JP2000283392A - Membrane type low temperature liquefied gas storage tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane-type low-temperature liquefied gas storage tank provided with a compression-resistant heat insulating material which does not use environmental destructive substances and has sufficient physical properties. SOLUTION: In a membrane-type low-temperature liquefied gas storage tank comprising an outer tank 2, a compression-resistant heat insulating material 3 provided on the inner surface thereof, and a membrane inner tank 4 formed of a thin metal plate provided on the inner surface thereof. The compressive heat-insulating material 3 has a compressive strength of 15 N / cm ² or more and a temperature from room temperature (30 ° C.) to a very low temperature (−1).
62 ° C.) and an average thermal conductivity of 0.023 W / m · K
The following is a rigid polyurethane foam in which the blowing agent is hydrofluorocarbon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a membrane tank for storing an ultra-low temperature liquefied gas such as LPG and LNG.

[0002]

2. Description of the Related Art As a low-temperature liquefied gas storage tank, a membrane provided with an outer tank having a rigid structure, a compression-resistant heat insulating material provided on the inner surface thereof, and a membrane inner tank formed of a thin metal plate provided on the inner surface thereof. A low-temperature liquefied gas storage tank is widely used, and a rigid polyurethane foam is generally used as the compression-resistant heat insulating material.

Heretofore, rigid polyurethane foams have been prepared by using an isocyanate compound and a polyol as catalysts and trichloromonofluoromethane (CFC) as a blowing agent in the presence of a foam stabilizer.
-11).

[0004] However, CFC-11 destroys the ozone layer,
It is pointed out that it is a substance that causes global warming,
Hydrochlorofluorocarbons such as CH ₃ CCl ₂ F (CFC-14) may be used as a foaming agent in place of CFC-11.
1b), a production method using CHClF ₂ (CFC-22) or the like has been proposed.
Rather than ozone depletion capacity (ODP) or global warming capacity (G
WP) is small, but it has been determined that its use is prohibited because it is a similar environmental destructive substance.

[0005]

Therefore, there is a need for a method for producing a rigid polyurethane foam that does not use trichloromonofluoromethane or hydrochlorofluorocarbon. The present invention has been made in view of the above-described problems, and provides a membrane-type low-temperature liquefied gas storage tank provided with a compression-resistant heat insulating material that does not use an environmental destructive substance and has sufficient physical characteristics. The main purpose is to

[0006]

SUMMARY OF THE INVENTION The present invention relates to a membrane type low-temperature membrane comprising an outer tank, a compression-resistant heat insulating material provided on the inner surface thereof, and a membrane inner tank made of a thin metal plate provided on the inner surface thereof. In the liquefied gas storage tank, the compression-resistant heat insulating material has a compression strength of 15 N / cm ² or more and a normal temperature (30 ° C.).
To an extremely low temperature (−162 ° C.).
023 W / m · K or less, characterized in that the foaming agent is a rigid polyurethane foam which is a hydrofluorocarbon. Hydrofluorocarbon (HF
C) is a general term for chlorofluorocarbons, which is a combination of hydrogen (H), fluorine (F), and carbon (C), such as CFC-11 and CFC-1.
It does not contain chlorine (Cl) as in 41b. The ozone depletion potential (ODP) is largely due to the action of chlorine in chlorofluorocarbons. In the case of hydrofluorocarbons,
No problem of environmental destruction.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention, wherein 1 is a ground surface, 2 is an outer tank having a rigid structure, 3 is a compression-resistant heat insulating material, and 4 is an inner tank of a membrane. is there. The upper end of the membrane inner tank 4 is connected to a roof 5 installed at the upper end of the outer tank 2, and a heat insulating layer 8 is provided on a hanging roof 7 suspended by a hanging rod 6 from the roof 5. ing.

[0008] The membrane type low temperature liquefied gas storage tank,
The liquid pressure of the low-temperature liquefied gas, the tank pressure, the seismic load, and the like, which are contained in the tank, are supported by the rigid outer tank 2 via a heat insulating material. It is necessary that the heat insulating material 3 of the membrane type low temperature liquefied gas storage tank has high pressure resistance and also has inherent heat insulating properties.

Therefore, the heat insulating material 3 has a compressive strength of 15 N /
cm ² or more, from normal temperature (30 ° C) to extremely low temperature (-162 ° C)
Is a rigid polyurethane foam having an average thermal conductivity of 0.023 W / m · K or less and a blowing agent of hydrofluorocarbon. If the compressive strength is lower than this, the heat insulating material may be deformed or broken by the static pressure and the dynamic pressure applied when the tank is used, which adversely affects the inner membrane tank. Also, when the thermal conductivity is large, the heat input into the tank increases, and the contained liquid gas evaporates more. The vaporized gas is sucked and processed from the tank, but the operation load of the processing apparatus is increased, which is economically unsuitable. The average thermal conductivity is determined by the following equation [1].

[0010]

(Equation 1)

The rigid polyurethane foam of the present invention is obtained, for example, by reacting a polyisocyanate compound or a polyhydroxyl compound in the presence of a catalyst, a foam stabilizer, a foaming agent, a flame retardant and, if necessary, an additive such as water. It can be produced by causing a foaming reaction at the same time as producing a polyurethane resin.

Specifically, the I component mainly composed of a polyisocyanate compound and other components are previously blended, and the R component obtained by mixing is mixed using a urethane foaming machine, poured into a mold having a required shape, foamed and cured. It is manufactured by a batch method in which a block body is manufactured, or a continuous foaming method in which a block is discharged onto a traveling conveyor and foamed and cured on the conveyor.

