Apparatus and method for utilising waste heat

Abstract

The invention relates to an apparatus for utilising waste heat, comprising: a cooling circuit (1) which is coupled to a thermal store (13); and a steam-generating unit (21), wherein the thermal store (13) contains a liquid storage medium and the cooling circuit (1) is coupled to the thermal store in such a way that heat can be transferred from a coolant flowing through the cooling circuit (1) to the storage medium, and the steam-generating unit (21) comprises an evaporator which is coupled to the thermal store (13) in such a way that a flow of storage medium from the thermal store (13) can be utilised as a heat source for generating steam. The invention also relates to a method for utilising waste heat in such an apparatus.

Description

[0001] 240348W001

[0002] Device and method for utilizing waste heat

[0003] Description

[0004] The invention relates to a device for utilizing waste heat, comprising a cooling circuit for cooling a process and a steam generation device that is operated with a cooling medium flowing in the cooling circuit as a heat source. The invention further relates to a method for utilizing waste heat in such a device.

[0005] Heat recovery can improve process efficiency. However, particularly in discontinuous processes or continuous processes that require frequent interruptions, such as for maintenance, waste heat is currently often released without any added value, typically using river water or air for heat removal. One reason cited for the lack of utilization of waste heat from such processes is the effort required, as it results in a loss of flexibility. This is because processes must be synchronized to directly utilize waste heat from one process in another.

[0006] To bridge interruptions, it is known to use thermal storage. However, integrating thermal storage involves significant equipment complexity and varies considerably depending on the specific application. Another problem with discontinuous processes is the fluctuating temperature and the associated fluctuations in the amount of heat.

[0007] For the utilization of waste heat from discontinuous processes, it is known, for example, from KR-A 1020150032241, to use a heat transfer fluid to cool a reactor and then to heat another heat transfer fluid with this fluid, which is then fed to a flash steam generator for steam production. To ensure a continuous supply of steam in the event of a reactor interruption, a steam storage tank is connected downstream of the flash steam generator. However, the disadvantage of this method is that the steam occupies a large volume, requiring a correspondingly large steam storage tank. Furthermore, the steam storage tank must also be stable under the steam pressure.

[0008] A waste heat recovery system in which hot flue gases are cooled with a refrigerant and the heat absorbed by the refrigerant is subsequently used to generate electrical energy is known from US Patent 2010 / 0319348. To enable continuous electrical energy generation even during intermittent combustion, two heat storage units with different temperature levels are used.

[0009] A method for generating electrical energy that utilizes two thermal storage units is also known from US patent 2023 / 0287808. Here, a molten salt is used as a heat transfer medium, whereby the molten salt releases heat from the hot thermal storage unit to generate steam, which is then used to generate electrical energy. After heat transfer to a cold thermal storage unit, the process is called 240348W001.

[0010] 2

[0011] The molten salt from the cold heat storage unit is heated and transferred back into the hot heat storage unit.

[0012] The object of the present invention was to provide a device and a method for utilizing waste heat that can also be used at fluctuating temperatures and in discontinuously operated processes.

[0013] The problem is solved by a device for utilizing waste heat comprising a cooling circuit coupled to a heat storage unit and a steam generation device, wherein the heat storage unit contains a liquid storage medium and the cooling circuit is coupled to the heat storage unit in such a way that heat can be transferred from a cooling medium flowing through the cooling circuit to the storage medium, and the steam generation device comprises an evaporator coupled to the heat storage unit in such a way that a storage medium flow from the heat storage unit can be used as a heat source for steam generation.

[0014] The method for utilizing waste heat implemented in the device includes:

[0015] (a) Cooling of a process, wherein the cooling medium absorbs heat from the process;

[0016] (b) Transfer of heat to the storage medium when the cooling medium has a temperature above a minimum storage temperature and no heat transfer to the storage medium when the cooling medium has a temperature below the current minimum storage temperature;

[0017] (c) Extraction of part of the storage medium from the heat storage unit and use of part of the cooling medium as a heat source for steam generation in the steam generation unit.

[0018] The device according to the invention makes it possible to utilize even discontinuously generated heat, for example from batch processes, for continuous steam generation. Furthermore, heat can be stored until the temperature in the entire heat storage system is so high that no more heat can be absorbed by the storage medium. This also means that when the temperature in the heat storage system is close to the minimum storage temperature, more waste heat can be absorbed at a lower temperature level, thus allowing the heat storage system to be recharged more quickly. Additionally, heat can be absorbed until the maximum storage temperature is reached when temperature peaks occur in the process, thereby heating the cooling medium to its maximum temperature through process cooling.By separating the cooling circuit in which the coolant flows, the storage circuit in which the storage medium is guided, and the separate circuit for steam generation, the device, unlike known devices, also allows for useful heat storage when the temperature of the process, 240348W001.

[0019] 3. The waste heat stored in the system fluctuates. Due to the separate circuits for the cooling medium, the storage medium, and steam generation, it is still possible to use different media. Because of the different requirements for the cooling medium, the storage medium, and the medium to be evaporated, it is particularly advantageous to use different media as the cooling medium, the storage medium, and the medium to be evaporated, respectively.

[0020] A further advantage of the device and method according to the invention is that, by separating the cooling medium, storage medium, and steam generation, specific media can be used for each task. Thus, regardless of the cooling medium used, it is possible, for example, to use a medium with a low vapor pressure at the temperatures in the heat storage unit as the storage medium. Cross-contamination of the steam generated in the steam generation unit by leaks in the heat-dissipating process and in the heat storage unit can also be prevented. Furthermore, a medium with high heat capacity can be used in the heat storage unit to reduce hold-up, or a refrigerant that does not solidify at low ambient temperatures can be used in the cooling circuit, thus ensuring continuous operation.

[0021] The thermal storage system can be a stratified storage system; the storage medium within the thermal storage system can have a continuous temperature profile, or the storage medium within the thermal storage system can be mixed, so that the temperature of the storage medium within the thermal storage system is essentially constant. "Essentially constant" in this context means that there can be deviations from the average temperature of the storage medium, particularly at an inlet point of the storage medium into the thermal storage system, and further deviations can occur, for example, at the walls of the thermal storage system, such as through heat loss to the environment.

[0022] If the thermal storage system is a stratified storage system or if the storage medium within the thermal storage system has a continuous temperature profile, it is preferred to include a heat exchanger that is integrated into the cooling circuit and through which heat is transferred from the cooling medium to the storage medium. For heat transfer, both the cooling medium and the storage medium flow through the heat exchanger, and the heat is transferred indirectly from the cooling medium to the storage medium. The heat exchanger can be located inside or outside the thermal storage system, with an external arrangement being preferred. Any heat exchanger known to those skilled in the art for indirect heat transfer is suitable, for example, a shell-and-tube heat exchanger, a plate heat exchanger, or a spiral heat exchanger. A plate heat exchanger is preferred.

