Method and apparatus for cooling and separating a flow of co2 containing a first component

Abstract

A method for cooling and separating a CO2 stream (1) containing at least one first component having a dew point between 0 and 15°C at a first pressure, in which the stream is cooled by indirect heat exchange in a single exchanger (R3) with water and at least one liquid CO2 stream (19) which vaporizes forming a CO2 stream at a third temperature, in order to condense the at least one first component (8) present in the CO2 stream.

Description

[0001] Method and apparatus for cooling and separating a CO2 stream containing a first component

[0002] The present invention relates to a method and apparatus for cooling and separating, for example drying, a CO2 flow containing at least a first component, which may be water, methanol, ammonia, having a condensation temperature higher than that of CO2.

[0003] CO2 may contain at least one other component that is lighter and / or heavier than CO2.

[0004] Flue gases treated by CO2 capture processes often produce a water-saturated CO2 product, available at low pressure, whereas it is often necessary to produce it purified in water and under pressure (due to the specification of the product or its integration into a CO2 liquefier). It is then necessary to compress and dry it.

[0005] The present invention provides an optimization of an arrangement for partial condensation of water from a wet CO2 fluid by cooling against water and liquid CO2.

[0006] This invention can be applied in the context of different synergies that can be identified when compressing and drying wet CO2 with various units / technologies (e.g. wet CO2 from an amine scrubbing unit on flue gas and cryogenics on waste gas from a PSA H2 of an SMR, or wet CO2 from a pipeline and drying upstream of a liquefier).

[0007] When the water content imposed by the final CO2 specification is restrictive and / or the CO2 is intended for liquefaction at temperatures below 0°C, drying with a TSA is one of the ways to be compliant. It is possible to use a scheme that includes a first heat exchanger with cooling water at a first temperature followed by a second heat exchanger with cooling water at a second temperature lower than the first temperature (produced by a mechanical refrigeration unit and therefore energy consuming) or with a refrigerant coming from a mechanical refrigeration unit in order to cool the wet CO2 further and reduce the size of the downstream TSA as well as the energy required for its regeneration.

[0008] GB-A-2416389 describes a process for cooling wet CO2 in which compressed wet CO2 is cooled first with seawater in a first heat exchanger and then by two flows of gaseous CO2 in a second heat exchanger to condense water contained in the CO2 upstream of an adsorption unit. The water is removed by means of a phase separator downstream of the two exchangers.

[0009] The present invention relates to a method for cooling and separating a CO2 stream containing at least one first component having a dew point temperature between 0 and 70°C at a first pressure which is water and optionally at least one component lighter and / or heavier than CO2 comprising at least the following steps: i. Cooling the CO2 stream at the first pressure from a first temperature to a second temperature by indirect heat exchange with a heating cooling water stream ii. Cooling the CO2 stream at the first pressure to the second temperature by indirect heat exchange with at least one liquid CO2 stream which vaporizes forming a CO2 flow at a third temperature iii.Separation of condensate produced by condensation of the at least one first component present in the CO2 stream during at least one of steps i) or ii) forming a flow (9) enriched in CO2 and purified in the at least one first component iv.steps i) and ii) taking place in a single heat exchanger (R3) and the first and / or second temperatures being between 0 and 15°C, v.the flow enriched in CO2 (9) still containing water is dried by adsorption (A1, A2) or absorption of the water and vi.the flow of gaseous CO2 resulting from the vaporization of the at least one stream of liquid CO2 (19) being at least partly mixed with a gas produced (11, 21) by drying the flow enriched in CO2 of the water.

[0010] According to other optional features:

[0011] • the stream containing at least one first component is compressed upstream of step i) and / or the CO2-enriched stream is compressed after having been dried. • the gaseous CO2 flow resulting from the vaporization of the at least one liquid CO2 stream is at least partly mixed with a gas produced by drying the CO2-enriched flow upstream of the compression of the dried flow.

[0012] • the heat exchanger is of shell and tube technology, comprising at least two tube bundles, the CO2 containing the first component being injected on the shell side and the cooling water being injected into a first tube bundle and the at least one stream of vaporizing liquid CO2 being injected into a second tube bundle.

[0013] • the heat exchanger comprises at least three tube bundles, a liquid CO2 stream being injected into the second tube bundle and a gaseous CO2 stream or a liquid CO2 stream being injected into a third tube bundle.

[0014] • the at least one stream of liquid CO2 comes from a distillation and / or partial condensation process supplied by a flow other than the CO2-enriched flow treated by steps i) and ii).

