Patent Application
20240050890
The invention concerns a method for capturing a molecule of interest contained in a gaseous effluent, preferably in an industrial gaseous effluent, said method especially implementing a step for capturing a molecule of interest by a chemical absorbent and a step for regenerating the chemical absorbent loaded with the molecule of interest. The invention also concerns a system for capturing a molecule of interest contained in a gaseous effluent, said system for capturing a molecule of interest comprising at least one absorption column for capturing a molecule of interest by a chemical absorbent and a regeneration column. The invention can be applied to industrial gaseous effluents as well as to native gaseous effluents such as natural gas.
Carbon dioxide is considered to be responsible for 60% of global warming caused by greenhouse gases or ‘GHGs’ (according to data published by the Commissariat général du développement durable [Commissioner-General for Sustainable Development] in ‘Chiffres clés du climat France, Europe et Monde [Key figures for the climate in France, Europe and the World]’ 2019 edition). Carbon dioxide (CO2) is the main greenhouse gas, and is released, for example, through gaseous effluents, such as industrial gaseous effluents, especially when fossil fuels are burned to provide electricity and heat. These industrial processes include, for example, fossil fuel-based power plants, steel-making plants, biomass-based power plants, natural gas processing plants, synthetic fuel plants, refineries, petrochemical plants, cement plants and fossil fuel-based hydrogen production plants.
Several ways have been explored to reduce these CO2 emissions, such as more efficient use of energy, prioritising the use of alternative fuels and energy sources, and carbon capture and sequestration (CCS). Increasing energy efficiency and the transition to renewable energy will reduce CO2 emissions, but the impact of such measures is likely to be significant only in the long term. Carbon capture and storage (CCS) is a promising technology option to reduce CO2 emissions on a shorter time scale. Thus, according to the roadmap of the International Energy Agency, 20% of total CO2 emissions must be eliminated by CCS by 2050.
The CCS process involves separation of CO2 (e.g., from other compounds in the industrial effluent) followed by pressurisation, transport and sequestration or transformation. Many CO2 capture technologies have been developed, in particular for thermal power plants or other industrial processes. Indeed, it is estimated that 50% of the world's anthropogenic carbon dioxide emissions come from the combustion of fossil fuels in power plants or other industrial processes. In addition, in some regions, for example in Europe, industries emitting large quantities of CO2 gas are taxed and/or are required to purchase trading rights for CO2 on the basis of their use as raw material for CO2 gas production, which often makes these energy production methods uneconomical. Thus, the majority of current development efforts are dedicated to the removal of carbon dioxide from the gaseous effluents of industrial processes.
CO2 capture technologies developed include post-combustion capture, pre-combustion capture, oxy-fuel combustion capture, and chemical loop combustion capture. Various carbon dioxide separation technologies can be used with these options, such as chemical absorption, physical absorption, adsorption and membrane separation. Among these, chemical absorption technology has been the subject of the most development and implementation making it a solution of choice for CO2 capture.
The traditional method described in general studies on petroleum refining processes (Le raffinage du pétrole tome 3 procédés de transformation [Petroleum refining volume 3 transformation methods]). P. Leprince, Editions Technip 1998) is called amine treatment. This method consists of effecting the coupling (thermal and material) between two steps (or unit operations). The first step uses a chemical absorption column that selectively captures gaseous CO2 by an acid/base chemical reaction between a liquid amine solution (or equivalent basic solution) that contacts the gas flow in countercurrent under relatively high pressure conditions. The second stage uses a so-called regeneration column in which the chemical complex between the amine function and the CO2 formed during the first stage is decomposed by a supply of thermal energy and by adjusting the pressure to the lowest value possible. This method can be used in many other gas treatments and for many other molecules of interest. It therefore does not exclusively concern CO2.
Unfortunately, capture by chemical absorption methods is particularly energy consuming. For example, the absorption of CO2 by amine-based solutions is known to be very effective and selective in absorbing the CO2 gas. However, the recovery of CO2 from such solutions, also known as the regeneration step, is highly endothermic. As a result, this regeneration process requires additional energy consumption which results, when this energy comes from fossil fuel combustion, in additional CO2 gas emissions or a reduction in CCS energy efficiency.
Numerous solutions have been proposed to improve the energy efficiency of CO2 capture. Unfortunately, these optimisation efforts have shown that it is difficult to find an economical way to reduce reboiler energy requirements by more than 10% (S. Freguia et al. AlChE J., 49(7), 1676 (2003)).
In particular, many studies have focused on optimising the capture process itself, especially through optimisations making it possible to find optimal operating conditions relative to the calculated operating and investment costs. For example, strategies have been proposed for intermediate cooling of the absorption column, the implementation of a multi-pressure configuration at the regeneration column, the decompression of the liquid formed in the regeneration column to form water vapour and CO2 or the integration of the vapour generated into the compressor system (M. Karimi, et al., Chem. Eng. Res. Des., 89(8), 1229 (2011)).
These techniques have limitations. For example, the integration of CO2 compressor during the regeneration of the absorbent leads to an increase in investment and energy requirements and was therefore not considered to be a good configuration for the capture of CO2 (M. Karimi, et al., Chem. Eng. Res. Des., 89(8), 1229 (2011)).
