FR3010509A1 - METHOD AND APPARATUS FOR SUBAMBIAN TEMPERATURE SEPARATION - Google Patents

Abstract

In a subambient temperature separation process, a mixture of fluid (A, B) at subambient temperature is sent to a separation column system comprising at least one separation column (3, 5), a fluid enriched in a component lighter mixture comes out of the head of a column of the system and a fluid enriched in a heavier component is withdrawn from the tank of a column of the system, the heat sink of a heat pump (MC, MC1, MC2 , MC3) using the magnetocaloric effect is thermally connected to a first zone (1) of a column of the system and the heat source of the same heat pump is thermally connected to a second zone (2) of the same or of another column of the system.

Description

The present invention relates to a method and apparatus for separation by separation at subambient temperature, or even cryogenic. The separation may be separation by distillation and / or dephlegmation and / or absorption. The equipment used for this separation will be called "column". Thus, a column may for example be a distillation or absorption column. Reduced to its simplest expression, it can be a phase separator. Otherwise a column can also be a device where a deflegmation takes place. Magnetic refrigeration is based 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). In fact, the higher the magnetization variations, and consequently 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 rest of the description will be made for the direct case, but the transposition to the indirect case 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) heating the material. constant magnetic field material (usually zero) to capture heat.

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 active regenerative magnetic refrigeration.

It is known to use the magnetocaloric effect to provide cold to a process of air separation by cryogenic distillation. US-A-6502404 describes the use of the magnetocaloric effect to provide cold (necessary to ensure the cooling of the process) to a cryogenic process for separating gas from air, the separation energy being conventionally provided by the pressurized air which makes it possible to operate the vaporizer-condenser of the double column (the low pressure column can be reduced to a simple vaporizer in the case of a nitrogen generator). The present invention addresses the problem of heat transfer from one place of a separation apparatus by distillation and / or dephlegmation and / or subambient absorption considered as a cold source to another location of said apparatus considered as a hot spring. It has long been known to use the same circuit to provide both heat reboiler of a distillation column and condenser frigories of the same column. US-A-2916888 shows an example for hydrocarbon distillation. A heat pump is a thermodynamic device for transferring a quantity of heat from a medium considered as "transmitter" said "cold source" from which the heat is extracted to a medium considered as "receiver" said "hot source Where the heat is supplied, the cold source being at a cooler temperature than the hot source. The conventional cycle used in the state of the art for this type of application is a thermodynamic cycle of compression - cooling (condensation) - relaxation - heating (vaporization) of a refrigerant. Figure 12 of the document "ENGINEERING TECHNIQUES - Magnetic Refrigeration 2005" shows a gain of a factor 2 on the coefficient of performance of a refrigeration system using a magnetic cycle compared to the conventional cycle. 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. According to an object of the invention, there is provided a subambient or even cryogenic temperature separation process, in which a subambient or even cryogenic fluid mixture is sent to a separation column system comprising at least one separation column. , a fluid enriched in a lighter component of the mixture exits the head of a column of the system and a fluid enriched in a heavier component is withdrawn from the tank of a column of the system, wherein the cold source of a heat pump using the magnetocaloric effect is thermally connected, directly or indirectly, to a first zone of a column of the system and the heat source of the same heat pump is thermally connected, directly or indirectly, to a second zone of the same or another column of the system, the minimum temperature of the first zone being lower than the maximum temperature of the second zone.

