JPH0117036B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for constructing a bottom heat insulating layer of a heat insulated storage tank, and more specifically, a heat insulating layer made of expanded perlite, which has high compressive strength and excellent heat insulation properties, is installed between the foundation and the bottom plate of a storage tank. This provides a construction method with good workability.

(Technical background) Many storage tanks that store high-temperature or low-temperature liquids have insulation materials applied not only to the side walls and roofs of the tank, but also to the bottom to prevent thermal energy from flowing out or flowing into the tank. In particular, in storage tanks that store large volumes of liquid at extremely low temperatures, such as LNG (liquefied natural gas) and LPG (liquefied petroleum gas) storage tanks, the structure of the insulation layer at the bottom of the tank is determined from the safety of the storage tank and Construction costs are also an important issue in terms of storage costs.

The tank structure currently most popular for LNG, LPG storage tanks, etc. is a double shell structure, and the bottom part is an outer shell tank and an inner shell tank on a concrete foundation that supports the entire tank, and the space between them is It is best to provide a heat insulating layer, or to provide an annular so-called ring concrete that supports the inner shell tank on the bottom plate of the outer shell tank, and to provide a heat insulating layer in the space surrounded by this ring concrete and the bottom plate of the inner and outer tank. It is common. Most of these storage tanks are installed above ground, but in recent years underground storage tanks have also become popular.

The requirements for the bottom insulation layer of such an insulation storage tank are, of course, that it has excellent insulation properties;
It has the compressive strength to withstand the liquid pressure of the contents of the storage tank, has little loss of strength at high or low temperatures, does not corrode iron plates, and is inexpensive and easy to construct.

Conventionally, the bottom insulation layer of such a heat-insulated storage tank has been constructed by laying several layers of perlite concrete blocks or lightweight concrete blocks formed by hardening expanded perlite with concrete, or by constructing expanded perlite and concrete. It has been constructed using methods such as pouring on site. However, the former method is not economical because the blocks are produced in a factory, and it requires handling relatively heavy blocks, and the gaps between the blocks must be filled with perlite powder, etc. It has the disadvantage of poor workability. In addition, although the latter on-site pouring method is more economical and easier to construct than the former, it requires a long period of time (several weeks) for drying and curing after concrete is poured, and it is difficult to completely dry the concrete. It is difficult to do so, and there remains a concern that the insulation performance will deteriorate and there will be condensation or freezing inside.

Furthermore, in order to streamline on-site pouring, if perlite concrete is pumped using a pump truck, etc., the expanded perlite particles may break and the insulation properties may deteriorate, so currently the concrete is transported to the pouring site by hand. be.

In addition, a common drawback of both methods is that since both are based on concrete, the thermal conductivity of the heat insulating layer is 0.15 Kcal/m. Time. For example, when installing an LNG tank with tens of thousands of kiloliters using pearlite concrete as a heat insulating layer, the thickness of the heat insulating layer will be 40 to 50 cm.

(Objective of the present invention) In providing a heat insulating layer between the foundation and the bottom plate of a heat insulated storage tank, the inventors solved the above-mentioned conventional drawbacks and created a heat insulating layer with excellent heat insulating properties and high compressive strength. The method of the present invention was completed as a result of intensive research to find a construction method with good forming workability.

(Method of the present invention) In the method of the present invention, when providing a heat insulating layer of expanded pearlite between the foundation and the bottom plate,
For every 100 parts by weight, add 3 to 30 parts by weight of a liquid room-temperature curing resin with a viscosity of 2000 centipoise or less to an average particle size of
A method for constructing a heat insulating layer at the bottom of a heat insulating storage tank, characterized in that the surface of expanded pearlite particles of 0.3 to 5 mm is coated in advance, the resulting mixed coating is cast on a foundation, and then the room temperature curing resin is cured. be.

(Expanded pearlite) The expanded pearlite used in the present invention is produced by crushing pearlite, rosinite, obsidian, etc., and then firing it at a temperature of 900 to 1100°C. It is made into a hollow body by foaming. These have an apparent specific gravity of 0.07 to 0.25g/
It is extremely light (cc) and has a thermal conductivity of 0.03 ~
0.05Kcal/m, time. ℃ and has excellent insulation properties, especially obsidian-based ones, which have little adsorbed water, have smooth particle surfaces with almost no pores, and have a so-called honeycomb structure in which primary foam particles gather inside, making it easier to compress particles. It is the most preferable pearlite to be used in the present invention because it has high strength, has a nearly perfect spherical shape, and has high strength when bonded with a curable resin.

In the present invention, it is preferable to use among these expanded pearlites those having an average particle size of 0.3 to 5 mm. When the average particle size is 0.3 mm or less, the apparent density of the heat insulating layer becomes high and the heat insulating properties decrease. Furthermore, if pearlite particles having an average particle size of 5 mm or more are used, the compressive strength of the heat insulating layer may be reduced.