In addition, the treatment of CO2-rich gas with an amine must comply with a constraint related to a temperature not to be exceeded at the risk of damaging the chemical absorbent. For example, when the temperatures used in the system exceed 120° C., there may be an acceleration of amine degradation.
There are therefore numerous methods for capturing a molecule of interest including the use of a chemical absorbent and the regeneration of this chemical absorbent loaded with the molecule of interest. However, the costs associated with regeneration processes are too high. There is therefore a need for new methods and systems for capturing a molecule of interest, such as CO2, from gaseous effluent having reduced costs associated with the regeneration process, without major modification of the industrial process already in place.
The objective of the invention is to remedy the disadvantages of the prior art. In particular, the objective of the invention is to propose a method for capturing a molecule of interest which consumes less thermal energy than the methods described in the prior art and which, in particular, has a reduced energy requirement at the reboiler of the regeneration column. Another objective of the invention is to propose a system for capturing a molecule of interest capable of implementing a method having an improved energy efficiency and having reduced design costs, especially by means of the reboiler being undersized.
To this end, the invention relates to a method for capturing a molecule of interest contained in a gaseous effluent, preferably in an industrial gaseous effluent, said method implementing:
As will be described below, the present invention is especially based on a significant change in the conditions and in the technology implemented for the regeneration of the chemical absorbent. Such a method makes it possible to intensify the regeneration step of the chemical absorbent. In addition, when it is applied to CO2 capture, it allows the CO2 compression and conditioning step to be initiated at the same time and, in some embodiments, the CO2 compression and conditioning step to be performed completely since it has been freed of water.
This new method has the advantage of greatly reducing the heat demand to be supplied to the step of regeneration of the chemical absorbent by using the heat of the compression step via a heat transfer step. This new method allows many possibilities for arranging the regeneration and condensation sections provided that an inter-section heat transfer is carried out (for example via an inter-section heat exchanger arranged to carry out the heat transfer) and that a pressure jump of at least two bar, preferably at least three bar, is carried out between the regeneration section and the condensation section (for example via a compressor positioned before the condensation section).
The original feature of the method of the invention is to produce a gas at the top of the condensation section having a water content lower than that of the methods used in the usual regeneration columns. As a result, in addition to energy savings, the method could make it possible to reduce or eliminate the need for equipment such as pumps and system for treating cooling water of the condensation circuit, condensers at the top of the column and also, in some configurations, dehydrator and dryer downstream of the condenser.
Depending on other optional characteristics of the method, the method may optionally include one or more of the following, alone or in combination:
The invention also relates to a system for capturing a molecule of interest contained in a gaseous effluent, preferably in an industrial gaseous effluent, said system for capturing a molecule of interest comprising at least one absorption column for capturing the molecule of interest by a chemical absorbent, characterised in that it further comprises:
Depending on other optional characteristics of the system, this system may optionally include one or more of the following, alone or in combination:
The invention also concerns an industrial plant equipped with a system for capturing a molecule of interest according to the invention.
Other advantages and characteristics of the invention will become apparent on reading the following description given by way of illustrative and non-limiting example, in reference to the attached figures:
As will be appreciated, the proportion and relative scale of the elements provided in the FIGS. are intended to illustrate the embodiments of the present invention, and should not be taken in a limiting sense. As used in the figures, a ‘line’ associated with the system indicates a pipe or conduit formed of suitable material and sufficiently sized for the transport of a fluid (e.g., liquid or gas) within the line. It is understood that one or more pumps and/or compressors or other known devices for moving the fluid are also associated with the line and with the components of the integrated system discussed here. Such devices, however, are not systematically illustrated so as to allow the figures to better represent the present invention. The arrowheads represented on the ‘lines’ seen in the figures of the integrated system indicate the direction of flow of the fluid.
In addition, aspects of the present invention are described with reference to flowcharts and/or block diagrams of methods and apparatus (systems) according to embodiments of the invention. In the following detailed description of the present description, reference is made to an attached drawing, which forms part of the present description, and the way in which one or more embodiments of the invention can be put into practice is shown by way of illustration. These embodiments are described in sufficient detail to enable the person skilled in the art to put into practice the embodiments of this disclosure, and it should be understood that other embodiments may be used and process, chemical and/or structural changes may be carried out without exceeding the scope of this disclosure.
In the figures, the flowcharts and functional diagrams illustrate the architecture, functionality and operation of possible implementations of systems and methods according to various embodiments of the present invention. In this respect, each block in the flowcharts or block diagrams can represent a system, a device or a module, which is arranged to implement the specified action or actions. In some implementations, the functions associated with the blocks may appear in a different order than that shown in the figures. For example, two blocks shown in succession can, in fact, be implemented substantially simultaneously, or the blocks can sometimes be implemented in reverse order, depending on the action involved.
In the remainder of the description, the expression ‘molecule of interest’ may correspond to any molecule that could damage a system or reduce the efficiency of a method or the quality of a product (e.g., H2S, H2O) or for environmental reasons (e.g., CO2).
