A regasification system for liquified gas, a ship, and a method of regasification of liquefied gas

Abstract

The disclosure relates to a regasification system for liquified gas, including a liquefied gas feed stream (130), at least one booster pump (110) for pressurizing the liquefied gas stream (130) to a first pressurized liquefied gas stream (132), and a second pressurized liquefied gas stream (134) to be passed through at least one vaporizer system (114) to produce a vaporized gas stream (136) by regasification of the second pressurized liquefied gas stream (134), wherein the system comprises at least one expander (116) for receiving and expanding a portion of the vaporized gas stream (136) as a return portion vaporized gas stream (138) to produce an expanded gas stream (142), a heat exchanger (112) for heat exchanging between the first pressurized 10 liquefied gas stream (132) and the expanded gas stream (142) to provide a condensed gas stream (144), and returning the condensed gas stream (144) into the liquefied gas feed stream (130).

Description

[0001] A regasification system for liquified gas, a ship, and a method of regasification of liquefied gas

[0002] Technical field

[0003] The present disclosure relates to a regasification system for liquified gas, a ship, and a method of regasification of liquefied gas. More specifically, the disclosure relates to a regasification system for liquified gas, a ship, and a method of regasification of liquefied gas as defined in the introductory parts of the independent claims.

[0004] Background art

[0005] Regasification systems for liquefied gases represent a critical link in the energy supply chain, facilitating the seamless transition of liquefied gases, such as for example liquefied natural gas (LNG), from a condensed, easily transportable state back into their gaseous forms.

[0006] LNG is a mixture of light hydrocarbons with methane as the main component and nitrogen as inert and small amounts of ethane, propane, butane, and pentane may be present. Depending upon its exact composition, the boiling point of LNG is around - 162 °C to -158 °C at atmospheric pressure.

[0007] Regasification systems can be land-based or installed onboard floating storage and regasification unit (FSRU) vessels or shuttle and regasification vessels (SRVs). It is often favourable to re-vaporize the liquefied gas aboard the sea-going carrier before the gas is off-loaded into onshore pipelines. The typical regasification process involves outputting the liquified gas from a cargo tank, pressurizing the liquefied gas in a booster pump and vaporizing the pressurized liquefied gas to gaseous form before delivering it to the distribution network.

[0008] A problem with the solutions of the prior art is that they do not have optimal efficiency.

[0009] There is thus a need for an improved regasification system.

[0010] Summary

[0011] It is an object of the present disclosure to mitigate, alleviate or eliminate one or more of the above-identified deficiencies and disadvantages in the prior art and solve at least the above-mentioned problem. According to a first aspect, there is provided a regasification system for liquified gas, including a liquefied gas feed stream, at least one booster pump for pressurizing the liquefied gas stream to a first pressurized liquefied gas stream, and a second pressurized liquefied gas stream to be passed through at least one vaporizer system to produce a vaporized gas stream by regasification of the second pressurized liquefied gas stream, wherein the system comprises at least one expander for receiving and expanding a portion of the vaporized gas stream as a return portion vaporized gas stream to produce an expanded gas stream, a heat exchanger for heat exchanging between the first pressurized liquefied gas stream and the expanded gas stream to provide a condensed gas stream, and returning the condensed gas stream into the liquefied gas feed stream.

[0012] According to some embodiments, the expander is connected to a power production system.

[0013] According to some embodiments, the system comprises at least one heater for pre-heating the return portion vaporized gas stream, the return portion vaporized gas stream entering the heater as a non-heated portion vaporized gas stream and entering the expander as a pre-heated vaporized gas stream.

[0014] According to some embodiments, the first and second pressurized liquefied gas streams have a pressure of 30 - 150 bar.

[0015] According to some embodiments, the expanded gas stream has a pressure of 3 - 30 bar.

[0016] According to some embodiments, the system is configured to route up to 60 % of the vaporized gas stream from the at least one vaporizer system back through the expander and heat exchanger to the liquefied gas feed stream.

[0017] According to some embodiments, the at least one vaporizer system comprises a heat exchanger.

[0018] According to some embodiments, the system comprises a suction drum.

[0019] According to some embodiments, the suction drum is in the form of a combined suction drum and recondenser. According to some embodiments, the system is configured to expand the return portion vaporized gas stream in two or more pressure stages and to optionally heat said gas stream between the pressure stages.

