JP3211190B2 - Low temperature storage tank bottom heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bottom heater provided in a low-temperature storage tank for storing a low-temperature liquefied gas to prevent the base from freezing, and more particularly, to a bottom heater having an outer peripheral insulating layer and a central insulating layer. The present invention relates to a heater arranged at the base of a low-temperature storage tank or at the bottom of the storage tank.

[0002]

2. Description of the Related Art A low-temperature storage tank for storing low-temperature liquefied gas such as LNG, LPG, ammonia, ethylene, etc. is usually provided on a concrete foundation such as pearlite concrete, dry sand or the like so as not to transmit the cold heat of the stored low-temperature liquid to the foundation. A bottom insulation layer made of a heat insulating material is provided, and is installed thereon. However, the heat insulation effect of the bottom cold storage layer is not always sufficient, and the cold heat of the stored low-temperature liquid is transmitted to freeze the moisture in the concrete foundation and the lower ground of the foundation, causing cracks in the foundation and expansion of the frozen ground. There is a risk of lifting the entire storage tank or a part of the storage tank. As a measure against this,
Conventionally, in order to prevent the temperature of the foundation from dropping and keep the foundation at a predetermined temperature or more, heat sources such as electricity and hot water are placed in the bottom insulation layer, in the bottom of the storage tank such as in the concrete outer tank bottom plate, or in the foundation. The heater which used was embedded.

A heater for preventing the basic freezing is disclosed in, for example, Japanese Patent Application Laid-Open No. 58-214097,
No. 14398. JP-A-58-21
In the invention of No. 4097, a plurality of heat pipes are buried and arranged as a heating source in a concrete foundation in which a low-temperature liquid tank is installed, and the heat pipes are buried in parallel with each other or radially from the center. And, the pipe diameter is made thicker or narrower at the center side to heat the entire tank foundation uniformly, preventing the occurrence of local high temperature and low temperature parts due to the heat resistance of the heat pipe, This is to prevent thermal stress from occurring in the concrete foundation. The invention of Japanese Utility Model Application No. Sho 60-14398 relates to a heater system for an underground storage tank. A large number of independent heaters are buried in the entire outer tank of the concrete so as to cover the side plate and the bottom plate, and a power supply is connected to each heater. Thus, even if several independent heaters are disconnected, it is possible to freely control the temperature of an appropriate portion.

In a storage tank for storing a large volume of low-temperature liquefied gas, the load applied to the bottom cold storage layer is almost only a hydraulic load at the center, whereas a large load is applied to the storage tank at the outer periphery. Therefore, a heat insulating material having a pressure resistance corresponding to the load is used, and each is formed, and a bottom cold insulating layer including a central cold insulating layer and an outer peripheral cold insulating layer is formed. In general, the insulation performance of the heat insulating material decreases when the mechanical strength is increased in response to the load. Cooling heat of the storage liquid transmitted to the foundation via the outer part is transmitted more than the central part, the temperature in the concrete foundation becomes uneven, causing thermal stress or partially freezing the outer part of the foundation There was fear. In addition, the temperature of the outer periphery of the storage foundation differs between the southern surface where the amount of solar radiation is high and the northern surface where the amount of solar radiation is low. There was a risk that a difference would occur, causing thermal stress and damaging the foundation.

[0005]

SUMMARY OF THE INVENTION Conventional Japanese Patent Application Laid-Open No. 58-2
In the invention of No. 14097, the portion where the temperature at the center of the tank base is low can be made uniform by increasing the heating amount by enlarging the diameter of the heater or making the space between the heaters dense,
It is difficult to make the temperature uniform at the outer periphery of the tank foundation,
There is a problem that the structure of the heater becomes complicated, and furthermore, it cannot be applied to a low-temperature storage tank provided with a bottom cold-storage layer in which the outer periphery of the storage tank base tends to be low temperature. In addition, 60-1
Even with the invention of No. 4398, not only is it difficult to solve the problem of a low-temperature storage tank with a bottom cold storage layer where the outer periphery of the storage tank base tends to be low temperature, but also the power supply and temperature control equipment of many independent heaters are complicated and large. In addition, there were also problems that maintenance and inspection were difficult.

