WO2016038081A1

WO2016038081A1 - Hydrocarbon processing plant with a side water intake system and method of operating such a plant

Info

Publication number: WO2016038081A1
Application number: PCT/EP2015/070592
Authority: WO
Inventors: Robbert Van Der Wal; Scott M. DAVEY; Christiaan M. NA; Augustine FRANCIS; Roel BRANDT; Casimir Willem Hendrik VAN DOORNE
Original assignee: Shell Internationale Research Maatschappij B.V.; Shell Oil Company
Priority date: 2014-09-11
Filing date: 2015-09-09
Publication date: 2016-03-17

Abstract

The invention relates to a hydrocarbon processing plant (100) comprising a wall (110). The wall (110) is at least partially submerged in a body of water. The hydrocarbon processing plant (100) comprises a water intake system (1) comprising a water intake opening (2) provided in the underwater part of the wall (110), an air disengagement tank (3) comprising a tank inlet (4), the tank inlet (4) being formed by or being in fluid communication with the water intake opening (2). The air disengagement tank (3) comprises a tank outlet (5). The air disengagement tank (3) is in fluid connection with a vent channel (6).

Description

Hydrocarbon processing plant with a side water intake system and

method of operating such a plant

TECHNICAL FIELD

The present invention relates to a hydrocarbon processing plant. The invention further relates to a method of

operating such a hydrocarbon processing plant.

STATE OF THE ART

Different types of hydrocarbon processing plants are known. Hydrocarbon processing plants are known which process natural gas by liquefying a vaporous hydrocarbon containing feed stream and/or by gasifying a liquefied hydrocarbon containing stream. The natural gas may be sweet gas or sour gas .

Hydrocarbon processing plants may be on-shore structures, but may also be provided on off-shore structures, such as floating structures and gravity based off-shore structures.

Examples of floating structures are FLNG-structures (floating liquid natural gas) and F(P)SO structures (floating (production) , storage and off-loading) .

Gravity based off-shore structures are typically formed by a barge, e.g. a concrete barge, located on the sea floor.

A commercially important liquefied hydrocarbon is liquefied natural gas (LNG) , which is typically produced by extracting heat from a natural gas stream whereby the natural gas is cooled to reach a temperature that is below the bubble point of the LNG at atmospheric pressure. The temperature is typically about -162 °C. The removed heat is generally brought into the ambient. In case of a water-cooled LNG production process, the heat is removed by cooling (sea) water and generally released into the sea. Before use by an end user, the LNG is typically

revaporized, which involves withdrawing heat from the ambient and adding this heat to the LNG. The heat may be taken from a stream of (sea) water.

Both in liquefying and vaporizing natural gas processing plants water is taken in.

Floating hydrocarbon processing plants often comprise a water intake riser assembly being suspended from the floating structure into the body of water to take in water from a certain depth and supply the water to the hydrocarbon processing plant via the water intake riser assembly. The water is used to add heat to, or remove heat from, a

hydrocarbon stream. Subsequently the water is disposed of. An example of such a floating hydrocarbon processing plant is provided in WO2012066039.

In some cases, it is not possible to use water intake riser assemblies being suspended from the floating structure. This is for instance the case when the floating hydrocarbon processing plant is operational in shallow waters or in case the hydrocarbon processing plant is provided on an off-shore gravity based structure, e.g. positioned on a barge placed on the sea floor.

An example of such an off-shore gravity based structure is the Adriatic LNG terminal (formally known as Terminale GNL Adriatico Sri.), a joint venture company owned by ExxonMobil, Qatar Petroleum and Edison in the Adriatic Sea.

In these cases, water intake riser assemblies are not suitable .

US4041721 provides an example of a floating natural gas processing plant using side water intake systems. The side water intake system is provided in a side wall of the hull of the vessel. Water intake pumps are provided to take water in. Side water intake systems are known which comprise an inlet screen or inlet filter to prevent debris and sea life from being taken in (e.g. Johnson Screens® intake screens) . However, side water intake systems have an increased risk of getting blocked by debris and sea life with respect to water intake riser assemblies. Blockage could cause failure of the inlet screen or filter as a result of high differential pressure caused by such blockage. This may happen when the inlet screens are exposed to a high differential pressure and the sea cooling water intake pumps continue to run. This could cause damage to the inlet screens. Blockage may result in the need to interrupt (part of) the plant to perform maintenance, which is very cost-inefficient.