[0023] To maintain the continuous temperature profile or temperature layers in the stratified storage system, it is preferred if the storage medium, after absorbing heat from the cooling medium, is introduced into the heat storage system at a position where storage medium with a similar temperature is located and storage medium is available for absorbing heat from 240348W001

[0024] 4. The cooling medium is extracted at a point where the storage medium has a minimum temperature. Furthermore, it is preferred if the storage medium used as a heat source for steam generation is extracted at the point where the storage medium has the maximum temperature and, after releasing heat for steam generation, is fed back in at the point where the storage medium has a similar temperature. It is further preferred if the supply and extraction of the storage medium are carried out in such a way that the storage medium in the heat storage unit is mixed as little as possible due to the supply and extraction of storage medium.Since the density of the storage medium generally decreases with increasing temperature, it is preferred that the supply of the storage medium after heat absorption from the cooling medium occurs at a point of similar temperature, and the withdrawal of the storage medium for steam generation occurs at the top of the heat storage unit, and that the withdrawal of the storage medium for heat absorption from the cooling medium and the supply of the storage medium after heat release for steam generation occur at the bottom of the heat storage unit. "Top of the heat storage unit" refers to the upper third of the heat storage unit, preferably the upper quarter, and particularly the upper tenth. "Bottom of the heat storage unit" refers accordingly to the lower third of the heat storage unit, preferably the lower quarter, and particularly the lower tenth, wherein, in particular, the withdrawal point for the storage medium taken from the cooling medium for heat absorption is located at the bottom of the heat storage unit.“Similar temperature” means that the difference in temperature between two media is less than 20 K, preferably less than 10 K and in particular less than 3 K.

[0025] Provided that the storage medium in the thermal storage unit maintains a substantially constant temperature, for example, when the storage medium is mixed within the thermal storage unit, the supply and withdrawal of the storage medium for use in steam generation and for heat absorption in the heat exchanger can occur at any point within the thermal storage unit. Furthermore, it is preferred that the supply and withdrawal of the storage medium also results in the mixing of the storage medium within the thermal storage unit.

[0026] Particularly when the storage medium in the thermal storage unit maintains a substantially constant temperature, in addition to using a heat exchanger, it is possible, for example, to provide a double jacket or a coiled pipe through which the cooling medium flows and transfers heat to the storage medium in the thermal storage unit. However, the use of a heat exchanger is preferred.

[0027] Within the scope of the present invention, the "minimum storage temperature" is understood to be the minimum temperature at which the storage medium in the heat storage unit exhibits heat. The "maximum storage temperature" is the temperature at which the storage medium can no longer absorb heat from the cooling medium.

[0028] To efficiently store heat in the thermal storage unit, it is preferable if the storage medium does not evaporate due to heat absorption from the cooling medium. For this purpose, the 240348W001 is used.

[0029] 5

[0030] The pressure of the storage medium is selected such that it lies above the boiling point at maximum storage temperature, that is, above the temperature to which the storage medium can be heated by absorbing heat from the cooling medium. Furthermore, the heat storage system is operated at a pressure at which no storage medium evaporates. For this reason, it is particularly preferred if the heat absorption from the cooling medium, the heat release for steam generation, and the heat storage are carried out at a substantially constant pressure. "Substantially constant pressure" here means that pressure changes may occur, for example, through the use of pumps or due to flow-related pressure losses, but apart from pumps for transporting the fluid flows, no compression or expansion devices are used.

[0031] To prevent the storage medium from boiling in the thermal storage unit and to minimize its evaporation, the maximum storage temperature is below the boiling point of the storage medium at the given pressure in the thermal storage unit. Preferably, the maximum storage temperature is at least 20 K below the boiling point, more preferably 10 to 15 K below the boiling point, and particularly 5 to 8 K below the boiling point of the storage medium at the given pressure in the thermal storage unit.

[0032] Any heat transfer medium known to those skilled in the art is suitable as a storage medium, provided it preferably remains liquid and does not evaporate up to the maximum storage temperature. Depending on the maximum storage temperature, the storage medium can be, for example, a heat transfer oil, water, a molten salt, a mixture of one or more glycols and water, an aqueous salt solution, or paraffin. Preferably, the storage medium is selected from heat transfer oils, water, or aqueous mixtures of glycols and water, and aqueous salt solutions, and in particular, from heat transfer oils, water, and mixtures of glycols and water.

[0033] To remove heat from a process, it is common practice to either cool the device in which the process is carried out or, alternatively, to cool the material streams drawn from the device. Processes whose waste heat can be utilized with the inventive method and device include, for example, a chemical reaction, cooling of a material stream, or cooling of an apparatus.

[0034] Devices in which the process is carried out can be, for example, columns, vessels, or pipelines equipped with a double jacket or surface-mounted coils through which a cooling medium flows. Alternatively, especially in the case of columns or vessels, cooling coils can be provided internally through which the cooling medium flows. Any process that generates heat can be carried out in the apparatus. Common processes include, for example, chemical reactions, absorption processes, adsorption processes, crystallization, dissolution of solids in liquids, or condensation. 240348W001

[0035] 6

[0036] In addition to the aforementioned devices, tube bundle systems, for example, can also be used. In these systems, one medium flows through the pipes and another medium flows around them. In this case, heat is transferred via the walls of the individual tubes in the tube bundle system, whereby it is possible for the warmer medium to flow around the tubes, or for the colder medium to flow around them. A chemical reaction, for example, can also be carried out in a tube bundle system.

[0037] When waste heat is transferred to the cooling medium by cooling a fluid stream, heat exchangers are typically used. Common heat exchangers include shell and tube heat exchangers, plate heat exchangers, block heat exchangers, and spiral heat exchangers.

[0038] Furthermore, waste heat from industrial plants or engines can also be used. In this case, the cooling medium is used to cool the industrial plant or the engine, with the cooling medium absorbing the heat.

[0039] Preferably, the waste heat absorbed by the cooling medium originates from a chemical process, particularly a chemical reaction, for example, an exothermic chemical reaction carried out in a batch process. Reactions in which the device and the process can be used include, for example, polymerizations, neutralizations, or oxidations.

