EP3441529B1 - Device and method for the freezing of soil - Google Patents

Description

The invention relates to a device and a method for freezing soil.

So-called ground freezing processes or icing processes are used according to the state of the art to consolidate or seal the building ground. Are known e.g. Processes that use liquid nitrogen or liquefied air as a coolant. Also known is the icing with brine, which in turn is tempered by a refrigeration system. Due to the low temperature of the liquid nitrogen, freezing with liquid nitrogen is much faster than with brine, whereas the running costs (energy costs) for longer freezing times are significantly higher with liquid nitrogen than with brine.

According to the state of the art, devices for freezing soil with so-called freezing lances are introduced into the soil for soil freezing processes, the freezing lances having an outer pipe and two downpipes arranged in an interior, such as from document EP2 690 222 A1 known.

According to the prior art, a refrigerant, e.g. a cryogenic liquefied gas such as liquid nitrogen is introduced into the interior. The liquid refrigerant, which is in a thermally conductive connection with the outer pipe, removes heat from the surroundings, so that the soil surrounding the freezing lance freezes.

The exhaust gas (e.g. gaseous nitrogen) produced in the interior space by evaporation of the refrigerant is conducted to the surface of the earth via the second downpipe using the methods of the prior art.

However, this has the disadvantage of a strong formation of fog on the surface, which in particular can lead to poor visibility, so that the risk of an accident is increased.

In addition, the cold gaseous nitrogen escaping from the second downpipe on the surface of the earth can collect near the ground, which can lead to a risk of suffocation in this area.

It is therefore the object of the present invention to provide an apparatus and a method which is improved with regard to the stated disadvantages of the prior art.

This object is achieved by the device according to claim 1 and the method according to claim 5. Advantageous embodiments of the device are specified in subclaims 2 to 4 and advantageous embodiments of the method are specified in subclaims 6 to 10.

A first aspect of the invention relates to a device for freezing soil comprising a freezing lance extending along a longitudinal axis, which is designed to be introduced into the ground for freezing soil, the freezing lance having a jacket which has an interior space with a first section (also referred to as freezing area) for receiving a liquid refrigerant, wherein the soil surrounding the freezing lance can be cooled by means of the refrigerant located in the first section or heat can be extracted from the soil surrounding the freezing lance by means of the refrigerant located in the first section, so that the soil at least partially freezes, and a line projecting into the interior space for providing the liquid refrigerant in the first section of the interior space, the device having a first end section at which a first opening is formed for withdrawing a refrigerant by evaporation eten exhaust gas is provided from the interior, the interior having a second section (also referred to as the heating area) adjoining the first section along the longitudinal axis for receiving the exhaust gas, so that the exhaust gas in the second section can contact the jacket.

In particular, heat is exchangeable in the second section between the exhaust gas located in the interior or flowing through the interior and the jacket, so that the exhaust gas can be heated through the jacket with the soil adjacent to the freezing lance.

This means in particular that a separate exhaust gas line is omitted compared to the prior art and instead the exhaust gas flow is drawn off at the upper end of the freezing lance, in particular at a freezing head.

This has the advantage that the exhaust gas exiting on the surface is significantly warmer due to the heat exchange with the surrounding soil via the jacket than in comparable devices of the prior art in which the exhaust gas flow is guided through a downpipe, in particular thermally insulated from the jacket becomes. This advantageously reduces the formation of mist and the accumulation of exhaust gas on the surface, which improves safety in the vicinity of the icing point. This is particularly relevant in densely populated areas.

Said first end section can be passed through the freezing lance or its jacket, or through a separate part, e.g. a freezer head.

In particular, the device also has a freezing head connected to the freezing lance at the first end section, the freezing head in particular forming the first end section. The freezing head in particular has the line for providing the liquid refrigerant and / or the first opening for drawing off the exhaust gas. In addition, the freezer head can form at least a part of the second section for receiving the exhaust gas.

The freezer head can e.g. be soldered onto the freezing lance. When the device is operated as intended, the freezer head is in particular outside the ground.

The soil surrounding the freezing lance is advantageously used to heat the exhaust gas. Separate devices for heating the exhaust gas flow can thus be omitted and costs and energy are saved.

The elimination of the separate exhaust pipe also reduces the structural complexity of the device and costs are saved.

In particular, the first end section adjoins the second section and the jacket has a second end section which adjoins the first section.