Side water intake systems are known which use an air blast cleaning system, which periodically generates an outward blast of air through the inlet screen or inlet filter (i.e. in a direction opposite to the direction of taking in water), to clean the inlet screen or inlet filter. Johnson Screens® use a so-called hydroburst™ system to do this.

Such air blast cleaning systems can be operated

simultaneously with taking in water. This introduces an increased risk of air being entrained in the water taken in via the side water intake system. Entrained air in the cooling water could cause cavitation in the water intake pumps .

SHORT DESCRIPTION

It is an object to provide a hydrocarbon processing plant having a side water intake system with a reduced risk of air being entrained in the water taken in via the side water intake system. The term 'comprising' is used in this text to indicate that all the enlisted elements are encompassed without excluding the presence of additional non-named elements.

In accordance with an aspect of the present invention, there is provided a hydrocarbon processing plant 100

comprising a wall 110, the wall 110, in use, being at least partially submerged in a body of water, the hydrocarbon processing plant lOOfurther comprising a water intake system 1 comprising a water intake opening 2 provided in an

underwater part of the wall 110, an air disengagement tank 3 comprising a tank inlet 4, the tank inlet 4 being formed by or being in fluid communication with the water intake opening 2, the air disengagement tank 3 comprising a tank outlet 5, the air disengagement tank 3 being in fluid connection with a vent channel 6.

The wall may be a side-wall, in particular a vertical wall of the hydrocarbon processing plant.

The wall may be an outer wall. The wall may form part of the hull of a floating structure supporting the hydrocarbon processing plant, typically being a metal wall, such as a steel or iron wall. The wall may also be made of concrete, in particular in case the structure is a gravity based structure or an on-shore structure.

The water intake system comprises one or more water intake pumps for generating a water flow through the water intake opening towards the tank inlet, the air disengagement tank, the tank outlet and finally towards further equipment of the hydrocarbon processing plant, such as heat exchangers for cooling/liquefying a vaporous hydrocarbon containing feed stream and/or for heating/gasifying a liquefied hydrocarbon stream. A cooling water suction conduit 7 may be provided which is in fluid communication with the tank outlet. One or more water intake pumps may be present somewhere along the cooling water suction conduit 7 and/or inside the air disengagement tank 3.

Providing such an air disengagement tank being in fluid communication with a vent channel allows air to escape from the water before the water reaches the water intake pumps and thereby reduces air associated damage to the water intake pumps and subsequent equipment, e.g. caused by cavitation.

The air disengagement tank is typically located between the wall and the wall or hull and storage tanks located inside the wall or hull. The storage tanks may be one of a LNG storage tank, a refrigerant storage tank, a condensate storage tank, a waste storage tank or an oil storage tank.

According to an embodiment, the hydrocarbon processing plant is a floating hydrocarbon processing plant, which comprises one or more water ballast tanks, wherein the air disengagement tank, and optionally at least part of the vent channel, is located inside the water ballast tanks.

The air disengagement tank is preferably located at a minimum distance from a bottom of the structure for safety and integrity reasons of both the air disengagement tank and the hull .

According to an embodiment the vent channel 6 comprises a vent channel inlet 61 being in fluid communication with an opening in the upper half of the air disengagement tank 3 and a vent channel outlet 62 being in fluid communication with the vent channel inlet 61, the vent channel outlet 62 being at a higher level than the vent channel inlet 61.

Positioning the vent channel inlet in the upper half of the air disengagement tank ensures that the air is routed through the vent channel effectively.

Typically, the vent channel inlet 61 is positioned in the ceiling 31 of the air disengagement tank 6. The ceiling may be a horizontal flat surface or may be a dome-shaped upper surface. The vent channel and/or the ceiling may be formed without dead pockets as to prevent air being trapped in such dead pockets. The vent channel therefore has a monotonically increasing height from the vent channel inlet to the vent channel outlet. For instance, the vent channel is a vertical vent channel or an inclined vent channel or is formed of a combination of vertical and inclined portions.

In case the hydrocarbon processing plant is a floating or off shore gravity based structure, the vent channel outlet is preferably located at the (processing) deck of the floating or off shore gravity based structure.

