Temperature-swing adsorption process

Abstract

A temperature swing adsorption process for removing a target component from a gaseous mixture, the process being carried out in a plurality of reactors, wherein each reactor performs: (a) adsorption of the target component providing a loaded adsorbent and a waste stream; (b) heating of the loaded adsorbent and desorption of target component, providing an output stream; (c) cooling of the adsorbent; a rinse step (a1) before the heating (b), wherein the loaded adsorbent is contacted with a rinse stream containing the target component, producing a purge stream depleted of the target component; a purge step (b1) before the cooling (c), wherein the adsorbent is contacted with the purge stream provided by another reactor while performing the rinse step (a1), thus producing an output stream containing the target component, wherein the rinse stream comprises at least a portion of the output stream provided by another reactor while performing the purge step (b1).

Claims

1. A temperature swing adsorption process for removing a target component from a gaseous mixture containing at least one side component besides the target component, said temperature swing adsorption process being carried out in a plurality of reactors, wherein each reactor of the plurality of reactors performs a process comprising: (a) an adsorption step, comprising contacting an input stream of said gaseous mixture with a solid adsorbent and adsorption of target component from said input stream, providing a target component-loaded adsorbent and a waste stream depleted of the target component; (b) heating of said loaded adsorbent and desorption of a first amount of target component, providing a partially regenerated adsorbent and a first output stream containing the desorbed target component; (c) cooling of said at least partially regenerated adsorbent, the process of each of the plurality of reactors including: a rinse step (a1) after said adsorption step (a) and before said heating step (b), wherein said loaded adsorbent is contacted with a rinse stream containing the target component, wherein an amount of target component contained in said rinse stream is adsorbed and a purge stream depleted of the target component is produced; a purge step (b1) before said cooling step (c), wherein the partially regenerated adsorbent is contacted with at least a portion of the purge stream which is provided by at least one other reactor of said plurality of reactors while performing the rinse step (a1), wherein a second amount of target component is released providing a second output stream containing the target component; wherein the rinse stream used in said rinse step (a1) comprises at least a portion of the second output stream provided by at least one other reactor of said plurality of reactors while performing the purge step (b1), wherein a first reactor performs the purge step (b1) providing said second output stream and a second reactor performs the rinse step (a1) providing said purge stream, wherein at least a portion of said second output stream is used as rinse stream for the rinse step (a1) of said second reactor and at least a portion of said purge stream is used for the purge step (b1) of said first reactor, thus forming a closed loop between said first and second reactor.

2. The temperature swing adsorption process of claim 1, wherein said at least a portion of the purge stream and said at least a portion of the second output stream acting as rinse stream are provided by two different reactors.

3. The temperature swing adsorption process of claim 1, wherein said at least a portion of the second output stream used as rinse stream and said at least a portion of the purge stream are routed to compressors to ensure their circulation in the closed loop.

4. The temperature swing adsorption process of claim 1, wherein said at least a portion of the second output stream is exchanged with or without an intermediate storage in a tank from said at least one other reactor undergoing the purge step (b1) to said reactor undergoing the rinse step (a1), and said at least a portion of the purge stream is exchanged with or without an intermediate storage in a suitable tank from said at least one other reactor undergoing the rinse step (a1) to said reactor undergoing the purge step (b1).

5. The temperature swing adsorption process of claim 1, wherein said at least a portion of the purge stream is cooled prior to subjection to the purge step (b1).

6. The temperature swing adsorption process of claim 1, wherein said at least a portion of the second output stream is heated prior to subjection to said rinse step (a1).

7. The temperature swing adsorption process of claim 1, wherein said heating step (b) comprises direct heat exchange with a heating medium in contact with the adsorbent, said heating medium being a stream containing predominantly the target component.

8. The temperature swing adsorption process of claim 1, wherein the cooling step (c) comprises direct heat exchange with a cooling medium in contact with the adsorbent, said cooling medium being a target component depleted-waste stream.

9. The temperature swing adsorption process of claim 8, wherein the cooling step (c) comprises direct heat exchange with at least a portion of the waste stream provided by at least one other reactor of said plurality of reactors while performing the adsorption step (a), said at least a portion of the waste stream being optionally cooled prior to subjection to the cooling step (c).

10. The temperature swing adsorption process of claim 1, wherein the heating step (b) and/or the cooling step (c) comprises indirect heat exchange.

