KR20210076549A - Grouting material for underground heat exchangers and method of construction using the same - Google Patents

Abstract

The present invention relates to a grouting material for an underground heat exchanger and a grouting method using the same. The grouting material for the underground heat exchanger includes: 30 to 55 wt% of silica sand; 20 to 30 wt% of bentonite; 5 to 10 wt% of a hydraulic binder; 10 to 15 wt% of water; and 5 to 10 wt% of copper smelting slag, wherein the copper smelting slag is to have a particle size distribution of 0.5 to 4.0 mm by a slag generated during copper smelting by water granulating with high pressure water. According to this configuration, it is possible to provide the grouting material for the underground heat exchanger having high thermal conductivity, workability, and low shrinkage, and the grouting method using the same.

Description

Grouting material for underground heat exchangers and method of construction using the same

The present invention relates to a grouting material for an underground heat exchanger and a grouting method using the same.

Recently, as carbon dioxide emissions from fossil energy have been highlighted as a global environmental problem, various methods are being developed to reduce the use of fossil energy. As part of this, a heat exchanger is installed underground and a heating medium is circulated in the underground heat exchanger to heat and cool buildings. A geothermal heat pump system, which receives the energy required for heating from geothermal heat, has been developed and used.

Since the underground temperature is maintained at a temperature of 17 to 18°C throughout the year, it is possible to secure the amount of heat according to the temperature difference by pumping the groundwater and using heat using a heat pump. Since groundwater or heating medium heated or cooled by heat exchange in the heat pump flows into the ground and exchanges heat with the ground again, this cycle can be continuously maintained. A facility using this principle is a geothermal heat pump system.

In the geothermal heat pump system, the geothermal heat exchanger located in the ground is largely divided into a closed type and an open type.

The open type geothermal well is similar to a general underground water well, but the groundwater pumped by the deep well pump is exchanged with a heat pump installed on the ground, and then the heat-exchanged groundwater is returned to the inside of the geothermal well to exchange underground heat.

In the sealed type, a polyethylene pipe (PE pipe) for heat exchange is installed in a U-shape inside a geothermal hole drilled into the ground, and the heating medium is circulated inside the tube to exchange heat between the heating medium and the ground.

When installing a sealed type underground heat exchanger, insert a PE pipe (hereinafter referred to as a heat exchange pipe) bent in a U-shape into a hole drilled to a depth of approximately 150 to 200 m underground, and then fill the hole with grout material. The filling of the grout material is performed by inserting the tremie tube into the drilling hole and flowing the grout material into the tremie tube.

The grout material fills the space between the underground heat exchanger and the ground or rock to promote heat transfer to and from the ground, and plays a role in preventing the penetration of surface water in the bore hole and contamination of the ground water. Therefore, the conditions that the grout material must have are high thermal conductivity, low water permeability, and secure workability that facilitates work.

Although bentonite and cement are common grout materials, most of the bentonite is currently used in Korea.

As most of bentonite is imported, the burden of material cost is high, and although it has excellent advantages in terms of underground environmental protection, it has a problem of low thermal conductivity.

Cement has higher thermal conductivity than bentonite, high adhesion and low permeability coefficient.

In general, the grout material is used by mixing bentonite with other sand, etc. However, research on bentonite grout material exclusively for underground heat exchangers in Korea is insufficient.

In addition, if the grout material shrinks a lot as it dries, material separation occurs and a thermal discontinuity is formed, thereby reducing the geothermal heat exchange efficiency.

Therefore, there is a need for a bentonite-based grout material having high thermal conductivity, workability, and low shrinkage.

Korean Patent Application No. 10-2003-0099010

The present invention was invented in view of the above circumstances, and an object of the present invention is to provide a grouting material for an underground heat exchanger having high thermal conductivity, workability, and low shrinkage, and a grouting method using the same.

