SYSTEM AND METHOD FOR UNLOADING LCO2 FROM A SHIP TO AN INTERMEDIATE STORAGE TANK AT AN LCO2 RECEIVING DEVICE

Description

FIELD OF THE INVENTION

[0001] The present invention generally relates to CCS technology, and more particularly to a system for offloading liquid CO 2 (LCO 2 ) from an LCO 2 carrier ship to an intermediate LCO 2 storage tank at an LCO 2 receiving terminal connected to a long term LCO 2 storage facility, wherein cross-contamination from cargo of one ship to another can be avoided. The invention also relates to a corresponding method. The invention uses a slip stream of LCO 2 withdrawn from a stream of LCO 2 being offloaded to the terminal which is vaporised and returned to the LCO 2 carrier ship, and the vaporisation is used to provide sub-cooling of an LCO 2 stream withdrawn from the intermediate LCO 2 storage tank, and a resulting sub-cooled LCO 2 stream is returned to the intermediate LCO 2 storage tank by spraying into the head space of the intermediate LCO 2 storage tank. The present invention also relates to a corresponding method.BACKGROUND ART

[0002] Captured and liquefied carbon dioxide can be transported in the liquid phase (LCO 2 ) from various locations and customers to CO 2 receiving terminals at which the CO 2 will be temporarily stored in intermediate buffer storage tanks onshore, before being pumped in a dense phase via a pipeline and injected into an offshore long-term storage reservoir. The purpose of the buffer storage is to allow for continuous injection to the long-term storage reservoir despite intermittent LCO 2 cargo transfer from ship.

[0003] A general description of an outline of a CCS chain can be found in Conceptualization of CO2 Terminal for Offshore CCS Using System Engineering Process by Hyonjeong et al. Energies, 2019, 12, 4350. Said CCS chain description includes the return of CO 2 carriers to consider the vaporised CO 2 (VCO 2 ) in returning carriers. According to Hyonjeong et al., the same volume of VCO 2 must be loaded into the carrier's cargo tank when unloading LCO 2 from the carrier to the CO 2 terminal. The carrier's cargo tank is displaced by the VCO 2 of the storage tanks at the terminal, while LCO 2 fills the storage tanks. There are two reasons for loading VCO 2 into the carrier's cargo tank. The first is to allow the pressure and temperature of the cargo tank to be controlled during the unloading process. Constant pressure and temperature facilitate the process. The second reason is to prevent the rapid decrease in temperature due to Joule-Thomson cooling.

[0004] Thus, for example, during LCO 2 cargo transfer between ship and onshore intermediate storage, the displaced vapour in the onshore intermediate storage tank could be returned to the CO 2 carrier ship via a vapour return connection for pressure maintenance in both sets of tanks, i.e. of the carrier ship and of the intermediate storage of the CO 2 receiving terminal, respectively.

[0005] However, depending on origin and purity of the LCO 2 being received at the terminal, the vapour in the onshore storage tank or tanks may contain impurities. In the event that restrictions are imposed on the vapour quality of vapour being returned to the ship that are not met by the vapour composition in the onshore storage, such impurities could pose a substantial impediment to the functioning of the CCS chain. In particular, LCO 2 receiving terminals served by multiple customers, with CO 2 originating from various sources, could face challenges from a technical and commercial point with undesired cross-contamination caused by impurities contained in the vapour space, originating from previous off-loaded cargo, of the onshore storage tanks when returned to the ships.

[0006] It would be desirable to enable pressure maintenance in both sets of tanks, i.e. of the carrier ship and of the intermediate storage of the CO 2 receiving terminal, while reducing, and preferably avoiding, the risk of contaminating an LCO 2 carrier tank at a ship in connection with offloading LCO 2 from the ship to an LCO 2 receiving terminal.

[0007] It is an object of the present invention to provide a system and a method enabling the above.SUMMARY OF THE INVENTION

[0008] The present invention is based on using a slip stream of LCO 2 , which is being withdrawn from a stream LCO 2 being offloaded from a ship and imported to the terminal, for sub-cooling an LCO 2 stream being withdrawn from an intermediate storage tank to which intermediate storage tank a remaining LCO 2 main stream resulting after withdrawal of the slip stream is being led, wherein the two streams are kept separate, and wherein the resulting sub-cooled LCO 2 stream is resprayed into the head space of the storage tank. The obtained cooling for subcooling the LCO 2 stream is accomplished by subjecting the LCO 2 slip stream to a reduced pressure. The resulting cold partly vaporised LCO 2 slip stream, and the LCO 2 stream withdrawn from the storage tank are led to a heat exchanger for exchange of heat. After complete vaporisation of the LCO 2 slip stream, the resulting CO 2 vapour after compression thereof is led back to the ship in a vapour return conduit.