11. The temperature swing adsorption process of claim 1, each reactor of said plurality of reactors performing a preliminary heating step (a2) after said rinse step (a1) and before said main heating (b), wherein during said preliminary heating (a2) a gaseous product containing said at least one side component is released from the adsorbent and is recycled to a reactor undergoing the adsorption step (a) or the rinse step (a1).

12. The temperature swing adsorption process of claim 11, wherein at least one of the following conditions applies: the time duration of the preliminary heating (a2) is from 0.1 to 10 times the time duration of the rinse step (a1); the time duration of the heating step (b) is from 10 to 70 times the time duration of the rinse step (a1); or the time duration of the cooling step (c) is from 10 to 50 times the time duration of the purge step (b1).

13. The temperature swing adsorption process of claim 1, wherein the temperature of the heating step (b) is not greater than 250° C.

14. The temperature swing adsorption process of claim 13, wherein the temperature of the heating step (b) is not greater than 200° C.

15. The temperature swing adsorption process of claim 13, wherein the temperature of the heating step (b) is not greater than 170° C.

16. The temperature swing adsorption process of claim 1, wherein said target component includes carbon dioxide.

17. The temperature swing adsorption process of claim 1 wherein said gaseous mixture includes a flue gas.

18. The temperature swing adsorption process of claim 17, wherein said flue gas includes a flue gas of an ammonia plant, methanol plant, or urea plant.

19. A plant for treating a gaseous mixture and removing a target component from said gaseous mixture with the process of claim 1, the plant comprising: a plurality of reactors, each of the plurality of reactors containing an adsorbent bed for selectively adsorbing said target component, wherein: each of the plurality of reactors operates a sequence of steps comprising: adsorption of the target component in the adsorbent bed, rinse of the adsorbent with a stream containing the target component, heating of the adsorbent for desorption of the target component, purge of the adsorbent with a stream depleted of the target component and cooling of the so obtained regenerated adsorbent, wherein the reactors are interconnected so that each of the plurality of reactors: during the purge step receives at least part of the stream depleted of the target component which is provided by at least one other reactor of said plurality of reactors while performing the rinse step; during the rinse step receives at least part of the stream containing the target component which is provided by at least one other reactor of said plurality of reactors while performing the purge step; and a first reactor performs the purge step (b1) providing an output stream and a second reactor performs the rinse step (a1) providing a purge stream, wherein at least a portion of said output stream of the first reactor is used as rinse stream for the rinse step (a1) of said second reactor and at least a portion of said purge stream of from the second reactor is used for the purge step (b1) of said first reactor, thus forming a closed loop between said first and second reactor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a block diagram of a temperature swing adsorption process for removing the carbon dioxide from a flue gas, according to a first embodiment of the invention.

(2) FIG. 2 is a block diagram of a temperature swing adsorption process, according to a second embodiment of the invention.

(3) FIG. 3 is a purity vs recovery curve of a TSA process which is not object of the present invention.

(4) FIG. 4 is a purity vs recovery curve of another TSA process which is not object of the present invention.

(5) FIG. 5 shows a purity vs recovery curve of a TSA process according to the embodiment of FIG. 1, in comparison with the curve of FIG. 3.

(6) FIG. 6 shows a purity vs recovery curve of a TSA process according to the embodiment of FIG. 2, in comparison with the curve of FIG. 4.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

First Embodiment

(7) Referring to FIG. 1, the process of the invention is carried out in a plurality of reactors, for example including reactors 101, 102, 103. Each reactor 101-103 contains a fixed bed of an adsorbent for a target component, for example zeolite 13X for adsorption of CO.sub.2.

(8) Each reactor performs a number of steps, namely: an adsorption step (a), a rinse step (a1), a heating step (b), a purge step (b1) and a cooling step (c). The reactors are interconnected and, during some of said process steps, a reactor may exchange one or more stream(s) with one or more other reactor(s). In FIG. 1, the blocks (a), (a1), (b), (b1), (c) denote the reactors 101, 102, 103 while performing said process steps.

