Carbon dioxide separation plant with ammonia scrubbing

Abstract

Plant (400) for the separation of carbon dioxide, in which the necessary thermal energy is provided by utilizing waste heat within the system and transported by a heat pump system, and process for the separation of carbon dioxide in the plant.

Description

[0001] The invention relates to a plant for the separation of carbon dioxide and a method for the separation of carbon dioxide in this plant.

[0002] The aqueous ammonia carbon capture process is a technology for capturing carbon dioxide (CO2), primarily from industrial sources. This process uses an aqueous ammonia solution to absorb CO2, preferably at low temperatures, which significantly increases capture efficiency while minimizing ammonia emissions into the atmosphere. The industrial aqueous ammonia process for flue gas ultra-cleaning was first patented by Eli Gal (EP 1781400 A1). It was subsequently further developed through a series of demonstration plants and patents for industrial applications as chilled ammonia (Electric Power Research Institute (2011): Chilled Ammonia Process Development Unit at We Energies Pleasant Prairie Power Plant. Process Performance. 2011 Technical Report. Palo Alto (1017642); US2012258031 (A1)).

[0003] The cooled ammonia process offers many advantages compared to conventional amine-based carbon deposition technologies. - It is relatively stable in the presence of impurities in flue gases (SOx, NOx, etc.) and avoids oxidative degradation in the presence of O2. (Pérez Calvo, José Francisco (2021): Process Development and Optimization of Absorption-Based Post-Combustion CO2 Capture Technologies Applied to Industrial Point Sources. ETH Zurich) Ammonia can be synthesized from renewable energy sources and raw materials, making it a more environmentally friendly alternative to fossil solvents. - It is less corrosive and has a similar viscosity to water (Pérez-Calvo, José-Francisco; Sutter, Daniel; Gazzani, Matteo; Mazzotti, Marco (2017): Application of a Chilled Ammonia-based Process for CO2 Capture to Cement Plants. In Energy Procedia 114, pp. 6197-6205. DOI: 10.1016 / j.egypro.2017.03.1757) - It has a higher absorption capacity and lower regeneration energy requirements than conventional amines (Yang, Nan; Yu, Hai; Li, Lichun; Xu, Dongyao; Han, Wenfeng; Feron, Paul (2014): Aqueous Ammonia (NH 3) Based Post Combustion CO 2 Capture: A Review. In Oil Gas Sci. Technol. - Rev. IFP Energies nouvelles 69 (5), pp. 931-945. DOI: 10.2516 / ogst / 2013160). The heat energy requirement for regeneration in an aqueous ammonia-based carbon capture process can vary between 2.1 and 2.9 GJ / MT of captured CO2 (Pérez-Calvo 2021, so), which is quite low compared to a conventional carbon capture system based on monoethanolamine (MEA) (3.6 to 4 GJ / MT of captured CO2).

[0004] Aqueous ammonia carbon capture also has disadvantages. For example, the required cooling capacity (in terms of energy) is higher than the thermal energy required for regeneration and ammonia stripping. Therefore, a chiller fulfills the process requirement of cooling the flue gas, the absorption section, the water scrubber, and other streams at low temperatures. The chiller system results in an additional electricity demand for the overall system.

[0005] Similarly, the demand for thermal energy is quite high for both solvent regeneration (for CO2 removal) in the regenerator and ammonia stripping in the stripper. Furthermore, both columns operate at higher pressures, resulting in higher temperatures in the evaporators than in conventional amine-based systems. Thermal energy is traditionally supplied using fossil fuels. The heating energy is generally condensing low- to medium-pressure steam drawn from an upstream network (most likely from the low-pressure stages of the steam turbine or from the heat recovery section), resulting in a total energy loss of approximately 4.1–7% (EP1781400).

[0006] In current technology, chillers are used for cooling. The low-temperature waste heat dissipated by chillers (due to exothermic reactions in the absorber, water scrubbing columns, etc.) often remains unused and is released into the environment. This waste heat can also be of high quality, for example, for cooling the CO2 stream after regeneration, which could then be better utilized. Similarly, the waste heat dissipated by water in direct-contact coolers is released into the environment.

[0007] DE 10 2023 208 672 A1 shows a system for absorptive carbon dioxide capture with a heat pump.

[0008] US 2014 / 0196481A1 discloses a carbon dioxide removal system comprising a cooled ammonia CO2 capture system, an absorber cooling system in fluid communication with the cooled ammonia system, and a heat recovery steam generator in fluid communication with the cooled ammonia system and the absorber cooling system.

[0009] The object of the invention was to provide a system for the separation of carbon dioxide that is more energy-efficient.

[0010] The invention relates to a system for the separation of carbon dioxide and a method for the separation of carbon dioxide in this system according to the independent claims. Specific embodiments of the invention are specified in the dependent claims and this description.

[0011] The invention describes a system for the separation of carbon dioxide, comprising - an absorber in which an input stream containing carbon dioxide can be contacted with an aqueous ammonia solution, - a gas scrubber in which a first gaseous outflow obtained from the absorber can be contacted with scrubbing water for the removal of ammonia from the first gaseous outflow - a stripper in which gaseous carbon dioxide and gaseous ammonia can be driven off from the wash water in a second gaseous stream, - a first reboiler coupled to the stripper in a circuit, wherein the wash water in the circuit is circulated through the first reboiler to introduce heat energy into the wash water, - a connecting line from the stripper to the absorber, through which the second gaseous outflow from the stripper can be introduced into the absorber, - a regenerator into which a first liquid outflow obtained from the absorber can be introduced and in which gaseous carbon dioxide can be expelled from the first liquid outflow, - a second reboiler coupled to the regenerator in a circuit, wherein the first liquid outflow in the circuit is circulated through the first reboiler to introduce thermal energy into the first liquid outflow, - a gas outlet through which a third gaseous outflow can be extracted from the regenerator, containing gaseous carbon dioxide, - a heat pump comprising a refrigerant and at least one refrigerant circuit designed in which a refrigerant flow circulates, wherein the following are provided in the refrigerant circuit • a liquefier, • a first expansion valve and a second expansion valve, • a first evaporator and a second evaporator, • a first compressor and a second compressor, wherein, with respect to a direction of circulation of the refrigerant circuit, the refrigerant circuit after the condenser has a first branch into a first circuit subsection and a second circuit subsection, and the refrigerant circuit before the condenser has a first union of the first circuit subsection and the second circuit subsection, wherein the first evaporator is arranged in the first circuit section and the second evaporator is arranged in the second circuit section, wherein, with regard to the direction of circulation, the first expansion valve is arranged upstream of the first evaporator, wherein, with regard to the direction of circulation, the first compressor is arranged after the first evaporator, wherein, with respect to the direction of circulation, the second expansion valve is located in the second circuit section and upstream of the second evaporator, and, with respect to the direction of circulation, the second compressor is located in the second circuit section and downstream of the second evaporator, wherein the first evaporator is a first heat exchanger or is connected to a first heat exchanger, wherein the first heat exchanger is configured to transfer heat energy from the second gaseous outflow and / or (preferably “and”) from the third gaseous outflow to the refrigerant at a first pressure and a first temperature of the refrigerant, wherein the second evaporator is a second heat exchanger or is connected to a second heat exchanger, wherein the second heat exchanger is configured to transfer thermal energy from the input stream and / or (preferably “and”) from at least one chiller of the system to the refrigerant at a second pressure and a second temperature of the refrigerant, wherein the second pressure is lower than the first pressure and the second temperature is lower than the first temperature, wherein the condenser is a third heat exchanger connected to or integrally designed with the first reboiler and / or (preferably "and") the second reboiler, and configured to transfer thermal energy from the refrigerant to the wash water and / or (preferably "and") the first liquid outflow.

