ES2387791A1 - Method for capturing co2 - Google Patents

Abstract

The present invention relates to a method for the capture of CO2 in a tube exchanger with amino-alcohol-impregnated alumina supports under combined conditions of TSA, PSA and vapour entrainment and subsequent reconditioning of the sorbent.

Description

CO2 capture procedure ..

The present invention relates to a process for the capture of CO2, in a gas treatment circuit in fixed-bed reactors with alumina supports impregnated with amino alcohols, under conditions of TSA, PSA and steam entrainment combined.

STATE OF THE PREVIOUS TECHNIQUE

Currently, all post-combustion CO2 capture plants use procedures based on chemical absorption with an aqueous solvent of alkanolamine, monoethanolamine (MEA) and diethanolamine (DEA) are the most frequent solvents. However, they have numerous drawbacks for treating gaseous streams, including the large amount of heat required to regenerate the solvent and the operating problems caused by corrosion and chemical degradation, which result in high capital costs and functioning. In total, 75–80% of the capture and sequestration cost of 90% of the CO2 from an electric power production plant is attributable to the capture and compression stage. It is therefore crucial to develop means of capturing CO2 at low cost to sequester CO2 emissions on an industrial scale.

It is considered that chemical absorption in regenerable solid sorbents is one of the most promising technologies to capture CO2 from gaseous streams, because it would allow a reduction in energy consumption, the heat capacity and regeneration temperature of the sorbent could be reduced solid.

Recently, it has been described about regenerable sorbents based on substrates for the capture of CO2 after combustion in gaseous streams from electric power plants fueled with fossil fuels. Several different methods have been used to synthesize solid chemosorbents for CO2 capture [WO2009 / 061470]. The use of grafted amines or polyamines on a nano-sized solid support to improve some characteristics of the gaseous sorbents in the solid phase is also described. For example, a procedure for creating CO2 chemosorbents is based on the insertion of amine groups into nanostructured mesoporous silica supports [US 5087597].

An additional hypothesis has also been proposed, called "molecular envelope" (or "molecular basket" in English) in which nanostructured mesoporous silicas are used, where porous nanosilica support material is used, with a large pore volume for the purpose. to obtain a high adsorption capacity while to increase the selectivity and affinity of the adsorbent for CO2, polyamines are introduced into the pores, which have a high affinity for CO2 [US 7795175].

Other materials recently used to trap carbon dioxide are metalorganic reticular materials (MOF). MOFs are nanocrystalline structures composed of organic and inorganic components arranged in a crystalline network structure. These structures are constructed using an ionic metal core or axis, to which organic ligands bind. The lengths of the organic ligands define the volume of the gaps, the diameter of the pores of the crystalline lattice, and the geometry of the gap. The physical adsorption capacity and the selectivity of the MOF depend on these parameters. Organometallic skeletons are more suitable for pressure swing adsorption (PSA) with a loading pressure (15/40 bar, 1500/4000 kPa) and atmospheric pressure desorption. MOFs with uncoordinated amine functionalities inside the pores have also been prepared in an effort to improve yields in the application of the chemosorption process and temperature oscillation adsorption (TSA).

All the aforementioned materials require complex syntheses, and their production on an industrial scale is expensive. Considering that the application for the capture of CO2 in an electric power plant requires large quantities of materials, cheap and simple preparation methodologies would be necessary to prepare solid sorbents.

Regardless of the typology of the materials used, a critical aspect refers to the definition of a suitable procedure for the capture of post-combustion CO2 by solid sorbents in an electric power plant. For an efficient recovery of CO2, a large amount of solid sorbent must be used in a process that provides a low pressure drop and easy regeneration of the sorbent, due to a high concentration of CO2 and the flow of the gaseous streams of the plant. electric power.

The typology of the CO2 capture procedure with solid sorbent depends on the particle size of the material used. In the case of using sorbents in the form of a powder, a high pressure drop is generated which means that a fluidized bed is needed, in this case, the procedure normally used is a gas washing equipment, of a fluidized bed in circulation, with a part of the sorbent transported by the same gas flow in a separate device where the sorbent is regenerated by heating it and then cooled and recirculated in the absorber.

On the other hand, when a sorbent in the form of granules is used, a lower pressure drop is generated and in this case a fixed bed procedure would be employed. However, in order to carry out the regeneration step, a mobile bed is usually used for the use of granules, where the sorbent is continuously recirculated between the absorber and the desorber to provide a continuous supply of regenerated material.