(Room temperature curable resin) In the present invention, the room temperature curable resin to which the expanded pearlite particles are bonded is obtained by curing a liquid monomer or polymer into a three-dimensional crosslinked structure using a curing agent or the like. The surface of the expanded pearlite particles is coated with this curable resin in a liquid state, and the resin is left to stand at room temperature to harden and bond the expanded pearlite particles together.

The room temperature curable resin used in the present invention is not particularly limited, and examples include unsaturated polyester resins, phenol resins, epoxy resins, urea resins, melamine resins, urethane resins, modified liquid polybutadiene, and the like. These are generally cured by a conventional method using a curing agent, and the curing agent is appropriately selected depending on the resin used. For example, formalin is used as a curing agent for phenolic resins, urea resins, melamine resins, etc., organic peroxides are used for unsaturated polyester resins, modified liquid polybutadiene, etc., and amines are used as curing agents for epoxy resins, etc.
Note that it is not necessary to add a curing agent to materials that harden with moisture in the air, such as urethane resins.

Many of these room temperature curable resins are viscous liquids, and even when a curing agent is added, they have a considerable viscosity. When implementing the present invention, if the viscosity is too high, the mixed coating may become uneven, and the fluidity of the expanded pearlite particles during casting may deteriorate, making the casting operation difficult, so a hardening agent is added. It is preferable to use one with a viscosity of 2000 centipoise or less after drying.

Therefore, when using a room temperature curable resin with a relatively high viscosity, it is preferable to add a reactive or non-reactive diluent to bring the viscosity within the above range.

The room temperature curable resin is used in an amount of 3 parts by weight or more, preferably 5 parts by weight or more, based on 100 parts by weight of expanded pearlite. If this amount is less than 3 parts by weight, the bonding force between the expanded pearlite particles will be weak and they will not be able to withstand the liquid pressure in the storage tank. There is no particular restriction on the upper limit of the amount of curable resin used, but even if 30 parts by weight or more is used, no significant improvement in compressive strength can be expected and it is disadvantageous from an economic standpoint.

(Construction method) The timing for constructing the bottom insulation layer of the insulation storage tank of the present invention varies depending on the structure of the storage tank, etc. In a storage tank such as that shown in the vertical sectional view (longitudinal cross-sectional view), it is generally constructed after the foundation concrete 8, the outer shell bottom plate 3, and the ring concrete 6 are constructed.

In the present invention, first, expanded pearlite particles are uniformly mixed and coated with a liquid hardening resin near the construction site. Expanded pearlite particles may be destroyed. Additionally, in general, when a mixer with rotary blades is used, when the mixing operation is interrupted, the hardening resin adhering to the mixer wall or rotor hardens, interfering with subsequent mixing operations. There is the inconvenience of having to wash it with an organic solvent or the like.

Regarding this point, the inventors of the present application previously proposed a method of mixing such solid particles and a liquid adhesive substance without contaminating the mixer (Japanese Patent Application No. 107164/1982); This method can be used very effectively in the invention.

That is, in this method, expanded perlite and a cold-curing resin are placed in a plastic bag, for example, and mixed and coated using a mixer that moves the entire container or a part of the container. Types of mixers include rocking mixers and container rotating mixers.

When the above-mentioned oscillating mixer is used in the present invention, the expanded perlite particles and a room-temperature curing resin to which a curing agent has been added as necessary are placed in a bag made of polyethylene or the like, and then transferred to the oscillating mixer. Load into a mixing container and mix. This type of mixer mixes the contents by shaking the entire container or the bottom of the container to move the contents up and down.
etc. are known.

In addition, when using the above-mentioned container rotating type mixer, the expanded perlite particles and room temperature curing resin are placed in a bag made of polyethylene, etc., and this is loaded into a container such as a drum with the bag in close contact with the container wall. Swirl the entire container to mix.

The expanded pearlite mixture coating obtained in this way is transported to the casting site by pneumatic transport, belt conveyor, handcart, etc. In this case as well, the mixed coating is placed in the polyethylene bag mentioned above. If the mixture is taken out of the mixer and transported while still in the container, there is no need to worry about the transport equipment being contaminated by the room-temperature curing resin or the like.

In addition, to cast the above-mentioned expanded pearlite particle mixture coating at the construction site, use the same method as the conventional method of pouring pearlite concrete, etc., and pour the mixed coating at the pouring point, and as needed. After densely packing using a vibrator or press plate, the surface is leveled and finished. Thereafter, the resin is left to harden for several hours to one day, depending on the type of room-temperature curable resin, the amount of curing agent, etc., to complete the construction of the bottom heat insulating layer.

