CN112854192A - Artificial stratum freezing method utilizing low-temperature carbon dioxide circulation refrigeration - Google Patents
Artificial stratum freezing method utilizing low-temperature carbon dioxide circulation refrigeration Download PDFInfo
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- CN112854192A CN112854192A CN202110124865.9A CN202110124865A CN112854192A CN 112854192 A CN112854192 A CN 112854192A CN 202110124865 A CN202110124865 A CN 202110124865A CN 112854192 A CN112854192 A CN 112854192A
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
- E02D3/11—Improving or preserving soil or rock, e.g. preserving permafrost soil by thermal, electrical or electro-chemical means
- E02D3/115—Improving or preserving soil or rock, e.g. preserving permafrost soil by thermal, electrical or electro-chemical means by freezing
Abstract
The invention relates to an artificial stratum freezing method utilizing low-temperature carbon dioxide circulation refrigeration, which comprises the following steps: providing a freezing pipe, and driving the freezing pipe into an area needing freezing construction in the stratum; and providing a liquid carbon dioxide supply device, communicating the liquid carbon dioxide supply device with all the freezing pipes to form a first circulation loop, continuously feeding the liquid carbon dioxide into the freezing pipes through the liquid carbon dioxide supply device, and freezing the soil around the freezing pipes by using the liquid carbon dioxide in the freezing pipes to finish the freezing construction of the corresponding area in the stratum. The carbon dioxide can be recycled, so that the carbon dioxide is more economical and practical, and the freezing with higher efficiency at the same cost is realized.
Description
Technical Field
The invention relates to the technical field of stratum freezing, in particular to an artificial stratum freezing method utilizing low-temperature carbon dioxide circulation refrigeration.
Background
The artificial stratum freezing method (hereinafter referred to as "freezing method") is a special civil engineering construction method for changing natural soil into artificial frozen soil by using an artificial refrigeration technology, thereby improving the soil property to facilitate subsequent underground engineering construction.
Currently, among the available freezing methods, brine freezing is the most common and most widely used freezing method, followed by liquid nitrogen freezing. Among them, the freezing of brine is usually done: the temperature of the primary refrigerant is reduced by a compressor, then the temperature of the secondary refrigerant (calcium chloride brine) is reduced, and then the temperature of the soil body is reduced by continuously circulating the low-temperature brine in a freezing pipe which is driven into the soil body, so that frozen soil is gradually formed. The method has higher efficiency before the soil body is lowered to the freezing point, but the freezing efficiency of the brine is reduced along with the further reduction of the temperature of the soil body, and the situation that the temperature of the brine cannot be reduced in the later period often exists, so the total freezing period is longer, and the total cost is higher. The liquid nitrogen freezing process is relatively simple, and only liquid nitrogen needs to be introduced into the freezing pipe. The method is characterized in that new liquid nitrogen is poured into the frozen stratum every time, and the liquid nitrogen cannot be reused, so that the construction cost is high, and the method is usually used in engineering emergency. Generally, brine freezing and liquid nitrogen freezing have problems, respectively, in that the former is low in cost but low in efficiency, and the latter is high in efficiency but high in cost.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide an artificial stratum freezing method utilizing low-temperature carbon dioxide circulation refrigeration to realize more efficient freezing at the same cost.
In order to achieve the aim, the invention provides an artificial stratum freezing method utilizing low-temperature carbon dioxide circulation refrigeration, which comprises the following steps:
providing a freezing pipe, and driving the freezing pipe into a region needing freezing construction in a stratum;
and providing a liquid carbon dioxide supply device, communicating the liquid carbon dioxide supply device with all the freezing pipes to form a first circulation loop, continuously feeding liquid carbon dioxide into the freezing pipes through the liquid carbon dioxide supply device, and freezing the soil around the freezing pipes by using the liquid carbon dioxide in the freezing pipes to finish the freezing construction of the corresponding area in the stratum.
