CN109827721B - Experimental platform and method for leakage diffusion and pollutant removal of buried liquid hydrocarbon pipeline - Google Patents
Experimental platform and method for leakage diffusion and pollutant removal of buried liquid hydrocarbon pipeline Download PDFInfo
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Abstract
The invention discloses an experimental platform and a method for leakage diffusion and pollutant removal of a buried liquid hydrocarbon pipeline, wherein the experimental platform comprises a normal-pressure oil tank, a first centrifugal pump, a second centrifugal pump, a third centrifugal pump, a normal-pressure water tank, a pressure-resistant gas tank, an oil-water separator, an air compressor, a pressure-resistant oil tank, a sand box and a pressure-resistant water tank; the sand box comprises a cover plate, a pressing device and a transparent box body, the cover plate is pressed at the upper end of the transparent box body through the pressing device, two sides of the transparent box body are respectively communicated with the oil-water separator and the pressure-resistant water tank, the bottom of the transparent box body is communicated with the pressure-resistant gas tank, and the cover plate is provided with a vent pipe communicated with the inner cavity of the transparent box body. The invention can research the influence of different burial depths on the leakage rate; the influence of the soil pressure at different burial depths on the diffusion rate of the pollutants can be researched; the influence of the underground water level and the underground water flow on the diffusion of pollutants can be researched; the influence of parallel pipelines in the soil on the diffusion of pollutants can be researched; fifthly, the removing effect of the temperature and the flow of the stripping gas on pollutants can be researched.
Description
Technical Field
The invention belongs to the field of petroleum and chemical engineering safety engineering, and particularly relates to a platform and a method for a buried liquid hydrocarbon pipeline leakage diffusion and pollutant removal experiment.
Background
The pipeline transportation has the advantages of large transportation amount, small occupied area, sealing safety, low cost and the like, and is the most main transportation mode of crude oil and finished oil. In the service process of the pipeline, due to factors such as corrosion, third-party damage, natural disasters and the like, the accidents of pipeline breakage and perforation sometimes occur. Since most petroleum pipelines are buried pipelines, after the pipelines are broken, liquid petroleum leaks into the soil from the openings of the broken pipelines and gradually diffuses in the soil. The leakage of the buried petroleum pipeline causes serious environmental pollution, and in addition, the buried petroleum pipeline has the dangerous characteristics of flammability, explosiveness, toxicity and the like, so that the buried petroleum pipeline is very easy to cause serious events such as fire, explosion and the like, and great threat is caused to the safety of lives and properties.
At present, research on leakage diffusion of liquid pipelines is mainly based on derivation of basic equations of hydrodynamics and seepage mechanics, and the oil leakage rate and the diffusion range are researched.
In terms of diffusion range, research is currently mainly carried out by deriving a basic equation set of seepage mechanics to carry out numerical experiments and physical experiments: in the aspect of numerical experiments, three-dimensional seepage is mainly simplified into two-dimensional steady-state or unsteady-state seepage, the diffusion process of petroleum in soil is simulated by using relevant fluid mechanics software, the distribution conditions of the characteristics of the petroleum in the soil, such as a pressure field, a velocity field, a temperature field and the like, are analyzed, and the influences of the diameter, the position, the soil water content, the permeability, the saturation, the temperature, the surface temperature and the like of a leakage orifice on the diffusion range and the relevant characteristics are researched. Because the basic seepage mechanics equation is simplified more when a mathematical model is established and the limitation of related fluid mechanics software is caused, the simulation result of a numerical experiment has larger difference with the actual diffusion condition, and the method is mainly used for qualitative research of the leakage diffusion process. In the aspect of physical experiments, the influences of petroleum properties, soil types, water contents and soil uniformity on a diffusion range and relevant characteristics are mainly analyzed through the research of soil column experiments, two-dimensional sand box experiments and two-dimensional sand tank experiments. However, many factors affecting the leakage diffusion characteristic, such as the buried depth of the pipeline, the groundwater level, the groundwater flow speed and the parallel pipeline in the soil all affect the leakage or diffusion characteristic, and the related research at present is extremely deficient.
In addition, at present, the research on petroleum leakage and diffusion in soil is mostly focused on the research on leakage rate and diffusion range, the quantitative research on experiments related to removal of pollutants after leakage is less, along with the continuous attention of the country on environmental protection, the research on related technologies for processing petroleum pollutants in soil is necessarily promoted, and a related experimental device is necessary to be designed to carry out research on removal of pollutants in soil.
Disclosure of Invention
The invention mainly overcomes the defects in the prior art and provides an experimental platform and method for buried liquid hydrocarbon pipeline leakage diffusion and pollutant removal.