Said device can, when used as intended, e.g. be arranged such that the longitudinal axis is vertical, the first section being arranged below the second section, and the first end section of the shell being arranged above. In particular, the first end section is arranged outside the soil to be frozen. Alternatively, the device can be oriented in any other direction when used as intended.

The freezing lance can e.g. Have a total length of 20 meters, with the bottom 10 meters forming the first section and the top 10 meters forming the second section. For example, an opening in the conduit for providing the coolant can be positioned at a depth of 19.7 meters, i.e. 0.3 meters above the lower end of the freezing lance.

Alternatively, larger overall lengths of the freezing lance, e.g. 60 meters or more, conceivable.

According to one embodiment, the device for freezing soil has a first device for temperature measurement, in particular a temperature measuring lance, positioned at a transition area between the first section and the second section, which is designed to be at the transition area between the first section and the second section measure the temperature of the exhaust gas.

This means that, for example, a pipe with a temperature sensor is pulled to a depth that can be used to measure a reference temperature in order to be able to regulate or set a certain temperature of the first section required for freezing. As an alternative to a temperature measuring lance, a thermocouple, for example, can be inserted directly into the freezing lance so that direct temperature measurement is possible.

In comparison to devices of the prior art, the temperature of the first section can thus be set more precisely (optimized temperature control at the point of use), in particular when the exhaust gas flow is heated on the way to the earth's surface. This leads to cost savings due to a more precisely determinable consumption of refrigerant.

The first device for temperature measurement can e.g. be positioned at a depth of 10 meters with respect to the surface of the earth if the total length of the freezing lance is 20 meters and the lower 10 meters are used as the first section.

According to a further embodiment, the first device for temperature measurement is displaceable along the longitudinal axis.

In this way, different freezer sections (that is to say in particular heights or depths of the first section and of the second section) can advantageously be set flexibly (for the respective application).

According to a further embodiment, the device for freezing earth has a second device for temperature measurement which is positioned at the first opening and is designed to measure the temperature of the exhaust gas at the first opening.

By measuring the temperature at the first opening, that is to say in particular at the surface of the earth, the exhaust gas temperature can be determined in a simple manner, whereby conclusions can be drawn about the temperature in the first section. Thus, e.g. the flow of refrigerant into the first section can be controlled or regulated in order to achieve or maintain a specific temperature of the first section.

Of course, both a first device for measuring the temperature of the exhaust gas at the transition area between the first section and the second section and a second device for measuring the temperature of the exhaust gas at the first opening can also be provided.

A second aspect of the invention relates to a method for freezing soil by means of a device for freezing soil according to the first aspect of the invention, wherein the freezing lance is at least partially inserted into the ground, and wherein a liquid refrigerant is provided in the first section of the interior of the freezing lance The soil surrounding the freezing lance is cooled by means of the refrigerant located in the first section, so that the soil at least partially freezes, and in a second section adjoining the first section an exhaust gas is formed by evaporation of the refrigerant, the exhaust gas is withdrawn from the interior space at the first end section of the freezing lance, and wherein the exhaust gas exchanges heat with the jacket in the second section, so that the exhaust gas is heated by heat exchange with the soil adjacent to the jacket.

The heat exchange between the exhaust gas and the ground takes place mainly via that section of the shell that surrounds the second section or heating area of the interior.

According to one embodiment, the refrigerant is a cryogenic liquefied gas, in particular liquid nitrogen (N ₂ ).

According to a further embodiment, a first temperature of the exhaust gas is measured at the transition region between the first section and the second section, in particular by means of the first device for temperature measurement.

According to a further embodiment, a second temperature, in particular of the exhaust gas withdrawn from the interior, is measured at the first opening on the first end section of the freezing lance (e.g. at the freezing head), in particular by means of the second device for temperature measurement.

According to a further embodiment, an inflow of the refrigerant into the interior is controlled or regulated by means of the first temperature and / or the second temperature, in particular by means of a control and / or regulating device. The inflow of the refrigerant into the first section can be controlled or regulated, for example, by means of a valve, a flow connection being established by means of the valve can be interrupted and / or throttled between a refrigerant container and the first section, in particular the line.

According to a further embodiment, a plurality of freezing lances are introduced into the ground, the first temperature and / or the second temperature being measured on only some of the freezing lances.