The invention continuously feeds liquid carbon dioxide into the freezing pipe through the liquid carbon dioxide supply device, freezes the soil around the freezing pipe by using the liquid carbon dioxide in the freezing pipe to finish the freezing construction of the corresponding area in the stratum so as to achieve better freezing effect, the melting point of the carbon dioxide is-56.6 ℃, the boiling point of the carbon dioxide is-78.5 ℃, the temperature for refrigerating the stratum by using the carbon dioxide can reach-45 ℃, is far lower than-30 ℃ of the freezing temperature of the conventional saline water, the refrigerating effect is better, the flow of the liquid carbon dioxide is only about 1/10 of the conventional frozen saline water, the energy consumption required by the circulation is lower, the power consumption of the whole system is estimated to be 60 percent of the freezing temperature of the conventional saline water, the construction cost is reduced, the flow of the liquid carbon dioxide is small, the viscosity is low, and the sizes of the corresponding freezing equipment, the freezing pipe and each pipeline, not only saved the material, made the arranging of equipment more nimble convenient moreover, compare in the unable used repeatedly of liquid nitrogen, this application can cyclic utilization carbon dioxide economy and practicality more to realize that more efficient freezes under the same expense.
The invention further improves the artificial stratum freezing method by using the low-temperature carbon dioxide circulation refrigeration, and the step of providing the liquid carbon dioxide supply device comprises the following steps:
providing a first circulation pipeline, communicating the first circulation pipeline with all the freezing pipes and forming a first circulation loop;
filling a set amount of liquid carbon dioxide into the first circulation loop;
providing a carbon dioxide pump, installing the carbon dioxide pump on the first circulation pipeline, and enabling the liquid carbon dioxide in the first circulation loop to perform circulation motion through the carbon dioxide pump;
and providing a liquefying mechanism, installing the liquefying mechanism on the first circulating pipeline, and converting the carbon dioxide in the gas state in the first circulating pipeline into the carbon dioxide in the liquid state by using the liquefying mechanism.
The invention further improves the artificial stratum freezing method by using low-temperature carbon dioxide circulation refrigeration, and the step of providing the liquefaction mechanism comprises the following steps:
providing a second circulation pipeline, wherein a second circulation loop is formed inside the second circulation pipeline, and the second circulation pipeline is attached to the first circulation pipeline part;
and filling a refrigerant into the second circulation pipeline, circulating the refrigerant in a second circulation loop formed in the second circulation pipeline, and further circularly utilizing the refrigerant to cool the first circulation pipeline so as to convert the gaseous carbon dioxide in the first circulation pipeline into liquid carbon dioxide.
The artificial stratum freezing method utilizing the low-temperature carbon dioxide circulation refrigeration is further improved in that the step of providing the liquefaction mechanism further comprises the following steps of:
a throttle valve is provided and mounted on the second circulation line.
The artificial stratum freezing method utilizing the low-temperature carbon dioxide cycle refrigeration is further improved in that the provided refrigerant is ammonia.
The further improvement of the artificial stratum freezing method utilizing the low-temperature carbon dioxide circulation refrigeration of the invention is that the method also comprises the following steps:
and providing a condensation mechanism, installing the condensation mechanism on the second circulation pipeline, and cooling the liquefaction mechanism by using the condensation mechanism.
The artificial stratum freezing method utilizing the low-temperature carbon dioxide circulation refrigeration is further improved in that the step of providing the liquefaction mechanism further comprises the following steps of:
providing a compressor, installing the compressor on the second circulation pipeline, and pressurizing the refrigerant by the compressor.
The invention further improves the artificial stratum freezing method by using low-temperature carbon dioxide circulation refrigeration, and the step of providing a condensation mechanism comprises the following steps:
providing a third circulation pipeline, wherein a third circulation loop is formed in the third circulation pipeline, the third circulation pipeline is attached to the second circulation pipeline part, and the part of the second circulation pipeline attached to the third circulation pipeline is different from the part of the second circulation pipeline attached to the first circulation pipeline;
filling cooling water into the third circulation pipeline, enabling the cooling water to circularly move in a third circulation loop formed in the third circulation pipeline, and further circularly utilizing the cooling water to cool the second circulation pipeline so as to convert the carbon dioxide in the gas state in the first circulation pipeline into the carbon dioxide in the liquid state;
and providing a cooling tower, installing the cooling tower on the third circulating pipeline, and transferring the heat absorbed by the cooling water to the outside air by using the cooling tower.
The further improvement of the artificial stratum freezing method utilizing the low-temperature carbon dioxide circulation refrigeration of the invention is that the method also comprises the following steps:
and providing a cooling water pump, installing the cooling water pump on the third circulation pipeline, and enabling the cooling water in the third circulation circuit to circularly move through the cooling water pump.
Drawings
FIG. 1 is a flow chart of a method of freezing a liquid carbon dioxide formation according to the present invention.
