Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C9/00—Methods or apparatus for discharging liquefied or solidified gases from vessels not under pressure
  • F17C9/02—Methods or apparatus for discharging liquefied or solidified gases from vessels not under pressure with change of state, e.g. vaporisation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2201/00—Vessel construction, in particular geometry, arrangement or size
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2201/00—Vessel construction, in particular geometry, arrangement or size
  • F17C2201/05—Size
  • F17C2201/052—Size large (>1000 m3)
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2205/00—Vessel construction, in particular mounting arrangements, attachments or identifications means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2221/00—Handled fluid, in particular type of fluid
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2221/00—Handled fluid, in particular type of fluid
  • F17C2221/03—Mixtures
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2223/00—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2223/00—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel
  • F17C2223/01—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel characterised by the phase
  • F17C2223/0107—Single phase
  • F17C2223/013—Single phase liquid
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2225/00—Handled fluid after transfer, i.e. state of fluid after transfer from the vessel
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
  • F17C2227/01—Propulsion of the fluid
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
  • F17C2227/03—Heat exchange with the fluid
  • F17C2227/0302—Heat exchange with the fluid by heating
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
  • F17C2227/03—Heat exchange with the fluid
  • F17C2227/0367—Localisation of heat exchange
  • F17C2227/0388—Localisation of heat exchange separate
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
  • F17C2227/03—Heat exchange with the fluid
  • F17C2227/0367—Localisation of heat exchange
  • F17C2227/0388—Localisation of heat exchange separate
  • F17C2227/0393—Localisation of heat exchange separate using a vaporiser
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
  • F17C2227/04—Methods for emptying or filling
  • F17C2227/041—Methods for emptying or filling vessel by vessel
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2250/00—Accessories; Control means; Indicating, measuring or monitoring of parameters
  • F17C2250/06—Controlling or regulating of parameters as output values
  • F17C2250/0605—Parameters
  • F17C2250/0631—Temperature
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2265/00—Effects achieved by gas storage or gas handling
  • F17C2265/03—Treating the boil-off
  • F17C2265/032—Treating the boil-off by recovery
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2270/00—Applications
  • F17C2270/01—Applications for fluid transport or storage
  • F17C2270/0102—Applications for fluid transport or storage on or in the water
  • F17C2270/0105—Ships
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2270/00—Applications
  • F17C2270/01—Applications for fluid transport or storage
  • F17C2270/0102—Applications for fluid transport or storage on or in the water
  • F17C2270/011—Barges

Definitions

• the invention relates to the field of liquefied gas storage facilities, in particular facilities on board floating structures, such as LNG carriers or others.
• a liquefied gas storage installation in particular for storing LNG, can for example be an onshore storage installation, a storage installation placed on a seabed, or an installation on board a floating, coastal or in deep water, including an LNG carrier, a floating storage and regasification unit (FSRU), a floating production and remote storage unit (FPSO) and others.
• FSRU floating storage and regasification unit
• FPSO floating production and remote storage unit
• the liquefied gas can be a combustible gas, in particular liquefied natural gas (LNG) or liquefied petroleum gas (LPG), or other.
• LNG liquefied natural gas
• LPG liquefied petroleum gas
• Certain aspects of the invention are based on the observation that the gas tests, in particular the gassing and cooling operations, produce a large quantity of evaporation gas, which it would be desirable to reduce to facilitate its treatment. , save liquefied gas, and/or reduce gas emissions into the atmosphere.
• One idea at the basis of the invention consists in exploiting the evaporation gas produced during the cooling of a tank to carry out the gassing of another tank, in particular during a gas test involving several tanks in a liquefied gas storage facility.
• the invention proposes a gassing method intended to gasse a storage tank in a liquefied gas storage installation, the liquefied gas storage installation preferably being on board a floating structure, the method comprising: placing a liquefied gas storage installation in a preparatory state, the liquefied gas storage installation comprising a plurality of storage tanks and at least one collector connected parallel to an upper portion of each of said storage tanks, a first of said storage tanks in the preparatory state being filled with a liquefied gas in the vapor phase, the liquefied gas in the vapor phase in the first tank being at a temperature higher than a liquid-vapor equilibrium temperature of said liquefied gas, a second of said storage tanks in the preparatory state being filled with an inert gas, introducing a flow of the liquefied gas in liquid phase into the first tank , to cause cooling of the first tank and partial or total vaporization of the liquefied gas in the liquid phase in the first tank, while the flow of the lique
• such a method may have one or more of the following characteristics.
