Water surface LNAPL layer thickness online monitoring device and method based on light refraction principle

Abstract

The invention discloses a water surface LNAPL layer thickness online monitoring device and method based on the light refraction principle. The device is composed of a laser range finder, a light receiver, a light source, a distance rod, data processing equipment and the like. The length of the distance rod in liquid is calculated through data of a laser range finder, and the thickness of the oil film in underground water is calculated according to the transverse propagation distance difference of the running path of light passing through an oil layer or not. The device is free of moving equipment, low in failure rate, small in size and high in precision, and is not influenced by underground water level fluctuation. According to the method, real-time online monitoring of the NAPL phase thickness in underground water can be realized through the underground water monitoring well.

Description

Technical Field

[0001] The present invention relates to the technical field of groundwater pollution prevention and control, and particularly relates to an on-line monitoring device and method for the thickness of the LNAPL layer on the water surface based on the principle of light refraction. Background Art

[0002] In view of the special development process of the energy and chemical industries, their production and operation processes have caused varying degrees of pollution to the soil and groundwater in their respective areas. In some plots severely polluted by non-aqueous phase liquids (NAPL), NAPL will migrate downward along soil cracks. Since the density of light non-aqueous phase liquid (LNAPL) is less than that of water, it will accumulate above the soil saturation zone (groundwater) to form a non-aqueous phase liquid. In the LNAPL phase in the plot, part of it will dissolve in the groundwater and cause greater-range groundwater pollution with the flow of groundwater in the plot. Currently, an effective method is to build larger monitoring wells near the monitoring wells where the LNAPL phase is found and pump out the LNAPL from the larger monitoring wells. Since the migration speed of LNAPL in the soil is slow, when pumping out LNAPL from the groundwater monitoring well, the LNAPL in the monitoring well will be quickly pumped out, but the LNAPL around the monitoring well cannot migrate to the monitoring well in time, which will cause the LNAPL extraction equipment to pump out too much groundwater. Pumping out too much groundwater will not only increase the amount of sewage treatment, but also lower the water level and cause more soil pollution. Therefore, it is necessary to monitor the thickness of the LNAPL phase in the groundwater monitoring well in real time, so as to provide a basis for the LNAPL phase extraction plan.

[0003] Currently, there is no literature reporting the monitoring of the LNAPL phase. However, referring to the methods for monitoring the thickness of the oil layer in the catering industry, the methods for monitoring the thickness of the oil layer can be divided into the float method based on density, the optoelectronic method (Reference 1), the long and short probe method (Reference 2), the moving probe method (Reference 3), etc.

[0004] Reference 1: Chinese patent document with the patent application number CN200520010095.1.

[0005] Reference 1 discloses an optoelectronic on-line measurement system for the thickness of the floating oil layer on the liquid surface, including: transmitting and receiving optical heads (D, T), an optical reflection prism, a drive circuit. The system also includes a motor, a motor drive circuit, a shaping circuit, a single-chip microcomputer circuit, a display circuit, and a display drive circuit. Controlled by a single-chip microcomputer and adopting the ratio of two count values N1 and N2 in the measurement calculation algorithm, the direct display of the thickness of the floating oil layer on the liquid surface is realized. Therefore, it has accurate on-line measurement, is convenient and intuitive to use, and can be widely applied to industries such as chemical engineering, biology, pharmacy, and environmental protection, and has good application prospects.

[0006] Reference 2: Chinese patent document with the patent application number CN201520192148.X.

[0007] Reference 2 discloses an oil layer thickness monitoring device, which consists of a long probe, a short probe, a limit sleeve, a wire, a connecting piece, and a wire sleeve; the long probe is fixedly connected to the limit sleeve, the limit sleeve is welded to the wire, and the long probe, the limit sleeve, and the wire form an electric conduction path and are led out through the connecting piece and the wire sleeve. The short probe is fixedly connected to the limit sleeve, the limit sleeve is welded to the wire, and the short probe, the limit sleeve, and the wire form an electric conduction path and are led out through the connecting piece and the wire sleeve. According to the principle that electricity can conduct in water but not in oil, the oil layer thickness is monitored.