[0012] The present invention enables the most complete possible coverage of energy needs. It goes beyond the concept of the heat pump, which replaces the function of the refrigeration unit in an integrated system.

[0013] The existing system according to the prior art relies on an external supply of thermal energy, whereas the invention presented here generates the thermal energy within the system. The invention presented here generates the necessary thermal energy by utilizing waste heat within the system.

[0014] The advantages of the invention are explained in more detail in the exemplary embodiments.

[0015] With regard to the direction of circulation, the first expansion valve is preferably either • before the first branching or • arranged after the first branch in the first section of the cycle.

[0016] With regard to the direction of circulation, the first compressor is preferably either • before the first union in the first circulatory segment or • after the first unification arranged.

[0017] The aforementioned first assembly can be designed as a mixer, in particular a mixing vessel.

[0018] The aforementioned second assembly can be designed as a mixer, in particular a mixing vessel.

[0019] In one embodiment of the system, the first temperature is in the range of 60 to 90°C and the second temperature is in the range of 10 to 40°C.

[0020] The pressure depends heavily on the choice of refrigerant (since it is a constant-temperature system, i.e., a two-phase fluid). For example, when using pure ammonia as the working / refrigerant, the first pressure might be in the range of 25 to 50 bar, and the second pressure in the range of 6 to 16 bar.

[0021] In one embodiment of the system, the heat pump features: • a third expansion valve • a third evaporator • a third compressor wherein, with respect to a direction of circulation of the refrigerant circuit, the refrigerant circuit has a second branch after the first branch from the second circuit section to a third circuit section, and the refrigerant circuit has a second junction before the condenser and before the first junction, in which the third circuit section and the second circuit section are joined, wherein the third evaporator is arranged in the third circuit section, wherein, with regard to the direction of circulation, the third expansion valve is arranged upstream of the third evaporator, wherein, with regard to the direction of circulation, the third compressor is arranged after the third evaporator, wherein the third evaporator is at least a fourth heat exchanger or is connected to at least a fourth heat exchanger, wherein the at least a fourth heat exchanger is configured to transfer heat energy from the system to the refrigerant at a third pressure and a third temperature of the refrigerant, wherein the third pressure is lower than the second pressure and the third temperature is lower than the second temperature.

[0022] The aforementioned embodiment has the particular advantage that the at least one fourth heat exchanger can replace at least one chiller in the system according to the prior art. Preferably, several fourth heat exchangers replace several chillers, with each heat exchanger preferably replacing one chiller. Furthermore, with such a system, the heat pump can dissipate more heat energy than is required in the aforementioned reboilers. Thus, excess energy can be provided that can be used in other processes.

[0023] In this embodiment, the second heat exchanger is preferably configured to transfer thermal energy from the inlet stream, but not from at least one chiller in the system, to the refrigerant at a second pressure and temperature. This is preferred because, in this embodiment, chillers in the system are replaced by a fourth heat exchanger, so no thermal energy from chillers is available.

[0024] In one embodiment of the system, the heat energy transferred from the fourth heat exchanger in the system to the refrigerant originates from one or more of the following: - the input stream, which has preferably already been cooled by the second heat exchanger, - the second gaseous outflow, which has preferably already been cooled by the first heat exchanger, - the wash water, - aqueous ammonia solution, which is taken from the absorber and recirculated into the absorber, and / or - the third gaseous outflow, which has preferably already been cooled by the first heat exchanger.

[0025] In one embodiment of the system, the third temperature is in the range of 0 to 10°C.

[0026] The pressure depends heavily on the choice of refrigerant (since it is a constant-temperature system, i.e., a two-phase fluid). For example, when using pure ammonia as the working / refrigerant, the third pressure can be in the range of 4 to 6 bar.

[0027] In another aspect, the invention relates to a method for separating carbon dioxide in a plant as described above, wherein the method comprises: - Contacting an inlet stream containing carbon dioxide with an aqueous ammonia solution in the absorber, - Contacting a first gaseous stream obtained from the absorber with wash water to remove ammonia from the first gaseous stream in the gas scrubber, - Expulsion of gaseous carbon dioxide and gaseous ammonia from the wash water in one stripper and generation of a second gaseous outflow, - Circulating the wash water in a loop through the first reboiler, which is coupled to the stripper in the loop, whereby heat energy is introduced into the wash water in the first reboiler, - Introducing the second gaseous outflow from the stripper through a connecting line from the stripper to the absorber, - Introducing a first liquid outflow obtained from the absorber into the regenerator, in which gaseous carbon dioxide is driven off from the first liquid outflow, - Circulating the first liquid outflow in a circuit through the second reboiler, which is coupled to the regenerator in the circuit, whereby thermal energy is introduced into the first liquid outflow in the second reboiler, - Extraction of a third gaseous outflow containing gaseous carbon dioxide from the regenerator through the gas outlet, - Transfer of heat energy from the second gaseous outlet and / or (preferably “and”) from the third gaseous outlet in the first heat exchanger to the refrigerant at a first pressure and a first temperature of the refrigerant, - Transferring thermal energy from the carbon dioxide-containing input stream and / or (preferably “and”) from at least one chiller of the system in the second heat exchanger to the refrigerant at a second pressure and a second temperature of the refrigerant, wherein the second pressure is lower than the first pressure and the second temperature is lower than the first temperature, - Transfer of heat energy in the third heat exchanger from the refrigerant to the wash water and / or (preferably “and”) the first liquid outflow.

[0028] Any equipment as described above can be used in this process. The process features and conditions described above can be applied in this process. Specific embodiments of the process are listed below, and their advantages have already been explained.

[0029] In one embodiment of the method, the first temperature is in the range of 60 to 90°C and the second temperature is in the range of 10 to 40°C. An example of the first and second pressures for ammonia was mentioned previously.

[0030] In one embodiment of the method, the method has: - Transferring heat energy from the system to the refrigerant in the fourth heat exchanger at a third pressure and a third temperature of the refrigerant, where the third pressure is lower than the second pressure and the third temperature is lower than the second temperature.

