JP6572152B2 - Tank vent structure - Google Patents

Description

  The present invention relates to a tank vent structure, and is particularly suitable for a tank that stores evaporated liquid and has a side wall and a roof.

  An example of a tank that stores an evaporating liquid such as petroleum is an outdoor storage tank with a floating lid. This outdoor storage tank with a floating lid is a tank having a structure in which a floating lid is installed inside an outdoor tank with a roof (fixed roof). In the case of only the fixed roof, the highly volatile liquid volatilizes in the space between the liquid surface and the fixed roof, and this volatile component is lost in the long term. An outdoor storage tank with a floating lid is provided with a floating lid in order to suppress this volatilization loss. In such a tank, the floating lid moves up and down to suppress the volatile matter, but when the floating lid moves up and down, the vapor of the stored liquid moves above the floating lid, that is, below the roof. May accumulate. As a facility for effectively discharging the liquid vapor outdoors, for example, as described in Patent Document 1 below, a vent is provided in the roof. For example, the vent is formed so that a vent hole is formed in the vicinity of the tank side wall in the roof, and the upper side of the vent hole is covered with a cover that opens on the tank side wall side.

Japanese Utility Model Publication No. 60-193093

The vents near the side walls of the tank roof effectively take outside air and manage the concentration of steam inside the tank below the specified limit. The environmental load tends to increase due to the emission.
The present invention has been made paying attention to the above-described problems, and an object of the present invention is to provide a tank vent structure that can reduce the environmental load.

In order to solve the above problems, according to one aspect of the present invention, there is provided a vent structure for a tank that stores a liquid to be evaporated and has a side wall and a roof, and has a vent hole formed in the vicinity of the side wall of the roof. A cover that covers at least the upper side of the vent hole and opens at least on the side wall, and a wind rising along the side wall that protrudes from the lower side of the opening on the side wall side of the cover in a direction intersecting the side wall. There is provided a tank vent structure including a shielding plate that suppresses inflow from the opening into the vent hole .

  In the tank vent structure according to the present invention, it is possible to suppress the wind rising along the side wall from flowing into the vent hole from the opening on the side wall side of the cover, so that it is discharged from the other vent hole to the environment through the cover. It is possible to reduce the steam in the tank, which can reduce the environmental load.

It is a longitudinal cross-sectional view which shows an example of the outdoor storage tank with a floating lid to which the vent structure for tanks of this invention was applied. It is a perspective view which shows one Embodiment of the vent structure provided in the tank of FIG. It is a perspective view which shows other embodiment of the vent structure for tanks. It is a top view of the vent provided in the tank of FIG. It is a perspective view which shows the conventional vent hole structure for tanks. It is a perspective view which shows the comparative example of the vent structure for tanks.

  The following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention is the material, shape, structure, arrangement, etc. of components. Is not specified as follows. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.

  Hereinafter, embodiments of a tank vent structure according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view showing an example of an outdoor storage tank 1 with a floating lid to which the tank vent structure of this embodiment is applied. In this outdoor storage tank 1 with a floating lid, the outer shape of the tank is formed by a cylindrical side wall 2 and a conical roof (fixed roof) 3 having a low height. Inside the tank 1, a disc-shaped floating lid 4 that divides the inside of the tank 1 into upper and lower sides is installed. A float 5 that floats on the upper surface of the liquid stored in the tank is provided on the outer periphery of the float 4, and the float 4 and the sidewall 2 are liquid-tightly shielded between the side wall 2 and the float 5 of the tank 1. A seal 6 is provided. In the outdoor storage tank 1 with a lid, the evaporating liquid L, particularly the volatile liquid L, is stored below the floating lid 4, and the floating lid 4 floats on the upper surface of the liquid L. Thereby, volatilization of the liquid L is suppressed and loss is suppressed. The top of the roof 3 of the outdoor storage tank 1 with a floating lid is composed of a 200A steel pipe having a pipe outer diameter of 204.7 mm and a wall thickness of 5.8 mm, and a suction pipe 7 for sucking volatile vapor inside the tank. In the vicinity of the top, a nitrogen pipe 8 for filling an inert gas made of a 15A steel pipe having a pipe outer diameter of 21.7 mm and a wall thickness of 2.8 mm is installed.