[0008] However, the density-based float method and the long and short probe method can achieve fixed-point monitoring of the oil layer thickness to achieve the purpose of timely oil drainage, but they cannot measure the specific value of the oil layer thickness. The photoelectric method for measuring the thickness of the floating oil layer on the liquid surface cleverly uses the energy change reflected by light at different phase interfaces to find the oil-water phase interface, thereby realizing the monitoring of the oil-water phase interface. This method requires the installation of moving equipment outside the container, and the outside of the groundwater monitoring well does not have the installation conditions. Therefore, it cannot be applied to the monitoring of the oil-water phase interface in groundwater monitoring wells.

[0009] Reference 3: Chinese patent document with patent application number CN201510298881.4.

[0010] Reference 3 discloses an oil layer thickness detection device and its measurement method in a liquid tank. The device includes: a Pt electrode arranged in the liquid tank and in contact with the liquid inside, the Pt electrode is connected to a micro motor, the micro motor is connected to a resistor and a starting device, both ends of the resistor are respectively connected to the input end of a signal amplification circuit, and the output end of the signal amplification circuit is connected to a processor. This method uses the processor to collect the signals when the Pt electrode contacts the oil film and the signals when it contacts the seawater in the liquid tank in real time, and measures the oil layer thickness based on the induction principle. This method has extremely high measurement accuracy and sensitivity, and the device is small in size, convenient to carry, novel in design, and easy to produce.

[0011] However, the moving probe method can achieve real-time online measurement of the oil layer thickness on the upper part of the liquid, but it has the disadvantages that the moving equipment is not conducive to the use scenario with frequent liquid level changes, and the probe is easily attached by organic matter, affecting the accuracy.

[0012] How to achieve accurate real-time monitoring of the LNAPL thickness in groundwater monitoring wells, especially when the oil layer thickness is relatively thin, to provide a basis for avoiding frequent startup of LNAPL phase extraction equipment is the main problem solved by this patent. In addition, the device described in this patent is small in size, simple in structure, and highly feasible, and can also be applied to the determination of the oil layer thickness on the water layer surface without floating scum in the test layer and the determination of the oil layer thickness in a system with a millimeter-level accuracy requirement. Summary of the Invention

[0013] The object of the present invention is to solve the technical problem of how to achieve accurate real-time monitoring of the LNAPL thickness in a groundwater monitoring well, especially when the oil layer thickness is relatively thin, and avoid frequent startup of the LNAPL phase extraction equipment. Provided is an on-line monitoring device and method for the thickness of the LNAPL layer on the water surface based on the principle of light refraction.

[0014] To solve the above technical problems, the technical solution adopted by the present invention is: an on-line monitoring device for the thickness of the LNAPL layer on the water surface based on the principle of light refraction, which has:

[0015] A light source, placed in the aqueous phase and emitting light rays towards the outside at a non-vertical angle; and

[0016] A light receiver, placed above the water surface and receiving the light rays emitted by the light source; and

[0017] A laser rangefinder, placed above the water surface, for measuring the distance between the light receiver and the upper surface of the oil layer; and

[0018] A bracket, for carrying the light source, the light receiver and the laser rangefinder; and

[0019] A data processing device, for receiving the data detected by the light receiver and the laser rangefinder and performing calculations, and outputting the LNAPL layer thickness value.

[0020] As a further optimization of the on-line monitoring device for the thickness of the LNAPL layer on the water surface based on the principle of light refraction of the present invention: the bracket includes a fixed-distance rod, an upper bracket and a lower bracket. The upper bracket and the lower bracket are parallel to each other and are respectively perpendicular to the fixed-distance rod and are arranged at its upper and lower ends. The laser rangefinder and the light receiver are arranged on the upper bracket, and the light source is arranged on the lower bracket.

[0021] As a further optimization of the on-line monitoring device for the thickness of the LNAPL layer on the water surface based on the principle of light refraction of the present invention: the fixed-distance rod is a telescopic straight rod.

[0022] As a further optimization of the on-line monitoring device for the thickness of the LNAPL layer on the water surface based on the principle of light refraction of the present invention: a traction hole is provided on the upper bracket. The connection line between the center of the traction hole and the center of gravity of the device is parallel to the fixed-distance rod, and a suspension rope is installed on the traction hole.

[0023] As a further optimization of the on-line monitoring device for the thickness of the LNAPL layer on the water surface based on the principle of light refraction of the present invention: the test accuracy of the light rangefinder is 0.01 mm; the resolution of the light receiver is higher than 0.01 mm; the light source can emit direct light, and the thickness of the light ray is not greater than 0.01 mm.

