JPH04254096A - Double pipe type open rack type evaporator - Google Patents

Abstract

PURPOSE:To prevent flow rate hunting, reduce adfreezing, reduce sea water quantity and stabilize gas flow by employing double pipe structure for heat exchanging pipes to reduce adfreezing to the surface of a thermal exchanging panel. CONSTITUTION:A exchange panel comprises many heat exchanging pipes of double pipe-structure arranged in parallel, and the upper end of an inner pipe 11 is connected to an LNG inlet header tank 12 enabling LNG to enter and flow and closing the upper end section of an outer pipe 10 by the header tank 12. Double pipe type heat exchanging pipe constitution reduces the adfreezing to the surface of the outer pipe 10 and also enables the miniaturization of an evaporator by the increase in heat conducting area. In addition, since this constitution makes it possible to be of U type flow, the pressure loss in pipes is increased, that stabilizes the gas flow.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] This invention relates to an open rack type vaporizer for vaporizing liquefied natural gas using a heat medium such as seawater. Supply liquefied natural gas to the pipe and send it to the top of the outer pipe.
This invention relates to a double-pipe open rack type vaporizer that has a structure that extracts vaporized gas using a mold flow, which prevents flow rate hunting, reduces ice formation, reduces the amount of seawater, and stabilizes the gas flow.

0002

2. Description of the Related Art Conventionally, single-tube open rack type vaporizers have been mainstream as open rack type vaporizers for vaporizing liquefied natural gas (hereinafter referred to as LNG) using a heat medium such as seawater. As shown in Fig. 8, the single-tube open rack type vaporizer supplies LNG from a lower header tank 2 installed at the lower end of a heat exchange panel 1 that has a number of single-tube heat exchange tubes arranged in parallel. As the LNG rises inside the pipe, it is heated and vaporized by seawater, which is a heat medium outside the pipe, by the seawater sprinkled from the troughs 3 arranged on both sides of the upper part of the panel 1. It has a configuration in which natural gas (hereinafter referred to as NG) is supplied to the outside from a tank 4.

[0003] The single-tube open rack type vaporizer has a simple structure and is easy to manufacture as described above; Since direct heat exchange is performed, there is a problem in that ice builds up on the outside of the tube, that is, on the surface of the heat exchange panel 1.

[0004] To be more specific, if there is an imbalance in the flow rate of water supplied to each heat exchange tube of the heat exchange panel 1, an imbalance occurs in the height of ice formation on the outside surface of the tubes. As the LNG flow rate increases, the amount of unbalanced icing increases. As a result, the temperature of each heat exchange tube itself becomes non-uniform, a difference occurs in the amount of contraction of each heat exchange tube, and thermal stress increases, which greatly limits the ability to improve the performance of the vaporizer.

[0005] Conventionally, therefore, in order to prevent the unbalance of ice buildup on the surface of the heat exchange panel 1, measures have been proposed to equalize the amount of water sprinkled on each heat exchange tube and to alleviate thermal stress. However, the fundamental drawbacks of the single-tube open rack type vaporizer could not be overcome.

[0006]

[Problems to be Solved by the Invention] As a method to solve this problem, a configuration in which the LNG is heated indirectly by using a double heat exchange tube is considered, but the heat transfer efficiency is poor and the temperature of the NG is extremely low. There are many problems, such as the need to heat the low-temperature gas that exits the vaporizer in order to supply room-temperature gas. The optimal configuration for an LNG vaporization device, such as how to use the passage between the tube and the outer tube, has not been proposed.

[0007] The present invention provides a vaporizer in which the heat exchange tube has a double-tube structure in order to reduce the problem of ice build-up on the surface of the heat exchange panel, which has been a problem in conventional single-tube open rack type vaporizers. The aim is to provide a double-pipe open rack type vaporizer that prevents flow rate hunting, reduces ice formation, reduces seawater volume, and stabilizes gas flow.