In the remainder of the description, the expression ‘chemical absorbent’ may correspond to any chemical species allowing the fixation, adsorption or absorption of atoms, molecules or ions in a gas, liquid or solid phase. In the context of the present invention, a chemical absorbent makes it possible, in particular, to retain H2S or CO2. As will be detailed, a chemical absorbent within the meaning of the invention may be an amine, i.e., a molecule comprising at least one amine group, but may also be a molecule comprising an ammonium group. In particular, an amine within the meaning of the invention may be an ethanolamine.
The expression ‘chemical absorbent loaded with a molecule of interest’ or ‘enriched chemical absorbent’ corresponds to a chemical absorbent combined with or associated with a molecule of interest such as H2S or CO2. There may be different forms of combinations. This can be a chemical bond as for amines but other forms could be considered.
The expression ‘regenerated chemical absorbent’ corresponds to a chemical absorbent that has regained its absorbent properties after use and at least partial release of CO2.
The expression ‘gaseous effluent’, within the meaning of the invention, corresponds to a gas phase comprising a molecule of interest which it is desirable to separate from other molecules. A gaseous effluent may correspond to an anthropogenic effluent but also to natural gas.
The expression ‘industrial gaseous effluent’, within the meaning of the invention, corresponds to air contaminated by volatile organic compounds, dust, nitrous or sulphurous compounds, and, more particularly, carbon dioxide. As used here, the expression industrial gaseous effluent may correspond to any post-treatment gas containing at least one molecule of interest to be separated, such as H2S or CO2. Examples of industrial effluent gases or effluent gases comprise combustion gases, exhaust gases from internal combustion engines, landfill gases and/or process gases of an industrial process and containing CO2 or another acid gas such as H2S, such as those described herein.
The ‘multitubular system’ within the meaning of the invention corresponds to a configuration formed by one or more condensation sections and by one or more regeneration sections.
The term ‘comprises’ and its variants have no limiting meaning when these terms appear in the description and claims. In particular, where it is specified that a product comprises a particular element, it should be understood that it may also comprise several elements.
The term ‘and/or’ means one, more or all of the items listed.
In the remainder of the description, the same references are used to designate the same elements. Moreover, the various characteristics presented and/or claimed can advantageously be combined. Their presence in the description or in different dependent claims does not exclude this possibility.
As mentioned, the present invention may be considered, at least in certain aspects, as an improvement applicable to all methods of capturing molecules of interest integrating chemical absorption and regeneration. Indeed, the invention, as will be shown in the examples, allows a capture method that consumes less thermal energy than the methods described in the prior art and in particular a reduced energy requirement at the reboiler of the regeneration column.
A wide variety of technologies for capturing a molecule of interest integrating chemical absorption and regeneration have been proposed to prevent the release of CO2 or for its capture. However, chemical absorption requires energy to regenerate the CO2 loaded chemical absorbent. Often, the energy required to regenerate the chemical absorbent can give rise to a release of CO2, which still impairs the overall efficiency of the capture of the CO2 gas.
Thus, in the remainder of the description, the present invention will be detailed, in particular, for an application in which the molecule of interest is CO2 originating from a gaseous effluent, preferably an industrial effluent. However, by means of the teaching of the present invention, the person skilled in the art could apply it to other molecules of interest originating from other effluents.
For example, referring to
Inside the regeneration column 31, the hot flow of chemical absorbent loaded with CO2 53 is heated so as to cause the release of CO2 and the production of a hot flow of regenerated chemical absorbent 35 which is directed to the heat exchanger 50 and then the absorption column 20 in the form of a cold flow of regenerated chemical absorbent 52.
The gas flow containing the released CO2 37 is directed to a cooler 71, for example a water cooler, then to a water storage tank 72. While the gaseous part is directed towards a compressor 73, the liquid part is reinjected into the regeneration column 31. A series of coolers 71, water storage tank 72 and compressor 73 compresses the CO2 and removes some of the water. The final components of a known CO2 capture system are a dehydrator or dryer 75, such as a glycol scrubber (triethylene glycol, TEG), effective to obtain a water-free gas from a pressurised gas. The purified CO2 passes again through a compressor 73 so as to reach the transport or storage pressure (e.g., >100 bar).
Thus, a chemical absorbent-based CO2 capture system of the prior art combines elements for heating an effluent such as a reboiler 80 and elements for cooling an effluent such as coolers 71. In addition, it comprises numerous compressors 73 and at least one dehydrator or dryer 75. In particular, the recovered CO2 is compressed by four compressors in series with an intermediate cooling and a condenser between two compressors.
The energy efficiency of such a system is not optimal and a great deal of research and development have been carried out to increase the energy efficiency of such a system.
In an effort to solve this problem, the present disclosure provides both a method and a system for capturing a molecule of interest from gaseous effluents that reduce energy consumption while reducing design costs.
Thus, the present invention provides an arrangement and operating principle for capturing a molecule of interest (such as CO2) with, surprisingly, reduced energy consumption, which may present reductions of more than 30% compared with a conventional process and drying of the CO2 flow.
