Methods and devices for combining cooling and heat transfer effects

Abstract

Processes using liquid transfer fluids with a triple point temperature below -125°C (such as isopentane) are carried out to recover the cold energy used to sublimate and melt frozen material (especially CO2) on the exchanger surface. The same fluid circulates through two coupled circuits, one for pure cooling and the other for heat transfer during the thawing operation, transferring the cooling capacity recovered during the thawing process.

Description

Technical Field

[0001] The present invention relates to the treatment of flue gas containing water vapor and carbon dioxide, and optionally also nitrogen oxides.

Background Art

[0002] Recovering carbon dioxide CO2 and reusing it or storing it geologically has become a major goal for limiting the increase in the CO2 concentration in the atmosphere.

[0003] Many gas mixtures containing a high CO2 concentration need to be treated at their emission sources.

[0004] The main gas mixtures to be treated are as follows. That is, - Biogas that may contain 30% to 50% CO2 by volume, - Syngas derived from the gasification of biomass that may contain 25% to 35% CO2 by volume, - Combustion flue gas from power plants (natural gas, wood, coal, fuel oil) that may contain CO2 in a range of 10% to 15% by volume concentration, - Flue gas from industrial processes for manufacturing glass, lime, cement, and steel, where the volume concentration of CO2 can range from 10% to 40%. are included.

[0005] It should also be noted that all of these gas mixtures contain steam. Industrial flue gas usually contains 10 to 35% CO2 and 5 to 15% water vapor.

[0006] The flow rate of the flue gas to be treated is usually in the range of 50,000 to 1 million Nm 3 / h. The low-temperature CO2 freezing process requires a surface area of several thousand m 2 for such a flue gas flow rate. These exchange surface areas are distributed among dozens or even hundreds of exchangers operating according to the freezing and thawing cycles of CO2.

[0007] In terms of energy balance, the condensation and subsequent freezing of water accounts for 10% to 25% of the energy requirements when these smokes are cooled from 50°C to -40°C.

[0008] Cooling and freezing CO2 from -90°C to -120°C accounts for approximately 45% to 55% of the total energy consumption, with the remaining 100% being used for nitrogen cooling.

[0009] For example, the process of freezing and thawing CO2, as described in the international publication No. 02 / 060561 (Armines, 2002), requires the recovery of carbon dioxide sublimation energy and minimization of energy consumption associated with CO2 freezing.

[0010] In state-of-the-art technology, the sublimation energy of CO2 is recovered through various processes, including recovery in the form of a mixture of liquids and solids, as described in International Publication No. 2012 / 061544 (Battelle, 2012) or U.S. Patent Application Publication No. 2012 / 0103561 (Battelle, 2012), recovery using a refrigerant, as described in U.S. Patent No. 6082133 (Cryo Fuel Systems, 2000), or recovery under low pressure, as described in International Publication No. 2016 / 162643 (Cryo Pur, 2016).

[0011] Freezing CO2 at pressures below the triple point, occurring at -56.5°C and 520 kPa, requires energy ranging from 550 to 595 kJ / kg, depending on the back sublimation temperature.

[0012] Here, back sublimation refers to the direct transition from the gas phase to the solid phase. Parameters affecting carbon dioxide capture by back sublimation are the subject of modeling trials; see, for example, Tian et al. Energy Engineering 2020, 117(5), 267-277. https: / / DOI.org / 10.32604 / EE.2020.011440; Ababneh et al. Processes, Vol 10, Iss 2406, p2406(2022) DOI:10.3390 / pr10112406.

[0013] The sublimation and melting of CO2 releases approximately 200 to 220 kJ / kg of energy. [Prior art documents] [Patent Documents]

[0014] [Patent Document 1] International Publication No. 02 / 060561 [Patent Document 2] International Publication No. 2012 / 061544 [Patent Document 3] U.S. Patent Application Publication No. 2012 / 0103561 [Patent Document 4] U.S. Patent No. 6082133 [Patent Document 5] International Publication No. 2016 / 162643 [Non-patent literature]

[0015] [Non-Patent Document 1] Tian et al.Energy Engineering 2020,117(5),267-277.https: / / DOI.org / 10.32604 / EE.2020.011440 [Non-Patent Document 2] Ababneh et al.Processes,Vol 10,Iss 2406,p2406(2022)DOI:10.3390 / pr10112406

Non-Patent Document 3

Non-Patent Document 4

Summary of the Invention

[0016] An object of the present invention is to solve problems related to high energy efficiency management not only for the freezing and thawing cycles of CO2 but also for substances such as water (H2O) or nitrogen dioxide (NO2), regardless of the flow rate, and desirably for high flow rates as well.

[0017] The present invention provides for recovering cold and heat energy by a transfer fluid that serves a dual role of a refrigerant and a heat transfer fluid in order to recover energy from a very low temperature (about -150°C) to ambient temperature.

[0018] Such fluids are hydrocarbons that are liquid at ambient temperature, such as isopentane (2-methylbutane, CAS 78-78-4) or isohexane (2-methylpentane, CAS 107-83-5), with a triple point temperature below -125°C, preferably below -150°C. According to Tan et al., the triple point temperature of 2-methylbutane is 117K, i.e., about -156°C (Journal of thermal analysis. June 1994 41(6):1577-1592 DOI:10.1007 / bf02549956). According to Douslin et al., the triple point temperature of 2-methylpentane is 119 K, which is approximately -154°C (Douslin, DR; Huffman, HM, "Low-Temperature Thermal Data on the Five Isomeric Hexanes", J. Am. Chem. Soc., 1946, 68, 1704, doi.org / 10.1021 / ja01213a006).

[0019] The present invention provides a combination of two circuits, one being a cooling circuit and the other a heat transfer and cooling circuit, where the two circuits use the same transfer fluid, the triple point of which is preferably below -125°C, more preferably below -150°C, for example isopentane, whose triple point is -156°C, and the transfer fluid recovers the cold energy of the sublimation and melting of CO2 and, if present in the gas mixture being cooled, the cold energy of molecules such as nitrous oxide (N2O), nitrogen dioxide (NO2), and water. The cooling fluid is cooled to the lowest temperature level. The heat transfer and cooling fluid recovers the cold thawing energy (then functions as heat transfer) and transfers this cold energy at a high temperature (thus functioning as cooling).

[0020] Furthermore, energy recovery is carried out by a process involving the alternating operation of at least one pair of exchangers, one for freezing CO2 and the other for thawing CO2. Depending on the scale of the facility, tens or even hundreds of pairs of exchangers can operate in parallel and alternately.

[0021] Furthermore, the energy recovery is carried out by a process that operates alternately with at least a pair of exchangers, one of which operates by freezing water and the other by thawing water.