Both procedural solutions, both fluidized bed and mobile bed, have drawbacks with respect to a fixed bed: the fluidized bed and the mobile bed have a lower capture efficiency than the fixed bed and cause a loss of mass of friction sorbent and / or abrasion. In addition, diffusion outwards from the porosity of the solid of the CO2 released, from the sorbent during regeneration, could not occur spontaneously only due to the increase in temperature and then steam entrainment and / or vacuum depressurization should also be applied. The need for gas entrainment and / or use of vacuum makes it more difficult to work with procedures based on a fluid or moving bed.

DESCRIPTION OF THE INVENTION

The present invention provides a method for capturing CO2 comprising a gas stream treatment circuit, using fixed-bed reactors under conditions of TSA (temperature oscillation absorption), PSA (pressure oscillation absorption) and steam entrainment combined.

One aspect of the present invention relates to a CO2 capture process in a gas stream treatment circuit, in at least two fixed-bed reactors (from now on the process of the invention), which comprises the steps:

a) CO2 absorption from the gas stream, at a temperature between 20 and 60 ° C (TSA conditions). Fixed bed reactors have a sorbent in which CO2 is to be absorbed. This stage of CO2 absorption is an exothermic chemo-absorption, so the reactors can be cooled to achieve a more efficient CO2 capture and lengthen the absorption time,

b) desorption of CO2 at a temperature between 60 and 120 ° C, a pressure between 0.08 and 0.8 atm and a steam flow rate of between 5 and 25% by volume of the desorbed CO2 (combination of TSA conditions , PSA and gas drag). At this stage the regeneration of the sorbent occurs when the saturation capacity of the CO2 is reached, and

c) reconditioning of the sorbent at a temperature between 20 and 60 ° C.

The process of the invention is a discontinuous process based on a gas treatment circuit, however, since the fixed bed reactors are working alternately as an absorption or desorption device, controlling the relationship between the flow rate and the conditions of each stage. of the procedure, the absorption and desorption times can be temporarily coupled so that they are similar, obtaining a continuous CO2 capture process. This optimization of the times reduces the number of reactors necessary for the capture of CO2. In a preferred embodiment in the process of the invention, desorption times can be matched to absorption times thanks to the combination of TSA, PSA and steam entrainment.

The entrainment gas may be any gas known to a person skilled in the art, although water vapor or nitrogen is preferably used.

In another embodiment the process of the invention comprises three fixed bed reactors.

Fixed bed reactors have the advantage that they are more efficient, easier to operate and optimize.

Preferably, the fixed bed of the reactors comprises a pelletilized alumina sorbent impregnated with at least one amino alcohol. More preferably, the amino alcohol is selected from diethanolamine (DEA), monoethanolamine (MEA), diglylamine (DGA), diisopropanolamine (DIPA), methyldiethanolamine (MDEA), triethanolamine (TEA) or any combination thereof. More preferably, the amino alcohol is diethanolamine. More preferably, the amino alcohol content is between 30 and 40% by weight with respect to the total sorbent.

By "pelletilized alumina" in the present invention is meant that alumina solid finely divided into powder, which has been transformed into larger particles and of a stable nature at temperature, humidity and mechanical pressure.

In a preferred embodiment, the temperature and pressure control of steps (a), (b) and (c) is carried out by heat exchangers containing finned tubes. In a more preferred embodiment the finned tubes are made of aluminum with tubular geometry. (See figures 1 and 2).

In a preferred embodiment the heat exchanger used in the process of the invention is characterized in that it comprises:

-

a tube (1) for the circulation of the thermal fluid comprising longitudinal radial fins (2) and an internal cavity (4) through which a thermal fluid circulates,

-

a wall that wraps the free ends of the radial fins, comprising the wall, an internal wall (6), an external wall (5) and an insulating jacket between them (7)

the tube, the fins and the inner wall being configured so that between them a solid pelletized sorbent (3) is located through which the gas containing the CO2 flows. More preferably, the heat exchanger further comprises a thermocouple (8) for measuring the process temperature.

In this way the design of the exchanger is such that there is no direct contact between the sorbent and the thermal fluids of the heat exchanger (see Figure 3). This prevents degradation of the sorbent, since it has impregnated amino alcohols. An embodiment of the heat exchanger is illustrated by way of example and without limitation of the invention in Figure 3.

With this alumina sorbent impregnated with amino alcohol, the process of the invention has a high selectivity and CO2 absorption capacity.