According to other optional objects: a gas of the first zone condenses at least partially and is optionally returned to the first zone; a liquid of the second zone is vaporized at least partially and is optionally returned to the second zone; at least one fluid coming from the first or second zone in direct contact with a magnetocaloric material of a heat pump using the magnetocaloric effect; the heat exchange is at least partly carried out between a fluid coming from the first or second zone and a heat transfer fluid having been in contact with a magnetocaloric material of a heat pump using the magnetocaloric effect through an exchanger; - The heat exchange is at least partly carried out between a fluid from the first or second zone and a heat transfer fluid having been in contact with a magnetocaloric material of a heat pump using the magnetocaloric effect through an intermediate heat transport circuit ; the mixture is air, the heat pump using the magnetocaloric effect condenses in the first zone a gas enriched in nitrogen and vaporizes in the second zone a liquid enriched in oxygen; a plurality of heat pumps is implemented, heat being supplied to a plurality of heat pumps from a first zone and / or heat from a plurality of heat pumps being sent to a second zone; the mixture has as main components carbon monoxide and / or carbon dioxide and / or hydrogen and / or methane and / or nitrogen; to produce a liquid in a column tank containing more than 97 mol% of oxygen, argon is removed from the liquid withdrawn in the bottom of the column by separating an intermediate gas from the column enriched in argon in a distillation column for produce a richer flow of argon; a plurality of heat pumps using the magnetocaloric effect, one of which serves to condense an intermediate gas taken at a higher level of the column and another which serves to vaporize an intermediate liquid taken at a lower level of the column; - To produce a column-bottom liquid containing less than 96.5 mol% oxygen in which a heat pump using the magnetocaloric effect is used to vaporize an intermediate liquid taken at a lower level of the column. According to another object of the invention, there is provided a separating apparatus at subambient or even cryogenic temperature, comprising a system of separation columns comprising at least one separation column in which a mixture of subambient or even cryogenic fluid is sent, a conduit for withdrawing a fluid enriched in a lighter component of the mixture of the head of a column of the system, and a conduit for withdrawing a fluid enriched in a heavier component of the tank of a column of the system, in wherein the cold source of a heat pump using the magnetocaloric effect is thermally connected, directly or indirectly, to a first zone of a column of the system and the heat source of the same heat pump being thermally connected directly or indirectly , at a second zone of the same or another column of the system, the arrangement of the first and second zones in the column or the columns being such that the minimum temperature of the first zone is lower than the maximum temperature of the second zone.

According to other optional aspects, the apparatus comprises: means for sending a gas from the first zone to condense; means for sending the condensed gas to the first zone; means for sending a liquid from the second zone to vaporize at least partially; means for sending the vaporized liquid to the second zone; means for putting in direct contact at least one fluid coming from the first or second zone with a magnetocaloric material of a heat pump using the magnetocaloric effect; the heat exchange is at least partly carried out between a fluid coming from the first or second zone and a heat transfer fluid having been in contact with a magnetocaloric material of a heat pump using the magnetocaloric effect through an exchanger; the heat exchange is at least partly carried out between a fluid coming from the first or second zone and a heat transfer fluid having been in contact with a magnetocaloric material of a heat pump using the magnetocaloric effect through a heat transfer circuit intermediate; - the mixture is air; the heat pump using the magnetocaloric effect is capable of condensing a gas enriched in nitrogen in the first zone and vaporizes in the second zone a liquid enriched in oxygen; a plurality of heat pumps, means for supplying heat to a plurality of heat pumps from a first zone and / or means for sending heat from a plurality of heat pumps to a second zone; to produce a column-bottom liquid containing more than 97 mol% oxygen, a distillation column for removing argon from the liquid withdrawn in the bottom of the column by separating an intermediate gas from the argon-enriched column for produce a richer flow of argon; several heat pumps using the magnetocaloric effect, one of which serves to condense an intermediate gas taken at a higher level of the column and another which serves to vaporize an intermediate liquid taken at a lower level of the column. The invention will be described in more detail with reference to the figures.

In FIG. 1, a mixture containing at least A, B cooled to a subambient temperature, or even cryogenic, separates in a column 3 to form a fluid, possibly gaseous, rich in volatile components A and a fluid, possibly liquid, rich in less volatile components B. If it is desired to transfer heat from a first zone 1 between the second and third gas-liquid contactor sections, to a second zone 2 between the first and second contactor sections gas-liquid, this can be done using a heat pump using the magnetocaloric effect MC, the temperature of the first zone 1 being substantially lower than that of the second zone 2, that is to say that the exchange of heat between the two zones through a simple exchanger can not be done either because the temperature difference is negative or because the temperature difference is too small. The first zone 1 is thermally connected, directly or indirectly to the heat pump source MC using the magnetocaloric effect, and the second zone 2 is thermally connected, directly or indirectly, to the heat source of the same heat pump MC using the magnetocaloric effect.