[0040] The cooling medium used to cool the process can be any suitable cooling medium known to a person skilled in the art. Suitable cooling media include, for example, water or mixtures of water and an alcohol or salt. Suitable alcohols, which can be used in mixtures with water or in pure form, include, for example, glycols such as ethylene glycol or propylene glycol. Suitable salts, which can be added to water, include, for example, sodium chloride or carbonate salts. Other suitable cooling media include, for example, heat transfer oils, liquid salts, or sodium.

[0041] To prevent heat loss from the thermal storage system when the cooling medium's temperature falls below the minimum storage temperature after heat absorption, heat is only transferred from at least a portion of the cooling medium to the storage medium if its temperature is above the minimum storage temperature. Once the cooling medium's temperature after heat absorption from the process reaches or falls below the minimum storage temperature, no further heat is transferred from the cooling medium to the storage medium.

[0042] Whether only part of the cooling medium or the entire cooling medium transfers heat to the storage medium depends in particular on the minimum storage temperature and the temperature at which the cooling medium is supplied to the process. 240348W001

[0043] 7

[0044] If the temperature of the cooling medium after absorbing heat from the process and the temperature of the cooling medium supplied to the process for cooling are both above the minimum storage temperature, it is advantageous to separate the cooling medium into a first and a second part after heat absorption from the process. The first part of the cooling medium transfers heat to the storage medium, while the second part does not. After the heat transfer to the storage medium, the first and second parts of the cooling medium are mixed again. By mixing the first part of the cooling medium, which transferred heat to the storage medium, with the second part, which did not transfer heat to the storage medium, it is possible to adjust the temperature of the cooling medium to the temperature at which it is to be supplied to the process for cooling.For this purpose, the hot cooling medium flow extracted from the process is divided into the first and second parts in such a way that the desired mixing temperature is achieved.

[0045] If the temperature of the cooling medium after absorbing heat from the process is above the minimum storage temperature, and the temperature of the cooling medium supplied to the process for cooling is below the minimum storage temperature, it is preferred that all of the cooling medium transfers heat to the storage medium and that at least a portion of the cooling medium is cooled in a cooler after transferring heat to the storage medium. Since the temperature of the cooling medium after transferring heat to the storage medium remains above the temperature at which it is supplied to the process for cooling, it is necessary to cool the cooling medium further after transferring heat to the storage medium. Therefore, at least a portion of the cooling medium is first cooled in the cooler after transferring heat to the storage medium before being supplied to the process again for cooling.Whether all of the cooling medium, or only a portion of it, is fed to the cooler after transferring heat to the storage medium depends, for example, on the temperature of the cooling medium after transferring heat to the storage medium. The smaller the difference between the temperature of the cooling medium after transferring heat to the storage medium and the temperature at which the cooling medium is fed into the cooling process, the less heat the cooling medium needs to transfer to maintain the desired temperature.Depending on the amount of heat that needs to be dissipated by the cooling medium and the temperature and mass flow rate of the stream used for cooling, the mass flow rate of the portion of the cooling medium supplied to the cooler is selected in order to obtain the desired temperature after cooling and remixing of the portion of the cooling medium supplied to the cooler with the portion that was not separately cooled, at which the cooling medium is supplied to the process for cooling.

[0046] Since the temperature of the cooling medium supplied to the process is always below the temperature of the cooling medium removed from the process after cooling, no heat is transferred from the cooling medium to the storage medium when the temperature is 240348W001

[0047] 8. The temperature of the cooling medium after heat absorption from the process is below the minimum storage temperature. This prevents the temperature in the heat storage unit from decreasing because the storage medium is cooled by the cooler cooling medium.

[0048] As described above, the proportion of cooling medium supplied to the cooler depends on the temperature at which the cooling medium is to be supplied to the cooling process, the temperature of the cooling medium after transferring heat to the storage medium, and the temperature and mass flow rate of the flow supplied to the cooler. The proportion of cooling medium supplied to the cooler is selected such that, after remixing the cooled and uncooled portions of the cooling medium, the temperature at which the cooling medium is supplied to the cooling process is reached.

[0049] To enable heat to be transferred to the storage medium only from a portion of the cooling medium when the temperature of the cooling medium after heat absorption from the process and the temperature of the cooling medium supplied to the process for cooling are above the minimum storage temperature, and to prevent heat transfer from the storage medium to the cooling medium when the temperature of the cooling medium after heat absorption from the process is below the minimum storage temperature, it is preferred that the cooling circuit includes a bypass through which the cooling medium can flow in such a way that no heat is transferred to the storage medium.

[0050] Especially when a heat exchanger is used for heat transfer from the cooling medium to the storage medium, through which both the storage medium and the cooling medium flow, it is also possible to stop the supply of storage medium to the heat exchanger when no more heat transfer from the cooling medium to the storage medium is desired. However, since it cannot be ruled out that a minimum storage temperature will develop in the thermal storage system, which is so low that the cooling medium is cooled by heat transfer to the storage medium to a temperature below that at which the cooling medium is supplied to the process, it is also necessary in this case to provide a bypass to divert a portion of the cooling medium in such a way that it does not transfer heat to the storage medium.

[0051] As an alternative to the bypass, another heat exchanger could be used, in which the cooling medium is reheated slightly after transferring heat to the storage medium. However, this is less efficient and also requires additional equipment, so the bypass is preferred.

[0052] Since the cooling medium must be cooled further if no heat is transferred from the cooling medium to the storage medium, or if the temperature of the cooling medium after heat transfer to the storage medium is still above the temperature at which the cooling medium is supplied to the cooling process, the cooling medium must be cooled further, the cooling circuit 240348W001

[0053] 9 preferably a cooler. In order for the cooling medium to be cooled further after transferring heat to the storage medium, the cooler is preferably arranged in the cooling circuit downstream of the point where the cooling circuit is coupled to the heat storage. In order to supply only a portion of the cooling medium to the cooler, it is further preferred if at least one additional bypass is included through which the cooling medium can flow past the cooler.

[0054] The at least one additional bypass can, for example, branch off from the cooling circuit downstream of the point where the cooling circuit is coupled to the heat storage unit and upstream of the cooler, and rejoin the cooling circuit downstream of the cooler. Alternatively, or preferably, an additional bypass is included that is arranged upstream of the point where the cooling circuit is coupled to the heat storage unit. In particular, if the temperature of the cooling medium after heat transfer to the storage medium is below the temperature at which the cooling medium is to be returned to the process, the temperature of the cooling medium can be increased in this way by mixing in warm cooling medium taken from the process, thus setting the desired temperature at which the cooling medium is to be returned to the process.