[0024] As a further optimization of an on-line monitoring device for the thickness of the LNAPL layer on the water surface based on the principle of light refraction according to the present invention: the data processing device includes a data processing unit and a data transmission unit. The data processing unit has functions of data display, input, and editing calculation. The data transmission unit has components for transmitting data on the data processor to a remote memory, components for an app to call data from the remote memory, and components for running the app.

[0025] As a further optimization of an on-line monitoring device for the thickness of the LNAPL layer on the water surface based on the principle of light refraction according to the present invention: the data transmitted by the data transmission unit includes input data, measured data, test time, calculated oil layer thickness data, and instrument status.

[0026] The present invention also provides an on-line monitoring method for the thickness of the LNAPL layer on the water surface based on the principle of light refraction, characterized in that

[0027] S1. Roughly detect the thickness of the oil layer in the groundwater monitoring well, and measure the refractive index n of the upper oil layer of the groundwater o ;

[0028] S2. Adjust the length of the fixed-distance rod to be greater than the roughly measured oil layer thickness, and then use the rope fixed to the traction hole of the device to lower the device into the groundwater monitoring well. The light source is placed in the water phase, and the laser rangefinder and the light receiver are kept in the gas phase above the oil layer, ensuring that the fixed-distance rod of the detection device is perpendicular to the underground water surface. Turn on the light source, the light receiver, and the laser rangefinder;

[0029] S3. The data processing device receives the data from the light receiver and the laser rangefinder and calculates the real-time thickness H of the LNAPL layer through the following formula o :

[0030] L 测 -(H L tanα + H A tany) = H o (tanβ - tanα)

[0031] where L 测 is the lateral propagation distance of the light measured by the light receiver;

[0032] H L is the length of the fixed-distance rod extending below the groundwater liquid level;

[0033] H A is the distance from the light receiver to the upper surface of the oil layer measured by the laser rangefinder;

[0034] H O is the real-time thickness of the LNAPL layer;

[0035] α is the incident angle set by the light source;

[0036] β is the exit angle of light entering the oil layer;

[0037] γ is the exit angle of light exiting the water surface and entering the air.

[0038] As a further optimization of an on-line monitoring method for the thickness of the LNAPL layer on the water surface based on the principle of light refraction in the present invention: in step S1, the vertical intercept method is used to sample the liquid in the monitoring well to roughly detect the thickness of the oil layer in the groundwater monitoring well.

[0039] The β and γ are calculated by the following formula:

[0040]

[0041]

[0042] Among them, n o is the refractive index of oil, n W is the refractive index of water, n A is the refractive index of air.

[0043] The present invention has the following beneficial effects: by using the device and method of the present invention, when the LNAPL layer in groundwater is relatively thin, the thickness of the LNAPL layer can be monitored in real time and on-line through the groundwater monitoring well, providing data support for the start and stop of the extraction equipment through the groundwater monitoring well. And the device of the present invention has no moving equipment, low failure rate, small volume and high precision, and is not affected by the fluctuation of the groundwater level. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a schematic structural diagram of the on-line monitoring device of the present invention;

[0045] Figure 2 is a schematic principle diagram in the monitoring method of the present invention;

[0046] Markings in the figure: 102, rope and data transmission line; 103, laser rangefinder; 104, optical receiver; 105, upper bracket; 106, fixed-distance rod; 107, lower bracket; 108, light source; 109, wire; 110, data processing unit; 111, output transmission unit. DETAILED DESCRIPTION OF THE INVENTION

[0047] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments. However, the content of the present invention is not limited to the following embodiments.

[0048] <Example 1>

[0049] As Figure 1 shown: An on-line monitoring device for the thickness of the LNAPL layer on the water surface based on the principle of light refraction, which has a light source 108, a light receiver 104, a laser rangefinder 103, a bracket and a data processing device.

[0050] Among them, the bracket is used to carry the light source 108, the light receiver 104 and the laser rangefinder 103. The bracket includes a fixed-distance rod 106, an upper bracket 105 and a lower bracket 107. The upper bracket 105 and the lower bracket 107 are parallel to each other and are respectively perpendicular to the fixed-distance rod 106 and are arranged at its upper and lower ends. The laser rangefinder 103 and the light receiver 104 are arranged on the upper bracket 105, and the light source 108 is arranged on the lower bracket 107. The above structural design can ensure that the longitudinal distance between the light source 108 and the fixed-distance rod 106 does not change with the change of the lateral distance. The light source 108 can be rotated at any angle or installed at a fixed angle on the lower bracket 107. And ensure that the longitudinal distance between the laser rangefinder 103 and the fixed-distance rod 106 does not change with the change of the lateral distance.