• connection making it possible to conduct the flow of liquefied gas in the vapor phase from the first storage tank to the second storage tank can be made in different ways.
• said at least one manifold comprises a maintenance manifold, the maintenance manifold being connected parallel to the upper portion of each of said storage tanks via a first respective isolation valve , the flow of liquefied gas in the vapor phase being led from the upper portion of the first tank to the maintenance manifold through the first isolation valve associated with the first tank and/or from the maintenance manifold to the upper portion of the second tank through the first isolation valve associated with the second tank.
• this maintenance collector is not insulated.
• it may be a manifold connected to an inert gas production unit and usually used during tank inerting.
• said at least one manifold also comprises a steam manifold, the steam manifold being insulated, the steam manifold being connected parallel to the upper portion of each of said storage tanks via a second respective isolation valve, the vapor manifold being connected in series with the maintenance manifold, the flow of liquefied gas in the vapor phase being led successively through the first isolation valve associated with the first vessel, the manifold maintenance, the steam manifold and the second isolation valve associated with the second vessel or successively through the second isolation valve associated with the first vessel, the steam manifold, the maintenance manifold and the first isolation valve associated with the second tank.
• the flow of liquefied gas in the vapor phase from the first storage tank to the second storage tank can be achieved in different ways.
• the flow of liquefied gas in the vapor phase flows from the upper portion of the first storage tank to the upper portion of the second storage tank by natural convection. Thanks to these characteristics, the flow is achieved passively without additional energy expenditure.
• the liquefied gas storage installation further comprises a gas heater device having an inlet connected to one of the maintenance manifold and the vapor manifold and an outlet connected to the another among the maintenance collector and the vapor collector, the flow of liquefied gas in the vapor phase being further conducted through the gas heater device to be reheated before reaching the upper portion of the second tank. Thanks to these characteristics, it is possible to recover relatively cold boil-off gas, in particular the boil-off gas obtained in the first tank when the cooling operation of the first tank is in an advanced state.
• the liquefied gas storage installation further comprises a gas heater device having an inlet connected to one of the maintenance collector and the vapor collector and an outlet connected to the another of the maintenance collector and the vapor collector, and, during a first flow period, the flow of liquefied gas in the vapor phase flows from the upper portion of the first storage tank to the upper portion of the second storage vessel by natural convection, and during a second flow period, the flow of liquefied gas in the vapor phase is further led through the gas heater device to be reheated before reaching the upper portion of the second tank.
• the method further comprises the steps of: monitoring a temperature of the liquefied gas in the vapor phase leaving the first vessel during the first flow period, and switching the flow of liquefied gas in the vapor phase to the heater device when the temperature of the liquefied gas in the vapor phase satisfies a predetermined criterion.
• a natural flow can be achieved at the start of the cooling operation of the first tank until a predetermined criterion is reached, for example a temperature threshold below which the gas liquefied in phase vapor becomes too dense to perform the gassing operation.
• the flow is then switched to the heater to continue the gassing operation of the second storage tank.
• the flow of liquefied gas in the liquid phase can be produced in several ways, for example outside or inside the liquefied gas storage installation. According to embodiments, the flow of liquefied gas in the liquid phase is conducted from a land terminal or from a supply ship to which the liquefied gas storage facility is connected.
• the liquefied gas storage installation comprises a third storage tank and a spray manifold connected parallel to each of said storage tanks, the third storage tank in the preparatory state being partially or completely filled with the liquid phase liquefied gas, and the flow of the liquid phase liquefied gas is pumped into the third tank and led to the first tank through the spray manifold.
• the flow of liquefied gas in the liquid phase is sprayed into the first storage tank by a spray device.
• the liquefied gas storage installation comprises a liquid collector connected parallel to a lower portion of each of said storage tanks and a degassing mast connected to the liquid collector, and the flow of inert gas leaving the second tank is led through the liquid collector to the degassing mast.
• the invention also provides a method for carrying out gas tests in a liquefied gas storage installation on board a floating structure, said gas tests comprising: putting the second storage tank under gas by the aforementioned method and, after the second storage tank is gassed, introducing a flow of liquefied gas in the liquid phase into the second tank, to cause cooling of the second storage tank.
