Process and apparatus for the simultaneous production of gaseous and liquid CO2

Abstract

Title: Method and apparatus for the simultaneous production of gaseous CO2 and liquid CO2 In a method for the simultaneous production of gaseous CO2 and liquid CO2 from a gas mixture containing CO2 and at least one component lighter than CO2, in which the gas mixture (S101) is separated producing a first liquid (S108, S110) at a first pressure richer in CO2 than the gas mixture, a first portion (S110) of the first liquid is completely vaporized at the first pressure by heat exchange with the mixture forming a first gas (S115) rich in CO2, a second portion (S108) of the first liquid is completely vaporized at a second pressure lower than the first pressure by heat exchange with the mixture forming a second gas (S113) rich in CO2, the second gas is compressed in at least one stage of a compressor (C1) from the second pressure to substantially the first pressure,the first and second gases are mixed at the first pressure forming a third gas, and simultaneously the mixture is divided to produce a liquid product (S118) and a gaseous product (S116). Fig 2,

Description

Title of the invention: Method and apparatus for the simultaneous production of gaseous and liquid CO2

[0001] The present invention relates to a method and apparatus for the simultaneous production of gaseous and liquid CO2 from a gaseous mixture containing CO2 and at least one component lighter than CO2.

[0002] Many CO2-rich gas treatment process schemes with CO2 extraction exist, but most of them are based on the production of purified CO2, either entirely gaseous or entirely liquid.

[0003] The possibility of producing purified gaseous and liquid CO2 simultaneously from a CO2-rich source involves higher investments and particular attention must be paid to optimizing operating costs. An aim of this invention is to design a process capable of producing gaseous and liquid CO2 and to find the best process integration arrangement from an economic point of view offering the greatest operating flexibility between gaseous and liquid CO2 production.

[0004] FR-A-3120427 describes a method for separating a stream containing CO2 to simultaneously produce liquid CO2 and gaseous CO2, resulting from the vaporization of a flow of liquid CO2.

[0005] The present invention proposes to produce at least a portion of liquid CO2 by condensing gaseous CO2 and storing it in liquid form.

[0006] We can define:

[0007] [TAB.l] q Quantity of CO2 exported q0 Nominal quantity of CO2 produced qG Quantity of gaseous CO2 exported qL Quantity of liquid CO2 exported qLP Quantity of liquid CO2 produced by condensing gaseous CO2 zL Limit of the quantity of liquid CO2, defined by the low load limit n Number of external refrigerant cycles s Quantity of liquid CO2 to be sent to storage F, F0 Feed rate, nominal feed rate qLa Quantity of liquid, defined by excess cold zO Minimum load of a machine m% of qLP per refrigeration cycle (=q0 / n for homogeneous sharing)

[0008] So

[0009] qG + qL = q

[0010] qLP = qL + s

[0011] qLP can vary between the following values: • [0 (without LCO2 production); y (corresponding to excess cold)] • [zL; q (without GCO2 production)], zL>y with the lower limit zL discussed below.

[0012] A liquid storage is operated to ensure the entire range of liquid production qLe[y; zL] or [0; zL], for other discontinuous ranges or for CO2 production beyond the load capacity (q>qO for feed F0 for example), the liquid storage will be filled as described below.

[0013] It should be noted that since there is excess frigories due to the vaporization of liquid carbon dioxide withdrawn from the bottom of the stripping column, it is possible to withdraw a quantity qLa of LCO2 produced, for example by the column, with little effect on the design of the heat exchanger.

[0014] In this example qLa constitutes between 7 and 8% of the liquid CO2 production. If all the liquid production from the column bottom is vaporized in the heat exchanger HEX1, there is an excess of cold at the hot end of the exchanger. The quantity yO is the maximum quantity of CO2 that can be withdrawn from the column bottom, respecting the AT specification in the exchanger HEX1. [Fig.l] shows the variation of the AT with the temperature in the exchanger HEX1.