In FIG. 2, a mixture containing at least A, B cooled to a subambient temperature, or even cryogenic, separates in a column 3 to form a fluid, possibly gaseous, rich in volatile components A and a fluid, possibly liquid, rich in components. less volatile B. A mixture containing at least C, D cooled to a subambient temperature, or even cryogenic, separates in a column 5 to form a fluid, possibly gaseous, rich in volatile components C and a fluid, possibly liquid, rich in components less volatile D. If it is desired to transfer heat from a first zone 1 between the second and first gas-liquid contactor sections of column 3 to a second zone 2 between the second and third sections of gas-liquid contactors from column 5, this can be done using a heat pump using the magnetocaloric effect MC. The first zone 1 is thermally connected directly or indirectly to the heat pump's heat source using the magnetocaloric effect MC, and the second zone 2 is thermally connected, directly or indirectly, to the heat source of the same heat pump MC using the magnetocaloric effect. In Figure 3, a compressor 7 compresses a flow A, B (for example air considered as a mixture of oxygen and nitrogen mainly). The compressed flow rate is cooled in a cooler 9 and purified in a purification unit 11 to remove impurities (if present). The purified flow rate is cooled in a heat exchanger 13 to a cryogenic temperature and is divided into two flow rates 23, 25. A flow 23 is sent to column 3 in gaseous form and the remainder 25 is cooled or at least partially liquefied. in an exchanger 27. The cooled or at least partially liquefied flow is sent to column 3. Column 3 has a head condenser 15 and a bottom reboiler 17. The condenser 15 is considered as the first zone 1 and the reboiler 17 as the second zone 2, the heat being transferred from the first zone 1 to the second zone 2 by means of a heat pump using the magnetocaloric effect MC1. The cooling or liquefaction at least in part of the flow 25, which partially compensates for the electrical or mechanical energy introduced by the heat pump operation using the magnetocaloric effect MC1 can be achieved directly or indirectly by means of a pump. heat using the magnetocaloric effect MC4 using a cooling fluid 51, typically ambient air or cooling water or any other refrigeration system, for example with a thermodynamic compression / expansion cycle.

In Figures 4 and 5, heat is transferred from the head of the medium pressure column of a double air separation column to the vessel of the low pressure column thereof. In Figure 4, a compressor 7 compresses a flow A, B (for example, air as a mixture of oxygen and nitrogen mainly). The compressed flow rate is cooled in a cooler 9 and purified in a purification unit 11 to remove impurities (if present). The purified flow is divided in two. A portion 23 cooled in a heat exchanger 13 at a cryogenic temperature is sent to the bottom of the medium pressure column 3. The remainder 123 is supercharged in a booster 41, partially cooled in the heat exchanger 13, and then expanded in a turbine The expanded air is sent to the low pressure column 5, thermally connected directly or indirectly to the medium pressure column 3 through a heat pump using the magnetocaloric effect MC. Other means of producing cold, other than the blowing turbine, can be envisaged.

A B-enriched liquid flow (oxygen) and an A-enriched liquid flow (nitrogen) are withdrawn from the medium pressure column 3 and sent to the low pressure column 5. In Figure 4, column 3 is not head condenser in the column and column 5 has no bottom reboiler in the column. Nitrogen gas 47 is withdrawn from column 3 and divided into two. A portion 49 is heated in the exchanger 13. The remainder 51 is sent to the heat pump using the magnetocaloric effect MC where it condenses (possibly partially) and the condensed nitrogen is returned to the top of the column 3. From the liquid oxygen of the column 5 tank is also sent to the heat pump using the magnetocaloric effect MC where it vaporizes (possibly partially) before being returned to the column 5. Thus the heat pump using the The magnetocaloric effect MC replaces both the head condenser and the bottom reboiler, allowing in particular to reduce the total height of the column system 3.5. Gaseous oxygen 53 is withdrawn from column 5 as product, warms up in exchanger 13 and is compressed in compressor 55. It is obvious to those skilled in the art that liquid oxygen can be drawn off of the column either as a liquid product, or to be pumped, and then vaporized in the exchange line 13 against overpressed air. Nitrogen 57 is withdrawn from the head of the low pressure column 5, heated in the subcooler 45 and in the exchanger 13 before serving at least partly to the regeneration of the unit 11.