[0009] Accordingly, in one aspect the invention relates to a system 250 for offloading LCO 2 cargo from an LCO 2 carrier ship 30 to an intermediate LCO 2 storage tank 40 at an LCO 2 receiving terminal 300, which system avoids cross-contamination of cargo from one LCO 2 carrier ship 30 to another, said system comprising: an intermediate LCO 2 storage tank 40; an LCO 2 cargo import conduit 1, 10 connected to the intermediate LCO 2 storage tank 40 configured to receive an LCO 2 cargo import stream from the LCO 2 carrier ship 30; a CO 2 vapour return conduit 4, 5, 6, 7, 8, 9 configured to be connected to the LCO 2 carrier ship 30 and to return from the system 250 CO 2 vapour to the LCO 2 carrier ship 30; an LCO 2 main outlet 70 from the intermediate LCO 2 storage tank 40 configured to discharging an injection stream of LCO 2 from the intermediate LCO 2 storage tank 40; which system additionally comprises an LCO 2 slip stream conduit 2 connected to the LCO 2 cargo import conduit 1 configured to withdrawing a slip stream of LCO 2 from the LCO 2 cargo import conduit 1; a pressure let-down valve A connected to the LCO 2 slip stream conduit 2 configured to receiving the slip stream of LCO 2 having a first temperature T1, and to exiting an at least partly vaporised stream of LCO 2 having a second lower temperature T2; a partly vaporised stream conduit 3 connected to the pressure let-down valve A configured to receiving the at least partly vaporised stream of LCO 2 having a second lower temperature T2; a withdrawn LCO 2 stream conduit 16' connected to the intermediate LCO 2 storage tank 40 configured to discharging a stream of LCO 2 from the intermediate LCO 2 storage tank 40; a first heat exchanger B" connected to the partly vaporised stream conduit 3 and to the withdrawn LCO 2 stream conduit 16', respectively, said heat exchanger being configured to receiving the at least partly vaporised stream of LCO 2 having the second lower temperature T2, to receiving the LCO 2 stream withdrawn from the intermediate LCO 2 storage tank 40, to transferring heat from the withdrawn LCO 2 stream to the at least partly vaporised stream of LCO 2 having the second lower temperature T2, to exiting a cooler withdrawn LCO 2 stream and to exiting an at least partly vaporised stream of LCO 2 , respectively; re-spraying means 80 configured to receiving the cooler withdrawn LCO 2 stream and to respraying said sub-cooled withdrawn LCO 2 stream into the head space of intermediate LCO 2 storage tank 40; wherein the CO 2 vapour return conduit 4, 5, 6, 7, 8, 9 is further configured to receive CO 2 vapour resulting from the at least partly vaporised stream of LCO 2 having the second lower temperature T2; and a vapour return compressor F arranged along the vapour return conduit 4, 5, 6, 7, 8, 9 configured to compressing the CO 2 vapour to be returned to the LCO 2 carrier ship 30.

[0010] In a preferred embodiment of the system, the system additionally comprises means configured to vaporising a remaining non-vaporised fraction of the at least partly vaporised stream of LCO 2 exiting the first heat exchanger B".