[0031] In one embodiment of the method, the heat energy transferred from the system to the refrigerant in the fourth heat exchanger originates from one or more of the following: - the input stream, which has preferably already been cooled by the second heat exchanger, - the second gaseous outflow, which has preferably already been cooled by the first heat exchanger, - the wash water, - aqueous ammonia solution, which is taken from the absorber and recirculated into the absorber, and / or - the third gaseous outflow, which has preferably already been cooled by the first heat exchanger.

[0032] In one embodiment of the method, the third temperature is in the range of 0 to 10°C. An example of the third pressure for ammonia was mentioned earlier.

[0033] In one embodiment of the method, the heat energy transferred to the refrigerant in the first, second and fourth heat exchangers is greater than the energy transferred from the refrigerant to the wash water and / or (preferably “and”) the first liquid outflow in the third heat exchanger.

[0034] Further embodiments relating to the system and the process are specified below: In one embodiment, the refrigerant circuit is designed such that a first portion of the refrigerant flow circulates through the first evaporator, wherein the first portion amounts to 45 to 95 wt.%, preferably 45 to 80 wt.%, of the refrigerant flow.

[0035] In one embodiment, the refrigerant is selected from the group consisting of 1-butene, acetone, ammonia, benzene, cis-2-butene, cyclohexane, cyclopentane, cyclopropane, D4, D5, D6, dichloroethane, diethyl ether, dimethyl carbonate, dimethyl ether, ethanol, ethylbenzene, ethylene oxide, heavy water, isobutane, isobutene, isohexane, isopentane, m-xylene, MD2M, MD3M, MD4M, MDM, methanol, MM, n-butane, n-decane, n-dodecane, n-heptane, n-hexane, n-nonane, n-octane, n-undecane, neopentane, o-xylene, p-xylene, propyne, R11, R113, R114, R123, R1233zd(E), R1234ze(Z), R124, R13I1, R141b, R142b, R21, R236ea, R236fa, R245ca, R245fa, R365mfc, R40, sulfur dioxide, toluene, trans-2-butene, R1336mzz(Z), R1224yd(Z), cyclobutene, water, mixture of methanol and ammonia, mixture of cis-2-butene and methanol, mixture of benzene and methanol, mixture of cyclobutene and toluene, mixture of cyclobutene and heptane, or the refrigerant contains a component from the group.

[0036] Ammonia is a preferred refrigerant.

[0037] In one embodiment, the refrigerant is ammonia and the refrigerant circuit is designed such that a first portion of the refrigerant flow circulates through the first evaporator, wherein the first portion is 60 to 75 wt.%, preferably 65 to 75 wt.%, of the refrigerant flow.

[0038] In one embodiment, the heat pump has, in addition to a first refrigerant circuit, a second refrigerant circuit. The refrigerant in the first refrigerant circuit is preferably ammonia, and the refrigerant in the second refrigerant circuit is preferably water. The first refrigerant circuit preferably passes through the first evaporator, the second evaporator, and, if present, the third evaporator, as well as the condenser. The second refrigerant circuit preferably passes through the condenser, in which heat is transferred from the first refrigerant circuit to the second refrigerant circuit (where the condenser is considered an evaporator from the perspective of the second refrigerant circuit), and the first reboiler and / or the second reboiler. In this case, the condenser is connected to the first reboiler and / or the second reboiler.The condenser is then a third heat exchanger connected to the first reboiler and / or the second reboiler.

[0039] The invention is described below with reference to exemplary embodiments. The figures shown are: Fig. 1: a plant for the separation of carbon dioxide and a flow diagram of a process for carbon separation according to the state of the art; Fig. 2: A chiller as known from the state of the art; Fig. 3: a heat pump, which in combination with a system of Fig. 1 represents a first exemplary embodiment of the invention; Fig. 4 A logarithmic pH curve of a cascaded high-temperature heat pump (HTHP) system based on the reverse Rankine cycle for the in Fig. 3 heat pumps shown; Fig. 5: a heat pump, which in combination with a system of Fig. 1 represents a second exemplary embodiment of the invention; Fig. 6 A logarithmic pH curve of a cascaded high-temperature heat pump (HTHP) system based on the reverse Rankine cycle for the in Fig. 5 heat pumps shown; Fig. 7: a heat pump, which in combination with a system of Fig. 1 represents a third exemplary embodiment of the invention; Fig. 8 A logarithmic pH curve of a cascaded high-temperature heat pump (HTHP) system based on the reverse Rankine cycle for the in Fig. 7 heat pump shown; Fig. 9 a process sequence according to the invention.

[0040] Fig. Figure 1 shows a plant (400) for the capture of carbon dioxide and a flow diagram of a carbon capture process. The in Fig. The system shown largely corresponds to the state of the art. In combination with a heat pump according to one of the Fig. The invention is implemented in 3-8. It is shown in Fig. 1:

[0041] Flue Gas Cooling Section: In the direct contact cooler 410, flue gas, as the inlet stream ES, comes into contact with the cold water 411 from the cooling tower 409 of the direct contact cooler 410. The direct contact cooler 410 ensures that the flue gas / inlet stream ES is cooled to a lower temperature and the moisture it contains condenses. After contact with the flue gases / inlet stream ES, the heated water 411 is pumped into the cooling tower 409 of the direct contact cooler 410, which performs evaporative cooling to lower the water temperature before it is returned as chilled water 413 via the second direct contact cooler 412 to the direct contact cooler 411. The flue gas is further cooled by chilled water through a chiller 415 after being conveyed by a blower 414. The temperature of the chilled water (approx. 2-10 °C) is maintained by an external chiller, as shown in [reference missing]. Fig. 2 (e.g., by an ethyl glycol-based heat pump (Gaspar, Jozsef; Arshad, Muhammad Waseem; Blaker, Eirik Ask; Langseth, Birger; Hansen, Tord; Thomsen, Kaj et al. (2014): A Low Energy Aqueous Ammonia CO2 Capture Process. In Energy Procedia 63, pp. 614-623. DOI: 10.1016 / j.egypro.2014.11.066)). The additional cooling helps to reduce the volume flow rate of the flue gas / input stream ES entering absorber 401 (by limiting the humidity to preferably below 1%) and thereby increase the CO2 concentration in the flue gas / input stream ES. The entire cooling range contributes to improving the absorption efficiency and thus to reducing the capital costs of the system.

