Mine ventilation air methane waste heat absorption system
By embedding a CO2 circulating pipeline and an NH3-CO2 cascade module into the underground roadway of a coal mine, the shortcomings of waste heat recovery and utilization have been solved, and the efficient conversion of low-grade heat energy into high-grade heat energy has been achieved, reducing energy consumption and carbon emissions.
Patent Information
- Application Number
- CN202511084035.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-04
- Publication Date
- 2025-11-18
AI Technical Summary
There is a lack of research on the recovery and utilization of waste heat from exhaust wind in existing technologies. In particular, there is a lack of specific application schemes for the absorption, long-distance transmission and improvement of heat energy quality in exhaust wind, which leads to high energy consumption and large pollution emissions.
A mine exhaust air waste heat absorption system is adopted, which utilizes a CO2 circulation pipeline embedded in the sidewall of the underground roadway of the coal mine. Combined with a gas-liquid separator and an NH3-CO2 cascade assembly, the system achieves transcritical state transmission and efficient conversion of exhaust air heat energy through CO2 and NH3 media. A superhydrophobic nanocomposite coating and spray assembly are used to prevent clogging, thereby achieving efficient absorption of low-grade heat energy and preparation of high-grade heat energy in the exhaust air.
It significantly reduced energy consumption for coal mine wellhead frost prevention and plant area heating, reduced carbon emissions, achieved efficient utilization of waste heat, and reduced the frequency of coal-fired boiler use.
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Figure CN120970352A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of waste air waste heat utilization, and particularly relates to a mine waste air waste heat absorption system. BACKGROUND
[0002] Waste air refers to air after passing through a mine working face or other areas. In a mine, due to the activities of mine workers and the operation of mechanical equipment, a large amount of oxygen is consumed and carbon dioxide and other pollutants are generated. Such oxygen-poor air mixed with harmful gases and dust pollutants does not meet the requirements of air for underground workers to breathe and is called waste air.
[0003] Coal mine shaft freezing usually needs to be assisted by electric heating means, and high-grade heat energy is prepared for bath water supply, heating, etc. in the plant area, which usually needs to rely on coal-fired boilers, resulting in a large amount of energy consumption and carbon emissions, which does not meet the environmental protection concept of green mine construction. In the existing design, the waste air waste heat absorption system, the bath water supply system, and the high-grade heat energy system for preparing high-grade heat energy for heating in the plant area are all independent systems. The waste air contains a large amount of low-grade heat energy, generally at 15-25℃, and if it can be utilized for coal mine shaft freezing, heating of bath hot water supply in the plant area, and preparation of high-grade heat energy for heating in the plant area to form a unified system, the meaningless consumption of energy and the generation of pollution can be greatly reduced. However, the current design still lacks research on the recycling of waste air waste heat, especially the absorption and gathering of heat energy contained in waste air, long-distance transmission, and the upgrading of heat energy grade (to provide heating with different temperature requirements), which lacks specific and implementable application schemes, resulting in low economic benefits in actual application.
[0004] Therefore, it is urgent to provide a mine waste air waste heat absorption system that effectively absorbs and utilizes waste air waste heat to overcome the above problems.
[0005] Therefore, the present application is proposed. SUMMARY
[0006] The technical problem to be solved by the present application is to overcome the deficiency that the prior art cannot effectively absorb and utilize waste air waste heat, and the purpose is to provide a mine waste air waste heat absorption system that effectively absorbs and utilizes waste air waste heat.