[0020] According to a second aspect, there is provided a ship comprising a regasification system according to the first aspect claims, the ship further comprising an outlet manifold for leading an outlet vaporized gas stream to an onshore installation.

[0021] According to a third aspect, there is provided a method of regasification of liquefied gas comprising: feeding a liquefied gas feed stream to at least one booster pump, increasing pressure of the liquefied gas stream to a first pressurized liquefied gas stream in the at least one booster pump, regasifying a second pressurized liquefied gas stream in at least one vaporizer system to produce a vaporized gas stream, wherein routing a portion of the vaporized gas stream as a return portion vaporized gas stream to a feedback loop, in which feedback loop expanding the return portion vaporized gas stream to provide an expanded gas stream, heat exchanging the expanded gas stream against the first pressurized liquefied gas stream from the at least one booster pump to condense the expanded gas stream to a condensed gas stream, and returning the condensed gas stream into the liquefied gas feed stream.

[0022] According to some embodiments, the return portion vaporized gas stream is routed to the feedback loop as a non-heated portion vaporized gas stream and preheated in a heater to a pre-heated vaporized gas stream before being expanded in the feedback loop.

[0023] According to some embodiments, the return portion vaporized gas stream is expanded in two or more pressure stages and optionally heated between the pressure stages.

[0024] According to some embodiments, the pressure of the liquefied gas feed stream is increased to 30 - 150 bar in the at least one booster pump, and the pressure of the expanded gas stream is reduced to 3 - 30 bar in the feedback loop.

[0025] Effects and features of the second and third aspects are to a large extent analogous to those described above in connection with the first aspect. Embodiments mentioned in relation to the first aspect are largely compatible with the second and third aspects.

[0026] The present disclosure will become apparent from the detailed description given below. The detailed description and specific examples disclose preferred embodiments of the disclosure by way of illustration only. Those skilled in the art understand from guidance in the detailed description that changes and modifications may be made within the scope of the disclosure.

[0027] Hence, it is to be understood that the herein disclosed disclosure is not limited to the particular component parts of the device described or steps of the methods described since such device and method may vary. It is also to be understood that the terminology used herein is for purpose of describing particular embodiments only and is not intended to be limiting. It should be noted that, as used in the specification and the appended claim, the articles "a", "an", "the", and "said" are intended to mean that there are one or more of the elements unless the context explicitly dictates otherwise. Thus, for example, reference to "a unit" or "the unit" may include several devices, and the like. Furthermore, the words "comprising", "including", "containing" and similar wordings does not exclude other elements or steps.

[0028] Brief descriptions of the drawings

[0029] The above objects, as well as additional objects, features and advantages of the present disclosure, will be more fully appreciated by reference to the following illustrative and non-limiting detailed description of example embodiments of the present disclosure, when taken in conjunction with the accompanying drawings.

[0030] Figure 1 shows a simplified process flow diagram of a regasification system according to an embodiment of the present disclosure.

[0031] Figure 2 shows a simplified process flow diagram of a regasification system according to an embodiment of the present disclosure.

[0032] Detailed description

[0033] The present disclosure will now be described with reference to the accompanying drawings, in which preferred example embodiments of the disclosure are shown. The disclosure may, however, be embodied in other forms and should not be construed as limited to the herein disclosed embodiments. The disclosed embodiments are provided to fully convey the scope of the disclosure to the skilled person.

[0034] Figure 1 shows a regasification system 100 for liquified gas according to an embodiment of the present disclosure. An inlet liquefied gas stream 128 is fed from a cargo tank for storage of liquefied gas (not shown in the figure) to a liquefied gas feed stream 130, which is fed to at least one booster pump 110 for pressurizing the liquefied gas stream 130 to a first pressurized liquefied gas stream 132. The first pressurized liquefied gas stream 132 is led through a heat exchanger 112 and exits the heat exchanger 112 as a second pressurized liquefied gas stream 134, which is passed through at least one vaporizer system 114 to produce a vaporized gas stream 136 by regasification of the pressurized liquefied gas stream 134. The vaporized gas stream 136 is split into two, an outlet vaporized gas stream 140, which is led out of the regasification system, and a return portion of vaporized gas 138. Figure 1 shows an expander 116 for receiving and expanding the return portion of vaporized gas stream 138 to produce an expanded gas stream 142. A power production system 118 is optionally connected to the expander 116. In the heat exchanger 112, heat exchanging between the first pressurized liquefied gas stream 132 and the expanded gas stream 142 takes place to provide a condensed gas stream 144. The condensed gas stream 144 is returned into the liquefied gas feed stream 130. The condensed gas stream 144 may also be returned into the cargo tank for storage of liquefied gas (not shown in the figure), before being fed to the liquefied gas feed stream 130.