The thermal fluid that flows inside the tube provided with fins of the heat exchanger, can heat (or cool) by conduction the sorbent placed in the cavities between said fins, as illustrated in Figures 2 and

3 . Also the tube bundle can have a stream of cooling water in the absorption mode, and by condensation steam in desorption mode. Any other thermal fluid known to any person skilled in the art can also be used.

In a preferred embodiment the absorption of step (a) is carried out at a temperature between 35 and 45 ° C.

In another preferred embodiment the desorption of step (b) is carried out at a temperature between 80 and 90 ° C.

Preferably the desorption of step (b) is carried out at a pressure of 0.1 atm.

In another preferred embodiment the reconditioning step (c) is carried out at a temperature between 35 to 45 ° C.

In a preferred embodiment, the process of the invention has a CO2 absorption capacity greater than 90%.

The process of the present invention can be used to capture carbon dioxide from a coal power plant.

Another aspect of the invention relates to the heat exchanger for carrying out the process of the invention characterized in that it comprises:

-

a tube (1) for the circulation of the thermal fluid comprising longitudinal radial fins (2) and an internal cavity (4) through which a thermal fluid circulates,

-

a wall that wraps the free ends of the radial fins, comprising the wall, an internal wall (6), an external wall (5) and an insulating jacket between them (7)

the tube, the fins and the inner wall being configured so that between them a solid pelletized sorbent (3) is located through which the gas containing the CO2 flows

In a preferred embodiment, the heat exchanger further comprises a thermocouple (8) for measuring the process temperature.

Throughout the description and the claims the word "comprises" and its variants are not intended to exclude other technical characteristics, additives, components or steps. For those skilled in the art, other objects, advantages and features of the invention will be derived partly from the description and partly from the practice of the invention. The following examples and drawings are provided by way of illustration, and are not intended to be limiting of the present invention.

DESCRIPTION OF THE FIGURES

Fig. 1. Shows the view of the cross section (a) and the external surface (b) of the finned tube contained in the heat exchanger.

Fig. 2. Shows the horizontal section of the heat exchanger that contains the finned tube.

Fig. 3. Shows the diagram of the vertical section of the heat exchanger.

Fig. 4. Shows the CO2 absorption curve over time, with a sorbent of 630 g of alumina impregnated with 36% by weight of alumina.

EXAMPLES

The invention will now be illustrated by tests carried out by the inventors, which demonstrates the specificity and effectiveness of the process of the invention for the capture of CO2.

In order to carry out laboratory tests that evaluate the effectiveness of the post-combustion CO2 capture procedure based on solid sorbents, a specifically manufactured prototype has been used that simulates a sub-sector of industrial equipment. The reactor, which reproduces on a laboratory scale a geometry similar to that proposed for the actual application, allows to analyze the mechanism of heat and mass exchange, as well as the absorption / desorption phenomena inside the solid sorbent.

The device was designed similarly to a tubular heat exchanger (1000 mm long, ID 50 mm, constituted by a jacketed cylindrical vessel inside which is housed a tube equipped with extruded aluminum fins with external fins that if extended radially along the length of the entire length with up to providing a more efficient heat exchange In Figure 1a and b, the section and the external surface of the finned tube used in the realization of the fixed bed reactor can be observed respectively. Figure 2 shows in detail the horizontal section of the heat exchanger constituted by an aluminum tube (1) longitudinally provided with fins (2) and covered by an internal wall (6) and an external wall (5), between which there is a jacket (7) The thermal fluid flows both through the cavity of the finned tube (4) and through the outer jacket of the heat exchanger (7) The free space between the fins Longitudinal is filled by the solid pelletized sorbent (3) through which the gas containing CO2 flows

Figure 3 describes the vertical cross-section of the exchanger where the same elements described in Figure 2 are present. Figure 3 shows the inlet and outlet of the gas stream and the thermal fluid used as a heat exchange medium. The fluid used as a means of heat exchange is water which flows through the interior of the tube fitted with fins and the outer jacket, thus not directly in contact with the sorbent.

Depending on whether the thermal fluid is heated or cooling the fixed bed, the device will be able to function alternately and sequentially as a CO2 absorber or desorber. The thermal fluid that flows through the inside of the finned tube, heats (or cools) the conductive sorbent placed in the cavities between the fins and externally delimited by the wall of the internal unit surrounding the finned tube. In addition, to ensure the improvement of heat exchange by conduction with the sorbent, the reactor is also provided with an outer jacket through which the flow of the thermal fluid that leaves the tube provided with fins is transported, so that it is a heat exchanger. hot.

