阅读说明：本技术 一种煤矿液体二氧化碳直注系统及工艺 (Coal mine liquid carbon dioxide direct injection system and process ) 是由 韩晓琢 闫志贤 韩汉生 *** 闫曌 郭潞君 于 2019-11-01 设计创作，主要内容包括：本发明还公开了一种煤矿液体二氧化碳直注系统及工艺,将液态二氧化碳液态输送到减压阀组将二氧化碳的压强减至1.6～1.8MPa后输送至稳压阀组,使二氧化碳以压力0.8～1.0MPa、温度-20～-40℃的状态进入到惰化区,在惰化区经节流后形成含有干冰的低温气流进行惰化冷却。本发明利用二氧化碳输送管路导热性能和与输送环境的温差将部分液体汽化,通过控制注入量和注入压力调节二氧化碳惰化区温度和气液比例,使进入惰化区的二氧化碳通过节流后在惰化区内形成含少量干冰的低温气流,低温气流再与惰化区内气体对流换热,使得惰化区空间在充分惰化的同时得到快速冷却。(The invention also discloses a direct injection system and a direct injection process for the liquid carbon dioxide in the coal mine, which are characterized in that the liquid carbon dioxide is conveyed to a pressure reducing valve bank to reduce the pressure of the carbon dioxide to 1.6-1.8 MPa and then conveyed to a pressure stabilizing valve bank, so that the carbon dioxide enters an inerting area under the conditions of the pressure of 0.8-1.0 MPa and the temperature of-20 to-40 ℃, and forms low-temperature air flow containing dry ice for inerting and cooling after throttling in the inerting area. The invention uses the heat-conducting property of the carbon dioxide conveying pipeline and the temperature difference with the conveying environment to vaporize partial liquid, adjusts the temperature and the gas-liquid ratio of the carbon dioxide inerting area by controlling the injection amount and the injection pressure, so that the carbon dioxide entering the inerting area forms low-temperature airflow containing a small amount of dry ice in the inerting area after throttling, and the low-temperature airflow carries out convective heat exchange with the gas in the inerting area, thereby leading the space of the inerting area to be rapidly cooled while being fully inerted.)

1. The utility model provides a colliery liquid carbon dioxide directly annotates system which characterized in that includes: the device comprises an injection valve bank, a pressure reducing valve bank, a pressure stabilizing valve bank and a conveying pipeline, wherein the injection valve bank is communicated with a liquid carbon dioxide source, the pressure stabilizing valve bank is used for conveying low-temperature oxidation to an inerting area, and the conveying pipeline is used for conveying low-temperature oxidation to the inerting area; the injection valve group comprises a flow control valve and an emptying valve arranged behind the flow control valve, the pressure reducing valve group comprises a pressure reducing valve, a front pressure reducing valve cut-off valve arranged in front of the pressure reducing valve, a rear pressure reducing valve cut-off valve arranged behind the pressure reducing valve, a first parallel pipeline respectively connected with an inlet of the front pressure reducing valve cut-off valve and an outlet of the rear pressure reducing valve cut-off valve, a first bypass valve and a pilot valve arranged on the parallel pipeline, and the index of a pressure gauge behind the pressure reducing valve is 1.6-1.8 MPa; the pressure stabilizing valve group comprises a pressure stabilizing valve, a pressure stabilizing valve front cut-off valve arranged in front of the pressure stabilizing valve, a pressure stabilizing valve rear cut-off valve arranged behind the pressure stabilizing valve, a second parallel pipeline respectively connected with an inlet of the pressure stabilizing valve front cut-off valve and an outlet of the pressure stabilizing valve rear cut-off valve, a second bypass valve and a pilot valve arranged on the parallel pipeline, wherein the value of a pressure gauge behind the pressure stabilizing valve is 0.8-1.0 MPa, and the indication number of a temperature gauge behind the pressure stabilizing valve is-20 to-40 ℃.

2. The coal mine liquid carbon dioxide direct injection system of claim 1, wherein: the injection valve group also comprises at least one carbon dioxide injection switching valve, a carbon dioxide flow meter, a pressure meter before the flow control valve, a temperature meter before the flow control valve, a pressure meter after the flow control valve, a temperature meter after the flow control valve and a safety valve before the emptying valve.

