FR3033397A1 - PROCESS FOR COMPRESSING AND COOLING A GASEOUS MIXTURE - Google Patents

Abstract

In a method of compressing and cooling a gaseous mixture (120) to a final temperature, the gaseous mixture is cooled by a fluid (111) resulting from a process implementing a regenerative active magnetic refrigeration cycle , the average flow rate of heat transfer fluid flowing through at least one regenerator (103A) from the hot source to the cold source being greater than the average flow rate of heat transfer fluid flowing through at least one other regenerator (103B) from the cold source to the hot source and the final temperature being greater than the desublimation temperature of a component of the gas mixture during its cooling.

Description

The present invention relates to a method of compression and cooling. The present invention is, in particular, relating to the compression of gas in association with a regenerative active magnetic refrigeration system (in English: Active Magnetic Regenerative Refrigeration or AMRR) for use in particular for a process for separating a mixture gaseous, for example air, subambient or even cryogenic or a process for liquefaction of air gas, for example, nitrogen, oxygen or argon. The final temperature reached by cooling may in some cases be a subambient or cryogenic temperature. To produce an air gas, it is known to use the cryogenic route and use the following steps in particular: compression of the ambient air, purification of the air with water and CO2 by adsorption, cooling of the air air in a brazed aluminum heat exchanger to a temperature close to its dew point, separation by distillation in one or more column (s) of one or more oxygen-enriched fractions and one or more fraction (s) enriched with nitrogen, heating of these fractions against the flow of air in the brazed aluminum exchanger. Percentages for purities in this document are molar percentages. Magnetic refrigeration relies on the use of magnetic materials having a magnetocaloric effect. Reversible, this effect results in a variation of their temperature when they are subjected to the application of an external magnetic field. The optimal ranges of use of these materials are in the vicinity of their Curie temperature (Tc). Indeed, the higher the magnetization variations, and hence the magnetic entropy changes, the higher the changes in their temperature. The magnetocaloric effect is said to be direct when the temperature of the material increases when it is put in a magnetic field, indirect when it cools when it is put in a magnetic field. The remainder of the description will be made for the direct case, but indirect case translation is obvious to those skilled in the art. There are several thermodynamic cycles based on this principle. A typical magnetic refrigeration cycle consists of i) magnetizing the material to increase its temperature, ii) cooling the constant magnetic field material to reject heat, iii) demagnetizing the material to cool it, and iv) to heat the constant magnetic field material (usually zero) to capture the heat. A refrigeration device is a thermodynamic device making it possible to transfer a quantity of heat from a medium considered as a "transmitter", referred to as a "cold source", from which the heat is extracted to a medium considered as a "receiver" said "source where the heat is supplied, the cold source being at a colder temperature than the hot source.

A magnetic refrigeration device uses elements of magnetocaloric material, which generate heat when magnetized and absorb heat when demagnetized. It can implement a magnetocaloric material regenerator to amplify the temperature difference between the "hot source" and the "cold source": it is called regenerative active magnetic refrigeration. This effect is described in the 2005 Lebouc Engineer's Techniques article entitled "Magnetic Refrigeration". It is known to use the magnetocaloric effect to provide cold to a subambient temperature separation process in EP-A-2551005, US-A5249424 or US-A-6502404.

EP-A-2551005 discloses a magnetocaloric refrigeration system associated with a CO2 capture process using a Brayton cycle. This patent poses a major problem as to how to avoid the deposition of ice on the tubes of the exchanger when the temperature is lowered below the ambient temperature (between 35 ° C and -4 ° C) to reach -50 ° C. ° C to -60 ° C. Such operating conditions are particularly unsuitable for compact heat exchangers which have smaller hydraulic diameters than tube and shell heat exchangers. US-A-6502404 discloses several regenerative active magnetic refrigeration systems applied to cryogenic processes but in the case of combination with a heat exchanger over a large temperature gradient, generates either substantial irreversibilities by mixing a hot fluid with a cold fluid, ie large temperature differences and therefore significant irreversibilities.