[0022] Also, the energy recovery is carried out by a process that operates alternately with at least a pair of exchangers, one of which operates by freezing nitrogen dioxide NO2 or nitrous oxide N2O and the other by thawing them.

[0023] For these purposes, according to a first aspect, a process for treating a smoke containing water vapor and carbon dioxide, and optionally also nitrogen oxides, the process comprising a first step of cooling the smoke to be treated by freezing water and optionally also freezing nitrogen dioxide NO2, this first step producing the cooled smoke, the process comprising a second step of cooling and dehumidifying the cooled smoke by freezing the water contained in these cooled smokes, this second step producing the dehumidified smoke, the process comprising a third step of cooling and decarbonizing the dehumidified smoke by freezing the carbon dioxide contained in the dehumidified smoke so as to become carbon dioxide ice and optionally also freezing the nitrogen oxides contained in the dehumidified smoke, each of the three smoke treatment steps being carried out by one of a pair of exchangers, a transfer fluid circulating in each exchanger, each exchanger of the pair of exchangers being in a freezing mode for cooling the smoke while the other exchanger is in a thawing mode of the water ice or carbon dioxide ice formed during the previously carried out cooling step, the transfer fluid performing a cooling function in the exchanger in the freezing mode, the transfer fluid performing a heat transfer function in the exchanger in the thawing mode, the transfer fluid recovering the cold thermal energy for sublimating and melting the carbon dioxide ice obtained in the third cooling and decarbonizing step and transferring this cold thermal energy for cooling the smoke in the first treatment step, and the transfer fluid is brought to have a triple point with a temperature below -125 °C.

[0024] Preferably, the transfer fluid contains isopentane or isohexane.

[0025] Preferably, the transfer fluid circulates within the cooling circuit, the transfer fluid (preferably the same transfer fluid) circulates within the heat transfer / cooling circuit, the heat transfer / cooling circuit recovers the cold energy to sublimate and melt the carbon dioxide ice obtained in the third step, and in the first processing step, this cold energy is transferred to cool the smoke.

[0026] In some embodiments, the process includes: measuring the carbon dioxide concentration of smoke to be processed and cooled in a first processing step; comparing the measured carbon dioxide concentration to a threshold, wherein a predetermined flow rate of a heat transfer / cooling circuit provides the cooling capacity to cool the smoke to a target temperature in the first cooling step relative to this threshold; and mixing the transfer fluid of the cooling circuit with the transfer fluid of the cooling / heat transfer circuit when the measured carbon dioxide concentration is less than the threshold, wherein the flow rate of the resulting mixture is substantially equal to a predetermined flow rate.

[0027] Preferably, in the third step exchanger for cooling and decarbonizing the cold smoke, the transfer fluid of the heat transfer / cooling circuit circulates alternately with the transfer fluid of the cooling circuit in the exchanger, ensuring that the transfer fluid of the cooling circuit cools the smoke and freezes the carbon dioxide within the exchanger, and that the transfer fluid of the heat transfer / cooling circuit thaws the carbon dioxide within the exchanger.

[0028] Preferably, in the exchanger of the first step of cooling the smoke to be processed, the transfer fluid of the heat transfer / cooling circuit circulates alternately with the transfer fluid of the cooling circuit in the exchanger, so that the transfer fluid of the cooling circuit partially ensures, or does not partially ensure, the cooling of the smoke and the freezing of water into ice in the exchanger, and the transfer fluid of the heat transfer / cooling circuit partially or completely ensures the cooling of the smoke and the freezing of water, thereby performing a cooling function by transferring the recovered cold energy when the carbon dioxide thaws in the third step, and the transfer fluid of the heat transfer / cooling circuit also performs a heat transfer function when the ice in the exchanger thaws.

[0029] Preferably, in a second step exchanger for cooling and dehumidifying the smoke, the transfer fluid of the heat transfer / cooling circuit circulates alternately with the transfer fluid of the cooling circuit in the exchanger, ensuring that the transfer fluid of the cooling circuit freezes the water so that it cools the smoke and turns into ice within the exchanger, and that the transfer fluid of the heat transfer / cooling circuit thaws the ice within the exchanger.

[0030] Ideally, the same transfer fluid circulates within the cooling circuit and the heat transfer / cooling circuit.

[0031] According to a second embodiment, a device is provided for processing smoke containing water vapor and carbon dioxide, and optionally also containing nitrogen oxides, the device comprising a first pair of exchangers for a first step of cooling the smoke to be processed by freezing water, in which the first step generates cooled smoke, the device comprising a second pair of exchangers for a second step of cooling and dehumidifying the cooled smoke by freezing the water contained in the cooled smoke, and optionally also freezing nitrogen dioxide (NO2), in which the second step generates dehumidified smoke, the device freezing the carbon dioxide contained in the dehumidified smoke into carbon dioxide ice, and optionally also freezing nitrogen oxides contained in the dehumidified smoke For a third step of cooling and decarbonizing the dehumidified smoke by freezing, a third pair of exchangers is provided, in which the transfer fluid circulates within each exchanger, with each exchanger in the pair entering a freezing mode for cooling the smoke, while the other exchanger enters a thawing mode for the water ice or carbon dioxide ice formed during a previously performed cooling step, the transfer fluid performing a cooling function within the exchanger in freezing mode and a heat transfer function within the exchanger in thawing mode, the transfer fluid recovering cold energy to sublimate and melt the carbon dioxide ice obtained in the third cooling and decarbonization step, and transferring this cold energy in the first processing step to cool the smoke, the transfer fluid having a triple point where its temperature is below -125°C.

[0032] Preferably, the device comprises a cooling circuit through which a transfer fluid circulates and a heat transfer / cooling circuit through which a transfer fluid (preferably the same transfer fluid) circulates, the heat transfer / cooling circuit recovering the cold energy to melt and sublimate the carbon dioxide ice obtained in the third cooling and decarbonization step, and transferring this cold energy in the first processing step to cool the smoke.

[0033] Preferably, the device comprises, in a first processing step, means for measuring the carbon dioxide concentration of smoke processed and cooled by a first pair of exchangers; means for comparing the measured carbon dioxide concentration to a threshold, wherein a predetermined flow rate of the heat transfer / cooling circuit provides a cooling capacity to cool the smoke to a target temperature in the first cooling step relative to this threshold; and means for mixing the transfer fluid of the cooling circuit with the transfer fluid of the cooling / heat transfer circuit when the measured carbon dioxide concentration is less than the threshold, wherein the flow rate of the resulting mixture is substantially equal to the predetermined flow rate.

[0034] Preferably, the transfer fluid contains isopentane or isohexane.

[0035] Ideally, the same transfer fluid circulates within the cooling circuit and the heat transfer / cooling circuit.