[0011] In another aspect, the invention relates to a method for offloading LCO 2 cargo from an LCO 2 carrier ship 30 to an intermediate LCO 2 storage tank 40 at an LCO 2 receiving terminal 300, avoiding cross-contamination of cargo from one LCO 2 carrier ship 30 to another, said method comprising the following steps: i. receiving a cargo import stream of LCO 2 from an LCO 2 carrier ship 30 and directing a main stream of the LCO 2 to an intermediate LCO 2 storage tank 40; ii. withdrawing LCO 2 from an LCO 2 main outlet 70 from the intermediate LCO 2 storage tank 40; iv. returning CO 2 vapour from the terminal 300 back to the LCO 2 carrier ship 30, which method additionally comprises the following steps: iii'. withdrawing a stream of LCO 2 from the intermediate LCO 2 storage tank 40; v. withdrawing from the cargo import stream of LCO 2 a slip stream of LCO 2 ; vi. subjecting the withdrawn slip stream of LCO 2 having a first temperature T1 to a reduced pressure, thereby partly vaporising the withdrawn LCO 2 slip stream having a first temperature T1 so as to produce an at least partly vaporised LCO 2 slip stream having a second lower temperature T2; vii". subjecting the stream of LCO 2 withdrawn from the intermediate LCO 2 storage tank 40 to heat exchange with the at least partly vaporised LCO 2 slip stream having the second lower temperature T2, thereby sub-cooling the stream of LCO 2 withdrawn from the intermediate LCO 2 storage tank 40; viii". returning the resulting cooled stream of LCO 2 withdrawn from the intermediate LCO 2 storage tank 40 from step vii" back to the intermediate LCO 2 storage tank 40 by re-spraying the sub-cooled stream of LCO 2 into the head space of the storage tank 40; wherein, in step iv., the CO 2 vapour from the terminal 300 being returned to the LCO 2 carrier ship 30 comprises a stream of CO 2 vapour obtained from the slip stream of LCO 2 and is subjected to compression before being returned to the ship.

[0012] In a preferred embodiment of the method, the method additionally comprises a step ix. wherein a remaining non-vaporised fraction of the at least partly vaporised LCO 2 slip stream after heat exchange in step vii. is vaporised.

[0013] The present invention provides a method and system providing vapour return for pressure support of LCO 2 carrier ship 30 tanks during liquid off-loading by generating vapours directly from the off-loading cargo at the terminal 300, eliminating the risk for return of vapour potentially containing incompatible impurities from previous ships existing in the onshore storage tank facility 40.

[0014] Also, the invention provides an energy efficient measure to reduce the pressure in the onshore storage tanks 40, by heat integration with the ship vapour return 4, 5, 6, 7, 8, 9.

[0015] The present invention provides a method for force-vaporising a portion of the off-loaded LCO 2 cargo, providing vapour for pressure support to the ship tanks without ingress of any potential contaminants from the main onshore storage facility. The system also provides cooling duty for pressure maintenance in the onshore storage tanks, reducing or eliminating the energy requirements and need for a BOG-handling system.

[0016] The present invention achieves the advantage of providing CO 2 vapour return to an off-loading LCO 2 carrier ship 30, independent of the content in the onshore storage tanks, i.e. avoiding exposure of potential contaminants contained in the vapour space from previous off-loaded cargoes, such as from other LCO 2 carrier ships 30.

[0017] Further embodiments and advantages of the invention will be apparent from the following detailed description and appended claims.

[0018] In the present disclosure, same reference numeral is used both to denote the conduit and the stream flowing therein. For example, reference numeral 2 is used to both denote the slip stream conduit, and also to denote the slip stream itself flowing in said conduit.

[0019] The term "long-term" as used herein denotes a storage intended to be permanent.

[0020] The present system and method may be combined with either one or both of the embodiments disclosed applicant's co-pending applications filed on even date herewith, especially, as a compliment, with a method and system handling BOG, such as the system and method of applicant's co-pending application.BRIEF DESCRIPTION OF THE ATTACHED DRAWING

[0021] Figure 1 shows an embodiment of the inventive system 250 as indicated by the dashed line implemented into an LCO 2 receiving terminal 300. The inventive system 250 in its most generic embodiment does not include C, D, E, which in a preferred embodiment can be arranged along the vapour return conduit 4, 5, 6, 7, 8, 9, and does also not include I, and J, which are units conventionally included in a conventional LCO 2 receiving terminal 300, in which the inventive system 250 has not been implemented. A withdrawn LCO 2 stream pump K will be required if the pressure in conduit 16 at the point for off-take from conduit 16 is not sufficient to respray the LCO2 into the storage tank head space. This will be the case e.g. when the off-take point is upstream of a first pump stage along 16. Similarly, a withdrawn LCO 2 stream pump K will also be required when the withdrawn LCO 2 stream 16' is withdrawn directly from the storage tank 40 (not shown).DETAILED DESCRIPTION OF THE INVENTION

[0022] The core of the invention is a process scheme that enables efficient heat integration between the cold closed-circuit vapour return stream to LCO 2 carrier ship 30 and the warmer LCO 2 stream being withdrawn from the onshore storage tanks 40. This is achieved by using a slip stream of the off-loaded LCO 2 cargo stream, which serves a dual purpose: as the CO 2 pressure is let down to e.g. 7 barg, the temperature will drop to approximately -45°C, providing refrigeration for the LCO 2 stream being withdrawn during filling of onshore storage tanks 40. Respraying of the cooled LCO 2 stream enables a reduced amount of displaced vapour during filling of the storage tank 40; the cold low-pressure LCO 2 is vaporised by indirect heat exchange in the first heat exchanger B" which enables a closed-circuit vapour return system, eliminating the risk for return of vapour potentially containing incompatible impurities from previous ships existing in the onshore storage tank facility.