[0015] According to an object of the invention, there is provided a method for the simultaneous production of gaseous CO2 and liquid CO2 from a gas mixture containing CO2 and at least one component lighter than CO2 in which the gas mixture is separated by partial condensation and / or distillation and / or solidification producing a first liquid at a first pressure richer in CO2 than the gas mixture, a first part of the first liquid is completely vaporized at the first pressure by heat exchange with the mixture forming a first gas rich in CO2, a second part of the first liquid is completely vaporized at a second pressure lower than the first pressure by heat exchange with the mixture forming a second gas rich in CO2, the second gas is compressed in at least one stage of a compressor from the second pressure to substantially the first pressure,the first and second gases are mixed at the first pressure forming a third gas, and simultaneously,

[0016] i) a first fraction of the third CO2-rich gas is at least partially liquefied at the first pressure, by heat exchange with at least one re-cycle refrigeration, producing a third CO2-rich liquid which is pressurized by a pump to constitute at least a portion of the liquid CO2 produced and / or a second fraction of the third CO2-rich gas is liquefied at the first pressure, by heat exchange with at least one refrigeration cycle and sent at least occasionally to storage and

[0017] ii) a third fraction of the third CO2-rich gas has not been liquefied and constitutes a gaseous product of the process.

[0018] According to other optional features:

[0019] • the third fraction of the third CO2-rich gas is compressed by at least one stage of a compressor, preferably of the centrifugal type, from substantially the first pressure to a fourth pressure.

[0020] • the second gas is compressed in at least one stage of a compressor and the third fraction is compressed in at least one stage of the same compressor, preferably of the centrifugal type, downstream of the at least one stage where the second gas is compressed.

[0021] • at least the first part of the first liquid is vaporized without having been expanded or pressurized.

[0022] • the mixture is separated in at least one phase separator and at least one liquid of at least one phase separator is sent to a stripping column, the bottom liquid of the column constituting the first liquid and the column operating at the first pressure.

[0023] • the second part of the first liquid, possibly coming from the tank of the column, is expanded in a valve to the second pressure, before being vaporized and compressed.

[0024] • the column operates at between 10 and 20 bars abs, or even between 10 and 20 bars abs

[0025] • a third part of the first liquid also constitutes a liquid product of the process.

[0026] • according to a variant a) a first flow rate of the first and / or second fraction of the third CO2-rich gas is at least partially liquefied by heat exchange with the at least one refrigeration cycle, the at least one refrigeration cycle comprising a cycle compressor driven by an electric motor, producing a CO2-rich liquid if the electricity sent to the motor has a price below a threshold and

[0027] • according to a variant b) a second flow rate of the first and / or second fraction of the third CO2-rich gas, lower than the first flow rate, or even zero, is liquefied at least partially by heat exchange with the at least one refrigeration cycle, the at least one refrigeration cycle comprising a cycle compressor driven by an electric motor, producing the CO2-rich liquid if the electricity sent to the motor has a price above the threshold.

[0028] • according to a variant a) a first flow rate of the first and / or second fraction of the third CO2-rich gas is at least partially liquefied by heat exchange with the at least one refrigeration cycle, the at least one refrigeration cycle comprising a cycle compressor driven by an electric motor, producing a CO2-rich liquid if a first percentage of the electricity sent to the motor comes from at least one renewable source and

[0029] • according to a variant b) a second flow rate of the first and / or second fraction of the third CO2-rich gas, lower than the first flow rate, or even zero, is liquefied at least partially by heat exchange with the at least one refrigeration cycle, the at least one refrigeration cycle comprising a cycle compressor driven by an electric motor, producing the CO2-rich liquid if a second percentage, lower than the first percentage, or even zero, of the electricity sent to the motor comes from at least one renewable source. • the ratio between the flow rates of the first and third fractions is variable and / or the ratio between the flow rates of the second and third fractions is variable. • according to a variant i) according to a first step of the device, the ratio between the flow rates of the first and third fractions is x: 1 and