[0007] To solve the above technical problems, the basic idea of the technical solution adopted by the present application is as follows: a mine waste air waste heat absorption system, comprising: A first heat exchange component, the first heat exchange component comprising a first pipe and a second pipe; mine waste air flows in the first pipe; A CO2 circulation conveying pipeline, the CO2 circulation conveying pipeline being in communication with both ends of the second pipe; the CO2 circulation conveying pipeline is partially arranged in the side wall of the coal mine underground tunnel; a gas-liquid separator, which is in communication with one end of the CO2 circulation pipeline away from the first heat exchange assembly; a second heat exchange assembly, which comprises a third pipeline and a fourth pipeline; an inlet end of the third pipeline is in communication with a gas outlet end of the gas-liquid separator; the fourth pipeline circulates a heat exchange medium; an outlet end of the fourth pipeline is in communication with a first demand end; an NH3-CO2 cascade assembly, which comprises a fifth pipeline, a sixth pipeline and a seventh pipeline; the sixth pipeline circulates an NH3 medium; the seventh pipeline circulates a heat exchange medium; the seventh pipeline is in communication with a second demand end; an inlet end of the fifth pipeline is connected to an outlet end of the second heat exchange assembly; a first expansion valve, which is arranged between an outlet end of the fifth pipeline of the NH3-CO2 cascade assembly and an inlet end of the second pipeline of the first heat exchange assembly; one end of the first expansion valve is in communication with the outlet end of the fifth pipeline of the NH3-CO2 cascade assembly, and the other end of the first expansion valve is in communication with the inlet end of the second pipeline of the first heat exchange assembly; wherein the fourth pipeline of the second heat exchange assembly outputs the heat exchange medium at a temperature of 40-55℃; and the seventh pipeline of the NH3-CO2 cascade assembly outputs the heat exchange medium at a temperature of 80-95℃.
[0008] According to an embodiment of the present application, a super-hydrophobic nano-composite coating is arranged on the inner wall of the first pipeline.
[0009] According to an embodiment of the present application, a filter screen is arranged at the inlet end of the first pipeline.
[0010] According to an embodiment of the present application, a spraying assembly is arranged in the first pipeline. The spraying assembly sprays the filter screen to prevent accumulation of sundries.
[0011] According to an embodiment of the present application, the heat exchange medium is water or air.
[0012] According to an embodiment of the present application, the axial length of the CO2 circulation pipeline is greater than 2km.
[0013] According to an embodiment of the present application, the first demand end comprises a gas outlet for anti-freezing and de-icing of a wellhead. The heat exchange medium output by the second heat exchange assembly can be used for anti-freezing and de-icing of the wellhead.
[0014] According to an embodiment of the present application, the second demand end comprises an output outlet for conveying the heat exchange medium. The heat exchange working medium output by the NH3-CO2 cascade assembly can be used for heating and steam preparation process.
[0015] According to an embodiment of the present application, further comprising: The first pressurizing device is arranged between the gas outlet end of the gas-liquid separator and the inlet end of the third through pipe of the second heat exchange assembly. The second pressurizing device is arranged on the sixth through pipe.
[0016] According to an embodiment of the present application, the sixth through pipe is further provided with a second expansion valve.
[0017] Compared with the prior art, the present application has the following beneficial effects: in the present application, the mine ventilation air is flowed in the first through pipe and exchanges heat with the CO2 in the second through pipe, and the CO2 circulating pipeline is partially embedded in the sidewall of the underground tunnel of the coal mine, and the underground low-temperature environment is utilized, and based on the characteristics of the cross-critical state, high density, low viscosity, high flow rate and low heat loss, the heat absorption and heat preservation are further improved in the circulation process, and the heat exchange efficiency is improved. The CO2 after being heated by the first heat exchange assembly enters the gas-liquid separator for gas-liquid separation, and the separated gas enters the second heat exchange assembly to exchange heat with the heat exchange working medium in the fourth through pipe again, so that the temperature of the heat exchange working medium reaches 40-55 DEG C, which can be directly used for coal mine wellhead anti-freezing, replacing the traditional electric heating auxiliary means, greatly reducing the power consumption; meeting the demand for heating the bath water supplied to the plant area; the separated gas is subsequently treated by the NH3-CO2 cascade assembly, and based on the phase change high-temperature heat release of NH3, the temperature of the heat exchange working medium in the seventh through pipe is increased to 80-95 DEG C, meeting the demand for preparing high-grade heat energy such as heating in the plant area, thereby reducing the use and operation of the coal-fired boiler, and reducing the energy consumption and carbon emission.