[0023] In the above connection, a lower pressure will increase the cooling duty in the first heat exchanger B", but will also increase the compressor duty of vapour return compressor F.

[0024] Without CO 2 vapour return from the LCO 2 receiving terminal 300 to the LCO 2 carrier ship 30, e.g. in order to avoid cross-contamination of the tanks of the LCO 2 carrier ship 30, vapour for pressure maintenance on the ship could possibly alternatively be generated by force-vaporising liquid CO 2 cargo on the ship. Such solution is however considered inferior to the solution offered by the invention, since, i.a., with such solution, the displaced vapour in the intermediate LCO 2 storage tank or tanks 40 during filling will increase the sizing and energy requirements for a BOG-handling system of the LCO 2 receiving terminal 300.

[0025] In the embodiment of the invention illustrated in FIG. 1, LCO 2 is offloaded from a ship 30 at pressures from e.g. 15-18 barg (denoted as medium pressure (MP), with a typical saturation temperature between -30°C and -20°C).

[0026] A slip stream 2 of the off-loaded cargo stream 1 is fed to a pressure let-down control valve A, where the pressure is let down to e.g. 6-10 barg (denoted as low pressure (LP), with a saturation temperature between -50°C and -40°C).

[0027] The flow rate of the slip stream 2 will be determined by the off-loading rate, and typically around 5% of the total flow of the cargo stream will be required.

[0028] On the downstream side 3 of the pressure let-down valve A a two-phase LP LCO 2 stream is fed to the first heat exchanger B". In the embodiment in FIG. 1 the first heat exchanger B" is depicted as a shell and tube heat exchanger but could alternatively be of another type, such as a plate or plate-fin heat exchanger. In the first heat exchanger B", the cold two-phase LP stream provides cooling of the LCO 2 stream withdrawn from the storage tank 40 during filling thereof. The displacement rate will depend on the filing rate 10, the injection rate 18, and the temperature of the cooled stream of LCO 2 being resprayed into the head space of the storage tank 40.

[0029] Ideally, in a case of operation wherein the two-phase LP LCO 2 stream has been fully vaporised after heat exchange in the first heat exchanger B", the resulting CO 2 vapour could be returned to the ship after compression of the CO 2 vapour stream 7 in the vapour return compressor F.

[0030] Following heat exchange in the first heat exchanger B" in a case of operation wherein the partly vaporised LP LCO 2 stream 4 has not been fully vaporised, the stream is further vaporised in a second heat exchanger C, using the warm discharge stream 8 of CO 2 vapour from the vapour return compressor F. In the inventive system, first and second heat exchangers B" and C, respectively, could be referred to as cross heat exchangers.

[0031] In case the heat contents of the withdrawn stream of LCO 2 16' and of the compressor discharge stream 8 are not sufficient to completely vaporise the LP LCO2, so that a partly vaporised LCO 2 stream 5 remains after the second heat exchanger C, a dedicated vaporiser D is provided. The vaporiser D could be heated electrically, by ambient sea water or other suitable heat sources available at the terminal 300.

[0032] From the vaporiser D the LP CO 2 6 is preferably fed to a knock-out drum E to ensure that any remaining liquid droplets are not found in the suction flow 7 to the vapour return compressor F.

[0033] The vapour return compressor F will increase the pressure to be compatible with the ship cargo tank pressure. The compressor discharge 8 is cooled by cross-heat exchange in heat exchanger C, providing heat for vaporisation of a remaining liquid phase in the LP LCO2 stream 4 as described above.

[0034] Vapour 9 is returned to ship 30 at pressure and temperature compatible with the MP cargo at a rate that approximately equals the volumetric flow of off-loaded liquid 1.

[0035] As shown in the embodiment of the invention illustrated in FIG. 1, the offloaded LCO 2 is split into two process sections. As described above, the LP LCO2 slip stream 2 is providing vapour for the displaced liquid in the ship cargo tanks 30 in a closed circuit 2, 3, 4, 5, 6, 7, 8, 9. The major part of the imported LCO 2 is transferred 10 at MP conditions to the intermediate storage tank(s) 40.