3. The coal mine liquid carbon dioxide direct injection system of claim 1, wherein: the pressure reducing valve bank further comprises a pressure reducing valve front temperature gauge arranged in front of the pressure reducing valve front cut-off valve and a pressure reducing valve rear temperature gauge arranged behind the pressure reducing valve rear cut-off valve, and the first parallel pipeline is sequentially provided with a pressure reducing valve front pressure gauge, a first pilot valve, a first bypass valve, a second pilot valve and a pressure reducing valve rear pressure gauge.

4. The coal mine liquid carbon dioxide direct injection system of claim 1, wherein: the pressure stabilizing valve group further comprises a pressure stabilizing valve front temperature gauge arranged in front of a pressure stabilizing valve front cut-off valve and a pressure stabilizing valve rear temperature gauge arranged behind a pressure stabilizing valve rear cut-off valve, and a pressure stabilizing valve front pressure gauge, a third guide shower valve, a second bypass valve, a fourth guide shower valve and a pressure stabilizing valve rear pressure gauge are sequentially arranged on the second parallel pipeline.

5. The coal mine liquid carbon dioxide direct injection system of claim 1, wherein: the inerting area is a closed area formed by a closed wall and a mine, a discharge pipeline communicated with an outlet of the pressure stabilizing valve group is arranged in the inerting area, the outer part of the discharge pipeline, which extends out of the closed wall, extends into the closed wall, an inner closed valve or a front closed valve is arranged on the discharge pipeline inside or outside the closed wall, and the inner closed valve is a front valve type pressure opening self-operated regulating valve or a one-way valve.

6. The coal mine liquid carbon dioxide direct injection system of claim 5, wherein: the release pipeline is also provided with a branch pipeline, the outer part of the self-closing wall of the branch pipeline extends into the self-closing wall, the branch pipeline is provided with a front closing valve, the front closing valve is positioned outside the self-closing wall, and the front closing valve is a front valve type pressure opening self-operated regulating valve or a one-way valve.

7. The coal mine liquid carbon dioxide direct injection system of claim 1, wherein: the pressure reducing valve and the pressure stabilizing valve are selected from one of a self-operated regulating valve, a pneumatic regulating valve and an electric regulating valve.

8. The coal mine liquid carbon dioxide direct injection system of claim 7, wherein: the pressure reducing valve and the pressure stabilizing valve are respectively a valve rear type pressure-closing self-operated regulating valve and a valve front type pressure-opening self-operated regulating valve.

9. A coal mine liquid carbon dioxide direct injection process is characterized by comprising the following steps: and conveying the liquid carbon dioxide to a pressure reducing valve bank to reduce the pressure of the carbon dioxide to 1.6-1.8 MPa, conveying the carbon dioxide to a pressure stabilizing valve bank, enabling the carbon dioxide to enter an inerting area under the conditions that the pressure is 0.8-1.0 MPa and the temperature is-20 to-40 ℃, and throttling the inerting area to form low-temperature air flow containing dry ice for inerting and cooling.

Technical Field

The invention belongs to the technical field of mine safety, relates to a coal mine fire prevention and extinguishing system, and particularly relates to a coal mine liquid carbon dioxide direct injection system and a coal mine liquid carbon dioxide direct injection process.

Background

At present, two methods applied to inerting a coal mine liquid carbon dioxide mine in China comprise a vaporization method and a direct injection before closing, are limited by an injection process and injection conditions, and have larger application defects.

A vaporization method; the method is characterized in that liquid carbon dioxide from a carbon dioxide tank car is gasified through an air bath type vaporizer and a water bath type vaporizer, the gasification process needs to be carried out under the assistance of heat power or electric power, the power consumption of the water bath type vaporizer for vaporizing 1 ton of liquid carbon dioxide is about 100-120 KW/h, the vaporized carbon dioxide enters a well at the temperature of 30-40 ℃, and the gas is cooled through an input pipeline and is closed at the temperature of about 20-30 ℃. The method has the advantages that the carbon dioxide injection operation is completely carried out on the ground, the operation environment is suitable, the liquid carbon dioxide enters the well at low pressure after being completely gasified, the failure rate in the conveying process is low, and the whole inerting process is safe and reliable. But has more defects limited by the implantation process method; firstly, gasification equipment is bulky, and the gasification equipment's of being not convenient for fast speed adjusting fortune and vaporization field selection must have high-power to assist, and the power consumptive height of vaporization process has increased carbon dioxide and has injected into cost and the operation degree of difficulty. Thirdly, the narrow control parameter range of the carbon dioxide vaporization process has large operation difficulty, and fourthly, the carbon dioxide entry-closing temperature is high, which is not beneficial to the cooling of coal bodies in the closing and the control of the high-temperature hot spot oxidation speed.

