Device and method for ground freezing

Abstract

A method and device for freezing the ground are disclosed, including a freezing lance which extends along a longitudinal axis and has a pipe mantle that encloses an interior space, wherein the ground surrounding the freezing lance can be cooled by the refrigerant present in a first section of the interior space, a line for supplying the liquid refrigerant in the first section of the interior space, wherein the device has a first end section with a first opening for removing an exhaust gas formed by evaporation of the refrigerant from the interior space, wherein the interior space has a second section for holding the exhaust gas, wherein heat is exchangeable between the exhaust gas and the pipe mantle in the second section, so that the exhaust gas can be heated by heat exchange with the ground adjacent to the freezing lance.

Claims

1. A device for ground freezing, comprising a freezing lance which extends along a longitudinal axis and is designed to be introduced into the earth for the purpose of freezing the ground, wherein the freezing lance includes a pipe mantle that encloses an interior space having a first section for holding a liquid refrigerant, wherein the ground surrounding the freezing lance can be cooled by the refrigerant present in the first section, a line protruding into the interior space for supplying the liquid refrigerant into the first section of the interior space, wherein the device has a first end section, on which a first opening is provided for removing an exhaust gas, formed by evaporation of the refrigerant, from the interior space, and wherein the interior space has a second section adjacent to the first section along the longitudinal axis to hold the exhaust gas, so that the exhaust gas can come into contact with the pipe mantle in the second section, wherein a first device for temperature measurement of the exhaust gas is positioned at a transition area between the first section and the second section and said first device for temperature measurement is used to control or regulate inflow of liquid refrigerant into the interior space.

2. The device for ground freezing according to claim 1, wherein the first device for temperature measurement is displaceable along the longitudinal axis.

3. The device for ground freezing according to claim 1, further comprising a second device for temperature measurement positioned at the first opening, wherein said second device for temperature measurement is designed to measure the temperature of the exhaust gas at the first opening.

4. A method for ground freezing comprising: introducing a freezing lance into the ground, said freezing lance including a pipe mantle which encloses an interior space having a first section and a second section, introducing a liquid refrigerant into said first section of the interior space to at least partially freeze the ground, forming an exhaust gas from evaporation of the refrigerant in said interior space wherein said exhaust gas is held in said second section of the interior space which adjoins the first section of the interior space, wherein the exhaust gas exchanges heat with the pipe mantle in the second section of the freezing lance such that the exhaust gas is heated by exchange of heat with the ground adjacent to the pipe mantle, removing the exhaust gas from the interior space at a first end section of the freezing lance, measuring a first temperature of the exhaust gas at a transition area between the first section and the second section, and, wherein the measured first temperature of the exhaust gas is used to control or regulate inflow of liquid refrigerant into the interior space.

5. The method according to claim 4, wherein the refrigerant is a supercooled liquefied gas.

6. The method according to claim 5, wherein the supercooled liquefied gas is liquid nitrogen.

7. The method according to claim 4, wherein said first end section is provided with a first opening for the removal of the exhaust gas from the interior space, and further comprising measuring a second temperature of the exhaust gas at the first opening.

8. The method according to claim 7, wherein the measured second temperature of the exhaust gas is used control or regulate inflow of the liquid refrigerant into the interior space.

9. The method according to claim 4, wherein a plurality of freezing lances is introduced into the ground, and wherein the first temperature is only measured at some of the freezing lances.

10. The method according to claim 4, wherein the refrigerant is stored at elevated pressure in a refrigerant container, and wherein the refrigerant is introduced into the first section of the interior space from the refrigerant container, and wherein the exhaust gas is withdrawn from the interior space through the first opening by a pressure differential between the interior space and an ambient atmosphere around the freezing lance which is in fluid communication with the first opening.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the invention will be explained in the following description of the FIGURE of embodiments of the invention with reference to a FIGURE. The FIGURE shows:

(2) The FIGURE is a schematic representation of a lengthwise cross section through a

(3) ground freezing device according to the invention.