  The roof 3 of the outdoor storage tank 1 with a floating lid is provided with a vent structure 9 for managing the concentration of volatile vapor inside the tank below a specified limit. In this embodiment, a total of seven vent structures 9 are arranged on the roof 3 of the tank 1 that is circular in plan view. As shown in FIG. 2, the vent structure 9 of this embodiment covers at least the upper side of the vent hole 10 formed in the vicinity of the side wall 2 of the tank 1 in the roof 3 of the tank 1 and at least the tank. 1 includes a cover 11 that opens on the side wall 2 side, and a shielding plate 13 that protrudes in a direction intersecting the side wall 2 of the tank 1 from below the tank side wall opening 12 of the cover 11. Specifically, the vent hole 10 is a circular hole that is near the side wall 2 of the tank 1 and penetrates the roof 3 of the tank 1. The cover 11 is a substantially hemispherical hood member made of, for example, a metal plate that opens only on the tank side wall 2 side, and the lower end edge of the hood member is in close contact with the roof 3 of the tank 1 except for the side wall side opening 12. . The cover 11 prevents intrusion such as rain and snow which falls directly into the vent hole 10 or enters the vent hole 10 through the roof 3 of the conical tank 1. The tank sidewall opening 12 of the cover 11 has a lower end that is substantially the same position as the tank sidewall 2, and an upper end that opens obliquely so as to be slightly outside the tank sidewall 2. Further, the vent structure 9 including only the vent hole 10 and the cover 11 may be existing in the past.

  The shielding plate 13 of this embodiment is formed of, for example, a metal flat plate, and protrudes in a horizontal direction from directly below the tank side wall side opening 12 of the cover 11 so that both surfaces of the flat plate face up and down. As described above, the tank side wall side opening 12 of the cover 11 is obliquely opened so that the upper end portion is located outside the tank side wall 2. Rises along the tank side wall 2, and the rising wind flows into the vent hole 10 through the opening 12 of the cover 11. When wind (outside air) flows from the vent hole 10, the volatile vapor (gas) inside the tank flows out from the other vent hole 10, and the environmental load increases. The shielding plate 13 of this embodiment suppresses the wind rising along the tank side wall 2 and suppresses the inflow from the cover 11 into the vent hole 10. Therefore, the shielding plate 13 of this embodiment has a width equal to or larger than the width of the tank side wall opening 12 of the cover 11 as viewed from the tank side wall vertical direction. As for the shielding board 13 of this embodiment, the whole shielding board 13 comprises the rising wind shielding part 14. FIG. In addition, the protrusion direction of the shielding board 13 in this embodiment does not necessarily need to be a horizontal direction, and may be slightly inclined up and down.

  FIG. 3 is a perspective view showing another embodiment of the shielding plate 13. The shielding plate 13 of this embodiment is made of, for example, a metal flat plate, like the shielding plate 13 of FIG. 2, and once protrudes in the direction intersecting the tank side wall 2, specifically in the horizontal direction, the protruding tip The cross wind shielding portion 15 is formed by bending the portion upward (obliquely upward). The wind (outside air) flowing into the ventilation hole 10 through the cover 11 is not only the wind rising along the tank side wall 2 but also the wind toward the side wall side opening 12 of the cover 11, as can be seen from the shape of the cover 11, In other words, there is a crosswind. Since the shielding plate 13 of this embodiment has not only the rising wind shielding portion 14 protruding in the horizontal direction but also the side wind shielding portion 15 formed by bending upward, not only the wind rising along the tank side wall 2 Further, it is possible to suppress the cross wind directed toward the side wall side opening 12 of the cover 11 from flowing into the vent hole 10. Therefore, the portion of the shielding plate 13 that is bent upward, that is, the cross wind shielding portion 15 has a shape and a size that cover the tank sidewall opening 12 of the cover 11 as viewed from the tank sidewall vertical direction.