In particular, the plurality of freezing lances are provided in a so-called freezing field, which is formed from a plurality of freezing lances which are intended to freeze a section of the ground. In this case, some of the freezing lances are equipped with a device for temperature measurement, in particular a temperature lance (e.g. 10% of the freezing lances), the other freezing lances are then adapted in particular via setting values on the exhaust gas side (i.e., for example via the target value of the exhaust gas temperature at the first end section of the respective freezing lance) this means that the coolant flow is adjusted accordingly so that a certain temperature prevails in the first section. In this case, use can be made of the fact that, in particular in a coherent freezing body, the temperatures at a certain depth at different freezing lances are comparable.

This advantageously saves costs for further temperature measuring devices.

According to a further embodiment, the refrigerant is stored in a refrigerant container at overpressure, that is to say when the pressure is higher than atmospheric pressure, the refrigerant being introduced from the refrigerant container into the first section of the interior space, and the exhaust gas being caused by a pressure difference between the Interior space and a surrounding area of the freezing lance that is in flow connection with the first opening is withdrawn from the interior space via the first opening.

According to a further embodiment, the refrigerant is stored in the refrigerant container at an absolute pressure of 2 bar to 20 bar, in particular 6 bar to 16 bar, preferably 8 bar to 12 bar.

In this case, atmospheric pressure prevails in particular on the outlet side of the first opening, that is to say the system comprising the refrigerant container and freezing lance or interior of the freezing lance is depressurized on the outlet side of the first opening. The pressure difference between the interior and the environment therefore leads to the exhaust gas flowing or being pressed through the first opening into the environment.

Fig. 1

eine schematische Darstellung einer erfindungsgemäßen Vorrichtung zum Gefrieren von Erdreich im Längsschnitt.

Further features and advantages of the invention are explained in the following description of the figures of exemplary embodiments of the invention with reference to a figure. It shows:

Fig. 1

a schematic representation of a device according to the invention for freezing soil in longitudinal section.

Fig. 1 shows a device 1 according to the invention in longitudinal section with respect to a longitudinal axis L along which the device 1 extends. The device 1 has a freezing lance 10 with a jacket 11, the jacket 11 surrounding an interior space 12, in particular in the circumferential direction with respect to the longitudinal axis L.

The jacket 11 can have any shape in cross section with respect to the longitudinal axis L. In particular, the jacket 11 is circular in cross section with respect to the longitudinal axis L. The jacket can e.g. have a diameter of 50 to 60 mm, in particular 54 mm.

In particular, the jacket 11 is made of a material with good thermal conductivity, e.g. Copper, formed so that a good heat transfer between the refrigerant K located in the interior 12 and the surrounding soil is ensured.

The jacket 11 has a first end section 2 arranged on the end face with respect to the longitudinal axis L and a second end section 3 arranged opposite the first end section 2 on the end face.

The first end section 2 is shown in FIG Fig. 1 The embodiment shown is formed by a freezing head 5 which is connected to the freezing lance 10, for example by soldering. When the device 1 is operated as intended, the longitudinal axis L runs vertically, for example, with the first end section 2 forming the upper end of the freezing lance 10 and in particular being positioned outside the soil to be frozen, and with the second end section 3 forming the lower end of the freezing lance 10 and in particular is positioned in the soil. The second end section 3 is in particular closed, so that no refrigerant K can escape from the interior 12 via the second end section 3. However, other arrangements are also possible in which, for example, the longitudinal axis runs horizontally or obliquely with respect to the vertical.

The interior 12 has a first section 13 or freezing area for receiving a liquid refrigerant K, in particular liquid nitrogen, and a second section 14 or heating area adjoining the first section 13 along the longitudinal axis L for receiving an exhaust gas A formed by the evaporation of the refrigerant K. .

In this case, particularly when the device 1 is used as intended, the second section 14 is arranged above the first section 13. As a result, the lighter exhaust gas A collects above the liquid refrigerant K.

At a transition area 4 between the first section 13 and the second section 14, there is in particular a phase boundary between the liquid refrigerant K and the gaseous exhaust gas A. Of course, a liquid-gas mixture of the refrigerant K can also be present at or near this phase boundary.