[0036] Further objects and advantages of the present invention will become apparent in the description of several embodiments, and will be described with reference to the accompanying drawings. [Brief explanation of the drawing]

[0037] [Figure 1] This is a schematic diagram of equipment for cooling smoke, freezing and thawing water vapor, and then cooling carbon dioxide, the equipment comprising a cooling circuit and a heat transfer / cooling circuit. [Figure 2] Figure 1 is a schematic diagram of the equipment, with some elements of the cooling circuit omitted for simplification, while Figure 2 shows details of some elements of the heat transfer / cooling circuit. [Modes for carrying out the invention]

[0038] In the following explanation, the temperature values ​​correspond to an example of decarbonization of smoke containing 30% CO2 and 70% nitrogen by mass, which corresponds to a volume concentration of 21.5% carbon dioxide (CO2) and, consequently, 78.5% nitrogen.

[0039] The equipment shown in the diagram enables the cooling of such smoke on circuit 700, followed by the freezing and thawing of water vapor, and then the freezing and thawing of carbon dioxide.

[0040] In the description, the terms "upstream of ~" and "downstream of ~" are used in relation to the direction of fluid circulation, which is indicated by arrows placed on the ducts of different circuits in the facility, and the ducts are represented in the form of lines.

[0041] The equipment includes a cooling circuit 10 and a heat transfer / cooling circuit 20.

[0042] The use of the " / " symbol indicates that the fluid circulating within circuit 20 has either a heat transfer fluid function or a cooling fluid function, depending on the operating mode of the equipment.

[0043] Since circuit 700 is partially represented, the cooling circuit 10 and the heat transfer / cooling circuit 20 are clearly visible.

[0044] The equipment shown in the attached Figure 1 includes two exchangers 110 and 112 for cooling smoke and freezing water.

[0045] The smoke to be cooled alternately enters housings 109 or 111, which include exchangers 110 and 112, respectively, through lines 701 and 702.

[0046] The system includes two air coolers 106 and 108 to further cool the smoke discharged from either air cooler 110 or air cooler 112.

[0047] The smoke discharged from the exchanger 110 or exchanger 112 alternately enters the housings 104 or 107 that house the exchangers 106 and 108, respectively, through lines 705 or 706.

[0048] The system includes two exchangers 101 and 103 for cooling and decarbonizing the dehumidified smoke. Here, decarbonization refers to the reduction of greenhouse gases, particularly carbon dioxide, contained in the smoke.

[0049] The smoke to be cooled and decarbonized alternately enters housings 100 or 102, which house the exchangers 101 and 103, respectively, through lines 709 and 710.

[0050] The cooling fluid flowing into the exchangers 101, 103, 106, 108, 110, and 112 (hereinafter referred to as evaporators 101, 103, 106, 108, 110, and 112) comes from the cooling circuit 10.

[0051] In circuit 10, the inflow of cooling fluid into evaporator 101 or evaporator 103 is controlled by a solenoid valve 121 located on the inlet line 11 of evaporator 101 and by a solenoid valve 123 located on the inlet line 12 of evaporator 103. The outflow of refrigerant from evaporator 101 is controlled by a solenoid valve 1110. The outflow of cooling fluid from evaporator 103 is controlled by a solenoid valve 1111. The ducts carrying the outlet solenoid valves 1110 and 1111 of evaporators 101 and 103 are connected to a common branch pipe 13.

[0052] In circuit 10, the circulation of cooling fluid from the common branch pipe 13 to either evaporator 106 or evaporator 108 is controlled by a solenoid valve 1112 located in the inlet line 14 of evaporator 106 and a solenoid valve 1113 located in the inlet line 15 of evaporator 108. The outflow of cooling fluid from evaporator 106 is controlled by a solenoid valve 1114 located in the outlet branch pipe 16 of evaporator 106. The outflow of cooling fluid from evaporator 108 is controlled by a solenoid valve 1115 located in the outlet branch pipe 17 of evaporator 108. The outlets of evaporators 106 and 108 are connected to the common branch pipe 19 by branch pipes 16 and 17.

[0053] In circuit 10, the circulation of cooling fluid from the common branch pipe 19 to either the evaporator 110 or evaporator 112 is controlled by two solenoid valves: a solenoid valve 1118 on the inlet branch pipe 29 to evaporator 110 and a solenoid valve 1119 on the inlet branch pipe 21 to evaporator 112. The outflow of cooling fluid from evaporator 110 is controlled by a solenoid valve 1120. The outflow of cooling fluid from evaporator 112 is controlled by a solenoid valve 1121. The ducts carrying the solenoid valves 1120 and 1121 are joined at the common branch pipe 22.

[0054] The cooling circuit 10 includes a counter-flow type cooling exchanger 30 and a pump 1 for circulating the cooling fluid, located downstream of the common branch pipe 22.

[0055] The cooling circuit 10 includes a counter-flow type cooling exchange 40 downstream of the cooling exchange 30.

[0056] The two probes 136 and 137 enable the measurement of the coolant temperature at the inlet and outlet of the cooling exchanger 30.

[0057] The two probes 138 and 120 enable the measurement of the coolant temperature at the inlet and outlet of the cooling exchanger 40.

[0058] The equipment includes a heat transfer / cooling circuit 20.

[0059] The circuit 20 includes a pump 2 for circulating the transfer fluid.

[0060] Circuit 20 transports the transfer fluid to the inlet of evaporator 103, which is located above the inlet line 12 of evaporator 103, through a connection to the cooling circuit 10.

[0061] The inflow of the transfer fluid into the evaporator 103 is controlled by a solenoid valve 204 installed in the branch pipe 202 of circuit 20, which is located upstream of the connection between circuit 10 and circuit 20.

[0062] Circuit 20 transports the transfer fluid to the inlet of the evaporator 101, which is located above the inlet line 11 of the evaporator 101, through a connection to the cooling circuit 10.

[0063] The inflow of the transfer fluid into the evaporator 101 is controlled by a solenoid valve 203 installed in the branch pipe 201 of circuit 20, which is located upstream of the connection between circuit 10 and circuit 20.

[0064] The circulation of the transfer fluid in evaporators 101 and 103 allows the evaporators to be defrosted, and the transfer fluid thereby transfers heat and circulates at the outlets of evaporators 101 and 103 through outlet branch pipes 223 and 224, with solenoid valves 221 and 222 installed in each of these two outlet branch pipes 223 and 224.

[0065] The outlet branch pipes 223 and 224 of the evaporators 101 and 103 are connected to a common line 24. The solenoid valve 225 is installed on this common line 24 between the connection point with outlet branch pipe 223 and the connection point with outlet branch pipe 224.

