor 3 is arranged in the first line 101.
- a second line 102 configured for liquid transport leaves the evaporator 1 at its second outlet
- the second line 102 enters the absorber at its second inlet 212.
- a pump 4 is arranged in the second line 102.
- the second inlet 212 is arranged higher than the first inlet 211 so as to stimulate countercurrent flow of liquid and vapour in the absorber 2.
- the exact location of the first inlet 211 and the second inlet 212 is open for further design and optimization, as can be accomplished by a skilled person. It is observed for clarity, that the second line 102 is configured for an at least primarily liquid stream. In other words, it is not excluded that this stream also contains vapour bubbles. It is further observed that the term 'vapour' as used in the context of the invention does not exclude that the vapour is physically a gas being present above its critical temperature
- Figure 1 further shows a first heat exchanger 7 that is arranged within the evaporator 1 and a second heat exchanger 8 that is arranged within the absorber 2.
- the heat exchangers 7, 8 are physically integrated into the evaporator 1 and the absorber 2, it is feasible that the heat exchangers 7, 8 or at least one thereof is coupled in series with the evaporator 1 and the absorber 2 respectively. Rather than a single heat exchanger 7, 8 they may be arranged in series.
- the first heat exchanger 7 enables heat communication of the input stream with the circulating stream of refrigerant and solvent.
- the second heat exchanger is configured for heat exchange between the circulating stream in the absorber 2 and the output stream.
- Figure 1 also shows a third line 103 and a fourth line 104 that are configured for leading respectively a enriched liquid stream and a diluted vapour stream from the absorber 2 to the evaporator 1. More specifically, the diluted vapour stream leaves the absorber via its first outlet 221, and enters the evaporator at the first inlet 111. The enriched liquid stream leaves the absorber via the second outlet 222 and enters the evaporator 1 at the second inlet 112. An expansion device 5, as known per se, is present in the third line 103. A pressure reducing valve 6 is arranged in the fourth line 104 In operation, a vapour stream from the evaporator vessel 1 is compressed and sent to absorber vessel 2 over the first line 101.
- a liquid stream is pumped from the evaporator vessel 1 to the absorber vessel 2 over the second line 102. Since the pressure in the absorber vessel 2 is higher than in the evaporator vessel 1 , refrigerants in the vapour stream are absorbed in the absorber 2 into the lean liquid stream running downwards. Heat is being generated by the heat of absorption (due to condensation and/or dissolution of refrigerant into the solvent) and reaction. The reaction occurs between the first and second refrigerants.
- the streams in absorber vessel 2 are cooled by heat exchanger 8. The temperature in the absorber vessel 2 is therein maintained between 100 and 150°C, preferably between 110 and 140°C.
- both the first and the second refrigerant more specifically carbon dioxide and ammonia
- both the first and the second refrigerant are present in the vapour stream and then selectively absorbed in the liquid in the absorber
- Still a reaction may occur, if the other reactant remains in the liquid and is transported between evaporator and absorber via the liquid streams.
- This may be implemented in accordance with the requirements on output temperature (i.e. to be supplied via the heat exchanger coupled to the absorber), input temperature (to be obtained via the heat exchanger coupled to the evaporator), the flow rates of fluids (for instance process water) to be heat exchanged with the absorber and evaporator, investments into the apparatus, type of refrigerants etc.
- Said ratio of refrigerant mass flow rates between vapour stream and diluted vapour stream could be as low as 1.3.
- the ratio of refrigerant mass flow rates is at least 2.
- the enriched liquid that is generated in the absorber vessel 2 is transported back to the evaporator vessel 1 via the third line 103.
- the liquid level in the absorber vessel 2 is controlled by the valve 5.
- the pressure in the absorber vessel 2 is controlled by a reducing valve 6 which is arranged within the fourth line 104 and allows the diluted vapour stream to move to the evaporator vessel 1.
- the enriched liquid stream - also referred to as circulating stream - running through the third line 103 will flash in the evaporator vessel 1 due to the lower pressure present in this vessel 1. This flashing causes the temperature of the enriched liquid to decrease.