FIG. 2 is a construction state diagram of the freezing method of the liquid carbon dioxide stratum of the invention.
In the figure: the system comprises a freezing pipe-1, a first circulating pipeline-21, a carbon dioxide pump-22, a liquefying mechanism-23, a second circulating pipeline-231, a compressor-232, a throttle valve-233, a condensing mechanism-3, a third circulating pipeline-31, a cooling tower-32 and a cooling water pump-33.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides an artificial stratum freezing method utilizing low-temperature carbon dioxide circulation refrigeration, which is used for freezing a stratum. The invention continuously feeds liquid carbon dioxide into the freezing pipe through the liquid carbon dioxide supply device, freezes the soil around the freezing pipe by using the liquid carbon dioxide in the freezing pipe to finish the freezing construction of the corresponding area in the stratum so as to achieve better freezing effect, the melting point of the carbon dioxide is-56.6 ℃, the boiling point of the carbon dioxide is-78.5 ℃, the temperature for refrigerating the stratum by using the carbon dioxide can reach-45 ℃, is far lower than-30 ℃ of the freezing temperature of the conventional saline water, the refrigerating effect is better, the flow of the liquid carbon dioxide is only about 1/10 of the conventional frozen saline water, the energy consumption required by the circulation is lower, the power consumption of the whole system is estimated to be 60 percent of the freezing temperature of the conventional saline water, the construction cost is reduced, the flow of the liquid carbon dioxide is small, the viscosity is low, and the sizes of the corresponding freezing equipment, the freezing pipe and each pipeline, not only saved the material, made the arranging of equipment more nimble convenient moreover, compare in the unable used repeatedly of liquid nitrogen, this application can cyclic utilization carbon dioxide economy and practicality more to realize that more efficient freezes under the same expense.
The method for freezing the artificial formation by using the low-temperature carbon dioxide cycle refrigeration of the invention is explained below with reference to the accompanying drawings.
Referring to fig. 1 and 2, in the present embodiment, a method for freezing an artificial formation by using low-temperature carbon dioxide cycle refrigeration includes the following steps:
providing a freezing pipe 1, and driving the freezing pipe 1 into a region needing freezing construction in the stratum.
And providing a liquid carbon dioxide supply device, communicating the liquid carbon dioxide supply device with all the freezing pipes 1 to form a first circulation loop, continuously feeding liquid carbon dioxide into the freezing pipes 1 through the liquid carbon dioxide supply device, and freezing the soil around the freezing pipes 1 by using the liquid carbon dioxide in the freezing pipes 1 to finish the freezing construction of the corresponding area in the stratum.
In the freezing method of the embodiment, liquid carbon dioxide is continuously fed into the freezing pipe 1 through the liquid carbon dioxide supply device, the liquid carbon dioxide in the freezing pipe 1 is utilized to freeze the soil body around the freezing pipe 1 so as to finish the freezing construction of the corresponding region in the stratum, so as to achieve a better freezing effect, the melting point of the carbon dioxide is-56.6 ℃, the boiling point of the carbon dioxide is-78.5 ℃, the temperature for refrigerating the stratum by utilizing the carbon dioxide can reach-45 ℃, which is far lower than-30 ℃ of the freezing temperature of conventional saline water, the refrigerating effect is better, the flow rate of the liquid carbon dioxide is only about 1/10 of the conventional frozen saline water, the energy consumption required by the circulation is lower, the power consumption of the whole system is estimated to be 60 percent of the conventional saline water freezing, the construction cost is reduced, the flow rate of the liquid carbon dioxide is small, the viscosity, Freezing pipe 1 and the size of each pipeline and can accomplishing littleer, not only saved the material, make arranging of equipment nimble more convenient moreover, compare in the unable used repeatedly of liquid nitrogen, this application can cyclic utilization carbon dioxide economy and practicality more to realize under the same expense more efficient freezing.
Referring to fig. 2, in the present embodiment, the step of providing the liquid carbon dioxide supply means includes:
a first circulation line 21 is provided, and the first circulation line 21 is communicated with all the freezing pipes 1 and forms a first circulation loop.
The first circulation circuit is charged with a set amount of liquid carbon dioxide.
A carbon dioxide pump 22 is provided, the carbon dioxide pump 22 is attached to the first circulation line 21, and the liquid carbon dioxide in the first circulation circuit is circulated by the carbon dioxide pump 22.