Accordingly, the present invention solves the problem of non-uniform storage tank base temperature in a low-temperature storage tank provided with a bottom cold storage layer consisting of a central cold storage layer and an outer peripheral cold storage layer, thereby preventing basic frost heaving and further improving efficiency. An economical low temperature storage tank bottom heater is provided.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problem, and has been made to solve the above-mentioned problem by using a bottom heater of a low-temperature storage tank provided with a bottom cooling layer composed of an outer cooling layer and a central cooling layer. An outer peripheral heater disposed on the base or outer tank bottom plate or the bottom cold insulating layer below the part cold insulating layer, and a central part disposed on the base or outer tank bottom plate or the bottom cold insulating layer surrounded by the outer peripheral heater and below the central cold insulating layer The heater and the heater are formed separately from each other. Further, the outer peripheral heater disposed on the base or outer tank bottom plate or the lower cooler layer below the outer peripheral cool layer of the lower cool layer is divided into a plurality of parts, and the divided outer peripheral heaters are formed separately from each other. It was done.

[0008]

The bottom heater of the low-temperature storage tank is separated into an outer peripheral heater and a central heater and arranged separately, and the temperature of the outer peripheral part and the central part of the storage base are controlled separately so that the foundation is not frozen. In particular, the temperature difference generated in the foundation of a low-temperature storage tank provided with a bottom insulation layer composed of an outer periphery insulation layer and a center insulation layer having different heat insulation performances, that is, a temperature difference caused by cooling the outer periphery of the foundation from the center of the foundation. Is to prevent the generation of thermal stress due to a temperature difference and to prevent the frost heap of the outer peripheral portion of the base due to a temperature drop by actively heating an outer peripheral portion heater provided independently on the outer peripheral portion of the base. In addition, the outer peripheral heater is divided into a plurality of separate heaters, and the divided heaters are individually controlled in accordance with a change in temperature at the outer peripheral portion of the foundation due to the orientation, location conditions, storage tank shape, etc. of the outer peripheral portion of the foundation. Make the temperature of the part uniform.

[0009]

Embodiments will be described with reference to the drawings.
FIG. 1 is an explanatory longitudinal sectional view of a double-shell type low-temperature storage tank provided with a bottom heater according to the present invention, in which a part of the double-shell low-temperature storage tank is omitted. FIG. It is a longitudinal section explanatory view which deleted some double shell type low temperature storage tanks which show other examples. Reference numeral 4 denotes an outer tank of a double shell storage tank, which is formed as a sealed body by laying an outer tank bottom plate 6 on a foundation 11. In FIG. 2, the outer tank 4A is formed of concrete, and the foundation 11 and the outer tank bottom slab 6A are formed integrally. Reference numeral 5 denotes an inner tank containing a low-temperature liquid in a double-shell storage tank. The inner tank bottom plate 7 is laid on a bottom cold insulating layer 12 provided on the outer tank bottom plate 6, and is formed as a sealed body. Reference numeral 8 denotes an upper cold insulating layer provided in a range from the side between the outer tank 4 and the inner tank 5 to the roof. 9,
9A is a central cold insulation layer provided at the center of the storage tank between the outer tank bottom plate 6 or the outer tank bottom plate 6A and the inner tank bottom plate 7, and is formed of a heat insulating material such as dry sand, pearlite, foam glass or the like having a low thermal conductivity. . A ring-shaped outer peripheral cold storage layer 1 provided around the lower part of the inner tank 5 side plate on the outer circumference surrounding the central cold storage layers 9 and 9A
0 and 10A are made of a heat insulating material such as pearlite concrete having a high pressure resistance even if the heat conductivity is relatively large because a large load is applied. 3 is to prevent the cold heat of the stored low-temperature liquid transmitted through the bottom cold insulating layer 12 consisting of the central cold insulating layers 9 and 9A and the peripheral cold insulating layers 10 and 10A from lowering the base 11 of the storage tank below a certain temperature so as not to freeze. The bottom heater 3 to be heated is composed of an outer peripheral heater 1 disposed at the outer peripheral portion of the concrete foundation 11 and a central heater 2 disposed at the center of the concrete foundation 11 surrounded by the outer peripheral heater 1. Separate and lay in separate line. The outer peripheral portion heater 1 is provided with a plurality of ring-shaped heaters embedded in a lower foundation 11 of the outer peripheral portion cold insulating layers 10 and 10A, which are slightly inferior to the central cold insulating layers 9 and 9A. The outer peripheral portion heater 1 may be provided with a long path in a wavy line in order to improve the thermal conductivity of the heater. The central heater 2 is uniformly laid in a parallel or radial arrangement in the lower foundation 11 of the bottom central insulating layer 9, 9A having good heat insulation. The positions of the outer peripheral heater 1 and the central heater 2 in the depth direction may be wrapped so as to supply a required amount of heating depending on the heat transfer state and the state of the foundation.