US-A-5249424 discloses a regenerative active magnetic refrigeration system applied to a hydrogen liquefier which solves the problems of temperature deviation. On the other hand, since the compression of the gas is at a very low temperature, the overall efficiency of the compression system (including the system used to produce the liquid nitrogen) remains low. The present invention proposes to considerably increase the compression yield by solving the problems mentioned above. In particular, one of the objects of the invention is to propose a hybrid compression system associating, for example, a multi-stage centrifugal compressor with a regenerative active magnetic refrigeration system so as to obtain an exergy yield of compression greater than 80% ( equivalent to an isothermal efficiency higher than 80%). An ambient temperature is the temperature of the ambient air in which the process is located, or a temperature of a cooling water circuit related to the air temperature. A subambient temperature is at least 10 ° C below room temperature, for example below 0 ° C. A cryogenic temperature is below -50 ° C. Desublimation is the transition from the gaseous state to the solid state without going through the liquid state. According to one object of the invention, there is provided a method for compressing and cooling a gaseous mixture comprising at least one component capable of desublimation, in which the gaseous mixture is cooled to a final temperature by a fluid derived from a process employing a regenerative active magnetic refrigeration cycle for transferring a quantity of heat from a cold source from which the heat is extracted to a heat source where the heat is supplied, the cold source being at a temperature colder than the hot source in which a heat transfer fluid circulates through at least a first regenerator from the hot source to the cold source and heat transfer fluid circulates through at least one second regenerator from the cold source to the source hot and the gas mixture is compressed before being cooled and / or after having been cooled in a compression stage 3033397 4 c characterized in that: i) the average flow rate of heat transfer fluid flowing through the at least one first regenerator from the hot source to the cold source is greater than the average flow rate of heat transfer fluid flowing through the at least one second regenerator from the cold source to the hot source and ii) the final temperature is higher than the desublimation temperature of the constituent of the gaseous mixture capable of desublimation. According to other optional features: the cooling of the gaseous mixture cools the mixture up to a temperature above 0 ° C. or below 0 ° C., subambient, or even cryogenic, - said gas mixture is removed from the water by a process chosen from adsorption, absorption and / or permeation - the subambient temperature up to which the gaseous mixture is cooled is less than 0 ° C - the heat transfer fluid from the cold source of the magnetic refrigeration cycle active regeneration is a liquid at low pressure, preferably less than 10 bar or 5 bar - its exergy efficiency is greater than 80%. the ratio between the quantity of heat Qr during the cooling of the fluid and the work Wc supplied during the compression of the gaseous mixture downstream or upstream of the cooling is between half the exergy efficiency of the refrigeration system and 1 - the Wr power supplied to the refrigerating cycle to provide cooling Qr is much lower than the power Wc compression of the gas mixture downstream 25 or upstream of the cooling, in particular less than 20% or even 15% or even 10%. the discharge temperature of the compression stage of the gaseous mixture downstream or upstream of the cooling is greater than the ambient temperature - the water is removed by absorption - the process is integrated in an inverted Rankine liquefaction cycle the process is integrated in an inverted Brayton cycle. The gaseous mixture of the air - the gaseous mixture is essentially nitrogen, which may contain traces of CO2 and / or water, for example, less than 1 ppm - the gaseous mixture is essentially oxygen, which may contain traces of CO2 and / or water, for example, less than 1 ppm -the gaseous mixture is compressed in a compressor upstream of the cooling - the inlet temperature of the compressor upstream of the cooling is higher at 0 ° C, below 0 ° C or cryogenic 10 - the gas mixture is compressed in a compressor downstream of the cooling - the inlet temperature of the compressor downstream of the cooling is greater than 0 ° C, lower than 0 ° C According to another aspect of the invention there is provided a method of liquefying and / or separating a gaseous mixture, for example air comprising a compression process as described above - in a process air separation by cryogenic distillation, the cryogenic distillation is carried out in a column operating at a first pressure thermally coupled to a column operating at a second pressure plus base that the first pressure, air is compressed in n stages of compression to the first pressure and then is sent to the column operating at the first pressure, n being strictly less than 3, that is to say 1 or 2. Figure 1 shows the state of the art of compression on a factory separation of gases from the air.