[0036] Liquid CO 2 is transferred 16 to injection pump or pumps I. In the embodiment of FIG. 1, the injection pump I is shown as a single pump but could also be configured in series with booster pumps. The pump(s) provide sufficient head for dense phase CO 2 to be exported to a pipeline 110 and subsequently injected into a reservoir 120 for permanent storage. Downstream of the injection pump I , an injection heater J may be needed to avoid sub-zero temperatures entering the pipeline 110. The injection heater J could be heated electrically, by ambient sea water or other suitable heat sources available at the terminal.

[0037] The LCO 2 stream 16' being withdrawn from the storage tank 40 during filling thereof could be withdrawn directly from the tank via a dedicated outlet nozzle (not shown) in the tank, or via the injection stream conduit 16, and is thereafter forwarded by a pump K to heat exchanger B" (and further to spraying means 80). Alternatively, the off-take for withdrawn stream 16' could be located along the injection stream conduit 16 downstream a pump stage (not shown) with sufficient head to respray the LCO2 into the storage tank head space, in which case a withdrawn LCO 2 stream pump K should not be required.

[0038] The export flow rate 18 is likely to be lower than cargo transfer rate 10, hence, as the level in the intermediate storage tank 40 increases vapour will be displaced, or the tank pressure will increase. To control pressure, the displaced vapour will need to be processed or reduced, to avoid CO 2 emission to ambient by vent.

[0039] The displaced vapour at MP conditions will be re-liquefied by respraying of the colder LCO 2 stream 16" into the head space of tank 40. Ideally, in a case of operation wherein the BOG and / or displaced vapour can be completely re-liquefied in the storage tank by virtue of the colder LCO 2 stream 16" being resprayed into the tank, an additional BOG-handling system is not required.

[0040] A BOG-handling system may be included in the inventive system in order to handle any remaining BOG or displaced vapour not being balanced by the colder partial stream of LCO 2 being sprayed into the storage tank, e.g. using applicant's system for reliquefaction of a fraction of the BOG withdrawn from the storage tank, as disclosed in applicant's co-pending application filed on even date herewith.LIST OF REFERENCE SIGNS USED

[0041] 1, 10LCO 2 cargo import conduit 2LCO 2 slip stream conduit 3partly vaporised LCO 2 stream conduit 4, 5, 6, 7, 8, 9CO 2 vapour return conduit 16conduit connecting bottom outlet 70 with injection pump I 16'withdrawn LCO 2 stream conduit 16"LCO 2 stream conduit to heat exchanger 16‴cooled LCO 2 stream conduit 18conduit connecting outlet from injection pump with injection heater J 30LCO 2 carrier ship 40intermediate LCO 2 storage tank 250system for offloading LCO 2 cargo (from an LCO 2 carrier ship) 70main LCO 2 outlet (from intermediate LCO 2 storage tank) 80re-spraying means 300LCO 2 receiving terminal 110pipeline 120underground long term storage facility T1first temperature (of slip stream) T2second lower temperature (of partly vaporised LCO 2 stream) Apressure let-down valve B"first heat exchanger Csecond heat exchanger Dvaporiser Eknock-out drum Fvapour return compressor Iinjection pump Jinjection heater Kwithdrawn LCO 2 stream pump