Direct injection before closure; namely, the liquid carbon dioxide from the carbon dioxide tank wagon is firstly split charged into 175-200L dewar cans or 1-2 m³The special liquid carbon dioxide storage tank is fixed on the mine car, the mine car is used for transporting the mine car to the position before closing, and then the mine car is directly injected into the closing through a liquid phase outlet of the Dewar tank or the special liquid carbon dioxide storage tank. The advantages of this method areThe device is simple in entering process and easy to operate, and the liquid carbon dioxide is directly injected into the closed space before closing, so that the closing temperature is low, and the cooling of the closed space and the control of the high-temperature hot spot oxidation speed are facilitated. But the operation space and the closing mode limit also have more defects; firstly, pressure vessel is in the turnover of limited space, and the operation process unpredictable factor is many, and equipment safety is difficult to guarantee, is not convenient for inject into the operation long-time operation. And secondly, the turnover speed of the whole injection process is low due to the limitation of the quantity and the volume of the Dewar tank or the special liquid carbon dioxide storage tank, and the continuous mass injection of the liquid carbon dioxide is difficult to realize. And thirdly, liquid carbon dioxide is directly injected to easily form dry ice deposition near the discharge port, so that the inerting speed of the system in the closed area is reduced. Fourthly, injection operation is carried out in a narrow and small limited space, carbon dioxide leakage is not easy to diffuse, dangerous factors are more in the operation process, and the environmental safety risk is large.

Disclosure of Invention

The invention discloses a coal mine liquid carbon dioxide direct injection system and a coal mine liquid carbon dioxide direct injection process, which aim to solve the problems of an evaporation method and a pre-closing direct injection method in the existing coal mine liquid carbon dioxide mine inerting method.

The technical scheme of the invention is realized as follows:

on one hand, the invention discloses a coal mine liquid carbon dioxide direct injection system, which comprises an injection valve group, a pressure reducing valve group, a pressure stabilizing valve group and a conveying pipeline, wherein the injection valve group and the pressure reducing valve group are communicated with a liquid carbon dioxide source; the injection valve group comprises a flow control valve and an emptying valve arranged behind the flow control valve, the pressure reducing valve group comprises a pressure reducing valve, a front pressure reducing valve cut-off valve arranged in front of the pressure reducing valve, a rear pressure reducing valve cut-off valve arranged behind the pressure reducing valve, a first parallel pipeline respectively connected with an inlet of the front pressure reducing valve cut-off valve and an outlet of the rear pressure reducing valve cut-off valve, a first bypass valve and a pilot valve arranged on the parallel pipeline, and the index of a pressure gauge behind the pressure reducing valve is 1.6-1.8 MPa; the pressure stabilizing valve group comprises a pressure stabilizing valve, a pressure stabilizing valve front cut-off valve arranged in front of the pressure stabilizing valve, a pressure stabilizing valve rear cut-off valve arranged behind the pressure stabilizing valve, a second parallel pipeline respectively connected with an inlet of the pressure stabilizing valve front cut-off valve and an outlet of the pressure stabilizing valve rear cut-off valve, a second bypass valve and a pilot valve arranged on the parallel pipeline, wherein the value of a pressure gauge behind the pressure stabilizing valve is 0.8-1.0 MPa, and the indication number of a temperature gauge behind the pressure stabilizing valve is-20 to-40 ℃. The liquid carbon dioxide source used for coal mine fire fighting is typically in the form of a carbon dioxide tanker, although the invention is also applicable to other liquid carbon dioxide sources besides carbon dioxide tankers. The inerting zone may be closed or unsealed.

Typically, the injection valve block is located above the mine, the pressure relief valve block and the pressure regulator valve block are located below the mine, and the pressure regulator valve block is located near the inerting area.