Figure 2 shows a first variant of the invention. Figure 3 shows a second variant of the invention. Figure 4 shows the comparison between the exergy yield of the invention compared to the state of the art. Figure 1 which is described in FR-2777641 illustrates an air distillation plant 1 with argon production. This plant 1 essentially comprises a double column 2 for the distillation of air, a column 3 for producing impure argon, said column of mixture, a column 4 for producing pure argon, said denitrogenation column, a main line of heat exchange 5, a main air compressor 6 to be distilled and an air purification apparatus to be distilled 7. The double column 2 comprises a medium pressure column 8 operating at an average pressure, for example 5 bar absolute, a low pressure column 9, operating at a low pressure lower than the average pressure, for example a pressure slightly greater than 1 bar absolute, and a main evaporator 10. The impure argon production column 3 comprises a top condenser 12 to partially condense the impure argon at the top of the column 3. The pure argon production column 4 comprises a top condenser 13 and a tank vaporizer 14. A gas line 16, said The argon quencher connects an intermediate point of the low pressure column 9 to the tank of the impure argon production column 3, from the bottom of which a liquid return line 17 joins the column 9, at approximately the same temperature. The line 16 connects an outlet of the overhead condenser 12 of the column 3 to an intermediate level of the substantially pure argon production column 4. This pipe withdraws the non-condensed part in the condenser 12 from the impure argon at the top of the column 3. This pipe 19 passes successively from the column 3, a heat exchanger 20, for condensing the gaseous impure argon, and an expansion valve 21, to relax this condensed impure argon. The gaseous air to be distilled is compressed by the compressor 6 in this example a 3-stage MAC centrifugal compressor 6A, 6B and 6C, each followed by 3 water coolers 106A, 106B and 106C. The water (not shown) evacuates the heat of compression by heating up and is then cooled in an atmospheric tower (not shown) in direct contact with the ambient air at a close temperature but typically greater than 5 ° C. humid ambient air. The gaseous air comprises water and CO2 as it is compressed in the compressor 6. The compressed gaseous air is then purified with water and CO2, for example by adsorption, in the apparatus 7, is divided into two primary streams. These primary streams contain very small amounts of water and carbon dioxide, for example less than 0.1 ppm for an impurity breakthrough, averaging less than 5 ppm of each impurity. The first primary air stream is cooled in the main heat exchange line 5 and then divided into two secondary streams. The first secondary stream is injected into the vat of the medium pressure column near its dew point. The second secondary stream is sent to the vessel vaporizer 14 of the pure argon production column 4, where this second secondary stream is liquefied by vaporizing the bottom argon of this column 4. The liquid thus produced is sent by 10 a line 23 to the tank of the medium pressure column 8. The second primary flow of compressed and purified air is compressed by a compressor BAC 230 in this example, a centrifugal compressor 4 stages 230A, 230B, 230C and 230D, each followed a water cooler 232A, 232B, 232C and 232D. The water (not shown) exhausts the heat of compression by heating up and is then cooled in an atmospheric tower (not shown) in direct contact with ambient air at a near temperature but typically greater than 5 ° C. humid temperature of the ambient air. This second primary flow of air is then liquefied at the crossing of the main heat exchange line 5 and expanded in an expansion valve 231 substantially until the pressure prevailing in the medium pressure column 8. A first part of this flow is then injected at an intermediate level of the medium pressure column 8. The other part of this flow is sub-cooled through a heat exchanger 24, then expanded in an expansion valve 240 and injected at intermediate level 9. The vaporizer-condenser 10 vaporizes liquid oxygen in the bottom of the low pressure column 9 by condensing nitrogen at the top of the medium pressure column 8. Rich liquid (enriched with oxygen) LR is withdrawn from the tank of the medium pressure column 8, then subcooled in the heat exchanger 24 and finally divided into two streams. The first flow is sent, after expansion in an expansion valve 30 25, to an intermediate level of the low pressure column 9. The second flow is sent, after expansion in an expansion valve 26 to the condenser 12 of 3033397 8 head of column 3 for the production of impure argon, where this second stream is vaporized by condensation of impure argon at the top of column 3. The gas thus produced is returned, via line 27, to the low pressure column 9 at one level. intermediate lower than that of injection of the first flow of the rich liquid.