In case the hydrocarbon processing plant is a floating or off shore gravity based structure, the vent channel is preferably located between the wall or hull and storage tanks located inside the hull. The storage tanks may be one of a LNG storage tank, a refrigerant storage tank, a condensate storage tank, a waste storage tank or an oil storage tank.

According to an embodiment the vent channel 6 comprises a liquid level sensor 63 arranged to obtain an indication of a liquid level in the vent channel 6.

During normal operation, the liquid level of the water is between the vent channel inlet 61 and the vent channel outlet 62. The intended liquid level of the water during normal operation is referred to as the set point. The set point will typically be below the water surface of the body of water and may vary with varying conditions, such as the draught of the floating structure and/or the movements of the floating structure or the water level with respect to the on shore or off shore gravity based structure.

In case the water intake opening 2 provided in the underwater part of the wall 110 gets (partially) blocked and the water intake pumps continue to run, the liquid level of the water in the vent channel 6 will drop. Once the liquid level drops to a warning level at a predetermined distance below the set point, a warning signal may be generated by the liquid level sensor or a control unit arranged to receive the liquid level sensor readings . In response to such a warning signal, appropriate action may be taken, such as slowing down or tripping pumps .

The set point and the warning level may be variable and depend on further parameters which for instance influence the differential pressure across an inlet filter or inlet screen. In case of a floating structure such further parameters may comprise the draught and/or movements of the floating structure. In case of an on-shore or off-shore gravity based structure, such further parameters may comprise the water level (e.g. to take into account tidal influences) .

The liquid level sensor may comprise one or more liquid sensors arranged to detect the presence of liquid, in particular water. The one or more liquid sensors is/are provided at predetermined locations either inside the vent channel or adjacent to the vent channel 6. The liquid sensor may for instance use capacitive or inductive measurement techniques for detecting the presence of liquid.

According to an alternative, the liquid level sensor may be arranged to sense the liquid level from a distance and may be positioned remote from the vent channel 6, e.g. above the vent channel 6. In such an embodiment, the liquid level sensor may comprise a transmission unit (e.g. acoustic) directed to the liquid surface and a receiving unit (e.g. an acoustic) to detect transmitted signals which are reflected by the liquid surface. In combination with a timer for measuring the travelling time of the emitted signal an indication of the liquid level in the vent channel can be computed . According to an embodiment the water intake system 1 comprises a water intake pump 8 arranged to pump in water via the water intake opening 2 and the liquid level sensor 63 is in data communication with the pump 8 to adjust operational parameters of the water intake pump in response to an obtained indication of the liquid level.

The hydrocarbon processing plant may comprise a control unit 64 via which the data communication between the liquid level sensor 63 and the water intake pump 8 is established. The control unit 64 may comprise a central processing unit 642, a memory unit 641 comprising instructions readable and executable by the central processing unit 642 and an

input/output unit 643 to establish data communication with the liquid level sensor 63, the water intake pump 8 and optionally a blast system as discussed in more detail below. The input/output unit 643 is in particular arranged to receive liquid level readings from the liquid level sensor 63 and transmit pump control instructions to the water intake pump 8 to adjust the operational parameters of the water intake pump, such as pump speed. The input/output unit may be arranged to communicate wired and/or wireless.

The programming lines may provide the control unit 64 with the functionality to generate pump control instructions in response to readings received from the liquid level sensor 63. The pump control instructions may comprise pump speed control instructions to control the pump speed, trip

instructions to stop the pump, pump discharge flow

instructions to control the pump discharge flow, recycle valve instructions to open/close recycle valves, etc.

In case the liquid level drops below a predetermined level, i.e. the set point, and the liquid level sensor readings indicate that there is no liquid present at the liquid level sensor, the control unit 64 generates pump control instructions and transmits these to the water intake pump 8 to prevent the inlet screens or inlet filters from being exposed to relatively high differential pressures, which could damage the inlet screens/filters. This can for instance be prevented by generating pump speed control instructions to lower the pump speed, trip instructions to stop the pump, pump discharge flow instructions to increase the pump discharge flow.

According to an embodiment, two or more liquid sensors 63 may be present at same or different heights in the vent channel 6 and may provide a single or a combined result based on the heights to the control unit. This allows obtaining more detailed information about the liquid level and

controlling the water intake pump in a more detailed manner.