Conventionally, such a system comprises the capture of a molecule of interest in a gaseous effluent by means of a chemical absorbent in an absorption column 20. Moreover, in the context of the invention, the thermal regeneration of the chemical absorbent especially uses at least one regeneration section 30 and at least one condensation section 40.
Moreover, the invention comprises a compression of the molecule of interest released by the at least one regeneration section which is reinjected into the at least one condensation section, preferably at the bottom of the section, said condensation section being arranged to allow heat transfer to the regeneration column.
As illustrated in
The absorption column or columns 20 are arranged to allow the capture of CO2 by a chemical absorbent. It generally comprises one or more inlets, preferably at the bottom of the column, for a gaseous effluent 12 loaded with CO2, such as, especially, an industrial gaseous effluent.
It also comprises one or more inlets for a flow of chemical absorbent, preferably at the top of the column. When two flows of chemical absorbent enter the absorption column 20, a first can be positioned at the top of the column and a second in the lower half of the absorption column 20.
The absorption column also comprises one or more outlets for a flow of chemical absorbent 25 enriched in CO2, preferably at the bottom of the column. When two flows of enriched chemical absorbent leave the absorption column 20, a first can be positioned at the bottom of the column and a second in the upper half of the absorption column 20.
The absorption column also comprises one or more outlets for a gaseous effluent 21 depleted of CO2. This outlet for the CO2-depleted gaseous effluent 21 is preferably positioned at the top of the column. In addition, the system may comprise devices for treating this CO2-depleted gaseous effluent 21 not shown in the figures, such as devices for washing with water or for capturing any toxic compounds or compounds of interest of the CO2-depleted gaseous effluent 21.
As has been mentioned, a system 1 according to the invention is particularly suitable for the capture of CO2 by a chemical absorbent.
Many chemical solvents can be used to capture a molecule of interest and more particularly CO2 by chemical absorption. Preferably, the chemical absorbent is a chemical compound with a basic character. In fact, a chemical absorbent of basic character, that is to say comprising at least one basic function, will be capable of binding an acid molecule of interest, such as H2S or CO2, by formation of an acid/base bond. The chemical absorbent may, for example, comprise an amine function or a mixture of amine functions, ammonia, and/or a carbonate function.
The amines, or chemical absorbent carrying an amine function which can be used in the context of the present invention are especially primary amines (e.g., monoethanolamine (MEA) or diglycolamine (DGA) or 2-amino-2-methyl-1-propanol (AMP), secondary amines (e.g., diethanolamine (DEA) or diisopropyl amine (DIPA), tertiary amines (e.g., triethanolamine (TEA) or methyldiethanolamine (MDEA) or sterically hindered amines (e.g., 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD)).
As detailed in the examples, the performance of the present invention has been illustrated for the capture of CO2 by chemical absorption with monoethanolamine (MEA). In particular, CO2 from the gaseous effluent can be absorbed in a solution comprising MEA and water. MEA reacts with CO2 to form amine protonate, bicarbonate, and carbamate. Due to the high reaction enthalpy, amines generally absorb CO2 at rapid rates.
The chemical absorbent may contain ammonia and, in particular, ammonium carbonate.
The chemical absorbent may include potassium carbonate. An aqueous solution of potassium carbonate can be used both for the capture of carbon dioxide after combustion or in pre-combustion.
Moreover, the chemical absorbent according to the invention may comprise several compounds. For example, it may comprise piperazine, especially in combination with an amine or a potassium carbonate.
More generally, it may comprise at least two mixed amines (e.g., AMP+MEA) or one or more amines with potassium carbonate.
In order to limit the energy consumption necessary for the capture of CO2 by a chemical solvent, a chemical absorbent according to the invention may consist of a two-phase or demixing solvent. Such a two-phase demixing solvent preferably comprises two phases, for which one of the two phases is used to concentrate the captured CO2. Thus, in particular, the chemical absorbent exhibits a separation of liquid-liquid phases which is a function of the temperature and which facilitates the release of the molecule of interest (such as CO2) and the regeneration of the absorbent. Preferably, the chemical absorbent has a homogeneous phase at room temperature (for example below 30° C.) and a liquid-liquid phase separation at a temperature above 60° C.
More preferably, such a demixing solvent has the property of forming two immiscible liquid phases by absorption of CO2 under specific conditions of CO2 loading rate and/or temperature. Since the CO2 is concentrated in a liquid phase, only a fraction of the solvent must be sent to the regeneration section 30. The result is a decrease in the liquid flow to be regenerated. Thus, only the lower phase, rich in CO2, must be sent to the regeneration section 30. The upper phase poor in CO2 is returned directly to the top of absorption column 20 without specific treatment. For this purpose, a decanter can be positioned at the outlet of the absorption column 20, preferably at the outlet of the heat exchanger 50 described below, the increase in temperature favouring demixing.
The use of a demixing solvent makes it possible to reduce the volume to be treated during regeneration step 120 of the solvent or chemical absorbent loaded with CO2; this step is well known for being particularly energy-intensive and representing up to 70% of the costs of the entire gaseous effluent treatment chain. The use of such a solvent, known as a demixer, advantageously has a degradation rate, such as, for example, a loss of amine, of around 10% at a temperature of between 150° C. and 180° C. and at a pressure of 20 bar. Moreover, such a pressure advantageously makes it possible to facilitate the transport of the CO2 once the regeneration step 120 has been implemented.