[0066] When the transfer fluid flows out of the evaporator 101, solenoid valves 1110 and 225 close, solenoid valve 221 opens, and the transfer fluid flows out of the evaporator 101 through the branch pipe 223 and is sent to the reservoir 28 through the common branch pipe 24.

[0067] When the transfer fluid flows out of the evaporator 103, solenoid valves 221 and 1111 close, solenoid valves 222 and 225 open, the transfer fluid flows out of the evaporator 103 via the branch pipe 224 and is sent to the reservoir 28 via the common branch pipe 24.

[0068] Reservoir 28 is connected to the common branch pipe 19 of circuit 10 by line 23.

[0069] The solenoid valve 231 is installed in line 23.

[0070] Therefore, the circuit 20 transports the transfer fluid to the inlet of evaporator 110 or the inlet of evaporator 112.

[0071] The inflow of the transfer fluid into the evaporator 110 is controlled by a solenoid valve 1118 installed in the branch pipe 29 of the circuit 10, and the transfer fluid flows out from the reservoir 28 through the branch pipe 23 with valve 231 open.

[0072] The inflow of the transfer fluid coming from the branch pipe 23 of the evaporator 112 is controlled by a solenoid valve 1119 installed in the branch pipe 21 of the circuit 10, and the transfer fluid flows out of the reservoir 28 through the branch pipe 23, with valve 231 open.

[0073] The circulation of the transfer fluid in evaporators 110 and 112 allows them to freeze, so that the transfer fluid acts as a cooling fluid, and the transfer fluid circulates at the outlets of evaporators 110 and 112, which are located on the common line 25.

[0074] Solenoid valve 215 is located in the outlet branch pipe 213 of evaporator 112. Solenoid valve 216 is located in the outlet branch pipe 214 of evaporator 110. The two outlet branch pipes 213 and 214 of evaporators 110 and 112 are connected to a common line 25.

[0075] When the transferred fluid flows out of the evaporator 110, the solenoid valve 1120 in circuit 10 closes, and the solenoid valve 216 installed in the branch pipe 214 of circuit 20 opens.

[0076] When the transferred fluid flows out of the evaporator 112, the solenoid valve 1121 in circuit 10 closes, and the solenoid valve 215 installed in the branch pipe 213 of circuit 20 opens.

[0077] The heat transfer / cooling circuit 20 includes a cooling system 50 and a flow meter 200.

[0078] The smoke inlet temperature of each exchanger 101, 103, 106, 108, 110, 112 is measured by probes 78, 79, 74, 75, 70, 71 supported by lines or pipes 709, 710, 705, 706, 701, 702.

[0079] The smoke discharge temperature from each exchanger 101, 103, 106, 108, 110, and 112 is measured by probes 80, 81, 76, 77, 72, and 73, supported by pipes 711, 712, 707, 708, 703, and 704.

[0080] The inflow temperature of the transfer fluid or cooling fluid flowing into the housings 100, 102, 104, 107, 109, and 111 of the exchangers 101, 103, 106, 108, 110, and 112 is measured by probes 122 (on branch pipe 11), 124 (on branch pipe 12), 127 (on branch pipe 14), 128 (on branch pipe 15), 131 (on branch pipe 29), and 132 (on branch pipe 21).

[0081] The temperature of the transfer fluid or cooling fluid flowing out of the housings 100, 102, 104, 107, 109, and 111 of the exchangers 101, 103, 106, 108, 110, and 112 is measured by probes 125, 126, 129 (on branch pipe 16), 130 (on branch pipe 17), 133, and 134.

[0082] The adjustment solenoid valve 1000 is located in the common branch pipe 19, between the junction point of the common branch pipe 19 and line 23, and the junction point of the common branch pipe 19 and branch pipe 18 which is connected to the common branch pipe 22.

[0083] The solenoid valve 1117 is installed in the connecting branch pipe 18.

[0084] Referring to Figure 1, the operation of the cooling circuit 10 on the one hand and the operation of the heat transfer / cooling circuit 20 on the other hand are explained in detail, showing the circulation of the same transfer fluid in these two circuits 10 and 20.

[0085] In the facility's first operating mode, the exchanger 101 operates in CO2 freezing mode, and the exchanger 103 operates in thawing mode.

[0086] CO2 freezing is related to the circulation of the cooling fluid in circuit 10 of the exchanger 101, and CO2 thawing is related to the circulation of the fluid in the exchanger 103 of the cooling / heat transfer circuit 20, which acts on heat transfer. This mode of operation allows for the recovery of the cold energy of CO2 thawing by the heat transfer / cooling circuit 20 coupled to the cooling circuit 10.

[0087] In the second operating mode (which will be described later with reference to Figure 2), the thawing of water ice by the heat transfer / cooling circuit 20 is described.

[0088] The smoke is cooled by the water freezing and thawing cycle through the exchanger 110 or exchanger 112.

[0089] In cooling mode, the smoke to be processed enters the housing 111 (which houses the cooling exchanger 112) through pipe 701 and is discharged from the housing 111 through pipe 703. Alternatively, the smoke to be processed enters the housing 109 (which houses the cooling exchanger 110) through pipe 702 and is discharged from the housing 109 through pipe 704.

[0090] The smoke to be treated enters the enclosure 111 or enclosure 109 at a temperature of preferably 2°C and is discharged from the enclosure 111 or enclosure 109 at a temperature of preferably -52°C. Thus, as stated above, the temperature values ​​mentioned herein correspond to an example of decarbonization of smoke containing 30% CO2 and 70% nitrogen by mass ratio. This corresponds to a volume concentration of 21.5% carbon dioxide (CO2) and, consequently, 78.5% nitrogen.

[0091] Next, the smoke emitted from the housing 109 or 111 is cooled to preferably -52°C to -90°C by a cooler 106 housed in housing 104 or by a ventilator 108 housed in housing 107, according to a freeze-thaw cycle.

[0092] Finally, the smoke, preferably at about 0.1 ppm(v) and preferably well-dehumidified, is discharged from the exchanger 106 or exchanger 108, and the smoke is preferably cooled to -90°C to -120°C by the exchanger 101 housed in the housing 100, or by the exchanger 103 housed in the housing 102 operating in CO2 freezing mode.

[0093] The smoke enters the exchanger 103 through pipe 709 at a temperature of preferably -90°C and is discharged from the exchanger 103 through pipe 711 at a temperature of preferably -120°C, or the smoke enters the exchanger 101 through pipe 710 and is discharged from the exchanger 101 through pipe 712.

[0094] The smoke is preferably cooled to a temperature of -120°C, dehumidified, and then carried out in circuit 700 by different branch pipes 701-712.

[0095] The operation of the equipment shown in Figure 1 is described below, which involves the coupling of the cooling circuit 10 and the heat transfer / cooling circuit 20, and preferably the operation of the two circuits 10 and 20 with the same transfer fluid, particularly preferably isopentane.

