JP5691422B2 - LNG acceptance structure - Google Patents

Description

 The present invention relates to an LNG (Liquefied Natural Gas) receiving structure.

  The composition, density (weight), and the like of LNG vary depending on the production area. In recent years, with an increase in LNG demand, development of a heterogeneous LNG mixed storage technology for storing a plurality of types of LNG having different densities in the same LNG tank has been promoted. While this heterogeneous LNG storage technology has great economic benefits such as promoting LNG transactions and distribution and reducing equipment costs, it can also handle rollover caused by stratification within the LNG tank. It is necessary to take.

  Stratification means that when multiple types of LNG with different densities are introduced into the LNG tank, large (heavy) LNG accumulates downward, and low density (light) LNG accumulates upward, resulting in multiple different densities. This means that a liquid layer is formed. Rollover is the heat energy accumulated in the lower layer until the layer boundary disappears when the density difference between the upper and lower layers decreases due to heat input from outside in the LNG tank layered as described above. Refers to a phenomenon in which a large amount of BOG (Boil Off Gas) is generated from the liquid surface in a short time.

  When BOG exceeding the processing capacity of the BOG compressor occurs due to this rollover, it is necessary to operate the safety valve to discharge excess BOG outside the tank in order to suppress an increase in the pressure in the tank. If BOG exceeding the surplus BOG discharge capacity is generated, the increase in the pressure in the tank cannot be suppressed and the tank itself may be damaged. In order to avoid the occurrence of rollover, it is necessary to suppress stratification in the LNG tank as much as possible.

 Conventionally, two receiving pipes penetrating the roof of the LNG tank are provided, and a lead pipe extending to the bottom of the LNG tank is provided below one receiving pipe, and heavy LNG is received from the upper part of the tank through the receiving pipe. On the other hand, light LNG is received from the lower part of the tank through a receiving pipe and a lead pipe, thereby promoting mixing of different types of LNG and suppressing layering (see Patent Documents 1 and 2 below).

JP-A 63-135698 JP 2000-281178 A

  A hopper that receives LNG discharged from the lower end of the receiving pipe is provided at the upper end of the lead pipe. When light LNG is introduced through the reed pipe while heavy LNG is accumulated in the LNG tank, it is difficult for light LNG to be discharged from the lower end of the reed pipe due to the density difference between the two LNG, and light LNG can overflow from the hopper. There is sex.

  When light LNG overflows from the hopper in this way, the light LNG accumulates on the heavy LNG accumulated in advance, which causes layering that causes rollover. That is, in the conventional LNG receiving structure, the risk of rollover still remains, and it was necessary to take a solution immediately.

   The present invention has been made in view of the above-described circumstances, and an object of the present invention is to minimize the risk of rollover when a plurality of types of LNG having different densities are stored in the same LNG tank.

 In order to achieve the above object, in the present invention, as a first solving means related to the LNG receiving structure, a lead pipe installed below the receiving pipe that penetrates the roof of the LNG tank and extending to the bottom of the LNG tank; A hopper that is provided at the upper end of the lead pipe and receives the LNG discharged from the receiving pipe, and a gas that the LNG discharged from the receiving pipe drops while decelerating the central portion of the lead pipe and is separated from the LNG Gas-liquid separation structure disposed in the lead pipe, and a gas exhaust provided in the hopper for discharging the gas rising from the lead pipe to the outside of the hopper so that the gas rises along the inner wall of the lead pipe. And an outlet.

  Further, in the present invention, as the second solving means related to the LNG receiving structure, in the first solving means, the gas-liquid separation structure is configured such that the tubular member whose diameter is gradually reduced toward the lower side is replaced with the lead pipe. It is characterized by being arranged in a plurality on the central axis line.

 According to the LNG receiving structure according to the present invention, even when light LNG is introduced through the lead pipe while heavy LNG is accumulated in the LNG tank, the light LNG hardly overflows from the hopper, that is, the cause of occurrence of rollover. Therefore, the risk of rollover can be minimized.

It is the perspective view (a) of the LNG receiving structure in this embodiment, and the AA arrow sectional drawing (b) of an LNG receiving structure. It is explanatory drawing regarding the effect of the LNG receiving structure in this embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
Fig.1 (a) is a perspective view of the LNG receiving structure in this embodiment, FIG.1 (b) is AA arrow sectional drawing of an LNG receiving structure.