The temperature control of the thermal fluid is carried out by means of a cooled / heated recirculation bath for the control of the external temperature. The temperature of the sorbent bed is measured by thermocouples (8) directly in contact with the sorbent granules and placed in the upper, intermediate and lower part of the reactor as seen in Figure 3.

The fixed bed reactors were loaded with a bed of solid sorbent (spherical alumina granules impregnated with 36% by weight of diethanolamine) and fed with simulated gas streams.

In the CO2 absorption experiment, the test conditions were as follows:

 Composition of the gas inlet (v / v): CO2 = 10%; O2 = 3% v / v; H2O = 10% v / v; SO2 = 50 ppm; NO = 50 ppm; N2 = up to 100%;

 Amount of sorbents: 630 g;

 Flow rate: 300 Nl / h;

 Absorption temperature: 40 ° C

The desorption stage was carried out under the following conditions:

 Desorption temperature: 85 ° C

 Pressure: 100 mbar (10,000 kPa)

 Drag gas flow (N2): 0.6 Nl / h;

The performance of the procedure has been evaluated by measuring the “net CO2 capture capacity” and the “useful absorption time”, defined respectively as the amount of CO2 absorbed per gram of sorbent and the time until the CO2 concentration at the outlet of the reactor it remains less than 1% in volume during an absorption cycle (that is, until the fixed bed reactor allows 90% CO2 capture efficiency compared to its content in the feed which is of a 10%)

Figure 4 shows the curve corresponding to the concentration of CO2 output recorded during an absorption cycle.

Under the conditions tested, a "net CO2 capture capacity" of 50 mg CO2 / g of sorbent and a "useful absorption time" of more than 30 minutes have been measured. A complete regeneration of the sorbent can be obtained in a time equal to 30 minutes operating at 85 ° C, 10,000 kPa and with 0.6 Nl / h of N2 flow as entrainment gas. In addition, consecutive adsorption-desorption cycles were repeated hundreds of times using the same sorbent without any loss in its absorption capacity.

The experimental results showed that the process of the invention based on the fixed bed reactor heat exchanger is suitable for application to the capture of CO2 because it allows to quickly achieve the temperatures at which the sorbent operates in the absorption stages and regeneration, an effective CO2 capture and a complete regenerability of the sorbent. Additionally, thanks to the same duration of the absorption and regeneration stages, the continuous process can be easily carried out by means of a limited number of reactors operating alternately and therefore as an adsorption or desorption device.

Evaluation of the advantages of the proposed procedure

Based on the results obtained, the energy expenditure of the proposed post-combustion CO2 capture procedure using solid sorbents has been evaluated and the possible energy savings with respect to commercial technology based on the aqueous solution have also been estimated. of amines

To this end, the incidence of post-combustion CO2 capture on the electrical efficiency of the plant and on the net energy produced for a plant has been evaluated through a computer simulation program for an electric power production plant. of typical 660 MWe electric power powered by pulverized coal. In all the simulations carried out, a 90% CO2 capture from the gas stream has been taken as a reference.

The simulations of the plant were carried out in reference to the conventional plant (without CO2 capture), and for the following configurations:

the same electric power production plant associated with a conventional CO2 capture by MEA in aqueous solution;

the same plant working with a capture system based on the process of the invention with solid aminated sorbent for CO2.

Table 1 below summarizes the main results.

Table 1-Modeling results:

Case

Drag evaporator Tregen. (° C) Pregen. (KPa) Msorbent (Kg / kgCO2) Qregen. (KJ / kgCO2) W vacuum (MW) Wcompres (MW) Wneto (MW) C (LHV) (%)

No CO2 capture

---- ----- ----- ----- ----- ---- ----- 657.5 43.0

CO2 capture with MEA in solution

--- 120 ----- 17 3605 --- 48.5 475.6 31.1

CO2 capture with the process of the invention with solid sorbent

yes 85 10,000 twenty 2359 29.2 47.4 532.2 34.8

As shown in Table 1, the post-combustion CO2 capture procedure proposed by the inventors that uses solid sorbent saves more energy than one that uses aqueous monoethanolamine solution, which is potentially capable of saving 3.7 percentage points of net efficiency of the plant.

Claims (16)

one.

Procedure for capturing CO2, in at least two fixed-bed reactors, comprising the steps: a) CO2 absorption, from a gaseous stream, at a temperature between 20 and 60 ° C, b) CO2 desorption at a temperature of between 60 and 120 ° C, a pressure between 0.08 and 0.8 atm and a

Vapor flow rate of between 5 and 25% by volume with respect to the flow of desorbed CO2. c) reconditioning of the sorbent at a temperature between 20 and 60 ° C.