The pump speed may be lowered with lower liquid level sensor readings and the pump may be tripped or the pump speed may be set to zero once a minimum liquid level has been reached .

Such detailed control of the pumps speed may also be applied in case the liquid level sensor comprises a sound or radiation emission unit as described above.

According to an embodiment the air disengagement tank 3 comprises a flow obstruction element, e.g. a weir 9,

positioned in between the tank inlet 2 and the tank outlet 5.

The flow obstruction element may be a (standing) weir 9 positioned in between the tank inlet 2 and the tank outlet 5 and which has an upper edge positioned at a level above the level of the tank inlet 2 and tank outlet 5. Alternative weir designs may be possible, including a hanging weir, hanging from the ceiling or top part of the air disengagement tank or a combination weir (comprising a standing and a hanging weir) . The flow obstruction element obstructs the flow of water from the tank inlet to the tank outlet and thus lengthens the residence time of the water in the air disengagement tank. This ensures that the entrained air is properly disengaged and not carried forward to the water intake pump.

The water intake pump mentioned above, may be positioned in a pump room, e.g. adjacent to a storage tank, or may be positioned next to the air disengagement tank in the water ballast tank, inside the air disengagement tank. In case the water intake pump is located inside the air disengagement tank, the water intake pump is preferably positioned

downstream of the flow obstruction element, e.g. the weir.

According to an embodiment the air disengagement tank 3 comprises an inlet pipe 21 which is with a first end in fluid communication with the tank inlet 4, the inlet pipe 2 protruding into the air disengagement tank 3 and comprising a second end positioned in the air disengagement tank 3 at a level above the first end.

The second end is preferably directed away from the tank outlet.

The inlet pipe 21 may for instance be an elbow or a raised pipe section, with its second end directed upwardly. The function of the inlet pipe 21 is to direct the inflow of water in a direction which is not directly towards the tank outlet, to lengthen the residence time of the water in the air disengagement tank 3.

In case the air disengagement tank 3 comprises a

(standing) weir 9, the second end of the inlet pipe 21 is preferably located below the level of the upper edge of the weir 9.

According to an embodiment the water intake system 1 comprises an inlet filter system 10, being in fluid

communication with the water intake opening 2. The inlet filter system 10 comprises an inlet screen or inlet filter 11 which allows water to flow via the inlet filter or screen 11 towards/through the water intake opening 2 provided in the underwater part of the wall 110, but prevents particles and the like with a certain minimum size to flow through the inlet filter or screen to reach the water intake opening 2.

The inlet filter system 10 may comprise an inlet screen or inlet filter positioned inside the water intake opening.

Alternatively, the inlet filter system 10 comprises a housing 14 with one or more inlet openings 12 which are in fluid communication with the body of water the inlet filter system 10 is submerged in to, and one or more outlet openings 13 which are in fluid communication with the water intake opening 2 provided in the underwater part of the wall 110.

The inlet filter system preferably doesn't comprise any moving parts and is thus referred to as a passive inlet filter system.

Commercially available inlet filter systems may be used, such as Johnson Screens®, passive water intake screens from Euroslot Kdds . , Ovivo or Screen Services.

According to an embodiment the water intake system 1 comprises a blast system 70 to blast air or gas through the inlet filter system 10 in a direction opposite to the water intake direction.

Such a blast system 70 effectively cleans the inlet filter system by blasting away the contamination gathered on the inlet filter/screen. Such a blast system usually operates on a timer wherein air or gas blasts are initiated on predetermined time intervals.

communication with the water intake opening 2, the inlet filter system 10 comprises a housing 14 with one or more inlet openings 12 which are in fluid communication with the body of water the inlet filter system 10 is submerged in to, and one or more outlet openings 13 which are in fluid communication by means of a water intake conduit with the water intake opening 2 provided in the underwater part of the wall 110, wherein the blast system comprises a blast conduit 73 which has an outlet positioned in the housing 14 directed to the one or more inlet openings 12, wherein the blast conduit 73 is routed through the water intake opening 2.

Such an embodiment provides the advantage that multiple openings in the hull are avoided as the blast conduit and the water intake are done via the same opening in the hull.