FIG. 3 is an explanatory plan view, partially omitted, showing an example of the arrangement of the bottom heater according to the present invention. The bottom heater 3 is formed of an outer peripheral heater 1 and a central heater 2 that supply a heating source and control the temperature of the heater in separate systems, and the outer peripheral heater 1 is formed in a ring shape on the outer peripheral portion within the base 11 of the storage tank. To place. In addition, the central heater 2 is provided with a base 11 for the storage tank.
As shown in the figure, it is laid evenly in the central part in a parallel or radial arrangement.

FIG. 4 is an explanatory plan view showing a state in which only the outer peripheral heater of the bottom heater according to the present invention is taken out and arranged.
(A), (b), when the outer peripheral heater is divided into two,
(C) shows a case where the outer peripheral heater is divided into three parts, and (d) shows a case where the outer peripheral heater is divided into four parts. The outer peripheral heater 1 of the bottom heater 3 provided on the base 11 of the storage tank is divided into a plurality of heaters 1A, 2 divided heaters 1B, and 4 divided heaters 1C. The supply of the heating source and the temperature control are independent. A series of heaters are provided in a ring shape to control the heating amount corresponding to the distribution of the outer peripheral temperature of the storage tank base 11. In particular,
Corresponds to ambient conditions such as location conditions of storage tanks, orientation, solar radiation, wind direction, etc., and storage tank shape conditions, such as temperature changes caused by different shape conditions depending on the location of accessory equipment such as liquid receiving and dispensing equipment, nozzles, stirrers, etc. Thus, the supply of the heating source of each divided heater and the temperature control thereof are individually performed.

FIG. 5 is a basic sectional explanatory view showing an embodiment in which the bottom heater according to the present invention is installed in a low-temperature storage tank having a bottom insulating layer on the base. Low temperature storage tank 14 shown in this embodiment
Is mounted and supported on the bottom cold storage layer 12 provided on the foundation 11, and transfers the cold heat of the storage tank to be transmitted to the foundation 11,
It is formed so as to be cut off by the bottom cold insulating layer 12 composed of the central cold insulating layer 9B and the outer cold insulating layer 10B. The bottom heater 3 is provided in the base 11 so that the base 11 of the storage tank is not frozen by the cold of the storage tank.
The outer peripheral heater 1 is provided on the ring-shaped outer peripheral portion, and the central heater 2 is separately provided on the central portion surrounded by the outer peripheral heater 1. The supply of the heating source and the temperature control thereof are performed separately. Do with. The outer peripheral heater 1 and the central heater 2 which are arranged separately control the heating separately according to the positional condition of each part, that is, the temperature distribution due to the cold of the storage liquid or the influence of the outside air temperature. And prevent freezing. In each of the above embodiments, the outer peripheral heater 1
And the bottom heater 3 composed of the central heater 2 is laid in the foundation 11. However, if the bottom heater 3 is located at a position where the heat transmitted to the foundation 11 is cut off, the bottom heater 3 may be laid in the concrete outer tank bottom slab 6A.
It may be laid in the bottom insulating layer 12.