[0096] The cooling circuit 10 is circulated by the pump 1.

[0097] The refrigerant, at a temperature measured by probe 138 located downstream of pump 1, then flows into evaporator 4 of cooling circuit 40 at a preferred temperature of -95°C, and flows out of evaporator 4 at a preferred temperature of -125°C, the outlet temperature of which is measured by probe 120.

[0098] The cooling circuit 40 cools the refrigerant by counterflow, preferably to -128°C, upon the start of evaporation, and this temperature is measured by probe 41. The refrigerant then flows out of the evaporator 4, preferably at a temperature of -98°C, and this outlet temperature is measured by probe 42.

[0099] According to the CO2 freezing cycle, the refrigerant flows into either the exchanger 101 housed in the casing 100, or the exchanger 103 housed in the casing 102.

[0100] When the refrigerant circulates within the exchanger 103, solenoid valves 123 and 1111 installed at the inlet and outlet of the exchanger 103 open, and solenoid valves 121, 1110 and 221 installed at the inlet and outlet of the exchanger 101 close, and the refrigerant flows in through the branch pipe 12 preferably at -125°C, the inflow temperature of which is measured by probe 124.

[0101] The refrigerant cools the smoke and freezes the CO2 in the exchanger 103.

[0102] The typical duration of a freezing cycle is preferably one hour.

[0103] The refrigerant is preferably discharged from the evaporator 103 at a temperature of -95°C, the discharge temperature of which is measured by the probe 126, and it joins the common branch pipe 13 via the solenoid valve 1111.

[0104] Next, the refrigerant flows into the exchanger 108 at a temperature preferably of -95°C, the inflow temperature of which is measured by the probe 128, and the exchanger 108 is integrated into the housing 107 where the smoke is cooled, preferably to -90°C.

[0105] The duration of the water vapor freezing cycle is preferably about 48 hours, considering the low moisture content when the smoke enters pipe 705, with a value of 30 ppm corresponding to the saturation humidity at -52°C.

[0106] The refrigerant is preferably discharged from the exchanger 108 at a temperature of -57°C, and the discharge temperature is measured by the probe 130.

[0107] The refrigerant flows through the branch pipe 17 to the common branch pipe 19, and valve 1115 opens. The control valve 1000 closes, and solenoid valve 1117 installed in the connecting branch pipe 18 opens.

[0108] Preferably, when the volume concentration of CO2 in the smoke being processed is 21.5% or higher, the refrigerant does not enter the common branch pipe 19. This value allows the heat transfer / cooling loop 20 to provide the overall cooling capacity to cool the smoke to -52°C in the exchangers 110, 112.

[0109] Preferably, the control valve 1000 opens when the CO2 concentration of the smoke being processed is below 21.5%, allowing the refrigerant coming from branch pipe 17 and the heat transfer fluid / refrigerant coming from branch pipe 23 to mix in the common branch pipe 19, and if the heat flow rate of the heat transfer fluid / refrigerant in branch pipe 23 is insufficient at -54°C, preferably to ensure temperature control at a value in the range of -54°C.

[0110] When the heat transfer fluid / refrigerant flow rate is sufficient, the refrigerant does not pass through the common branch pipe 19 (the control valve 1000 is closed), as shown. The refrigerant then passes through the connecting branch pipe 18, is drawn in by the pump 1, and is cooled in the cooling exchanger 30, from an inlet temperature of preferably -54°C (this temperature is measured by probe 136) to an outlet temperature of -95°C (the outlet temperature is measured by probe 137).

[0111] The cooling exchanger 30 is counterflow type, with an inlet temperature preferably -98°C, measured by probe 31, and an outlet temperature preferably -59°C, measured by probe 32.

[0112] Pump 2 of the heat transfer / cooling circuit 20 preferably circulates the same transfer fluid, particularly isopentane, and the two circuits 10 and 20 alternately circulate the same exchanger 101 and 103 in each CO2 thawing and thawing cycle.

[0113] If it is necessary to supplement the heat flow of the heat transfer fluid / refrigerant, the regulating solenoid valve 1121 opens (when the exchanger 110 is in water freezing mode), or the regulating solenoid valve 1120 opens (when the exchanger 112 is in water freezing mode), allowing the same flow rate that valve 1000 sent to either of these exchangers 110, 112 to return to the branch pipe 19 of circuit 10, ensuring a temperature of -54°C (measured by probe 133 or 134).

[0114] Due to the flow rate difference, the flow rate of the refrigerant / heat transfer fluid from circuit 20 returns to pump 2 via branch pipe 26.

[0115] The heat transfer / cooling circuit 20 is so named because it provides heat to defrost the CO2 in exchanger 101 or 103, resulting in a lower temperature in exchanger 110 or 112. This gain is an indirect gain, as it allows the return temperature of the refrigerant to the branch pipe 22 to be as low as possible, preferably -54°C, when the circuit 20 provides the overall cooling capacity for exchanger 110 or 112.

[0116] Circuit 20 cools the smoke in the exchangers 110 and 112 and cools the water to freeze it, and this recovery of cold energy is associated with CO2 thawing, resulting in a direct gain.

[0117] The following explanation describes the process of thawing CO2, following the circulation of the transfer fluid along circuit 20.

[0118] At the outlet of the exchanger 5 of the cooling system 50, the temperature measured by the probe 141 is preferably -5°C, which is the temperature at which CO2 thawing is possible.

[0119] The solenoid valve 203 of branch pipe 201 is open, and similarly, the solenoid valve 221 of branch pipe 223 is also open. The solenoid valve 204 of branch pipe 202 is closed, and similarly, the solenoid valve 225 of common branch pipe 24 is also closed because the exchanger 103 is in freezing mode. The transfer fluid flows into the exchanger 101 in thawing mode, preferably at -5°C, and its temperature is measured by probe 122 at the inlet of the exchanger 101, with solenoid valves 121, 1110 and 204 closed.

[0120] The exchanger 101 is preferably at an average temperature of -110°C at the start of thawing, and the housing 100 is placed under vacuum at the start of the CO2 thawing cycle.

[0121] The transfer fluid is cooled by heating the exchanger, causing the CO2 to sublimate and the pressure in the enclosure to gradually rise, preferably to 520 kPa. This is the triple point pressure of CO2, at which point the CO2 transitions from solid to gaseous phase at -56°C.

[0122] The transferred fluid flows out of the branch pipe 223 via the solenoid valve 221 and joins the reservoir 28 via the common line 24.

[0123] Considering that the sublimation of CO2 from -120°C to -56°C corresponds to one-third of its melting energy, the average temperature of the transferred fluid in reservoir 28 is approximately -62°C, which is measured by two probes 2210 and 2311, which are located at the inlet and outlet of reservoir 28, respectively.