The technical scheme provided by the invention for solving the technical problems is as follows: an experimental platform for leakage diffusion and pollutant removal of a buried liquid hydrocarbon pipeline comprises a normal-pressure oil tank, a first centrifugal pump, a second centrifugal pump, a third centrifugal pump, a normal-pressure water tank, a pressure-resistant gas tank, an oil-water separator, an air compressor, a pressure-resistant oil tank, a sand box and a pressure-resistant water tank;
the bottom of the normal-pressure oil tank is communicated with the upper part of the pressure-resistant oil tank through a first centrifugal pump, and the side surface of the upper part of the pressure-resistant oil tank is communicated with the oil-water separator through a second centrifugal pump;
the sand box comprises a cover plate, a pressing device and a transparent box body, wherein the cover plate is pressed at the upper end of the transparent box body through the pressing device, two sides of the transparent box body are respectively communicated with an oil-water separator and a pressure-resistant water tank, the bottom of the transparent box body is communicated with the pressure-resistant gas tank, the cover plate is provided with a vent pipe communicated with an inner cavity of the transparent box body, a flange, a leakage unit, a parallel pipeline, a plurality of pressure sensors and temperature sensors are arranged in the transparent box body, the leakage unit is communicated with the bottom of the pressure-resistant oil tank through the flange, and an infrared thermal imager is arranged beside the transparent;
the upper part of the pressure-resistant water tank is communicated with the bottom of the normal-pressure water tank through a third centrifugal pump, and the upper part of the pressure-resistant gas tank is communicated with the air compressor.
The further technical scheme is that liquid level meters are arranged on the normal-pressure oil tank, the normal-pressure water tank, the pressure-resistant oil tank and the pressure-resistant water tank.
The further technical scheme is that temperature control devices are arranged in the pressure-resistant gas tank and the pressure-resistant oil tank.
The further technical scheme is that a sewage pool is arranged below the oil-water separator.
The further technical scheme is that a thermometer is arranged between the flange and the pressure-resistant oil tank; pressure gauges are arranged between the first centrifugal pump and the pressure-resistant oil tank, between the flange and the pressure-resistant oil tank, between the pressure-resistant water tank and the third centrifugal pump, and between the pressure-resistant gas tank and the air compressor, and flow meters are arranged between the flange and the pressure-resistant oil tank, between the transparent box body and the pressure-resistant gas tank, and between the transparent box body and the pressure-resistant water tank.
The further technical scheme is that the experimental platform further comprises a PCL control cabinet and a central control room which are electrically connected with each other, and the pressure gauge, the flow meter, the thermometer, the temperature sensor, the infrared thermal imager and the air compressor are all electrically connected with the PCL control cabinet.
The technical scheme is that the pressing device comprises an upper pressing plate, a lower pressing plate, a force applying rod and a sleeve, the upper pressing plate is connected with the lower pressing plate through the sleeve, a metal plate with a threaded hole is welded outside the sleeve, the force applying rod with threads at the upper end penetrates through the two threaded holes, a baffle is arranged on the lower portion of the force applying rod, and the upper pressing plate and the lower pressing plate are driven to move up and down along the direction of the sleeve through the rotating force applying rod to apply pressure to the surface of soil.
An experimental method for leakage diffusion and pollutant removal of a buried liquid hydrocarbon pipeline comprises the following steps:
(1) determining basic parameters, namely determining the soil density and the internal friction angle according to the soil type for experiments, and measuring the area of a leakage orifice and the wall thickness of a damaged pipeline;
(2) burying sand boxes in a layered mode, namely burying a temperature sensor, a parallel pipeline, a pressure sensor and a damaged pipeline into soil, recording the positions of the pipeline and each sensor in the soil, wherein the burial depth of the pressure sensor is the same as that of a leakage hole, and covering a cover plate when the soil is nearly full;
(3) according to the required equivalent burial depth, applying pressure to the surface of the soil through a pressing device, and simultaneously recording the pressure value of a pressure sensor until the pressure value of the pressure sensor meets the pressure value of the equivalent burial depth;
(4) pumping petroleum into a pressure-resistant oil tank, maintaining a certain pressure, opening a switch of a temperature control device, heating the petroleum to the required temperature, pumping clear water into a pressure-resistant water tank, maintaining a certain pressure, pressurizing air by an air compressor, introducing the air into the pressure-resistant air tank, maintaining a certain pressure, opening the switch of the temperature control device, and heating the compressed air to the required temperature;
(5) opening an outlet valve of the pressure-resistant water tank, controlling the water level and water flow in the sand tank to be required values, and simulating the flow of underground water level and underground water; opening an outlet valve of the pressure-resistant oil tank, introducing oil into the leakage unit, recording the leakage flow through a first flowmeter, recording the internal pressure of a leakage pipe section through a pressure gauge, and then, oil leaks into soil; recording the temperatures of different positions and different moments of the soil through a temperature sensor; opening an infrared thermal imager, and recording the temperature fields of the soil surface at different moments; when oil and water are diffused to the bottom of the sand box, an oil-water mixture enters the oil-water separator through the outlet stop valve on one side of the sand box, after being separated by the separator, oil on the upper part of the separator is pumped back to the pressure-resistant oil tank through the centrifugal pump, and water on the lower part flows into the sewage pool through the twentieth stop valve;