• the invention also provides a liquefied gas storage installation, the liquefied gas storage installation being preferably on board a floating structure and comprising: a plurality of storage tanks, a collector maintenance connected parallel to an upper portion of each of said storage tanks via a respective first isolation valve, a steam collector connected parallel to the upper portion of each of said storage tanks via a respective second isolation valve, the vapor collector being insulated, a liquid collector connected parallel to a lower portion of each of said storage tanks, the liquid collector being insulated, and a degassing mast connected to the liquid collector, the first isolation valves being switchable to selectively place the maintenance manifold in communication with the upper portion of a pr first of said storage tanks to conduct a flow of liquefied gas in the vapor phase from the first storage tank to the maintenance manifold through the first isolation valve associated with the first storage tank.
• such a liquefied gas storage facility may have one or more of the following characteristics.
• each of said storage tanks comprises a filling line connected to the liquid collector and a vapor line opening into the upper portion of the storage tank and connected parallel to the maintenance collector by the first valve associated with the storage tank and the vapor collector by the second isolation valve associated with the storage tank.
• the steam manifold is connected in series with the maintenance manifold, the second isolation valves being switchable to selectively put the steam manifold in communication with the upper portion of a second of said tanks tank to conduct the flow of liquefied gas in the vapor phase from the first storage tank to the second storage tank successively through the first isolation valve associated with the first storage tank, the maintenance manifold, the manifold steam and the second isolation valve associated with the second storage tank.
• the liquefied gas storage installation further comprises a spray manifold connected parallel to each of said storage tanks, and a spray device arranged in the upper portion of each of said tanks and connected to the spray collector.
• the liquefied gas is liquefied natural gas.
• the floating structure is a vessel for transporting a liquefied gas.
• a vessel for the transport of a liquefied gas may comprise a double hull and storage tanks arranged in the double hull.
• the storage tanks are made with a membrane technique and the double shell comprises an internal shell forming the bearing wall of the storage tanks.
• the invention also provides a test system for carrying out a gas test, the system comprising an aforementioned liquefied gas storage installation, insulated pipes arranged so as to connect the liquid collector or the spray manifold at a land terminal and a pump for driving a flow of liquid phase liquefied gas through the insulated pipes from the land terminal to the liquid manifold or the spray manifold.
• Figure 1 is a diagram partially representing a liquefied gas storage and handling system in which methods according to the invention can be implemented.
• Figure 2 is a view similar to Figure 1, illustrating the liquefied gas storage and handling system in a state preceding a gassing operation of a tank.
• Figure 3 is a view similar to Figure 1, illustrating the liquefied gas storage and handling system in a first phase of the operation of gassing a tank.
• Figure 4 is a graph illustrating the time evolution of the state of a tank during a gassing operation.
• Figure 5 is a view similar to Figure 1, illustrating the system for storing and handling liquefied gas in a second phase of the operation of gassing a tank.
• Figure 6 is a view similar to Figure 1, illustrating the liquefied gas storage and handling system in a third phase of the gas filling operation of a tank.
• FIG.7 Figure 7 is a timing diagram illustrating a test procedure implemented in a liquefied gas storage and handling system.
• Figure 8 is a cutaway schematic representation of an LNG carrier connected to a loading/unloading terminal.
• FIG 1 there is shown schematically an LNG storage facility capable of being embarked on a floating structure, for example on an LNG carrier.
• Three storage tanks 10A, 10B and 10C are shown for illustrative purposes, but this number could be higher or lower.
• the tanks can be arranged successively in the length of the ship's hull or can be arranged differently.
• the storage tanks have sealed and insulating walls which can be manufactured by different techniques, for example by a double membrane technique or the like.
• Each storage tank 10A-C comprises in particular:
• liquid manifold 1 to which the filling lines 9 of all the tanks are connected and the spray manifold 3 to which the spray ramps 5 of all the tanks are connected can be connected to d other fluid circuits.
• liquid manifold 1 and spray manifold 3 are connected to a transshipment circuit to send and receive fluids to and from a shore terminal or another vessel.
• a single steam pipe 6 has been provided here to connect the maintenance collector 4 and the steam collector 2 in parallel to the interior space of the tank.
• two separate steam lines could be provided.
• the spray collector 3, the liquid collector 1 and the vapor collector 2 are intended to conduct cold fluids and are therefore preferably insulated.
• the maintenance manifold 4 is not or only slightly insulated because its usual function is to conduct inert gas from an inert gas production unit (not shown) for the inerting operations of the tanks and pipes.
• FIG. 1 there is also shown a bent connection 19 connecting one end of the maintenance manifold 4 to the steam manifold 2, in order to form a particularly long circulation path, the use of which will be explained with reference to FIG. 3.