(9) During adsorption step (a), a gas to be treated, for example a flue gas, is admitted to the reactor and the target component is adsorbed, resulting in a waste stream and partially loading the adsorbent with the target component. During the rinse step (a1), the adsorbent is slightly heated by direct contact with a stream rich of the target component which comes from the purge step (b1) of another reactor. As a consequence, a further amount of the target component can be adsorbed and the one or more side components are expelled, thus generating a purge stream. During the heating step (b), the adsorbent is heated by direct or indirect heat exchange, resulting in desorption of the target component and regeneration of the adsorbent. The purge step (b1) is made with the help of the purge stream taken from the rinse step (a1) of another reactor. Step (c) is the cooling step, which is made with the help of at least a portion of the waste stream (mainly containing the one or more side components) taken from the adsorption step (a) of another reactor. Said step (c) brings the adsorbent back to the adsorption temperature in order to start again the cycle with step (a). Said steps and said interactions between the reactors will be described in greater detail with reference to the working cycle of reactor 101.

(10) Adsorption Step (a)

(11) A flue gas 111 coming from a combustion process and containing predominantly carbon dioxide (CO.sub.2) and nitrogen (N.sub.2) and optionally containing water is supplied to the reactor 101, where CO.sub.2 is adsorbed over the zeolite bed of the reactor, the CO.sub.2 having a greater affinity with said adsorbent compared to nitrogen.

(12) As a result, step (a) provides a CO.sub.2-loaded adsorbent and a CO.sub.2-depleted effluent 112, containing predominantly N.sub.2. A portion 113 of said effluent 112 can be used for the cooling step (c) of another reactor (for example of reactor 103), as will be explained below. The remaining portion 114 of the effluent 112 is exported and can be vented or used for a further scope if appropriate. For example in an ammonia plant, said stream 114, which is rich in nitrogen, can be used for the synthesis of ammonia.

(13) Preferably, the adsorption step (a) takes place at ambient temperature, for example at a temperature in the range 15 to 30° C. Preferably said step (a) is carried out upflow, which means that the flue gas 111 is supplied from the bottom of the reactor 101 and the waste stream 112 leaves the reactor 101 from the top, being N.sub.2 lighter than CO.sub.2.

(14) Rinse Step (a1)

(15) The reactor 101 receives a gaseous CO.sub.2-rich rinse stream 127 produced by another reactor of the plurality, for example by the reactor 102, while performing the purge step (b1). Said rinse stream 127 is fed to the bottom of the reactor 101, meaning that step (a1) is carried out in the same upflow direction as step (a).

(16) The rinse stream 127 is optionally heated in an external heat exchanger 10 prior to admission to said reactor 101. For example the rinse stream 127 is heated to a temperature of 343 K (70° C.).

(17) During said step (a1), some of the carbon dioxide contained in the rinse stream 127 is adsorbed over the adsorbent bed, which is already partially loaded with CO.sub.2 as a consequence of the previous adsorption step (a); another waste stream 115 mainly containing N.sub.2 is obtained, which is used for the purge step (b1) of another reactor (for example of reactor 102), as will be explained below. Said waste stream 115 will be also referred to as purge stream. Said purge stream may however contain some CO2.

(18) Said purge stream 115 is optionally cooled in an external heat exchanger 20 prior to admission to said reactor 102. For example the purge stream 115 is cooled to a temperature of 283 K (10° C.).

(19) Contrary to what happens to the waste stream 112 or to a part 114 thereof, said purge stream 115 is neither exported from the process nor vented into atmosphere. This is advantageous because possible losses of CO2 are avoided.

(20) In some embodiments, the rinse step (a1) of reactor 101 and the purge step (b1) of reactor 102 are synchronized, which means that the rinse stream 127 leaving the reactor 102 passes into the reactor 101 without an intermediate storage. In other embodiments, said CO.sub.2-rich gas 127, produced by the purge step (b1) of reactor 102, is stored in a suitable tank (not shown) outside the source reactor 102 and subsequently introduced into the reactor 101 for the above described rinse step (a1). The latter embodiment with intermediate storage may provide a greater flexibility since the duration of steps (a1) and (b1) of the two reactors may be different.

(21) Similarly, the purge stream 115 may be exchanged with or without an intermediate storage in a suitable tank from a reactor undergoing the rinse step (a1) to another reactor undergoing the purge step (b1).

(22) Heating Step (b)

(23) The CO.sub.2-loaded adsorbent is heated, for example to 420 K (147° C.); as a consequence, CO.sub.2 is desorbed producing a current 116 of CO.sub.2 of high purity and the adsorbent of the reactor 101 is partially regenerated.