According to an embodiment the vent channel 6 comprises a liquid level sensor 63 arranged to obtain an indication of a liquid level in the vent channel 6, wherein the liquid level sensor is in data communication with the blast system to initiate an air or gas blast in response to a predetermined obtained indication of the liquid level.

Such an embodiment ensures that the blast system is also initiated when needed, i.e. when the liquid level in the vent channel has reached a predetermined minimum level.

According to an embodiment the water intake system 1 comprises a plurality of horizontally adjacent water intake openings 2 provided in the underwater part of the wall 110 and a plurality of air disengagement tanks 3 associated with the respective water intake openings 2, wherein the plurality of air disengagement tanks 3 are formed by a segmented chamber .

The term segmented chamber is used to refer to a chamber extending along the plurality of water intake openings, which is segmented to form the plurality of air disengagement tanks. Preferably, the number of water intake openings and air disengagement tanks are the same. Alternatively, the air disengagement tanks are built as separate tanks or chambers.

According to an embodiment the hydrocarbon processing plant is positioned on a floating structure or an off shore gravity based structure, the structure comprising a hull, wherein the wall is part of the hull.

The hull may for instance be made of steel, iron or concrete .

The hull may be an elongated hull, comprising

longitudinal sides, a base extending between the sides, a deck being located atop and between the sides, and,

optionally, a longitudinal mid-plane in between and parallel to the longitudinal sides. The vessel may comprise at least one processing deck, which is elevated with respect to the deck. The processing deck has processing units for the processing of a hydrocarbon stream located thereon.

Inside the hull one or more hydrocarbon storage tanks may be positioned, e.g. suitable for storing liquefied natural gas. In a space-efficient embodiment, the vent channel is routed through a space in between the (sides of the) hull and the storage tank(s) . In a further space-efficient embodiment, the space between the (sides of the) hull and the storage tank(s) is a water ballast tank for controlling the draught of the floating structure and the vent channel is routed through the water ballast tank.

The hydrocarbon processing plant may be for liquefying a vaporous hydrocarbon containing feed stream and/or for gasifying a liquefied hydrocarbon stream. In other words, the hydrocarbon processing plant may cool and liquefy natural gas to form LNG and/or heat and gasify LNG .

In case of a liquefaction plant, the water intake system is provided to take in water and convey the water to the hydrocarbon processing plant for cooling purposes. In case of a gasification plant, the water intake system is provided to take in water and convey the water to the hydrocarbon processing plant for heating purposes.

In both cases the water may be input to heat exchangers provided as part of the hydrocarbon processing plant to add or remove heat to/from a process performed on the hydrocarbon processing plant. Heated or cooled water from the outlet of the heat exchangers may be discharged back into the body of water .

According to an embodiment the hydrocarbon processing plant is a floating hydrocarbon processing plant comprising a hull which, in use, is at least partially submerged in a body of water, the hull comprising a storage tank suitable for storing liquefied or vaporized natural gas, wherein the floating hydrocarbon processing plant 100 comprises a water ballast tank positioned between the hull and the storage tank, wherein the hydrocarbon processing plant 100 comprises a heat exchanger and wherein the tank outlet 5 of the air disengagement is in fluid connection with a piping system to supply water to the heat exchanger 40, wherein at least one of the air disengagement tank 3 and the vent channel 6 are positioned in the water ballast tank.

More than one ballast tank and more than one storage tank may be present. The piping system preferably runs at least partly underneath one of the storage tanks.

According to an embodiment the hydrocarbon processing plant 100 comprises a heat exchanger and the tank outlet 5 of the air disengagement tank is in fluid connection via a piping system to supply water to the heat exchanger 40, wherein at least part of the piping system 60 is routed through the water ballast tank 30.

The heat exchanger may be connected to exchange heat between the water in a hydrocarbon stream. Alternatively, the heat exchanger may be connected to exchange heat between the water and a further heat exchange medium, which may also be water .

According to a further aspect there is provided a method of operating a hydrocarbon processing plant according to the above .