• This elbow connection 19 is optional.
• a gas heater 14 is connected via isolation valves to the maintenance manifold 4, for example at the outlet of the gas heater 14, and to the vapor manifold 2, for example at the inlet of the gas heater 14.
• a vaporization unit 15 is connected via isolation valves to the spray manifold 3, for example at the inlet of the vaporization unit 15, and to the vapor manifold 2, for example at the outlet. of the vaporization unit 15.
• the vapor collector 2 can be connected to equipment consuming gases in the vapor phase, as outlined by the connection 18, for example to a combustion unit or a propulsion engine.
• the tank 10A is therefore filled with natural gas in the vapor phase 21 at room temperature and the tank 10B is filled with an inert gas 22 at room temperature, for example dinitrogen or a gas rich in carbon dioxide from oil combustion.
• an inert gas 22 at room temperature, for example dinitrogen or a gas rich in carbon dioxide from oil combustion.
• FIG. 2 Another storage tank which is partially filled with liquefied gas in the liquid phase in the preparatory state is shown in broken lines in Figure 2.
• the spray manifold 3 is also connected to this other tank.
• Figure 3 shows a first phase of the simultaneous operation of cooling tank 10A and gassing tank 10B.
• a flow of LNG 25 is introduced into tank 10A via spray collector 3 and sprayed by spray boom 5 to cool tank 10A.
• the LNG vaporizes by yielding its latent energy of vaporization in the tank 10A, which creates a surplus of natural gas in the vapor phase.
• This surplus of natural gas in the vapor phase must be evacuated from the tank 10A as it is produced to avoid an increase in the pressure in the tank 10A.
• a circulation path is created in order to conduct a flow of natural gas in the vapor phase 26 from the tank 10A to the tank 10B to effect the gassing of the tank 10B.
• the LNG flow 25 can be pumped into the other tank and led to tank 10A via spray collector 3.
• the arrows 26 show a circulation path leaving the tank 10A towards the maintenance manifold 4 via the steam line 6 and the isolation valve 11, traversing the entire length of the maintenance manifold 4 up to the elbow connection 19 and continuing in the steam collector 2 to the steam line 6 of the tank 10B.
• This circulation path can be configured using isolation valves 11 and 12:
• the pressure in vessel 10B is maintained at a lower pressure than vessel 10A by allowing a stream of inert gas 27 via the filling pipe 9, the liquid collector 1 and a degassing mast 13 connected to the liquid collector 1 .
• This is preferably the foremast, furthest from the castle of the ship.
• the relative pressure in tank 10B during the gassing can be for example about 60 mbar (6 kPa), while the relative pressure in tank OA can be for example between 150 mbar (15 kPa) and 180 mbar (18 kPa) .
• Figure 4 is a graph illustrating a change in the thermodynamic state of the tank 10A during the cooling operation.
• the abscissa axis represents the time expressed in hours.
• the ordinate axis on the right represents the temperature of the gaseous phase in the tank 10A expressed in degrees Celsius (°C) and the curve 41 represents the evolution of the temperature of the gaseous phase from the ambient temperature (here 30°C ) down to about -130°C.
• the ordinate axis on the left represents a mass flow rate of evaporation gas expressed in kg/h and the curve 42 represents the evolution of the mass flow rate of evaporation gas leaving the tank 10A, from an initially zero flow rate at the beginning of the operation.
• the cooling operation can last about 15 hours for a large capacity tank.
• the switching of the flow of natural gas in the vapor phase 26 to the gas heater 14 to launch the second phase can be manual or automated.
• the criterion for ending the first phase and starting the second phase can be a criterion of temperature or density of the vapor phase.
• the achievement of this criterion can be monitored by a human operator or automated by a control system.
• the excess gas natural vapor can be directed to gas consuming equipment, for example via link 18.
• the two phases described above for gassing the storage tank 10B make it possible to use the evaporation gas which is inevitably produced during the cooling operation of the storage tank 10A.
• the use of two phases is not mandatory for this. For example, if the gassing of tank 10B is complete before the temperature of the evaporation gas in tank 10A has fallen too low, the second phase is not necessary.
• a time overlap between the cooling operation of tank 10A and the operation of gassing tank 10B can therefore be total or partial.
• the vessel 10A cooling operation is complete before the vessel 10B gassing operation is complete, it is possible to complete the tank 10B gassing operation by any conventional method, as shown in Figure 6.