A two-phase demixing solvent may, for example, comprise one or more amine functions, one or more piperidine groups, or even be formed from several different molecules.
As illustrated in
A flow of hot regenerated chemical absorbent 35 coming from the regeneration section 30 provides calories to a flow 25 of enriched chemical absorbent coming from the absorption column 20. Given that the release of CO2 by the enriched chemical absorbent is very endothermic, this makes it possible to improve the energy balance of the system by proposing a hot flow of chemical absorbent enriched with CO2 53 as soon as it enters the regeneration section 30. Conversely, CO2 capture is more efficient at low temperature and such a heat exchanger 50 allows a cooled regenerated chemical absorbent flow 52 at the inlet of the absorption column. These steps are endothermic for two reasons: chemical, because the chemical bond between the weak acid CO2 and an ethanolamine is an acid-base bond and therefore strong, and thermodynamic, because of the amount of water present in the liquid entering the regeneration column.
Such a heat exchanger 50 may take the form of a shell-and-tube heat exchanger, a plate-and-frame heat exchanger, a plate-fin heat exchanger or a microchannel heat exchanger. Shell-and-tube heat exchangers consist of a shell with tubes inside; plate-and-frame heat exchangers consist of a series of corrugated plates supported by a rigid frame; plate heat exchangers consist of side bars, fins and separator sheets; microchannel or printed circuit heat exchangers consist of stacked plates with fine grooves etched into each plate. Alternatively, the heat exchanger 60 may have a triply periodic minimal surface.
Moreover, as illustrated in
A regeneration section 30 according to the invention preferably corresponds to a zone of the system arranged to allow regeneration of the chemical absorbent, i.e., more precisely, the release or passage to the gaseous state of at least a part of the CO2 that was previously combined with the chemical absorbent. A particular feature of the system 1 according to the invention is that it makes it possible to break a chemical bond between the chemical absorbent and the CO2 when this requires a large supply of energy. Preferably, the CO2 capture system according to the invention comprises a single regeneration section 30.
A condensation section 40 according to the invention preferably corresponds to a zone of the system arranged to allow condensation of water while maintaining the CO2 in the gaseous state. That is to say, more precisely, the passage to the liquid state of at least part of the water associated with the CO2 which has been released at the regeneration section 30. Preferably, the CO2 capture system according to the invention comprises several condensation sections 40.
Moreover, the at least one condensation section 40 and the at least one regeneration section 30 are associated in such a way that a material transfer is possible simultaneously with the heat transfer. The system then improves heat exchange while maintaining material transfer performance. The material transfer performance makes it possible to efficiently separate the CO2 and vapour mixture from the regenerated chemical absorbent in the regeneration section and to efficiently separate the CO2 and water in the condensation section.
In particular, the at least one condensation section 40 and the at least one regeneration section 30 are arranged so that each of the fluids circulating in said sections is both in liquid phase and in gas phase, the liquid phase flowing in a direction opposite to the gas phase.
Preferably, the at least one regeneration section 30 and at least one condensation section 40 form an assembly of the heat integrated distillation column (HIDiC) type. In HIDiC type assemblies, a column is split into two columns: a depletion column and an enrichment column. Numerous designs for heat integrated distillation columns, called HIDiC columns, have been proposed for decades. One of the characteristics of an HIDiC column is that heat is transferred from a hot enrichment zone to a cooler depletion zone. In order to observe this situation, the enrichment zone is set to a higher pressure than the depletion zone. Nevertheless, in the current use of HIDiC type assemblies, the pressure jump to be performed is kept at a low level, otherwise the cost of recompression would become comparable to the cost of reboiling the bottom of the column 31. Thus, generally, the pressure jump in a HIDiC column is less than 2 bar, preferably less than one bar.
Thus, although the regeneration section 30 and the condensation section 40 have similarities with HIDiC columns. However, in the context of the present invention, it is essential that, contrary to the case of distillation columns of the HIDiC type, the pressure in at least one condensation section 40 is at least 1 bar higher, preferentially at least 2 bar, more preferentially at least 3 bar, even more preferentially at least five bar higher than the pressure in the at least one regeneration section 30. Thus, as shown in the examples, a conventional HIDiC type column for CO2 capture as applied for distillation operations would not have the same performance as the present invention.
As illustrated in
An inter-section heat exchanger 43 usable in the context of the present invention is advantageously a device arranged to allow heat transfer between the at least one condensation section 40 and the at least one regeneration section 30. More particularly, the heat transfer is carried out from a fluid passing through the at least one condensation section 40 to a fluid passing through the at least one regeneration section 30.
Thus, these sections operate according to a diabatic mechanism, i.e., under heat exchange control, between at least one condensation section 40 physically separated from at least one regeneration section 30.
An inter-section heat exchanger 43 which can be used in the context of the present invention may, for example, correspond to one or more common walls between a regeneration section and a condensation section, a tube heat exchanger, a shell-and-tube heat exchanger, a plate-and-frame heat exchanger, a plate-fin heat exchanger or a microchannel heat exchanger.