[0018] The specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS
[0019] The accompanying drawings are part of the present application and serve to provide a further understanding of the present application, and the schematic embodiments of the present application and the description thereof serve to explain the present application, but do not constitute an improper limitation on the present application. Obviously, the accompanying drawings in the following description are only some embodiments, and other drawings can be obtained by those skilled in the art without creative labor. In the drawings: Figure 1 It is a structural schematic block diagram of a mine ventilation air waste heat absorption system in the embodiments of the present application.
[0020] Main element description in the figure: 1, first heat exchange assembly; 11, first through pipe; 12, second through pipe; 2, CO2 circulation conveying pipeline; 3, gas-liquid separator; 4, second heat exchange assembly; 41, third through pipe; 42, fourth through pipe; 5, NH3-CO2 cascade assembly; 51, fifth through pipe; 52, sixth through pipe; 53, seventh through pipe; 6, first expansion valve; 7, first pressurizing device; 8, second pressurizing device; 9, second expansion valve.
[0021] It should be noted that these drawings and textual descriptions are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION
[0022] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments will be described clearly and completely below in conjunction with the drawings of the embodiments of the present application. The following embodiments are used to illustrate the present application, but not to limit the scope of the present application.
[0023] In the description of the present application, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.
[0024] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.
[0025] As shown in Figure 1 A mine ventilation air methane waste heat absorption system according to the present application comprises: A first heat exchange assembly 1, which comprises a first through pipe 11 and a second through pipe 12; mine ventilation air methane flows through the first through pipe 11, and CO2 medium flowing through the second through pipe 12 absorbs the heat of the mine ventilation air methane flowing through the first through pipe 11; A CO2 circulating pipeline 2, which is communicated with both ends of the second pipeline 12, and through which the CO2 medium absorbing the heat of the mine ventilation air is flowed into the subsequent pipeline via the first pipeline 11; A gas-liquid separator 3, which is communicated with one end of the CO2 circulating pipeline 2 away from the first heat exchange assembly 1; A second heat exchange assembly 4, which comprises a third pipeline 41 and a fourth pipeline 42; the inlet end of the third pipeline 41 is communicated with the gas outlet end of the gas-liquid separator 3; the fourth pipeline 42 is communicated with a heat exchange medium, and the heat exchange medium in the fourth pipeline 42 absorbs the heat of the gaseous CO2 medium separated by the gas-liquid separator 3; the output end of the fourth pipeline 42 is communicated with a first demand end; An NH3-CO2 cascade assembly 5, which comprises a fifth pipeline 51, a sixth pipeline 52 and a seventh pipeline 53; the sixth pipeline 52 is communicated with an NH3 medium, and the seventh pipeline 53 is communicated with a heat exchange medium; the output end of the seventh pipeline 53 is communicated with a second demand end; the inlet end of the fifth pipeline 51 is connected with the output end of the second heat exchange assembly 4; A first expansion valve 6, which is arranged between the outlet end of the fifth pipeline 51 of the NH3-CO2 cascade assembly 5 and the inlet end of the second pipeline 12 of the first heat exchange assembly 1; one end of the first expansion valve 6 is communicated with the outlet end of the fifth pipeline 51 of the NH3-CO2 cascade assembly 5, and the other end of the first expansion valve 6 is communicated with the inlet end of the second pipeline 12 of the first heat exchange assembly 1; Wherein, the fourth pipeline 42 of the second heat exchange assembly 4 outputs the heat exchange medium with a temperature of 40-55℃; the seventh pipeline 53 of the NH3-CO2 cascade assembly 5 outputs the heat exchange medium with a temperature of 80-95℃.