As a preferred embodiment, the injection valve group further comprises at least one carbon dioxide injection switching valve, a carbon dioxide flow meter, a pressure meter before the flow control valve and a temperature meter before the flow control valve, a pressure meter after the flow control valve and a temperature meter after the flow control valve, and a safety valve before the evacuation valve; 2 safety valves which can work simultaneously are preferably arranged, and the arrangement of a carbon dioxide flow meter, the front/back temperature of the flow control valve and the front/back pressure gauge of the flow control valve can facilitate the control of the injection process; the carbon dioxide injection switching valve is used for replacing and switching the carbon dioxide tank car, the flow control valve is used for adjusting and controlling the injection speed of the system, the emptying valve and the safety valve are used for guaranteeing the operation pressure of the limiting system and the injection safety, and the safety valve is set with the trip pressure of 2 MPa (meter).

The pressure reducing valve bank also comprises a pressure reducing valve front temperature gauge arranged in front of a pressure reducing valve front cut-off valve and a pressure reducing valve rear temperature gauge arranged behind a pressure reducing valve rear cut-off valve, and the first parallel pipeline is sequentially provided with a pressure reducing valve front pressure gauge, a first pilot valve, a first bypass valve, a second pilot valve and a pressure reducing valve rear pressure gauge; the arrangement of the front/rear thermometer of the pressure reducing valve and the front/rear pressure gauge of the pressure reducing valve can facilitate observation and adjustment.

The pressure stabilizing valve group can reduce repeated pressurization of a system in the vehicle replacement process and effectively prevent carbon dioxide from forming dry ice in a pipeline to block the pipeline in the injection process; as a preferred embodiment, the pressure stabilizing valve group further comprises a pressure stabilizing valve front temperature gauge arranged in front of a pressure stabilizing valve front cut-off valve and a pressure stabilizing valve rear temperature gauge arranged behind a pressure stabilizing valve rear cut-off valve, and a pressure stabilizing valve front pressure gauge, a third pilot shower valve, a second bypass valve, a fourth pilot shower valve and a pressure stabilizing valve rear pressure gauge are sequentially arranged on the second parallel pipeline; the arrangement of the pressure stabilizing valve front/rear thermometer and the pressure stabilizing valve front/rear pressure gauge is convenient for observing and adjusting gas inlet and outlet parameters.

When the inerting area is a closed inerting area, as a preferred embodiment, the inerting area is a closed area surrounded by a closed wall and a mine, a discharge pipeline communicated with an outlet of the pressure stabilizing valve group is arranged in the inerting area, the outer part of the self-closed wall of the discharge pipeline extends into the closed wall, a closed inner valve is arranged on the discharge pipeline in the closed wall, and the closed inner valve is a valve-front pressure-opening self-operated regulating valve or a one-way valve in order to prevent the closed inner pipeline and the discharge pipeline from forming dry ice; the carbon dioxide inlet valve can be operated by adopting a double loop, a branch pipeline is additionally arranged on the discharge pipeline, the outer part of the self-closing wall of the branch pipeline extends into the self-closing wall, a front closing valve is arranged on the branch pipeline and is positioned outside the self-closing wall, and the front closing valve is a front valve type pressure opening self-operated regulating valve or a one-way valve respectively. Furthermore, the discharge pipeline after the front valve and the inner valve are closed can not be provided with elbows, reducing pipes and other pipes which can obstruct the flow of gas, and the length of the discharge pipeline after the valve is less than 10 times of the diameter of the pipeline. In order to optimize the distribution of carbon dioxide airflow in a sealed area and ensure that dry ice formed in the discharge process can be sublimated quickly, the distance between a discharge pipeline and a bottom plate is more than 0.8m, the carbon dioxide closing and entering adopts double-loop operation, and the double-system closing and entering can carry out secondary adjustment on the distribution of the carbon dioxide airflow in the sealed area and improve the reliability of system operation to the maximum extent.

In a preferred embodiment, the pressure reducing valve and the pressure maintaining valve are selected from one of a self-operated regulating valve, a pneumatic regulating valve and an electric regulating valve, if the self-operated regulating valve is selected, the pressure reducing valve is preferably a valve rear type pressure-closing self-operated regulating valve, and the pressure maintaining valve is preferably a valve front type pressure-opening self-operated regulating valve.