[0030] i) according to a second step of the apparatus, the ratio between the flow rates of the first and third fractions is y:1, y being greater than x. • according to a variant i) according to a first step of the device, the ratio between the flow rates of the second and third fractions is x: 1 and

[0031] ii) according to a second step of the apparatus, the ratio between the flow rates of the second and third fractions is y:1, y being greater than x. • all of the second part of the first liquid completely vaporized at a second pressure is compressed and mixed with the first part of the first liquid completely vaporized at the first pressure. • a gas coming from a gaseous storage headspace is sent upstream of the at least one compression stage or upstream of a point where the first and second gases mix at the first pressure forming the third gas or mixes with the second gas upstream of its compression to the first pressure.

[0032] According to another object of the invention, there is provided an apparatus for the simultaneous production of gaseous CO2 and liquid CO2 from a gaseous mixture containing CO2 and at least one component lighter than CO2 comprising a unit for separation by partial condensation and / or distillation and / or solidification to separate the gaseous mixture, means for leaving the separation unit a first liquid at a first pressure richer in CO2 than the gas mixture, a heat exchanger, means for sending a first portion of the first liquid to vaporize completely at the first pressure in the heat exchanger, by heat exchange with the mixture forming a first gas rich in CO2, means for sending a second portion of the first liquid to vaporize completely at a second pressure lower than the first pressure in the heat exchanger by heat exchange with the mixture forming a second gas rich in CO2, a compressor, means for sending the second gas to compress in at least one stage of the compressor from the second pressure to substantially the first pressure, means for mixing the first and second gases at the first pressure forming a third gas, and

[0033] a) means for liquefying a first fraction of the third CO2-rich gas at least partially at the first pressure, comprising at least one refrigeration cycle and capable of producing a third CO2-rich liquid and a pump for pressurizing the third liquid to constitute at least a portion of the liquid CO2 produced and / or

[0034] b) storage and means for liquefying a second fraction of the third CO2-rich gas at the first pressure, by heat exchange comprising at least one refrigeration cycle and means for sending the second liquefied fraction at least occasionally to storage and

[0035] c) means for outputting a third fraction of the third CO2-rich gas as a gaseous product of the process, these means not comprising liquefaction means.

[0036] The invention will be described in more detail with reference to the figures, where:

[0037] [Fig.2] represents a method according to the invention.

[0038] [Fig-2] represents a method according to the invention in which a mixture S101 of CO2 and at least one lighter component, e.g. hydrogen, helium, oxygen, nitrogen, methane, carbon monoxide, ethane or another hydrocarbon is separated by partial condensation and distillation.

[0039] The mixture S101 with a flow rate F, a pressure PI and a temperature T1 is cooled and partially condensed in a heat exchanger HEX1 of the wave brazed plate type. The partially condensed flow S102 at a temperature T2 is sent to a phase separator forming a gas S104 and a liquid S103. The gas S104 is heated in the exchanger HEX1. The liquid S103 is expanded in a valve EXP1 to a pressure P2 and a temperature T3 and sent to the top of a column T100. The top gas S106 from the column T100 enriched in the at least one lighter component and depleted in CO2 is heated in the exchanger HEX1 and joins the flow S104 forming a flow S107.

[0040] The bottom liquid of column T100 constitutes in part the liquid product of the CO2 LIQ process. A portion SI 11 of the liquid is vaporized in the exchanger HEX1 at the pressure P2 between 10 and 20 bar abs of the column and returned in gaseous form to the column T100 in the bottom to reboil the column. Another flow SI 10 of the bottom liquid at the pressure P2 and a temperature T4 vaporizes in the exchanger HEX1 without having been expanded forming a flow SI 15. Another flow of the bottom liquid S108 is expanded in a valve EXP2 forming a flow S109 at a pressure P3 and a temperature T5 and vaporized in the heat exchanger HEX1 at the pressure P3 lower than P2. The vaporized flow SI 13 is compressed in a compressor Cl, cooled in a cooler forming the flow SI 14 up to the pressure P2 which is that of the column and the two vaporized flows SI 14, SI 15 are mixed forming a third gas flow at a pressure between 10 and 20 bars abs.