[0055] To utilize the waste heat from the process, according to the invention, a portion of the storage medium contained in the heat storage unit is used for steam generation. Through steam generation, heat is released from the storage medium contained in the heat storage unit, so that the average temperature of the storage medium in the heat storage unit is below the temperature at which the storage medium is supplied to the heat storage unit after absorbing heat from the cooling medium.

[0056] A heat pump is preferably used as the steam generation device. The heat pump can be an open-loop or closed-loop heat pump.

[0057] In a closed-loop heat pump, heat is extracted from the storage medium in the heat storage unit and transferred to a working fluid in a first heat exchanger, causing the working fluid to evaporate. The evaporated working fluid is then compressed, further heating it during the compression process. In a second heat exchanger, the working fluid releases heat to a water stream, causing at least some of the water to evaporate. After releasing heat to the water, the working fluid is expanded in an expansion device, such as a throttle or turbine, where it cools down and condenses, provided it has not already condensed due to heat loss in the second heat exchanger. It can then absorb heat again in the first heat exchanger.

[0058] As an alternative to the second heat exchanger in the closed circuit, it is also possible to initially heat a water flow only in the heat exchanger by heat transfer. 240348W001

[0059] 10 men and a portion of the water are subsequently evaporated in a flash evaporator. In this case, the evaporated portion is withdrawn from the flash evaporator as steam, and the unevaporated portion is returned to the second heat exchanger.

[0060] Suitable working fluids for use in a closed loop include, for example, synthetic working fluids such as hydrofluoroolefins, preferably R1336mzz(Z), R1233zd(E) and R1234ze(Z), as well as natural hydrocarbons, preferably R600 (n-butane), R600a (isobutane) and R601 (pentane), and inorganic compounds, preferably R717 (ammonia) or carbon dioxide.

[0061] Unlike a closed-circuit heat pump, in an open-circuit heat pump, heat is transferred from the storage medium taken from the heat storage unit to the water via indirect heat transfer in a heat exchanger or evaporator.

[0062] In a first embodiment of an open-circuit heat pump, the portion of the storage medium extracted for steam generation transfers heat to a water stream in a heat exchanger, thereby heating the water stream. The heated water stream is fed to a flash evaporator, where it expands, causing a portion of the water stream to evaporate and be extracted as steam. The unevaporated portion is returned to the heat exchanger. The flash evaporator heat pump is preferably used when the storage medium extracted from the heat storage tank for steam generation has a temperature in the range of 20 to 250 °C, more preferably in the range of 70 to 200 °C, and particularly in the range of 90 to 165 °C.The water flow supplied to the heat exchanger preferably has a pressure in the range of 0.1 to 20 bar (abs), more preferably in the range of 0.6 to 16 bar (abs), and particularly in the range of 1 to 6.5 bar (abs), and is preferably heated in the heat exchanger to a temperature in the range of 40 to 210 °C, more preferably in the range of 80 to 195 °C, and particularly in the range of 95 to 158 °C. In the flash evaporator, the water flow is depressurized to a pressure below the boiling point at the temperature at which the water is supplied to the flash evaporator. Preferably, the water flow in the flash evaporator is depressurized to a pressure in the range of 0.01 to 19.9 bar (abs), more preferably to a pressure in the range of 0.3 to 15.9 bar (abs), and particularly to a pressure in the range of 0.7 to 6 bar (abs).The portion taken from the flash evaporator and returned to the heat exchanger is first compressed to the pressure at which the water stream is supplied to the heat exchanger and then mixed with the water stream.

[0063] The proportion of water that is evaporated in the flash evaporator is preferably in the range of 0.15 to 35 wt.%, more preferably in the range of 0.5 to 9 wt.% and particularly in the range of 2.3 to 5 wt.%, based on the total mass flow of water.

[0064] Any heat exchanger known to a specialist can be used as a heat exchanger, in which heat is transferred indirectly from one medium to another. 240348W001

[0065] 11 is transferred. Suitable heat exchangers include, for example, shell and tube heat exchangers, plate heat exchangers, spiral heat exchangers, or double-pipe heat exchangers or jacketed tube heat exchangers.

[0066] A flash container with a throttle at the inlet is suitable as a flash evaporator, for example, so that the water flow into the flash container is relaxed when passing the throttle.

[0067] In a second embodiment of an open-vent heat pump, the portion of the storage medium extracted for steam generation transfers heat to a water stream in an evaporator, causing the water stream to at least partially evaporate. If only partially evaporated, the partially evaporated water stream is fed to a phase separator. The evaporated portion is extracted from the phase separator as steam, and the unevaporated portion is returned to the evaporator. This embodiment is preferably used when the storage medium extracted from the heat storage tank for steam generation has a temperature in the range of 20 to 250 °C, more preferably in the range of 70 to 200 °C, and particularly in the range of 90 to 165 °C. The water stream supplied to the evaporator preferably has a pressure in the range of 0.1 to 20 bar (abs), more preferably in the range of 0.6 to 16 bar (abs), and particularly in the range of 1 to 6.5 bar (abs).Preferably 0.15 to 100 wt.%, more preferably 20 to 100 wt.% and in particular 80 to 100 wt.% are evaporated in the evaporator.

[0068] The phase separator downstream of the evaporator can be operated at the same pressure as the water flow entering it. Alternatively, it is also possible to operate the phase separator at a lower pressure, so that a further portion of the water flow evaporates due to expansion upon entering the phase separator. This is particularly advantageous if the amount of water already evaporated in the evaporator is insufficient to generate steam efficiently and effectively.

[0069] If not only part of the water stream is to be evaporated in the evaporator, but the entire water stream, the phase separator can be omitted, since in this case no liquid water needs to be separated from the evaporated stream.

[0070] Any suitable evaporator, as determined by those skilled in the art, can be used for at least the partial evaporation of a water stream. Suitable evaporators include, for example, shell-and-tube evaporators, falling-film evaporators, or boiler evaporators, with falling-film evaporators being preferred.

[0071] Especially when the storage medium is water, it is also possible to feed the storage medium directly to an evaporator of an open-vent heat pump for evaporation and to generate steam from the storage medium. In this case, the first heat exchanger, in which heat is transferred from the storage medium to the working fluid of a closed-vent heat pump or to water in an open-vent heat pump, can be omitted. 240348W001

[0072] 12

[0073] For evaporation, the warm water used as a storage medium is preferably fed into a flash evaporator, a device for steam generation, in which a portion of the water evaporates by expansion to a lower pressure. The unevaporated portion of the water is returned to the heat storage unit.

[0074] Depending on the intended use of the steam and the pressure of the steam generated in the steam generation system, the steam can either be used directly or compressed to a higher pressure. In particular, if the steam was generated by evaporation in a flash evaporator, it is usually necessary to compress the steam to a higher pressure.