(4) The FIGURE shows a device 1 according to the invention in a lengthwise cross section relative to a longitudinal axis L, along which device 1 extends. Device 1 includes a freezing lance 10 with a pipe mantle 11, wherein pipe mantle 11 surrounds an interior space 12, particularly in a circumferential direction relative to longitudinal axis L.

(5) The cross section of pipe mantle 11 may be of any shape relative to the cross section of the longitudinal axis L. In particular, the cross section of pipe mantle 11 may be circular relative to the longitudinal axis L. The pipe mantle may have a diameter of 50 to 60 mm, particularly 54 mm, for example.

(6) In particular pipe mantle 11 is made from a material with good heat conducting properties, copper for example, so that good heat exchange is guaranteed between the refrigerant K in interior space 12 and the surrounding ground.

(7) Pipe mantle 11 includes a first end section 2 arranged on the frontal face thereof with respect to the longitudinal axis L and a second end section 3 arranged on the opposite frontal face to the first end section 2.

(8) In the embodiment shown in the FIGURE, the first end section 2 is formed by a freeze head 5, which is joined to the freezing lance 10 by soldering, for example.

(9) When the device 1 is operated correctly, the longitudinal axis L extends vertically, for example, wherein the first end section 2 forms the upper end of freezing lance 10 and in particular is positioned outside of the area of ground that is to be frozen, and wherein the second end section 3 forms the lower end of freezing lance 10 and in particular is positioned in the ground. The second end section 3 is in particular closed, so that no refrigerant K can escape from the interior space 12 through the second end section 3. However, other arrangements are also possible, in which for example the longitudinal axis extends horizontally or at an angle to the vertical.

(10) The interior space 12 includes a first section 13 or freezing zone for holding a liquid refrigerant K, in particular liquid nitrogen, and a second section 14 or warming zone adjacent to the first section 13 along the longitudinal axis L for holding an exhaust gas A formed by evaporation of the refrigerant K.

(11) Particularly when device 1 is used as intended 1, the second section 14 is arranged above the first section 13. Consequently, the lighter exhaust gas A collects above the liquid refrigerant K.

(12) In particular, a phase boundary exists between the liquid refrigerant K and the gas-phase exhaust gas A in a transition area 4 between the first section 13 and the second section 14. Of course, a liquid-gas mixture of refrigerant K may also be present in or close to this phase boundary.

(13) The FIGURE further shows a line 15 for supplying the liquid refrigerant K in the first section 13 of interior space 12. Line 15 is in particular able to be brought into fluid communication with a refrigerant container 19 for storing the refrigerant K. In this context, refrigerant K is stored in refrigerant container 19 under overpressure, for example at a pressure from 2 bar to 20 bar, particularly 6 bar to 16 bar, preferably 8 bar to 12 bar, and introduced into the interior space 12 from the refrigerant container 19 via the line 15. In particular, the fluid connection between the refrigerant container 19 and the line 15 can be closed and/or throttled with a valve 20, so that a refrigerant stream or inflow of refrigerant into the first section 13 may be controlled via valve 20. Line 15 may have a diameter from 6 mm to 28 mm, particularly 12 mm for example. Line 15 may particularly be thermally insulated.

(14) A first device 17 for temperature measurement, for example a temperature measuring probe, is also represented in the FIGURE. Device 17 for temperature measurement, or a temperature sensor disposed on the end thereof is arranged close to 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 immediately after refrigerant K has been evaporated. This makes it possible to obtain relatively precise information about the temperature of the first section 13, so that an inflow of refrigerant from refrigerant container 19 into the first section 13 may be regulated with corresponding precision to correct deviations in the temperature from the setpoint value.

(15) The exhaust gas A formed by the evaporation of refrigerant K flows upwards in the second section 14 of the interior space 12, wherein heat is exchanged between the exhaust gas A and the surrounding ground via pipe mantle 11, so that the exhaust gas A heats up as it rises inside the second section 14.