On the other hand, the invention also discloses a direct injection process of the liquid carbon dioxide in the coal mine, which is characterized in that liquid carbon dioxide is conveyed to a pressure reducing valve bank to reduce the pressure of the carbon dioxide to 1.6-1.8 MPa and then conveyed to a pressure stabilizing valve bank, so that the carbon dioxide enters an inerting area under the conditions of the pressure of 0.8-1.0 MPa and the temperature of-20 to-40 ℃, and low-temperature air flow containing dry ice is formed for inerting and cooling after the inerting area is throttled by closing an inner valve.

The invention has the beneficial effects that:

(1) the injection system can adjust the injection amount in a large range by improving the conditions of the conveying pipeline; the injection power consumption is low, a high-power supply and a heat source do not need to be equipped for assistance, the inerting scheme is easier to implement, and the carbon dioxide injection can save 100-120 KW/ton of electric power compared with the traditional method; the defects of complex equipment, high power consumption, high operation difficulty, high carbon dioxide inlet and outlet temperature and the like of the traditional vaporization method for inerting the mine are overcome;

(2) the carbon dioxide is low in closing temperature, low-temperature airflow with the temperature of about-56.6 ℃ can be formed in the closed environment, the mine can be fully cooled while being inerted, and the purpose of quickly eliminating the fire and hidden danger of the mine is achieved; on the premise of avoiding the deposition of dry ice near the injection port, the dry ice is quickly cooled while being fully inerted; the inerting operation does not need to separately load and transport liquid carbon dioxide, and the injection operation is completely centralized on the ground, so that the whole carbon dioxide injection process is more reliable and safer;

(3) in the process of inerting the mine, a vaporizer is not needed for vaporization, other containers and storage tanks are not needed for transporting the liquid carbon dioxide to the bottom of the well, and the wellhead direct injection of the liquid carbon dioxide can be realized under the conditions of no electric power and heat source assistance. Compared with the traditional method, the operation process of the technology is completely carried out on the ground, the safety risk is small, and the control is easy.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a flow chart of the injection process of the coal mine liquid carbon dioxide direct injection system in the embodiment of the invention.

Fig. 2 is a schematic flow diagram of the valve assembly of fig. 1.

Fig. 3 is a schematic flow diagram of the pressure relief valve assembly of fig. 1.

Fig. 4 is a schematic flow chart of the pressure stabilizing valve block in fig. 1.

FIG. 5 is a schematic diagram of the structure of the inerting zone.

In the figure: 1. carbon dioxide tank car; 2. an injection valve group; 3. a pressure relief valve bank; 4. a pressure stabilizing valve bank; 5. a delivery line; 6, closing a front valve; 7. closing the wall; 8. a roadway closure area; 9. closing the internal valve; 11. a first carbon dioxide injection switching valve; 12. a carbon dioxide flow meter; 13. a flow control valve front pressure gauge; 14. A flow control valve front thermometer; 15. a flow control valve; 16. a flow control valve back pressure gauge; 17. a flow control valve rear thermometer; 18. a first safety valve; 19. a second relief valve; 110. a second carbon dioxide injection switching valve; 111. an evacuation valve; 21. a temperature gauge in front of the pressure reducing valve; 22. a front cut-off valve of the reducing valve; 23. a pressure reducing valve; 24. a rear cut-off valve of the reducing valve; 25. a post-pressure relief valve thermometer; 26. a pressure gauge in front of the pressure reducing valve; 27. a first bypass valve; 28. a pressure gauge behind the pressure reducing valve; 29. a first pilot shower valve; 210. a second pilot shower valve; 31. a temperature gauge in front of the pressure stabilizing valve; 32. a front stop valve of the pressure stabilizing valve; 33. a pressure maintaining valve; 34. a rear stop valve of the pressure stabilizing valve; 35. a pressure stabilizing valve rear thermometer; 36. a pressure gauge in front of the pressure stabilizing valve; 37. a second bypass valve; 38. a pressure gauge behind the pressure stabilizing valve; 39. a third pilot shower valve; 40. and a fourth pilot shower valve.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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 direct injection system for coal mine liquid carbon dioxide as shown in figure 1 ~ 5 comprises an injection valve group 2, a pressure reducing valve group 3, a pressure stabilizing valve group 4 and a conveying pipeline 5, wherein the injection valve group 2 is communicated with a gas port of a carbon dioxide tanker 1, the pressure stabilizing valve group 4 is used for conveying low-temperature dioxide to an inerting area, the conveying pipeline 5 is provided, the injection valve group 2 comprises a first carbon dioxide injection switching valve 11, a second carbon dioxide injection switching valve 110, a front pressure gauge 13 of a flow control valve, a front temperature gauge 14 of the flow control valve, a flow control valve 15, a rear pressure gauge 16 of the flow control valve, a rear temperature gauge 17 of the flow control valve, a first safety valve 18, a second safety valve 19 and an exhaust valve 111, the first safety valve 18 and the second safety valve 19 are sequentially arranged along the conveying direction of carbon dioxide, the first safety valve 18 and the second safety valve 19 are simultaneously connected to the conveying pipeline 5 and can simultaneously work, the carbon dioxide flow gauge 12, the front/rear temperature gauge 14 and 17 of the flow control valve, the arrangement of the front/rear pressure gauge 13 and the flow control valve can facilitate the injection process control, the arrangement of the carbon dioxide injection switching valves 11 and 110, the carbon dioxide injection switching valve group 1 is used for adjusting the injection speed of the control system, the safety valve 111, the pressure reducing valve 18 and the pressure reducing valve 23 are used for ensuring that the pressure reducing valve 23 and the pressure reducing valve 23 are sequentially connected to limit of the pressure reducing valve 23, the pressure reducing valve 23 is arranged before the pressure reducing valve 23, the pressure reducing valve 23 is arranged after the pressure reducing valve 23, the pressure reducing valve 23 is arranged before the pressure reducing valve 23, the pressure reducing valve 23 is arranged after the pressure reducing valve 23, the pressure reducing valve 23 is.