A liquefaction mechanism 23 is provided, the liquefaction mechanism 23 is attached to the first circulation line 21, and the carbon dioxide in the gaseous state in the first circulation line 21 is converted into carbon dioxide in the liquid state by the liquefaction mechanism 23.
Referring to fig. 2, further, the step of providing a liquefaction mechanism 23 further comprises:
a compressor 232 is provided, the compressor 232 is attached to the second circulation line 231, and the refrigerant is pressurized by the compressor 232.
Referring to fig. 2, further, the step of providing a liquefaction mechanism 23 further includes:
a throttle 233 is provided, and the throttle 233 is installed on the second circulation line 231 to control the flow rate of the refrigerant.
Referring to fig. 2, further, the step of providing a condensing mechanism 3 includes:
a third circulation line 31 is provided, a third circulation circuit is formed in the third circulation line 31, the third circulation line 31 is partially attached to the second circulation line 231, and the portion where the second circulation line 231 is attached to the third circulation line 31 is not aligned with the portion where the second circulation line 231 is attached to the first circulation line 21.
The third circulation pipeline 31 is filled with cooling water, the cooling water performs a circulating motion in a third circulation loop formed inside the third circulation pipeline 31, and the cooling water is recycled to cool the second circulation pipeline 231, so that the gaseous carbon dioxide in the first circulation pipeline 21 is converted into liquid carbon dioxide.
A cooling tower 32 is provided, the cooling tower 32 is attached to the third circulation line 31, and heat absorbed from the cooling water is transferred to the outside air by the cooling tower 32.
In this embodiment, the provided refrigerant is ammonia. However, the refrigerant used in the present application is not limited to ammonia, and includes a method of circulating refrigeration using another refrigerant such as freon. Taking ammonia circulation as an example, liquid ammonia absorbs heat and is evaporated into low-temperature and low-pressure saturated vapor ammonia, the low-temperature and low-pressure vapor ammonia is compressed into high-temperature and high-pressure vapor ammonia by the compressor 232 and then enters the condensing mechanism 3 for cooling, the cooled high-pressure liquid ammonia is decompressed by the throttle valve 233 and then is changed into liquid ammonia again, and heat exchange is performed between the liquid ammonia and carbon dioxide in the first circulation pipeline 21, so that an ammonia circulation system is formed. The ammonia circulation system transfers heat absorbed by the liquid ammonia to the cooling water.
Referring to fig. 2, in the present embodiment, the freezing method further includes:
a condensing means is provided, the condensing means 3 is attached to the second circulation line 231, and the condensing means 3 cools the liquefying means 23.
Preferably, the refrigerant in the gaseous state is pressurized by the compressor 232, and the pressurized refrigerant in the gaseous state in the second circulation line 231 exchanges heat with the cooling water in the third circulation line 31 to liquefy the refrigerant in the gaseous state into a refrigerant in the liquid state, so that the carbon dioxide in the gaseous state can be liquefied into carbon dioxide in the liquid state by circulating the refrigerant.
Referring to fig. 2, further, the freezing method further includes:
a cooling water pump 33 is provided, the cooling water pump 33 is attached to the third circulation line 31, and the cooling water in the third circulation circuit is circulated by the cooling water pump 33.
Preferably, the freezing pipe 1 is driven vertically into the formation by a pipe jacking method, a pipe ramming method or a directional drilling method.
The freezing method further comprises the following steps: providing a heat insulation box, and sleeving the heat insulation box on the portion where the second circulation pipeline 231 is attached to the third circulation pipeline 31 and the portion where the second circulation pipeline 231 is attached to the first circulation pipeline 21, so as to isolate the heat exchange between the first circulation pipeline 21, the second circulation pipeline 231, and the third circulation pipeline 31 and the outside air.
Referring to fig. 2, in the present embodiment, the first circulation line 21 is provided with pairs of inlet and outlet ends, and the freezing method further includes:
the inlet end extends into the bottom of the corresponding freezing pipe 1, the outlet end is hermetically connected to the top of the corresponding freezing pipe 1, the liquid carbon dioxide flowing out of the inlet end continuously enters the bottom of the freezing pipe 1, the carbon dioxide flows into the freezing pipe 1 continuously and rises along with the continuous pressing of new carbon dioxide, heat exchange is carried out between the carbon dioxide and the surrounding soil, and the carbon dioxide flows into the first circulation pipeline 21 through the outlet end when the carbon dioxide rises to the top of the freezing pipe 1.