Lean liquid (approximately pure nitrogen) LP is taken from the upper part of the medium pressure column 8, then subcooled in the heat exchanger 24, and finally divided into three streams. The first stream is expanded in an expansion valve 30 and then injected at the top of the low pressure column 9. The second stream is expanded in an expansion valve 31 and then vaporized in the heat exchanger 20, condensing the impure argon channelized by the pipe 19, then this vaporized stream is again expanded in an expansion valve 32. This second stream is then returned by a waste pipe 33 to the heat exchanger 24, where the second stream is heated by cooling the Liquid LP and LR passing through the exchanger 24. This second stream is finally sent to the main heat exchange line 5, where the second stream is heated by participating in the cooling of the air to be distilled. The third stream of lean liquid is expanded in an expansion valve 34 before being sent to the top condenser 13 of the pure argon production column 4, where this third stream is vaporized by condensation of the impure nitrogen of 4. The gas thus produced is sent, after expansion into an expansion valve 35, into the waste pipe 33 to be heated on the one hand in the heat exchanger 24 while cooling the LP liquids. and LR and, on the other hand, in the main heat exchange line 5 by participating in the cooling of the air to be distilled. Impure or residual nitrogen NR, withdrawn from the top of the low pressure column 9, is sent to the waste pipe 33, where this impure nitrogen is heated through the heat exchanger 24, then from the line main heat exchange 5. OL liquid oxygen, withdrawn in the bottom of the low pressure column 9, is pumped by a pump 37 and then sent via a pipe 38 to the main line 30 of heat exchange 5, where this oxygen liquid is vaporized by participating in the cooling of the air to be distilled.

The medium pressure nitrogen gas NGNP is taken at the top of the medium pressure column 8 and then sent via a pipe 39 to the heat exchange line 5 to participate in the cooling of the air to be distilled. In an intermediate region of this heat exchange line 5, the medium pressure nitrogen gas 5 is divided into two streams. The first flow crosses the rest of the line 5 where it is heated then it is distributed by a production line 40, for example to feed a consumer installation 140. The second flow is expanded in a turbine 41 and sent to the waste pipe 33 at the cold end of the heat exchange line 5, to participate again in cooling the air to be distilled. NLMP medium pressure liquid nitrogen is withdrawn at the top of the medium pressure column 8 and then sent via a pipe 43 to the heat exchanger 24, where the liquid nitrogen is sub-cooled by heating the waste gases channeled by the pipe of This liquid nitrogen is then dispensed, for example by supplying, after expansion in an expansion valve 143, a storage tank 144. Arl about pure liquid argon is withdrawn in the vat of column 4 and then distributed by a production pipe 45. Impure or waste nitrogen is taken at the top of the column 4 and then discharged via a pipe 46.

The installation 1 further comprises a bypass line 48 whose inlet 49 is connected to the pipe 19, between the heat exchanger 20 and the expansion valve 21, and whose outlet 50 opens into the waste pipe. 33, just upstream of the heat exchanger 24. The example of Figure 1 shows a method using an air overpressure using a booster 230 whose inlet temperature is relatively hot, called "hot booster". On the other hand, it is well known to booster part of the supply air using a booster with an inlet temperature which is a temperature below 0 ° C, or even cryogenic, called "cold booster". For example, a part of the air can be withdrawn from the exchanger 5, 30 supercharged and returned to the exchanger before being sent to the distillation.