[0075] To compress the steam, at least one compressor is preferably arranged downstream of the evaporator.

[0076] The steam generated in the steam generation unit can either be supplied directly to a consumer or fed into a steam network that supplies steam to various consumers. In particular, when the steam is supplied directly to a consumer, it is possible to use the steam at the pressure it has during steam generation in the unit. When feeding it into a steam network or supplying it to a consumer for whom the temperature of the steam generated in the unit is too low, it is necessary to compress the steam. It is preferable to supply the consumers directly with the steam.

[0077] Low-pressure, medium-pressure, or high-pressure steam can be generated by compression in at least one compressor. It is also possible to first compress all the steam to low-pressure steam, provided the pressure in the steam generation system is below that of low-pressure steam, then to further compress at least a portion of the low-pressure steam to medium-pressure steam, and finally to compress at least a portion of the medium-pressure steam to high-pressure steam.

[0078] In the context of the present invention, low-pressure steam is understood to mean steam having a pressure in the range of 0.9 to 4 bar(abs), preferably in the range of 1 to 2 bar(abs) and particularly in the range of 1.2 to 1.5 bar(abs) and a temperature in the range of 96 to 160 °C, more preferably in the range of 99 to 140 °C and particularly in the range of 104 to 120 °C.

[0079] Medium-pressure steam within the scope of the present invention is steam with a pressure in the range of 4 to 8 bar(abs), preferably in the range of 4.5 to 7 bar(abs) and particularly in the range of 5 to 6 bar(abs) and a temperature in the range of 143 to 220 °C, more preferably in the range of 147 to 210 °C and particularly in the range of 151 to 200 °C. 240348W001

[0080] 13

[0081] High-pressure steam within the scope of the present invention is steam with a pressure in the range of 8 to 40 bar(abs), preferably with a pressure in the range of 10 to 30 bar(abs) and in particular with a pressure in the range of 16 to 20 bar(abs) and a temperature in the range of 170 to 280 °C, more preferably in the range of 180 to 260 °C and in particular with a temperature in the range of 201 to 240 °C.

[0082] To generate low-pressure, medium-pressure, or high-pressure steam, a compressor or a compressor cascade can be used. A compressor cascade with at least two compressors, in which the steam is compressed in stages, or a compressor with multiple compressor stages, such as a geared turbo compressor, is preferred. A geared turbo compressor typically includes several compression stages and intermediate stages, with intercooling possible in the respective intermediate stages. Even when a compressor cascade with multiple compressors is used, it is advantageous to implement intercooling between the individual compressors.

[0083] Water is typically injected into the steam for intercooling. Due to the temperature of the compressed steam, the water evaporates completely, cooling the steam and simultaneously increasing the steam volume. A sufficiently long injection section is provided to ensure that the injected water evaporates completely before subsequent compression in another compressor or compression stage.

[0084] The steam generated in this way is then extracted from the waste heat recovery device and supplied to a consumer or fed into a steam network.

[0085] Exemplary embodiments of the invention are shown in the figures and are explained in more detail in the following description.

[0086] They show:

[0087] Figure 1 shows a flow diagram of a device according to the invention for utilizing waste heat,

[0088] Figure 2 shows a control concept for a device according to the invention for the utilization of waste heat,

[0089] Figure 3a Temperature in the heat storage unit as a function of time,

[0090] Figure 3b Mass flow rate of generated steam as a function of time,

[0091] Figure 3c Process return temperature, setpoint of coolant supply temperature and achieved temperature as a function of time;

[0092] Figure 4 shows a section of the diagram depicted in Figure 3c. 240348W001

[0093] 14

[0094] Figure 1 shows a flow diagram of a device according to the invention for utilizing waste heat.

[0095] After absorbing heat from a process, a cooling medium from a cooling circuit 1, of which only the part relating to heat storage and use is shown here, is fed to a heat exchanger 3, in which the cooling medium can transfer heat to a storage medium.

[0096] In order to provide the possibility of passing only a portion of the cooling medium or no cooling medium at all through the heat exchanger 3 during the operation of the process, the cooling circuit 1 has a bypass 5 through which cooling medium can flow without passing through the heat exchanger 3.

[0097] If the cooling medium downstream of the heat exchanger 3 has a temperature higher than the temperature at which it is to be returned to the process, the cooling circuit 1 includes a cooler 7. To adjust the temperature of the cooling medium, a further bypass 9 is included, through which at least a portion of the cooling medium can flow past the cooler 7. If the cooling medium in the cooler 7 is cooled to a temperature below the temperature at which it is to flow back into the process for further heat absorption, a portion of the warmer cooling medium can flow past the cooler 7 through the further bypass 9. Downstream of the cooler 7, the two flows are mixed again, resulting in a temperature higher than the temperature at which the cooling medium left the cooler 7.

[0098] If, after transferring heat to the storage medium in the heat exchanger 3, the cooling medium has a temperature below the temperature at which the cooling medium is to be returned to the process, the cooling medium is directed through the further bypass 9 after flowing through the heat exchanger 3, and additionally, a portion of the cooling medium that has absorbed heat from the process is directed through a second further bypass 11 and mixed with the portion of the cooling medium that has flowed through the heat storage medium, so that after the mixture the cooling medium has a temperature above the temperature at which the cooling medium left the heat exchanger and corresponds to the temperature at which the cooling medium is to be returned to the process.Of course, to adjust the temperature of the cooling medium that is returned to the process, cooling medium that has flowed through cooler 7 can also be mixed with cooling medium that has passed through the second additional bypass 11, so that the second additional bypass 11 is used instead of the additional bypass 9, or cooling medium can be passed through cooler 7, the additional bypass 9 and the second additional bypass 11 to adjust the temperature of the cooling medium that is returned to the process. The flow rates through cooler 7, the additional bypass 9 and the second additional bypass 11 240348W001.

[0099] 15 depend on the quantity and temperature of the cooling medium that has transferred heat to the storage medium in the heat exchanger 3 and on the temperature to which the cooling medium is cooled in the cooler ? if cooling medium flows through this.

[0100] After the storage medium in the heat exchanger 3 has been heated by heat transfer from the cooling medium, it is fed into a thermal storage unit 13. In the thermal storage unit, the storage medium can be mixed, resulting in a substantially constant temperature. Alternatively, and preferably, the storage medium in the thermal storage unit exhibits a temperature profile. Here, the storage medium can have a continuous temperature profile or form different layers with varying temperatures, making the thermal storage unit 13 a stratified storage unit. If the thermal storage unit is a stratified storage unit, the storage medium forms at least two temperature layers: one layer with a high temperature and one layer with a low temperature.