The pressure stabilizing valve group can reduce repeated pressurization of a system in the vehicle replacement process and effectively prevent carbon dioxide from forming dry ice in a pipeline to block the pipeline in the injection process; the pressure stabilizing valve group comprises a pressure stabilizing valve 33, a front pressure stabilizing valve cut-off valve 32 arranged in front of the pressure stabilizing valve 33, a front pressure stabilizing valve temperature gauge 31 arranged in front of the front pressure stabilizing valve cut-off valve 32, a rear pressure stabilizing valve cut-off valve 34 and a rear pressure stabilizing valve temperature gauge 35 which are sequentially arranged behind the pressure stabilizing valve 33, a second parallel pipeline which is respectively connected with an inlet of the front pressure stabilizing valve cut-off valve 32 and an outlet of the rear pressure stabilizing valve cut-off valve 34, a front pressure stabilizing valve gauge 36, a third guide shower valve 39, a second bypass valve 37, a fourth guide shower valve 40 and a rear pressure stabilizing valve pressure gauge 38 which are sequentially arranged on the second parallel pipeline, wherein the value of the rear pressure stabilizing valve pressure gauge 38 is 0.8-1.0 MPa, and the indication number of the rear pressure stabilizing valve temperature gauge 35 is-20; the arrangement of the pressure maintaining valve front/back thermometers 31 and 35 and the pressure maintaining valve front/back pressure gauges 36 and 38 is convenient for observing and adjusting gas inlet and outlet parameters. The inerting area is a roadway closed area 8 enclosed by a closed wall 7 and a mine, a discharge pipeline communicated with an outlet of the pressure stabilizing valve group 4 is arranged in the inerting area, the outer part of the discharge pipeline closed wall 7 extends into the closed wall 7, a closed inner valve 9 is arranged on the discharge pipeline in the closed wall 7, and the closed inner valve 9 is a valve front type opening self-operated regulating valve for preventing the closed inner pipeline and the discharge pipeline from forming dry ice; the carbon dioxide inlet and outlet are operated in a double-loop mode, a branch pipeline is additionally arranged on the discharge pipeline, the outer portion of a self-closing wall 7 of the branch pipeline extends into the self-closing wall 7, a front closing valve 6 is arranged on the branch pipeline, the front closing valve 6 is located outside the self-closing wall 7, and the front closing valve 6 is a one-way valve. Furthermore, the discharge pipeline after the front valve 6 and the inner valve 9 are closed does not need to be provided with pipe fittings which obstruct the gas flow, such as elbows, reducing pipes and the like, and the length of the discharge pipeline after the valves is less than 10 times of the diameter of the pipeline. In order to optimize the distribution of carbon dioxide airflow in a sealed area and ensure that dry ice formed in the discharge process can be sublimated quickly, the distance between a discharge pipeline and a bottom plate is more than 0.8m, the carbon dioxide closing and entering adopts double-loop operation, and the double-system closing and entering can carry out secondary adjustment on the distribution of the carbon dioxide airflow in the sealed area and improve the reliability of system operation to the maximum extent.