The grouting material for a geothermal heat exchanger according to the present invention for realizing the object as described above is 30 to 55 wt% of silica sand; 20-30% by weight of bentonite; 5-10 wt% of a hydraulic binder; 10-15% by weight of water; includes

In addition, 5 to 10% by weight of copper smelting slag; Further comprising, the copper smelting slag is to have a particle size distribution of 0.5 ~ 4.0mm by the slag generated during copper smelting by water crushing with high pressure water.

In addition, the hydraulic binder is composed of silicate 3 lime (3CaO·SiO ₂ ), silicate 2 lime (2CaO·SiO ₂ ) and aluminate lime (3CaO·Al ₂ O ₃ ), the silicate 3 lime, the silicate 2 lime and the lime aluminate is mixed in a ratio of 1:1:0.7.

A grouting method for a geothermal heat exchanger according to another embodiment of the present invention comprises: a hole drilling step of drilling a hole of a predetermined diameter to a predetermined depth in the ground using a drilling facility; a heat exchange pipe installation step of installing a heat exchange pipe in the hole; a grout material filling step of inserting a tremie tube into the hole in which the heat exchange pipe is installed to fill the grout material; a finishing step of finishing or forming a surface layer so that external contaminants do not flow into the upper portion of the hole filled with the grout material; Including, wherein the grout material, 30 to 55% by weight of silica sand; 20-30% by weight of bentonite; 5-10 wt% of a hydraulic binder; 5-10% by weight of copper smelting slag; 10-15% by weight of water; includes

According to the present invention, it is possible to provide a grouting material for an underground heat exchanger having high thermal conductivity, workability, and low shrinkage, and a grouting method using the same.

1 is a process flow chart of a grouting method for a geothermal heat exchanger of the present invention.
Figure 2 is a view showing the grout material filling step in the present invention.

Hereinafter, the configuration and operation of the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Here, in adding reference numerals to the components of each drawing, it should be noted that only the same components are marked with the same reference numerals as much as possible even though they are displayed on different drawings.

1 is a process flow chart of a grouting method for a geothermal heat exchanger of the present invention. Figure 2 is a view showing the grout material filling step in the present invention.

The grouting method for an underground heat exchanger according to the present invention includes a hole drilling step (S100), a heat exchange pipe installation step (S200), a grout material filling step (S300) and a finishing step (S400).

The hole drilling step (S100) is a step of drilling a hole 10 having a depth of 150 to 200 m in the ground using a drilling equipment (eg, a drilling machine, etc.).

Here, when the hole 10 is drilled using a perforator, the topsoil layer is dug to a predetermined depth to make a hole, and a casing of a predetermined length is inserted into the hole. And when the depth of the hole 10 is deepened by continuing the drilling operation, the operation proceeds while extending the length by connecting another rod to the upper end of the rod on which the bit is installed. At this time, the casing functions to support the soil from entering the hole or collapsing during the drilling operation.

The heat exchange pipe installation step ( S200 ) is a step of inserting the heat exchange pipe 20 bent in a U-shape into the hole 10 drilled in the ground. The heat exchange pipe 20 may be composed of a pipe made of PE material.

The diameter of the heat exchange pipe 20 is approximately 50 mm, and the interval between the bent pipes is formed in a U-shape such that the interval is 50 mm. The spacer 21 is installed in the heat exchange pipe 20 at a predetermined interval so that the interval between the pipes bent in a U-shape is maintained.

In the grout material filling step (S300), after the heat exchange pipe 20 is inserted into the perforated hole 10 and installed, the space between the hole 10 and the heat exchange pipe 20 is filled to replace the underground heat with the heat exchange pipe 20. It is a step of filling the grout material 30 that maintains the shape of the hole for a long time while easily delivering it to the

The grout material 30 prevents groundwater from being contaminated when the heat exchange pipe is damaged and the internal heating medium leaks, and prevents groundwater from leaking to the surface along the perforated hole 10 and the heat exchange pipe 20 function as well.