2.

Method according to claim 1 comprising three fixed bed reactors.

3.

Method according to any one of claims 1 or 2, wherein the fixed bed of the reactors comprises a pelletilized alumina sorbent impregnated with at least one amino alcohol.

Four.

Process according to claim 3, wherein the amino alcohol is selected from diethanolamine, monoethanolamine, diglylamine, diisopropanolamine, methyldiethanolamine, triethanolamine or any combination thereof.

5.

Method according to claim 4, wherein the amino alcohol is diethanolamine.

6.

Process according to any of claims 3 to 5, wherein the amino alcohol content is between 30 to 40% by weight with respect to the total sorbent.

7.

Process according to any one of claims 1 to 6, wherein the temperature and pressure control of steps (a), (b) and (c) is carried out by heat exchangers.

8.

Method according to claim 7, wherein the heat exchanger is made of aluminum with tubular geometry.

9.

Method according to any one of claims 1 to 8, wherein the heat exchanger is characterized in that it comprises:

-

a tube (1) for the circulation of the thermal fluid comprising longitudinal radial fins (2) and an internal cavity (4) through which a thermal fluid circulates,

-

a wall that wraps the free ends of the radial fins, comprising the wall, an internal wall (6), an external wall (5) and an insulating jacket between them (7)

the tube, the fins and the inner wall being configured so that between them a solid pelletized sorbent (3) is located through which the gas containing the CO2 flows.

10.

 Method according to claim 9, wherein the heat exchanger further comprises a thermocouple (8).

eleven.

Process according to any one of claims 1 to 10, wherein the absorption of step (a) is carried out at a temperature between 35 and 45 ° C.

12.

Process according to any one of claims 1 to 11, wherein the desorption of step (b) is carried out at a temperature between 80 and 90 ° C, a pressure between 0.1 and 0.3 atm and a steam flow rate of between 5 and 15% by volume with respect to the flow of desorbed CO2.

13.

Process according to any one of claims 1 to 12, wherein the reconditioning step (c) is carried out at a temperature between 35 to 45 ° C.

14.

Heat exchanger for carrying out the process according to any of the preceding claims characterized in that it comprises:

-

a tube (1) for the circulation of the thermal fluid comprising longitudinal radial fins (2) and an internal cavity (4) through which a thermal fluid circulates,

-

a wall that wraps the free ends of the radial fins, comprising the wall, an internal wall (6), an external wall (5) and an insulating jacket between them (7)

the tube, the fins and the inner wall being configured so that between them a solid pelletized sorbent (3) is located through which the gas containing the CO2 flows 15. Heat exchanger according to claim 14 further comprising a thermocouple (8).  (a) (b) FIG. one FIG. 2 FIG. 3  t -sec- FIG. 4 SPANISH OFFICE OF THE PATENTS AND BRAND Application no .: 201130296 SPAIN Date of submission of the application: 04.03.2011 Priority Date: REPORT ON THE STATE OF THE TECHNIQUE 51 Int. Cl. See Additional Sheet RELEVANT DOCUMENTS

Category

@ Documents cited Rei> indications affect

TO

WO 9817388 A1 (UNITED TECHNOLOGIES CORP) 30.04.1998, p. 3, lines 18-19; P. 4, 1-15

lines 3-5, 24-26; P. 4, lines 14, 18; P. 8

TO

US 2009 145297 A1 (ALSTOM TECHNOLOGY LTD) 11.06.2009, paragraphs [0031] - [0044]. 1-15

TO

WO 2010094923 A2 (ORIGO IND LTD; HOUSTON IAN) 26.08.2010, page 1-8, 11. 1-15

TO

WO 2008021700 A1 (UNIV SOUTHERN CALIFORNIA ET AL) 21.02.2008, p. 5, lines 10-20; 1-15

P. 8, line 6; P. 10, line 23.

TO

EP 1332783 A1 (HAMILTON SUNDSTRAND CORP) 06.08.2003, paragraphs [0007] - [0011], [0018] 1-15

[0023]

TO

US 7288136 B1 (US OF AMERICA DEPT OF ENERGY) 30.10.2007, column 3, lines 30-55; 1-15

column 4, lines 30-31; column 6, lines 5-8, 65-55; column 7, lines 5-28.