[0008]

[Means for Solving the Problems] This invention forms a heat exchange panel by connecting a large number of heat exchange tubes with a double tube structure, and a water trough is arranged in the upper part of the panel to enable heating.
Liquefied gas is introduced into the inner tube from the inlet header tank installed at the upper or lower end of the heat exchange tube, and the fluid exiting the inner tube is reversed in the closed outer tube at the other end opposite the inlet header tank. After reversing, the fluid moving upward or downward through the annular passage between the outer tube and the inner tube can exchange heat with the water sprinkled on the outer surface of the outer tube and the liquefied gas inside the inner tube. This is a double pipe open rack type vaporizer characterized by being able to be led out from an outlet header tank connected to an outer pipe on the header tank side.

The present invention also provides a double-pipe open rack having the above structure, characterized in that a heat insulating means is provided on the outer periphery of the inner pipe on the inlet header tank side including the vicinity of the outlet to the outlet header tank. It is a type vaporizer.

0010

[Operation] This invention was developed as a result of various studies aimed at creating an open rack type vaporizer with a double pipe structure that reduces ice buildup on the LNG inlet header tank side, which was a problem with conventional open rack type vaporizers. A heat exchange panel is formed by connecting a large number of heat exchange tubes with a double tube structure, and an LNG inlet header tank and an NG outlet header tank are placed on one side of the upper or lower part of the heat exchange tubes, and the inner tube is connected from one end to the other. During the U-shaped flow in which the LNG that has been introduced is reversed from the other end and moved between the outer pipe and the inner pipe, and flows into the NG outlet header tank of the outer pipe, seawater → outer pipe → NG → inner pipe → With a configuration that inputs heat with LNG, it is possible to reduce the amount of seawater by reducing the amount of ice that would otherwise occur with conventional equipment, reduce the amount of pump used, and prevent flow rate and calorie hunting.
They also found that a vaporizer with stable NG flow could be obtained, and completed this invention.

[0011] In this invention, the double pipe structure
NG can flow downward from the upper end of the inner tube and be reversed from the opening lower end, and NG can rise through the annular passage between the outer tube and the inner tube, or LNG can be flowed upward from the lower end of the inner tube and reversed from the opening upper end. As long as the NG can descend through the annular passage between the outer tube and the inner tube, any configuration can be adopted, such as one end of the inner tube protruding from the outer tube.

[0012] Furthermore, a finned tube having star fins protruding from the outer peripheral surface can be used as the outer tube. Furthermore, it is also possible to increase the heat transfer area by providing notches or irregularities on the inner surfaces of both the inner tube and the outer tube.

[0013] Furthermore, the header tank is disposed on either the upper side or the lower side of the double-tube structure heat exchange tube so that the fluid can flow in a U-shape from the inner tube to the outer tube. For example, when the LNG inlet side is provided at the upper end of the inner tube, the NG outlet side may be located at any position on the upper side of the heat exchange panel.

In the present invention, the water sprinkling trough may have any configuration as long as it can spray seawater from the upper part of the heat exchange panel to the outer circumferential surface of the outer pipe, but at least it sprays water to the LNG inlet header tank. It is necessary to arrange the header tank so that it does not occur, and it is best to arrange it according to the position of each header tank.

[0015] In this invention, the heat insulating material coated on the upper outer periphery of the inner pipe is used to protect the NG discharged by the LNG immediately after inflow.
It must be installed so that it is not cooled, and using a known heat insulating material such as Bakelite or stainless steel, the covering position and The range, amount, etc. may be selected as appropriate.

Furthermore, instead of the heat insulating material coated on the upper outer periphery of the inner tube, a cover that can form the required space between the upper outer periphery of the inner tube and the outer periphery of the inner tube is provided around the inner tube.
As a result, L
It can be configured not to cool the NG derived from the NG. This heat insulating cover can have any configuration as long as it can retain part of the NG. For example, it can be configured so that the NG is temporarily retained by changing the degree of opening on the inlet and outlet sides of the cover. Also, known materials such as aluminum, Bakelite, and stainless steel can be used.

[0017]

[Example] Example 1 A double tube open rack type vaporizer according to the present invention shown in FIG. An LNG inlet header tank and an NG outlet header tank are provided at the top of the panel. Each heat exchange tube has an inner tube 11 inserted into an outer tube 10 having a required length and inner diameter and whose lower end is closed, but the inner tube 11 has its lower end opened at the inner bottom of the outer tube 10, Further, the upper end of the inner pipe 11 is connected to an LNG inlet header tank 12 to enable LNG to be introduced and flowed down, and the upper end of the outer pipe 10 is closed by the header tank 12.