Figure 5 shows a more conventional variant where the column 3 has a top condenser 15 and the column 5 a bottom reboiler 17. The heat transfer between the two is done indirectly by means of a heat pump using the effect magnetocaloric MC, a heat transfer fluid from the heat pump using the magnetocaloric effect MC supplying the condenser, a heat transfer fluid from the heat pump using the magnetocaloric effect MC supplying the vaporizer, the two heat transfer fluids can be the same. Compared to the conventional configuration of the double column, the use of a heat pump using the magnetocaloric effect as illustrated in FIGS. 3, 4 and 5 to operate the distillation makes it possible to gain up to about 20 % of energy, in particular by reducing the flow pressure A, B in the compressor 7 necessary for separation. Figure 6 shows an apparatus similar to that of Figure 3 except that it comprises an argon producing column 103 fed from column 3. This argon column 103 can actually produce an argon-enriched fluid or otherwise, pour the argon-enriched fluid into a residual flow. The condenser of the argon column 103 is fed with a liquid from the column 3, withdrawn on "equivalent distillation trays" around the introduction of liquid air, above the introduction of air 23. Said liquid is vaporized (at least partially) in the condenser of the argon column 103 to ensure refrigeration of the argon column 103, and then reintroduced in the column 3 under the air supply 23. The column of Argon 103 is connected to column 3 under the reintroduction of said vaporized liquid. In this case, the oxygen 29 withdrawn from the bottom of the column 3 can have a purity of more than 97 mol%. Figure 7 shows an apparatus similar to that of Figure 6 where heat pumps using the magnetocaloric effect MC2, MC3 replace the argon producing column 103 and the overhead condenser thereof. Part of the heat exchanged at the condenser 15 of the column 3 is transferred directly or indirectly to the heat pump's heat source using the magnetocaloric effect MC3. The heat pump using the magnetocaloric effect MC3 has as a hot source a liquid withdrawn between the liquid air inlet and the gaseous air inlet 23, which is at least partially vaporized and re-introduced in the column 3 under the supply of gaseous air 23. The heat pump using the magnetocaloric effect MC2 has as cold source a gas withdrawn below the level of said re-introduction, which is at least partially condensed and re-introduced at the level of said re-introduction. --introduction. Part of the heat exchanged at the vaporizer 17 of the column 3 comes directly or indirectly from the heat source of the heat pump using the magnetocaloric effect MC2. The complement of the heat exchanged at the condenser 15 of the column 3 is transferred directly or indirectly to the cold source of the heat pump using the magnetocaloric effect MC1. The complement of the heat exchanged at the vaporizer 17 of the column 3 comes directly or indirectly from the heat source of the heat pump using the magnetocaloric effect MC1. Heat pumps using the magnetocaloric effect MC1, MC2 and / or MC3 can be wholly or partly combined in one device. It (which) has an energetic performance identical to FIG. 6, in the case where the fluid enriched in argon is rejected in a residual flow. It allows an energy saving of about 7% compared to FIG. 3. In this case, the oxygen 29 withdrawn from the bottom of the column 3 can have a purity of more than 97 mol%. Figure 8 shows an apparatus similar to that of Figure 3 but including an intermediate reboiler. In this case, heat is transferred indirectly from the condenser 15 to both reboilers 17, 71, through two heat pumps using the magnetocaloric effect MC1, MC2. Part of the heat exchanged at the condenser 15 of column 3 is transferred directly or indirectly to the heat pump's heat pump source using magnetocaloric effect MC2. The heat exchanged at the intermediate reboiler 71 situated under the gaseous air inlet 23 comes directly or indirectly from the heat source of the heat pump using the magnetocaloric effect MC2. The complement of the heat exchanged at the condenser 15 of the column 3 is transferred directly or indirectly to the cold source of the heat pump using the magnetocaloric effect MC1. The heat exchanged at the vaporizer 17 of the column 3 comes directly or indirectly from the heat pump using the magnetocaloric effect MC1. In this case, the oxygen 29 withdrawn from the bottom of the column 3 can have a purity of less than 96.5 mol%. Heat pumps using the magnetocaloric effect MC1 and MC2 can be wholly or partly combined in one device.

Compared to the conventional configuration of the double column with double vaporizer in the low pressure column, the use of heat pumps using the magnetocaloric effect as illustrated in Figure 8 to operate the distillation allows to win up to about 20% energy.