[0042] Fig. 2 shows in detail the in Fig. 1 Chiller 415, 416, 418 (chiller cooler) shown, designed as a refrigeration machine for supplying the aqueous ammonia carbon capture process of the Fig. 1 with cold water. Shown are: A 420 mm cold water supply into the system of Fig. 1, a compressor 421, an evaporator 422, a condenser 423, an expansion valve 424, a chiller cooling tower 425, and water 426, which absorbs heat in the condenser 423. The chillers 417 and 419 of the Fig. 1 are constructed analogously and each has a second cold water inlet, analogous to inlet 420. However, they could also be designed as separate systems, each with its own cold water inlet, like chillers 414, 416, 418. Fig. 1 also shows:

[0043] An absorption section: During CO2 absorption in absorber 401, the temperature of the inlet stream ES is lowered to facilitate the reaction between CO2 and ammonia and the formation of ammonium bicarbonate. This reaction is maintained at temperatures between 5 °C and 15 °C, where the solubility of CO2 in the ammonia solution is greatest. The absorption process can take place in a series of packed columns, with the lean aqueous ammonia solution entering at the top of absorber 401, which is an absorption column, and coming into contact with the rising inlet stream ES. The concentration of the lean ammonia solvent can vary between 6 and 28 wt%, depending on the process conditions. The higher the concentration of the ammonia solvent, the better the absorption capacity, but the more ammonia slip occurs in the inlet stream ES.The lower the concentration of the ammonia solvent, the greater the heat energy requirement for regeneration. The optimal concentration of the ammonia solvent must be investigated on a case-by-case basis. In one such study, for example, an optimal solvent concentration of approximately 12.5 wt% was determined (Hanak, Dawid P.; Biliyok, Chechet; Manovic, Vasilije (2015): Rate-based model development, validation and analysis of chilled ammonia process as an alternative CO2 capture technology for coal-fired power plants. In International Journal of Greenhouse Gas Control 34, pp. 52-62. DOI: 10.1016 / j.ijggc.2014.12.013). The overall chemical reactions can be summarized as follows: Absorption reaction: CO2(g)+NH3(aq)+H2O(l)⇌ NH4HCO3(aq)

[0044] Operating at lower temperatures avoids unwanted side reactions, thereby minimizing ammonia slip into the input stream ES (see below).

[0045] Undesirable reactions: NH4 + + CO3 2- ⇌ NH3(g)+ HCO3 - NH4 + + HCO3 - ⇌ NH3(g)+ CO2(g)

[0046] The transition from a solids-forming to a solids-free operation involves a certain degree of complexity which, if not avoided, can lead to clogging of absorber 401 and complicate the operation of plant 400. Although energy consumption can be optimized, the need for cooling to maintain low temperatures increases operating costs.

[0047] Water scrubbing and ammonia stripper section: The treated inlet stream ES is passed as the first gaseous outflow AS1 through a further packing bed of the gas scrubber (also referred to as the water scrubber) 402, where wash water WW removes the ammonia vapor that may have escaped from the absorber 401. A portion of the wash water WW is recirculated and cooled to a low temperature in the chiller 418. The majority of the wash water WW is directed to the stripper 403, a bulk container that can be operated at a pressure above atmospheric pressure and serves to remove ammonia from the wash water WW. The heat for the stripper 403 is supplied by condensing steam 427 in the reboiler 20, which strips the ammonia or CO2 contained in the wash water WW. The stripped vapors are cooled and, as a second gaseous outflow AS2, are directed through the connecting line 405 to the bottom of the absorber 401.Similarly, a fresh supply of treated water 428 from the lower stream of the stripper 403 is maintained to the upper part of the gas scrubber 402. The treated flue gases 429 from the upper part of the gas scrubber 402 are directed into the second direct contact cooler 412, where they come into contact with the cooling water recirculated from the cooling tower 409 of the direct contact cooler. The final treatment of the flue gases described above ensures that the ammonia concentration is reduced to trace levels before being released into the atmosphere (Electric Power Research Institute (2011): Chilled Ammonia Process Development Unit at We Energies Pleasant Prairie Power Plant. Process Performance. 2011 Technical Report. Palo Alto (1017642)).

[0048] Regeneration section: The enriched solution exiting the bottom of absorber 401 is a first liquid outflow FL1 and is pumped to a higher pressure (typically above 20 bar) by pump 430. It is then heated in a crossover heat exchanger 431 by the lean solution 432 exiting the bottom of regenerator 406 (regeneration column). The enriched solution enters the regenerator 406 at a higher pressure, and the bound CO2 is released in a reboiler 21 by the provision of thermal energy. The pressure of the stream required for regeneration can be between 5 and 8 bar, depending on the boiling point of the pressurized enriched solution. aThe regenerator 406 operates at a higher pressure because the solubility of ammonia in the solution is higher, thus reducing emissions of gaseous ammonia (EP 1781400 A1). The lean solution 433 exits at high temperature at the bottom of the regenerator 406 and is returned to the cycle.

[0049] Regeneration response: NH4HCO3(aq)+Heat⇌ CO2(g)+NH3(aq)+H2O(l)

[0050] The stripped steam leaves the regenerator 406 as a third gaseous stream AS3 through the gas outlet 408 and contains traces of ammonia and water, which are passed through a water scrubber, designed as a separator 434, to improve the CO2 concentration. The separated presaturated carbon dioxide 435 is further cooled to remove traces of water vapor, enabling its recovery and reuse in downstream systems (Augustsson et al. 2017).

[0051] Thermal energy is required for the ammonia stripper 403 and the regeneration section of the entire carbon capture plant. Since one or both of these units operate at higher pressure, steam 427, 436 (5-8 bar) is typically used. a ) as an energy source in the reboilers 20, 21. This steam 427, 436 must be supplied either from the steam network of the upstream plant or from the additional steam generation plant. The cooling requirement in the respective carbon capture plant is quite high, as the temperature of the flue gas / inlet stream ES, the absorber 401, the wash water WW and other streams must be cooled. The low-temperature cooling is supported by chillers 415, 416, 417, 418, 419. The chiller unit of the chillers 415, 416, 417, 418, 419 itself consists of various components, as shown in Fig. 2 shown. The refrigeration unit is operated with electrical energy, which is supplied to the compressor 421 of the Fig. 2 is supplied, and releases the heat via its own cooling tower 425 (see below). Fig. 2), to the environment, while at the same time a low temperature is maintained on the side of the evaporator 420 (see below). Fig. 2) is maintained.

[0052] The system and components described so far are largely known from the state of the art.

[0053] For cooling, several chillers 415, 416, 417, 418, 419 are used, of which chillers 415, 416, 418 are in Fig. 2 are shown in more detail. The low-temperature waste heat removed by the chiller of a chiller 415, 416, 417, 418, 419 (due to exothermic reactions in the absorber 401, in the gas scrubber 402, etc.) often remains unused and is released into the environment via the chiller's cooling tower 425 (see Fig. 2) The waste heat dissipated by the chillers can also be of high quality, e.g., for cooling the CO2 stream after regeneration, which can then be used more effectively. Similarly, the waste heat dissipated by water in direct contact coolers 410, 412 is released to the environment via the cooling tower 409 (see Fig. 1).

[0054] Similarly, the demand for thermal energy is quite high for both solvent regeneration (for CO2 removal) in regenerator 401 and ammonia stripping in stripper 403. Furthermore, both columns operate at higher pressures, resulting in higher temperatures in the evaporators than in conventional amine-based systems. Thermal energy is traditionally supplied using fossil fuels. The heating energy is generally condensing low / medium-pressure steam drawn from an upstream network (most likely from the low-pressure stages of the steam turbine or from the heat recovery section), resulting in a total energy loss of approximately 4.1–7% (EP 1781400 A1).