It is also known to compress a gas resulting from the distillation in a compressor whose inlet temperature is below 0 ° C., or even cryogenic, for example a cold nitrogen compressor. Figure 2 shows a first embodiment of the invention. The process of Figure 2 represents a compression process with a cooling step upstream and / or downstream of the compression. In other words, the compressor 130 or the compressor 131 may be optional. A gas mixture 119 is compressed in a stage n of compressor 130 to give a fluid 120 which is cooled in a heat exchanger 102 to a temperature below the wet bulb temperature of the air. to give a fluid 121 which is then compressed in a n + 1 compression stage 131 to form a compressed fluid 122. The refrigerant 111 of the exchanger 102 is derived from a regenerative active magnetic refrigeration system (in English: Active Magnetic Regenerative Refrigeration or AMRR) which will now be described. A heat transfer fluid 110 at a temperature near room temperature is oriented by an inverting device which typically operates at a frequency of between 1 and 10 Hz. The refrigerant heats up in the exchanger 102 to form the flow 113 which is returned to the magnetic refrigeration system. In a first alternating mode, the heat transfer fluid 110 passes through the valve 106A then travels a first regenerator 103A consisting of magnetocaloric material blades which has just been demagnetized, that is to say cooled. At the outlet of 103A, the heat transfer fluid is divided into a first portion 111 which constitutes a small fraction of the flow rate 110, typically between a few percent and 15%, and a second portion which will evacuate the heat of a second regenerator 103B which comes 25 to be magnetized, that is to say heated by magnets 104A and 104B on either side of the magnetocaloric materials of the regenerator placed in the air gap. The fluid leaving the regenerator 1036 passes through the valve 1056 and becomes the fluid 114 which is mixed with the fluid 113 from the exchanger 102. The formed mixture 115 passes into a circulation pump 109 to give a fluid 116 which will be 30 cooled by the ambient medium, for example in a hybrid air cooler 101 into which ambient air 130 is introduced which is optionally heated in the presence of water operating in evaporative air-cooling to give hot moist air 131. The valves 105A and 106B are closed. In a second alternate mode (not shown), the heat transfer fluid 110 passes through the valve 106B and then travels the second regenerator 103B consisting of 5 blades of magnetocaloric materials which has just been demagnetized, that is to say cooled. At the outlet of 1036, the coolant is divided into a first portion 111 which constitutes a small fraction of the flow rate 110, typically between a few percent and 15%, and a second portion which will evacuate the heat of the first regenerator 103A which has just to be magnetized, that is to say heated by magnets 104A and 104B on either side of the magnetocaloric materials of the regenerator placed in the air gap. The fluid leaving the first regenerator 103A passes through the valve 105A and becomes the fluid 114 which is mixed with the fluid 113 from the exchanger 102. The mixture 115 passes into a circulation pump 109 to give a fluid 116 which will be cooled by the ambient medium, for example in a hybrid air cooler 101 into which ambient air 130 is introduced, which is optionally heated in the presence of water operating in evaporative air-cooling to give hot moist air 131. The valves 1056 and 106A are closed. The fluid 116 heated in the cooler 101 is the coolant 110. One skilled in the art will recognize here that many variations of the invention are possible. The magnetocaloric material may be in the form of powder, beads, waves of different geometries, plates, etc. The inversion system may consist of two-way or multi-way valves, non-return valves, mechanically actuated valves. Electrically, the number of regenerators in parallel can be between 1 ("batch" system (in English "batch") with storage of the coolant) and several thousand. Figure 3 shows a second embodiment of the invention. A fluid 120 is cooled in a heat exchanger 102 at a temperature below the humid temperature of the air to give a fluid 121. In a first case, the fluid 120 corresponds to the gaseous mixture and comprises a component capable of desubling. Either the gas mixture 120 is compressed upstream of the heat exchanger 121 or the fluid 121 is compressed downstream of the heat exchanger 121, or both. In this first case, the final temperature of the cooling in the exchanger 102 is greater than the desublimation temperature of a component present in the gaseous mixture 120 compressed or to be compressed. In a second case, the fluid 121 is not the gas mixture used indirectly to cool another fluid, constituting the gaseous mixture, which will be compressed from a temperature below the humid temperature of the air but greater than the desublimation temperature of a component present in the gas mixture. Since the gaseous mixture contains the component capable of desubliming, the cooling of the gaseous mixture by the fluid 121 must not reach a temperature equal to or lower than the desublimation temperature. By against the cooling in the heat exchanger 102 can reach a temperature below the desublimation temperature, assuming that the fluid 121 does not contain a component capable of desublimer. The refrigerant 111 of exchanger 102 is derived from an Active Magnetic Regenerative Refrigeration (AMRR) refrigeration system which will now be described. A coolant 110 at a temperature near room temperature is oriented by an inverting device which typically operates at a frequency between 1 and 10 Hz.