[0013]

Since the present invention is configured as described above, it has the following effects. The bottom heater of the storage tank is separated into an outer peripheral heater and a central heater, and the supply and control of the heat source are arranged as separate systems, so that the foundation is prevented from freezing and the central and outer peripheral parts of the foundation are separated. The temperature can be controlled, the temperature of the entire foundation can be made uniform, the thermal stability does not occur, and the safety of the foundation can be ensured. Even if an attempt is made to generate a temperature difference in the foundation through a bottom cold insulation layer consisting of a different outer circumference cold insulation layer and a central cold insulation layer to generate thermal stress, the independently provided outer circumference heater must be actively heated. If the temperature difference disappears and no thermal stress is generated, damage to the outer peripheral foundation due to thermal stress and freezing of the foundation are prevented, and the foundation becomes a safe foundation.

Further, since the supply of the heat source and the control thereof are made independent by dividing the outer peripheral heater into a plurality of parts, each division is made in accordance with the temperature distribution in the outer peripheral part of the storage base according to the location conditions of the storage tank and the shape conditions of the storage tank. Heater can be controlled individually,
The outer peripheral portion of the storage tank base can be easily maintained at a uniform predetermined temperature. Although the present invention is a bottom heater provided in a low-temperature storage tank in which the outer peripheral portion of the foundation has a lower temperature than the central portion, in order to ensure the safety of the foundation, the central portion of the foundation has a lower temperature than the outer peripheral portion. It can also be applied to low temperature storage tanks.

[Brief description of the drawings]

FIG. 1 is an explanatory longitudinal sectional view of a double-shell low-temperature storage tank provided with a bottom heater according to the present invention, with a part thereof being omitted;

FIG. 2 is an explanatory longitudinal sectional view showing another embodiment in which a bottom heater according to the present invention is provided in a bottom plate portion of a concrete outer tank, in which a part of a double-shell low-temperature storage tank is omitted.

FIG. 3 is an explanatory plan view, partially omitted, showing an example of an arrangement state of a bottom heater according to the present invention.

FIG. 4 is an explanatory plan view of a bottom heater according to an embodiment of the present invention, showing a state in which the outer peripheral heater is disposed, in which the outer peripheral heater is divided into two parts (a) and (b). (C) shows the case of dividing into three, and (d) shows the case of dividing into four.

FIG. 5 is an explanatory sectional view of a base showing an embodiment in which the bottom heater according to the present invention is installed in a low-temperature storage tank having a bottom cooling layer on the base.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 outer peripheral heater 1A 2 split heater 1B 3 split heater 1C 4 split heater 2 central heater 3 bottom heater 4, 4A outer tank 5 inner tank 6 outer tank bottom plate 6A outer tank bottom plate 7 inner tank bottom plate 8 upper cold insulation layer 9, 9A , 9B Central insulated layer 10, 10A, 10B Outer peripheral insulated layer 11 Foundation 12 Bottom insulated layer 14 Low temperature storage tank

Claims (2)

(57) [Claims] 1. A bottom heater of a low-temperature storage tank provided with a bottom cooling layer comprising an outer cooling layer and a central cooling layer, wherein the outer heater is disposed on a base below the outer cooling layer, on an outer tank bottom plate, or on the bottom cooling layer. And a central heater disposed on the base or outer tank bottom plate or the bottom cooler layer below the central cooler layer surrounded by the outer peripheral heater, and formed separately in separate series, respectively. Bottom heater. 2. A plurality of peripheral heaters arranged on a foundation or an outer tank bottom plate or a bottom cold insulating layer below an outer peripheral cold insulating layer of the bottom cold insulating layer, and each of the divided outer peripheral heaters is separated into a separate series. The bottom heater of a low-temperature storage tank according to claim 1, wherein the bottom heater is formed.