(6) after the leakage diffusion experiment is finished, closing outlet valves of the pressure-resistant water tank and the pressure-resistant oil tank, weighing the mass of the whole sand box at the moment, opening the outlet valve of the pressure-resistant air tank, enabling air for stripping to enter soil from the bottom of the sand box, enabling stripping air flowing through the soil to enter an emptying system, emptying the emptying system, and discharging mixed air into the air; weighing the sand box once every a period of time;
(7) calculating to obtain the flow coefficient of the leakage hole; the pressing device is used for changing the equivalent burial depth of the pipeline, so that the influence rule of different burial depths on the leakage rate and the diffusion range can be researched; the influence rule of different water levels and groundwater flow on diffusion can be researched by controlling the opening of the outlet valve of the pressure-resistant water tank and the opening of the outlet valve on the side surface of the sand box; the influence rule of the parallel pipeline on the petroleum diffusion range can be researched by changing the relative position between the parallel pipeline and the damaged pipeline; the effect of removing petroleum pollutants by different stripping gas flow and temperature can be researched by changing the opening of an outlet valve of the pressure-resistant gas tank and the stripping gas temperature.
The invention has the following advantages: the influence of different burial depths on the leakage rate can be researched; the influence of the soil pressure at different burial depths on the diffusion rate of the pollutants can be researched; the influence of the underground water level and the underground water flow on the diffusion of pollutants can be researched; the influence of parallel pipelines in the soil on the diffusion of pollutants can be researched; fifthly, the removing effect of the temperature and the flow of the stripping gas on pollutants can be researched.
Drawings
FIG. 1 is a schematic diagram of an experimental apparatus according to the present invention;
fig. 2 is a schematic structural diagram of the pressing device in the embodiment.
Shown in the figure: 1-normal-pressure oil tank, 2-liquid level meter, 3 a-first stop valve, 3 b-second stop valve, 3 c-third stop valve, 3 d-fourth stop valve, 3 e-fifth stop valve, 3 f-sixth stop valve, 3 g-seventh stop valve, 3 h-eighth stop valve, 3 i-ninth stop valve, 3 j-tenth stop valve, 3 k-eleventh stop valve, 3L-twelfth stop valve, 3 m-thirteenth stop valve, 3 n-fourteenth stop valve, 3 o-fifteenth stop valve, 3 p-sixteenth stop valve, 3 q-seventeenth stop valve, 3 r-eighteenth stop valve, 3 s-nineteenth stop valve, 3 t-twentieth stop valve, 3 u-twenty-first stop valve, 3 v-twenty-second stop valve, 4 a-first centrifugal pump, 4 b-second centrifugal pump, 4 c-third centrifugal pump, 5 a-5 d-pressure gauge, 6-pipeline, 7 a-first flowmeter, 7 b-second flowmeter, 7 c-third flowmeter, 8-thermometer, 9-flange, 10-leakage unit, 11 a-11 b-pressure sensor, 12-temperature sensor, 13-parallel pipeline, 14-cover plate, 15 a-15 b-compacting device, 16-transparent sand box, 17-infrared thermal imager, 18-normal pressure water tank, 19-pressure-resistant gas tank, 20-oil-water separator, 21-PLC control cabinet, 22-central control room, 23-air compressor, 24-emptying vertical pipe, 25-temperature control device, 26-pressure-resistant oil tank, 27-pressure-resistant water tank and 28-sewage pool.
Detailed Description
The present invention will be further described with reference to the following examples and the accompanying drawings.
As shown in fig. 1: the experimental platform for leakage diffusion and pollutant removal of the buried liquid hydrocarbon pipeline comprises a normal-pressure oil tank 1, a first centrifugal pump 4a, a second centrifugal pump 4b, a third centrifugal pump 4c, a normal-pressure water tank 18, a pressure-resistant gas tank 19, an oil-water separator 20, an air compressor 23, a pressure-resistant oil tank 26, a sand box and a pressure-resistant water tank 27, wherein all the components are communicated through a pipeline 6, and each inlet and outlet is provided with a valve for control;
the bottom of the normal pressure oil tank 1 is communicated with the upper part of a pressure-resistant oil tank 26 through a first centrifugal pump 4a, and the side surface of the upper part of the pressure-resistant oil tank 26 is communicated with an oil-water separator 20 through a second centrifugal pump 4 b;
the sand box comprises a cover plate 14, pressing devices 15 a-15 b and a transparent box body 16, wherein the cover plate 14 is pressed at the upper end of the transparent box body 16 through the pressing device 15, two sides of the transparent box body 16 are respectively communicated with an oil-water separator 20 and a pressure-resistant water tank 27, the bottom of the transparent box body 16 is communicated with a pressure-resistant gas tank 19, the cover plate 14 is provided with a vent pipe 24 communicated with the inner cavity of the transparent box body 16, a flange 9, a leakage unit 10, a parallel pipeline 13 and a plurality of temperature sensors 12 are arranged in the transparent box body 16, the leakage unit 10 is communicated with the bottom of the pressure-resistant oil tank 26 through the flange 9, and an infrared thermal imager 17 is further arranged beside the transparent;
the upper part of the pressure-resistant water tank 27 is communicated with the bottom of the normal-pressure water tank 18 through a third centrifugal pump 4c, and the upper part of the pressure-resistant gas tank 19 is communicated with the air compressor 23.