Furthermore shows Fig. 1 a line 15 for providing the liquid refrigerant K in the first section 13 of the interior 12. The line 15 can be brought into flow connection in particular with a refrigerant container 19 for storing the refrigerant K. The refrigerant K is stored in the refrigerant container 19 at overpressure, for example at a pressure of 2 bar to 20 bar, in particular 6 bar to 16 bar, preferably 8 bar to 12 bar, and from the refrigerant container 19 via line 15 into the interior 12 initiated. In particular, the flow connection between the refrigerant container 19 and the line 15 can be closed and / or throttled by a valve 20, so that a refrigerant flow or refrigerant inflow into the first section 13 can be controlled via the valve 20. The line 15 can, for example, have a diameter of 6 mm to 28 mm, in particular 12 mm. Furthermore, the line 15 can in particular be thermally insulated.

In Fig. 1 a first device 17 for temperature measurement, for example a temperature measuring lance, is also shown. The device 17 for temperature measurement or a temperature sensor arranged at its end is arranged in the vicinity of the transition area 4 between the first section 13 and the second section 14, so that the temperature of the exhaust gas A can be measured directly after the refrigerant K has evaporated. As a result, relatively precise conclusions can be drawn about the temperature of the first section 13, so that a refrigerant inflow from the refrigerant container 19 into the first section 13 can be precisely regulated in order to correct temperature deviations from the setpoint.

The exhaust gas A formed by the evaporation of the refrigerant K flows upwards in the second section 14 of the interior 12, heat being exchanged between the exhaust gas A via the jacket 11 with the surrounding soil, so that the exhaust gas A is in the second section when it rises 14 heated.

A first opening 16 for drawing off the heated exhaust gas A and a second opening 22 for drawing off the heated exhaust gas A are provided on the freezing head 5 at the first end section 2, ie in particular at the upper end of the freezing lance 10. The interior 12 is in flow communication with an environment in particular via the first opening 16 and the second opening 22, with atmospheric pressure prevailing in the environment. In this case, the exhaust gas A flows into the surroundings from the first opening 16 and the second opening 22, in particular due to the pressure difference between the system comprising the refrigerant container 19 and the interior 12 to the surroundings.

In the Fig. 1 The first opening 16 shown is positioned perpendicular to the longitudinal axis L and the second opening 22 is arranged on the end face with respect to the longitudinal axis L, that is to say on the first end section 2. Of course, only one opening of the jacket 11 can also be provided. This can be arranged perpendicular to the longitudinal axis L or at the end.

An optional second device 18 for measuring the temperature of the exhaust gas A is positioned at the first opening 16. In the in Fig. 1 In the illustrated embodiment, the first opening 16 is mainly used to measure the temperature of the exhaust gas A, while the main portion of the exhaust gas A leaves the interior space 12 through the second opening 22 and in particular exits into the environment. Alternatively, the second device 18 for temperature measurement can be arranged on the second opening 22 instead of the first opening 16, or a respective device for measuring the temperature of the exhaust gas A can be provided both on the first opening 16 and on the second opening 22.

In the Fig. 1 The arrangement shown of the first opening 16 and the second opening 22 can be realized, for example, by a T-piece, wherein a first arm of the T-piece is connected to the jacket 11, and wherein a second arm of the T- Piece forms the first opening 16, and wherein a third arm running parallel to the first arm and opposite the first arm forms the second opening 22.

In the Fig. 1 a control and / or regulating device 21 is also shown, which is connected to the first device 17 for temperature measurement, the second device 18 for temperature measurement and the valve 20 in such a way that a temperature of the exhaust gas A from the first device 17 for temperature measurement and / or the second device 18 for temperature measurement and can be transmitted as an actual variable to the control and / or regulating device 21, wherein the control and / or regulating device 21 is designed to regulate the valve 20 so that the inflow of the refrigerant K from the refrigerant container 19 into the first section 13 of the interior 12 of the freezing lance 10 is set in such a way that the temperature of the exhaust gas A is adapted to a predetermined setpoint value.

This setpoint is selected in particular so that the temperature of the refrigerant K in the first section 13 has a temperature required to freeze the ground (that is, is kept at the temperature or is brought to the temperature) when the temperature of the exhaust gas A reaches the setpoint corresponds.

If, for example, the measured temperature of the exhaust gas A exceeds a certain setpoint temperature (which is an indication that the temperature of the refrigerant K in the first section 13), refrigerant K can be introduced into the first section 13 via the valve 20, for example intermittently, as a result of which the temperature of the refrigerant K in the first section 13 is reduced.

