Plant and process for separating carbon dioxide contained in a fluid stream

Abstract

A system (ANL, ANL2) is proposed for separating carbon dioxide contained in a fluid stream (AG1), exhibiting - an absorber (A) designed to carry out chemical absorption of the carbon dioxide contained in the fluid stream (AG1), - an absorbent, - a regenerator configured to carry out carbon dioxide desorption from carbon dioxide-loaded absorbent, the regenerator comprising a stripper (S) and a reboiler (R), - an absorbent cycle (ACC) designed to supply the carbon dioxide-laden absorbent from the absorber (A) to the regenerator and to supply regenerated absorbent from the regenerator to the absorber (A), - a heat pump (HP), comprising a refrigerant and a refrigerant circuit designed in which a refrigerant flow circulates, which are provided in the refrigerant circuit - a liquefier, - a first expansion valve (EV1) and a second expansion valve (EV2), - a first evaporator (V1) and a second evaporator (V2), - a first compressor (K1) and a second compressor (K2), wherein, with respect to a direction of circulation of the refrigerant circuit (KKL), the refrigerant circuit (KKL) after the condenser has a branch (VZ) to a first circuit subsection (TA1) and a second circuit subsection (TA2). Furthermore, a corresponding procedure is proposed.

Description

[0001] The invention relates to a system for separating carbon dioxide present in a fluid stream. Furthermore, a method for separating carbon dioxide present in a fluid stream is proposed.

[0002] The separation or deposition of gases has been used in industrial applications for over 80 years. Numerous different methods exist for gas separation, including chemical and physical absorption, adsorption (with solid sorbents), membrane separation, and cryogenic separation.

[0003] The capture of carbon dioxide from industrial point sources has recently garnered particular interest due to advancing climate change. For example, in a typical natural gas- or coal-fired power plant, exhaust gases are present at near atmospheric pressure. The carbon dioxide concentration in such an exhaust stream (after combustion in the power plant) fluctuates approximately between 3 and 15 vol%. For such point sources with low carbon dioxide concentrations (corresponding to low partial pressures) and high volume flow rates, chemical absorption is the preferred technology. This is due to the fact that chemical absorption offers high selectivity, higher absorption rates, lower energy consumption, and lower costs compared to other alternatives.

[0004] The industrial reference method of chemical absorption (often using an amine absorbent, also referred to as an amine solvent) is described below. It can be used particularly in power plants and other industrial processes that generate exhaust gases.

[0005] The exhaust gas stream is fed to an absorber (sometimes also referred to as an absorption column, gas scrubber, or wet scrubber), usually by a fan, to overcome an inlet resistance in the absorber. The exhaust gas stream is also usually pre-cooled, e.g. by a cooler, in particular a gas cooler, so that a temperature range of, for example, 40 to 60 °C can be maintained in the absorber. Larger or smaller intervals are also possible. In principle, temperatures or temperature ranges in the absorber can be achieved, e.g. in the interval from 0 to 100 °C. The temperature can be adapted to the absorbent used. The size of the interval range can depend on the design of the absorber. The exhaust gas stream comes into contact with the absorbent in the absorber. Carbon dioxide is removed from the exhaust gas stream and chemically bound to the absorbent.The now largely carbon dioxide-free exhaust stream is typically washed with water in the upper section of the absorber to remove all absorbent residues (especially droplets). The remaining carbon dioxide concentration in the exhaust stream leaving the absorber depends on the design of the capture system used.

[0006] The absorbent, now loaded with carbon dioxide, is pumped into the upper section of a stripper (sometimes also referred to as a regeneration column). The absorbent circulates largely (apart from losses) in an absorbent circuit between the absorber and a regenerator, which contains the stripper and a reboiler (sometimes also referred to as a heater or evaporator).

[0007] A heat exchanger, typically located within the absorber circuit between the absorber and the regenerator, known as an intermediate heat exchanger, provides advantageous heat recovery. It preheats the loaded absorber and cools the regenerated absorber—that is, the low-carbon absorber from which carbon dioxide has been removed in the regenerator.

[0008] To remove the absorbed carbon dioxide from the loaded absorbent, thermal energy is required, often referred to as regeneration energy. The actual pressure required may be only slightly above atmospheric pressure. This thermal energy is provided in the reboiler at elevated temperatures, typically approximately 100 to 140 °C, typically with the help of condensing low-pressure steam, which typically originates from the industrial process (e.g., power generation by a power plant) from whose exhaust stream the carbon dioxide is separated.

[0009] The thermal energy dissolves the carbon dioxide from the loaded absorbent, thus regenerating the absorbent. The now warm, regenerated absorbent is typically pumped through the intermediate heat exchanger again within the absorber circuit and usually further through an additional cooler to keep the temperature range in the absorber into which it is pumped low. Stripped, i.e. separated or separated gases with a high carbon dioxide content (these gases can be referred to as overhead gas) usually leave the stripper in its upper section and are usually cooled to a comparatively lower temperature. Such cooling is primarily carried out to concentrate separated carbon dioxide by condensing and separating water and residues of the absorbent.Cooling is typically provided by cooling water from the industrial process. A condensed distillate, comprising water and the residues of the absorbent, is returned to the stripper as reflux at a lower temperature. The remaining overhead product is the desired carbon dioxide in concentrated form.

[0010] The residues of the absorbent temporarily leave the absorbent circuit as part of the overhead gas, but are returned to it by reflux into the stripper and thus reused in the absorbent circuit.

[0011] In the ideal theoretical case, the absorbent cycle would be thermodynamically and chemically reversible. In practice, however, irreversibilities can occur. This means that the absorbent in the absorbent cycle can be partially converted into chemical byproducts. Such chemical byproducts are typically removed. Refilling the absorbent may be necessary.

[0012] The thermal energy required to separate the carbon dioxide, also for the purpose of regenerating the absorbent, is comparatively high and is typically covered by energy from fossil fuels. Condensing low-pressure steam, taken from an upstream source, is typically used as the heating medium. The upstream source can be, for example, a low-pressure stage of a steam turbine or a heat recovery system. On the other hand, cooling the head gas requires cooling with a refrigerant; cooling water is typically used for this purpose. The thermal energy absorbed by the refrigerant is ultimately lost to the environment, e.g., via cooling towers.

[0013] It is an object of the present invention, with regard to the separation of carbon dioxide present in a fluid stream, wherein the fluid stream can in particular be an exhaust gas stream, to reduce the necessary water consumption, the technical effort for the application of thermal energy and cooling, the additionally occurring carbon dioxide emissions and the resulting costs, e.g. for investments, fuels and / or necessary electricity.

[0014] According to a basic concept of the present invention, a heat requirement of a reboiler for regenerating the absorbent and a cooling requirement for separating carbon dioxide from a head gas stream are generated using an adapted heat pump, which can in particular be a compression heat pump. In particular, phase transformation processes of a refrigerant circulating in a refrigerant circuit can be advantageously utilized within the compression heat pump. A typical temperature difference between a cooler and / or a condenser for separating carbon dioxide from the head gas stream and the reboiler is favorable for the inventive integration of the heat pump.

[0015] The heat requirement of the reboiler, which is usually covered by condensing steam according to the state of the art, is achieved according to the invention by condensing the refrigerant of the heat pump by a condenser or condenser of the heat pump.

[0016] In particular, at least two compressors can be provided within the heat pump. A first compressor can raise the pressure and temperature of the refrigerant to a desired, high range (a comparatively high pressure and a comparatively high temperature) with the aim of partially or completely covering the heat energy demand of the reboiler. This heat energy demand of the reboiler can be used in the design of the heat pump to determine the total mass flow of the refrigerant circulating in the refrigerant circuit (refrigerant flow).