- the stream in the evaporator vessel 1 has to be heated using the first heat exchanger 7 to maintain constant temperature between 70 and 100°C.
- the vapour streams and the liquid streams are transmitted separately from each other. This is deemed beneficial to maintain differences in composition. Moreover, it allows to inject vapour stream and liquid stream at different locations within the evaporator and absorber (vessels). It is believed that the system of the invention may be considered to work such that any water vapour in the vapour stream and the diluted vapour stream is a carrier gas, with in the case of C02, NH3 and water also having some catalytic properties at least. Furthermore, effects of flow behavior are believed to help in setting up a system beneficial for working as a heat pump.
- the diluted vapour stream may contribute to transmission of heat and bubbling so as to increase the evaporation rate of the refrigerants.
- the entering of the vapour stream into the absorber may contribute to distribution of the refrigerants. It is believed that both due to an increase of the vaporization in the evaporator and a better and quicker absorption of the vapour stream in the absorber, the effective heat transfer from the input stream to the output stream can be increased further.
- the two vessels 1, 2 are constructed as bubble columns where the vapour streams enter at the bottom of the vessels.
- the vapour streams move virtually in plug flow from the bottom to the top within the evaporator 1 and the absorber 2.
- the vessels 1,2 are preferably designed so as to have sufficient residence time and interfacial area between liquid and vapour for the heat and mass exchange. This is beneficial to increasing the COP (coefficient of performance) of the heat pump.
- Fig. 2 shows a process diagram of a second embodiment of the heat pump according to the invention, which is configured so as to get, as much as possible and preferably substantially, outgoing vapour streams in thermodynamic equilibrium with ingoing liquid streams. This distinguishes operation in according with the second embodiment from that of the first embodiment, in which the outgoing vapour streams are more in thermodynamic equilibrium with the outgoing liquid streams.
- the evaporator 1 and the absorber 2 are not implemented as simple flash vessels, but as two stage contactor columns.
- Each stage contains a mass transfer section and a heat exchanger 7 A, 7B; 8 A, 8B.
- the mass transfer sections may be equipped with structured or random packing.
- a recycle circuit is added per stage. In other words, liquid coming from a single mass transfer section is collected in a collector and pumped through a heat exchanger by pumps 11 A, 1 IB, 12A and 12B and recycled to the top of the mass transfer section of the same stage. Fresh liquid is continuously added to the top of the columns (i.e. absorber or evaporator).
- an overflow mechanism is applied for the transfer from the first stage to the second stage. Liquid from the collector of a first stage starts to overflow to the next stage and subsequently to the sump when the hold-up of the collectors have reached their maximum.
- an alternative transfer mechanism from the first to the second stage is not excluded.
- Fig. 3 shows a process diagram of a third embodiment of the heat pump of the invention, wherein the absorber and the evaporator are embodied as a column with a single mass transfer section with heat transfer means that are distributed inside the column.
- the heat transfer means are preferably embodied as heat exchanger tubes 7C, 8C, through which a heat exchanging medium flows.
- the heat exchanging medium is suitably the output stream, however, an intermediate cycle with a heat exchanging medium with a high heat capacity and/or non-corrosive and predefined composition may be used alternatively.
- the heat exchanging medium could be an oil. In the latter case, the output stream is again heat exchanged with the intermediate cycle.
- the mass transfer section is in this embodiment, as in any other embodiment suitably provided with mass transfer promoting internals.
- These internals could be structured or random packing. However, the internals may even be omitted when the heat transfer means have sufficient mass transfer promoting capabilities of their own.
- the heat transfer means When embodying the heat transfer means as heat exchanger tubers that are substantially horizontally arranged, the internals could be omitted. Liquid from the top trickles down across the heat exchanger tubes while the vapour flow up in the column.
- the heat exchanger tubes promote the mass transfer between the liquid and the gas and the heat of absorption and reaction is transferred by the heat exchanger tubes. As a consequence, the column is effectively subdivided by the heat exchanger tubes in a plurality of mass transfer stages.