[0124] The storage of the transfer fluid in reservoir 28 ensures a stable flow rate of the heat transfer / cooling fluid for the freezing operation of the exchanger 110 or 112.

[0125] When the solenoid valve 231 opens, the transfer fluid flowing out of the reservoir 28 via the branch pipe 23 becomes a refrigerant.

[0126] This fluid joins the branch pipe 19 and cools the exchanger 110. This is because the solenoid valve 1118 of the branch pipe 29 opens and the solenoid valve 1119 of the branch pipe 21 closes.

[0127] The exchanger 110 is preferably a finned tube type exchanger, and the smoke circulating through the fins is cooled from 2°C (its temperature is measured by probe 71) to preferably -52°C (its temperature is measured by probe 73).

[0128] The refrigerant circulating in the tube preferably enters at -64°C (its temperature is measured by probe 131) and preferably exits at -5°C (its temperature is measured by probe 133), joining the branch pipe 25 via the open control valve 216, at which point the control valve 215 is closed.

[0129] The heat transfer fluid joins the pump 2 via line 26, and in this operation, the exchanger 5 does not need to cool the heat transfer / cooling fluid.

[0130] The cooling / heat transfer circuit 20 recovers cold energy from CO2 thawing and transfers this energy to cool the smoke from 2°C to -52°C.

[0131] Preferably, as soon as the volume concentration of CO2 in the gas mixture being treated reaches 21.5% or more, the heat flow rate of the heat transfer fluid / refrigerant from the cold energy recovered from CO2 thawing is sufficient to ensure all cooling requirements are met.

[0132] To give another example, if the volume concentration of CO2 in the mixture of gases being processed is 14%, the heat transfer / cooling circuit 20 provides 60% of the cooling requirement from 2°C to -54°C, and the remaining 40% is provided by the cooling circuit 10.

[0133] In this case, the adjustment valve 1000 is opened by the command system 800, thereby controlling the temperature measured by probe 133 or 134 to -5°C.

[0134] The flow rate of pump 1 is adjusted in freezing mode to ensure that the cooling requirements of exchangers 101 or 102 and 106 or 108 are met.

[0135] The cooling capacity associated with CO2 thawing is recovered by the heat transfer / cooling circuit 20 at the point where the gas mixture is cooled in the exchanger 110 or 112, resulting in a considerable amount of energy savings.

[0136] The operation of the cooling / heat transfer circuit 20 will be explained with reference to Figure 2, on the one hand, regarding the thawing of the exchangers 110 and 112 for cooling the smoke, and on the other hand, regarding the freezing of the water in the exchangers 106 and 108.

[0137] In Figure 2, the elements of circuits 10 and 20 associated with switches 101 and 103 are not shown for simplification.

[0138] In Figure 2, the circuit 20 shown in Figure 1 is complemented by three branch pipes 27, 36, and 37.

[0139] The branch pipe 27 of circuit 20 includes a branch pipe 209 for connecting to the branch pipe 21 of circuit 10. The solenoid valve 1001 is located in the connecting branch pipe 209.

[0140] The branch pipe 27 of circuit 20 includes a branch pipe 210 for connecting to the branch pipe 29 of circuit 10. The solenoid valve 1002 is located in the connecting branch pipe 210.

[0141] Upstream of the connection point with the branch pipe 210, the branch pipe 27 of the circuit 20 is connected to the branch pipe 26, and is continuously equipped with a regulating solenoid valve 1003, a switch 8, and a pump 33.

[0142] The two probes 321 and 322 enable the measurement of the fluid temperature at the inlet and outlet of the exchanger 8.

[0143] Pump 33 in branch pipe 27 takes in a portion of the return flow rate of line 26, which is regulated by a control solenoid valve 1003, and the refrigerant / heat transfer fluid is heated in exchanger 8, preferably to 15°C, and alternately defrosts exchangers 110 and 112.

[0144] The heat transfer fluid flow rate is controlled by the solenoid valve 1002 in branch pipe 210 or the solenoid valve 1001 in branch pipe 209 at the inlets of exchangers 110 and 112, and by the valve 216 in branch pipe 214 or the valve 215 in branch pipe 213 at the outlets of exchangers 110 and 112.

[0145] The branch pipe 37 of circuit 20 includes a branch pipe 207 for connecting to the branch pipe 15 of circuit 10. The solenoid valve 1006 is located in this connecting branch pipe 207.

[0146] The branch pipe 37 of circuit 20 includes a branch pipe 208 for connecting to the branch pipe 14 of circuit 10. The solenoid valve 1005 is located in this connecting branch pipe 208.

[0147] Upstream of the connection point with the branch pipe 208, the branch pipe 37 of the circuit 20 is connected to the branch pipe 26 and is continuously equipped with a regulating solenoid valve 1004, a switch 7, and a pump 35.

[0148] The two probes 143 and 144 enable the measurement of the fluid temperature at the inlet and outlet of the exchanger 7.

[0149] The branch pipe 36 of circuit 20 includes a branch pipe 226 for connecting to circuit 10 at the outlet of the exchange 108. The solenoid valve 212 is located in this branch pipe 226.

[0150] The branch pipe 36 of circuit 20 includes a branch pipe 227 for connecting to circuit 10 at the outlet of the exchange 106. The solenoid valve 211 is located in this branch pipe 227.

[0151] Upstream of the connection point with the branch pipe 227, the branch pipe 36 of the circuit 20 is connected to the branch pipe 26.

[0152] Pump 35 in branch pipe 37 takes in a portion of the return flow rate from line 26, which is regulated by a control solenoid valve 1004, and the refrigerant / heat transfer fluid is heated in exchanger 7, preferably to 15°C, and alternately defrosts exchangers 106 and 108.

[0153] The heat transfer fluid flow rate is controlled by the solenoid valve 1005 of branch pipe 208 or the solenoid valve 1006 of branch pipe 207 at the inlets of exchangers 106 and 108, and by the valve 211 of branch pipe 227 and the valve 212 of branch pipe 226 at the outlets of exchangers 106 and 108.

[0154] The branch pipe 36 is a return branch pipe for the heat transfer fluid to the branch pipe 26. This branch pipe 36 is supplied by the branch pipe 227 when the solenoid valve 211 opens when the exchanger 106 is thawed, or by the branch pipe 226 when the solenoid valve 212 opens when the exchanger 108 is thawed.

[0155] The ventilators 7 and 8 are preferably heated by the circuit 60 coming from the cooler.

[0156] The exchanger 6 takes heat from the circuit 60 on the circuit 39 in which the fluid / refrigerant is circulated by the pump 34.