[0017] The refrigerant, which is under a comparatively high pressure, can be throttled to a comparatively medium pressure and / or a comparatively medium temperature by a first expansion valve. The refrigerant flow can then be divided (when viewed in the direction of refrigerant circulation) in the refrigerant circuit, e.g., downstream of the first expansion valve. This means that the refrigerant circuit can branch into at least two circuit sections, a first circuit section and a second circuit section. The branch can correspond to a bifurcation. The two circuit sections can run in parallel.

[0018] For the purposes of this publication, the term "at least" means "equal to or more than." For example, "at least two" means "two or more than two."

[0019] A significant portion of the split refrigerant stream—the first portion of the (split) refrigerant stream flowing in the first circuit subsection—can then (when viewed in the direction of refrigerant circulation) cool a carbon dioxide-containing overhead gas stream originating from a regenerator at the average pressure and average temperature in a first heat exchanger arranged in the first circuit subsection. With respect to the heat pump and the refrigerant, the first heat exchanger is a first evaporator or is connected to a first evaporator. With respect to the overhead gas stream, the first heat exchanger is a first cooler or is connected to a first cooler. The first cooler can be a first condenser, in particular if thermal energy extracted from the overhead gas stream is sufficient for at least partial condensation of the overhead gas stream in the first heat exchanger.

[0020] The remaining part of the split refrigerant flow—the second portion of the (split) refrigerant flow flowing in the second circuit section—can be further throttled to a comparatively low pressure and a comparatively low temperature by a second expansion valve. The second portion of the refrigerant flow can then (when viewed in the direction of refrigerant circulation) cool the carbon dioxide-containing head gas flow at the low pressure and / or low temperature in a second heat exchanger arranged in the second circuit section. The second heat exchanger is, with respect to the heat pump and the refrigerant, a second evaporator or is connected to a second evaporator. With respect to the head gas flow, the second heat exchanger is a second cooler or is connected to a second cooler.The second cooler may be a second condenser, in particular if thermal energy extracted from the head gas stream is sufficient for at least partial condensation of the head gas stream in the second heat exchanger.

[0021] The second portion of the refrigerant flow is brought to medium pressure in a second compressor after the second heat exchanger, as viewed in the direction of refrigerant circulation. Then, as viewed in the direction of refrigerant circulation, the first portion of the refrigerant flow and the second portion of the refrigerant flow can be mixed in a merging unit. The merging of the at least two circuit sections is a physical merging, for example, in the form of a merging of the at least two circuit sections (i.e., their respective lines). The recombined refrigerant flow then reaches the inlet of the first compressor, which increases the pressure to the high pressure and the temperature to the high refrigerant temperature.

[0022] In the prior art, the overhead gas stream is typically cooled with cooling water. Because the overhead gas stream is typically a mixture of carbon dioxide, water vapor, and other gases, the condensation follows a curve in a temperature-enthalpy diagram rather than an isothermal line. This circumstance allows heat to be extracted at different temperatures (here two) or at different pressures (here two). In a system according to the invention, the overhead gas is cooled in two heat exchangers, which extract thermal energy from the overhead gas stream.

[0023] Cooling of the head gas stream can also be carried out, with appropriate adaptation and branching, in more than two circuit sections (for example, three, four, five, or six), at more than two temperatures (for example, three, four, five, or six), or at more than two pressures (for example, three, four, five, or six). Appropriate duplication of the necessary parts and assemblies must then be provided accordingly.

[0024] In particular, it is proposed a plant for separating carbon dioxide in a fluid stream, having - an absorber designed to carry out chemical absorption of the carbon dioxide present in the fluid stream, - an absorbent, - a regenerator designed to carry out carbon dioxide desorption from carbon dioxide-laden absorbent, the regenerator comprising a stripper and a reboiler, - an absorber circuit designed to supply the carbon dioxide-laden absorber from the absorber to the regenerator and to supply regenerated absorber from the regenerator to the absorber, - a heat pump comprising a refrigerant and a refrigerant circuit designed to circulate a refrigerant flow therein, where in the refrigerant circuit are provided - a condenser, - a first expansion valve and a second expansion valve, - a first evaporator and a second evaporator, - a first compressor and a second compressor.

[0025] With respect to the direction of circulation of the refrigerant circuit, the refrigerant circuit downstream of the condenser has a branch to a first circuit section and a second circuit section, and the refrigerant circuit upstream of the condenser has a junction of the first circuit section and the second circuit section. The first evaporator is arranged in the first circuit section, and the second evaporator is arranged in the second circuit section.

[0026] In terms of circulation direction, the first expansion valve is located before the first evaporator and either - before the branch or - arranged after the branching in the first circuit section.

[0027] In terms of circulation direction, the first compressor is located after the first evaporator and either - before joining in the first part of the circuit or - arranged after the unification.

[0028] With respect to the circulation direction, the second expansion valve is arranged in the second circuit section and upstream of the second evaporator. With respect to the circulation direction, the second compressor is arranged in the second circuit section and downstream of the second evaporator.

[0029] 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 thermal energy from a top gas stream discharged from the regenerator to the refrigerant at a first refrigerant pressure. 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 top gas stream to the refrigerant at a second refrigerant pressure, wherein the second pressure is lower than the first pressure. The condenser is a third heat exchanger connected to or integral with the reboiler and configured to transfer thermal energy from the refrigerant to absorbent located in the reboiler.

[0030] Reference is made to the above statements where applicable.

[0031] The designation of individual parts with attributes such as "further," "additional," "further yet again," or numbers (e.g., "first," "second," "third," "fourth," "fifth," "sixth") can serve to distinguish the respective part from other parts of the same type or genus. If the same attribute is used for multiple parts, these parts can have a technical context or a semantic context that can facilitate understanding.

[0032] The fluid stream can be, for example, an exhaust gas stream and / or a synthesis gas stream and / or a natural gas stream containing, among other gases, carbon dioxide. The fluid stream can also contain or comprise such a stream. The fluid stream can be in gaseous form. The carbon dioxide present in the fluid stream is separated by chemical absorption. For this purpose, regenerated absorbent and, if necessary, new absorbent can be fed to the absorber at a low temperature, for example, 40 °C, and slightly elevated pressure, e.g., 8 bar.

[0033] The absorber has an inlet for the fluid stream. An upstream fan and / or cooler can be provided upstream of the inlet. A device for scrubbing the exhaust gas stream, which has already been freed of carbon dioxide (after absorption), can be provided, in particular, in the upper region of the absorber. The absorber has an outlet, which can usually be provided in the upper part, so that the fluid stream freed of carbon dioxide can leave the absorber as an exhaust stream.

[0034] The absorbent may, for example, comprise monoethanolamine or diethanolamine, or methyldiethanolamine, diisopropylamine, diisopropanolamine, or diglycolamine, or ammonia, or water, or selexol, or methanol. Generally, the absorbent may comprise an amine. The absorbent may, in particular, be an ethanolamine derivative. The absorbent may be in the form of an aqueous solution. A mixture of at least two absorbents, for example, at least two amines, e.g., a mixture of at least two of the amines mentioned, may also be present.

[0035] In the regenerator, carbon dioxide is desorbed from the absorbent, meaning the carbon dioxide is removed, which can then be highly concentrated and released. This allows the end product, carbon dioxide, to be used for later material purposes.

[0036] An intermediate heat exchanger can be present within the absorber circuit as already described above.

[0037] In particular, a blower and / or a pump can be provided in the absorbent circuit for supplying the loaded absorbent toward the intermediate heat exchanger and / or toward the stripper. A blower and / or a pump can also be provided for supplying the regenerated absorbent toward the intermediate heat exchanger and / or toward the absorber.

[0038] The absorbent circuit can be physically configured, in particular, using conduits, such as pipes, hoses, ducts, guides, or other forms of conduits. The absorbent circuit can be a closed or essentially closed circuit. It cannot be ruled out that small portions of the absorbent may leave the absorbent circuit, particularly in the stripper and / or reboiler. This may necessitate the addition of new absorbent.