[0026] In the mine ventilation air waste heat absorption system provided by the application, the mine ventilation air flows in the first through pipe and exchanges heat with CO2 in the second through pipe, and the CO2 circulating conveying pipeline is partially embedded in the sidewall of the underground tunnel of the coal mine, so that the relatively stable low-temperature environment of the underground environment is utilized to further absorb heat and keep warm of the CO2 in the circulating process, and the heat exchange efficiency is improved. The CO2 that is heated by the first heat exchange assembly enters the gas-liquid separator for gas-liquid separation, the separated gas enters the second heat exchange assembly and exchanges heat with the heat exchange medium in the fourth through pipe again, so that the temperature of the heat exchange medium reaches 40-55 DEG C, which can be directly used for coal mine mouth anti-freezing, replacing the traditional electric heating auxiliary means, greatly reducing the power consumption; meeting the demand for heating the bath water in the factory area; the separated gas is subsequently treated by the NH3-CO2 cascade assembly, the fifth through pipe, the sixth through pipe and the seventh through pipe are matched, the temperature of the heat exchange medium in the seventh through pipe is increased to 80-95 DEG C, meeting the demand for preparing high-grade heat energy such as factory area heating, so that the use and operation of the coal-fired boiler are reduced, and the energy consumption and carbon emission are reduced. In the application, CO2 is used as an intermediate medium, the good heat transfer performance and phase change characteristics of CO2 are utilized, the low-grade heat energy of 15-25 DEG C in the ventilation air is efficiently absorbed, and the NH3-CO2 cascade assembly is utilized to realize the conversion of heat energy from low-grade to high-grade, so that the application scene of the ventilation air waste heat is widened.
[0027] In a specific embodiment of the embodiment (not shown in the figure), the part of the second through pipe 12 that exchanges heat with the first through pipe 11 is in a spiral shape and is arranged around the outer periphery of the first through pipe 11. Through the arrangement, the heat exchange time and heat exchange path ( / heat exchange area) of the CO2 medium in the second through pipe 12 and the mine ventilation air in the first through pipe 11 are increased, and effective heat exchange is realized.
[0028] In a specific embodiment of the embodiment, the gas-liquid separator 3 includes a medium inlet, a liquid outlet and a gas outlet. The end of the CO2 circulating conveying pipeline 2 that is far away from the first heat exchange assembly 1 is connected to the gas-liquid separator 3 through the medium inlet. The inlet of the third through pipe 41 is connected to the gas outlet of the gas-liquid separator 3.
[0029] The CO2 medium in the CO2 circulating pipeline sequentially passes through the second through pipe 12 of the first heat exchange assembly 1, the gas-liquid separator 3, the third through pipe 41 of the second heat exchange assembly 4 and the fifth through pipe 51 of the NH3-CO2 cascade assembly 5, and finally flows back to the second through pipe 12 of the first heat exchange assembly 1.
[0030] In a specific embodiment of the present embodiment (not shown in the figure), the part of the fourth pipe 42 that exchanges heat with the third pipe 41 is in a spiral shape and is arranged around the outer periphery of the third pipe 41; Through the arrangement, the heat exchange time and heat exchange path of the heat exchange working medium in the fourth pipe 42 and the CO2 medium in the third pipe 41 are increased, and effective heat exchange is achieved.
[0031] In a specific embodiment of the present embodiment, the liquid outlet is in communication with the end of the second pipe 12 of the first heat exchange assembly 1 away from the gas-liquid separator 3.
[0032] In a specific embodiment of the present embodiment, a super-hydrophobic nano-composite coating is arranged on the inner wall of the first pipe 11.
[0033] In a specific embodiment of the present embodiment, a filter screen is arranged at the inlet end of the first pipe 11 to prevent dust carried by the mine ventilation air to flow in the first pipe 11.
[0034] In a specific embodiment of the present embodiment, a spraying assembly is arranged in the first pipe 11. The spraying assembly sprays the filter screen to prevent sundries from accumulating on the filter screen and causing hindrance to the actual flow of the mine ventilation air.
[0035] In the present application, the super-hydrophobic nano-composite coating, the filter screen and the spraying assembly are arranged to filter and remove dust from the mine ventilation air injected into the first pipe 11, thereby avoiding the problem of blockage of the first pipe 11 of the first heat exchange assembly 1 and having a positive significance for the guarantee of heat exchange efficiency.