[0041] The third gas flow is divided into two parts. One part can directly constitute the gaseous product at pressure P2 or otherwise this part can be sent at least in part to a compressor C2, cooled forming a flow SI 16 of gaseous CO2 at a pressure P5, serving as product of the process.

[0042] Another part qLP of the third gas flow is sent at least in part to a heat exchanger HEX3 to be condensed at the pressure P2 by at least one closed refrigeration cycle 100, involving a cycle compressor C3, a cooler, a valve, a phase separator. The refrigerant of the cycle, for example NH3, is compressed by the cycle compressor C3, cooled, expanded in the valve forming a two-phase flow, the two-phase flow separating in a phase separator, the gas being sent upstream of the compressor and the liquid being vaporized in the exchanger HEX3.

[0043] The gas flow SI 17 leaves condensed from the exchanger HEX3 at the pressure P2 which is that of the column T100, is pressurized by a pump up to a pressure higher than P2 which can be supercritical, forming a flow SI 18. At least a part of the condensed flow SI 18 can be sent as flow s to a liquid storage S and / or used as liquid product without passing through the storage S. In the event of a need for production above the capacity of the column, a flow ds can be withdrawn from the storage S to provide the missing quantity of liquid.

[0044] The production of a higher quantity (qLP>qLa) of purified LCO2 requires the use of at least one external refrigeration cycle 100, using a refrigerant such as NH3 to cool a portion of the product (mixture of SI 14 and SI 15) to condense a portion of the GCO2 in the heat exchanger HEX 3 at a pressure that differs from that of the column only by pressure losses. The resulting condensed CO2 production LCO2 S117 can be pumped up to a higher pressure forming a liquid flow SI 18.

[0045] The scheme regarding the ratio of GCO2 / LCO2 fractions depends on the minimum possible flow rate for the CO2 compressor C2 and the minimum possible flow rate for the refrigeration cycle compressor C3. Depending on the required flexibility, it could be interesting to carry out the C2 and / or C3 compression by several compressors in parallel (2*50% capacity or 3*33% capacity ...) or several cycle compressors in parallel

[0046] For a liquid production qLP>zL, the quantity qLPi is sent to the heat exchanger HEX 3 to be condensed against the refrigeration cycle. The cycle compressor C3 must manage a variation of the refrigerant flow rate depending on the CO2 flow rate qLP to be condensed. Thus the value of zL is defined by the minimum flow rate of the refrigerant compressor C3.

[0047] Several external cycles or several refrigerant compressors can be used in parallel to optimize the flexibility of the scheme by reducing the flow rate of the cycle or cycles or of the compressor or compressors. It is also possible to close one or more cycles or compressors simultaneously.

[0048] The minimum quantity of gaseous CO2 to be produced can be limited by the minimum flow rate that can be compressed by compressor C2. The limitation can be eliminated by recycling the compressed CO2 after expansion (line R) in a recycling valve at the compressor inlet. This solution increases energy consumption.

[0049] S storage can be used to make the production of liquid and gaseous CO2 more flexible.

[0050] The discontinuous production of liquid CO2 by the cryogenic unit can be compensated by a storage of liquid CO2 connected to the distillation apparatus.

[0051] In one example, one can: • Fill the storage • when qL < zL / n (the quantity of LCO2 to be exported corresponds to (a) the load of the at least one refrigerant cycle if below its or their minimum flow rate; and the at least one refrigerant cycle / compressor is not stopped but is operated at its maximum flow rate). Thus qLP = zL=qL+s and / or • after a fraction when at least one cycle / compressors are not stopped. Thus qLP = qL+s and / or • at night when electricity costs are lower and / or • during periods when renewable energy is available • Empty storage • When at least one refrigerant cycle is stopped to continue producing a minimum amount of LCO2). Thus qL = qLP +s and / or

[0052]

[0053]

[0054]

[0055]