In this embodiment, the liquid carbon dioxide in the first circulation line flows into the freezing pipe 1 through the carbon dioxide pump 22 to absorb heat of the surrounding formation, wherein a part of the liquid carbon dioxide is vaporized into gaseous carbon dioxide, the carbon dioxide flowing out of the ground through the freezing pipe 1 is a gas-liquid mixture, the mixture flows through the liquefaction mechanism 3 to liquefy the gaseous carbon dioxide into liquid carbon dioxide, and the carbon dioxide in the first circulation line is converted into liquid carbon dioxide and then flows into the freezing pipe 1, so that a carbon dioxide circulation system is formed. The carbon dioxide circulation system transfers heat in the formation to the refrigerant in the second circulation line of the liquefaction mechanism 3. The refrigerant in the second circulation line absorbs heat and evaporates to become a low-temperature low-pressure saturated vapor refrigerant, the low-temperature low-pressure vapor refrigerant is compressed into a high-temperature high-pressure vapor refrigerant by the compressor 32 and then enters the condensing mechanism 4 to be cooled, and the cooled high-pressure liquid refrigerant is decompressed by the throttle valve 34 and then becomes a liquid refrigerant again to exchange heat with carbon dioxide in the first circulation line 21, thereby forming a refrigerant circulation system. The refrigerant circulation system transfers heat absorbed by the liquid refrigerant to the cooling water in the condensation mechanism 4. The low-temperature cooling water in the third circulation pipeline absorbs heat from the refrigerant in the second circulation pipeline and is changed into high-temperature cooling water, the low-temperature cooling water is formed again after being cooled by the cooling tower 42, and then the low-temperature cooling water exchanges heat with the refrigerant in the second circulation pipeline after passing through the cooling water pump 44 to form cooling water circulation. The cooling water cycle transfers heat absorbed from the refrigerant to the outside air. Finally, the heat of the formation and the heat generated by the compressor 32 are transferred to the outside air through three cycles of the carbon dioxide cycle, the refrigerant cycle and the cooling water cycle, so that the temperature of the formation is reduced, and the soil around the freezing pipe 1 is changed into frozen soil.
And (3) after the temperature of the carbon dioxide is reduced to the design temperature (-38 ℃ to-45 ℃), entering a maintenance freezing stage, and performing freezing underground excavation (including shield tunneling in and out of a hole), structure construction and the like after the set conditions are reached. And stopping freezing after the structure is completely applied and reaches a certain strength, sealing the freezing holes, and performing thaw settlement grouting according to settlement monitoring.
In one embodiment, the specific construction method is as follows:
first step, construction preparation:
1) constructors and equipment materials enter the field;
2) the construction water, electricity and sewage are connected into corresponding lines or pipelines;
3) constructing a construction working face, and freezing a station site enclosure;
4) handing over construction coordinate points;
step two, freezing the construction of the pipe 1:
1) measuring and lofting a freezing hole;
2) drilling holes in the freezing holes, namely fixing a fixed drilling machine, drilling the holes, installing a hole opening pipe (winding hemp threads outside the fish scale buckle during installation) in the drilling holes, and installing a control valve; if water seepage occurs, injecting polyurethane for plugging by a needle eye method;
3) the freezing hole pipe-jacking construction method comprises a freezing hole, a temperature measuring hole, a pressure relief hole and the like. When the pipe is pushed, the ejector rod is connected with the guide head at the head of the freezing pipe 1, the piston of the pipe pushing jack is connected with the tail end of the ejector rod, the hydraulic pump is started, the piston of the hydraulic cylinder extends to apply thrust to the ejector rod, and the ejector rod transmits the thrust to the guide head at the head of the freezing pipe 1, so that the whole freezing pipe 1 is driven to enter the stratum;
4) and moving the push bench away after the jacking reaches the designed depth, and pulling out the push rod. Then, the depth of the freezing pipe 1 is retested, and leakage test of the freezing pipe 1 is carried out;
5) grouting and water sealing are carried out through the orifice pipe bypass, and cement-water glass is adopted for grouting liquid;
6) a carbon dioxide liquid supply pipe is arranged in the freezing pipe 1. Recording the length of each liquid supply pipe, and checking whether the length of the liquid supply pipe and the length of the freezing pipe 1 are consistent or not;
7) the temperature measuring pipe and the pressure relief pipe are installed in the same way. In the water-containing sand layer, the pressure relief pipe is densely filled with the pseudo-ginseng soil and then is tamped into the stratum. After the pressure relief pipe is tamped to the designed depth, a water pressure meter and a valve are installed on the orifice pipe, and then water is flushed in the pipe to ensure that the pressure relief hole is smooth.