[0036] In a specific embodiment of the present embodiment, the heat exchange working medium is water or air, and the type of heat exchange working medium depends on the demand for gas or water at the demand end.
[0037] In a specific embodiment of the present embodiment, the axial length of the CO2 circulating conveying pipeline 2 is greater than 2km. The CO2 circulating conveying pipeline 2 is partially arranged in the side wall of the underground tunnel of the coal mine.
[0038] In the present application, the CO2 circulating conveying pipeline 2 is arranged in the side wall of the underground tunnel of the coal mine to form a kilometer-level linear heat exchange interface. Through dynamic coupling of the phase change working medium and the heat field of the surrounding rock, the carbon dioxide continuously absorbs the heat dissipation of the surrounding rock and the waste heat of the ventilation air in the long process transportation, and finally reaches a pseudo-critical state thermodynamic state, thereby realizing the step-by-step enrichment of low-grade heat energy. Meanwhile, the arrangement of the CO2 circulating conveying pipeline fully utilizes the double advantages of the natural working medium (CO2 medium): At the thermodynamic level, the wide phase transition temperature range feature makes the evaporation section self-adaptable to the 15-25℃ waste air temperature fluctuation, and realizes the synchronous and efficient extraction of sensible heat and latent heat. At the fluid dynamics level: the supercritical state low viscosity feature combined with the self-boosting effect enables the pipeline system to have autonomous siphon conveying capacity, which can reduce the pipe diameter specification by more than 40% compared with the traditional circulating pumping mode, and significantly suppresses the heat dissipation along the way.
[0039] In a specific embodiment of the present embodiment, the first demand end includes wellhead anti-freezing and deicing demand, medium-temperature application demand such as hot water for bathing, etc. The second demand end includes high-temperature application demand such as building heating in a mining area, steam preparation process, etc.
[0040] In a specific embodiment of the present embodiment, the first demand end includes a gas outlet for anti-freezing and deicing of the wellhead. The heat exchange working medium (at this time, air) output by the second heat exchange assembly 4 can be used for anti-freezing and deicing of the wellhead.
[0041] In a specific embodiment of the present embodiment, the first demand end includes a hot water delivery pipeline for bathing. The heat exchange working medium (at this time, water) output by the second heat exchange assembly 4 can be used to supply hot water for bathing.
[0042] In a specific embodiment of the present embodiment, the second demand end includes an output port for delivering the heat exchange working medium. The heat exchange working medium (high-grade heat energy) output by the NH3-CO2 cascade assembly 5 can be used for heating and steam preparation process.
[0043] In a specific embodiment of the present embodiment, the fifth pipe 51 of the NH3-CO2 cascade assembly 5 is in communication with the CO2 circulating delivery pipeline 2. The NH3 medium flowing in the sixth pipe 52 absorbs the heat of the CO2 medium; The heat exchange working medium in the seventh pipe 53 absorbs the heat of the NH3 medium.
[0044] The NH3-CO2 cascade assembly converts low-grade heat energy into high-grade heat energy through the mechanism of double working medium cooperative phase change heat exchange and multi-stage energy coupling. Specifically, based on the principle that CO2 low-temperature phase change can realize efficient heat absorption, after absorbing the waste air heat in the low-temperature zone, CO2 crosses the critical state in the transportation process, has the characteristics of high density, low viscosity, high flow rate, and low heat loss in transportation, and transfers energy to NH3 through phase change; when NH3 releases energy in the high-temperature zone, due to its high critical temperature, the heat can be upgraded to a higher grade, forming a "low-temperature absorption-high-temperature release" grade jump.
[0045] Please see the appendix Figure 1 In one specific embodiment of this invention, the mine exhaust air waste heat absorption system further includes: The first pressurizing device 7 is disposed between the gas outlet end of the gas-liquid separator 3 and the inlet end of the third pipe 41 of the second heat exchange component 4. The second pressurizing device 8 is disposed on the sixth conduit 52.