The urethane foaming machine can use a low-pressure system or a high-pressure system, but in order to achieve the object of the present invention, a high-pressure system capable of obtaining a rigid polyurethane foam having excellent properties such as strength and thermal conductivity is preferable. is there.

The present invention also includes a so-called polycisocyanurate foam in which an isocyanurate ring formed by a trimerization reaction of polyisocyanate belonging to the category of rigid polyurethane foam is introduced into the chemical structure of the resin.

As the polyisocyanate compound used in the present invention, any of those conventionally used for rigid polyurethane foams can be used.
In view of the low-temperature properties of the resulting rigid polyurethane foam, polymeric MDI such as MDI, and prepolymers having an isocyanate group as a terminal group based on polymeric MDI are preferred. The polyhydroxyl compound has active hydrogen as a terminal group and preferably has a functional group number of 2 or more and a hydroxyl group equivalent of 50 to 300. For example,
Polyglycols such as glycerin, trimethylolpropane, pentaerythritol, sugarose, and sorbitol to which polyalkylene oxides such as ethylene oxide and propylene oxide are added; polycarboxylic acids (eg, adipic acid, phthalic anhydride) (Polyester polyols produced by condensation of ethylene glycol, butanediol, diethylene glycol, etc., aromatic polyester polyols utilizing recovered PET, etc. The hydroxyl compound may be used alone or different hydroxyl compounds may be appropriately mixed. In each case, the hydroxyl equivalents of these hydroxyl compounds in the R component are from 100 to 200. Less than these rigid polyurethane foams formed Brittleness is large, not suitable for practical use due also large, the strength is small.

As the catalyst, a tertiary amine such as triethylenediamine or dimethylcyclohexylamine, a triazine, an organotin compound or the like is used in an appropriate combination. In the case of the polyisocyanurate foam, alkylaminophenol, alcoholate, metal salts of organic acids and the like are used as a trimerization catalyst. The foam stabilizer is preferably silicone oil.

The foaming agent is mainly a hydrofluorocarbon, and a mixture (R) containing a polyhydroxy compound is used.
Component) can be pre-mixed, thereby providing R
The viscosity of the component is reduced, the mixing property with the component I is improved, and the physical properties such as the strength and the thermal conductivity of the formed rigid polyurethane foam are improved. As the hydrofluorocarbon, CF
₃ CH ₂ CHF ₂ (HFC-245fa), CF ₃ CH ₂ C
F ₂ CH ₃ (HFC-365mFC), CF ₃ CH ₂ F (H
FC-134a) and the like.

[0018]

EXAMPLES Examples of the raw material blending of the rigid polyurethane foam used in the present invention and physical properties of the obtained rigid polyurethane foam are shown in Table 1 below. In this embodiment,
Using the composition shown in Table 1, a block was manufactured by a continuous foaming method using a high-pressure foaming machine, and after curing for one week, JIS
A The physical properties were measured in accordance with A 9511-1995.

[0019]

[Table 1] Note * 1) Sorbitol-based polyether polyol * 2) Polyester polyol

[0020]

According to the present invention, a membrane type having an outer tank having a rigid structure, a compression-resistant heat insulating material provided on the inner surface thereof, and a membrane inner tank made of a thin metal plate provided on the inner surface side. In the low-temperature liquefied gas storage tank, the compression-resistant heat insulating material has a compression strength of 15 N / cm ² or more and a normal temperature (30
° C) to an ultra-low temperature (-162 ° C), the average thermal conductivity of which is 0.023 W / m · K or less, and the foaming agent is a hydrofluorocarbon rigid polyurethane foam. It is possible to provide a membrane type low temperature liquefied gas storage tank provided with a compression resistant heat insulating material having sufficient physical properties. Also,
INDUSTRIAL APPLICABILITY The present invention has an effect of effectively utilizing resources and effectively contributing to environmental problems since recovered PET can be used.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a membrane type low temperature liquefied gas storage tank showing one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ground surface 2 Outer tank 3 Compression resistant heat insulating material 4 Membrane inner tank 5 Roof 6 Suspension rod 7 Suspended roof 8 Insulation layer

Continued on the front page (72) Inventor Naoji Ishida 1-5-20, Kaigan, Minato-ku, Tokyo Inside Tokyo Gas Co., Ltd. (72) Inventor Shiro Kikuchi 1-70, Ogurocho, Tsurumi-ku, Yokohama-shi, Kanagawa Nichiasu Research Inc. In-house (72) Inventor Kenji Nishino 1-70 Oguro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Nichias Research Institute (72) Inventor Kiyoshi Morita 1-70 Oguro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Nichiasu Research Co., Ltd. In-house (72) Inventor Yoichi Tomosue 1-70 Ogurocho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Nichiasu Corporation Tsurumi Research Laboratory F-term (reference) 3E073 AA01 AB03 CA01 CB02 CD00

Claims (1)

[Claims] 1. A membrane-type low-temperature liquefied gas storage tank comprising an outer tank, a compression-resistant heat insulating material provided on an inner surface thereof, and a membrane inner tank made of a metal sheet provided on an inner surface thereof. Compressive insulation has a compressive strength of 15N /
cm ² or more, from normal temperature (30 ° C) to extremely low temperature (-162 ° C)
A low-temperature liquefied gas storage tank for membranes, characterized in that the average thermal conductivity is 0.023 W / m · K or less and the foaming agent is a rigid polyurethane foam with hydrofluorocarbon.