[0056] • Whatever the liquefier load, increase the L / G ratio of CO2 produced in order to operate at an optimum OPEX. Thus qL > qLP and / or • When the liquefier operates at reduced load With gaseous and liquid CO2 production below nominal production and / or With nominal gaseous and liquid CO2 production (F <F0, qL + qG = qO) et / ou • When the liquefier is operated at nominal gas and liquid production and higher gas and liquid production is required (F=F0, qL>qLP) [TAB.2] (example) CAS Feedstock Liquid CO2 Production Gaseous CO2 Production Storage 0 - Nominal F0 qLO qGO 0 to zL / n OR sO 1 - Reduced load F < F0 qL0=qLP+s 1 qGO -si 2 - Increased production F0 qL2=qLP+s2 qGO -s2 3 - Reduced production F0 qL3=qLP-s3 qGO s3 In case 1, liquid si coming from storage S compensates for the lack of condensed liquid due to the reduction in load. In case 2, liquid s2 coming from storage S completes the quantity of condensed liquid. In case 3, liquid s3 goes to storage S because it is not required for production. A BOG gas coming from the gaseous sky of storage S can be sent upstream of compressor C2 and / or Cl or upstream of the point where gases S114, S115 mix. • Advantages of the proposed solution • Flexibility of production, gaseous G and / or liquid L with a variable L / G ratio • Multi-fluid heat exchanger with stable, even constant, operating conditions • Separation apparatus with distillation column and / or exhaustion having stable, even constant, operating conditions Low pressure compressor with stable, even constant, operating conditions regardless of the gas / liquid production ratio Liquid storage provides more liquid than that provided by separation at any given time Vaporized gas from storage can be recycled to be liquefied and returned to storage

Claims

Claims

1. A method for the simultaneous production of gaseous CO2 and liquid CO2 from a gas mixture containing CO2 and at least one component lighter than CO2, wherein the gas mixture (S 101) is separated by partial condensation and / or distillation and / or solidification producing a first liquid (S 108, SI 10) at a first pressure richer in CO2 than the gas mixture, a first portion (SI 10) of the first liquid is completely vaporized at the first pressure by heat exchange with the mixture forming a first gas (SI 15) rich in CO2, a second portion (S 108) of the first liquid is completely vaporized at a second pressure lower than the first pressure by heat exchange with the mixture forming a second gas (SI 13) rich in CO2, the second gas is compressed in at least one stage of a compressor (Cl) from the second pressure to substantially the first pressure,the first and second gases are mixed at the first pressure forming a third gas, and simultaneously i. a first fraction (S 117, S118) of the third CO2-rich gas is at least partially liquefied at the first pressure, by heat exchange with at least one refrigeration cycle, (100) producing a third CO2-rich liquid which is pressurized by a pump to constitute at least a part of the liquid CO2 produced and / or a second fraction of the third CO2-rich gas is liquefied at the first pressure, by heat exchange with at least one refrigeration cycle and sent at least occasionally to a storage (S) and ii. a third fraction (SI 16) of the third CO2-rich gas has not been liquefied and constitutes a gaseous product of the process.,

2. A method according to claim 1 wherein the third fraction (SI 16) of the third CO2-rich gas is compressed by at least one stage of a compressor (C2), preferably of the centrifugal type, from substantially the first pressure to a fourth pressure.

3. A method according to claim 2 wherein the second gas is compressed in at least one stage of a compressor (Cl) and the third fraction is compressed in at least one stage (C2) of the same compressor, preferably of the centrifugal type, downstream of the at least one stage where the second gas is compressed.

4. A method according to claim 1, 2 or 3 wherein at least the first portion (SI 10) of the first liquid is vaporized without having been expanded or pressurized.

5. A method according to claim 1, 2, 3 or 4 wherein the mixture is separated in at least one phase separator and at least one liquid from at least one phase separator is sent to a stripping column (T100), the bottom liquid of the column constituting the first liquid and the column operating at the first pressure.