According to an embodiment, the method comprises

producing a liquefied hydrocarbon stream, comprising:

- feeding a vaporous hydrocarbon containing feed stream to the hydrocarbon processing plant,

- on the hydrocarbon processing plant, forming a liquefied hydrocarbon stream from at least a part of the vaporous hydrocarbon containing feed stream comprising at least extracting heat from at least said part of the vaporous hydrocarbon containing feed stream;

- supplying water to the hydrocarbon processing plant via the water intake system;

- adding at least part of the heat removed from said at least a part of the hydrocarbon containing feed stream to at least part of the water supplied via the water intake system;

- subsequently disposing of the at least part of the water .

According to an embodiment, the method comprises

producing a vaporous hydrocarbon stream, comprising:

- providing a liquefied hydrocarbon stream to the hydrocarbon processing plant;

- on the hydrocarbon processing plant, forming a vaporous hydrocarbon stream from at least a part of the liquefied hydrocarbon stream comprising adding heat to the said part of the liquefied hydrocarbon stream;

- supplying water to the hydrocarbon processing plant via the water intake system; - drawing at least part of the heat for adding to the said part of the liquefied hydrocarbon stream from at least part of the water supplied via the water intake system;

- subsequently disposing of the at least part of the water .

According to an embodiment the method comprises

- obtaining an indication of a liquid level in the vent channel 6, and

- deciding to initiate a blast or not in response to the obtained indication of the liquid level.

The blast may be carried out using a blast device as described above. The blast may be executed to clean the inlet filter system.

The decision may be taken by comparing the obtained indication of the liquid level to a predetermined indication of the liquid level.

According to an embodiment the method comprises

- obtaining an indication of a liquid level in the vent channel 6, and

- adjusting the operational parameters of the water

intake pump in response to the obtained indication of the liquid level .

SHORT DESCRIPTION OF THE DRAWINGS

The invention will be further illustrated hereinafter by way of example only, and with reference to the non-limiting drawing in which:

Fig.'s la - lc schematically illustrate floating structures arranged in a body of water comprising a water intake system according to different embodiments.

DETAILED DESCRIPTION

In this description same reference numbers refer to similar components. The person skilled in the art will readily understand that, while the invention is illustrated making reference to one or more a specific combinations of features and measures, many of those features and measures are functionally independent from other features and measures such that they can be equally or similarly applied

independently in other embodiments or combinations.

Fig. la schematically shows a floating structure on which a hydrocarbon processing plant 100 is positioned. The floating structure comprises a deck 101. The hardware elements of the hydrocarbon processing plant 100 may be positioned on the deck 101 and inside the hull 102 of the floating structure. As the hardware elements of hydrocarbon processing plants are known to the skilled person and depend on the type of hydrocarbon processing plant, the hardware elements are not shown.

The floating structure 100 comprises a (side) wall 110 which is partially submerged in a body of water 103.

Fig. la shows a water intake system 1 in more detail. The water intake system 1 is a side water intake system as water is taken in via the side wall 110.

A water intake opening 2 is provided in the wall 110. Behind the water intake opening 2 an air disengagement tank 3 is provided. Water taken in via the water intake opening 2 is guided into the air disengagement tank 3. The air

disengagement tank 3 further comprises a tank outlet 5 which is in fluid communication with a cooling water suction conduit 7 and a water intake pump 8 to transport the water to predetermined further hardware elements of the hydrocarbon processing plant 100.

Further provided is a vent channel 6 which is in fluid communication with the upper part of the air disengagement tank 3 to allow water to partially fill the vent channel and allow entrained air to escape from the water via the vent channel 6.

The air disengagement tank 3 comprises means to increase the residence time of the water inside the air disengagement tank 3 and the vent channel 6 to allow air sufficient time to escape from the water before the water leaves the air disengagement tank 3 via the tank outlet 5. These means comprise a weir 9, having an upper edge above the tank inlet 4 and the tank outlet 5. These means further comprise an inlet pipe 21 which is with a first end in fluid

communication with the tank inlet 4 and protrudes into the air disengagement tank 3 in a direction not directly directed at the tank outlet. In the example shown, the inlet pipe 21 comprises a second end positioned in the air disengagement tank 3 at a level above the first end and directed upwardly.

The water intake system 1 comprises an inlet filter system 10, for instance comprising an inlet screen or inlet filter 11. The inlet screen/ filter 11 can be positioned in the water intake opening 2 as shown in Fig. la.