Claims

1. A system (250) for offloading LCO2 cargo from an LCO2 carrier ship (30) to an intermediate LCO2 storage tank (40) at an LCO2 receiving terminal (300), which system avoids cross-contamination of cargo from one LCO2 carrier ship (30) to another, said system comprising: - an intermediate LCO2 storage tank (40); - an LCO2 cargo import conduit (1, 10) connected to the intermediate LCO2 storage tank (40) configured to receive an LCO2 cargo import stream from the LCO2 carrier ship (30); - a CO2 vapour return conduit (4, 5, 6, 7, 8, 9) configured to be connected to the LCO2 carrier ship (30) and to return from the system (250) CO2 vapour to the LCO2 carrier ship (30); - an LCO2 main outlet (70) from the intermediate LCO2 storage tank (40) configured to discharging LCO2 from the intermediate LCO2 storage tank (40); characterized in additionally comprising, - an LCO2 slip stream conduit (2) connected to the LCO2 cargo import conduit (1) configured to withdrawing a slip stream of LCO2 from the LCO2 cargo import conduit (1); - a pressure let-down valve (A) connected to the LCO2 slip stream conduit (2) configured to receiving the slip stream of LCO2 having a first temperature (T1), and to exiting an at least partly vaporised stream of LCO2 having a second lower temperature (T2); - a partly vaporised stream conduit (3) connected to the pressure let-down valve (A) configured to receiving the at least partly vaporised stream of LCO2 having a second lower temperature (T2); - a withdrawn LCO2 stream conduit (16') connected to the intermediate LCO2 storage tank (40) configured to discharging a stream of LCO2 from the intermediate LCO2 storage tank (40); - a first heat exchanger (B") connected to the partly vaporised stream conduit (3) and to the withdrawn LCO2 stream conduit (16'), respectively, said heat exchanger being configured to receiving the at least partly vaporised stream of LCO2 having the second lower temperature (T2), to receiving the LCO2 stream withdrawn from the intermediate LCO2 storage tank (40), to transferring heat from the LCO2 stream to the at least partly vaporised stream of LCO2 having the second lower temperature (T2), to exiting a cooler withdrawn LCO2 stream and to exiting an at least partly vaporised stream of LCO2, respectively; - re-spraying means (80) configured to receiving the cooler withdrawn LCO2 stream and to respraying said cooler withdrawn LCO2 stream into the head space of intermediate LCO2 storage tank (40); - wherein the CO2 vapour return conduit (4, 5, 6, 7, 8, 9) is further configured to receiving CO2 vapour resulting from the at least partly vaporised stream of LCO2 having the second lower temperature (T2); and - a vapour return compressor (F) arranged along the vapour return conduit (4, 5, 6, 7, 8, 9) configured to compressing the CO2 vapour to be returned to the LCO2 carrier ship (30).

2. The system (50) of claim 1, additionally comprising - means (C, D, E) arranged along the CO2 vapour return conduit (4, 5, 6, 7, 8, 9) configured to vaporising a remaining non-vaporised fraction of the at least partly vaporised stream of LCO2 exiting the first heat exchanger (B").

3. A method for offloading LCO2 cargo from an LCO2 carrier ship (30) to an intermediate LCO2 storage tank (40) at an LCO2 receiving terminal (300), avoiding cross-contamination of cargo from one LCO2 carrier ship (30) to another, said method comprising the following steps: i.) receiving a cargo import stream of LCO2 from an LCO2 carrier ship (30) and directing a main stream of the cargo import stream of LCO2 to an intermediate LCO2 storage tank (40); ii.) withdrawing an LCO2 injection stream from an LCO2 main outlet (70) from the intermediate LCO2 storage tank (40); iv.) returning CO2 vapour from the terminal (300) back to the LCO2 carrier ship (30), characterized in additionally comprising the following steps: iii'.) withdrawing a stream of LCO2 from the intermediate LCO2 storage tank (40); v.) withdrawing from the cargo import stream of LCO2 a slip stream of LCO2; vi.) subjecting the withdrawn slip stream of LCO2 having a first temperature (T1) to a reduced pressure, thereby partly vaporising the withdrawn LCO2 slip stream having a first temperature (T1) so as to produce an at least partly vaporised LCO2 slip stream having a second lower temperature (T2); vii".) subjecting the stream of LCO2 withdrawn from the intermediate LCO2 storage tank (40) to heat exchange with the at least partly vaporised LCO2 slip stream having the second lower temperature (T2), thereby sub-cooling the stream of LCO2 withdrawn from the intermediate LCO2 storage tank (40); viii".) returning the resulting sub-cooled stream of LCO2 withdrawn from the intermediate LCO2 storage tank (40) from step vii" back to the intermediate LCO2 storage tank (40) by re-spraying the sub-cooled stream of LCO2 into the head space of the storage tank (40); wherein, in step (iv.), the CO2 vapour from the terminal (300) being returned to the LCO2 carrier ship (30) comprises a stream of CO2 vapour obtained from the slip stream of LCO2 and is subjected to compression before being returned to the ship.

4. The method for offloading LCO2 cargo from an LCO2 carrier ship (30) to an intermediate LCO2 storage tank (40) at an LCO2 receiving terminal (100) of claim 3, additionally comprising the following step: ix.) vaporising a remaining non-vaporised fraction of the at least partly vaporised LCO2 slip stream after heat exchange in step (vii), wherein, in step (iv.), the CO2 vapour from the terminal being returned to the LCO2 carrier ship (30) comprises the resulting CO2 vapour from step (ix.).