[0039] Residues of the absorbent as part of the overhead gas may temporarily leave the absorbent circuit due to system requirements, but may be returned to it by backflow into the stripper (e.g. using a separation vessel) and thus potentially reused in the absorbent circuit if appropriate facilities for backflow and separation are provided.

[0040] The heat pump can be a compression heat pump. The terms "condenser," "first expansion valve," "second expansion valve," "first evaporator," "second evaporator," "first compressor," and "second compressor" refer to the refrigerant circuit and the refrigerant.

[0041] The branch is a physical branch into the first circuit section and the second circuit section, e.g. a bifurcation of the lines. Optionally and additionally, at least one further circuit section can be provided, each of which can optionally have its own expansion valve, its own evaporator and / or its own compressor. The optional, at least one further circuit section can also branch off at the branch. The optional, at least one further circuit section can alternatively branch off after the second expansion valve. The optional, at least one further circuit section can alternatively or additionally branch off in a further branch. This makes it possible to cool the top gas stream at at least one further refrigerant temperature or at at least one further refrigerant pressure.

[0042] The branching can be designed such that after the condenser, a first mass flow of the refrigerant (a first portion of the refrigerant flow) in the first circuit section (in particular exclusively) passes the first evaporator and a second mass flow of the refrigerant (a second portion of the refrigerant flow) in the second circuit section (in particular exclusively) passes the second evaporator.

[0043] In other words, the direction of circulation of the refrigerant circuit is the flow direction of the refrigerant in the refrigeration circuit.

[0044] The junction is a physical junction of the first circuit subsection and the second circuit subsection, e.g., a junction of the lines. The optional, at least one further circuit subsection can also be merged with the first circuit subsection and the second circuit subsection at the junction. The optional, at least one further circuit subsection can alternatively be merged with the first circuit subsection or the second circuit subsection before the junction in a further junction. The optional, at least one further circuit subsection can alternatively be merged after the junction in a further junction with another circuit subsection arranged after the junction.The optional, at least one further circuit section can alternatively be combined with the (other) refrigerant circuit in a further union after the union.

[0045] The branch can be configured such that the first portion of the refrigerant flow and the second portion of the refrigerant flow are in a given ratio to each other or with respect to the refrigerant flow. For example, valves can be provided at the branch that can limit or adjust the first portion of the refrigerant flow and / or the second portion of the refrigerant flow. Such valves can be adjustable.

[0046] Other design options for achieving such a desired ratio are also possible: For example, the diameters of the lines forming the first circuit section and / or the second circuit section can be different and designed according to a desired ratio. Other types of resistors can also be incorporated into the lines.

[0047] The first expansion valve and / or the second expansion valve can also be designed to establish a desired ratio in the refrigerant circuit.

[0048] As already explained, within the refrigerant circuit, the refrigerant is at a high pressure after the first compressor (e.g., 80 bar with ammonia as the refrigerant and monoethanolamine, present as an aqueous solution, as the absorbent). After the first expansion valve, the pressure is at a medium pressure (e.g., 37 bar with ammonia as the refrigerant and monoethanolamine, present as an aqueous solution, as the absorbent). The medium pressure can correspond to the first refrigerant pressure. After the second expansion valve, the pressure is at a low pressure (e.g., 13 bar with ammonia as the refrigerant and monoethanolamine, present as an aqueous solution, as the absorbent). The low pressure can correspond to the second refrigerant pressure.

[0049] At high pressure, the refrigerant is at a high temperature (e.g., approximately 112 °C) and within a wide temperature range. At medium pressure, the refrigerant is at a medium temperature within a medium temperature range (e.g., approximately 80 °C). At low pressure, the refrigerant is at a low temperature within a low temperature range (e.g., approximately 40 °C).

[0050] The first expansion valve can be arranged upstream of the branch (as viewed in the direction of circulation of the refrigerant). In an alternative, non-preferred embodiment, the branch can also be made upstream of the first expansion valve (as viewed in the direction of circulation of the refrigerant). The first expansion valve can then be arranged in the first circuit section and only affect the first portion of the refrigerant flow present there, so that the first portion of the refrigerant flow is brought to the medium pressure and the medium temperature in the medium temperature range. The second expansion valve can then be designed to effect a greater expansion than the first expansion valve and the second portion of the refrigerant flow is brought to the low pressure and the low temperature in the low temperature range.

[0051] In another possible embodiment, which can be provided alternatively or in addition to the alternative embodiment already mentioned above, the first compressor in the first circuit section (when viewed in the direction of refrigerant circulation) can be arranged after the first evaporator and before the merging point, and can affect only the first portion of the refrigerant flow present there. The second compressor can then be designed to cause a pressure increase from the low pressure to the high pressure, i.e., a greater pressure increase than the first compressor. At the merging point, both portions of the previously divided refrigerant flow already have the high pressure.

[0052] The first heat exchanger can be connected to a first head gas line carrying the head gas stream for the purpose of extracting thermal energy from the head gas stream. The second heat exchanger can be connected to the first head gas line and / or to another head gas line carrying the head gas stream for the purpose of extracting thermal energy from the head gas stream.

[0053] When reference is made to “connect” or “connected” in this document, particularly with regard to parts of the refrigerant circuit or the absorbent circuit, this may in particular refer to a connection that enables a transfer of thermal energy.

[0054] A separator vessel (cold-out drum) may be provided to separate the carbon dioxide in the overhead gas stream from other components of the overhead gas stream. A backflow of the remaining components from the separator vessel (possibly via a pump) to the stripper may be provided. An outlet may be provided for the final carbon dioxide product.

[0055] In particular, one of the following variants can apply to the reboiler: The reboiler is the third heat exchanger, has the third heat exchanger, or is part of the third heat exchanger, or the third heat exchanger has the reboiler, or the third heat exchanger is part of the reboiler. These variants can each mean "integrally designed." Alternatively, the reboiler can be connected to the third heat exchanger. The third heat exchanger is - with respect to the heat pump and the refrigerant - the condenser. By transferring thermal energy to the absorbent in the reboiler, the carbon dioxide-laden absorbent in the regenerator becomes regenerated absorbent.

[0056] The invention advantageously embodies a transition to economical, sustainable energy use. The first evaporator and the second evaporator, which operate at different pressures and temperatures, achieve a high exergetic efficiency and a high COP value (e.g., over 4) for the heat pump. The COP value is a common metric for heat pumps. COP stands for "Coefficient of Performance." The COP value indicates the ratio of generated heat output to the required drive energy. It is a parameter that indicates the efficiency of the heat pump.

[0057] Even compared to a heat pump with only an evaporator, these parameters are significantly higher – particularly due to the interaction with the special thermal properties of the head gas stream (its condensation in a temperature-enthalpy diagram follows a curve rather than an isothermal line, so heat absorption at different temperatures can increase the efficiency of the heat pump). The required water consumption, the technical effort for generating thermal energy and cooling, the additional carbon dioxide emissions, and the associated costs are all reduced compared to state-of-the-art systems.

[0058] Possible industrial applications in which the plant according to the invention can be used advantageously include, for example, power plants, cement production plants, limestone kilns, (hot) steam reforming plants, steel production plants, paper production plants, biomass combustion plants, bioethanol refineries, refineries in general, petroleum refineries, waste incineration plants, etc. Extracted carbon dioxide can be used in many ways industrially and / or in the private sector.

[0059] The plant according to the invention can also be used to separate other substances, not just carbon dioxide. Therefore, the plant according to the invention for separating components present in a fluid stream or from a component present in a fluid stream is generally disclosed here. This disclosure therefore applies not only to the separation of carbon dioxide, but generally to the separation of at least one (other) substance that can be separated by means of chemical absorption and an absorbent. An example of such another substance can be hydrogen sulfide. Further examples can be acidic gases or hydrogen sulfates. Further examples can be: sulfur dioxide, hydrogen sulfide, hydrogen chloride, nitrogen dioxide, hydrogen cyanide, hydrogen bromide, selenium dioxide.