Liquid level meters are arranged on the normal-pressure oil tank 1, the normal-pressure water tank 18, the pressure-resistant oil tank 26 and the pressure-resistant water tank 27, temperature control devices 25 are arranged in the pressure-resistant air tank 9 and the pressure-resistant oil tank 26, and a sewage pool 28 is arranged below the oil-water separator 20.
A thermometer 8 is arranged between the flange 9 and the pressure-resistant oil tank 26; pressure gauges are arranged between the first centrifugal pump 4a and the pressure-resistant oil tank 26, between the flange 9 and the pressure-resistant oil tank 26, between the pressure-resistant water tank 27 and the third centrifugal pump 4c, and between the pressure-resistant gas tank 19 and the air compressor 23, and flow meters are arranged between the flange 9 and the pressure-resistant oil tank 26, between the transparent box body 16 and the pressure-resistant gas tank 19, and between the transparent box body 16 and the pressure-resistant water tank 27.
The experimental platform further comprises a PCL control cabinet 21 and a central control room 22 which are electrically connected with each other, and all the valves, the pressure gauge, the flow meter, the thermometer 8, the temperature sensor 12, the infrared thermal imager 17 and the air compressor 23 are electrically connected with the PCL control cabinet 21.
The experiment platform consists of a pipeline conveying system, a sand box, a data acquisition and experiment control system, a leakage unit, a temperature control system and an emptying system. The pipeline conveying system can be divided into three subsystems of oil conveying, water conveying and air conveying.
Wherein the head end of the oil product conveying system is provided with a normal pressure oil tank 1 for storing oil products, the normal pressure oil tank 1 is provided with a liquid level meter 2 for displaying oil product liquid level, a first centrifugal pump 4a for providing power to ensure stable pipeline oil product flow, a pressure resistant oil tank 26 is a buffer tank for maintaining the pressure stability of the oil product conveying system, the pressure resistant oil tank 26 is provided with a liquid level meter 2b for displaying oil product liquid level, a temperature control device 25a for controlling the temperature of the oil products in the pressure resistant oil tank at a set temperature, a first flow meter 7a for recording the instantaneous leakage rate of the oil products, a leakage unit 10 for simulating an underground pipeline with a leakage orifice, and the oil-water separator 20 is composed of a section of pipeline with two ends plugged and an outer wall surface opened, is opened in the middle part of the pipeline and is connected with a short pipe with a smaller diameter, the other end of the short pipe is connected, the oil on the upper part of the separator is pressurized by a second centrifugal pump 4b and then is conveyed back to a pressure-resistant oil tank 26, the water on the lower part of the separator enters a sewage pool 28, a first stop valve 3a, a second stop valve 3b, a third stop valve 3c, a tenth stop valve 3j, an eleventh stop valve 3k, a twelfth stop valve 3L, a twentieth stop valve 3t and a twenty-first stop valve 3u in an oil conveying system are used for controlling the experiment process, a pressure gauge 5a is used for detecting the pressure value of the oil after the centrifugal pump 4a is pressurized, a pressure gauge 5b is used for detecting the pressure value of the oil at the outlet of the pressure-resistant oil tank 26 and making the pressure value equal to the pressure value at the leakage hole, and a thermometer 8 is used for detecting the temperature of the oil.
The water conveying system head end is equipped with ordinary pressure water pitcher 18 in order to store water, be equipped with the liquid level gauge 2c on the ordinary pressure water pitcher 18 and be used for showing the liquid level of water, centrifugal pump 4c is used for providing power and guarantees stable pipeline discharge, withstand voltage water pitcher 27 is the buffer tank, be used for maintaining the stability of water conveying system pressure, be equipped with level gauge 2d on the withstand voltage water pitcher 26 and be used for showing the liquid level of water, third flowmeter 7c is used for the instantaneous flow of record water, shut-off valve fifth stop valve 3e among the oil conveying system, sixth stop valve 3f, seventh stop valve 3g, eighth stop valve 3h, ninth stop valve 3i is used for controlling the experiment process, pressure gauge 5d is used for detecting the water pressure value after the.