When the grout material 30 is filled into the perforated hole 10, a tremi tube of a predetermined length is inserted into the perforated hole, and then the supply pump is operated to supply the grout material 30 stored in the storage tank to the tremie tube, thereby perforating The hole 10 is filled by filling it up to a predetermined height from the bottom to the top.

Then, after a predetermined time, as the grout material 30 is subsided, the height filled with the grout material 30 is lowered as a whole, and then the grout material 30 is filled again by the lowered height. The refilling of the grout material 30 is repeated several times according to the amount of settlement of the grout material 30 as described above.

The closing step (S400) is a step of finishing by removing the tremie tube when the filling of the grout material 30 is completed, and then removing the casing installed previously.

At this time, the casing may not be removed if necessary. And the upper part of the perforated hole 10 may be finished in an open state or may be finished by covering the upper part of the hole 10 with a lid or the like, or may be finished by completely filling the hole 10 with soil.

In the present invention, the grout material is bentonite 20-30 wt%, silica sand 30-55 wt%, hydraulic binder 5-10 wt%, copper smelting slag 5-10 wt%, admixture, water reducing agent, thickener, defoaming agent and 10-15 wt% % of water is mixed.

Bentonite is a kind of clay that has strong swelling properties and is gelled by absorbing and expanding water. Since pure bentonite has a lower thermal conductivity than ground or rock, when used alone, it has a disadvantage in that it cannot obtain good thermal efficiency enough to be used in an underground heat exchange system.

Here, bentonite may be divided into Na-based bentonite and Ca-based bentonite, and bentonite produced in nature is mainly in the form of Ca-based bentonite. Since Na-based bentonite has superior viscosity and swelling degree compared to Ca-based bentonite, it is used in the form of Na-based bentonite by replacing the cation of Ca-based bentonite with Na.

To this end, Ca-based bentonite is pulverized and then _{mixed with Na 2} CO ₃ powder, and then heat-treated at 450 to 900° C. to make Na-based bentonite. Alumina or graphite may be added to the bentonite prior to heat treatment.

As a supplement to bentonite, silica sand with good thermal conductivity is mixed with bentonite.

The hydraulic binder reduces the shrinkage of bentonite and prevents thermal short circuit due to shrinkage.

The hydraulic binder is a tri-lime silicate (3CaO•SiO _{2 ) that induces a quick reaction with water, a dilime silicate (2CaO•SiO 2} ) that contributes to strength development, and a quick reaction with water that can generate heat. It consists of lime aluminate (3CaO·Al ₂ O _{3 ).} Here, 3 lime silicate, 2 lime silicate and lime aluminate are mixed in a ratio of 1:1:0.7.

The hydraulic binder is calcined limestone containing 15-20% of clay powder, _{and reacts a part of quicklime with silicic acid (SiO 2} ) and alumina (Al ₂ O ₃ ) contained in clay limestone to form hydraulic minerals such as silicate 3 lime, silicic acid 2 It is produced by producing lime and lime aluminate, which are hydrated with water, and crushed and classified. These hydraulic binders have the advantage of complementing hardenability and high water resistance.

Silica fume or limestone powder fine powder may be mixed as an admixture in order to improve the curing characteristics and strength characteristics of the hydraulic binder.

Silica fume is an industrial by-product of ultra-fine particles obtained by collecting _{silica (SiO 2} ) contained in waste gas generated when manufacturing silicon, ferrosilicon, silicon alloy, etc. with a dust collector. Silica fume is composed of very fine spherical particles (average particle diameter 0.1 to 0.2㎛). Since these silica fume has very fine particles, it increases strength and reduces permeability according to the pore filling effect.

Fine limestone powder can be obtained by pulverizing limestone, and when fine limestone powder is mixed with bentonite, rheological properties are improved, bleeding is reduced, and heat of hydration is suppressed.

