FR2851301A1 - Gaseous fuel supplying equipment for ship, has accumulator connected to supply collector of energy production assembly by valve and having gas under pressure greater than supply pressure - Google Patents

Abstract

The equipment has a compressor (5) driven by a motor (6) and having input aspired in a tank (2), and an exit provided into a supply collector of an energy production assembly (1). A submerged pump (3) at bottom of the tank is connected to an input of an evaporator (4) whose output is connected to the collector. An accumulator (7) connected to the collector by valve (7) has gas under a pressure greater than supply pressure.

Description

The invention relates to an installation for the supply of fuel.

  gas to an energy production unit of a liquefied gas transport vessel, this gaseous fuel being compressed to a certain supply pressure by one or more devices before supplying the energy production unit through at least one collector .

  The invention relates to the regulation and control of the pressurized gas supply of the electric power generator with gas supply of a liquefied gas transport vessel, this assembly possibly comprising, for example, one or more diesel generator sets. or one or more gas turbines. The operating characteristics of an electric power generator with gas supply generally imply that this gas supply is carried out under a low supply pressure which may for example be of the order of six bars. In steady state, this supply is generally carried out under correct conditions by the existing compression apparatuses which are capable of delivering the desired flow rate and pressure. These devices which include for example a compressor and / or a pump supplying an evaporator are generally controlled by a pressure regulator situated at the level of the manifold so as to maintain in this manifold a pressure close to the set supply pressure.

  When a sudden increase in the load applied to the electric power generator appears, this produces a rapid increase in gas consumption which generally results in a drop in the supply pressure in the manifold. In fact, given the limited volume of the manifold, the distances separating the apparatuses from the manifold and the reaction time of the apparatuses which compress the gas, the control of the pressure delivered by the compression apparatuses on the pressure regulator presents a significant hysteresis. Therefore, a certain time interval corresponding to a transient phase is necessary to restore the supply pressure in the manifold after a sudden increase in the load of the electric power generator.

  Such an increase in the load of the entire energy production may be due to a request to accelerate the speed of the ship, to the commissioning of large consumers such as cargo pumps or the like. During this transient phase, the speed of the electric power generator and the power they deliver are disturbed, so that this transition can cause the unwanted shutdown of the electric power generator due to lack of fuel gas pressure.

  On the other hand, when the load of the energy production assembly is low, for example when the ship is sailing at low speed, the compressor (s) which are usually used for their gas supply are not sized or designed to provide a low gas flow at a pressure around six bars. The operation of the assembly is therefore not satisfactory, which could even cause the gas supply to stop.

  To date, this problem has not been highlighted and has not been the subject of any previous study.

  The object of the invention is to remedy this drawback.

  To this end, the subject of the invention is an installation for supplying gaseous fuel to an energy production unit of a liquefied gas transport vessel, from the contents of at least one tank of said vessel, comprising at least minus a compressor driven by a motor, the inlet of which draws into said tank, the outlet of the compressor delivering into a supply manifold of said energy production unit, and a submerged pump at the bottom of the tank connected to the inlet of an evaporator, the outlet of the evaporator being connected to said supply manifold of said energy production assembly, and characterized in that it comprises a buffer tank containing gas originating from the tanks of the ship under a pressure greater than the pressure of supply, this buffer tank 25 being connected to the collector via a valve, this valve being intended to gradually discharge the buffer tank into the manifold to regulate the pressure in the event of a sudden increase in the load of the energy production assembly tending to cause the supply pressure to drop temporarily.

  In this way, the supply conditions for the energy production assembly are optimal, including during the transient phases of sudden increase in load.

  According to a preferred embodiment, the buffer tank is supplied with gas by a dedicated compressor, receiving gas taken for example from the tanks or a supply pipe for the energy production assembly or by a dedicated pump, taking liquid gas for example in a tank or in the supply manifold of the main forced vaporizer. This compressor or this pump can be controlled by a pressure regulator fitted to the buffer tank so as to maintain a predetermined pressure in the buffer tank. The buffer tank thus has an autonomous operation which allows it to fill automatically when a transient phase is finished and thus to be permanently in a position to compensate for any further sudden drop in gas pressure in the manifold.