  Next, with respect to the effects of the shielding plate 13 in FIG. 2 (hereinafter also referred to as the shielding plate of Example 1) and the shielding plate 13 in FIG. 3 (hereinafter also referred to as the shielding plate of Example 2), general-purpose fluid software is used. Then, fluid analysis in the tank 1 and in the vicinity of the discharge port structure 9 was performed by a computer. The type of analysis was a three-dimensional steady turbulent flow analysis of an incompressible rectifier pair, and was studied with a two-component system of benzene and air contained in the volatile vapor in the tank 1. FIG. 4 shows an arrangement layout of a total of seven vent structures 9 arranged on the roof 3 of the above-described outdoor storage tank 1 with a floating lid. The structure of the tank 1 is assumed to have a diameter of φ20750 mm and a height of 9140 mm, and the vent hole 10 is φ530 mm. Ventilation structure 9 is installed at 30 °, 80 °, 130 °, 180 °, 230 °, 280 °, and 340 ° in the clockwise direction on the outer periphery of tank roof 3 with the north facing at the tank installation location being 0 °. Each vent structure number was given a D to G in the order of B at 30 °, C at 80 °, and A at 340 °.

As for the wind, the northward direction was 0 °, and the southwestern wind from the direction of 225 ° was blown at a wind speed of 2.0 m / s. From the nitrogen pipe 8 provided at the top of the tank roof 3, a constant amount of nitrogen was continuously sealed at 0.409 m / s, and from the suction pipe 7 provided around the top of the tank roof 3 -3 mmH ₂ O (water column millimeter) Then, the gas (volatile vapor) in the tank 1 was sucked and burned at the suction destination. In principle, the gas in the tank does not flow out from each vent structure 9 by this nitrogen filling and gas suction. In order to reproduce the wet state of the inner wall of the tank due to the vertical movement of the floating lid 4, the benzene concentration on the inner wall of the tank was set to 30 wt% which is a saturated concentration. In order to clarify the effect of reducing the amount of benzene outflow by the shielding plate 13 of Example 1 and the shielding plate 13 of Example 2, as shown in FIG. 5, a vent structure 9 without a shielding plate was used as a conventional example. Further, a vent structure 9 provided with a shielding plate 13 as shown in FIG. The shielding plate 13 of this comparative example is attached to a tank side wall side opening 12 of the cover 11 in close contact with, for example, a metal flat plate bent into an upward convex mountain shape, and the tank side wall side opening 12 of the cover 11 is attached to the shielding plate. 13 is opened inside. Incidentally, the shielding plate 13 of this comparative example was set mainly for the purpose of suppressing the cross wind blown into the tank side wall side opening 12 of the cover 11. Accordingly, the bottom of the shielding plate 13 of the comparative example that is bent into an upwardly convex mountain shape opens to the upper end of the tank side wall 2. Table 1 shows the analysis results.

  The total outflow amount in the table is the total amount of gas (air and benzene) flowing out from each vent structure 9, the benzene concentration is the benzene concentration in the outflow gas from each vent structure 9, and the benzene outflow amount is This is the flow rate of benzene flowing out from each vent structure 9, and benzene outflow amount = total outflow amount × benzene concentration. In addition, “−” in the table means that no outflow of gas from each vent structure 9 is observed, and on the contrary, wind (outside air) flows into the vent structure 9. Conceivable. In the conventional example without a shielding plate, the total amount of benzene outflow was 392.9 kg / h. In the case of the vent structure 9 provided with the shielding plate 13 of Example 1, the total amount of benzene efflux was 176.4 kg / h, which was 55.1% lower than the conventional example. . Further, in the case of the vent structure 9 provided with the shielding plate 13 of Example 2, the total amount of benzene outflow is 125.6 kg / h, which is a 68.0% benzene outflow reduction effect compared to the conventional example. there were. On the other hand, in the case of the vent structure 9 provided with the shielding plate 13 of the comparative example, the total amount of benzene outflow is 943.3 kg / h, which is -140.1% reduction in benzene outflow compared to the conventional example. That is, benzene outflow increased by 140.1%.