Silica fume and fine limestone powder can be used by mixing 2 to 3% by weight and 3 to 6% by weight, respectively.

Copper smelting slag is used to improve the thermal conductivity of bentonite, and slag generated during copper smelting is added as an aggregate. The copper smelting slag separated from the mat during the copper smelting process is subjected to a process for recovering valuable metals in an electric furnace, and then crushed by high-pressure water to form granules with a uniform particle size of 0.5 to 4.0 mm.

As described above, the process of hand crushing the copper smelting slag is to prevent material separation and non-mixing in the process of mixing the slag with the hydraulic binder.

The high-performance AE water reducing agent can use naphthalene or polycarboxylic acid, and the dispersion performance of the hydraulic binder is excellent and the water sensitivity is excellent, and there is no adverse effect such as delay in setting, excessive air entrainment, and decrease in strength, so it can improve the properties of grouting materials. can

The thickener is cellulose-based, and it can improve the uniformity and watertightness of the grout material quality by increasing the viscosity and water retention of the grout and reducing the loss of the grout or the separation of copper smelting slag, which serves as an aggregate, during construction. Ethyl hydroxyl ethyl cellulose (EHEC) and methyl hydroxyl ethyl cellulose (MHEC) may be used as the thickener.

The antifoaming agent is a material that inhibits the formation of bubbles, and dimethyl polysyloxame may be used.

The high-performance AE water reducing agent, thickener, and antifoaming agent may be used with water in an amount of 0.2 to 0.5 wt%, 0.05 to 0.1 wt%, and 0.1 to 0.25 wt%, respectively.

The grouting material for the underground heat exchanger of the present invention is mixed with a hydraulic binder to reduce the shrinkage of bentonite to prevent thermal short circuit due to shrinkage. In addition, copper smelting slag is used to improve the thermal conductivity of bentonite, and after going through a process for recovering valuable metals, it is crushed by high pressure water, so that material separation occurs in the process of mixing the slag with the hydraulic binder. phenomenon can be prevented.

It is obvious to those of ordinary skill in the art that the present invention is not limited to the above embodiments and can be implemented with various modifications or variations without departing from the technical gist of the present invention. will be.

10: Hall
20: heat exchange pipe
21: spacer
30: grout material

Claims (4)

In the grouting material for the underground heat exchanger,
30-55% by weight of silica sand;
20-30% by weight of bentonite;
5-10 wt% of a hydraulic binder;
10-15% by weight of water;
A grouting material for an underground heat exchanger comprising a. According to claim 1,
5-10% by weight of copper smelting slag;
further comprising,
The copper smelting slag is a grouting material for a geothermal heat exchanger so that the slag generated during copper smelting has a particle size distribution of 0.5 to 4.0 mm by water crushing with high pressure water. According to claim 1,
The hydraulic binder consists of silicate 3 lime (3CaO·SiO ₂ ), silicate 2 lime (2CaO·SiO ₂ ) and aluminate lime (3CaO·Al ₂ O ₃ ),
The grouting material for a geothermal heat exchanger in which the silicate 3 lime, the silicate 2 lime and the aluminate lime are mixed in a ratio of 1:1:0.7. A grouting method for an underground heat exchanger comprising:
A hole drilling step of drilling a hole of a predetermined diameter to a predetermined depth in the ground using a drilling machine;
a heat exchange pipe installation step of installing a heat exchange pipe in the hole;
a grout material filling step of inserting a tremie tube into the hole in which the heat exchange pipe is installed to fill the grout material;
a finishing step of finishing or forming a surface layer so that external contaminants do not flow into the upper portion of the hole filled with the grout material;
including,
The grout material,
30-55% by weight of silica sand;
20-30% by weight of bentonite;
5-10 wt% of a hydraulic binder;
5-10% by weight of copper smelting slag;
10-15% by weight of water;
A grouting method for an underground heat exchanger comprising a.

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