[0035] When compared to known regasification systems, the embodiments according to the invention comprise a feedback loop for routing a portion of the vaporized gas back to the liquefied gas stream. That is, in the traditional systems, the liquefied gas stream 128 is pressurized in the pump 110, vaporized in the vaporizer 114 and the gas is led out of the system via line 140 to a gas distribution network. In the present embodiments, a portion of the vaporized gas 138 is routed back to the input stream 130 as explained above. In this way, significant energy savings in the magnitude of 40 % can be obtained.

[0036] Figure 2 shows a regasification system 200 for liquified gas according to an embodiment of the present disclosure. An inlet liquefied gas stream 250 is fed from a cargo tank for storage of liquefied gas (not shown in the figure) into a suction drum 224. A liquefied gas feed stream 130 is fed from the suction drum 224 to at least one booster pump 110 for pressurizing the liquefied gas stream 130 to a first pressurized liquefied gas stream 132. The first pressurized liquefied gas stream 132 is led through a heat exchanger 112 and exits the heat exchanger 112 as a second pressurized liquefied gas stream 134, which is passed through at least one vaporizer system 114 to produce a vaporized gas stream 136 by regasification of the second pressurized liquefied gas stream 134. The vaporized gas stream 136 is split into two, an outlet vaporized gas stream 140, which is led out of the regasification system, and a non-heated portion vaporized gas stream 244, which is led to a heater 230 for pre-heating the non-heated portion vaporized gas stream 244, which exits the heater 230 as pre-heated vaporized gas stream 246. Figure 2 further shows an expander 116 for receiving and expanding the pre-heated vaporized gas stream 246 to produce an expanded gas stream 142. A power production system 118 is optionally connected to the expander 116. In the heat exchanger 112, heat exchanging between the first pressurized liquefied gas stream 132 and the expanded gas stream 142 takes place to provide a condensed gas stream 248. Figure 2 further shows a liquid receiver 220 installed along the condensed gas stream 248, and a valve 222 for regulating the flow of the condensed gas stream 248 into the suction drum 224, before being fed to the liquefied gas stream 130. The condensed gas stream 248 may also be returned, directly or via the suction drum 224, into the cargo tank for storage of liquefied gas (not shown in the figure), before being fed to the liquefied gas stream 130.

[0037] The first aspect of this disclosure shows a regasification system for liquified gas, including a liquefied gas feed stream 130, at least one booster pump 110 for pressurizing the liquefied gas stream 130 to a first pressurized liquefied gas stream 132, and a second pressurized liquefied gas stream 134 to be passed through at least one vaporizer system 114 to produce a vaporized gas stream 136 by regasification of the second pressurized liquefied gas stream 134, wherein the system comprises at least one expander 116 for receiving and expanding a portion of the vaporized gas stream 136 as a return portion vaporized gas stream 138 to produce an expanded gas stream 142, a heat exchanger 112 for heat exchanging between the first pressurized liquefied gas stream 132 and the expanded gas stream 142 to provide a condensed gas stream 144, and returning the condensed gas stream 144 into the liquefied gas feed stream 130. The condensed gas stream 144 may also be led back to a cargo tank for storage of liquefied gas. Expander 116 can be connected to a power production system 118. An expander, also known as a turbo expander, is an equipment that can extract energy by reducing the pressure of any fluid.

[0038] The system according to the disclosure can comprise at least one heater 230 for pre-heating the return portion vaporized gas stream 138, the return portion vaporized gas stream 138 entering the heater 230 as a non-heated portion vaporized gas stream 244 and entering the expander 116 as a pre-heated vaporized gas stream 246. The heater 230 can be of any type suitable to pre-heat said vaporized gas stream 244.