The head end of the air delivery system is an air compressor 23 and is used for providing power to ensure stable pipeline air flow, the pressure-resistant air tank 19 is a buffer tank and is used for maintaining the pressure of the air delivery system to be stable, the temperature control device 25b is used for controlling the temperature of air in a pressure-resistant air pipe at a set temperature, the third flow meter 7c is used for recording the instantaneous flow of the air, the thirteenth stop valve 3m, the fourteenth stop valve 3n, the fifteenth stop valve 3o, the sixteenth stop valve 3p, the seventeenth stop valve 3q, the eighteenth stop valve 3r and the nineteenth stop valve 3s in the air delivery system are used for controlling the experiment process, and the pressure gauge 5c is used for detecting the air pressure value after the air.
The cover plate 14 in the sand box is used for transmitting the force of the pressing device 15 through the cover plate 14 to simulate different pipeline burial depths when simulating the soil burial depth, the pressing device 15 is used for providing the soil surface pressure required by simulating the soil burial depth, the structural schematic diagram of the pressing device 15 is shown in figure 2, an upper pressing plate 29 is connected with a lower pressing plate 30 through a sleeve, a metal plate with threaded holes is welded outside the sleeve, a force applying rod 31 with threads at the upper end penetrates through the two threaded holes, a baffle is arranged at the lower part of the force applying rod, and the upper pressing plate and the lower pressing plate are driven to move up and down along the direction of the sleeve by rotating the force applying rod to apply pressure to the soil surface;
the emptying system consists of a twenty-second stop valve 3v and an emptying vertical pipe 24 and is used for discharging mixed gas formed by petroleum steam and stripping gas during pollutant removal experiments.
An experimental method for leakage diffusion and pollutant removal of a buried liquid hydrocarbon pipeline comprises the following steps:
(1) determining basic parameters, namely determining the soil density and the internal friction angle according to the soil type for experiments, and measuring the area of a leakage orifice and the wall thickness of a damaged pipeline;
(2) burying the sand box layer by layer, burying the temperature sensor 12, the parallel pipeline 13, the pressure sensor 11 and the damaged pipeline into the soil, recording the positions of the pipeline and each sensor in the soil, wherein the burial depth of the pressure sensor 11 is the same as that of the leakage hole, and covering the cover plate 14 when the soil is nearly full;
(3) according to the required equivalent burial depth, applying pressure to the soil surface through a pressing device 15, and simultaneously recording the pressure value of a pressure sensor until the pressure value of the pressure sensor 11 meets the pressure value of the equivalent burial depth;
(4) pumping petroleum into a pressure-resistant oil tank 26, maintaining a certain pressure, opening a switch of a temperature control device 25, heating the petroleum to the required temperature, pumping clear water into a pressure-resistant water tank 27, maintaining a certain pressure, pressurizing air by an air compressor 23, introducing the air into a pressure-resistant air tank 19, maintaining a certain pressure, opening a switch of the temperature control device 25, and heating the compressed air to the required temperature;
(5) opening an outlet valve of the pressure-resistant water tank 27, controlling the water level and water flow in the sand tank to be required values, and simulating the underground water level and underground water flow; opening an outlet valve of the pressure-resistant oil tank 26, introducing oil into the leakage unit, recording the leakage flow through a first flow meter 7a, recording the internal pressure of a leakage pipe section through a pressure meter, and at the moment, oil leaks into soil; recording the temperature of the soil at different positions and different moments through a temperature sensor 12; opening the infrared thermal imager 17 and recording the temperature fields of the soil surface at different moments; when oil and water are diffused to the bottom of the sand box, an oil-water mixture enters the oil-water separator through a tenth stop valve 3j, an eleventh stop valve 3k and a twelfth stop valve 3L at an outlet on one side of the sand box, after being separated by the separator, the oil on the upper part of the separator is pumped back to the pressure-resistant oil tank through a centrifugal pump 4b, and the water on the lower part flows into a sewage pool through a twentieth stop valve 3 t;
(6) after the leakage diffusion experiment is finished, closing outlet valves of the pressure-resistant water tank 27 and the pressure-resistant oil tank 26, weighing the mass of the whole sand box at the moment, opening an outlet valve of the pressure-resistant air tank 19, enabling air for stripping to enter soil from the bottom of the sand box, enabling stripping air flowing through the soil to enter an emptying system, emptying the emptying system, and discharging mixed air into the air; weighing the sand box once every a period of time;
(7) calculating to obtain the flow coefficient of the leakage hole; the pressing device 15 is used for changing the equivalent burial depth of the pipeline, so that the influence rule of different burial depths on the leakage rate and the diffusion range can be researched; the influence rule of different water levels and groundwater flow on diffusion can be researched by controlling the opening of the outlet valve of the pressure-resistant water tank 27 and the opening of the outlet valve on the side surface of the sand box; the influence rule of the parallel pipeline 13 on the petroleum diffusion range can be researched by changing the relative position between the parallel pipeline 13 and the damaged pipeline; the effect of removing petroleum pollutants by different stripping gas flow and temperature can be researched by changing the opening of an outlet valve of the pressure-resistant gas tank 19 and the stripping gas temperature.