Claims (5)

REVENDICATIONS1. Process for separation at subambient or even cryogenic temperature, in which a mixture of fluid (A, B) at subambient or even cryogenic temperature is sent to a system of separation columns comprising at least one separation column (3, 5), a fluid enriched in a lighter component of the mixture leaves the head of a column of the system and a fluid enriched in a heavier component is withdrawn from the tank of a column of the system, wherein the cold source of a pump to heat (MC, MC1, MC2, MC3) using the magnetocaloric effect is thermally connected, directly or indirectly, to a first zone (1) of a column of the system and the heat source of the same heat pump is thermally connected, directly or indirectly to a second zone (2) of the same or another column of the system, the minimum temperature of the first zone being lower than the maximum temperature of the second zone. 2. The method of claim 1, wherein a gas of the first zone condenses at least partially and is optionally returned to the first zone (1). 3. Method according to claim 1 or 2, wherein a liquid of the second zone is vaporized at least partially and is optionally returned to the second zone (2). 4. Method according to claim 1, 2 or 3, wherein at least one fluid from the first or second zone (1, 2) is brought into direct contact with a magnetocaloric material of a heat pump using the magnetocaloric effect. (MC, MC1, MC2, MC3) .30. A method according to claim 1, 2 or 3, wherein the heat exchange is at least partly carried out between a fluid from the first or second zone (1, 2) and a heat transfer fluid having been in contact with a magnetocaloric material of a heat pump using the magnetocaloric effect (MC, MC1, MC2, MC3) through an exchanger. Process according to Claim 1, 2 or 3, in which the heat exchange is at least partly carried out between a fluid originating from the first or second zone (1, 2) and a heat transfer fluid having been in contact with a magnetocaloric material. a heat pump using the magnetocaloric effect (MC, MC1, MC2, MC3) through an intermediate heat transport circuit. 7. Method according to one of the preceding claims, wherein the mixture is air. 8. The method of claim 7, wherein the heat pump using the magnetocaloric effect condenses in the first zone a nitrogen-enriched gas and vaporizes in the second zone an oxygen-enriched liquid. The method according to one of the preceding claims, wherein a plurality of heat pumps (MC, MC1, MC2, MC3) is implemented, heat being supplied to a plurality of heat pumps from a first zone and / or heat from a plurality of heat pumps being sent to a second zone. Process according to one of the preceding claims, in which the mixture has as main components carbon monoxide and / or carbon dioxide and / or hydrogen and / or methane and / or nitrogen. 11. Process according to one of the preceding claims 1 to 9, in which to produce a column-bottom liquid containing more than 97 mol% of oxygen, argon is removed from the liquid withdrawn in the bottom of the column by separating a column. gas intermediate the argon enriched column in a distillation column to produce a richer argon flow. 12. Method according to one of the preceding claims, wherein one uses several heat pumps (MC, MC1, MC2, MC3) using the magnetocaloric effect, one of which serves to condense an intermediate gas taken at a higher level of the column. and another which serves to vaporize an intermediate liquid taken at a lower level of the column. Method according to one of the preceding claims 1 to 9, 11 or 12, for producing a column-bottom liquid containing less than 96.5 mol% of oxygen in which a heat pump (MC, MC1, MC2, MC3) using the magnetocaloric effect is used to vaporize an intermediate liquid taken at a lower level of the column. 14. Apparatus for separation at subambient temperature, even cryogenic, comprising a system of separation columns comprising at least one separation column (3, 5) in which a mixture of fluid (A, B) at subambient or even cryogenic temperature is sent, a pipe for withdrawing a fluid enriched in a lighter component of the mixture of the head of a column of the system and a pipe for drawing off a fluid enriched in a heavier component of the tank of a column of the system, wherein the cold source of a heat pump (MC, MC1, MC2, MC3) using the magnetocaloric effect being thermally connected, directly or indirectly at a first zone (1) of a column of the system and the hot source of the same heat pump being thermally connected, directly or indirectly, to a second zone (2) of the same or another column of the system , the arrangement of the first and second zones in the column or columns being such that the minimum temperature of the first zone is lower than the maximum temperature of the second zone.