[0055] The present invention utilizes the waste heat generated in the system in an energy-efficient manner to cover the heating and cooling energy demand by employing a heat pump system, as described in the Fig. 3-8 described, which is connected with Annex 400 of the Fig. 1 is combined to form a system according to the invention. The aim of the invention is the complete electrification of the supply system and at the same time ensuring that the system is free from external heat energy requirements. The prior art is based on external steam requirements to cover the heat demand of the chillers 20, 21, and on refrigeration machines according to Fig. 2 to cover the cooling demand and to rely on cold water to cover the additional cooling demand for direct contact coolers.

[0056] The present invention aims to cover energy needs as completely as possible. It goes beyond the concept of a heat pump, which replaces the function of a refrigeration unit in an integrated system. This particular approach to a heat pump based on a vapor compression refrigeration cycle, which extracts heat from different temperature levels, has not been presented before.

[0057] Due to the large temperature difference (difference between the minimum temperature of the source and the maximum temperature of the sink), a cascade system is used in some parts of the invention, i.e., two different refrigeration circuits exchange heat with each other. This can fundamentally worsen the coefficient of performance (COP) of the heat pump. However, the invention carefully examines the correct temperature levels for heat extraction in order to obtain a relatively high COP, which has a positive effect on electrification.

[0058] The existing system according to the prior art relies on an external supply of heat energy, whereas the invention presented here generates the heat energy within the system. The investigation revealed that the system has a much higher heat energy output to the environment at lower temperatures. The described invention not only enhances the low-temperature heat but, in one embodiment, when utilizing all available energy, generates excess hot heat energy at the same temperature level required by the system. This excess heat energy can be used outside the system, i.e., likely downstream, for example, for conditioning captured CO2 or for converting CO2 into useful chemicals (CCU), etc.

[0059] The invention is divided into a series of possible process configurations that take into account the different requirements of the carbon capture plant. A detailed description and the advantages are illustrated below.

[0060] Fig. Figure 3 shows the heat pump 501 for combination with a system 400 to realize a first exemplary embodiment of the invention. The heat pump is based on a cascade system that covers the heat energy demand of the stripper 403 and regenerator 406.

[0061] The components are described as follows - Components 1, 12, 9, 7, 10 and 13 are designed as heat exchangers, with 1 and 9 being evaporators. - Components 2, 4, 6, 15, 17 and 19 are designed as compressors. - Components 8, 11 and 14 are expansion valves or expanders. - Components 3, 5, 16 and 18 can be referred to as mixing containers or simply as vessels. Components 20 and 21 are reboilers. These reboilers are in Fig. 1 shown as part of the process diagram.

[0062] The 501 heat pump Fig. With regard to the direction of circulation of the first refrigerant circuit KKL1, the first refrigerant circuit KKL1 has a first branch VZ1 after the condenser 7, leading to a first circuit subsection TA1 and a second circuit subsection TA2. Before the condenser 7, the first refrigerant circuit KKL1 has a first junction VE1 of the first circuit subsection TA1 and the second circuit subsection TA2.

[0063] The first evaporator 9 is arranged in the first circuit section TA1 and the second evaporator 1 is arranged in the second circuit section TA2.

[0064] With regard to the direction of circulation, the first expansion valve 8 is located upstream of the first evaporator 9 and the first compressor 6 is located downstream of the first evaporator 9.

[0065] Furthermore, with regard to the direction of circulation, the second expansion valve 14 is arranged in the second circuit section TA2 and before the second evaporator 1, and the second compressor 2 is arranged in the second circuit section TA2 and after the second evaporator 1.

[0066] Fig. Figure 3 shows a heat pump 501 configured as a cascaded high-temperature heat pump system for an aqueous ammonia carbon capture unit (AACCU) 400. The refrigerant is also referred to as the working fluid. The lower cycle of the multi-stage vapor compression heat pump can be equipped with Fig. Figure 4 illustrates this. It begins at current 100 and ends at current 117. Similarly, the upper cycle, which begins at point 202 and ends at 201, can be described. Identical reference numerals denote identical features. The first exemplary embodiment of the invention described here extracts only the heat required to meet the thermal energy demand of the reboilers 20, 21 using a cascaded heat pump system. Unlike a subsequent embodiment, the first exemplary embodiment deals with Fig. 5 not with the replacement of one or more of the chillers 415, 416, 417, 418, 419 to provide cooling.

[0067] Component 1, which is an evaporator 1, is intended as a replacement for the cooling tower 409 of the direct contact cooler 410, as shown in Fig. As described in section 1, the evaporator 1 transfers heat energy from the carbon dioxide-containing input stream (ES) to the working fluid.

[0068] Component 1 can also dissipate waste heat through cooling tower 425 of the in Fig. The refrigeration unit shown in section 2, one or more of the chillers 415, 416, 418, are used. Heat energy is then transferred through the evaporator 1 from a cooling tower 425 located in Fig. Component 1 transfers the heat from the chiller's refrigeration unit shown in Figure 2 to the working fluid. Alternatively or additionally, Component 1 can dissipate the waste heat through the cooling tower of one or more of the chillers 417, 419. Component 1 is thus an additional replacement for at least two components in the prior art: the cooling tower 409 of the direct contact cooler 410 and at least one cooling tower 425 of a chiller, preferably the cooling towers of several or all chillers 415, 416, 417, 418, 419.

[0069] This low-temperature waste heat (Q2) is absorbed by the working fluid of the heat pump system at a constant temperature (which can be in the range of atmospheric temperature from 10-40 °C) and thus evaporates from state 117 to 100.

[0070] Component 2, which is a compressor 2, compresses the working fluid vapor to a higher pressure and temperature and mixes with a portion of the working fluid in component 3, which is a mixing vessel. Component 3, the mixing vessel, ensures that the working fluid remains in a vapor state before it enters the next compression stage. The portion of working fluid that separates from component 112, i.e., stream 113, passes through component 12, which is a heat exchanger, to be heated to stream 114 before mixing with stream 101 in component 3. The main purpose of component 12 is to dissipate heat (Q4) from component 10, which is a heat exchanger, through recuperation, as indicated by stream 302. Components 10 and 12 can also consist of a single component instead of two separate ones.Component 4, a compressor, re-compresses the steam to a higher pressure and temperature, undergoing the same mixing process within component 5, which is a mixing vessel. The working fluid separated at this pressure level of 107, i.e., stream 108, is responsible for heat removal (Q4) at a constant temperature (which can be in the range of 60–90 °C) at two possible locations in the AACCU. These locations are referred to as strip steam after regeneration in regenerator 406 (this is the third gaseous outflow AS3 in ). Fig. 1) and steam after the ammonia stripper 403 (this is the second gaseous outflow AS2 in Fig. 1), described in the AACCU, which are generally cooled by chilled water and can be partially replaced by component 9.