6. Method according to claims 4 and 5 in which the second part of the first liquid, possibly coming from the tank of the column (T100), is expanded in a valve (EXP 2) to the second pressure, before being vaporized and compressed.

7. A method according to any preceding claim wherein a third portion (qLa) of the first liquid also constitutes a liquid product of the method.

8. Method according to one of the preceding claims in which a. a first flow rate of the first and / or second fraction of the third CO2-rich gas is liquefied at least partially by heat exchange with the at least one refrigeration cycle, the at least one refrigeration cycle comprising a cycle compressor driven by an electric motor, producing a CO2-rich liquid if the electricity sent to the engine has a price below a threshold and / or and b. a second flow rate of the first and / or second fraction of the third CO2-rich gas, lower than the first flow rate, or even zero, is liquefied at least partially by heat exchange with the at least one refrigeration cycle, the at least one refrigeration cycle comprising a cycle compressor driven by an electric motor, producing the CO2-rich liquid if the electricity sent to the engine has a price above the threshold.

9. Method according to one of the preceding claims in which a. a first flow rate of the first and / or second fraction of the third CO2-rich gas is at least partially liquefied by heat exchange with the at least one refrigeration cycle, the at least one refrigeration cycle comprising a cycle compressor driven by an electric motor, producing a CO2-rich liquid if a first percentage of the electricity sent to the engine comes from at least one renewable source and b. a second flow rate of the first and / or second fraction of the third CO2-rich gas, lower than the first flow rate, or even zero, is at least partially liquefied by heat exchange with the at least one refrigeration cycle, the at least one refrigeration cycle comprising a cycle compressor driven by an electric motor, producing the CO2-rich liquid if a second percentage, lower than the first percentage, or even zero, of the electricity sent to the engine comes from at least one renewable source.

10. Method according to one of the preceding claims in which the ratio between the flow rates of the first and third fractions is variable and / or the ratio between the flow rates of the second and third fractions is variable.

11. Method according to one of the preceding claims in which all of the second part (SI 13) of the first liquid completely vaporized at a second pressure is compressed and mixed with the first part (SI 15) of the first liquid completely vaporized at the first pressure.

12. Method according to one of the preceding claims in which a gas (BOG) coming from a gaseous sky of the storage (S) is sent upstream of the at least one compression stage (Cl, C2) or upstream of a point where the first and second gases mix at the first pressure forming the third gas or mixes with the second gas upstream of its compression to the first pressure.

13. Apparatus for the simultaneous production of gaseous CO2 and liquid CO2 from a gaseous mixture containing CO2 and at least one component lighter than CO2 comprising a unit for separation by partial condensation and / or distillation and / or solidification (T2, T100) for separating the gaseous mixture, means for exiting the unit separating a first liquid (S 108) at a first pressure richer in CO2 than the gas mixture, a heat exchanger (HEX1), means for sending a first portion (SI 10) of the first liquid to vaporize completely at the first pressure in the heat exchanger, by heat exchange with the mixture forming a first gas rich in CO2, means for sending a second portion (S 108) of the first liquid to vaporize completely at a second pressure lower than the first pressure in the heat exchanger by heat exchange with the mixture forming a second gas rich in CO2 (SI 14), a compressor (Cl), means for sending the second gas to compress in at least one stage of the compressor from the second pressure to substantially the first pressure, means for mixing the first and second gases at the first pressure forming a third gas, and a. means (100, HEX3) for liquefying a first fraction of the third CO2-rich gas at least partially at the first pressure, comprising at least one refrigeration cycle and capable of producing a third CO2-rich liquid and a pump for pressurizing the third liquid to constitute at least a portion of the liquid CO2 produced and / or b. a storage (S) and means for liquefying a second fraction of the third CO2-rich gas at the first pressure, by heat exchange comprising at least one refrigeration cycle and means for sending the second liquefied fraction at least occasionally to the storage and c. means for outputting a third fraction (SI 18) of the third CO2-rich gas as a gaseous product of the process, these means not comprising liquefaction means.

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