[0046] In one specific embodiment of this example, a second expansion valve 9 is also provided on the sixth conduit 52.
[0047] In this invention, by setting the second pressurizing device 8 and the second expansion valve 9, the heat absorption and release cycle of NH3 is promoted, ensuring the high efficiency of heat transfer.
[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. The implementation schemes in the above embodiments can also be further combined or replaced. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.
Claims
1. A mine exhaust air waste heat absorption system, characterized in that, include: The first heat exchange component includes a first through pipe and a second through pipe; the mine exhaust air flows through the first through pipe; The CO2 circulation pipeline is connected to both ends of the second pipe; the CO2 medium flowing in the second pipe absorbs the heat of the mine exhaust air flowing in the first pipe; part of the CO2 circulation pipeline is set in the side wall of the underground roadway of the coal mine. The gas-liquid separator is connected to the end of the CO2 circulation pipeline furthest from the first heat exchange component. The second heat exchange component includes a third pipe and a fourth pipe; the inlet end of the third pipe is connected to the gas outlet end of the gas-liquid separator; a heat exchange medium flows in the fourth pipe; the outlet end of the fourth pipe is connected to the first demand end; the heat exchange medium flowing in the fourth pipe absorbs the heat of the CO2 medium flowing in the third pipe. The NH3-CO2 cascade assembly includes a fifth, sixth, and seventh tube. NH3 medium flows through the sixth tube, and a heat exchange medium flows through the seventh tube. The seventh tube is connected to a second demand end. The inlet end of the fifth tube is connected to the outlet end of the second heat exchange assembly. The NH3 medium flowing through the sixth tube absorbs heat from the CO2 medium flowing through the fifth tube; the heat exchange medium in the seventh tube absorbs heat from the NH3 medium. The first expansion valve is located between the outlet end of the fifth pipe of the NH3-CO2 cascade assembly and the inlet end of the second pipe of the first heat exchange assembly; one end of the first expansion valve is connected to the outlet end of the fifth pipe of the NH3-CO2 cascade assembly, and the other end of the first expansion valve is connected to the inlet end of the second pipe of the first heat exchange assembly. The fourth pipe outputs a heat exchange medium with a temperature of 40-55℃; the seventh pipe outputs a heat exchange medium with a temperature of 80-95℃.
2. The mine exhaust air waste heat absorption system according to claim 1, characterized in that, The inner wall of the first conduit is provided with a superhydrophobic nanocomposite coating.
3. The mine exhaust air waste heat absorption system according to claim 2, characterized in that, A filter screen is installed at the inlet end of the first conduit.
4. A mine exhaust air waste heat absorption system according to claim 3, characterized in that, A spray assembly is installed inside the first through pipe; The spray assembly sprays water onto the filter screen to prevent debris from accumulating.
5. A mine exhaust air waste heat absorption system according to claim 1, characterized in that, The heat exchange medium is water or air.
6. A mine exhaust air waste heat absorption system according to claim 5, characterized in that, The axial length of the CO2 circulation pipeline is greater than 2 km.
7. A mine exhaust air waste heat absorption system according to claim 5, characterized in that, The first demand side includes a gas delivery port for antifreezing and de-icing the wellhead; The heat exchange medium output from the second heat exchange component can be used for wellhead antifreeze and de-icing.
8. A mine exhaust air waste heat absorption system according to claim 5, characterized in that, The second demand side includes an output port for conveying the heat exchange medium; The heat exchange medium output by the NH3-CO2 cascade module can be used in heating and steam preparation processes.
9. A mine exhaust air waste heat absorption system according to any one of claims 1-8, characterized in that, Also includes: A first pressurizing device is disposed between the gas outlet end of the gas-liquid separator and the inlet end of the third pipe of the second heat exchange component; The second pressurizing device is installed on the sixth conduit.
10. A mine exhaust air waste heat absorption system according to claim 9, characterized in that, A second expansion valve is also installed on the sixth conduit.