[0071] The attractive feature lies in the ability to dissipate large quantities of heat at the highest temperature level, which improves the overall coefficient of performance (COP) of the heat pump system. The working fluid follows the same path: flow 109 mixes with flow 103 in component 5 before continuing as flow 104. A further compression step takes place in component 6, which is a compressor, and the heat is dissipated via component 7, which is a condenser, at the highest temperature (which can range from 80 to 120 °C) and highest pressure level of the second refrigerant circuit, KKL2. The working fluid is cooled to level 106 and then expanded in component 8, an expansion valve, to the lower pressure level of flow 107. Flow 107 is then split into flows 108 and 110.Stream 110 is cooled to stream 111 by recuperation (heat stream 302 is dissipated by component 12) before being further expanded in component 11, an expansion valve, to lower the pressure level of stream 112. Stream 112 is then split into streams 113 and 115. Stream 115 is cooled by recuperation (heat stream 301 is dissipated by component 1). Finally, stream 116 is expanded by component 14, an expansion valve, to the lowest pressure and temperature level in the cycle, i.e., to stream 117.

[0072] Fig. Figure 4 is a logarithmic pressure-enthalpy curve of a cascaded high-temperature heat pump (HTHP) system based on the reverse Rankine cycle for the in Fig. 3 Heat pump 501 shown for a first exemplary embodiment of the invention.

[0073] The recovered heat Q5 is removed from the working fluid of the second refrigerant circuit KKL2 via component 7, which is a condenser 7, causing it to evaporate from stream 201 to 202. Stream 202 is fed to component 15, which is a compressor, and increases the pressure level of the working fluid to stream 203. Component 16, a mixing vessel, acts as the component where the freshly supplied working fluid, as a pressurized liquid stream 204, mixes with stream 203 and is converted into vapor before component 17, which is a compressor. Component 17 recompresses the vapor to a higher pressure level, and the same mixing process as described above takes place. The final compression step is performed by component 19, a compressor, to generate a high pressure and high temperature of the working fluid (which can be in the range of 150–200 °C).Stream 209 is distributed according to the energy demand (Q6) of the reboilers 20 and 21 in both the regenerator and the ammonia stripper of the AACCU, thus replacing the conventional steam supply with steam 427 and 436 from external sources. Stream 200 collects the condensate of the working fluid from streams 212 and 213 before it is expanded via component 22, an expansion valve, to the lowest pressure level in the second refrigerant circuit KKL2.

[0074] The 502 heat pump can use a combination of different working fluids in both the first refrigerant circuit KKL1 and the second refrigerant circuit KKL2 while operating according to the described concept. An example of the first exemplary embodiment shown: If pure ammonia is assumed to be the working fluid for the first refrigerant circuit KKL1 and water as the working fluid for the second refrigerant circuit KKL2, then the COP (Coefficient of Performance) for the heating of the high-temperature heat pump system can be in the range of 1.5–2.5. This COP only considers heating as a positive effect; if cooling is also considered as a positive effect, it will necessarily be much higher.

[0075] The second exemplary embodiment of the invention is shown schematically in the Fig. Figure 5 shows the components described in the previous first embodiment, except that additional components are described here. - Components 23 and 25 form a heat exchanger. - Component 26 is a compressor. Component 24 is an expansion valve. Component 27 can be described as a mixer, mixing vessel, or simply a vessel. - Component 28 is an additional heat consumer for excess energy.

[0076] The 502 heat pump of the Fig. 5 operates with a cascade system that covers the entire heat energy demand of plant 400.

[0077] The 502 heat pump Fig. 5 is in comparison to the heat pump 501 the Fig. 3. The following additional items are available: In the heat pump 502, in the direction of circulation of the first refrigerant circuit KKL1, the refrigerant circuit has a second branch VZ2 from the second circuit section TA2 to a third circuit section TA3 after the first branch VZ1.

[0078] The refrigerant circuit KKL1 has the second junction VE2 before the condenser 7 and before the first junction VE1, where the third circuit section TA3 and the second circuit section TA2 are joined.

[0079] The third evaporator 25 is located in the third circuit section TA3, and the third expansion valve 24 is located upstream of the third evaporator 25 with respect to the direction of circulation. The third compressor 26 is located downstream of the third evaporator 25 with respect to the direction of circulation.

[0080] The cascaded cycles are in Fig. Figure 5. This embodiment aims to cover the entire cooling and heating requirements of the aqueous ammonia-carbon capture plant 400 (AACCU). The additional part of the first refrigerant circuit KKL1, which differs from the embodiment in Fig. The key difference is the splitting of stream 117 into stream 119 and stream 118. The recuperation cooling requirement (stream 300) for streams 118 to 120 is covered by component 25. Stream 120 is then de-expanded to stream 121 using component 24. Stream 121 absorbs heat (Q4) at a constant temperature level (which can be in the temperature range of -5 to 20 °C) from component 25 and simultaneously evaporates to stream 122. Component 25 can replace chillers 415, 416, 417, 418, and 419 in the modern AACCU system. The cycle continues with a compression step by component 26 before further components 27 are added. Another noteworthy difference to the heat pump 501 is that component 1 does not have access to the waste heat of the cooling tower 425 of a chiller 415, 416, 417, 418, 419, since there are no chillers 415, 416, 417, 418, 419 in invention 2.Component 1 thus has access to the waste heat from cooling tower 409 or another part of the AACCU, if required. The rest of the first refrigerant circuit KKL1 remains unchanged.

[0081] The second refrigerant circuit KKL2 is largely identical to that in Fig. 3, but differs in terms of the amount of recovered heat (Q6), which can range between 150 and 200 °C. The amount of waste heat available in the AACCU exceeds the requirements of the evaporators and generates additional thermal energy. This thermal energy can, as in Fig. The components shown in Figure 6 can be used for various purposes deemed necessary outside of the AACCU, as illustrated by Component 28. An important application could be downstream CO2 purification or utilization, since all further processes are energy-intensive.

[0082] Fig. Figure 6 shows the logarithmic PH curve of a cascaded high-temperature heat pump (HTHP) system based on the reverse Rankine cycle for the 502 heat pump. Fig. 5.

[0083] The 502 heat pump can use a combination of different working fluids in both the first refrigerant circuit (KKL1) and the second refrigerant circuit (KKL2), just like the 501 heat pump. If pure ammonia is used as the working fluid for the first refrigerant circuit (KKL1) and water as the working fluid for the second refrigerant circuit (KKL2), then the COP for heating in the HTHP system can be in the range of 2 to 3. This COP only considers heating as a positive effect; if cooling is also considered a positive effect, then it will be much higher.