 In these drawings, reference numeral 1 denotes a lead pipe that is installed below the receiving pipe 102 that penetrates the roof of the LNG tank and extends to the bottom of the LNG tank. Reference numeral 2 denotes a hopper that is provided at the upper end of the reed tube 1 and that receives LNG discharged from the receiving tube 102. Reference numeral 3 denotes a reed tube 1 so that the LNG discharged from the receiving tube 102 falls while decelerating the central portion of the reed tube 1, and the gas separated from the LNG rises along the inner wall of the reed tube 1. It is a gas-liquid separation structure arranged inside. Reference numeral 4 is a gas discharge port provided in the hopper 2 for discharging the gas rising from the lead pipe 1 out of the hopper 2.

 The gas-liquid separation structure 3 is configured by arranging cylindrical members 3 a, 3 b, 3 c, and 3 d that gradually reduce in diameter downward on the central axis 1 a of the lead tube 1. In addition, in FIG. 1, although the state where the four cylindrical members 3a, 3b, 3c, and 3d are arrange | positioned in the lead tube 1 is illustrated, the number of arrangement | positioning of a cylindrical member is not limited to four, It can be appropriately changed as necessary.

Next, the function and effect of the LNG receiving structure configured as described above will be described.
Light LNG unloaded from the LNG tanker is transferred to the LNG tank through the receiving pipe 102. This light LNG is a gas-liquid mixed fluid containing flash gas (hereinafter abbreviated as gas). As shown in FIG. 2, the light LNG discharged from the receiving pipe 102 to the hopper 2 first falls from the upper opening of the tubular member 3a into the tubular member 3a. As described above, since the cylindrical member 3a is gradually reduced in diameter toward the lower side, the flow rate of light LNG is decelerated in the cylindrical member 3a.

 Light LNG discharged from the lower opening of the cylindrical member 3a falls into the cylindrical member 3b from the upper opening of the lower cylindrical member 3b, and decelerates in the cylindrical member 3b. Light LNG discharged from the lower opening of the cylindrical member 3b falls from the upper opening of the lower cylindrical member 3c into the cylindrical member 3c, and decelerates in the cylindrical member 3c. Light LNG discharged from the lower opening of the cylindrical member 3c falls from the upper opening of the lower cylindrical member 3d into the cylindrical member 3d, and decelerates in the cylindrical member 3d.

 Thus, in the process in which light LNG falls while decelerating the central portion of the reed tube 1, gas-liquid separation of light LNG is promoted, and gas is separated from light LNG. The separated gas rises along the inner wall of the lead pipe 1 and is discharged to the outside from a gas discharge port 4 provided in the hopper 2.

 As described above, when gas-liquid separation is promoted in the process in which light LNG falls while decelerating the central portion of the lead tube 1, the density of light LNG increases as the drop distance increases. That is, if light LNG is introduced through the lead pipe 1 while heavy LNG is accumulated in the LNG tank, the density difference between the two LNG can be reduced, so that light LNG can be easily discharged from the lower end of the lead pipe 1. Light LNG is less likely to overflow from the hopper 2. Therefore, according to the present embodiment, the layering that causes the rollover is less likely to occur, and the risk of the rollover can be minimized.

 In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably. For example, in the said embodiment, the gas-liquid separation structure 3 comprised by arrange | positioning the cylindrical members 3a, 3b, 3c, and 3d which reduce diameter gradually toward the downward direction on the central axis 1a of the lead pipe 1 is illustrated. However, in this gas-liquid separation structure 3, the LNG discharged from the receiving pipe 102 falls while decelerating the central portion of the lead pipe 1, and the gas separated from the LNG rises along the inner wall of the lead pipe 1. Any structure may be used as long as it has a structure.

 DESCRIPTION OF SYMBOLS 1 ... Lead pipe, 2 ... Hopper, 3 ... Gas-liquid separation structure, 3a, 3b, 3c, 3d ... Cylindrical member, 4 ... Gas exhaust port, 102 ... Receiving pipe

Claims (1)

A lead pipe installed below a receiving pipe penetrating the roof of the LNG tank and extending to the bottom of the LNG tank;
A hopper provided at an upper end of the lead pipe and receiving LNG discharged from the receiving pipe;
A plurality of cylindrical members that gradually decrease in diameter downward are arranged on the central axis of the lead pipe, and LNG discharged from the receiving pipe decelerates the central portion of the lead pipe. A gas-liquid separation structure disposed in the lead pipe so that the gas that has fallen and separated from the LNG rises along the inner wall of the lead pipe;
A gas discharge port provided in the hopper and for discharging the gas rising from the lead pipe to the outside of the hopper;
LNG receiving structure characterized by comprising.

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