[0101] If the storage medium in the thermal storage unit 13 has a substantially constant temperature, it is possible to feed the storage medium into the thermal storage unit at any point after heat absorption in the heat exchanger. If the storage medium has a continuous temperature profile or forms several layers with different temperatures, the storage medium is fed into the thermal storage unit 13 at a position where storage medium with a similar temperature is located.

[0102] To absorb heat, storage medium is extracted from the heat storage unit 13 and fed to the heat exchanger 3. If the storage medium in the heat storage unit 13 has a substantially constant temperature, it can be extracted from any position within the unit. If the storage medium has a temperature profile, it is preferably extracted from a point where it has a minimum temperature. Since the density generally decreases with increasing temperature, the storage medium is preferably fed into the upper region of the heat storage unit 13 and extracted from the lower region.

[0103] The heat exchanger 3, in which heat is transferred from the cooling medium to the storage medium, can be located inside or, as shown here, preferably outside the heat storage unit 3. To supply the storage medium from the heat storage unit 13 to the heat exchanger 3 and, after heat absorption in the heat exchanger 3, to return it to the heat storage unit 13, a line 15 is provided in which a pumping device 17, preferably a pump, is housed. The pump regulates the flow of the storage medium through the heat exchanger 3 as a function of the flow of the cooling medium through the heat exchanger 3.

[0104] To utilize the heat of the storage medium, a portion of the storage medium from the thermal storage unit 13 is fed to a heat exchanger 19 of a steam generation unit 21, in which water is heated. Since the storage medium is cooled by the heat transfer to the water, when the storage medium in the thermal storage unit 13 reaches a temperature of 240348W001

[0105] 16

[0106] The temperature profile is such that the storage medium is extracted at a position where it has a high temperature and returned to the thermal storage unit 13 at a position where it has a minimum temperature. However, if the temperature of the storage medium in the thermal storage unit 13 is constant, the storage medium can be extracted and returned at any position.

[0107] To generate steam, the water, after being heated in the heat exchanger 19, is fed to a flash evaporator 23. In the flash evaporator, a portion of the water evaporates by expanding to a lower pressure. The evaporated portion is extracted as steam, and the unevaporated portion is returned to the heat exchanger 19. Here, the water extracted from the flash evaporator 23 is compressed to a higher pressure in a pump 27 so that it can expand again in the flash evaporator after absorbing heat.

[0108] Since the total amount of water decreases due to steam withdrawal, it is necessary to supply fresh water. Preferably, the fresh water is supplied directly to the flash evaporator 23 or, more preferably, via a fresh water line 29 between the flash evaporator and the pump 27. Demineralized and degassed water is preferably supplied as fresh water.

[0109] Alternatively, the steam generation device 21 may include an evaporator in which water is at least partially evaporated by heat transfer from the storage medium. If the water is partially evaporated, a phase separator is connected downstream of the evaporator, in which the evaporated portion is separated from the unevaporated portion and extracted as steam. The unevaporated portion is returned to the evaporator. To increase the steam output, the phase separator can be operated at a lower pressure than the evaporator, so that further water evaporates upon entering the phase separator.

[0110] If all the water in the evaporator evaporates, the phase separator can be omitted.

[0111] If steam is to be used directly, it can be drawn off, for example, via a steam line 25. If the steam cannot be used at the pressure at which it is drawn from the steam generation unit 21, but requires a higher pressure, the steam drawn off via the steam line 25 can be fed to at least one compressor. A multi-stage compressor is typically used to compress the steam, and additional water can be injected after the compressor stages for cooling. The water injected after the compression stages can be either unevaporated water drawn from the steam generation unit 21 or fresh water. The compressed steam leaving the compressor can then be fed, for example, into a steam network. 240348W001

[0112] 17

[0113] A control concept for the device according to the invention is shown in Figure 2.

[0114] All regulations in the regulatory concept are designed as PID regulations.

[0115] After heat absorption in a process not shown here, the temperature of the cooling medium is measured by a first temperature controller 31. The first temperature controller 31 also receives the temperature in the heat storage tank 13, measured by a second temperature controller 33, as an additional input. The difference between the temperature of the cooling medium and the temperature in the storage tank is calculated. As soon as this difference exceeds a setpoint, at least some of the cooling medium is directed into a line 34 leading to a split point, where a supply line 35 branches off to the heat exchanger 3. If the temperature falls below the setpoint, more cooling medium is diverted around the heat exchanger 3 via a bypass line 37.

[0116] To adjust the flow rate, the current amount of cooling medium is measured using a flow controller 39 and a pump 41 in the cooling circuit 1 is controlled.

[0117] Depending on the temperature of the storage medium in the thermal storage unit 13, if a temperature difference greater than the setpoint has been established by the first temperature controller 31, at least a portion of the cooling medium can be supplied to the heat exchanger 3 via the supply line 35. The cooling medium not supplied to the heat exchanger 3 is routed around the heat exchanger via the bypass 5. After passing through the heat exchanger 3, the cooling medium is returned to the cooling circuit 1 and mixed with the cooling medium that bypassed the heat exchanger 3. The mixed temperature of the cooling medium after mixing is measured by a third temperature controller 43.

[0118] The amount of cooling medium supplied to the heat exchanger 3 depends on the temperatures detected by the second temperature controller 33 and the third temperature controller 43.

[0119] To determine the ratio of the amount of cooling medium supplied to the heat exchanger 3 and the amount of cooling medium routed through the bypass 5, the mixture temperature detected by the third temperature controller 43 is first compared with a target value. The target value is the temperature specified by the process control system for the inflow to the process being cooled. If the temperature detected by the third temperature controller 43 is above the target value, the third temperature controller 43 specifies a higher setpoint for the proportion of cooling medium flow supplied to the heat exchanger 3, and if the temperature detected by the third temperature controller 43 is below the target value, the setpoint for the cooling medium flow supplied to the heat exchanger 3 is decreased.

[0120] The second temperature controller 33 receives the temperature at the top of the heat storage unit 13 as its input. The target value for the second temperature controller 33 is a predefined value for 240348W001.

[0121] 18 the maximum temperature in the heat storage unit 13. If the temperature measured by the second temperature controller 33 is below the maximum temperature in the heat storage unit 13, the second temperature controller 33 specifies a higher setpoint for the proportion of coolant flow to be supplied to the heat exchanger 3 in order to heat a larger quantity of storage medium. As soon as the temperature in the heat storage unit 13 approaches the target temperature, i.e., the maximum temperature in the heat storage unit 13, the setpoint is reduced so that less storage medium is heated to prevent overheating.