[0084] Fig. Figure 7 shows the heat pump 503 for combination with a system 400 to implement a third exemplary embodiment of the invention. The description of the components is the same as described in the preceding figures. The basic variant is assumed to operate at the end of the operating pressure range of the regenerator 406 and the stripper 403 and is therefore referred to as the modified AACCU. If the regenerator 406 and stripper 403 are operated at a lower pressure, the thermal energy requirement increases. Operation at a lower pressure also carries the risk of greater ammonia slip in the pure CO2 stream. This effect can be counteracted by using a lower weight fraction of aqueous ammonia as a solvent. However, this inevitably leads to a higher thermal energy requirement for regeneration.The advantage of operating at a lower stripper / regenerator pressure (which can be atmospheric or below atmospheric pressure) is that the required temperature level at the reboiler 20, 21 is lower (can be in the range of 80-110 °C) than with modern AACCU (can be in the range of 150-200 °C). This offers advantages when integrating heat pumps, as the temperature difference is reduced, which automatically improves the system's coefficient of performance (COP).

[0085] The in Fig. The heat pump 503 shown in Figure 7 is designed to cover the entire heat energy demand of a modified AACCU in a closed system, thereby replacing chillers 415, 416, 417, 418, 419 including the chiller, DCC cooling tower 409, and external steam supply with steam 427, 436. Condensers 70, 71 are integrated into reboilers 20 and 21, respectively. The final heat output (Q5) not only covers the heat energy demand of reboilers 20, 21, but also provides excess energy that, as described in component 28, can be used outside the system.

[0086] The in Fig. The embodiment of the heat pump 503 shown in Figure 7 covers the entire heat energy demand of the modified AACCU when integrated into the system 400.

[0087] Fig. Figure 8 shows the logarithmic PH curve of a cascaded high-temperature heat pump (HTHP) system based on the reverse Rankine cycle for the 503 heat pump. Fig. 7.

[0088] The embodiment of the heat pump 503 Fig. In contrast to the preceding embodiments of the Fig. 3 and Fig. 5. The advantage of operating in a single KKL1 circuit: If pure ammonia is assumed as the working medium for the circuit, the COP of the heating system for the HTHP system can be in the range of 2 to 3. This COP only considers the heating as a positive effect; if cooling is also considered a positive effect, it will inevitably be much higher.

[0089] The following are examples of temperature ranges: It should be noted that the temperature of the working fluid does not change, as it is in the two-phase range. The system is designed to operate in this way (reverse Rankine cycle). - Component 9 Inlet: 60-90 °C Output: 60-90 °C - Component 1 Inlet: 10-40 °C Output: 10-40 °C - Component 25 Inlet: 0-10 °C Output: 0-10 °C - Component 20 / 21 / 28 Inlet temperature: 150-200 °C Output: 150-200 °C

[0090] In Fig. Figure 9 illustrates a process sequence according to the invention. Parts and features thereof have already been described previously. In continuous operation, the activities mentioned may or will take place partially or entirely simultaneously and / or in a different sequence. The sequence or numbering of the activities mentioned therefore does not represent a mandatory chronological order and may be modified where technically feasible, or activities may be carried out in parallel where possible and practical. S1 Contacting a carbon dioxide-containing input stream ES with an aqueous ammonia solution in the absorber 401. S2 Contacting a first gaseous outflow AS1 obtained from the absorber 401 with wash water WW to remove ammonia from the first gaseous outflow AS1 in the gas scrubber 402. S3 Expulsion of gaseous carbon dioxide and gaseous ammonia from the wash water in one stripper 403 and generation of a second gaseous outflow AS2. S4 Circulating the wash water WW in a circuit through the first reboiler 20, which is coupled to the stripper 403 in the circuit, whereby heat energy is introduced into the wash water in the first reboiler 20. S5 Introduction of the second gaseous outflow AS2 from the stripper 403 through a connecting line 405 from the stripper 403 to the absorber 401. S6 Introducing a first liquid outflow FL1 obtained from the absorber 401 into the regenerator 406, in which gaseous carbon dioxide is driven out of the first liquid outflow FL1. S7 Circulating the first liquid outflow FL1 in a cycle through the second reboiler 21, which is coupled to the regenerator 406 in the cycle, whereby heat energy is introduced into the first liquid outflow FL1 in the second reboiler 21. S8 Extraction of a third gaseous outflow AS3, containing gaseous carbon dioxide, from the regenerator 406 through the gas outlet 408. S9 Transfer of heat energy from the second gaseous outflow AS2 and / or from the third gaseous outflow AS3 in the first heat exchanger to the refrigerant at a first pressure and a first temperature of the refrigerant. S10 Transfer of heat energy from the carbon dioxide-containing input stream ES and / or from at least one chiller of the system in the second heat exchanger to the refrigerant at a second pressure and a second temperature of the refrigerant, wherein the second pressure is lower than the first pressure and the second temperature is lower than the first temperature S11 Transfer of heat energy in the third heat exchanger from the refrigerant to the wash water WW and / or the first liquid outflow FL1. S12 Transfer of heat energy from the system 400 to the refrigerant in the fourth heat exchanger at a third pressure and a third temperature of the refrigerant, wherein the third pressure is lower than the second pressure and the third temperature is lower than the second temperature.

[0091] Examples of commercial applications of the present invention include: - Carbon deposition from various point sources - Development of high-temperature heat pumps - Value chain for carbon capture, utilization, transport and storage. - Fertilizer production.