[0060] It is also disclosed here: The heat pump as used in the context of the invention and described here can also be used for a distillation process.

[0061] Furthermore, the use of the heat pump as described in the invention is possible in the separation of other acidic gases such as hydrogen sulfide from the fluid stream.

[0062] In an advantageous embodiment of the system according to the invention, 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% by weight, preferably 45 to 80% by weight, of the refrigerant flow.

[0063] The refrigerant flow is the total mass flow of refrigerant circulating in the refrigerant circuit. The first portion of the refrigerant flow can, in particular, be related to a unit of time. Particularly preferably, the first portion is 45 to 75 wt.%, even more preferably 48 to 72 wt.%. Reference is made to the described possibilities for setting a desired ratio of the first portion of the refrigerant flow with respect to a second portion of the refrigerant flow or the refrigerant flow.

[0064] A particularly advantageous first portion may depend on the refrigerant used. Specific information for particularly advantageous ranges for various refrigerants is given below in parentheses: 1-Butene (50-70 wt%), Acetone (50-70 wt%), Ammonia (60-80 wt%), Benzene (50-70 wt%), Cis-2-Butene (50-70 wt%), Cyclohexane (50-70 wt%), Cyclopentane (50-70 wt%), Cyclopropane (60-80 wt%), D4 (40-60 wt%), D5 (40-60 wt%), D6 (40-60 wt%), Dichloroethane (50-70 wt%), Diethyl ether (50-70 wt%), Dimethyl carbonate (50-70 wt%), Dimethyl ether (55-75 wt%), Ethanol (50-70 wt%), Ethylbenzene (50-70 wt%), Ethylene oxide (50-70 wt%), Heavy water (50-70 wt%), Isobutane (50-70 wt%), isobutene (50-70 wt%), isohexane (45-65 wt%), isopentane (50-70 wt%), m-xylene (50-70 wt%), MD2M (40-60 wt%), MD3M (40-60 wt%), MD4M (45-65 wt%), MDM (40-60 wt%), methanol (55-75 wt%), MM (40-60 wt%), n-butane (50-70 wt%), n-decane (45-65 wt%), n-dodecane (45-65 wt%), n-heptane (50-70 wt%), n-hexane (50-70 wt%), n-nonane (50-70 wt%), n-octane (50-70 wt%), n-undecane (50-70 wt%), neopentane (50-70% by weight), o-xylene (50-70% by weight).-%), p-xylene (50-70 wt%), propyne (55-75 wt%), R11 (50-70 wt%), R113 (50-70 wt%), R114 (50-70 wt%), R123 (50-70 wt%), R1233zd(E) (50-70 wt%), R1234ze(Z) (50-70 wt%), R124 (55-75 wt%), R13l1 (55-75 wt%), R141b (50-70 wt%), R142b (50-70 wt%), R21 (50-70 wt%), R236ea (50-70 wt%), R236fa (55-75 wt%), R245ca (50-70 wt%), R245fa (50-70 wt%), R365mfc (50-70 wt%), R40 (55-75 wt%), sulfur dioxide (55-75 wt%), toluene (50-70 wt%), trans-2-butene (50-70 wt%), water (55-75 wt%).

[0065] Simulations have shown that using one of the aforementioned first portions of the refrigerant flow achieves a particularly high exergetic efficiency and a particularly high COP value for the heat pump. This is accompanied by a small refrigerant flow. Furthermore, the heat pump can be kept comparatively small and thus resource-efficient. The aforementioned advantages of the invention (particularly with regard to water consumption, technical complexity, additional carbon dioxide emissions, and costs) are further enhanced.

[0066] In an advantageous embodiment of the system according to the invention, 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, R13l1, 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.

[0067] The following terms are used: R11: Trichlorofluoromethane; R113: 1,1,2-trichloro-1,2,2-trifluoroethane; R114: Cryofluorane; R123: 2,2-dichloro-1,1,1-trifluoroethane; R1233zd(E): trans-1-chloro-3,3,3-trifluoropropene; R1234ze(Z): cis 1,3,3,3-tetrafluoropropene; R124: Chlorotetrafluoroethane; R13l1: iodotrifluoromethane; R141b: 1,1-dichloro-1-fluoroethane; R142b: 1-chloro-1,1-difluoroethane; R21: Dichlorofluoromethane; R236fa: 1,1,1,2,3,3-hexafluoropropane; R245ca: 1,1,2,2,3-pentafluoropropane; R245fa: 1,1,1,3,3-pentafluoropropane; R365mfc: 1,1,1,3,3-pentafluorobutane; R40: Monochloromethane.

[0068] Simulations have shown that the refrigerants mentioned can be used in the described heat pump at pressures that allow for a simple heat pump design. In particular, no pressures above 100 bar are required, and with many of the refrigerants mentioned, no pressures below atmospheric pressure are required. Furthermore, the refrigerants mentioned enable comparatively small mass flows in the refrigerant circuit. Furthermore, the heat pump and the refrigerant flow can be kept comparatively small and thus conserve resources. The aforementioned advantages of the invention (particularly with regard to water consumption, technical complexity, additional carbon dioxide emissions, and costs) are further enhanced.

[0069] In an advantageous embodiment of the system according to the invention, 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 amounts to 60 to 75% by weight, preferably 65 to 75% by weight, of the refrigerant flow.

[0070] A range for the first portion of the refrigerant stream of 67 to 71 wt.% is particularly advantageous, a range of 68 to 70 wt.% is even more advantageous, and a first portion of the refrigerant stream of 69 wt.% is especially advantageous. Reference is made to the described possibilities for setting a desired ratio of the first portion of the refrigerant stream with respect to a second portion of the refrigerant stream or the refrigerant stream.

[0071] As simulations have shown, ammonia results in a comparatively particularly low mass flow in the refrigerant circuit compared to other refrigerants, especially compared to all of the refrigerants mentioned above. With the total cooling capacities at the first evaporator and the second evaporator remaining constant, and the heat output at the condenser or reboiler remaining constant, the mass flow is reduced by a factor of approximately two or even more compared to other refrigerants. Furthermore, the pressure ratio between the lowest pressure (second pressure) and the highest pressure (after the first compressor) in the refrigerant circuit is particularly low; advantageously, it can be approximately 5.5.

[0072] The first portion of the refrigerant flow can, in particular, be related to a unit of time. Simulations have shown that, with ammonia, a particularly high exergetic efficiency and a particularly high COP value can be achieved with one of the aforementioned first portions of the refrigerant flow. Furthermore, the heat pump and the refrigerant flow can be kept comparatively small and thus conserve resources. The aforementioned advantages of the invention (particularly with regard to water consumption, technical complexity, additional carbon dioxide emissions, and costs) are further enhanced.

[0073] In an advantageous embodiment of the system according to the invention, a fourth heat exchanger is provided in the refrigerant circuit, which is connected to the absorbent circuit, and the fourth heat exchanger is designed to transfer thermal energy from the regenerated absorbent to the refrigerant.

[0074] The fourth heat exchanger can, for example, be provided (in the direction of circulation of the refrigerant circuit) downstream of the second condenser and upstream of the second compressor. Alternatively—and less preferably, since higher refrigerant temperatures prevail there—it can also be provided downstream of the first condenser and upstream of the first compressor. The fourth heat exchanger can be provided in the second circuit section or—less preferably—in the first circuit section or upstream of the branch. More than one fourth heat exchanger can also be provided on the second circuit section and / or the first circuit section and / or upstream of the branch.