[0015] • a gas flow containing CO2 from the distillation and / or partial condensation process is used for the regeneration of the adsorption unit in which the flow enriched in CO2 and purified of the at least one first component is dried. the gas used for the regeneration is mixed with the flow of wet CO2 upstream of step i). the at least one flow of liquid CO2 which vaporizes in the heat exchanger is at a pressure between 25 and 45 bar abs, or even between 30 and 45 bar abs.

[0016] According to another aspect of the invention, there is provided an apparatus for cooling and separating a CO2 stream containing at least one first component having a dew point temperature between 0 and 70°C at a first pressure which is water and optionally at least one component lighter and / or heavier than CO2 comprising heat exchange means, means for sending a stream of cooling water to the heat exchange means, means for sending at least one stream of liquid CO2 to the heat exchange means,means for sending the CO2 flow at the first pressure to cool in the heat exchange means from a first temperature to a second temperature by indirect heat exchange with the cooling water stream which heats up and then to cool in the heat exchange means at the first pressure from the second temperature by indirect heat exchange with at least one liquid CO2 stream which vaporizes forming a CO2 flow at a third temperature, means for leaving the exchange means the condensate produced by condensation of the at least one first component present in the CO2 flow, means for leaving the heat exchange means a flow enriched in CO2 and purified in the at least one first component and the heat exchange means being constituted by a single heat exchanger,means for drying the CO2-enriched flow and means for mixing the CO2 flow at the third temperature with the flow dried by the means for drying the CO2-enriched flow.,

[0017] According to other optional features:

[0018] • the heat exchanger consists of a shell and at least two tube bundles arranged in the shell, the means for sending a flow of CO2 at the first pressure to cool, the means for removing the condensate (8) and the means for removing the flow enriched in CO2 being fluidly connected to the shell.

[0019] • one of the tube bundles is fluidically connected to the means for sending the cooling water stream and another of the tube bundles is connected to the means for sending the liquid CO2 stream.

[0020] • the apparatus comprises a compressor for compressing the dried flow downstream of drying means.

[0021] • the means for mixing the CO2 flow at the third temperature with the flow dried by the means for drying the CO2-enriched flow are connected to a point upstream of the compressor.

[0022] • the means for mixing the CO2 flow at the third temperature with the flow dried by the means for drying the CO2-enriched flow are connected to a point downstream of the compressor.

[0023] • the CO2 stream containing at least one first component comes from an amine washing process

[0024] The present invention proposes an optimization of the scheme by introducing a cooling step upstream of the adsorption unit, for example TSA (if present) with liquid CO2 from a cryogenic unit. This step takes place in a single heat exchanger, also cooled by cooling water.

[0025] The configuration proposed in this invention presents the possibility of using less equipment, mainly a first exchanger with cooling water and a second exchanger with liquid CO2 upstream of the TSA by bringing them together in a single exchanger.

[0026] In the case of a shell and tube exchanger, water condensation can take place in the shell of this exchanger, hence saving both the cooler and the separator pot downstream of the cooler, the liquid CO2 will be vaporized in the second tube bundle of the exchanger.

[0027] The vaporized liquid CO2 can be pooled with the dried CO2. To do this, it will be injected into an intermediate section of the common compressor or at its outlet.

[0028] The exchanger with the double tube bundle has a single pass on the shell side, which minimizes the pressure losses on the shell side and allows the installation of a droplet separator on the outlet face of the second bundle.

[0029] The liquid CO2 used for the second cooling stage can come from a low-temperature process, for example, distillation and / or partial condensation, producing CO2. This process replaces the mechanical refrigeration unit used to produce cooling water, which is often used for this purpose.

[0030] Description of the invention

[0031] The invention will be described in more detail with reference to the figure:

[0032] Figure 1 schematically represents a method according to the invention.

[0033] The invention makes it possible to recover and dry wet CO2 1 which can come, for example, from an amine M washing unit or from a gaseous CO2 pipeline at the inlet of a liquefier.