(24) The heating step (b) can be performed either by means of indirect heat exchange or direct heat exchange.

(25) In case of indirect heat exchange, one of the reactor ends is kept open while the other is kept closed, meaning that it is a semi-open heating step.

(26) In case of direct heat exchange, a hot regeneration medium is supplied to the reactor for direct contact with the adsorbent. Preferably, both ends of the reactor 101 are kept open and said regeneration medium flows opposite with respect to steps (a) and (a1), namely from the top to the bottom. Preferably said regeneration medium is made predominantly of CO.sub.2 (i.e. of the target component).

(27) Purge Step (b1)

(28) The adsorbent in the reactor 101 is purged with a purge stream 135 which results from the rinse step (a1) of another reactor, for example of reactor 103. Said stream 135 is similar in composition to the previously described stream 115 obtained in the reactor 101 itself. Said purge stream 135 is fed to the reactor 101 from the top, meaning that step (b1) is carried out in the opposite flow direction with respect to steps (a) and (a1).

(29) Said purge stream 135 is optionally cooled in an external heat exchanger 20′ prior to admission into the reactor 101. For example the purge stream 135 is cooled to a temperature of 283 K (10° C.).

(30) During said purge step (b1), the purge stream 135 “cleans” the adsorbent by displacing a CO.sub.2-rich stream 117, so that more CO.sub.2 can be adsorbed during the adsorption step (a) and the recovery is increased. Said CO.sub.2-rich stream 117 is advantageously subjected to the rinse step (a1) of another reactor, in the same manner as the CO.sub.2-rich stream 127 previously described. Said stream 117 is optionally heated in an external heat exchanger 10′.

(31) Purge streams 115, 135 may be routed to suitable compressors (not shown) before being subjected to reactors 102, 101 performing the purge step (a1), respectively.

(32) Similarly, rinse streams 117, 127 may be routed to suitable compressors (not shown) before being subjected to reactors 103, 101 performing the rinse step (a1), respectively.

(33) Said compressors ensure circulation of the gas in the closed loop 115-127-115 between reactors 102, 101 and in the closed loop 135-117-135 between reactors 101, 103.

(34) In some embodiments, the rinse step (a1) of reactor 103 and the purge step (b1) of reactor 101 are synchronized, so that the purge stream 135 leaving the reactor 103 passes into the reactor 101 without an intermediate storage. In other embodiments, a storage tank for said stream 135 is provided.

(35) Cooling Step (c)

(36) The adsorbent is cooled down to the adsorption temperature in order to restart the cycle.

(37) The cooling step (c) can be performed either by means of indirect heat exchange or by means of direct heat exchange.

(38) According to the example of the figure, a waste stream 133 provided by reactor 103 while performing the adsorption step (a) is supplied to the reactor 101, wherein it directly contacts the adsorbent acting as cooling medium. Accordingly, both ends of the reactor 101 are kept open and the waste stream 133 flows opposite with respect to steps (a) and (a1), namely from the top to the bottom, leaving the reactor as stream 118. Alternatively, step (c) is semi open and the waste stream 133 only pressurizes the reactor.

(39) The waste stream 133 is optionally cooled in an external heat exchanger 30 prior to admission to said reactor 101.

(40) The other reactors, such as reactors 102 and 103, perform the same steps.

Second Embodiment

(41) Referring to FIG. 2, the process of the invention is carried out in a plurality of reactors, for example including reactors 201, 202, 203. Each reactor 201-203 contains a fixed bed of an adsorbent for a target component, for example zeolite 13X for adsorption of CO.sub.2.

(42) Each reactor performs a sequence of steps which is the same sequence as the first embodiment, with the addition of a preliminary heating step (a2), after the rinse step (a1) and before the heating step (b). The steps common to the first embodiment are not described in detail for the sake of brevity. In order to better distinguish step (a2) from step (b), the latter will be referred to as main heating step.

(43) Combining steps (a1) and (b1) with a further pre-heating step (a2) gives rise to a synergy, which allows to obtain the high recovery and purity of step (a2) and the low energy consumption of steps (a1) and (b1).

(44) Referring to a reactor 201, a gas mixture 211 containing predominantly carbon dioxide (CO.sub.2) and nitrogen (N.sub.2) is mixed with a gaseous product 219 predominantly containing N.sub.2 and a small amount of CO.sub.2, obtained from said preliminary heating step (a2), to provide a gaseous input stream 220.