Thirdly, installing a freezing system:
1) mounting low-temperature carbon dioxide freezing equipment, namely lofting an equipment foundation → anchoring a foundation bolt → positioning the equipment, leveling, fixing → laying a cable → mounting an electric control system → commissioning a refrigeration system → insulating a low-temperature container and a pipeline;
2) the method comprises the following steps of freezing station pipeline installation, including main pipeline lofting → installation pipe frame → installation of main pipeline → installation of branch pipeline → installation of pressure and temperature measuring points → pipeline purging and leakage testing → pipeline painting → carbon dioxide dry pipe heat preservation;
3) the freezer is connected, and comprises the steps of installing and connecting the head of the freezer, cold discharge pipes and the liquid collecting and distributing pipes → the head of the freezer, connecting rubber pipes and the liquid collecting and distributing pipes for heat preservation.
Fourth step, active freezing
1) Checking and confirming that a circuit system, a cooling water circulation system, a carbon dioxide circulation system, an ammonia circulation system and the like are normal, starting up and running in a trial mode, gradually adjusting state parameters such as energy, pressure, temperature, motor load and the like, and enabling the unit to run under the condition of technical parameters related to equipment regulations and running requirements;
2) after the test run is normal, the active freezing is carried out, and relevant parameters of a refrigerating system are adjusted according to the temperature of cooling water and the temperature of liquid carbon dioxide, so that the high refrigerating efficiency is ensured;
3) after freezing begins, checking the frosting of the freezer and monitoring the return liquid temperature periodically, and taking measures such as adjusting a control valve in time when the frosting or the return liquid temperature is uneven;
4) analyzing the formation and development conditions of the freezing wall according to the temperature of the temperature measuring hole and the pressure monitoring result of the pressure relief hole;
5) the frost heaving deformation is monitored every day, the operation parameters of the freezing system are checked and recorded every two hours, and problems are analyzed and processed in time.
The fifth step, maintenance freezing
1) According to the temperature monitoring data, after the conditions such as the thickness of the frozen wall, the average temperature and the like are analyzed, excavation and permanent structure construction are carried out;
2) in the process of maintaining and freezing, the freezing construction monitoring is carried out as in the active freezing process, and the normal operation of a freezing system is ensured. Meanwhile, monitoring the temperature of the frozen wall, the surface temperature of the frozen soil of the excavation face and the surface displacement condition of the frozen wall;
3) the peripheral heat-insulating layer cannot be damaged in the excavation process, and the freezing pipe 1 is prevented from leaking due to overexcavation.
The sixth step, stop freezing and ending
1) Stopping freezing after the permanent structure is poured;
2) completing the plugging of the freezing hole within 5 days after the freezing is stopped, cutting off the orifice pipe, then blowing dry residues in the pipe by using compressed air, and filling cement mortar or concrete;
3) forced thawing or natural thawing is adopted according to requirements. Forced thawing is carried out after the main structure concrete reaches over 75% of the designed strength;
4) and performing the thaw grouting during the natural thawing period, and adjusting grouting parameters according to the actual measurement condition.
Seventh, safety measures
Due to the ultra-low temperature of the low temperature liquid carbon dioxide and the asphyxiating characteristics of the gaseous carbon dioxide, the following technical and institutional measures need to be taken to ensure personnel safety:
1) the protection of operators, including anti-freezing protective clothing, strict bare-handed contact with low-temperature components such as a liquid carbon dioxide storage tank and the like, wearing anti-blowout goggles and the like;
2) the respiratory self-rescue professional equipment is arranged on the site, the related warning board and operation rules are hung on the site, and the field equipment management and operation are in line with the technical requirements of the pressure container and the pressure pipeline;
3) emergency facilities such as an oxygen concentration monitoring system and a local ventilator are arranged on the site, and emergency rescue drilling is carried out regularly.