[0157] The outlet of the exchanger 7 is connected to the inlet of the exchanger 8 by a branch pipe 38. Three solenoid valves 351, 352, and 353 are located in the branch pipe 38.

[0158] The outlet of the exchanger 8 is connected to the inlet of the exchanger 7 by a branch pipe 43. The solenoid valve 354 is located in the branch pipe 43.

[0159] Circuit 60 is connected to line 43 by a first branch pipe, and a pump 34 and a solenoid valve 341 are installed on the first branch pipe. Circuit 60 is connected to line 43 by a second branch pipe, and a solenoid valve 342 is installed on the second branch pipe.

[0160] The valve sets 341, 342, 351, 352, 353, and 354 allow for alternating supply to either the exchanger 7 or the exchanger 8.

[0161] As explained above, exchanger 112 is in defrost mode, and exchanger 110 is in defrost mode.

[0162] The total flow rate of the heat transfer / cooling fluid needs to be doubled. This is because the circuit of branch pipe 21 requires this additional flow rate by activating the pump 33 of branch pipe 27 to defrost the exchanger 112.

[0163] In defrost mode, the exchanger 112 is initially placed at a preferred average temperature of -27°C, and the heat transfer fluid gradually heats the exchanger, melting the water ice deposited on the fins of the exchanger.

[0164] When the head loss threshold on the smoke circuit is exceeded (measured by a differential pressure sensor (not shown)), triggering the defrost cycle of the exchanger 112, the control command system 800 opens the regulating valve 1003 on the branch pipe 27, opens the valve 1001 located on the branch pipe 209, and similarly opens the solenoid valve 215 located on the branch pipe 213, and closes the valve 1002.

[0165] The control command system 800 doubles the flow rate of pump 2, and this flow rate is confirmed by the flow meter 200.

[0166] Next, branch pipes 209 and 210 are supplied with the same flow rate, one used to cool branch pipe 210 and the other used to transfer heat to branch pipe 209.

[0167] The circuit 60 operating in the cooler provides the heat necessary for thawing by providing the required flow rate at 20°C (the temperature of which is measured by a temperature probe 61), thereby heating the heat transfer fluid, preferably isopentane, from a variable temperature (preferably -30°C) to preferably +15°C, the temperature of which is measured by a temperature probe 331.

[0168] Pump 34 circulates a suitable heat transfer fluid (e.g., potassium acetate) at 20°C in the exchanger 8, with two solenoid valves 352 and 342 open and four solenoid valves 341, 351, 353, and 354 closed.

[0169] The pump 33 in the branch pipe 27 is activated to draw in the heat transfer fluid flow rate and is also regulated by a control valve 1003 that is adjusted to pass half of the return flow rate to the exchanger 8.

[0170] The return to branch pipe 25 is via the solenoid valve 215 of branch pipe 213.

[0171] In the defrost mode of the exchangers 110 and 112, the flow rate measured by the flow meter 200 of the branch pipe 26 is therefore twice the flow rate of these exchangers without defrosting.

[0172] The cooling flow rate of the cooling circuit 50 itself increases, providing a cooling capacity at -10°C (measured by temperature probe 51) and preferably flowing out at +3°C (measured by temperature probe 52), which probes serve as an indicator for the control command system 800 to adjust the flow rate of the cooling system 50.

[0173] The thawing time for the exchanger 110 or 112 is preferably short, about 30 minutes, compared to about 4 hours.

[0174] When the temperature reaches 15°C, as indicated by probe 134, the control command system 800 stops pump 33, closes control valves 1001 and 1003, closes solenoid valve 215, and reduces the flow rate of pump 2 by half.

[0175] The defrosting of exchanger 106 or 108 is carried out according to the same principle, but defrosting is preferably performed once every 48 hours, and the control command system 800 gives priority to the defrosting of exchanger 110 or 112. This is because exchangers 106 and 108 can be on standby, thus avoiding simultaneous defrosting of both exchangers in the branch pipe 26.

[0176] Preferably, the exchanger 106 is in freezing mode and the exchanger 108 is in thawing mode, with an initial average temperature of approximately -70°C.

[0177] The heat transfer fluid is preferably isopentane, which heats the exchanger and melts the water ice deposited on the fins of the exchanger.

[0178] Triggered by the smoke exceeding a head loss threshold on the circuit (measured by a differential pressure sensor (not shown)), and in response to the initialization of the defrost cycle of the exchanger 108, the control command system 800 opens the regulating valves 1004 and 1006 on the branch pipe 207, and similarly opens the solenoid valve 212 located on the branch pipe 226, thereby doubling the flow rate of the pump 2.

[0179] Circuit 60 provides the heat necessary for thawing by providing the required flow rate at 20°C (measured by temperature probe 61), thereby heating the heat transfer fluid (preferably isopentane) in the exchanger 7 from a temperature of preferably -60°C to +15°C, the temperature of which is measured by probe 144.

[0180] Pump 34 circulates a potassium acetate heat transfer fluid in the exchanger 7, preferably at 20°C, with solenoid valves 351, 352, and 342 closed and solenoid valves 341, 353, and 354 open.

[0181] The pump 35 of the branch pipe 37 is activated to draw in a heat transfer fluid flow rate regulated by a control valve 1004, which is adjusted to pass half of the return flow rate from the branch pipe 26 to the exchanger 7.

[0182] The return to branch pipe 36, which is connected to branch pipe 26, is done via the solenoid valve 212 of branch pipe 226, and at this time, solenoid valves 1115 and 211 are closed.

[0183] The cooling flow rate of the cooling circuit 50 increases, preferably providing a cooling capacity at -10°C (the temperature of which is measured by a temperature probe 51), and at best, preferably at +3°C (the temperature of which is measured by a temperature probe 52), which probe serves as an indicator to the control command system 800 for adjusting the flow rate of the cooling system 50.

[0184] The thawing time is clearly shorter to be advantageous, at about 30 minutes, while the thawing time is about 48 hours, and consequently, when the temperature of probe 130 reaches 15°C, the control command system 800 stops pump 35, closes control valves 1004 and 1006, closes solenoid valve 212, and reduces the flow rate of pump 2 by half.

[0185] Also, pump 34 will stop.

[0186] The return branch pipe of circuit 20 transfers cooling capacity to the heat transfer / cooling circuit through the thawing of water at exchangers 106 and 108 on the one hand, and at exchangers 110 and 112 on the other hand. This cooling capacity contributes to the cooling of the gas mixture or the cooling system, and the cold air generated by the thawing of exchangers 106, 108, 110, and 112 is recovered by the cooling / heat transfer circuit.