The working principle of the method is as follows:
(1) leakage principle of damaged pipeline under pressure
When the pipeline is broken and leaks, the leakage rate meets the calculation of the Bernoulli equation of the constant total flow of the incompressible viscous fluid, and the form of the Bernoulli equation is shown as a formula (1). The leakage rate q is directly measured by the flowmeter, A is calculated according to the size of the leakage port, p1、p2Respectively by a pressure gauge arranged on the pipe and a pressure sensor arranged in the soil, p being measurable by laboratory tests. Mu is related to factors such as orifice wall thickness, shape, oil flow velocity and the like, and cannot be obtained through calculation, and the flow coefficient mu can be obtained through back calculation under the known conditions of the rest values in the formula (1), wherein the expression formula is shown in the formula (2). The influence rule of different shapes and sizes on the flow coefficient mu can be researched by replacing pipe sections with different shapes and sizes.
q-leakage Rate, m3/s；
μ -flow coefficient of orifice leakage, Pa;
a-area of the orifice, m2；
p1-the pressure in the pipeline medium transport, Pa;
p2-the soil pressure, Pa, at the depth of the leak orifice;
rho-oil density, kg/m3；
(2) Principle of simulating soil buried depth
Buried petroleum pipeline's buried depth variation changes greatly, and the scope is from being less than one meter to tens meters, in order to study petroleum pipeline leakage diffusion law under different soil buried depths, based on the maston soil pressure theory, simulates the soil buried depth. In this theory, under the condition that other conditions are not changed, the soil pressure at a certain position in the soil and the buried depth are in one-to-one correspondence. The Maston's earth pressure calculation formula is shown in formula (3):
σz-earth pressure, Pa, at the depth of the burial;
d, the diameter of the steel pipe, m;
gamma-soil volume weight, N/m3，γ＝ρsog，ρsoIs the soil density, kg/m3Selected from tables 1 and 2, g is the acceleration of gravity, 9.81m/s2；
k-the coefficient of the soil pressure,
h, buried depth, m;
according to the formula (3), a calculation formula of the soil burial depth can be obtained, as shown in the formula (4). The compaction device applies pressure on the soil surface, and the pressure sensor which is coaxial with the experimental pipeline buried in the soil measures the soil pressure in the buried depth, so that the equivalent buried depth of the point can be converted. The equivalent burial depth is the depth of soil required when the pressure value P1 of the horizontal plane on which the axis of the pipeline is located in the soil is equal to the pressure value P2 of the horizontal plane on which the axis of the pipeline is located when the surface of the soil is compressed when the surface of the soil is not compressed.
TABLE 1 Sand Density ρsoAnd angle of internal friction
TABLE 2 Clay Density ρsoAnd angle of internal friction
(3) Simulation principle of underground water level and underground water flow
In order to research the influence rule of the underground water level and the underground water flow on the petroleum diffusion, the underground water level and the underground water flow condition are simulated by a method of forming a water injection hole at one side of a transparent sand box. The clear water enters the pressure buffer tank after being pressurized by the centrifugal pump, enters the soil of the transparent sand box through the valve, and reaches the water outlet hole at the other side of the transparent sand box through the soil and enters the oil-water separator through the valve. The underground water level and the flow of underground water are controlled by controlling the opening degree of the water inlet valve and the water outlet valve.
(4) Parallel pipeline simulation principle
The parallel laying of pipelines has the advantages of less land acquisition, convenient management, low construction cost and the like, and the parallel laying mode of oil and gas pipelines is adopted in China. The influence rule of the parallel pipelines on the diffusion of petroleum in the soil is researched by burying the cylindrical metal pipelines in the transparent sand box.
(5) Experimental principle for removing pollutants
The oil leakage pollutes the soil, and researches show that the soil stripping technology is a very effective organic pollutant on-site treatment technology for volatile organic pollutants, and the soil stripping technology is a technology for introducing dry air into the soil to carry the pollutants out of the soil. According to the phase equilibrium principle, each component in a liquid mixture at a certain temperature has an equilibrium partial pressure, and when the equilibrium partial pressure of the component in a gas phase in contact with the component in a liquid phase tends to zero, the equilibrium partial pressure of the gas phase is far less than that of the liquid phase, so that the component is converted from the liquid phase to the gas phase. The partial pressure of the petroleum component in the dry air is almost zero, and the petroleum component in the soil diffuses into the air when the dry air passes through the soil containing the petroleum component. And (3) calculating the gasoline loss in the stripping process by adopting a subtraction method, namely weighing the mass of the whole sand box before the removal experiment of the polluted area is started, and weighing once after the experiment is started without a period of time, so that the loss of the petroleum in the soil is the mass difference of the whole sand box within a period of time. By controlling the air flow and the temperature, the influence rule of different air flows and temperatures on the stripping effect can be researched.