Claims

A system (400) for the separation of carbon dioxide, comprising: - an absorber (401) in which an inlet stream (ES) containing carbon dioxide can be contacted with an aqueous ammonia solution; - a gas scrubber (402) in which a first gaseous outflow (AS1) obtained from the absorber (401) can be contacted with wash water (WW) for the removal of ammonia from the first gaseous outflow (AS1); - a stripper (403) in which gaseous carbon dioxide and gaseous ammonia can be driven off from the wash water (WW) in a second gaseous outflow (AS2); - a first reboiler (20) coupled to the stripper (403) in a circuit, wherein the wash water (WW) can be circulated through the first reboiler (20) in the circuit to introduce thermal energy into the wash water (WW); - a connecting line (405) from the stripper (403) to the absorber (401),through which the second gaseous outflow (AS2) from the stripper (403) can be introduced into the absorber (401), - a regenerator (406) into which a first liquid outflow (FL1) obtained from the absorber (401) can be introduced and in which gaseous carbon dioxide can be driven off from the first liquid outflow (FL1), - a second reboiler (21) which is coupled to the regenerator (406) in a circuit, wherein the first liquid outflow (FL1) can be circulated in the circuit through the first reboiler (20) in order to introduce thermal energy into the first liquid outflow (FL1), - a gas outlet (408) through which a third gaseous outflow (AS3) containing the gaseous carbon dioxide can be extracted from the regenerator (406), - a heat pump (501; 502, 503) comprising a Refrigerant and at least one refrigerant circuit (KKL1, KKL2) designed in such a way that a refrigerant flow circulates within it,wherein the refrigerant circuit comprises: • a condenser (7; 70, 71), • a first expansion valve (8) and a second expansion valve (14), • a first evaporator (9) and a second evaporator (1), • a first compressor (6) and a second compressor (2), wherein, with respect to a direction of circulation of the refrigerant circuit (KKL1), the refrigerant circuit after the condenser (7; 70, 71) has a first branch (VZ1) to a first circuit subsection (TA1) and a second circuit subsection (TA2), and the refrigerant circuit (KKL) before the condenser (7; 70, 71) has a first union (VE1) of the first circuit subsection (TA1) and the second circuit subsection (TA2), wherein the first evaporator (9) is arranged in the first circuit subsection (TA1) and the second evaporator (1) in the second circuit subsection (TA2) is arranged, wherein, with respect to the direction of rotation,the first expansion valve (8) is arranged upstream of the first evaporator (9), wherein, with respect to the direction of circulation, the first compressor (6) is arranged downstream of the first evaporator (9), wherein, with respect to the direction of circulation, the second expansion valve (14) is arranged in the second circuit section (TA2) and upstream of the second evaporator (1), and, with respect to the direction of circulation, the second compressor (2) is arranged in the second circuit section (TA2) and downstream of the second evaporator (1), wherein the first evaporator (9) is a first heat exchanger or is connected to a first heat exchanger, wherein the first heat exchanger is configured to transfer thermal energy from the second gaseous outlet (AS2) and / or from the third gaseous outlet (AS3) to the refrigerant at a first pressure and a first temperature of the refrigerant, wherein the second evaporator (1) is a second heat exchanger or is connected to a second heat exchanger.wherein the second heat exchanger is configured to transfer thermal energy from the inlet stream (ES) and / or from at least one chiller of the system to the refrigerant at a second pressure and temperature of the refrigerant, wherein the second pressure is lower than the first pressure and the second temperature is lower than the first temperature, wherein the condenser (7; 70, 71) is a third heat exchanger connected to or integrally formed with the first reboiler (20) and / or the second reboiler (21), which is configured to transfer thermal energy from the refrigerant to the wash water (WW) and / or the first liquid outlet (FL1). System (400) according to claim 1, wherein the first temperature is in the range of 60 to 90°C and the second temperature is in the range of 10 to 40°C. System (400) according to one of the preceding claims, wherein the heat pump (502) comprises: • a third expansion valve (24) • a third evaporator (25) • a third compressor (26) wherein, with respect to a circulation direction of the refrigerant circuit (KKL1), the refrigerant circuit after the first branch (VZ1) has a second branch (VZ2) from the second circuit section (TA2) to a third circuit section (TA3) and the refrigerant circuit (KKL1) before the condenser (7) and before the first junction (VE1) has a second junction (VE2) in which the third circuit section (TA3) and the second circuit section (TA2) are joined, wherein the third evaporator (25) is arranged in the third circuit section (TA3), wherein, with respect to the circulation direction, the third expansion valve (24) is arranged before the third evaporator (25), wherein, in With regard to the direction of rotation,the third compressor (26) is arranged downstream of the third evaporator (25), wherein the third evaporator (25) is at least a fourth heat exchanger or is connected to at least a fourth heat exchanger, wherein the at least one fourth heat exchanger is configured to transfer thermal energy from the system (400) to the refrigerant at a third pressure and a third temperature of the refrigerant, wherein the third pressure is lower than the second pressure and the third temperature is lower than the second temperature. System (400) according to claim 3, wherein the heat energy transferred from the fourth heat exchanger of the system (400) to the refrigerant originates from one or more of the following: - the inlet stream (ES), preferably already cooled by the second heat exchanger, - the second gaseous outlet (AS2), preferably already cooled by the first heat exchanger, - the wash water (WW), - aqueous ammonia solution taken from the absorber (401) and recirculated into the absorber (401), and / or - the third gaseous outlet (AS3), preferably already cooled by the first heat exchanger. System (400) according to one of claims 3 or 4 wherein the third temperature is in the range of 0 to 10°C. A method for separating carbon dioxide in a system (400) according to any one of claims 1-5, comprising: - contacting (S1) a carbon dioxide-containing inlet stream (ES) with an aqueous ammonia solution in the absorber (401), - contacting (S2) a first gaseous outflow (AS1) obtained from the absorber (401) with wash water (WW) to remove ammonia from the first gaseous outflow (AS1) in the gas scrubber (402), - driving off (S3) gaseous carbon dioxide and gaseous ammonia from the wash water in the first stripper (403) and generating a second gaseous outflow (AS2), - circulating (S4) the wash water (WW) in a circuit through the first reboiler (20), which is coupled to the stripper (403) in the circuit, wherein heat energy is transferred into the first reboiler (20). Wash water is introduced- Introducing (S5) the second gaseous outflow (AS2) from the stripper (403) through a connecting line (405) from the stripper (403) to the absorber (401),- Introducing (S6) a first liquid outflow (FL1) obtained from the absorber (401) into the regenerator (406), in which gaseous carbon dioxide is driven off from the first liquid outflow (FL1),- Circulating (S7) the first liquid outflow (FL1) in a circuit through the second reboiler (21), which is coupled to the regenerator (406) in the circuit, whereby thermal energy is introduced into the first liquid outflow (FL1) in the second reboiler (21),- Extracting (S8) a third gaseous outflow (AS3), which contains the gaseous carbon dioxide, from the regenerator (406) through the gas outlet (408),- Transfer (S9) of thermal energy from the second gaseous outlet (AS2) and / or from the third gaseous outlet (AS3) in the first heat exchanger to the refrigerant at a first pressure and a first temperature of the refrigerant; - Transfer (S10) of thermal energy from the carbon dioxide-containing inlet stream (ES) and / or from at least one chiller of the system in the second heat exchanger to the refrigerant at a second pressure and a second temperature of the refrigerant, wherein the second pressure is lower than the first pressure and the second temperature is lower than the first temperature; - Transfer (S11) of thermal energy in the third heat exchanger from the refrigerant to the wash water (WW) and / or the first liquid outlet (FL1). Method according to claim 6, wherein the first temperature is in the range of 60 to 90°C and the second temperature is in the range of 10 to 40°C. Method according to claim 6 or 7, comprising: - Transferring (S12) heat energy from the system (400) to the refrigerant in the fourth heat exchanger at a third pressure and a third temperature of the refrigerant, wherein the third pressure is lower than the second pressure and the third temperature is lower than the second temperature. Method according to claim 8, wherein the heat energy transferred from the system (400) to the refrigerant in the fourth heat exchanger originates from one or more of the following: - the inlet stream (ES), preferably already cooled by the second heat exchanger, - the second gaseous outlet (AS2), preferably already cooled by the first heat exchanger, - the wash water (WW), - aqueous ammonia solution taken from the absorber (401) and recirculated into the absorber (401), and / or - the third gaseous outlet (AS3), preferably already cooled by the first heat exchanger. Method according to one of claims 8 or 9, wherein the third temperature is in the range of 0 to 10°C. Method according to one of claims 8-10, wherein the heat energy transferred to the refrigerant in the first heat exchanger, the second heat exchanger and the fourth heat exchanger is greater than the heat energy transferred from the refrigerant to the wash water (WW) and / or the first liquid outflow (FL1) in the third heat exchanger and an excess of heat energy is provided which is preferably made available for a downstream process.

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