  According to the invention, the supply gas is compressed by at least one compressor driven by a motor controlled by an automaton, and in the event of a low load of the electric power generator, the automaton controls the various parameters of the motor-compressor assembly, that is to say for example the speed of rotation of the motor or the pitch of the blades of the compressor to adjust the supply pressure of the electric power generator. In fact, the necessary supply pressure of the energy production assembly decreases when the load of the latter decreases.

  According to a preferred embodiment of the invention, the automaton controls the pitch of the blades of the compressor to adjust the supply pressure to the value most suited to the load of the electric power generator. In this way the compressor is operated under more favorable technical and economic conditions, the discharges being reduced due to the combustion of the necessary amount.

  The invention will now be described in more detail, and with reference to the accompanying drawings which illustrate an embodiment by way of non-limiting example.

  Figure 1 is a schematic representation of a first embodiment of the invention; Figure 2 is a schematic representation of a second embodiment of the invention.

  Figure 1, the elements dedicated to the production of energy on an LNG carrier are shown schematically, here they include a set of diesel alternators 1 for producing an electric current. As is commonly the case with LNG carriers, the energy production unit 1 is supplied with gas which is taken from one or more tanks 2 of the LNG carrier. The feed gas is most often methane which is taken directly from the tanks by being placed under a feed pressure of a few bars.

  This feed gas is taken in parallel in two ways. On the one hand, a pump 3 submerged at the bottom of the tank and electrically supplied takes liquid methane 2 'which is led into a main evaporator 4 through a regulation valve 4'. At the outlet of the main evaporator 4, the methane is in gaseous form, at the desired supply pressure to supply the supply manifold of the diesel-alternator assembly 1 10 via a supply line . On the other hand, evaporated gas 2 "is also taken from the tank, above the surface of the liquid methane 2 'to be compressed in a compressor 5 which is driven by an electric motor 6. This gas is then injected into the collector together with the methane from the main evaporator 4. 15 A valve 1 'is connected to the supply line to evacuate gas to the atmosphere or a burner in the event of overpressure in this line, this is to say in the collector Such an overpressure can for example occur following a sudden drop in the charge of the diesel-alternator assembly 1, leading to a sudden drop in their gas consumption.

  According to the invention a buffer tank 7 is placed upstream of the manifold of the diesel-alternator assembly so as to compensate for a sudden drop in supply pressure in this manifold. This buffer tank 7 is inflated to a high pressure which is higher than the supply pressure 25 of the diesel-alternator assembly, which makes it possible to limit its volume to a few cubic meters or less. When the load of the diesel generator set 1 increases suddenly, a valve 7 'located downstream of this tank and connected to the gas supply pipe of the energy production unit 1 opens to discharge part of the content 30 of this buffer tank 7 in the supply line. This makes it possible to compensate during the transient phase for the drop in supply pressure due to the sudden increase in load of the diesel-alternator assembly 1, in order to maintain the supply pressure at its set value. The valve 7 ′ can be controlled in particular by a pressure regulator 35 fitted to the manifold and more generally be controlled by a regulation automaton.

  Advantageously, this buffer tank 7 is supplied with gas by a compressor 8 which is dedicated to it and which is controlled by a pressure regulator 7 "fitted to the buffer tank 7, so as to maintain, for example, a pressure of one hundred bars permanently available in the 5 buffer tank 7. When the pressure in the buffer tank 7 is lower than the pressure regulating pressure of the pressure regulator 7 ", the compressor thus automatically starts to bring the pressure up to a hundred bars. A non-return valve 8 'is mounted between the compressor 8 and the buffer tank 7 so as to avoid a return of the compressed gas to the compressor 8. In the example of FIG. 1, this compressor 8 collects gas directly in the supply line for the diesel-alternator assembly 1, namely gas from the compressor 5 and the main evaporator 4 to inflate the buffer tank.