As schematically shown in Fig. la, the floating structure comprises one or more LNG storage tanks 120, and one or more water ballast tanks 121 positioned in between the LNG storage tank 120 and the hull. The air disengagement tank and optionally at least part of the vent channel is located inside the water ballast tanks, in particular at least partially underneath the one or more LNG storage tanks 120.

For reasons of clarity, the LNG tanks and water ballast tanks are only shown in Fig. la. However, the LNG tanks and water ballast tanks may also be present in the other

embodiments described.

Alternatively, as shown in Fig. lb, the water intake system 1 comprises an inlet filter system 10 comprising a housing 14 which is positioned outside the wall 110 in the body of water 103. The housing 14 comprises one or more inlet openings 12 comprising an inlet screen/filter 11. The housing 14 further comprises one or more outlet openings 13 which are in fluid communication with the water intake opening 2.

A further alternative is shown in Fig. lc, where the water intake system 1 further comprises a blast system 70. The blast system 70 comprises a high pressure air or gas source 71, a blast conduit 73 which is with one end connected to an outlet of the high pressure source 71 (e.g. high pressure vessel) and has another end located in the housing

14 and directed to the inlet screen/filter 11 to blast air or gas through the inlet screen/filter 11 in a direction opposite to the water intake direction. The blast system further comprises a controllable blast valve 72 positioned in the blast conduit 73. Opening the blast valve 72 initiates a blast. It will be understood that other types of blast systems may be used as well. The position of the blast system 70 and its parts are shown schematically in Fig. lc. It will be understood that the blast system can for instance be positioned on the (processing) deck with appropriate piping to the water intake system 1.

The water intake system 1 comprises a liquid level sensor 63. According to the example shown, the liquid level sensor 63 is positioned at a predetermined height in the vent channel 6. The liquid level sensor 63 is for instance arranged to detect the presence or absence of water. The sensor readings of the liquid level sensor 63 can be used to control the pump 8. In case the liquid level sensor 63 senses the presence of water, no action is required. In case the liquid level sensor 63 doesn't sense the presence of water, action is required, for instance by reducing the pump speed or by initiating the blast system 70.

The water intake system 1 comprises a control unit 64 to transfer liquid level sensor readings into appropriate action. The control unit 64 may be a computer device, comprising a central processing unit 642, a memory unit 641 comprising instructions readable and executable by the central processing unit 642 and an input/output unit 643 to establish data communication with the liquid level sensor 63, the blast system 70 and the water intake pump 8. The data communication may be wired and wireless data communication.

Although all embodiments described above with reference to Fig.'s la-lc are shown are hydrocarbon processing plants provided on floating structures, it will be understood that according to further embodiments, off-shore gravity based structures may be provided, as well as on-shore structures having wall 110 at least partially submerged in the body of water .

The person skilled in the art will understand that the present invention can be carried out in many various ways without departing from the scope of the appended claims.

Claims

C L A I M S

1. Hydrocarbon processing plant (100) comprising a wall (110), the wall (110), in use, being at least partially submerged in a body of water, the hydrocarbon processing plant (100) comprising a water intake system (1) comprising a water intake opening (2) provided in an underwater part of the wall (110), an air disengagement tank (3) comprising a tank inlet (4), the tank inlet (4) being formed by or being in fluid communication with the water intake opening (2), the air disengagement tank (3) comprising a tank outlet (5), the air disengagement tank (3) being in fluid connection with a vent channel (6) .

2. Hydrocarbon processing plant (100) according to claim 1, wherein the vent channel (6) comprises a vent channel inlet (61) being in fluid communication with an opening in the upper half of the air disengagement tank (3) and a vent channel outlet (62) being in fluid communication with the vent channel inlet (61), the vent channel outlet (62) being at a higher level than the vent channel inlet (61) .

3. Hydrocarbon processing plant (100) according to any one of the preceding claims, wherein the vent channel (6) comprises a liquid level sensor (63) arranged to obtain an indication of a liquid level in the vent channel (6), and optionally the water intake system (1) comprises a water intake pump (8) arranged to pump in water via the water intake opening (2) and the liquid level sensor (63) is in data communication with the pump (8) to adjust operational parameters of the water intake pump in response to an obtained indication of the liquid level.