After constructing the heat insulating layer as described above, an asbestos board or the like is laid on top of the heat insulating layer, and the bottom plate of the inner shell tank is welded on top of this to finish the bottom of the tank.

(Effects of the present invention) Next, the effects of the present invention will be described.

(1) In the present invention, the thermal conductivity is 0.03~
0.05Kcal/m, hour. Since expanded perlite, which is inherently highly insulating at ℃, is used, the heat insulating layer of the bottom plate has sufficient heat insulating properties.

(2) Since the amount of room-temperature curing resin used as a binder is small (it is sufficient to use 3% by weight or more), there is less deterioration in insulation properties compared to the method using conventional concrete binders (thermal conductivity after curing is is 0.05-0.07 Kcal/m, h.°C).

Therefore, the thickness of the heat insulating layer can be made thinner than the conventional concrete-based heat insulating layer.

(3) Expanded pearlite particles are inorganic foams;
Although it itself has strong compressive strength, by selecting expanded pearlite with an appropriate particle size, it is possible to obtain a heat insulating layer that can withstand the liquid pressure of an extremely large storage tank of tens of thousands of kiloliters.

(4) Room-temperature curing resin can be cured in a few hours, so construction time can be significantly shortened compared to concrete construction methods.

(5) No water is used and there is almost no residual moisture, so there is no need to worry about internal condensation.

(6) It is very easy to coat expanded pearlite by using a room-temperature curing resin with a relatively low viscosity of 2000 centipoise or less, and the particles maintain good fluidity even after coating (the angle of repose is 30 to 45 degrees). This makes pouring work and surface leveling work easy.

(7) The mixed covering has a much lower density than uncured pearlite concrete and is very easy to transport to the pouring site.

(8) When making a mixed coating of expanded perlite particles and room-temperature curing resin, it is possible to put both into a plastic bag, mix them in a mixer, and then transport the bag to the casting site. During the process up to pouring, there is no need to worry about the mixer or transport equipment being contaminated with room-temperature curing resin.

Examples of the method of the invention are described below.

Example: 100 parts by weight of liquid epoxy resin ("EPOMIK VR-130A" manufactured by Mitsui Petrochemical Co., Ltd.) and 40 parts by weight of a curing agent ("EPOMIK VQ-5" manufactured by Mitsui Petrochemicals) were mixed to form a blended resin (room-temperature curable resin). did.

100 parts by weight of expanded pearlite (Fuyolite No. 1 manufactured by Fuyolite Co., Ltd.) with an average particle size of 1 mm was added to a thickness of 30 mm.
The mixture was placed in a micron polyethylene film bag, and the bag was placed in a mixing container of a rocking mixer (Omnimixer OM-10, manufactured by Chiyoda Giken Industries, Ltd.).

Next, while operating the mixer and shaking the contents, 10 parts by weight of the above blended resin was added little by little.
After dropping, the mixing operation was continued for 1 minute to obtain a mixture in which the surfaces of the expanded pearlite particles were coated with the epoxy resin. This mixture has high fluidity and is suitable for use as a heat insulating layer at the bottom of a heat insulating storage tank, and when the contents of the bag were taken out after mixing, no contamination of the mixer was observed.

The thermal conductivity of the block obtained by leaving this mixed coating for a day and night to harden was 0.07 Kcal/m. Time. ℃
The compressive strength was 7 Kg/cm ² , which fully satisfied the strength required for the bottom plate insulation layer of an ultra-large storage tank with a content of tens of thousands of kiloliters.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the method for constructing a bottom heat insulating layer of a heat insulating storage tank according to the present invention. Code, 1...Double wall tank, 2...Outer shell side plate,
2'...Inner shell side plate, 3...Outer shell bottom plate, 3'...Inner shell bottom plate, 4...Insulating material, 5...Asbestos board, 6...
...Ring concrete, 7...Bottom insulation layer of the present invention, 8...Foundation concrete.

Claims (1)

[Claims] 1. When providing a heat insulating layer of expanded pearlite between the foundation and the bottom plate, for 100 parts by weight of expanded pearlite,
The surface of expanded pearlite particles with an average particle size of 0.3 to 5 mm is coated in advance with 3 to 30 parts by weight of a liquid room temperature curing resin with a viscosity of 2000 centipoise or less, and the resulting mixed coating is poured onto a foundation and then cured at room temperature. A method for constructing a bottom insulation layer of a heat insulation storage tank, characterized by curing a plastic resin. 2. The mixed coating is obtained by further loading a bag filled with both expanded perlite particles and room-temperature curable resin into a container, and mixing the two by a mixer that moves the whole or part of the container. A method for constructing a bottom heat insulating layer of a heat insulating storage tank according to claim 1, which is a mixed coating formed.