In a first alternating mode, the coolant 110 passes through the valve 106A then travels a first regenerator 103A consisting of magnetocaloric material blades which has just been demagnetized, that is to say cooled. At the outlet of 103A, the heat transfer fluid passes through the valve 107A to give the fluid 111 which is introduced into the exchanger 102 and then divided into a first portion 113 which constitutes a small fraction of the flow rate 110, typically between a few percent and 15. %, and a second portion 112 which passes through the valve 108B and will evacuate the heat of a second regenerator 103B which has just been magnetized that is to say heated by magnets 104A and 104B on both sides magnetocaloric regenerator materials placed in the air gap. The fluid leaving the regenerator 103B passes through the valve 105B and becomes the fluid 114 which is mixed with the fluid 113 from the exchanger 102. The mixture 115 passes into a circulation pump 109 to give a fluid 116 which will be cooled by any of the fluids of the unit in which this refrigeration system integrates. It may be a fluid from the cold side of another refrigeration system. In this case, we will talk about a cascade system. In this case, the heat exchanger 101 may be in direct contact if it has been possible to choose the same heat transfer fluid for the two refrigeration systems. It can also be a fluid directly or indirectly cooled by another refrigeration system. The valves 105A, 106B, 107B and 108A are closed. In a second alternate mode (not shown), the heat transfer fluid 110 passes through the valve 106B and then travels the second regenerator 103B consisting of 10 blades of magnetocaloric materials which has just been demagnetized, that is to say cooled. At the outlet of 103B, the heat transfer fluid passes through the valve 107B to give the fluid 111 which is introduced into the exchanger 102 and then divided into a first portion 113 which constitutes a small fraction of the flow rate 110, typically between a few percent and 15% and a second portion 112 which passes through the valve 108A and will discharge heat from the first regenerator 103A which has just been magnetized, ie heated by magnets 104A and 104B on both sides of the materials. magnetocaloric regenerator placed in the gap. The fluid exiting the regenerator 103A passes through the valve 105A and becomes the fluid 114 which is mixed with the fluid 113 from the exchanger 102. The mixture 115 passes into a circulation pump 109 to give a fluid 116 which will be cooled. by any of the fluids of the unit in which this refrigeration system is integrated. It may be a fluid from the cold side of another refrigeration system. In this case, we will talk about a cascade system. In this case, the exchanger 101 may be in direct contact if it was possible to choose the same heat transfer fluid for the two refrigeration systems. It can also be a fluid directly or indirectly cooled by another refrigeration system. The valves 105B, 106A, 107A and 108B are closed. The processes of Figures 2 and 3 can be applied to the compression and cooling of a gaseous mixture to be separated by distillation at a subambient or even cryogenic temperature. In particular, the gaseous mixture may be air, a mixture having the main (or main) component (s) of carbon dioxide, carbon monoxide, hydrogen, methane, hydrogen, nitrogen, oxygen or argon. The gaseous mixture comprises at least one component, in particular carbon dioxide, which is capable of desubling. Cooling in exchanger 102 cools the gaseous mixture to a temperature above the desublimation temperature of that component, for example to -30 ° C. The heat exchanger 102 does not cool the gaseous mixture to a temperature equal to or lower than the desublimation temperature of the desublimatable component.