[0075] The fourth heat exchanger can, in particular, cool regenerated absorbent before entering the absorber, so that temperatures in the absorber can be kept low. The fourth heat exchanger can be a fourth evaporator with respect to the refrigerant and the refrigerant circuit. The fourth heat exchanger and the fourth evaporator can form a single unit. The fourth heat exchanger can comprise the fourth evaporator or be designed as an integral part with the fourth evaporator.

[0076] The fourth heat exchanger enables a further increase in the cooling capacity provided by the heat pump at an additional point in the absorption circuit. This saves energy for the (possibly external) cooling otherwise required at this additional point. This enables savings in energy and the associated costs. The aforementioned advantages of the invention (particularly with regard to water consumption, technical complexity, additional carbon dioxide emissions, and costs) are further enhanced.

[0077] In an advantageous embodiment of the system according to the invention, the fourth heat exchanger is arranged in the second circuit section of the refrigerant circuit between the second expansion valve and the second compressor.

[0078] This enables particularly powerful and energy-efficient cooling of regenerated absorbent due to the low temperatures prevailing in the refrigerant circuit.

[0079] The fourth heat exchanger enables an even further increase in the cooling capacity provided by the heat pump at an additional point in the absorption circuit. This allows for particularly advantageous savings in energy for the (possibly external) cooling otherwise required at this additional point. This enables further savings in energy and the associated costs. The aforementioned advantages of the invention (particularly with regard to water consumption, technical complexity, additional carbon dioxide emissions, and costs) are further enhanced.

[0080] In an advantageous embodiment of the system according to the invention, a fifth heat exchanger is provided in the refrigerant circuit, which is connected to a heat source of a process that generates the fluid flow, and the fifth heat exchanger is designed to transfer thermal energy from a device of the process to be cooled to the refrigerant.

[0081] Possible industrial applications in which the system according to the invention can be used advantageously include, for example, power plants, cement production plants, limestone kilns, steam conversion stations, steel production plants, paper production plants, biomass combustion plants, bioethanol refineries, refineries in general, oil refineries, and waste incineration plants. In these industrial applications, numerous systems and devices are used that have a cooling requirement that can possibly be met by the fifth heat exchanger. The process can be a process in one of the aforementioned industrial applications. The heat source of the process can be a heat source of a system used in the process.

[0082] For example, the fifth heat exchanger can serve to cool the fluid flow. For this purpose, the fifth heat exchanger can be arranged at a location upstream of an inlet to the absorber, for example, on a line that carries the fluid flow.

[0083] The fifth heat exchanger can, for example, be provided (in the direction of circulation of the refrigerant circuit) downstream of the second condenser and upstream of the second compressor. Alternatively—and less preferably, since higher refrigerant temperatures prevail there—it can also be provided downstream of the first condenser and upstream of the first compressor. The fifth heat exchanger can be provided in the second circuit section or—less preferably—in the first circuit section or upstream of the branch. More than one fifth heat exchanger can also be provided on the second circuit section and / or the first circuit section and / or upstream of the branch.

[0084] The fifth heat exchanger may be a fifth evaporator with respect to the refrigerant and the refrigerant circuit. The fifth heat exchanger and the fifth evaporator may form a single unit. The fifth heat exchanger may comprise the fifth evaporator or be designed as an integral part with the fifth evaporator.

[0085] The fifth heat exchanger enables a further increase in the cooling capacity provided by the heat pump at an additional point in an upstream industrial process. This saves energy for the external cooling otherwise required at this additional point. This enables savings in energy and the associated costs. The aforementioned advantages of the invention (particularly potentially with regard to savings in cooling water, technical complexity, additional carbon dioxide emissions, and costs) are further enhanced.

[0086] In an advantageous embodiment of the system according to the invention, at least one further circuit section branches off at the branch or at a further branch, wherein a further heat exchanger is provided in the further circuit section, which is designed to transfer thermal energy from the head gas stream (KGS) output from the regenerator to the refrigerant at a further pressure of the refrigerant, wherein the further pressure does not correspond to the first pressure and not to the second pressure.

[0087] Reference is made to the above remarks where applicable.

[0088] The further circuit section can be combined with the (other) refrigerant circuit or the first circuit section or the second circuit section at the junction or at a further junction of the refrigerant circuit. The further pressure can, for example, advantageously be either above the first pressure, between the first pressure and the second pressure, or below the second pressure.

[0089] A further expansion valve (before the further heat exchanger) and / or a further compressor (after the further heat exchanger) can be provided on the further circuit section.

[0090] The additional heat exchanger can be an additional evaporator with respect to the refrigerant and the refrigerant circuit. The additional heat exchanger and the additional evaporator can form a single unit. The additional heat exchanger can comprise the additional evaporator or be designed as an integral part with the additional evaporator.

[0091] The COP value and exergetic efficiency of the heat pump can be further increased by the advantageous design—absorbing thermal energy at a different refrigerant pressure (and temperature). The aforementioned advantages of the invention (particularly with regard to water consumption, technical complexity, additional carbon dioxide emissions, and costs) are further enhanced.

[0092] In an advantageous embodiment of the system according to the invention, at least one additional circuit section branches off at the branch or at an additional branch, wherein at least one additional heat exchanger is provided in the additional circuit section, which is designed to transfer thermal energy from the regenerated absorbent and / or the carbon dioxide-laden absorbent and / or the fluid flow to the refrigerant.

[0093] The additional circuit section can be combined with the (other) refrigerant circuit or the first circuit section or the second circuit section in the junction or an additional junction of the refrigerant circuit. The at least one additional heat exchanger can be used to cool, in particular, regenerated absorbent before entering the absorber and / or the fluid flow before entering the absorber, so that temperatures in the absorber can be kept low. Alternatively or additionally, the carbon dioxide-laden absorbent can be cooled. The additional heat exchanger can be designed as an intercooler for the carbon dioxide-laden absorbent or can have such an intercooler. A first intercooler line can be designed to conduct the carbon dioxide-laden absorbent to the intercooler.A second intercooler line can be designed to supply the now cooled carbon dioxide-laden absorbent to the absorber.

[0094] An additional expansion valve (before the additional heat exchanger) and / or an additional compressor (after the additional heat exchanger) may be provided on the additional circuit section.

[0095] The additional heat exchanger may be an additional evaporator with respect to the refrigerant and the refrigerant circuit. The additional heat exchanger and the additional evaporator may form a single unit. The additional heat exchanger may comprise the additional evaporator or be designed as an integral part with the additional evaporator.

[0096] The additional heat exchanger enables a further increase in the cooling capacity provided by the heat pump at an additional point in the absorber circuit or in relation to the fluid flow. This saves energy for the (possibly external) cooling that would otherwise be required. This enables savings in energy and the associated costs. The aforementioned advantages of the invention (particularly with regard to water consumption, technical complexity, additional carbon dioxide emissions, and costs) are further enhanced.

[0097] In addition, a method for separating carbon dioxide present in a fluid stream is proposed using a plant according to the invention, comprising - carrying out a chemical absorption of the carbon dioxide present in the fluid stream using an absorber, - carrying out carbon dioxide desorption of carbon dioxide-laden absorbent using a regenerator, the regenerator comprising a stripper and a reboiler, - feeding the carbon dioxide-laden absorbent from the absorber to the regenerator and feeding regenerated absorbent from the regenerator to the absorber by means of an absorbent circuit in which absorbent is present, - Providing a heat pump having a refrigerant and a refrigerant circuit configured to circulate a refrigerant flow therein, wherein a condenser, a first expansion valve and a second expansion valve, a first evaporator and a second evaporator, and a first compressor and a second compressor are provided in the refrigerant circuit.

[0098] With respect to the direction of circulation of the refrigerant circuit, the refrigerant circuit downstream of the condenser has a branch to a first circuit section and a second circuit section, and the refrigerant circuit upstream of the condenser has a junction of the first circuit section and the second circuit section. The first evaporator is arranged in the first circuit section, and the second evaporator is arranged in the second circuit section.