The NG outlet header tank 14 is connected to the outer pipe 10 below the LNG inlet header tank 12.
It is arranged via an outlet pipe 13. In addition, on the outer surface of each outer pipe 10 constituting the heat exchange panel, overflow water from water troughs 15 and 16 arranged oppositely below the NG outlet pipe 13 side and below the LNG inlet header tank 12 on the opposite side flows down. do. Furthermore, a heat insulating material 17 is attached to the outer circumferential surface of the inner pipe 11 for a required length from the connection part to the LNG inlet header tank 12 and below the water sprinkling trough 1516 position below the NG outlet pipe 13 side. Further, the LNG inlet header tank 12 is also covered with a heat insulating material 18.

The supplied LNG flows downward through the inner pipe 11 from the inlet header tank 12, and is partially vaporized by being heated by NG, which will be described later, before turning over from the lower end of the opening of the inner pipe 11 to the inner bottom of the outer pipe 10. . The partially vaporized LNG is further heated while rising through the annular passage between the outer tube 10 and the inner tube 11,
The NG is led out to the NG outlet header tank 14 as NG at room temperature via the NG outlet pipe 13 connected above the outer tube 10.

[0020] In the open rack type vaporizer according to the present invention, the heat exchange tube is constructed with a double tube, so that the heat medium seawater and the cryogenic LNG do not directly exchange heat, and the NG in the annular passage is Since heat is exchanged through the outer tube 10, ice formation on the surface of the outer tube 10 is reduced, and the heat transfer area is increased, so that the vaporizer can be downsized. Therefore, by reducing ice formation, it is possible to reduce the amount of seawater to be supplied as a heat medium, and the power consumption of the seawater pump can be significantly reduced. Furthermore, by locating the LNG inlet header tank 12 to which cryogenic LNG is supplied above the troughs 15 and 16, it is possible to prevent heat from entering the LNG inlet header tank 12 from seawater, and it is possible to prevent seawater from entering the heat exchange pipes. Flow rate hunting and calorie hunting can be prevented.

Furthermore, by configuring the heat exchange tube as a double tube, NG is supplied into the outer tube 10 from the lower end of the inner tube 11, rising inside the tube and exiting from the upper end to the outside, creating a U-shaped flow. This increases the pressure loss inside the pipe and stabilizes the gas flow.

Furthermore, in the open rack type vaporizer according to the present invention, the required upper part of the inner pipe 11 to which cryogenic LNG is supplied from the LNG inlet header tank 12 is surrounded by a heat insulating material 17, and the NG outlet located close to the inner pipe 11 is surrounded by a heat insulating material 17. This prevents the NG temperature from decreasing in the vicinity.

To be more specific, in the open rack type vaporizer having the configuration shown in FIG. 1, if the heat insulating material 17 at the required upper part of the inner pipe 11 is removed, the temperature of NG decreases near the NG outlet pipe 13, as shown in FIG. However, when the insulation material 17 is installed,
As shown in FIG. 6, the temperature of NG is raised to near seawater temperature.

Furthermore, as shown in FIG. 7, instead of the heat insulating material 17 covering the upper outer periphery of the inner tube, an aluminum cover 19 is provided so as to form a required space between the outer periphery of the inner tube and the upper outer periphery of the inner tube. It is possible to adopt a heat insulating means provided around the cover, which is a gas reservoir that retains a part of the NG drawn out into the cover, and exhibits a heat insulating effect equal to or greater than that of the above-mentioned heat insulating material 17. This aluminum cover 19 is provided on the inner tube 11 by welding, but if it is made of stainless steel and screwed, for example, the heat insulation effect will be further improved.

Embodiment 2 A double pipe open rack type vaporizer according to the present invention shown in FIG. 2 has a heat exchange panel having the same structure as that shown in FIG. Located at the bottom of the panel, NG outlet header tank 1
4 are similarly arranged in parallel, and there is no header tank at all near the watering troughs 15 and 16 arranged at the top of the panel.