By adopting the technical scheme, the invention has the following beneficial effects:
the invention continuously feeds liquid carbon dioxide into the freezing pipe through the liquid carbon dioxide supply device, freezes the soil around the freezing pipe by using the liquid carbon dioxide in the freezing pipe to finish the freezing construction of the corresponding area in the stratum so as to achieve better freezing effect, the melting point of the carbon dioxide is-56.6 ℃, the boiling point of the carbon dioxide is-78.5 ℃, the temperature for refrigerating the stratum by using the carbon dioxide can reach-45 ℃, is far lower than-30 ℃ of the freezing temperature of the conventional saline water, the refrigerating effect is better, the flow of the liquid carbon dioxide is only about 1/10 of the conventional frozen saline water, the energy consumption required by the circulation is lower, the power consumption of the whole system is estimated to be 60 percent of the freezing temperature of the conventional saline water, the construction cost is reduced, the flow of the liquid carbon dioxide is small, the viscosity is low, and the sizes of the corresponding freezing equipment, the freezing pipe and each pipeline, not only saved the material, made the arranging of equipment more nimble convenient moreover, compare in the unable used repeatedly of liquid nitrogen, this application can cyclic utilization carbon dioxide economy and practicality more to realize that more efficient freezes under the same expense.
Claims (9)
1. An artificial stratum freezing method utilizing low-temperature carbon dioxide circulation refrigeration is characterized by comprising the following steps:
providing a freezing pipe, and driving the freezing pipe into a region needing freezing construction in a stratum;
and providing a liquid carbon dioxide supply device, communicating the liquid carbon dioxide supply device with all the freezing pipes to form a first circulation loop, continuously feeding liquid carbon dioxide into the freezing pipes through the liquid carbon dioxide supply device, and freezing the soil around the freezing pipes by using the liquid carbon dioxide in the freezing pipes to finish the freezing construction of the corresponding area in the stratum.
2. The method of claim 1, wherein the step of providing a liquid carbon dioxide supply comprises:
providing a first circulation pipeline, communicating the first circulation pipeline with all the freezing pipes and forming a first circulation loop;
filling a set amount of liquid carbon dioxide into the first circulation loop;
providing a carbon dioxide pump, installing the carbon dioxide pump on the first circulation pipeline, and enabling the liquid carbon dioxide in the first circulation loop to perform circulation motion through the carbon dioxide pump;
and providing a liquefying mechanism, installing the liquefying mechanism on the first circulating pipeline, and converting the carbon dioxide in the gas state in the first circulating pipeline into the carbon dioxide in the liquid state by using the liquefying mechanism.
3. The method of claim 2, wherein the step of providing a liquefaction mechanism comprises:
providing a second circulation pipeline, wherein a second circulation loop is formed inside the second circulation pipeline, and the second circulation pipeline is attached to the first circulation pipeline part;
and filling a refrigerant into the second circulation pipeline, circulating the refrigerant in a second circulation loop formed in the second circulation pipeline, and further circularly utilizing the refrigerant to cool the first circulation pipeline so as to convert the gaseous carbon dioxide in the first circulation pipeline into liquid carbon dioxide.
4. The method of claim 3, wherein the step of providing a liquefaction mechanism further comprises:
a throttle valve is provided and mounted on the second circulation line.
5. The method of claim 3, wherein the refrigerant is ammonia.
6. The method of claim 3, further comprising:
and providing a condensation mechanism, installing the condensation mechanism on the second circulation pipeline, and cooling the liquefaction mechanism by using the condensation mechanism.
7. The method of claim 6, wherein the step of providing a liquefaction mechanism further comprises:
providing a compressor, installing the compressor on the second circulation pipeline, and pressurizing the refrigerant by the compressor.
8. The method of claim 6, wherein the step of providing a condensing mechanism comprises:
providing a third circulation pipeline, wherein a third circulation loop is formed in the third circulation pipeline, the third circulation pipeline is attached to the second circulation pipeline part, and the part of the second circulation pipeline attached to the third circulation pipeline is different from the part of the second circulation pipeline attached to the first circulation pipeline;
filling cooling water into the third circulation pipeline, enabling the cooling water to circularly move in a third circulation loop formed in the third circulation pipeline, and further circularly utilizing the cooling water to cool the second circulation pipeline so as to convert the carbon dioxide in the gas state in the first circulation pipeline into the carbon dioxide in the liquid state;
and providing a cooling tower, installing the cooling tower on the third circulating pipeline, and transferring the heat absorbed by the cooling water to the outside air by using the cooling tower.
9. The method of claim 8, further comprising:
and providing a cooling water pump, installing the cooling water pump on the third circulation pipeline, and enabling the cooling water in the third circulation circuit to circularly move through the cooling water pump.
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