  In another embodiment shown in FIG. 2, the gas which feeds the buffer tank 7 comes from the gas in the liquid phase of the tank. As can be seen in FIG. 2, a pump 10 delivers liquid methane into a secondary evaporator 10 'to supply the buffer tank 7, this pump 10 being controlled by a pressure regulator 7 "fitted to the buffer tank 7. More particularly, the liquid methane is vaporized in the secondary evaporator 10 'before being injected into the buffer tank 7.

  The invention also relates to the regulation of the gas supply when the diesel-alternator assembly is subjected to a low load. In this case, the compressor 5 which is conventionally a centrifugal compressor 25 must operate so as to maintain a certain supply pressure while producing a low flow rate. Centrifugal compressors that are commonly used are not sized or designed to provide a low flow of gas at a supply pressure usually around six bars. Operating them with such parameters leads to unsatisfactory operations.

  According to the invention, the supply pressure is reduced when the load of the energy production assembly is low. When the load is low, the ideal supply pressure is actually lower than the supply pressure of six bars which is only necessary when the diesel-generator set is operating at high speed. According to the invention, the supply motor 6 and the compressor 5 are therefore controlled to provide a lower pressure when the load of the diesel-alternator assembly is low. This allows both the compressors 5 to operate under more favorable conditions.

  In the example illustrated in FIGS. 1 and 2, a centralized automaton 9 is connected to the motor 6 and to the compressor 5 to modify their operating parameters. This automaton 9 receives as input data including the load of the diesel-alternator assembly 1, as well as other instantaneous values of pressure and flow rate. It acts at the output on the engine 6 and on the compressor 5 to vary the supply pressure and adjust the desired flow 10 when the load of the diesel-alternator assembly 1 is low. The compressor 5 may for example include blades with variable pitch controlled by the automaton 9 to adjust the supply pressure to the most suitable value. The supply pressure may for example be six bars when the load of the energy production unit 15 is maximum, and drop to four and a half bars when the load is twenty percent of the maximum load.

Claims (5)

  1 / Installation for the supply of gaseous fuel to an assembly (1) of energy production of a liquefied gas transport vessel, from the content of at least one tank (2) of said vessel, comprising at least one compressor (5) driven by a motor (6), the inlet of which sucks in said tank (2), the outlet of the compressor (5) delivering into a supply manifold of said assembly (1) for energy production, and a pump (3 ) submerged at the bottom of the tank (2) connected to the inlet of an evaporator (4), the outlet of the evaporator (4) being connected to said supply manifold of said assembly (1) for energy production, characterized in that it comprises a buffer tank (7) containing gas coming from the tanks (2) of the ship under a pressure higher than the supply pressure, this buffer tank (7) being connected to the manifold by means of a valve (7 ').   2 / Installation according to claim 1, wherein the buffer tank (7) is supplied with gas by a dedicated compressor (8) receiving gas taken from a supply pipe for the assembly (1) of energy production, this compressor (8) being controlled by a pressure regulator 20 (7 ") fitted to the buffer tank (7).   3 / Installation according to claim 1, in which the buffer tank (7) is supplied with gas by a dedicated pump (10) receiving liquid gas coming from the tank (2), the gas leaving this pump passing through a secondary vaporizer (10 ') before being injected into the buffer tank (7), this pump (10) being controlled by a pressure regulator (7 ") fitted to the buffer tank (7).   4 / Installation according to the preceding claims, in which the compressor (5) and / or the motor (6) are controlled by an automaton (9) to vary the gas supply pressure of the assembly (1) of energy production.   5 / Installation according to claim 4, wherein the controller (9) controls the pitch of the blades of the compressor (5).