4. Hydrocarbon processing plant (100) according to any one of the preceding claims, wherein the air disengagement tank (3) comprises a flow obstruction element, e.g. a weir (9), positioned in between the tank inlet (2) and the tank outlet (5) .

5. Hydrocarbon processing plant (100) according to any one of the preceding claims, wherein the air disengagement tank (3) comprises an inlet pipe (21) which is with a first end in fluid communication with the tank inlet (4), the inlet pipe (2) protruding into the air disengagement tank (3) and comprising a second end positioned in the air disengagement tank (3) at a level above the first end.

6. Hydrocarbon processing plant (100) according to any one of the preceding claims, wherein the water intake system (1) comprises an inlet filter system (10), being in fluid communication with the water intake opening (2) .

7. Hydrocarbon processing plant (100) according to any one of the preceding claims, wherein the water intake system (1) comprises a blast system (70) to blast air or gas through the inlet filter system (10) in a direction opposite to the water intake direction and optionally the water intake system (1) comprises an inlet filter system (10), being in fluid communication with the water intake opening (2), the inlet filter system (10) comprises a housing (14) with one or more inlet openings (12) which are in fluid communication with the body of water the inlet filter system (10) is submerged in to, and one or more outlet openings (13) which are in fluid communication by means of a water intake conduit with the water intake opening (2) provided in the underwater part of the wall (110), wherein the blast system comprises a blast conduit (73) which has an outlet positioned in the housing (14) directed to the one or more inlet openings (12), wherein the blast conduit (73) is routed through the water intake opening (2) .

8. Hydrocarbon processing plant according to claim 7, wherein the vent channel (6) comprises a liquid level sensor (63) arranged to obtain an indication of a liquid level in the vent channel (6), wherein the liquid level sensor is in data communication with the blast system to initiate a blast in response to a predetermined obtained indication of the liquid level.

9. Hydrocarbon processing plant according to any one of the preceding claims, wherein the water intake system (1) comprises a plurality of horizontally adjacent water intake openings (2) provided in the underwater part of the wall (110) and a plurality of air disengagement tanks (3)

associated with the respective water intake openings (2), wherein the plurality of air disengagement tanks (3) are formed by a segmented chamber.

10. Hydrocarbon processing plant (100) according to any one of the preceding claims, wherein the hydrocarbon processing plant is positioned on a floating structure or an off shore gravity based structure, the structure comprising a hull, wherein the wall is part of the hull.

11. Hydrocarbon processing plant (100) according to any one of the preceding claims, wherein the hydrocarbon processing plant is a floating hydrocarbon processing plant comprising a hull which, in use, is at least partially submerged in a body of water, the hull comprising a storage tank suitable for storing liquefied or vaporized natural gas, wherein the floating hydrocarbon processing plant (100) comprises a water ballast tank positioned between the hull and the storage tank, wherein the hydrocarbon processing plant (100)

comprises a heat exchanger and wherein the tank outlet (5) of the air disengagement is in fluid connection with a piping system to supply water to the heat exchanger (40), wherein at least one of the air disengagement tank (3) and the vent channel (6) are positioned in the water ballast tank and optionally the hydrocarbon processing plant (100) comprises a heat exchanger and wherein the tank outlet (5) of the air disengagement tank is in fluid connection with a piping system to supply water to the heat exchanger (40), wherein at least part of the piping system (60) is routed through the water ballast tank (30) .

12. Method of operating a hydrocarbon processing plant according to any one of the preceding claims .

13. Method according to claim 12, wherein the method

comprises producing a liquefied hydrocarbon stream,

comprising :

- subsequently disposing of the at least part of the water .

14. Method according to any one of the claims 12 - 13, wherein the method comprises producing a vaporous hydrocarbon stream, comprising:

- providing a liquefied hydrocarbon stream to the hydrocarbon processing plant;

- drawing at least part of the heat for adding to the said part of the liquefied hydrocarbon stream from at least part of the water supplied via the water intake system;

- subsequently disposing of the at least part of the water .

15. Method according to any one of the claims 12 - 14, wherein the method comprises

- obtaining an indication of a liquid level in the vent channel ( 6 ) , and

16. Method according to any one of the claims 12 - 15, wherein the method comprises obtaining an indication of a liquid level in the vent channel ( 6 ) , and

adjusting the operational parameters of the water intake pump in response to the obtained indication of the liquid level .