  Therefore, in the vent structure 9 including the combination of the cover 11 having the tank side wall side opening 12 and the vent hole 10, the wind rising up the tank side wall 2 can be suppressed from the other vent structure 9. It is most important to reduce gas outflow, and next to this, it is important to suppress the cross wind blowing toward the tank side wall opening 12 of the cover 11. Therefore, as in the shielding plate 13 of the first embodiment, even the shielding plate 13 having only the rising wind shielding portion 14 made of a flat plate protruding in the direction intersecting the tank side wall 2, specifically the horizontal direction, A significant reduction in the amount of outflow of gas in the tank can be obtained. Further, like the shielding plate 13 of the second embodiment, the rising wind shielding portion 14 projecting in the direction intersecting the tank side wall 2, specifically the horizontal direction, and the side wind shielding with the projecting tip portion bent upward. If it is the shielding board 13 provided with the part 15, the outflow amount reduction effect of the gas in a tank will be acquired further. On the contrary, even if the inflow of the cross wind into the vent hole 10 can be suppressed, the outflow amount of the gas in the tank is rather in the comparative shielding plate 13 that cannot suppress the inflow of the updraft along the tank side wall 2 into the vent hole 10. Reduction effect cannot be obtained.

  Thus, in the vent structure 9 of this embodiment, in the tank 1 that stores the liquid to be evaporated and has the side wall 2 and the roof 3, the vent hole 10 is formed near the side wall 2 in the roof 3, and the tank A cover 11 that opens on the side wall 2 covers the upper side of the vent hole 10, and a shielding plate 13 that protrudes in a direction intersecting the tank side wall 2 is projected from below the tank side wall side opening 12 of the cover 11. Thereby, it is possible to suppress the wind rising along the tank side wall 2 from flowing into the vent hole 10 through the tank side wall side opening 12 of the cover 11, and thereby the inside of the tank from the other vent hole 10. Since the outflow amount of gas can be reduced, the environmental load can be reduced.

In addition, by setting the width of the shielding plate 13 to be equal to or larger than the width of the tank side wall side opening 12 of the cover 11 as viewed from the tank side wall vertical direction, the wind rising along the tank side wall 2 is opened on the tank side wall side of the cover 11. It is possible to further suppress the flow into the vent hole 10 through the portion 12 and to further reduce the environmental load.
Further, by projecting the shielding plate 13 in a direction intersecting the tank side wall 2 and bending the protruding tip portion upward, not only the wind rising along the tank side wall 2 but also the tank side wall side opening 12 of the cover 11. It can suppress that the cross wind which blows in flows into vent hole 10, and it becomes possible to further reduce environmental load.

Further, by covering the tank side wall side opening 12 of the cover 11 viewed from the vertical direction of the tank side wall with the portion of the shielding plate 13 that is bent upward, a cross wind blowing into the tank side wall side opening 12 of the cover 11 is generated. It is possible to further suppress the inflow into the vent hole 10 and further reduce the environmental load.
In addition, the shape of the ventilation hole 10, the shape of the cover 11, and the shape of the shielding board 13 are not limited to embodiment. Moreover, the number of installation of the vent structure 9 on the tank roof 3 is not limited to the embodiment.

  It goes without saying that the present invention includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention-specific matters described in the appropriate claims from the above description.

DESCRIPTION OF SYMBOLS 1 Tank 2 Side wall 3 Roof 4 Floating lid 5 Float 6 Seal 7 Suction piping 8 Nitrogen piping 9 Vent structure 10 Vent hole 11 Cover 12 Opening part 13 Shielding plate 14 Ascending wind shielding part 15 Side wind shielding part

Claims (4)

A tank vent structure for storing evaporating liquid and having side walls and a roof,
A vent hole formed near the side wall of the roof;
A cover that covers at least the upper side of the vent hole and opens at least the side wall;
A wind rising along the side wall that protrudes in a direction intersecting the side wall from the lower side of the side wall side opening of the cover flows into the vent hole from the side wall side opening of the cover. A shielding plate to suppress ,
Ventilation structure for tank with   2. The tank vent structure according to claim 1, wherein the shielding plate has a width equal to or larger than a width of the opening on the side wall side of the cover as viewed from a direction perpendicular to the side wall.   3. The tank vent structure according to claim 1, wherein the shielding plate protrudes in a direction intersecting with the side wall, and a protruding tip end portion thereof is bent upward.   4. The tank vent structure according to claim 3, wherein a portion of the shielding plate that is bent upward covers the side wall side opening of the cover as viewed from the side wall vertical direction. 5.

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