[0034] The wet CO2 is compressed in a first compressor C1, cooled by means of water in a cooler R1 to condense part of the water it contains. The water 6 is removed in a separator S1 and the CO2 3 still containing water is compressed in a compressor C2 to the adsorption pressure of the TSA A1, A2 between 5 and 30 bara, preferably at 10 bara and recovered at the outlet of compressor C2 at a temperature between 80°C and 150°C. The flow 7 at a first pressure between 5 and 30 bara is sent to a shell and tube heat exchanger R3, having two tube bundles F1, F2, the flow 7 being sent to the shell. The water contained in the flow 7 has a dew point temperature between 0 and 70°C at this first pressure. Cooling water is sent to the first bundle F1 to cool the wet CO2 circulating in the tubes of the first bundle. This water is preferably at room temperature.A flow of liquid CO2 19 is sent to the second bundle F2 where it vaporizes forming dry gaseous CO2 while circulating in the tubes of the second bundle F2, preferably at a pressure between 25 bars abs and 45 bars abs or even between 30 bars abs and 45 bars abs.

[0035] Condensed water 8 produced by cooling the wet CO2 7 is removed from the shell.

[0036] At least two streams of liquid CO2 can be sent to the R3 exchanger by adding tube bundles.

[0037] Otherwise at least one flow of liquid CO2 and at least one flow of gaseous CO2 can be sent to exchanger R3 by adding tube bundles.

[0038] An intermediate drying step of the dried gas 9 in the exchanger R3 will be carried out for example in a TSA adsorption unit A1 to ensure that the final CO2 product complies with the water specification. The drying unit can also be a triethylene glycol TEG dryer.

[0039] Temperature swing adsorption (TSA) is a gas mixture separation process in which a gas is alternately adsorbed by a solid or liquid at a given temperature and then desorbed at a higher temperature. 1 .

[0040] Temperature-swing adsorption uses the temperature dependence of adsorption. The adsorbent is loaded with the compound to be separated and is largely freed of this compound in a subsequent step by means of the introduction of thermal energy. For continuous operation of a temperature-swing adsorption system, at least two adsorbent beds are required; one being loaded and the other being desorbed. While the gas is adsorbed in bed A1, it is desorbed in bed A2 and vice versa.

[0041] The dry CO2 11 leaving the adsorbent bed A1 (or A2 depending on the cycle) can then be further compressed to the final pressure by a compressor C3 in common with the vaporized CO2 stream(s) 19. If the vaporized CO2 19 is at a sufficiently high pressure, it can be mixed with the dry CO2 downstream of the compressor C3.

[0042] Otherwise the vaporized CO2 can be sent as flow 19A upstream of compressor C2, if its pressure is not high enough to be sent upstream of compressor C3.

[0043] The dry CO2 flow may be mixed with the vaporized liquid CO2 flow 19 in the bundle F2 upstream or downstream of the compressor C3. The compressed flow 21 may be cooled by a cooler R4 to form a dry CO2 flow 23. The gas 23 may feed a CO2 liquefier other than the apparatus 20.

[0044] This solution is advantageously economical in terms of investment costs because the number of required equipment is reduced. Only a single R3 dual-fluid heat exchanger will be required instead of several exchangers and potentially gas / liquid separation pots. In addition, this solution potentially eliminates the need for a dedicated refrigeration unit.

[0045] The at least one stream 19 may be produced by a distillation and / or partial condensation apparatus 20 producing a gas flow enriched in CO2 25 and / or a gas flow 27 enriched in the at least one component lighter or heavier than CO2. The apparatus 20 is supplied by a flow other than the flow 11, 21, 23.

[0046] Flow 7 at the first pressure may contain another first component than water, having a dew point temperature between 0 and 70°C at this first pressure, for example methanol or ammonia.

[0047] Flow 7 at the first pressure may contain another first component instead of water or in addition to water, having a dew point temperature between 0 and 70°C at this first pressure, for example methanol or ammonia.

Claims

Claims 1. Method for cooling and separating a CO2 stream (1, 3, 7) containing at least one first component having a dew point temperature between 0 and 70°C at a first pressure which is water and optionally at least one component lighter and / or heavier than CO2 comprising at least the following steps: i. Cooling the CO2 stream at the first pressure from a first temperature to a second temperature by indirect heat exchange with a heating cooling water stream ii.Cooling the CO2 stream at the first pressure to the second temperature by indirect heat exchange with at least one liquid CO2 stream (19) which vaporizes forming a CO2 flow at a third temperature iii) Separation of condensate (8) produced by condensation of the at least one first component present in the CO2 stream during at least one of steps i) or ii) forming a flow (9) enriched in CO2 and purified of the at least one first component iii. steps i) and ii) taking place in a single heat exchanger (R3) and the first and / or second temperatures being between 0 and 15°C, iv. the CO2-enriched flow (9) still containing water is dried by adsorption (A1, A2) or absorption of the water, v. the gaseous CO2 flow resulting from the vaporization of the at least one liquid CO2 stream (19) being at least partly mixed with a gas produced (11, 21) by drying the CO2-enriched flow of water.