(16) A first opening 16 is provided in freeze head 5 on the first end section 2, that is to say in particular on the upper end of freezing lance 10, for drawing off the heated exhaust gas A, and a second opening 22 is provided for drawing off the heated exhaust gas A. Interior space 12 in particular is in fluid communication with the ambient atmosphere via first opening 16 and second opening 22, wherein atmospheric pressure exists in the ambient atmosphere. Exhaust gas A flows from the first opening 16 and the second opening 22 into the ambient atmosphere in particular due to the pressure differential between the system consisting of refrigerant container 19 and interior space 12 and the ambient atmosphere.

(17) The first opening 16 shown in the FIGURE is positioned perpendicularly to longitudinal axis L, and the second opening 22 is arranged at the axial end of longitudinal axis L, that is to say on the first end section 2. Of course, it is also possible for only opening to be provided in pipe mantle 11. This may be arranged perpendicularly to the longitudinal axis L or on the axial end.

(18) An optional second device 18 for measuring the temperature of the exhaust gas A may be positioned at the first opening 16. In the embodiment represented in the FIGURE, the first opening 16 in particular serves mainly to measure the temperature of exhaust gas A, whereas most of the exhaust gas A exits the interior space 12 and escapes into the ambient atmosphere through the second opening 22. Alternatively, the second device 18 for temperature measurement may be arranged at the first opening 16 instead of at the second opening 22, or a device for measuring the temperature of the exhaust gas A may be provided both at the first opening 16 and at the second opening 22.

(19) The arrangement of the first opening 16 and the second opening 22 shown in the FIGURE may be configured with a T-piece, for example, wherein a first arm of the T-piece is connected to the pipe mantle 11, and wherein a second arm of the T-piece extending perpendicularly to the first arm of the T-piece forms the first opening 16, and wherein a third arm opposite the first arm and extending parallel to the first arm forms the second opening 22.

(20) Also represented in the FIGURE is a control and/or regulating device 21 which is connected with the first device 17 for temperature measurement, the second device 18 for temperature measurement and valve 20 in such manner that a temperature of exhaust gas A may be measured by the first device 17 for temperature measurement and/or the second device 18 for temperature measurement and transmitted as an actual parameter to the control and/or regulating device 21, wherein the control and/or regulating device 21 is designed to regulate valve 20 so that the inflow of refrigerant K from the refrigerant container 19 into the first section 13 of the interior space 12 of freezing lance 10 is adjusted so that the temperature of exhaust gas A is adapted to a predetermined setpoint value.

(21) This setpoint value is in particular selected such that the temperature of refrigerant K is at a temperature required to freeze the earth in the first section 13 (that is to say it is maintained at the temperature or adjusted to the temperature) when the temperature of the exhaust gas A matches the setpoint value.

(22) For example, if the measured temperature of exhaust gas A is higher than a certain setpoint temperature (which is an indication that a temperature of refrigerant K in the first section 13 is too high), refrigerant K may be fed into the first section 13 via valve 20, intermittently for example, thereby lowering the temperature of refrigerant K in the first section 13.

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

(24) It is also conceivable that the control and/or regulating device 21 controls and/or regulates the inflow of refrigerant K in to the first section 13 not by means of valve 20 but in some other way.

LIST OF REFERENCE SIGNS

(25) 1 Device for ground freezing

(26) 2 First end section

(27) 3 Second end section

(28) 4 Transition area

(29) 5 Freeze head

(30) 10 Freezing lance

(31) 11 Pipe mantle

(32) 12 Interior space

(33) 13 First section or freezing zone

(34) 14 Second section or warming zone

(35) 15 Line

(36) 16 First opening

(37) 17 First temperature measurement device

(38) 18 Second temperature measurement device

(39) 19 Refrigerant container

(40) 20 Valve

(41) 21 Control and/or regulating device

(42) 22 Second opening

(43) A Exhaust gas

(44) K Refrigerant

(45) L Longitudinal axis