Of course, a corresponding control and / or regulating device 21 can also only receive temperature data from one of the devices 17, 18 for temperature measurement (i.e. either with an exhaust gas temperature measured at the transition area 4 or with an exhaust gas temperature measured at the first opening 16 at the first end section).

It is also conceivable that the control and / or regulating device 21 controls or regulates the inflow of the refrigerant K into the first section 13 not via the valve 20 but in another suitable manner.

List of reference symbols

1 Device for freezing soil 2 First end section 3 Second end section 4th Transition area 5 Freezer head 10 Freezing lance 11 coat 12th inner space 13 First section or freezer area 14th Second section or heating area 15th management 16 First opening 17th First device for temperature measurement 18th Second device for temperature measurement 19th Refrigerant tank 20th Valve 21st Control and / or regulating device 22nd Second opening A. Exhaust gas K Refrigerant L. Longitudinal axis

Claims (11)

1. Device (1) for the freezing of soil, having

   - a freezer lance (10) extending along a longitudinal axis (L) and designed to be introduced into the soil for freezing soil, wherein the freezer lance (10) has a sheath (11) which surrounds an inner space (12) with a first section (13) for receiving a liquid refrigerant (K), wherein the soil surrounding the freezer lance (10) can be cooled by means of the refrigerant (K) present in the first section (13),

   - a line (15), projecting into the inner space (12), for providing the liquid refrigerant (K) in the first section (13) of the inner space (12),

   - wherein the device (1) has a first end section (2) in which a first opening (16) is provided for extracting from the inner space (12) an off-gas (A) formed by evaporation of the refrigerant (K),

   characterized in that
   the inner space (12) has a second section (14), adjacent to the first section (13) along the longitudinal axis (L), for receiving the off-gas (A), so that the off-gas (A) in the second section (14) can contact the sheath (11).
2. Device (1) for the freezing of soil according to claim 1, characterized in that the device (1) has a first apparatus (17) for measuring temperature which is positioned at a transition region (4) between the first section (13) and the second section (14) and is designed to measure the temperature of the off-gas (A) at the transition region (4) between the first section (13) and the second section (14).
3. Device (1) for the freezing of soil according to claim 2, characterized in that the first apparatus (17) for temperature measurement is displaceable along the longitudinal axis (L).
4. Device (1) for the freezing of soil according to one of claims 1 through 3, characterized in that the device (1) has a second apparatus (18) for temperature measurement which is positioned at the first opening (16) and is designed to measure the temperature of the off-gas (A) at the first opening (16).
5. Method for the freezing of soil by means of a device (1) for the freezing of soil according to one of claims 1 through 4, wherein the freezer lance (10) is introduced into soil, and wherein, in the first section (13), a liquid refrigerant (K) is provided, wherein the soil surrounding the freezer lance (10) is cooled by means of the refrigerant (K) present in the first section (13), so that the soil at least partially freezes, and wherein, in a second section (13) adjoining the first section (14), an off-gas (A) is formed by evaporation of the refrigerant (K), wherein the off-gas (A) at the first end section (2) of the freezer lance (10) is removed from the inner space (12), and wherein the off-gas (A) in the second section (14) exchanges heat with the sheath (11), so that the off-gas (A) is heated by heat exchange with the soil adjacent to the sheath (11).
6. Method according to claim 5, wherein the refrigerant (K) is a cryogenic liquefied gas - in particular, liquid nitrogen (N₂).
7. Method according to claim 5 or 6, wherein a first temperature of the off-gas (A) is measured at the transition region (4) between the first section (13) and the second section (14).
8. Method according to one of claims 5 through 7, wherein a second temperature of the off-gas (A) is measured at the first opening (16).
9. Method according to claim 7 or 8, wherein an inflow of the refrigerant (K) into the inner space (12) is controlled or regulated by means of the first temperature and/or the second temperature.
10. Method according to one of claims 5 through 9, wherein a plurality of freezer lances (10) are introduced into the soil, and wherein the first temperature and/or the second temperature is measured at only a part of the freezer lances (10).
11. Method according to one of claims 5 through 10, wherein the refrigerant (K) is stored at elevated pressure in a refrigerant tank (19), and wherein the refrigerant (K) from the refrigerant tank (19) is introduced into the first section (13) of the inner space (12), and wherein the off-gas (A) is removed, via the first opening, (16) from the inner space (12) by a pressure difference between the inner space (12) and an environment, which is in flow connection with the first opening, (16) of the freezer lance (10).

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