[0039] The first and second pressurized liquefied gas streams 132, 134 can have a pressure of up to 150 bar, such as in the range of 30 - 150 bar, or 30 - 130 bar, or 40 - 120 bar (1 bar equals 105Pa).

[0040] The expanded gas stream 142 can have a pressure of up to 30 bar, such as in the range of 3 - 30 bar, or 4 - 20 bar, or 5 - 15 bar.

[0041] The system according to the disclosure can be configured to route up to 60 % of the vaporized gas stream 136 from the at least one vaporizer system 114 back through the expander 116 and heat exchanger 112 to the liquefied gas feed stream 130. The system according to the disclosure can be configured to route at least 1 % of the vaporized gas stream 136 from the at least one vaporizer system 114 back through the expander 116 and heat exchanger 112 to the liquefied gas feed stream 130. For example, 2 - 50 %, 5 - 40 %, or 10 - 30 % of the vaporized gas stream 136 can be routed back to the liquefied gas feed stream 130.

[0042] The at least one vaporizer system 114 comprises a heat exchanger (not shown in the figures) that is used for vaporizing the pressurized liquefied gas stream 134 to provide the vaporized gas stream 136. The heat exchanger can be any type of heat exchanger; e.g., a compact printed circuit heat exchanger, PCHE, made from stainless steel or any suitable material.

[0043] The principle of vaporizing liquefied gas is well known to the person skilled in the art, and therefore not described any further her.

[0044] The system according to the disclosure can comprise a suction drum 224. The suction drum 224 is configured to receive an inlet liquefied gas stream 250 and the condensed gas stream 248 and to feed liquefied gas via the liquefied gas feed stream 130 into the at least one booster pump 110. The pressure of the liquefied gas in the suction drum is around 3 - 6 bar, typically around 5 bar.

[0045] The suction drum 224 can be in the form of a combined suction drum and recondenser.

[0046] The system according to the disclosure can be configured to expand the return portion vaporized gas stream (138) in two or more pressure stages and to optionally heat said gas stream between the pressure stages. The expansion in two or more pressure stages and the optional heating between the pressure stages can take place in the expander 116.

[0047] The at least one booster pump 110, which boosts / increases liquefied gas pressure, can for example be in the form of a multistage centrifugal pump.

[0048] The system according to the disclosure may further comprise a liquid receiver 220 and a valve 222 configured to control any produced flash, and to control the flow of the condensed gas stream 248 back to the liquefied gas feed stream 130 either via the suction drum 224 or directly from the heat exchanger 112 to the liquefied gas feed stream 130. The condensed gas stream 248 may also be led back to a cargo tank for liquefied gas.

[0049] The system according to the disclosure can be configured to mixing boil-off gas (BOG) into the expanded gas stream 142 before entering the heat exchanger 112 (not shown in the figures), in order to avoid or reduce the need for regular BOG recondensation.

[0050] The liquefied gas can be any appropriate type of liquefied gas, such as, but not limited to, liquefied natural gas (LNG), liquefied ethane, liquefied propane, liquefied biogas, liquefied synthetic methane, liquefied nitrogen, liquefied hydrogen, or liquefied carbon dioxide, with the corresponding vaporized gases, such as, but not limited to, natural gas (NG), ethane, propane, biogas, synthetic methane, nitrogen, hydrogen, or carbon dioxide.

[0051] The regasification system according to the disclosure can comprise several trains. There will be a heat exchanger 112 on each train. The condensation will happen on the train(s) that is (are) in operation. The trains will be connected and have one common outlet vaporized gas stream 140. The second aspect of this disclosure shows a ship comprising a regasification system according to the first aspect claims, the ship further comprising an outlet manifold for leading the outlet vaporized gas stream 140 to an onshore installation.