The injection valve group is arranged above a mine, the pressure reducing valve group and the pressure stabilizing valve group are positioned below the mine, and the pressure stabilizing valve group is close to the inerting area.

Further, the pressure reducing valve and the pressure stabilizing valve are both valve rear type pressure-closing self-operated regulating valves.

Technical parameters and requirements of coal mine liquid carbon dioxide direct injection system

(1) Inerting index: the oxygen content in the inerting zone is less than or equal to 5 percent

(2) Injection speed: and (3) at the initial stage of injection: 1000 to 2000NM³/H (2～4T/H)

After the oxygen content is less than or equal to 5 percent: determined according to the change of oxygen and carbon monoxide content

(3) Injection temperature (carbon dioxide into the wall): between minus 20 ℃ and minus 50 DEG C

(4) Injection pressure (highest): ≦ 4MPa

(5) An injection process: direct injection of liquid carbon dioxide

(6) And (3) the quality standard of liquid carbon dioxide is as follows: meets the GB/T6052-2011 standard requirement

The direct injection process of the liquid carbon dioxide in the coal mine comprises the steps of arranging a carbon dioxide tank car 1 in a relatively open and flat area above a mine, conveying the liquid carbon dioxide to a pressure reducing valve group 3 below the mine through an injection valve group 2, reducing the pressure of the carbon dioxide to 1.6-1.8 MPa, conveying the carbon dioxide to a pressure stabilizing valve group 4 in front of a closed wall, enabling the carbon dioxide to enter an inerting area in a state of pressure of 0.8-1.0 MPa and temperature of-20 to-40 ℃, and forming low-temperature air flow containing dry ice for inerting and cooling after throttling through a closed inner valve in the inerting area.

The liquid carbon dioxide injection operation specifically comprises the following steps:

(1) preparation work

Flattening the carbon dioxide injection site, removing peripheral sundries and ensuring convenient and safe access of carbon dioxide transport vehicles with the length of about 17 meters;

secondly, according to the requirements of the scheme, the arrangement of injection vehicles and the connection of temporary pipelines and pipe fittings of the field pipeline are carried out, the valve position of the closed inner flow limiting valve is set, and the connection mode is confirmed to be safe and reliable;

thirdly, injecting field illumination and vehicle loading and unloading power supply according to the requirement and confirming the safety and the good use;

fourthly, 380V and 10KW power supplies and illumination are arranged on the injection site;

preparing tools and labor protection products required by the injection process;

(2) air tightness test

Closing all valves of an injection system, and closing an inner valve to set pressure of 0.8-1.0 MPa;

opening front and rear cut-off valves of a pressure reducing valve of a system pressure reducing valve bank and a front cut-off valve of a pressure maintaining valve of a pressure stabilizing valve bank;

thirdly, butting a gas phase port of the carbon dioxide tank car with a carbon dioxide injection valve group, opening a gas phase valve of the tank car and a switching valve of the carbon dioxide injection valve group to pressurize the system to 1MPa, and stopping pressurizing for 5 minutes to carry out system inspection;

fourthly, after confirming that the system has no leakage point, continuing pressurizing until the pressure of the system is balanced with the pressure of the vehicle, closing a switching valve of a carbon dioxide injection valve group, and stopping pressurizing for 30 minutes to check a system pipeline and a pipe fitting;

after checking and confirming that the system has no external leakage point, the airtight test is finished, the carbon dioxide tank car gas phase valve is closed, the carbon dioxide injection valve group switching valve is closed, and the system is decompressed to normal pressure through the carbon dioxide tank car gas phase decompression valve;