[0099] With respect to the direction of circulation, the first expansion valve is arranged upstream of the first evaporator and either upstream of the branch or downstream of the branch in the first circuit section. With respect to the direction of circulation, the first compressor is arranged downstream of the first evaporator and either upstream of the junction in the first circuit section or downstream of the junction. With respect to the direction of circulation, the second expansion valve is arranged in the second circuit section and upstream of the second evaporator. With respect to the direction of circulation, the second compressor is arranged in the second circuit section and downstream of the second evaporator.

[0100] The first evaporator is a first heat exchanger or is connected to a first heat exchanger, the first heat exchanger being configured to transfer thermal energy from a head gas stream discharged from the regenerator to the refrigerant at a first refrigerant pressure. The second evaporator is a second heat exchanger or is connected to a second heat exchanger, the second heat exchanger being configured to transfer thermal energy from the head gas stream to the refrigerant at a second refrigerant pressure, the second pressure being lower than the first pressure.

[0101] Furthermore, the procedure has - transferring thermal energy from a head gas stream discharged from the regenerator to the refrigerant by means of the first heat exchanger at the first pressure of the refrigerant, - transferring thermal energy from the head gas stream to the refrigerant by means of the second heat exchanger at the second pressure of the refrigerant, - Transferring thermal energy from the refrigerant to the absorbent in the reboiler by means of the condenser, which is a third heat exchanger connected to or integral with the reboiler.

[0102] The process can be used to operate any plant according to the invention for separating carbon dioxide present in the fluid stream, which has been structurally described above. The features of the presented embodiments of the plant according to the invention or process features described above can be the subject of the process according to the invention. With regard to the process according to the invention, reference is made in full to the embodiments of the plant according to the invention, and vice versa. The process presented can be carried out at least partially or fully automated.

[0103] The process according to the invention can also be used to separate other substances, not just carbon dioxide. Therefore, the process according to the invention for separating components present in a fluid stream or a component present in a fluid stream is generally disclosed here. This disclosure therefore applies not only to the separation of carbon dioxide, but generally to the separation of at least one (other) substance that can be separated by means of chemical absorption and an absorbent.

[0104] The invention is described below using exemplary embodiments. They show: Fig. 1 a schematic representation of a system according to the invention, Fig. 2 a schematic, qualitative log-ph diagram of the states of the refrigerant in the refrigerant circuit of the heat pump of the system according to the invention as shown in Fig. 1 is shown, Fig. 3 a schematic, qualitative TQ diagram of the head gas flow of the plant according to the invention as shown in Fig. 1 is shown, Fig. 4 a schematic representation of a system according to the invention in a further embodiment, Fig. Figure 5 schematically shows a process according to the invention for separating carbon dioxide in a fluid stream.

[0105] Identical reference symbols used in different figures mean identical or essentially equivalent features / parts / instances, even if not all features shown with reference symbols are referred to again in each figure.

[0106] Fig. Figure 1 shows a schematic representation of a plant ANL according to the invention. A fluid stream AG1, which may be an exhaust gas stream from a power plant, is fed to an absorber A via a fan G1 and a cooler KL1. The fluid stream AG1 is located in a line indicated by an arrow in Fig. 1. The path of the fluid stream AG1 is schematically represented by arrows, which symbolize lines. The respective directions of the arrows correspond to the flow direction. For this purpose, the ANL system has suitable lines, e.g., gas lines, ducts, and / or pipes and / or other lines. The absorber A is designed to carry out a chemical absorption of the carbon dioxide present in the fluid stream. In absorber A, monoethanolamine, presently as an aqueous solution, is used as the absorber. Another absorber is also possible. The absorber A is designed to absorb carbon dioxide. An exhaust gas stream AG2 freed from carbon dioxide can leave the absorber in the upper area through an outlet. The fluid stream AG2 leaves the ANL system in an outlet line, which is indicated by an arrow in Fig. 1. The direction of the arrow corresponds to the direction of flow.

[0107] The absorbent can circulate in an absorber circuit (AKL). Connected to the lower section of absorber A are lines designed to transport the carbon dioxide-laden absorbent, first from absorber A to a pump P1, then via an intermediate heat exchanger (ZWT), where it is preheated, to a stripper S.

[0108] The stripper S is designed to remove carbon dioxide from the loaded absorbent with the aid of a reboiler R. The carbon dioxide then becomes part of a top gas stream KGS, which can be removed from the top of the stripper S via a corresponding line for the top gas stream KGS. The stripper S and the reboiler R can be collectively referred to as a regenerator. The top gas stream KGS is located in a line indicated by an arrow in Fig. 1. The path of the head gas flow KGS is schematically represented by arrows representing lines. The directions of the arrows correspond to the flow direction.

[0109] From the stripper S, the line for the head gas stream leads to a first evaporator V1 of a refrigerant circuit KKL of a heat pump HP. Ammonia circulates in this evaporator in the form of a refrigerant stream. Another refrigerant is also possible. The first evaporator V1 is designed as an integral heat exchanger, configured to cool the head gas stream KGS at a medium temperature range (e.g., 80 °C) and at a medium refrigerant pressure, e.g., 37 bar. A line now leads from the first evaporator V1 to a second evaporator V2 of the refrigerant circuit KKL. The second evaporator V2 is designed as an integral heat exchanger, configured to cool the head gas stream KGS at a low temperature range (e.g., 40 °C) and at a low refrigerant pressure, e.g., 12 bar. The terms first evaporator V1 and second evaporator V2 are to be understood in relation to the refrigerant of the heat pump WP.With regard to the head gas stream KGS, both cases involve coolers and / or condensers - thermal energy is transferred from the head gas stream KGS to the refrigerant, thereby cooling the head gas stream KGS.

[0110] A line leads from the second evaporator V2 to a separation vessel AB, which is designed, on the one hand, to generate a reflux stream RF, which can be fed back to the stripper via a pump P3. On the other hand, it is designed to separate the end product carbon dioxide CO2 from the overhead gas stream, as indicated by arrows in Fig. 1. The final product, carbon dioxide, can be used for further processing and / or sequestration. The return stream RF is located in a line indicated by an arrow in Fig. 1. The path of the return current RF is schematically represented by arrows representing lines. The directions of the arrows correspond to the direction of flow.

[0111] The refrigerant circuit KKL of the heat pump WP has a first compressor K1, after which (when viewed in the direction of circulation, symbolized by the arrows schematically comprising the KKL refrigerant circuit) a line leads to the reboiler R. The reboiler R is designed as a heat exchanger and can, among other things, heat the absorbent passing through it as part of a regeneration process, transforming it from loaded absorbent into regenerated absorbent. The regenerated absorbent is fed back into the upper section of the absorber A via a pump P2 and the intermediate heat exchanger ZWT for cooling, and via another cooler KL2.

[0112] In terms of the refrigerant circuit, the reboiler R is a condenser. The reboiler R is constructed as an integral part together with the condenser and is therefore referred to simply as the reboiler R.

[0113] A first expansion valve EV1 can throttle the refrigerant flow toward the medium pressure and temperature range. The terms "high," "medium," and "low" are relative terms with regard to pressures and temperatures. A branch VZ follows the first expansion valve EV1, which can be physically configured, for example, as a line fork or line divider. The branch VZ can regulate the division of the refrigerant flow, e.g., by means of adjustable valves, so that a specific ratio of a first portion of the refrigerant flow and a second portion of the refrigerant flow can be achieved or additionally adjusted after the branch VZ.

[0114] After the branching point VZ, there is a first circuit section TA1 and a second circuit section TA2. In the example, the branching is designed such that 69% by weight of the refrigerant flow (first portion of the refrigerant flow) is routed through the first circuit section TA1. 31% by weight of the refrigerant flow (second portion of the refrigerant flow) is routed through the second circuit section TA2. The lines of the first circuit section, in which the first portion of the refrigerant flow is routed, pass through the first evaporator V1 for the purpose of absorbing thermal energy by the refrigerant.