In addition, an inter-section heat exchanger 43 which can be used in the context of the present invention may take the form of a wall between the condensation section 40 and the regeneration section 30 combined with a packing which can be positioned on the side of the condensation section 40 and/or on the side of the regeneration section 30.
Thus, the condensation section 40 and the regeneration section 30 may each comprise a packing and this packing may be different according to the sections. The packings of the condensation section 40 and the regeneration section 30 may be fixed to a common wall between these two sections.
In particular, the packing may take the form of a thermally conductive alveolar three-dimensional structure. The packing may especially define a plurality of cells in communication with one another. The packing may have a stochastic structure or a regular structure. Thus, the arrangement of the cells may be regular or stochastic. The cells may be cylindrical, prismatic or parallelepipedal, for example. In particular, the packing may comprise Kelvin cells.
The packing may comprise or be constituted by a conductive foam, especially a foam constituted by a heat conductive material. For example, the foam may be a metal foam (e.g., copper, titanium, stainless steel or aluminium foam, or alloys thereof) or a silicon carbide foam.
The packing, as already mentioned, may be integrated both inside column 30 and inside column 40. The packing may have a surface area to volume of between 100 and 100,000 m2/m3. Preferably, the packing may have a surface area to volume greater than 1000 m2/m3, more preferably a surface area to volume greater than 10,000 m2/m3. Moreover, it may have a void ratio of between 85% and 99%. The packing can be manufactured by casting or by additive technology.
Advantageously, in one embodiment, the inter-section heat exchanger 43 may correspond, for example, to one or more common walls between a regeneration section and a condensation section. In particular, for this embodiment, the inter-section heat exchanger 43 will advantageously have a triply periodic minimal surface (TPMS).
A TPMS is defined as a surface of zero mean curvature, which means that the sum of the principal curvatures at each point is zero. Thus, a TPMS is a surface that minimises its surface with a fixed limit curve. Conventional examples of TPMS include the Schwarz surface, the gyroid surface and the diamond surface.
Advantageously, the inter-section heat exchanger 43 will comprise one or more TPMS dividing a three-dimensional domain (3D) into two separate but interpenetrating channels. This makes it possible to provide a large surface area to volume ratio.
Advantageously, the inter-section heat exchanger 43 will comprise one or more walls having a zero mean curvature at any point. Moreover, each separate channel may advantageously be interconnected in all directions. Therefore, the flow is free to move in any direction and the hydrodynamic resistance and pressure drop in the intersection heat exchanger 43 are limited.
The inter-section heat exchanger 43 can be manufactured by additive manufacturing as a complete part without welding or brazing.
The inter-section heat exchanger 43 may have a triply periodic minimal surface (TPMS) in other embodiments.
Advantageously, a condensation section 40 may be associated with a regeneration section 30 in the form of a one-piece assembly. Thus, the at least one condensation section 40 and the at least one regeneration section 30 can be arranged in the form of a one-piece integral assembly.
The one-piece assembly will comprise at least one condensation section 40 inseparable from a regeneration section 30. Moreover, it may include the inter-section heat exchanger 43.
A one-piece, preferably integral, assembly makes heat transfer more efficient. For example, in the presence of a packing established in continuity with the thermally conductive wall or walls, energy is more easily transferred from one section to another.
The one-piece assembly may be manufactured by additive manufacturing, brazing or welding of elemental metal plates or by one-piece casting.
The at least one regeneration section 30 and condensation section 40 may, for example, take the form of independent columns.
As shown in
Alternatively, the sections or columns may not be joined together but separated by an inter-section heat exchanger 43 for fluid management allowing heat to be transferred from a condensation section 40 to a regeneration section 30. For example, a regeneration section 30 may be coupled to a condensation section 40 by a network of heat exchangers of the fluid exchanger type, the fluid possibly being the fluid flowing through the condensation section 40. A heating fluid circulates in the exchanger network; it captures the heat from the condensation section and supplies it to the regeneration section.
In one embodiment, the regeneration section 30 and condensation section 40 are arranged concentrically. In particular, as illustrated in
The exchange surface and therefore the inter-section heat exchanger 43 can be limited to the wall between the two columns. Nevertheless, advantageously, the sections include fins or a packing to improve the heat transfer between the two sections. The packing or fins of the outer section (regeneration) are connected to the inner section (condensation) so that the vapour of the inner section can flow in contact with the packing or fins and condense there, and the liquid then falls into the inner section. The heat released during condensation of the vapour of the inner section releases the CO2 associated with the chemical absorbent of the outer section circulating on the packing or fins. Internal surfaces will not necessarily have the same geometry and will be conceptualised in such a way that changes in fluid flow rates on either side of the walls are taken into account. This equipment and these internal walls can be manufactured by existing casting methods or by additive manufacturing.
In particular, in the context of a concentric column arrangement, a first packing can fill the inside of the condensation section 40 and a second packing can follow the contour of the wall surrounding the condensation section 40 and extend radially into the regeneration section.
Such a system operating on the same principle could be envisaged with several tubular columns distributed homogeneously so as to maximise heat exchanges.