Claims

1. A process for treating smoke containing water vapor and carbon dioxide, and optionally also containing nitrogen oxides, wherein the process freezes water and optionally contains nitrogen dioxide NO ２ The process includes a first step of cooling the smoke to be processed by freezing the water contained in the cooled smoke, the first step of which generates cooled smoke; the process includes a second step of cooling and dehumidifying the cooled smoke by freezing the water contained in the cooled smoke, the second step of which generates dehumidified smoke; the process includes a third step of cooling and decarbonizing the dehumidified smoke by freezing the carbon dioxide contained in the dehumidified smoke to form carbon dioxide ice, and optionally also freezing nitrogen oxides contained in the dehumidified smoke, each of the three steps of processing the smoke being performed by one of a pair of exchangers The process is carried out such that the transfer fluid circulates within each exchanger, with each of the pair of exchangers entering a freezing mode for cooling the smoke, while the other exchanger enters a thawing mode for water ice or carbon dioxide ice formed during a previously performed cooling step, the transfer fluid performing a cooling function within the exchanger in the freezing mode, the transfer fluid performing a heat transfer function within the exchanger in the thawing mode, the transfer fluid recovering cold energy to sublimate and melt the carbon dioxide ice obtained in the third cooling and decarbonization step, and in the first processing step, this cold energy is transferred to cool the smoke, the transfer fluid having a triple point where its temperature is below -125°C.

2. The process according to claim 1, characterized in that the transfer fluid comprises isopentane or isohexane.

3. The process according to claim 1 or 2, characterized in that a transfer fluid circulates within a cooling circuit, a transfer fluid circulates within a heat transfer / cooling circuit, the heat transfer / cooling circuit recovers cold energy to sublimate and melt the carbon dioxide ice obtained in the third cooling and decarbonization step, and in the first processing step, this cold energy is transferred to cool the smoke.

4. The process according to claim 3, comprising: measuring the carbon dioxide concentration of the smoke processed and cooled in the first processing step; comparing the measured carbon dioxide concentration with a threshold, wherein a predetermined flow rate of the heat transfer / cooling circuit provides a cooling capacity to cool the smoke to a target temperature in the first cooling step relative to this threshold; and mixing the transfer fluid of the cooling circuit with the transfer fluid of the cooling / heat transfer circuit when the measured carbon dioxide concentration is less than the threshold, wherein the flow rate of the resulting mixture is substantially equal to the predetermined flow rate.

5. The process according to any one of claims 3 to 4, wherein in the exchanger of the third step of cooling and decarbonizing the smoke, the transfer fluid of the heat transfer / cooling circuit circulates alternately with the transfer fluid of the cooling circuit in the exchanger, the transfer fluid of the cooling circuit ensures that the smoke is cooled and the carbon dioxide is frozen in the exchanger, and the transfer fluid of the heat transfer / cooling circuit ensures that the carbon dioxide is thawed in the exchanger.

6. The process according to any one of claims 3 to 5, wherein in the exchanger of the third step of cooling the smoke to be processed, the transfer fluid of the heat transfer / cooling circuit circulates alternately in the exchanger with the transfer fluid of the cooling circuit, and the transfer fluid of the cooling circuit partially ensures, or does not at all, the cooling of the smoke and the freezing of water into ice in the exchanger, and the transfer fluid of the heat transfer / cooling circuit partially or completely ensures the cooling of the smoke and the freezing of water, thereby performing a cooling function by transferring the recovered cold when the carbon dioxide thaws during the third step, and the transfer fluid of the heat transfer / cooling circuit performs a heat transfer function when the ice in the exchanger thaws.

7. The process according to any one of claims 3 to 6, characterized in that, in the exchanger of the second step of cooling and dehumidifying the smoke, the transfer fluid of the heat transfer / cooling circuit circulates alternately with the transfer fluid of the cooling circuit in the exchanger, ensuring that the transfer fluid of the cooling circuit freezes water so as to cool the smoke and turn into water ice in the exchanger, and ensuring that the transfer fluid of the cooling circuit / heat transfer thaws the water ice in the exchanger.

8. The process according to any one of claims 3 to 7, characterized in that the same transfer fluid circulates within the cooling circuit and the heat transfer / cooling circuit.

9. A device for processing smoke containing water vapor and carbon dioxide, and optionally nitrogen oxides, wherein the device comprises a first pair of exchangers (110, 112) for a first step of cooling the smoke to be processed by freezing water, in which the first step generates cooled smoke; the device comprises a second pair of exchangers (106, 108) for a second step of cooling and dehumidifying the cooled smoke by freezing the water contained in the cooled smoke, in which the second step generates dehumidified smoke; the device cools and decarbonizes the dehumidified smoke by freezing the carbon dioxide contained in the dehumidified smoke into carbon dioxide ice, and optionally also freezing nitrogen oxides contained in the dehumidified smoke. For step 3, the device comprises a third pair of exchangers (101, 103), in which the transfer fluid circulates within each exchanger (110, 112, 106, 108, 101, 103), with each exchanger of the pair entering a freezing mode for cooling the smoke, while the other exchanger enters a thawing mode for water ice or carbon dioxide ice formed during a previously performed cooling step, the transfer fluid performing a cooling function within the exchanger in the freezing mode, the transfer fluid performing a heat transfer function within the exchanger in the thawing mode, the transfer fluid recovering cold energy to sublimate and melt the carbon dioxide ice obtained in the third cooling and decarbonization step, and in the first processing step, transferring this cold energy to cool the smoke, the transfer fluid having a triple point temperature below -125°C.

10. The device according to claim 9, comprising a cooling circuit (10) through which a transfer fluid circulates and a heat transfer / cooling circuit (20) through which a transfer fluid circulates, wherein the heat transfer / cooling circuit (20) recovers cold energy to sublimate and melt the carbon dioxide ice obtained in the third cooling and decarbonization step, and in the first processing step, transfers this cold energy to cool the smoke.

11. The device according to claim 9 or 10, further comprising: means for measuring the carbon dioxide concentration of the smoke being processed and cooled in the first pair of exchangers (110, 112) in the first processing step; means for comparing the measured carbon dioxide concentration to a threshold, wherein a predetermined flow rate of the heat transfer / cooling circuit provides a cooling capacity to cool the smoke to a target temperature in the first cooling step relative to this threshold; and means for mixing the transfer fluid of the cooling circuit (10) with the transfer fluid of the cooling / heat transfer circuit (20) when the measured carbon dioxide concentration is less than the threshold, wherein the flow rate of the resulting mixture is substantially equal to the predetermined flow rate.

12. The device according to any one of claims 9 to 11, characterized in that the transfer fluid comprises isopentane or isohexane.

13. The device according to any one of claims 10 to 12, characterized in that the same transfer fluid circulates within the cooling circuit (10) and the heat transfer / cooling circuit (20).

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