(3) inerting operation

Firstly, connecting a carbon dioxide tank car liquid phase interface with a carbon dioxide injection valve bank switching valve, opening the carbon dioxide injection valve bank switching valve, exhausting air in a hose through a tank car liquid phase pressure relief valve, and equalizing the pressure of a system and a vehicle to be balanced;

secondly, opening a pressure retaining valve of the pressure stabilizing valve bank and then cutting off the valve, slowly opening and closing a front valve to cool the system, and paying attention to the changes of a pressure gauge and a thermometer of the pressure stabilizing valve bank and the running condition of a carbon dioxide conveying pipeline;

thirdly, adjusting the pressure of the set pressure reducing valve group to be 1.6-1.8 MPa, and adjusting the pressure of the set pressure maintaining valve group to be 0.8-1.0 MPa;

fourthly, controlling the cooling speed of the pipeline by adjusting the opening of the front valve, and controlling the cooling speed of the pipeline to be less than 5 ℃/min;

when the carbon dioxide liquid conveying pipeline is cooled to-20 ℃ (the pipeline is frosted), adjusting the inlet closed flow, and controlling the inlet closed temperature of the carbon dioxide to be-20 to-50 ℃ to maintain the stable operation of the system;

(4) operation maintenance

Firstly, in order to ensure that the mine inerting work is continuously carried out, an operator needs to contact with a transport vehicle in time to ensure that the liquid of a liquid injection vehicle is sufficient;

after the liquid carbon dioxide injection tank car enters a low liquid level, liquid can be supplemented to the injection vehicle through other carbon dioxide tank cars, if liquid supplementing conditions are not available, the empty and heavy vehicles are alternately replaced, and the alternate replacement is performed in a mode that the empty vehicles are withdrawn after the empty vehicles are supplied with liquid after the heavy vehicles are used for supplying liquid;

checking the running flow, pressure, temperature and temperature of the inerting system once per hour, and recording;

fourthly, checking the carbon dioxide conveying pipeline once per hour, and recording;

the liquid phase valve of the carbon dioxide tank car and the switching valve of the injection valve set are closed immediately after the abnormal phenomena such as leakage and rupture of the infusion pipeline are detected, and the system is stoppedFeeding liquid in the system;

sixthly, opening a liquid phase pressure relief valve of the carbon dioxide tank car to relieve the system pressure to normal pressure, and putting the system into operation again after the system is qualified;

(5) system shut down

Closing a liquid phase valve of a carbon dioxide tank car, closing a switching valve of an injection valve group, and stopping injecting liquid carbon dioxide into the system;

opening a carbon dioxide tank car liquid phase pressure relief valve to relieve pressure of the connecting pipe, and dismantling a tank car liquid phase connecting port;

thirdly, stopping the operation for a long time, connecting a gas phase port of the tank car to a system inlet, opening a gas phase port valve of the carbon dioxide tank car, opening a switching valve of an injection valve group, and sending liquid in the pipeline into a closed area by using air pressure;

closing a tank car gas phase valve after the pressure of the carbon dioxide tank car and the system is balanced, opening a pressure stabilizing valve group bypass valve, feeding residual gas in the system into a closed state, closing a front cut-off valve, and closing an inlet and a closed port;

opening a tank car gas phase pressure relief valve, closing an injection valve set switching valve after the pressure relief of residual gas in a pipeline is finished, and dismantling a tank car and system connecting pipe;

(6) accident handling

System power failure

Firstly, turning on an emergency power supply of a vehicle to keep on-site illumination normal;

secondly, after power failure, the carbon dioxide injection vehicle cannot perform liquid supplementing operation, and at the moment, the carbon dioxide injection uses an injection valve group switching valve to perform alternate replacement operation of empty and heavy vehicles;

burst of delivery pipe

Firstly, a pressure reducing valve group or a vehicle liquid phase valve is selected to be closed according to the burst position of a conveying pipeline, and liquid supply to a system is stopped;

opening a bypass valve of the pressure stabilizing valve group, and completely delivering carbon dioxide liquid and gas in the pipeline into a sealed area;

if the bypass valve of the pressure stabilizing valve group cannot be opened in time, a liquid (gas) phase pressure release valve of the injected vehicle is directly opened, and the system residual gas is discharged;

closing the front cut-off valve and the pressure stabilizing valve set bypass valve, closing the injection valve set switching valve and evacuating personnel to a safe area.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.