Preferably, in both cases of FIGS. 2 and 3, the gaseous mixture, or the air from which it is derived, has been purified to the component capable of desubliming, to remove most of this component if the gaseous mixture contains at least 30 mol% of carbon dioxide, or even at least 70% of carbon dioxide, it is necessary to remove the water it may contain upstream of the heat exchanger, if the cooling temperature must pass below 0 ° C. The cooling of FIG. 2 or 3 may be used to cool the air of FIG. 1 upstream of at least one of the compressors 6A, 6B, 6C and / or upstream of at least one of the compressors 230A, 230B, 230C, 232C, 230D and / or downstream of at least one of these compressors. It can also be used to cool another fluid in the installation. The cooling of Figure 2 or 3 can completely or partially replace cooling in one of the chillers 106A, 106B, 106C or 232A, 232B, 232C, 232D.

In the case where the invention is applied to replace at least one of the coolers 106A, 106B, 106C by downstream compressor cooling according to the invention, it becomes possible to reduce the number of compression stages by three (as in the prior art of Figure 1) to only two or even a compression stage. Here the two (or less) stages compress the air to the operating pressure of the column 8.

The cooling method of FIG. 2 or 3 can be used in the case where the compression upstream and / or downstream of the cooling is carried out in a cold booster or a cold compressor. In this case, the gas to be compressed, for example purified air or nitrogen, has very little component capable of desublishing, for example carbon dioxide, and the desublimation temperature may be less than -100. ° C, or -150 ° C. For example, for a flow rate at 5 bar containing 1 ppm of carbon dioxide, the desublimation temperature is between 160 ° C and -165 ° C. In this case, it will be understood that the cooling carried out in the heat exchanger 102 can make it possible to reach a temperature of at most -100.degree. C., or even at most -150.degree. C., depending on the concentrations and the pressures. The cold compressor or the cold booster may comprise at least two stages and the cooling of Figure 2 or 3 takes place between the two stages. Otherwise the cold compressor or the cold booster may comprise a single stage and the cooling of Figure 2 or 3 is upstream or downstream of this stage. The gaseous mixture in FIGS. 2 and 3 may be a substantially nitrogen gas flow rate or a substantially oxygen gas flow rate, containing, in both cases, traces of CO2 and / or water, for example less than 1 ppm. Figure 4 shows how a hybrid compression system associating a centrifugal compressor with a regenerative active magnetic refrigeration system so as to obtain an exergy compressive efficiency greater than 80% (equivalent to an isothermal efficiency greater than 80%). The calculations were made on the basis of a perfect gas. The polytropic yield was set at 85%. The compressor inlet temperature in the absence of refrigeration is set at 15 ° C. Curve A shows the evolution of the exergetic efficiency of the compressor-refrigeration system as a function of the temperature of the fluid 121 on the basis of FIG. 2, for a compression ratio of 2 of the compressor 131 and an exergy efficiency of the refrigeration system. 80%. It is found that the yield goes from 75.48% at 15 ° C (no refrigeration) to 83.15% at -35 ° C which represents a considerable gain. Curve B shows the evolution of the exergetic efficiency of the compressor-refrigeration system as a function of the temperature of the fluid 121 on the basis of FIG. 3 in the case where the flow rate of the fluid 112 is the same as that of 111, c that is, the flow rate of 113 is zero. In this case, the optimum yield is 79.25% at -11 ° C.