(6) Principle for measuring petroleum diffusion range
The temperature of petroleum is heated to the temperature different from the temperature of soil during the experiment, and when the petroleum diffuses in the soil, the leaked petroleum changes the temperature field of the soil due to the fact that the temperature of the leaked pollutants is different from the temperature of the soil, the temperature field of the leaked petroleum is continuously changed along with the continuous diffusion of the pollutants, and the pollution condition of the petroleum can be judged by observing the change of the temperature field of the soil. The temperature sensors are arranged at different positions in the soil, the initial temperature field of the transparent sand box soil is recorded before leakage begins, and the temperature of each sensor at different moments is recorded after leakage begins, so that the change of the temperature field in the soil along with time, namely the change of the diffusion range along with time is obtained. Because the temperature sensor buried in the soil can only obtain the change of the temperature data at the arrangement point of the sensor and can not obtain a continuous temperature field, the infrared thermal imager is adopted to obtain the continuous change rule of the soil surface temperature field, and the diffusion condition of petroleum in the soil can be reflected on the other hand.
Although the present invention has been described with reference to the above embodiments, it should be understood that the present invention is not limited to the above embodiments, and those skilled in the art can make various changes and modifications without departing from the scope of the present invention.
Claims (5)
1. An experimental platform for leakage diffusion and pollutant removal of a buried liquid hydrocarbon pipeline is characterized by comprising an atmospheric pressure oil tank (1), a first centrifugal pump (4 a), a second centrifugal pump (4 b), a third centrifugal pump (4 c), an atmospheric pressure water tank (18), a pressure-resistant gas tank (19), an oil-water separator (20), an air compressor (23), a pressure-resistant oil tank (26), a sand box, a pressure-resistant water tank (27), a PCL control cabinet (21) and a central control room (22), wherein the PCL control cabinet and the central control room are electrically connected with each other;
the bottom of the normal-pressure oil tank (1) is communicated with the upper part of a pressure-resistant oil tank (26) through a first centrifugal pump (4 a), and the side surface of the upper part of the pressure-resistant oil tank (26) is communicated with an oil-water separator (20) through a second centrifugal pump (4 b);
the sand box comprises a cover plate (14), a pressing device and a transparent box body (16), wherein the cover plate (14) is pressed at the upper end of the transparent box body (16) through the pressing device, two sides of the transparent box body (16) are respectively communicated with an oil-water separator (20) and a pressure-resistant water tank (27), the bottom of the transparent box body (16) is communicated with a pressure-resistant gas tank (19), the cover plate (14) is provided with a vent pipe (24) communicated with the inner cavity of the transparent box body (16), a flange (9), a leakage unit (10), a parallel pipeline (13), a plurality of pressure sensors (11) and temperature sensors (12) are arranged in the transparent box body (16), the leakage unit (10) is used for simulating a buried pipeline with a leakage orifice, consists of a pipeline with two ends blocked and an outer wall surface opening, is opened in the middle of the pipeline and connected with a short pipe with a smaller diameter, and the other end of the short pipe is communicated with the bottom of, an infrared thermal imager (17) is arranged beside the transparent box body (16);
the upper part of the pressure-resistant water tank (27) is communicated with the bottom of the normal-pressure water tank (18) through a third centrifugal pump (4 c), and the upper part of the pressure-resistant gas tank (19) is communicated with an air compressor (23);
a thermometer (8) is arranged between the flange (9) and the pressure-resistant oil tank (26); pressure gauges are arranged between the first centrifugal pump (4 a) and the pressure-resistant oil tank (26), between the flange (9) and the pressure-resistant oil tank (26), between the pressure-resistant water tank (27) and the third centrifugal pump (4 c), and between the pressure-resistant gas tank (19) and the air compressor (23), a first flowmeter (7 a) is arranged between the flange (9) and the pressure-resistant oil tank (26), a second flowmeter (7 b) is arranged between the transparent box body (16) and the pressure-resistant gas tank (19), and a third flowmeter (7 c) is arranged between the transparent box body (16) and the pressure-resistant water tank (27);
the pressure gauge, the first flowmeter (7 a), the second flowmeter (7 b), the third flowmeter (7 c), the thermometer (8), the temperature sensor (12), the infrared thermal imager (17) and the air compressor (23) are all electrically connected with the PCL control cabinet (21);
the pressing device comprises an upper pressing plate (29), a lower pressing plate (30), a stress application rod (31) and a sleeve, the upper pressing plate (29) is connected with the lower pressing plate (30) through the sleeve, a metal plate with a threaded hole is welded outside the sleeve, the stress application rod (31) with threads at one upper end penetrates through the two threaded holes, a baffle is arranged on the lower portion of the stress application rod (31), the upper pressing plate (29) and the lower pressing plate (30) are driven to move up and down along the sleeve direction through the rotating stress application rod, and pressure is applied to the surface of soil.