(45) Said input stream 220 is supplied to the reactor 201 for the adsorption step (a) wherein a waste stream 212 is produced and the adsorbent is loaded with CO.sub.2. A portion 213 of the waste stream can be used for cooling another reactor and the remaining portion 214 is exported or vented.

(46) Then, the reactor 201 undergoes the rinse step (a1) with the help of a rinse stream 227 from the reactor 202 undergoing the purge step (b1), optionally with intermediate heating in the exchanger 10.

(47) During said rinse step (a1), some of the carbon dioxide contained in the rinse stream 227 is adsorbed over the adsorbent bed and a purge stream 215 mainly containing N.sub.2 is obtained, which is used for the purge step (b1) of reactor 202. Said purge stream 215 is optionally cooled in an external heat exchanger 20 prior to admission to said reactor 202.

(48) Then, the reactor 201 undergoes the preliminary heating step (a2), during which the CO.sub.2-loaded adsorbent contained in the reactor 201 is further heated. The temperature reached by the adsorbent during said preliminary heating step (a2) is lower than the temperature reached during the subsequent main heating step (b). For example, the adsorbent is heated to a temperature ranging between 360 and 380 K (i.e. between 87 and 107° C.) during said preliminary heating step (a2).

(49) During said step (a2), the nitrogen and a small amount of CO.sub.2 are desorbed providing the gaseous product 219. During said step (a2), the pressure is kept constant and only the bottom end of the reactor is kept open.

(50) In some embodiments, the so obtained gaseous product 219 is stored in a tank 40 and subsequently mixed with the flue gas 211 to provide the gaseous stream 220 feeding the adsorption step (a), in order to recover the CO.sub.2 contained therein. In other embodiments (not shown), said gaseous product 219 is mixed with the flue gas feed of another reactor, for example of reactor 202 or 203.

(51) After the preliminary heating step (a2), the reactor 201 undergoes the sequence of main heating (b), purge (b1) and cooling (c).

(52) The purge step (b1) is carried out with the help of a purge stream 235 taken from reactor 203, optionally with intermediate cooling in a heat exchanger 20′, and releases a CO.sub.2-rich stream 217 which is advantageously subjected to the rinse step (a1) of reactor 203. Said stream 217 is optionally heated in an external heat exchanger 10′. The main heating (b) releases a stream 216 of the target component, in this case of CO.sub.2. The cooling step (c) is performed with the aid of a waste stream 233 provided by reactor 203 performing the adsorption step (a), which acts as cooling medium and leaves the reactor as stream 218. The waste stream 233 is optionally cooled in an external heat exchanger 30 prior to admission to said reactor 101.

(53) Similarly to embodiment 1, suitable compressors ensure circulation of the gas in the closed loop 215-227-215 between reactors 202, 101 and in the closed loop 235-217-235 between reactors 201, 203.

(54) The other reactors, such as reactors 202 and 203, perform the same steps.

COMPARATIVE EXAMPLES

Example 1

(55) A flue gas with the following molar composition:

(56) CO.sub.2=0.12, N.sub.2=0.88

(57) is subjected to a process carried out in a plurality of interconnected reactors, each containing a fixed bed of an adsorbent for CO2. Each reactor performs an adsorption step (a), a rinse step (a1), a heating step (b), a purge step (b1) and a cooling step (c).

(58) During adsorption step (a), the flue gas is admitted to the reactor and CO2 is partially adsorbed, resulting in a waste stream and CO2-partially loaded adsorbent. During the rinse step (a1), the adsorbent is slightly heated by direct contact with a CO2-rich stream which comes from the purge step (b1) of another reactor, a further amount of CO2 is adsorbed and N.sub.2 is expelled, thus generating another waste stream. During the heating step (b), the adsorbent is heated by direct or indirect heat exchange, resulting in CO2 desorption and regeneration of the adsorbent. The purge step (b1) is made with the help of a N2-containing waste stream taken from the adsorption step (a) of another reactor. The cooling step (c) brings the adsorbent back to the adsorption temperature in order to start again the cycle with step (a).

(59) By varying the time duration of the above five steps of adsorption (a), rinse (a1), heating (b), purge (b1) and cooling (c), the curve of FIG. 3 has been identified with computer simulation.