[0115] Both the first circuit section TA1 and the second circuit section TA2 as well as all other parts of the refrigerant circuit KKL are designed by pipes and in Fig. 1 is symbolized by arrows indicating the respective flow direction. In other cases, Fig. 1 (and in Fig. 4 also) lines are represented by arrows, whereby the respective direction of an arrow corresponds to the intended flow direction in the respective line.

[0116] A second expansion valve EV2 is designed to throttle the second portion of the refrigerant flow in the second circuit section TA2 towards a low pressure and a low temperature range. The lines of the second circuit section, in which the second portion of the refrigerant flow (31 wt. % of the refrigerant flow) is conducted, pass through the second evaporator V2 for the purpose of absorbing thermal energy by the refrigerant. Here, the temperature range and pressure of the refrigerant are low. A second compressor can raise the temperature of the refrigerant to the medium temperature range and raise the pressure of the refrigerant to the medium pressure. A union VE can be designed in particular as a line combination. It is designed to combine the first circuit section TA1 and the second circuit section TA2. In the downstream first compressor K1, the refrigerant can be pressurized to a high pressure (e.g.B. 80 bar) and brought into a high temperature range (e.g. 110 °C).

[0117] Fig. Figure 2 shows a schematic, qualitative log-ph diagram of the states of the refrigerant in the refrigerant circuit of the heat pump WP of the system ANL according to the invention as shown in Fig. 1. The behavior of the refrigerant is represented by arrows that correspond to the direction of circulation of the refrigerant in the heat pump.

[0118] Line 1 shows an isobaric heat release in the reboiler R at the high pressure and in the high temperature range. This is followed, in line 2, by an isenthalpic expansion, corresponding to the first expansion valve EV1, advantageously starting on the boiling line. A branching point VZP corresponds to the situation at the branching point VZ ( Fig. 1). This is followed in line 3 by a further isenthalpic expansion (expansion valve EV2) for the second portion of the refrigerant flow. In line 4, the second portion of the refrigerant flow undergoes heat absorption (second evaporator) at the low pressure in the low temperature range. In curve 5, the second portion of the refrigerant flow undergoes a compression (second compressor), which is irreversible (the assumed isentropic efficiency can be, for example, 0.72).

[0119] In line 6, heat absorption occurs for the first portion of the refrigerant flow at the medium pressure in the medium temperature range (first evaporator) up to an end point before the (subsequent) mixing EPVM. Adiabatic mixing of the first refrigerant flow and the second refrigerant flow occurs due to the merging VE. The enthalpy of the first refrigerant flow increases as a result, represented by line 7A. The enthalpy of the second refrigerant flow decreases as a result, represented by line 7B. The mixed state of the first refrigerant flow and the second refrigerant flow is represented by the merging point VEP, which corresponds to the situation of the now recombined refrigerant flow after the merging and at the inlet of the first compressor K1. Advantageously, the merging point VEP lies on the dew line. Subsequent compression by the first compressor K1 toward the high pressure and high temperature range is shown in curve 8.After this, the process starts again with an isobaric heat release in the reboiler R. .

[0120] Fig. Figure 3 shows a schematic, qualitative TQ diagram of the head gas flow. Curve 13 qualitatively shows a possible behavioral profile of the head gas flow KGS as an example. Line 12 represents heat absorption in the second evaporator V2 by the refrigerant in the low temperature range. Line 11 represents heat absorption in the first evaporator V1 by the refrigerant in the medium temperature range. The smaller the area between lines 11 and 12 and curve 13, the more heat can be absorbed by the heat pump and the higher the COP value of the heat pump. The rectangular area below line 11, which extends down to the temperature of line 12, demonstrates the exergetic advantage of the invention compared to a single-stage, conventional heat pump.It can be seen that the two evaporators operating at different temperatures contribute to a high COP value, especially compared to single-stage heat pumps.

[0121] Fig. Figure 4 shows a schematic representation of a system ANL2 according to the invention in a further embodiment. It differs from the system shown in Fig. 1 in that a (further) fourth heat exchanger WT4 is provided. It is located in the second section TA2 and further cools the regenerated absorbent coming from the intermediate heat exchanger ZWT before it enters absorber A.

[0122] Fig. Figure 5 schematically shows a process according to the invention for separating carbon dioxide in a fluid stream.

[0123] In a first step S1, chemical absorption of the carbon dioxide present in the fluid stream is carried out using an absorber (e.g. absorber A) and an absorbent, e.g. an aqueous solution of monoethanolamine.

[0124] Subsequently, in a second step S2, carbon dioxide desorption of carbon dioxide-laden absorbent takes place using a regenerator, wherein the regenerator comprises a stripper (e.g. stripper S) and a reboiler (e.g. reboiler R).

[0125] In a third step S3, a resulting head gas stream (e.g. head gas stream KGS) is led out of the stripper S and, with the help of a first evaporator (e.g. first evaporator V1) and a second evaporator (e.g. second evaporator V2), both of which act as heat exchangers and parts of a heat pump (e.g. heat pump WP, cf. Fig. 1 and Fig.4) are cooled in two different temperature ranges of a refrigerant, with lower temperatures at the second evaporator V2 than at the first evaporator V1. At the second evaporator V2 the refrigerant has a lower pressure than at the first evaporator V1. The lower pressure at the second evaporator V2 is achieved by a mass division in the refrigerant circuit (e.g. refrigerant circuit KKL) of the heat pump WP by two parallel circuit sections (e.g. first circuit section KT1 and second circuit section KT2), ​​with an additional throttle (e.g. second expansion valve EV2) in the second circuit section. A first throttle (e.g. first expansion valve EV1) is located upstream of the mass division in the refrigerant circuit KKL. The mass division can be achieved by means of a branch (e.g. branch VZ).

[0126] The first evaporator V1 and the second evaporator V2 each provide cooling for the head gas stream (e.g., head gas stream KGS). In a fourth step S4, the absorbent is heated in the reboiler R, which is designed as a heat exchanger and is also part of the heat pump HP, during regeneration—i.e., the removal of carbon dioxide from the absorbent. Steps S1, S2, S3, and S4 can all be performed at least partially or all in parallel and continuously for a continuous fluid flow, since both the absorbent and the refrigerant circulate in circuits. Reference symbol 1 isobaric heat release 11 Heat absorption in the first evaporator 12 Heat absorption in the second evaporator 13 Course of a behavior of the head gas flow 2 isenthalpic expansion 3 further isenthalpic expansion 4 Heat absorption 5 Compression 6 Heat absorption 7 isobaric heat release 7A Enthalpy change due to mixing 7B Enthalpy change due to mixing 8 Compression A absorber AB separator tank AG1 Fluid flow AG2 exhaust gas flow AKL absorbent circuit ANL facility ANL2 system CO2 end product carbon dioxide EPVM endpoint before mixing EV1 first expansion valve EV2 second expansion valve G1 blower K1 first compressor KGS head gas stream KKL refrigerant circuit KL1 cooler KL2 cooler P1 pump P2 pump P3 pump R Reboiler RF return current S Stripper S1-S4 steps TA1 first circuit section TA2 second circuit section V1 first evaporator V2 second evaporator VE Association VEP union point VZ branching VZP branching point WP heat pump WT4 fourth heat exchanger ZWT intermediate heat exchanger