2. The experimental platform for leakage diffusion and contaminant removal of the buried liquid hydrocarbon pipeline according to claim 1, wherein liquid level meters are arranged on the atmospheric pressure oil tank (1), the atmospheric pressure water tank (18), the pressure resistant oil tank (26) and the pressure resistant water tank (27).
3. The experimental platform for leakage diffusion and contaminant removal of the buried liquid hydrocarbon pipeline according to claim 2, wherein temperature control devices are respectively arranged in the pressure-resistant gas tank (19) and the pressure-resistant oil tank (26).
4. The experimental platform for leakage diffusion and contaminant removal of buried liquid hydrocarbon pipelines according to claim 3, wherein a sewage tank (28) is arranged below the oil-water separator (20).
5. An experimental method using the experimental platform for leakage diffusion and contaminant removal of the buried liquid hydrocarbon pipeline of claim 4, comprising the following steps:
(1) determining basic parameters, namely determining the soil density and the internal friction angle according to the soil type for experiments, and measuring the area of a leakage orifice and the wall thickness of a damaged pipeline;
(2) burying sand boxes in layers, namely burying a temperature sensor (12), a parallel pipeline (13), a pressure sensor and a damaged pipeline into soil, recording the positions of the pipeline and each sensor in the soil, wherein the burial depth of the pressure sensor is the same as that of a leakage hole, and covering a cover plate (14) when the soil is nearly paved;
(3) according to the required equivalent burial depth, applying pressure to the soil surface through a pressing device (15), and simultaneously recording the pressure value of the pressure sensor until the pressure value of the pressure sensor meets the pressure value of the equivalent burial depth;
(4) pumping petroleum into a pressure-resistant oil tank (26), maintaining a certain pressure, turning on a switch of a temperature control device (25), heating the petroleum to the required temperature, pumping clear water into a pressure-resistant water tank (27), maintaining a certain pressure, pressurizing air by an air compressor (23), introducing the air into a pressure-resistant air tank (19), maintaining a certain pressure, turning on a switch of the temperature control device, and heating the compressed air to the required temperature;
(5) opening an outlet valve of the pressure-resistant water tank (27), controlling the water level and water flow in the sand tank to be required values, and simulating the underground water level and underground water flow; opening an outlet valve of a pressure-resistant oil tank (26), introducing oil into the leakage unit, recording the leakage flow through a first flowmeter (7 a), recording the internal pressure of a leakage pipe section through a pressure gauge, and then, oil leaks into soil; recording the temperatures of different positions and different moments of the soil through a temperature sensor (12); opening an infrared thermal imager (17) and recording the temperature fields of the soil surface at different moments; when oil and water are diffused to the bottom of the sand box, an oil-water mixture enters the oil-water separator (20) through an outlet stop valve on one side of the sand box, after being separated by the oil-water separator (20), the oil on the upper part of the oil-water separator (20) is pumped back to the pressure-resistant oil tank (26) through the second centrifugal pump (4 b), and the water on the lower part flows into the sewage pool (28) through the twentieth valve (3 t);
(6) after the leakage diffusion experiment is finished, closing outlet valves of a pressure-resistant water tank (27) and a pressure-resistant oil tank (26), weighing the mass of the whole sand box at the moment, opening an outlet valve of a pressure-resistant air tank (19), enabling air for stripping to enter soil from the bottom of the sand box, enabling stripping air flowing through the soil to enter an emptying system, emptying the emptying system, and discharging mixed air into the air; weighing the sand box once every a period of time;
(7) calculating to obtain the flow coefficient of the leakage hole; the impact rule of different burial depths on the leakage rate and the diffusion range can be researched by changing the equivalent burial depth of the pipeline through the pressing device (15); the influence rule of different water levels and groundwater flow on diffusion can be researched by controlling the opening of the outlet valve of the pressure-resistant water tank (27) and the opening of the outlet valve on the side surface of the sand box; the influence rule of the parallel pipeline (13) on the petroleum diffusion range can be researched by changing the relative position between the parallel pipeline (13) and the damaged pipeline; the effect of removing petroleum pollutants by different stripping gas flow and temperature can be researched by changing the opening of an outlet valve of the pressure-resistant gas tank (19) and the stripping gas temperature.
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