Category of the documents cited X: of particular relevance Y: of particular relevance combined with other / s of the same category A: reflects the state of the art O: refers to unwritten disclosure P: published between the priority date and the date of priority submission of the application E: previous document, but published after the date of submission of the application

This report has been carried out • for all claims • for claims no:

Date 'and realization' the report 24.05.2012

Examiner'or I. González Balseyro Page 1/4

REPORT OF THE STATE OF THE TECHNIQUE Application number: 201130296 CLASSIFICATION OBJECT OF THE APPLICATION B01D53 / 62 (2006.01) B01D53 / 14 (2006.01) B01D53 / 82 (2006.01) B01J20 / 22 (2006.01) B01J20 / 08 (2006.01) F28F1 / 10 (2006.01) F28D7 / 10 (2006.01) Minimum documentation sought (classification system followed by classification symbols) B01D, B01J, F28F, F28D Electronic databases consulted during the search (name of the database and, if possible, search terms used) INVENES, EPODOC, WPI, TXT, XPESP State of the Art Report Page 2/4  WRITTEN OPINION Application number: 201130296 Date of the Written Opinion: 24.05.2012 Statement

No> e'a '-Art. .1 LP 11 "198 -

Claims Claims 1-15 IF NOT

Acti> i'a 'in> enti> a -Art. 8.1 LP11 "198 -

Claims Claims 1-15 IF NOT

The application is considered to comply with the industrial application requirement. This requirement was evaluated during the formal and technical examination phase of the application (Article 31.2 Law 11/1986).  Base 'e Opinion.- This opinion has been made on the basis of the patent application as published. State of the Art Report Page 3/4  WRITTEN OPINION Application number: 201130296  1. Documents considered.- The documents belonging to the state of the art taken into consideration for the realization of this opinion are listed below.

Document

Publication or Identification Number Publication Date

D01

WO 9817388 A1 (UNITED TECHNOLOGIES CORP) 04/30/1999

D02

US 2009 145297 A1 (ALSTOM TECHNOLOGY LTD) 06.11.2009

D03

WO 2010094923 A2 (ORIGO IND LTD; HOUSTON IAN) 26.08.2010

D04

WO 2008021700 A1 (UNIV SOUTHERN CALIFORNIA et al) 02.22.2008

 2. Motivational declaration according to articles 29. � 29.� 'the Regulation' to execute '' Le 11 '198' e 2 '' e March� 'e Patents on non> e'a '� the acti> i'a' in> enti> a� citations � explanations in support of this eclaration The object of the invention is a process for capturing carbon dioxide by absorbing it on a fixed bed and desorption with steam entrainment; as well as the exchanger to carry out this procedure. Document D01 discloses a CO2 absorption procedure on fixed beds of alumina impregnated with 35-75% by weight of DEA. The regeneration of the sorbent is carried out by heating (30-50 ° C), pressure reduction and / or gas scanning. (See page 3, lines 18-19; page 4, lines 3-5, 24-26; page 4, lines 14, 18; page 8). Document D02 discloses a carbon dioxide absorption process on a fixed bed of a porous material impregnated in DEA, the regeneration thereof being carried out by heating at 35-140 ° C, reducing the pressure and / or with steam scanning. (See paragraphs [0031] - [0044]). Document D03 discloses a process of absorption of carbon dioxide on a porous substrate impregnated with amine (for example diethanolamine), said absorption being carried out at 15-70 ° C. The regeneration of the sorbent, or desorption of CO2, is carried out at 40-120 ° C by means of an acid treatment. (See page 1-8, 11). Document D04 discloses a CO2 absorption process at 0-100 ° C by using an amine (which may be DEA) on a support of a nanostructured material. Desorption or regeneration of the sorbent can be carried out by heating at 25-120 ° C, reducing the pressure, vacuuming, purging with gas or combining some of said techniques. (See page 5, lines 10-20; page 8, line 6; page 10, line 23). None of the aforementioned documents D01-D04 or any relevant combination thereof discloses a process for capturing carbon dioxide under the conditions set forth in claim 1 of the application, much less the sorbent being composed of a pelletized alumina support. Likewise, none of the aforementioned documents D01-D04 discloses a heat exchanger with the characteristics defined in claim 14 which allows to reach the conditions of absorption and desorption of CO2 therein, according to the moment of the process in which it is located. Consequently, the invention as set forth in claims 1-15 meets the requirements of novelty and inventive activity, as set forth in Articles 6.1 and 8.1 of the Patent Law. State of the Art Report Page 4/4