(60) The curve of FIG. 3 delimits the maximum feasible CO.sub.2 purity and CO.sub.2 recovery in a two dimensional plot of purity vs recovery. As shown in FIG. 3, the maximum feasible purity is slightly higher than 99% but is achievable only for a recovery of 85%. On the other hand, the maximum feasible recovery is around 98% but is achievable only with a purity of around 98.5%.

Example 2

(61) A combustion flue gas with the same composition of the gas of example 1 is subjected to a process carried out in a plurality of interconnected reactors, each containing a fixed bed of an adsorbent for CO2. Each reactor performs a sequence of steps which is the same sequence as the example 1, with the addition of a preliminary heating step (a2), after the rinse step (a1) and before the heating step (b).

(62) The temperature reached by the adsorbent during the preliminary heating (a2) is lower than the temperature reached during the subsequent heating (b). During said step (a2), the nitrogen and a small amount of CO.sub.2 are desorbed providing a gaseous product which is subsequently mixed with a flue gas feeding the adsorption step (a), thus recovering the CO.sub.2 contained therein.

(63) By varying the time duration of the above six steps of adsorption (a), rinse (a1), preliminary heating (a2), heating (b), purge (b1) and cooling (c), the curve of FIG. 4 has been identified with computer simulation.

(64) The curve of FIG. 4 delimits the maximum feasible CO.sub.2 purity and CO.sub.2 recovery in a two dimensional plot of purity vs recovery. As shown in FIG. 4, the maximum feasible purity is 94%, which is achievable for a recovery lower than 90%. For a unitary recovery, the purity is very low, i.e. lower than 91%.

Example 3: First Embodiment of the Invention

(65) A combustion flue gas with the same composition of the gas of the previous examples is subjected to the process according to FIG. 1.

(66) FIG. 5 shows the curves delimiting the feasible CO.sub.2 purity and CO.sub.2 recovery for the process of FIG. 1 and the process of example 1 taken as reference. The process of FIG. 1 substantially distinguishes from the reference process in that it comprises a closed loop between a reactor performing the rinse step (a1) and another reactor performing the purge step (b1).

(67) In greater detail, a first reactor performs the purge step providing an output stream containing the target component and a second reactor performs the rinse step providing a purge stream depleted of the target component. At least a portion of said output stream is used as rinse stream for the rinse step of said second reactor and at least a portion of said purge stream is used for the purge step of said first reactor, thus forming a closed loop between said first and second reactor.

(68) The new process of FIG. 1 largely outperforms the process of example 1 in terms of CO2 recovery and CO2 purity.

(69) As can be seen from FIG. 5, the “CO2 recovery” vs “CO2 purity” curve of the new process is shifted up and right with respect to the reference process. The improvement of the new process is due to the presence of a closed loop, which prevents loss of product and enables optimization of the time steps to achieve better separation performances than the reference process.

(70) For example, for a CO2 purity of 99%, the new process allows to obtain a recovery of 98%, while the reference process allows to obtain a recovery of 95%.

(71) Furthermore, for a CO2 recovery of 95%, the new process allows to obtain a purity greater than 99.5%, while the reference process allows to obtain a purity of 99%.

Example 4: Second Embodiment of the Invention

(72) A combustion flue gas with the same composition of the gas of the previous examples is subjected to the process according to FIG. 2.

(73) FIG. 6 shows the curves delimiting the feasible CO.sub.2 purity and CO.sub.2 recovery for the process of FIG. 2 and the process of example 2 taken as reference. The process of FIG. 2 substantially distinguishes from the reference process in that it comprises a closed loop between a reactor performing the rinse step (a1) and another reactor performing the purge step (b1).

(74) As can be clearly seen from FIG. 6, the “CO2 recovery” vs “CO2 purity” curve of the new process of FIG. 2 is shifted up and right with respect to the reference process of example 2. Accordingly, the new process largely outperforms the reference process in terms of CO2 recovery and CO2 purity. Also in this case, the improvement of the new process is due to the presence of a closed loop.

(75) For example, for a CO2 purity of 93.5%, the new process allows to obtain a recovery of 98%, while the reference process allows to obtain a recovery of 95%.

(76) Furthermore, for a CO2 recovery of 95%, the new process allows to obtain a purity of 94%, while the reference process allows to obtain a purity of 93.5%.