Claims

[1] Plant (ANL, ANL2) for separating carbon dioxide in a fluid stream (AG1), comprising - an absorber (A) designed to carry out a chemical absorption of the carbon dioxide present in the fluid stream (AG1), - an absorbent, - a regenerator designed to carry out carbon dioxide desorption from carbon dioxide-laden absorbent, the regenerator comprising a stripper (S) and a reboiler (R), - an absorber circuit (AKL) designed to supply the carbon dioxide-laden absorber from the absorber (A) to the regenerator and to supply regenerated absorber from the regenerator to the absorber (A), - a heat pump (WP) comprising a refrigerant and a refrigerant circuit which is designed such that a refrigerant flow circulates therein, where in the refrigerant circuit are provided - a condenser, - a first expansion valve (EV1) and a second expansion valve (EV2), - a first evaporator (V1) and a second evaporator (V2), - a first compressor (K1) and a second compressor (K2), wherein, with respect to a direction of circulation of the refrigerant circuit (KKL), the refrigerant circuit (KKL) downstream of the condenser has a branch (VZ) to a first circuit section (TA1) and a second circuit section (TA2), and the refrigerant circuit (KKL) upstream of the condenser has a union (VE) of the first circuit section (TA1) and the second circuit section (TA2), wherein the first evaporator (V1) is arranged in the first circuit section (TA1) and the second evaporator (V2) is arranged in the second circuit section (TA2), wherein, with respect to the direction of circulation, the first expansion valve (EV1) is arranged upstream of the first evaporator (V1) and either - before the junction (VZ) or - after the branching (VZ) in the first circuit section (TA1) is arranged, wherein, with respect to the direction of circulation, the first compressor (K1) is arranged after the first evaporator (V1) and either - before the union (VE) in the first circuit section (TA1) or - after unification (VE) is arranged, wherein, with respect to the direction of circulation, the second expansion valve (EV2) is arranged in the second circuit section (TA2) and upstream of the second evaporator (V2) and, with respect to the direction of circulation, the second compressor (K2) is arranged in the second circuit section (TA2) and downstream of the second evaporator (V2), wherein the first evaporator (V1) is a first heat exchanger or is connected to a first heat exchanger, wherein the first heat exchanger is designed to transfer thermal energy from a head gas stream (KGS) discharged from the regenerator to the refrigerant at a first refrigerant pressure, wherein the second evaporator (V2) is a second heat exchanger or is connected to a second heat exchanger, wherein the second heat exchanger is designed to transfer thermal energy from the head gas stream (KGS) to the refrigerant at a second pressure of the refrigerant, wherein the second pressure is lower than the first pressure, wherein the condenser is a third heat exchanger connected to or integral with the reboiler (R) and configured to transfer thermal energy from the refrigerant to the absorbent located in the reboiler (R). [2] Plant (ANL, ANL2) according to claim 1, characterized by that the refrigerant circuit (KKL) is designed such that a first portion of the refrigerant flow circulates through the first evaporator (V1), wherein the first portion amounts to 45 to 95% by weight, preferably 45 to 80% by weight, of the refrigerant flow. [3] Plant (ANL, ANL2) according to claim 1 or 2, characterized bythat 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, R13l1, 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. [4] Plant (ANL, ANL2) according to one of claims 1-3, characterized by that the refrigerant is ammonia and that the refrigerant circuit (KKL) is designed such that a first portion of the refrigerant flow circulates through the first evaporator (V1), wherein the first portion amounts to 60 to 75% by weight, preferably 65 to 75% by weight, of the refrigerant flow. [5] Plant (ANL, ANL2) according to one of claims 1-4, characterized by that a fourth heat exchanger (WT4) is provided in the refrigerant circuit (KKL), which is connected to the absorbent circuit (AKL) and is designed to transfer thermal energy from the regenerated absorbent to the refrigerant. [6] Plant (ANL, ANL2) according to claim 5, characterized by that the fourth heat exchanger (WT4) is arranged in the second circuit section (TA2) of the refrigerant circuit (KKL) between the second expansion valve (EV2) and the second compressor (K2). [7] Plant (ANL, ANL2) according to one of claims 1-6, characterized bythat a fifth heat exchanger is provided in the refrigerant circuit (KKL), which is connected to a heat source of a process which generates the fluid flow (AG1) and is designed to transfer thermal energy from a device of the process to be cooled to the refrigerant. [8] Plant (ANL, ANL2) according to one of claims 1-7, characterized by that at least one further circuit section branches off at the branch or at a further branch, wherein a further heat exchanger is provided in the further circuit section, which is designed to transfer thermal energy from the head gas stream (KGS) output from the regenerator to the refrigerant at a further pressure of the refrigerant, wherein the further pressure does not correspond to the first pressure and not to the second pressure. [9] Plant (ANL, ANL2) according to one of claims 1-8, characterized bythat at least one additional circuit section branches off at the branch or at an additional branch, wherein at least one additional heat exchanger is provided in the additional circuit section, which is designed to transfer thermal energy from the regenerated absorbent and / or the carbon dioxide-laden absorbent and / or the fluid stream (AG1) to the refrigerant. [10] A method for separating carbon dioxide present in a fluid stream (AG1) using a plant (ANL, ANL2) according to any one of claims 1-9, comprising - carrying out a chemical absorption of the carbon dioxide present in the fluid stream (AG1) using an absorber (A), - carrying out carbon dioxide desorption of carbon dioxide-laden absorbent using a regenerator, the regenerator comprising a stripper (S) and a reboiler (R), - feeding the carbon dioxide-laden absorbent from the absorber (A) to the regenerator and feeding regenerated absorbent from the regenerator to the absorber (A) by means of an absorbent circuit (AKL) in which absorbent is present, - Providing a heat pump (WP) comprising a refrigerant and a refrigerant circuit (KKL) which is designed such that a refrigerant flow circulates therein, wherein a condenser, a first expansion valve (EV1) and a second expansion valve (EV2), a first evaporator (V1) and a second evaporator (V2) as well as a first compressor (K1) and a second compressor (K2) are provided in the refrigerant circuit (KKL), wherein, with respect to a direction of circulation of the refrigerant circuit (KKL), the refrigerant circuit (KKL) downstream of the condenser has a branch (VZ) to a first circuit section (TA1) and a second circuit section (TA2), and the refrigerant circuit (KKL) upstream of the condenser has a union (VE) of the first circuit section (TA1) and the second circuit section (TA2), wherein the first evaporator (V1) is arranged in the first circuit section (TA1) and the second evaporator (V2) is arranged in the second circuit section (TA2), wherein, with respect to the direction of circulation, the first expansion valve (EV1) is arranged upstream of the first evaporator (V1) and either upstream of the branch (VZ) or downstream of the branch (VZ) in the first circuit section (TA1), wherein, with respect to the direction of circulation, the first compressor (K1) is arranged after the first evaporator (V1) and either before the union (VE) in the first circuit section (TA1) or after the union (VE), wherein, with respect to the direction of circulation, the second expansion valve (EV2) is arranged in the second circuit section (TA2) and upstream of the second evaporator (V2) and, with respect to the direction of circulation, the second compressor (K2) is arranged in the second circuit section (TA2) and downstream of the second evaporator (V2), wherein the first evaporator (V1) is a first heat exchanger or is connected to a first heat exchanger, wherein the first heat exchanger is designed to transfer thermal energy from a head gas stream (KGS) discharged from the regenerator to the refrigerant at a first refrigerant pressure, wherein the second evaporator (V2) is a second heat exchanger or is connected to a second heat exchanger, wherein the second heat exchanger is designed to transfer thermal energy from the head gas stream (KGS) to the refrigerant at a second pressure of the refrigerant, wherein the second pressure is lower than the first pressure, - Transferring thermal energy from a head gas stream (KGS) discharged from the regenerator to the refrigerant by means of the first heat exchanger at the first refrigerant pressure, - Transferring thermal energy from the head gas stream (KGS) to the refrigerant using the second heat exchanger at the second refrigerant pressure, - Transferring thermal energy from the refrigerant to the absorbent located in the reboiler (R) by means of the condenser, which is a third heat exchanger connected to or integral with the reboiler (R).

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