[0122] Since the amount of cooling medium supplied to the heat exchanger 3 affects both the mixture temperature, which is measured by the third temperature controller 43, and the temperature in the heat storage tank 13, which is measured by the second temperature controller 33, the coupling of the second temperature controller 33 and the third temperature controller 43 is crucial for determining the setpoint for the valves that regulate the amount of cooling medium flowing through the bypass 5 and the amount of cooling medium supplied to the heat exchanger 3. For this purpose, it is possible, for example, to always use the smaller of the setpoints determined by the second temperature controller 33 and the third temperature controller 43 for the amount of cooling medium supplied to the heat exchanger 3. Alternatively, the two setpoints can be multiplied, with the setpoints taking a value between 0 and 1.“0” means that no cooling medium is supplied to the heat exchanger 3, but the entire cooling medium is routed through the bypass 5, and “1” means that the entire cooling medium is supplied to the heat exchanger 3 and no cooling medium flows through the bypass 5.

[0123] For example, the second temperature controller 33 might, at a low storage medium temperature, specify that all of the cooling medium should be supplied to the heat exchanger 3, i.e., it sets a setpoint of 1. However, since in this case the cooling medium temperature would be too low for supply to the process, and a mixing temperature must be set that requires part of the cooling medium to flow through bypass 5, the third temperature controller 43 specifies that only part of the cooling medium can be supplied to the heat exchanger 3 and the other part should flow through bypass 5. If, for example, half of the cooling medium is to be supplied to the heat exchanger 3, the setpoint determined by the third temperature controller 43 is 0.5.In this case, both in the variant where the smaller control value is used and in the case of multiplication of the control values, the control value to be used would be 0.5, meaning that one half of the cooling medium is supplied to the heat exchanger 3 and the other half is routed through the bypass 5.

[0124] When the temperature of the storage medium approaches the maximum temperature in the heat storage unit 13, the second temperature controller 33 specifies a smaller setpoint, for example, a setpoint of 0.05. However, if, on the other hand, a larger quantity of cooling medium is to be supplied to the heat exchanger 3 to achieve the desired mixing temperature, for example, 70% of the cooling medium, the third temperature controller 43 specifies a setpoint of 0.7. Using the smaller setpoint, 5% of the cooling medium would be supplied to the heat exchanger 3 in this case, or, in the case of multiplying the setpoints, 240348W001

[0125] 19 only 3.5% of the cooling medium. Due to the small amount of cooling medium supplied to the heat exchanger 3, the mixture temperature is too high, so that in this case the cooling medium must be cooled further downstream of the third temperature controller 43 in the cooler 7.

[0126] To regulate the flow through the cooler 7, a fourth temperature controller 45 regulates the ratio of the partial flows passing through the cooler 7 and through the further bypass 9, based on the temperature of the cooling medium supplied to the process to be cooled and a setpoint corresponding to the desired supply temperature to the process to be cooled. Furthermore, the fourth temperature controller 45 also regulates the flow rate of coolant for cooling the cooling medium through the cooler 7.

[0127] For steam generation, storage medium is extracted from the heat storage unit 13 and fed to a steam generation device, in which the heat from the storage medium is used to generate steam. Preferably, the storage medium is fed to the heat exchanger 19, in which heat is transferred to a working fluid of a closed-loop heat pump or in which water is directly heated for an open-loop heat pump.

[0128] The flow to the heat exchanger 19 is regulated by a second flow controller 47 via a pump 49. The setpoint for the flow rate is calculated based on the currently required amount of energy. This required amount of energy can vary depending on the temperature in the heat storage tank and the required amount of steam. Both discrete steps based on threshold values ​​and continuous dependencies are possible. It is also possible to establish a cascade control system in which an intermediate controller 51 receives the target energy value and then varies the setpoint for the flow rate until the desired amount of energy is achieved.

[0129] The flow rate of working fluid for a closed heat pump or of water for an open heat pump through the heat exchanger 19 is regulated by a fifth temperature controller 53. The input variable here is the temperature of the storage medium, which is returned to the heat storage tank 13 after flowing through the heat exchanger 19. The setpoint for the control is determined by the temperature of the steam generation.

[0130] Example

[0131] The process for utilizing waste heat is simulated using a simulation program, whereby the control system shown in Figure 2 is modeled using the simulation program.

[0132] To simplify the simulation, the process being cooled and the compressor are not included. This is achieved by specifying that the compressor automatically operates within its load range of 60 and 100% depending on the temperature in the heat storage unit 13, and that the process follows a predetermined 240348W001

[0133] The coolant flow rate is derived from real operating data, assuming water as the coolant. The supply temperature to the process is also derived from real data.

[0134] Furthermore, heat losses to the environment are neglected in the simulation, so that, for example, the heat storage unit 13 does not release any heat to the environment.

[0135] The simulation tests the control concept shown in Figure 2, including the control loops. Impermissible temperature exceedances or other impermissible operating points become apparent.

[0136] Furthermore, the simulation checks the behavior of the fill level and temperature in the heat storage unit 13, as well as the flow temperature in the cooling circuit downstream of the cooler 7 and in the heat exchanger 19, the flow rate from the heat storage unit 13 to the heat exchanger 19 and the flow rate from the cooling circuit 1 to the heat exchanger 3.

[0137] A continuous storage control system is simulated, in which the heat flow rate supplied to the evaporator for steam generation can assume all values ​​between a minimum and a maximum heat flow rate. A heat exchanger is assumed to be the evaporator.

[0138] The following input parameters are used for the simulation:

[0139] The mass flow rate and temperature of the coolant after heat absorption from the process are transmitted to the simulation model as a function of time;

[0140] The target value for the process flow temperature is transmitted to the simulation model as a function of time;

[0141] The target pressure is 0.4 bar (abs);

[0142] The target value for the coolant flow rate is 375 m³ / h. 3 / h

[0143] The target value for the difference between return temperature and storage temperature is 9 °C;

[0144] The heat storage unit operates within a temperature range of 90 to 100 °C;

[0145] The heat storage unit has a volume of 3000 m³ 3 up and the target value for the fill level is 90% of the total volume;

[0146] A heat transfer coefficient of 1072 kW / K is assumed for the cooler; 240348W001

[0147] 21

[0148] A heat transfer rate of 1072 kW / K is assumed for the heat transfer from the cooling medium to the storage medium in the heat exchanger 3;

[0149] A heat transfer rate of 1072 kW / K is assumed for the heat transfer from the storage medium to the working fluid of the heat pump in the heat exchanger 19;

[0150] Steam generation is stopped when the temperature in the heat storage tank falls below 90 °C and resumes at minimum load when the temperature rises above 91 °C;

[0151] When the storage medium temperature reaches 95 °C, steam generation is increased from minimum to maximum load. When the temperature drops below 93 °C, steam generation is switched from maximum to minimum load.