• the storage tank 10A has been partially filled with LNG in the liquid phase after cooling.
• a flow of LNG 30 is pumped into the liquid phase 23 stored in the bottom of the tank 10A using the spray pump 7 and led to the unit of vaporization 15, for example via the spray collector 3.
• the vaporization unit 15 thus produces a flow of vaporized natural gas 29, for example at a temperature of about 20° C., which is led to the storage tank 10B to complete the gassing operation.
• FIG. 7 is a timing diagram illustrating a time sequence of operations that can be used to perform gas tests in an LNG carrier comprising four storage tanks with similar capacities and arranged successively along the length of the ship.
• Tank A refers to the tank located at the stern of the ship and tank D to the tank located at the front of the ship.
• the abscissa axis represents the time expressed in hours.
• Steps 101 to 104 are carried out in conjunction with an external source of LNG, namely an onshore terminal or a supply ship to which the LNG carrier is connected. Steps 105 to 118 can be performed at sea, so without incurring the cost of renting a land terminal.
• the frames 100 of FIG. 7 underline the fact that the cooling operation of a tank can be carried out each time in partial or total temporal overlap with the gas operation of the following tank, except the cooling of the last tank of course.
• the boil-off gas generated by the cooling can be used for gassing by the methods described above. This results in a significant reduction in the total quantity of boil-off gas produced by the gas tests conducted by this procedure, compared to the conventional synchronous procedure.
• This reduced quantity of evaporation gas is easier to manage, either by reliquefaction, or by combustion, or by return to the terminal, or by evacuation into the atmosphere and therefore leads to a benefit in all cases.
• This benefit can be a reduction in operational costs and/or an environmental benefit (reduction of emissions).
• the gas tests can be implemented in tanks on board one or more ships. In the case of several vessels, these must be connected in order to be able to exchange fluids during the gas test procedure.
• a collector for example the steam collector, can be understood as the meeting of the steam collectors of the different ships connected to each other.
• a cutaway view of an LNG carrier 70 shows a sealed and insulated tank 71 of generally prismatic shape mounted in the double hull 72 of the ship.
• the wall of the tank 71 comprises a primary leaktight barrier intended to be in contact with the LNG contained in the tank, a secondary leaktight barrier arranged between the primary leaktight barrier and the double hull 72 of the ship, and two insulating barriers arranged respectively between the primary waterproof barrier and the secondary waterproof barrier and between the secondary waterproof barrier and the double hull 72.
• loading/unloading pipes 73 arranged on the upper deck of the ship can be connected, by means of appropriate connectors, to a maritime or port terminal to transfer a cargo of LNG from or to the tank. 71 .
• FIG. 8 represents an example of a maritime terminal comprising a loading and unloading station 75, an underwater pipe 76 and an installation on land 77.
• the loading and unloading station 75 is a fixed offshore installation comprising a movable arm 74 and a tower 78 which supports the movable arm 74.
• the movable arm 74 carries a bundle of insulated flexible pipes 79 which can be connected to the loading/unloading pipes 73.
• the adjustable movable arm 74 adapts to all sizes of LNG carriers.
• a connecting pipe, not shown, extends inside the tower 78.
• the loading and unloading station 75 allows the loading and unloading of the LNG carrier 70 from or to the shore installation 77.
• This comprises liquefied gas storage tanks 80 and connecting pipes 81 connected by the underwater pipe 76 to the loading or unloading station 75.
• the underwater pipe 76 allows the transfer of the liquefied gas between the loading or unloading station 75 and the shore installation 77 over a great distance, for example 5 km, which makes it possible to keep the LNG carrier 70 at a great distance from the coast during loading and unloading operations.
• pumps on board the ship 70 and/or pumps fitted to the shore installation 77 and/or pumps fitted to the loading and unloading station are used. 75.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Filling Or Discharging Of Gas Storage Vessels (AREA)

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Citations (6)

• 2020
  • 2020-12-10 FR FR2012970A patent/FR3117572B1/fr active Active
• 2021
  • 2021-12-09 KR KR1020237021252A patent/KR20230112138A/ko unknown
  • 2021-12-09 JP JP2023535323A patent/JP2023553928A/ja active Pending
  • 2021-12-09 WO PCT/EP2021/085106 patent/WO2022122982A1/fr active Application Filing
  • 2021-12-09 CN CN202180083286.2A patent/CN116601421A/zh active Pending

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