Curve C corresponds to the same assumptions as curve A but for a compression ratio of 4. It can be seen that the optimum in this case is 81.55% at -78 ° C. This means that it is possible to reduce the number of stages of a centrifugal compressor, in this case 1 instead of 2 to make a compression ratio of 4 while maintaining a higher yield compared to the basic case (75.48 %). The curve D corresponds to the same assumptions as the curve B but for a compression ratio of 4. It can be seen that the optimum in this case is 73.88% at -36 ° C. Curve E corresponds to the same assumptions as curve A but for an exergetic efficiency of the refrigeration system of 50%. It can be seen that the optimum in this case is 80.33% at -18 ° C. Even with these more pessimistic assumptions, the gain remains substantial relative to the base case (75.48%). Curve F corresponds to the same assumptions as curve B but for an exergetic efficiency of the refrigeration system of 50%. It can be seen that the optimum in this case is 77.88% at -2 ° C. The comparison curve A / curve B, curve C / curve D and curve E / curve F 20 shows the interest of FIG. 2 compared with the conventional configuration of a regenerative active magnetic refrigeration system as described, for example, by US Pat. No. 6,502,404 where the coolant leaving the cold zone is returned thereto. For the curves A, C and E, at the optimum, the ratio between the amount of heat Qr during the cooling of the fluid (difference between 120 and 121) and the work Wc of the supplied during the compression 131 is equal to the yield exergy of the refrigeration system. The effectiveness of such a system also lies in the efficiency of the exchanger 102 in terms of the temperature difference between the heat transfer fluid and the refrigerant.

Claims (12)

REVENDICATIONS1. A method of compressing and cooling a gaseous mixture comprising at least one component capable of desublimation, wherein the gaseous mixture is cooled to a final temperature by a fluid (111) from a process employing a cycle of regenerative active magnetic refrigeration for transferring a quantity of heat from a cold source (120) from which the heat is extracted to a heat source (130) where the heat is supplied, the cold source being at a heat source temperature colder than the hot source in which a coolant flows through at least a first regenerator (103A, 103B) from the hot source to the cold source and coolant flows through at least one second regenerator (103B, 103A) from the cold source to the hot source and the gas mixture is compressed before being cooled and / or after having been cooled in a compression stage characterized by the fact that: i) the average flow rate of heat transfer fluid flowing through the at least one first regenerator from the hot source to the cold source is greater than the average flow rate of heat transfer fluid flowing through the at least one second regenerator since the cold source to the hot source and ii) the final temperature is higher than the desublimation temperature of the component of the gaseous mixture capable of desublimation. 2. Method according to claim 1 characterized in that water is removed from said gas mixture by a method selected from adsorption, absorption and / or permeation and optionally the subambient temperature up to which the The gaseous mixture is cooled to below 0 ° C, or even to -100 ° C. 3. Method according to claim 1 characterized in that the heat transfer fluid from the cold source of the regenerative magnetic refrigeration cycle is a low-pressure liquid, preferably less than 10 bar or 5 bar. 4. Method according to claim 1 characterized in that its exergetic efficiency is greater than 80%. 5. Method according to claim 1 characterized in that the ratio between the amount of heat Qr during the cooling of the fluid and the work Wc provided during the compression of the gaseous mixture downstream or upstream of the cooling is between half of the Exergetic performance of the refrigeration system and 1. 6. Method according to claim 5 characterized in that the power Wr supplied to the refrigerating cycle to provide the cooling Qr is much lower than the power Wc compression of the gas mixture downstream or upstream of the cooling, especially less than 20% or 15% or even 10%. 7. Process according to claim 1, characterized in that the discharge temperature of the compression stage of the gaseous mixture downstream or upstream of the cooling is greater than the ambient temperature. 20 8. The method of claim 7 characterized in that removes the water by absorption. 9. The process of claim 1 integrated in an inverted Rankine liquefaction cycle. The method of claim 1 embedded in an inverted Brayton cycle. 11. Process for liquefaction and / or separation at subambient or even cryogenic temperature of a gaseous mixture, for example air, comprising a compression and cooling method according to one of the preceding claims. 12. Process for air separation by cryogenic distillation according to claim 11 wherein the cryogenic distillation is carried out in a column operating at a first pressure thermally coupled to a column operating at a second pressure lower than the first pressure, the air is compressed in n compression stages until the first pressure and then is sent to the column operating at the first pressure, n being strictly less than 3, ie 1 or 2.