- the heat exchanger tubes are not foreseen to have any positive effect on mass transfer, and are then not feasible to replace random or structured packing or any other mass transfer promoting internals.
- Fig. 4 shows a process diagram of a fourth, preferred embodiment of the heat pump of the invention, wherein the compressor is lubricated by the process mixture.
- C02 and NH3 can react together at high temperature and pressure to form Urea and water.
- Urea is a solid and therefore highly undesirable as it may damage the compressor.
- the formation of Urea needs to be avoided, even small amounts.
- the reaction of ammonia and C02 to form Urea is an equilibrium reaction.
- the presence of water (vapor) will prevent the formation of Urea.
- the compressor is preferably lubricated by the process mixture.
- the enriched liquid running through the third line 103 is used.
- a branch towards the compressor is split off and provided with a valve for determining the flow rate towards the compressor.
- Fig. 4 is identical to the third embodiment shown in Fig. 3. It is to be understood that the lubrication of the compressor by means of the process mixture can alternatively be implemented in the first and the second embodiments shown in Fig. 1 or 2 or in any further embodiment, not shown herein.
- the heat pump suitably comprises one or more inlets for the refrigerants and the solvent.
- the inlets and the outlet can further be used for start up and/or interruption. It is deemed preferable that separate inlets are present for the different refrigerants, which can be connected to supplies thereto, that are well known in the art. Nonetheless, it is not excluded that a pre-mixing chamber is provided, in combination with one or more inlets. Such pre-mixing chamber avoids generation of variations in composition that, like waves, are damped out merely slowly.
- a pre-mixing chamber is in one embodiment arranged within the closed circuit, for instance upstream of the evaporator, more particularly in the low temperature domain.
- the heat pump of the invention is further provided with one or more sensors and a controller.
- the controller is configured for control of the operation of the heat pump, such as the liquid level in the absorber, the temperature in the absorber, as arranged by the flow rate of heat exchanging medium etc.
- the controller may be arranged to control inflow of fresh refrigerant and/or fresh solvent.
- Typical sensors that are envisaged are pressure sensors, temperature sensors, flow sensors and/or pH sensors.
- thermodynamic properties of the mixture are calculated with the extended UNIQUAC activity coefficient method for the liquid phase and the Soave-Redlich-Kwong equation of state for the vapor phase.
- the code for this method was developed as an extension to Aspen Plus.
- the COP of the cycle increases when sufficient amounts of ammonia are present so that the C02 can fully react with the ammonia and water in the liquid phase. Then the cycle does not only benefits from the heat of absorption as in the case with an ammonia water mixture but additionally the heat of reactions.
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Abstract
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NL2016303A NL2016303B1 (en) | 2016-02-23 | 2016-02-23 | Improved heat pump and process of heat pumping. |
PCT/NL2017/050106 WO2017146570A1 (en) | 2016-02-23 | 2017-02-22 | Improved heat pump and process of heat pumping |
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EP3420288B1 EP3420288B1 (en) | 2024-03-27 |
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CN109631415A (en) * | 2018-12-27 | 2019-04-16 | 同济大学 | A kind of steam compressed and chemisorption autocascade cycle system |
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US4016657A (en) * | 1971-07-14 | 1977-04-12 | Passey Now By Change Of Name C | Heat pump freeze drying system |
CA1012454A (en) * | 1971-07-14 | 1977-06-21 | Chand A. Passey | Vacuum and freeze-drying method and apparatus |
DE3140013C2 (en) | 1981-10-08 | 1986-06-19 | Fried. Krupp Gmbh, 4300 Essen | Method and device for utilizing exhaust steam |
GB2169069B (en) | 1984-11-02 | 1989-04-26 | Ic Gas Int Ltd | Improvements in and relating to absorbers for heat pump systems |
US5582020A (en) * | 1994-11-23 | 1996-12-10 | Mainstream Engineering Corporation | Chemical/mechanical system and method using two-phase/two-component compression heat pump |
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