As illustrated in
As shown in
As illustrated in
As illustrated in
As illustrated in
In one embodiment, the at least one regeneration section 30 and condensation section 40 may be integrated into the same column. As illustrated in
In addition, as illustrated in
Thus, the system according to the invention can comprise regeneration and condensation sections arranged in the form of a column comprising a packing, in the form of a set of internal assemblies with periodic structure (of the TPMS-gyroid type) allowing an increased exchange surface but without contact between the phases on either side of the jackets. This scheme allows intensified heat exchanges and therefore a reduction in the size of the equipment as well as a minimisation of the pressure drop of the low pressure system.
As illustrated in
The system according to the invention may, in addition to one or more compressors 60, comprise expansion valves, for example installed at the level of the sections, to adjust the respective pressure levels in the two sections. In particular, the condensation section(s) 40 and/or regeneration section(s) 30 may especially be equipped with one or more expansion valves configured to adjust the respective pressure levels in the two sections.
In particular, a compressor 60 and therefore a compressor assembly 60 can be arranged to maintain a pressure in the at least one condensation section 40 that is at least 1 bar, 2 bar or 3 bar higher, preferentially at least 5 bar, more preferentially at least 10 bar, even more preferentially at least 15 bar higher than the pressure in the at least one regeneration section 30. The pressure difference thus established leads to a temperature difference between a condensation section 40 and a regeneration section 30 which offers the possibility of transferring heat between the two sections via an inter-section heat exchanger 43.
The compressor 60 can be selected from any type of compressor capable of establishing a pressure differential according to a ratio of at least 1:3 between the regeneration section 30 and the condensation section 40. Advantageously, the compressor 60 can be a compressor capable of establishing a pressure differential according to a ratio of at least 1:5 between the regeneration section 30 and condensation section 40, preferably at least 1:8. The compressor 60 may, for example, be a shock wave compressor.
As illustrated in
As illustrated in
In particular, a first compressor may be positioned at the outlet of a regeneration section 30 and a second compressor may be positioned at the outlet of a condensation section 40 as shown in
Several compressors can also be positioned at the outlet of several regeneration sections 30 and a second compressor can be positioned at the outlet of a condensation section 40 as shown in
Advantageously, the system will comprise a plurality of compressors 60, 60b, making it possible, for example through several successive compressions, to reach a pressure of at least 3 bar, preferentially at least 10 bar, more preferentially at least 30 bar, and even more preferentially at least 100 bar for the gas mixture comprising CO2 passing through a section capable of carrying out heat exchange with at least one condensation section 40 and/or at least one regeneration section 30. In this case, taking into account the high pressures in the last compression phase (for example more than 50 bar), the water content in the gas phase will be zero or almost zero. The drying unit will therefore be unnecessary, which represents a significant capital gain.
The system 1 according to the invention is particularly suitable for its installation on industrial plants producing a gaseous effluent comprising CO2. Indeed, it will be able to enable CO2 capture and storage with improved energy efficiency.
Thus, according to another aspect, the invention also relates to an industrial plant producing a gaseous effluent comprising CO2 and equipped with a CO2 capture system 1 according to the invention.
For example, the industrial power plant may be a fossil fuel-based energy plant, a steel-making plant, a biomass-based energy plant, a natural gas processing plant, a synthetic-fuel plant, a refinery, a petrochemical production plant, a cement plant, or a fossil fuel-based hydrogen production plant.
According to another aspect, the invention also relates to a method 100 for capturing a molecule of interest contained in a gaseous effluent, preferably an industrial gaseous effluent. Such a method for capturing a molecule of interest can implement a system 1 for capturing a molecule of interest according to the invention or any other suitable system. In particular, the invention relates to a method 100 for capturing CO2 contained in an industrial gaseous effluent which can be used in a CO2 capture system 1 according to the invention or any other suitable system. As previously, a method according to the invention will be illustrated in the context of a capture of CO2.
As illustrated in
During the CO2 capture step 110, industrial gaseous effluents containing carbon dioxide are introduced into the lower part of an absorption column 20, and the chemical absorbent is introduced from the upper part of the absorption column 20. The gaseous effluent and the chemical absorbent therefore flow counter-currently to each other in the absorption column 20. As it comes into contact with the liquid chemical absorbent, carbon dioxide is absorbed by the chemical absorbent. The exhaust gas from which the carbon dioxide has been removed is evacuated towards the upper part of the absorption tower 10, and a chemical absorbent rich in carbon dioxide is evacuated towards a regeneration section 30 or a heat exchanger 50.
Following the regeneration step 120, the method may comprise a step of heating the liquid formed in the at least one regeneration section 30. This heating is carried out by a conventional reboiler 80, via microwave irradiation, solar energy or an electrical resistance.
As has already been mentioned, the CO2 capture method 100 according to the invention has the particular feature of using at least one regeneration section 30 and at least one condensation section 40. In particular, in the context of a method according to the invention, the regeneration step 120 is implemented in at least one regeneration section 30. The condensation step 150 is implemented in at least one condensation section 40.
The regeneration section 30 may have a temperature at the top of the column preferably comprised between 60° C. and 150° C.