[0152] The maximum energy output for the steam is 300 kW and the minimum energy output is 90 kW.

[0153] The following starting parameters are set at the beginning of the simulation:

[0154] The starting temperature of the heat storage unit is 90 °C;

[0155] The liquid volume in the heat storage tank is initially 3000 m³. 3 ;

[0156] The amount of heat supplied for steam generation is initially 0 kW.

[0157] The results of the simulation are shown in Figures 3a to 3c, where the simulation simulates operation over 270 hours.

[0158] Figure 3a shows the temperature in the heat storage tank over time in hours. Figure 3b shows the mass flow rate of the generated steam over time in hours, and Figure 3c shows the temperature of the water used as a cooling medium after heat absorption from the process (solid line 61), the setpoint temperature for the supply temperature of the cooling medium to the process being cooled (line 63), and the actual supply temperature of the cooling medium to the process being cooled (dashed line 65), where the process is operated as a batch process. For clarity, Figure 4 shows the first 50 hours of the process return temperature (61), the setpoint (63) for the supply temperature of the cooling medium to the process from which heat is absorbed, and the actual supply temperature (65) of the cooling medium to the process from which heat is absorbed.

[0159] The simulation results show that the heat storage unit 13 operates within the planned temperature window, even when the process is operated as a batch process and therefore the 240348W001

[0160] The amount of heat released by the process varies over time. Furthermore, the planned switching of steam generation takes place between maximum load, reduced load, and periods of no operation.

[0161] The desired supply temperature of the cooling medium for the process to be cooled is reliably achieved, so that stable operation of the process is possible even with heat integration.

Claims

240348W001 23 Patent claims 1. Device for the utilization of waste heat comprising a cooling circuit (1) coupled to a heat storage unit (13) and a steam generation device (21), wherein the heat storage unit (13) contains a liquid storage medium and the cooling circuit (1) is coupled to the heat storage unit in such a way that heat can be transferred from a cooling medium flowing through the cooling circuit (1) to the storage medium and the steam generation device (21) comprises an evaporator coupled to the heat storage unit (13) in such a way that a storage medium flow from the heat storage unit (13) can be used as a heat source for steam generation.

2. Device according to claim 1, characterized in that the cooling circuit (1) comprises a bypass (5) through which cooling medium can flow in such a way that no heat is transferred to the storage medium.

3. Device according to claim 1 or 2, characterized in that a heat exchanger (3) is included which is incorporated in the cooling circuit (1) and in which heat is transferred from the cooling medium to the storage medium.

4. Device according to one of claims 1 to 3, characterized in that a cooler (7) is arranged in the cooling circuit (1 ) downstream of the point where the cooling circuit (1 ) is coupled to the heat storage unit (13).

5. Device according to one of claims 1 to 4, characterized in that at least one further bypass (9, 11) is included through which the cooling medium can flow past the cooler (7).

6. Device according to one of claims 1 to 5, characterized in that water is at least partially evaporated in the evaporator by indirect heat transfer from the storage medium to the water.

7. Device according to claim 6, characterized in that the evaporator is a flash evaporator (23).

8. Device according to one of claims 1 to 7, characterized in that at least one compressor for compressing the steam is arranged downstream of the evaporator.

9. Method for utilizing waste heat in a device according to any one of claims 1 to 8, comprising: 240348W001 24 (a) Cooling of a process, wherein the cooling medium absorbs heat from the process; (b) Transfer of heat to the storage medium when the cooling medium has a temperature above a minimum storage temperature and no heat transfer to the storage medium when the cooling medium has a temperature below the current minimum storage temperature; (c) Extraction of part of the storage medium from the heat storage unit (13) and use of part of the cooling medium as a heat source for steam generation in the steam generation unit (21).

10. Method according to claim 9, characterized in that the portion of the storage medium withdrawn for steam generation releases heat to a water stream in a heat exchanger (19), thereby heating the water stream, the heated water stream is fed to a flash evaporator (23) in which the water stream is expanded, so that a portion of the water stream evaporates and is withdrawn as steam and the unevaporated portion is returned to the heat exchanger (19).

11. Method according to claim 9, characterized in that the portion of the storage medium withdrawn for steam generation releases heat to a water stream in an evaporator, wherein the water stream is at least partially evaporated, in the case of partial evaporation the partially evaporated water stream is fed to a phase separator, the evaporated portion is withdrawn from the phase separator as steam and the unevaporated portion is returned to the evaporator, and in the case of complete evaporation the steam is withdrawn from the evaporator.

12. Method according to one of claims 9 to 11, characterized in that the steam is compressed.

13. A method according to any one of claims 9 to 12, characterized in that, after heat absorption from the process, the cooling medium is separated into a first part and a second part, the first part of the cooling medium transfers heat to the storage medium and the second part does not transfer heat to the storage medium, and after heat transfer to the storage medium, the first and second parts of the cooling medium are mixed again if the temperature of the cooling medium after heat absorption from the process and the temperature of the cooling medium supplied to the process for cooling are above the minimum storage temperature, or that the entire cooling medium releases heat to the storage medium and at least a part of the cooling medium is cooled in the cooler (7) after heat release to the storage medium if the temperature of the cooling medium after heat absorption from the process is above the minimum storage temperature and the temperature of the cooling medium is above the minimum storage temperature. 240348W001 25. The medium supplied to the process for cooling is below the minimum storage temperature, or that no heat is transferred from the cooling medium to the storage medium when the temperature of the cooling medium after heat absorption from the process is below the minimum storage temperature.

14. Method according to one of claims 9 to 13, characterized in that the storage medium in the heat storage unit (13) has a temperature profile, wherein, after absorbing heat from the cooling medium, the storage medium is introduced into the heat storage unit (13) at a position where storage medium with a similar temperature is located, and storage medium is withdrawn to absorb heat from the cooling medium at a position where storage medium with a minimum temperature is located, and storage medium is withdrawn as a heat source for steam generation at the position where the storage medium with the maximum temperature is located, and the storage medium is supplied to the steam generation unit at the position where the storage medium with the minimum temperature is located after releasing heat.

15. A method according to any one of claims 9 to 14, characterized in that the process comprises a chemical reaction, cooling of a material stream or cooling of an apparatus.

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