The supplied LNG rises up the inner pipe 11 from the inlet header tank 12, and is partially vaporized by being heated by NG, which will be described later, before being turned over from the opening upper end of the inner pipe 11 to the upper end of the outer pipe 10. Partially vaporized LNG is stored in outer pipe 10 and inner pipe 1.
While descending through the annular passage between 1 and 1, the NG is further heated and is led out as normal temperature NG to the NG outlet header tank 14 via the NG outlet pipe 13 connected below the outer tube 10. As described above, since the heat exchange panel having the same structure as the structure shown in FIG. 1 is turned upside down, the obtained operation and effect are almost the same.

Embodiment 3 In the double pipe open rack type vaporizer according to the present invention shown in FIGS. 3 and 4, the upper end of the inner pipe 11 protrudes from the closed upper end of the outer pipe 10, and the upper end of the inner pipe 11 is heat-insulated. In the case of Fig. 4, the NG outlet header tank 1
If the position of 4 is as shown in Fig. 3, the LNG inlet header tank 12
It has the same structure as the structure shown in FIG. 1 described above, except that it is set above the LNG inlet header tank 12, whereas it is set at the same height as the LNG inlet header tank 12, and has the same effect.

[0028]

[Effects of the Invention] In the open rack type vaporizer according to the present invention, the heat exchange tube is configured with a double tube, so that NG is supplied from the lower end of the inner tube into the outer tube, ascends inside the tube, and is sent to the outside from the upper end. The pressure loss inside the pipe increases, the gas flow becomes stable, and the heat medium seawater and cryogenic LNG do not directly exchange heat, and the NG inside the annular passage
Because heat is exchanged through the tube, ice buildup on the surface of the outer tube is reduced, and the increased heat transfer area allows the vaporizer to be made more compact, significantly reducing the power consumption of seawater pumps. . In addition, by locating the LNG inlet header tank, where cryogenic LNG is supplied, above the trough, it is possible to prevent seawater from entering the LNG inlet header tank, reducing flow rate hunting and calorific value to each heat exchange tube. Hunting can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing the configuration of a double-tube open rack type vaporizer according to the present invention.

FIG. 2 is a longitudinal cross-sectional view showing the configuration of a double-tube open rack type vaporizer according to the present invention.

FIG. 3 is a longitudinal cross-sectional view showing the structure of another header tank and heat insulating material of the double pipe open rack type vaporizer according to the present invention.

FIG. 4 is a longitudinal cross-sectional view showing the structure of another header tank and heat insulating material of the double pipe open rack type vaporizer according to the present invention.

FIG. 5 is a graph showing the temperatures of seawater, LNG, and NG depending on the height position of the heat exchange panel.

FIG. 6 is a graph showing the temperatures of seawater, LNG, and NG depending on the height position of the heat exchange panel.

FIG. 7 is a longitudinal sectional view showing the structure of another heat insulating means of the double pipe open rack type vaporizer according to the present invention.

FIG. 8 is a perspective explanatory view of a single-tube open rack type vaporizer.

[Explanation of symbols]

10 Outer tube 11 Inner pipe 12 LNG inlet header tank 13 NG outlet pipe 14 NG outlet header tank 15,16 Water trough 17,18 Insulation material 19 Cover

Claims (2)

[Claims] Claim 1: A heat exchange panel is formed by connecting a large number of heat exchange tubes with a double tube structure, and a water spray trough is provided at the top of the panel to enable heating, and the upper end side or lower end of the heat exchange tube is Liquefied gas is introduced into the inner pipe from the inlet header tank provided on the side, and the fluid exiting the inner pipe can be reversed within the closed outer pipe at the other end opposite the inlet header tank.
After reversal, the fluid moving upward or downward through the annular passage between the outer tube and the inner tube can exchange heat with the water sprinkled on the outer surface of the outer tube and the liquefied gas inside the inner tube, and the vaporized gas, which has been vaporized and heated, is transferred to the inlet header tank side. A double pipe open rack type vaporizer characterized by being able to be led out from an outlet header tank connected to an outer pipe. 2. The double pipe open rack type vaporizer according to claim 1, wherein a heat insulating means is provided on the outer periphery of the inner pipe on the inlet header tank side including the vicinity of the outlet to the outlet header tank. .