A condensation section 40 may have a temperature at the top of the column at least equal to 90° C., preferably at least equal to 100° C. In the case of several condensation sections 40, the sections may have different operating temperatures.
In addition, the method according to the invention comprises a step 130 of compressing the gas mixture comprising a solvent and a molecule of interest (e.g., water and CO2) upstream of the condensation section 40. This compression step 130 can be carried out by any compressor and possibly by a combination of compressors (i.e., the compression step then comprising successive compression).
Such a compression step is advantageously carried out so that the pressure in the at least one condensation section 40 is at least 2 bar higher than the pressure in the at least one regeneration section 30. As has been mentioned, the pressure jumps are usually smaller and they do not make it possible to achieve the performances obtained with the present invention. Preferably, the compression step 130 makes it possible to create a pressure jump between the at least one regeneration section 30 and the at least one condensation section 40 at least equal to 2.5 bar, preferably at least equal to 3 bar, more preferably at least equal to 5 bar and even more preferably at least equal to 8 bar. This recompression of the gas mixture makes it possible, in the context of diabatic operation, to significantly improve the energy efficiency and, in particular, to reduce the energy input to the reboiler 80. Moreover, by integrating directly into the regeneration step a part of the recompression that normally takes place exclusively downstream of this step, a simplification takes place (fewer steps for the same result).
Following the step 130 of compressing the gas mixture comprising water and CO2, the pressure in the at least one condensation section 40 is at least equal to 3 bar, preferably at least equal to 10 bar, more preferably at least equal to 15 bar, and even more preferably at least equal to 30 bar.
As illustrated in
In particular, a method implemented according to the present invention could, in the presence of a pressure jump of 15 bar, require an energy consumption of the reboiler of 64 MW. This is a 30% gain compared to a typical consumption of 91 MW, without taking into account the reduced need for dehydrator or dryer.
In particular, the compression step 130 may comprise the injection of the compressed gas mixture into the condensation section, preferably at the bottom of the section.
The velocity of the gas phase in the at least one regeneration section may, for example, be between 0.5 m/s and 5 m/s, preferably between 1 m/s and 3 m/s.
The velocity of the gas phase in the at least one condensation section may, for example, be between 0.5 m/s and 5 m/s, preferably between 1 m/s and 3 m/s.
Such a method allows moderate recompression of the vapour (from the regeneration section to the condensation section) and diabatic operation of all or some of the columns (heat going from the condensation section 40 to the regeneration section 30).
As has already been said, this makes it possible to reduce the energy input to the reboiler 80 and energy gains of around 20% to 30% are expected. Moreover, by integrating directly in connection with the regeneration step a part of the recompression that normally takes place exclusively downstream of this step, a simplification of the method takes place (fewer steps for the same result). This integration makes it possible to reduce the elementary steps of the original method, which results in greater operational gains for the new configuration.
In addition, the method comprises a heat transfer step 140 between the at least one condensation section 40 and the at least one regeneration section 30. The heat transfer 140 may use different heat exchangers described above.
In particular, this step allows heat to be transferred from the at least one condensation section 40 to the at least one regeneration section 30. In other words, it allows the regeneration section 30 to be heated from the heat contained in the condensation section 40 and more particularly from the heat generated during the compression step 130.
The heat transfer step advantageously makes it possible to set up a temperature gradient within each of the regeneration and condensation sections. Given the presence of a temperature gradient within each of the regeneration and condensation sections, in each section, the fluid may be present in two states: the liquid state and the gaseous state. The liquid phase of a fluid will generally flow counter-currently to the gas phase of said fluid.
The heat transfer step can be controlled so as to induce a temperature difference of at least 3° C., preferably at least 5° C., more preferably at least 10° C. between a section inlet and a section outlet. The smaller the temperature difference between the section inlet and the section outlet, the greater the energy gain.
In particular, considering this heat transfer step 140, the gas mixture, comprising water vapour and CO2, may, in contact with walls cooled by the heat exchange in the direction of the regeneration section 30, be divided into water passing into the liquid state in contact with the wall and into CO2 remaining in the gaseous state. The water, in the liquid state, then trickles onto the solid surfaces while the CO2 occupies the rest of the structure and leaves the condensation section.
Thus, the method comprises a condensation step 150 allowing the formation of water in the liquid state and a gas mixture enriched in CO2.
Advantageously, the gas mixture enriched in CO2 will comprise a very small quantity of water.
Table 1 below shows performances that can be achieved by means of the present invention.
In addition to the energy gains, the present invention may allow better dehydration efficiency and better capture efficiency as a function of the pressure differential applied.
Thus, the present invention makes it possible, by a simplified system, to greatly reduce the heat demand to be supplied to the regeneration step of the chemical absorbent and to produce a gas at the top of the condensation section having a lower water content than the methods used in the usual regeneration columns.
As a result, in addition to energy savings, the method could make it possible to reduce or eliminate the need for equipment such as pumps and system for treating cooling water of the condensation circuit, condensers at the top of the column and also, in some configurations, dehydrator and dryer downstream of the condenser.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2020/052626 | 12/24/2020 | WO |