2. Method according to one of the preceding claims in which the stream (1, 3, 7) containing at least a first component is compressed (C1, C2) upstream of step i) and / or the CO2-enriched stream (9) is compressed after having been dried (C3).

3. Method according to one of the preceding claims in which the flow of gaseous CO2 resulting from the vaporization of the at least one stream of liquid CO2 (19) is at least partly mixed with a gas produced (11, 15) by drying the flow enriched in CO2 upstream of the compression of the dried flow.

4. Method according to one of the preceding claims in which the heat exchanger (R3) is of tube and shell technology, comprising at least two tube bundles (F1, F2), the CO2 containing the first component being injected on the shell side and the cooling water being injected into a first tube bundle (F1) and the at least one stream of liquid CO2 (19) vaporizing being injected into a second tube bundle (F2).

5. Method according to claim 4 wherein the heat exchanger comprises at least three tube bundles (F1, F2), a stream of liquid CO2 (19) being injected into the second tube bundle (F2) and a stream of gaseous CO2 or a stream of liquid CO2 being injected into a third tube bundle.

6. Method according to one of the preceding claims in which the at least one stream of liquid CO2 (19) comes from a distillation and / or partial condensation process (20) supplied by a flow other than the flow enriched in CO2 treated by steps i) and ii) (9, 21, 23).

7. Method according to claim 6, in which a gas flow (21, 29) containing CO2 originating from the distillation and / or partial condensation process (20) is used for the regeneration of the adsorption unit (A1, A2) in which the flow (9) enriched in CO2 and purified of the at least one first component is dried.

8. Method according to claim 7 in which the gas used for regeneration (31, 35, 37, 39) is mixed with the stream of wet CO2 (1, 3, 7) upstream of step i).

9. Method according to one of the preceding claims in which the at least one flow of liquid CO2 (19) which vaporizes in the heat exchanger (R3) is at a pressure between 25 and 45 bars abs, or even between 30 and 45 bars abs.

10. Apparatus for cooling and separating a CO2 flow (1, 3, 7) containing at least a first component having a dew point temperature between 0 and 70°C at a first pressure which is water and optionally at least one component lighter and / or heavier than CO2 comprising heat exchange means (R3), means for sending a stream of cooling water to the heat exchange means, means for sending at least one stream of liquid CO2 (19) to the heat exchange means, means for sending the CO2 stream at the first pressure to cool in the heat exchange means from a first temperature to a second temperature by indirect heat exchange with the cooling water stream which heats up and then to cool in the heat exchange means at the first pressure from the second temperature by indirect heat exchange with at least one stream of liquid CO2 (19) which vaporizes forming a CO2 flow at a third temperature,means for removing from the exchange means the condensate (8) produced by condensation of the at least one first component present in the CO2 flow, means for removing from the heat exchange means a flow (9) enriched in CO2 and purified in the at least one first component and the heat exchange means being constituted by a single heat exchanger, means (A1, A2) for drying the flow enriched in CO2 and means for mixing the flow of CO2 at the third temperature with the flow (11, 15) dried by the means for drying the flow enriched in CO2., 11. Apparatus according to claim 10 wherein the heat exchanger (R3) is constituted by a shell and at least two tube bundles (F1, F2) arranged in the shell, the means for sending a flow of CO2 (7) at the first pressure to cool, the means for removing the condensate (8) and the means for removing the flow enriched in CO2 (9) being fluidically connected to the shell 12. Apparatus according to claim 11 in which one of the tube bundles (F 1 ) is fluidically connected to the means for sending the cooling water stream and another of the tube bundles (F2) is connected to the means for sending the liquid CO2 stream (19).

13. Apparatus according to one of claims 10 to 12 comprising a compressor (C3) for compressing the dried flow downstream of drying means (A1, A2).

14. Apparatus according to claim 13 wherein the means for mixing the CO2 flow at the third temperature with the flow (11, 15) dried by the means for drying the CO2-enriched flow are connected to a point upstream of the compressor (C3).

15. Apparatus according to claim 13 wherein the means for mixing the CO2 flow at the third temperature with the flow (11, 15) dried by the means for drying the CO2-enriched flow are connected to a point downstream of the compressor.

Images