[0052] The third aspect of this disclosure shows a method of regasification of liquefied gas comprising: feeding a liquefied gas feed stream 130 to at least one booster pump 110, increasing pressure of the liquefied gas stream 130 to a first pressurized liquefied gas stream 132 in the at least one booster pump 110, regasifying a second pressurized liquefied gas stream 134 in at least one vaporizer system 114 to produce a vaporized gas stream 136, wherein routing a portion of the vaporized gas stream 136 as a return portion vaporized gas stream 138 to a feedback loop, in which feedback loop expanding the return portion vaporized gas stream 138 to provide an expanded gas stream 142, heat exchanging the expanded gas stream 142 against the first pressurized liquefied gas stream 132 from the at least one booster pump 110 to condense the expanded gas stream 142 to a condensed gas stream 144, and returning the condensed gas stream 144 into the liquefied gas feed stream 130.

[0053] The feedback loop comprises at least one expander 116, which may be connected to a power production system 118. The feedback loop further comprises a heat exchanger 112.

[0054] The return portion vaporized gas stream 138 can be routed to the feedback loop as a non-heated portion vaporized gas stream 244 and pre-heated in a heater 230 to a pre-heated vaporized gas stream 246 before being expanded in the expander 116 in the feedback loop. The expansion can be done in several pressure stages, and the return portion vaporized gas stream 138 can optionally be heated between the stages. The expansion in two or more pressure stages and the optional heating between the pressure stages can take place in the expander 116.

[0055] The pressure of the liquefied gas feed stream 130 is increased to 30 - 150 bar, or 30 - 130 bar, or 40 - 120 bar, in the at least one booster pump 110. The pressure of the liquefied gas feed stream 130 when entering the booster pump 110 can for example be around 3 - 6 bar, typically around 5 bar. The pressure of the expanded gas stream 142 is reduced to 3 - 30 bar, 4 - 20 bar, or 5 - 15 bar in the feedback loop.

[0056] In the method according to the disclosure, up to 60 % of the vaporized gas stream 136 from the at least one vaporizer system 114 may be routed into the feedback loop. At least 1 % of the vaporized gas stream 136 may be routed into the feedback loop. For example, 2 - 50 %, 5 - 40 %, or 10 - 30 % of the vaporized gas stream 136 can be routed into the feedback loop.

[0057] Instead of returning the condensed gas stream 144 directly into the liquefied gas feed stream 130, the method according to the disclosure may comprise leading condensed gas in condensed gas stream 248 into a suction drum 224 and feeding liquefied gas from the suction drum 224 to the liquefied gas stream 130. The condensed gas stream 248 may comprise a liquid receiver 220 and a valve 222 for controlling produced flash and to regulate the flow of the condensed gas stream 248 back to the liquefied gas feed stream 130 either via the suction drum 224 or directly from the heat exchanger 112 to the liquefied gas feed stream 130. The condensed gas stream 248 may also be returned, directly or via the suction drum 224, into a cargo tank for storage of liquefied gas (not shown in the figures).

[0058] Liquefied gas can be fed from a cargo tank (not shown in the figures) through an inlet liquefied gas stream 128 to the liquefied gas feed stream 130 and to the least one booster pump 110, or through an inlet liquefied gas stream 250 via the suction drum 224 to the at least one booster pump 110 from the liquefied gas feed stream 130.

[0059] The first and second pressurized liquefied gas streams 132, 134 are referred to as being at the high-pressure side of the at least one booster pump 110. The condensed gas stream 144 is referred to as being at the suction side of the at least one booster pump 110. The expanded gas stream 142 is condensed in the heat exchanger 112, which is cooled by the first pressurized liquefied gas stream 132. This happens at a pressure slightly higher than the pressure on the suction side of the at least one booster pump 110. The pressure here will automatically adjust according to the area of heat exchanger 112.

[0060] The inventor surprisingly found that by splitting the vaporized gas stream 136 after exiting the vaporization system 114 and leading a return portion vaporized gas stream 138 in a feedback loop, comprising the above-described expansion and heat exchanging, before being returned to the liquefied gas feed stream 130, the regasification system could operate in a more optimal manner, and thereby generate considerable reductions in power consumption, compared to existing systems. For example, starting with a 500 mmscfd system, with power consumption approx. 7 MW, with 30 % of the vaporized gas being recycled, approximately 5 MW is extracted, so 2.0 MW is spent. It is then delivered 350 mmscfd out, which would consume approx. 4.9 MW if operated without the expander; net saved power then equals 2.9 MW.

[0061] The system and method according to the disclosure can be used onboard any sea-going vessel, offshore, for example on a platform, or onshore.

[0062] The person skilled in the art realizes that the present disclosure is not limited to the preferred embodiments described above. The person skilled in the art further realizes that modifications and variations are possible within the scope of the appended claims. Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed disclosure, from a study of the drawings, the disclosure, and the appended claims.

Claims

CLAIMS1. A regasification system for liquified gas, including a liquefied gas feed stream (130), at least one booster pump (110) for pressurizing the liquefied gas stream (130) to a first pressurized liquefied gas stream (132), and a second pressurized liquefied gas stream (134) to be passed through at least one vaporizer system (114) to produce a vaporized gas stream (136) by regasification of the second pressurized liquefied gas stream (134), c h a r a c t e r i z e d i n that the system comprises at least one expander (116) for receiving and expanding a portion of the vaporized gas stream (136) as a return portion vaporized gas stream (138) to produce an expanded gas stream (142), a heat exchanger (112) for heat exchanging between the first pressurized liquefied gas stream (132) and the expanded gas stream (142) to provide a condensed gas stream (144), and returning the condensed gas stream (144) into the liquefied gas feed stream (130).

2. The regasification system according to claim 1, wherein the expander (116) is connected to a power production system (118).

3. The regasification system according to claim 1 or 2, wherein the system comprises at least one heater (230) for pre-heating the return portion vaporized gas stream (138), the return portion vaporized gas stream (138) entering the heater (230) as a non-heated portion vaporized gas stream (244) and entering the expander (116) as a pre-heated vaporized gas stream (246).

4. The regasification system according to any one of the preceding claims, wherein the first and second pressurized liquefied gas streams (132,134) have a pressure of 30 - 150 bar.

5. The regasification system according to any one of the preceding claims, wherein the expanded gas stream (142) has a pressure of 3 - 30 bar.

6. The regasification system according to any one of the preceding claims, wherein the system is configured to route up to 60 % of the vaporized gas stream (136) from the at least one vaporizer system (114) back through the expander (116) and heat exchanger (112) to the liquefied gas feed stream (130).

7. The regasification system according to any one of the preceding claims, wherein the at least one vaporizer system (114) comprises a heat exchanger.

8. The regasification system according to any one of the preceding claims, wherein the system comprises a suction drum (224).

9. The regasification system according to claim 8, wherein the suction drum (224) is in the form of a combined suction drum and recondenser.

10. The regasification system according to any one of the preceding claims, wherein the system is configured to expand the return portion vaporized gas stream (138) in two or more pressure stages and to optionally heat said gas stream between the pressure stages.

11. A ship comprising a regasification system according to any one of the preceding claims, the ship further comprising an outlet manifold for leading an outlet vaporized gas stream (140) to an onshore installation.

12. A method of regasification of liquefied gas comprising: feeding a liquefied gas feed stream (130) to at least one booster pump (110), increasing pressure of the liquefied gas stream (130) to a first pressurized liquefied gas stream (132) in the at least one booster pump (110), regasifying a second pressurized liquefied gas stream (134) in at least one vaporizer system (114) to produce a vaporized gas stream (136), c h a r a c t e r i z e d i n routing a portion of the vaporized gas stream (136) as a return portion vaporized gas stream (138) to a feedback loop, in which feedback loop expanding the return portion vaporized gas stream (138) to provide an expanded gas stream (142), heat exchanging the expanded gas stream (142) against the first pressurized liquefied gas stream (132) from the at least one booster pump (110) to condense the expanded gas stream (142) to a condensed gas stream (144), and returning the condensed gas stream (144) into the liquefied gas feed stream (130).

13. The method according to claim 12, wherein the return portion vaporized gas stream (138) is routed to the feedback loop as a non-heated portion vaporized gas stream (244) and pre-heated in a heater (230) to a pre-heated vaporized gas stream (246) before being expanded in the feedback loop.

14. The method according to claim 12 or 13, wherein the return portion vaporized gas stream (138) is expanded in two or more pressure stages and optionally heated between the pressure stages.

15. The method according to any one of claims 12 - 14, wherein the pressure of the liquefied gas feed stream (130) is increased to 30 - 150 bar in the at least one booster pump (110), and the pressure of the expanded gas stream (142) is reduced to 3 - 30 bar in the feedback loop.

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