[0051] The fixed-distance rod 106 is a telescopic straight rod. After the fixed-distance rod is telescoped, it can bear a weight of 10 kg without bending and the length remains unchanged.

[0052] The upper bracket 105 is provided with a traction hole. The connection line between the center of the traction hole and the center of gravity of the device is parallel to the fixed-distance rod 106. A suspension rope 102 is installed on the traction hole. The device is put into a groundwater monitoring well or other places where it is needed through the rope 102 fixed on the traction hole.

[0053] Among them, the light source 108 is placed in the water phase and emits light towards the outside at a non-vertical angle. The light source can emit direct light, and the thickness of the light is not greater than 0.01 mm.

[0054] Among them, the light receiver 104 is placed above the water surface and receives the light emitted by the light source 108. The resolution of the light receiver is higher than 0.01 mm.

[0055] Among them, the laser rangefinder 103 is placed above the water surface and is used to measure the distance between the light receiver 104 and the upper surface of the oil layer. The test accuracy of the light rangefinder is 0.01 mm. The laser rangefinder 103 is a small-volume laser rangefinder that can be placed in a groundwater monitoring well.

[0056] Among them, the data processing device is used to receive the data detected by the light receiver 104 and the laser rangefinder 103 and perform calculations, and output the LNAPL layer thickness value.

[0057] The data processing device includes a data processing unit 110 and a data transmission unit 111. The data processing unit 110 has functions of data display, input, and editing and calculation. The data transmission unit 111 has components for transmitting data on the data processor to a remote memory, components for an app to call data from the remote memory, and components for running the app. The data transmitted by the data transmission unit 111 includes input data, measured data, test time, calculated oil layer thickness data, and instrument status.

[0058] <Example 2>

[0059] As Figure 2 shown: An on-line monitoring method for the thickness of the LNAPL layer on the water surface based on the principle of light refraction: Adjust the length of the fixed-distance rod to be greater than the estimated oil layer thickness, and lower the device into the groundwater monitoring well through the rope fixed to the device towing hole, so that the light source is placed in the water phase and the laser rangefinder is kept in the gas phase above the oil layer, ensuring that the fixed-distance rod of the detection device is perpendicular to the underground water surface. Turn on each component of the oil layer thickness measuring instrument, and emit the light source towards the oil-water phase interface at an incident angle of α. Calculate the thickness of the oil layer on the underground water surface through the data processor.

[0060] The light source emits towards the oil-water phase interface at an incident angle of α. Assuming there is no oil layer on the water surface, the exit angle of the light emerging from the water surface into the air is γ, and the relationship between α and β is shown in Equation 1. If there is an oil layer on the water surface, the exit angle β of the light entering the oil layer is related to the refractive index of the oil layer, and the relationship between β and α is shown in Equation 2. The light emits towards the oil-air phase interface at an incident angle of β. From Equations 1, 2, and 3, it can be seen that the exit angle is still γ. The length (L) of the fixed-distance rod is a set value, and the distance H from the upper bracket to the upper surface of the oil layer measured by the laser rangefinder A , and the lateral distance L from the light source to the light-sensitive point on the light source receiving surface measured by the photosensitive material receiver 测 The value of Ho, the thickness of the oil layer on the underground water surface, can be calculated according to Equation 4. L 测 -(H L tanα + H A atany) = H o (tanβ - tanα) Equation 4

[0061] <Example 3>

[0062] Use the vertical intercept method to sample the liquid in the monitoring well and roughly detect that the thickness of the oil layer is about 1 mm. Take the refractive index n of the oil layer above the groundwater ois 1.5246, adjust the length H of the fixed-distance rod to 20 cm, the incident angle α of the light source is 5 degrees. Use the rope fixed to the device traction hole to lower the device into the groundwater monitoring well, place the light source about 10 cm below the oil-water interface, keep the laser rangefinder in the gas phase above the oil layer, ensure that the fixed-distance rod of the detection device is perpendicular to the underground water level, turn on the oil layer thickness measuring instrument, and input the set fixed-distance rod length of 20 cm and the measured refractive index n of the oil in the groundwater monitoring well o , the refractive index n of water W , the refractive index n of air A , and the incident angle α of the light source into the data processor. Set the data remote transmission device to send a data packet containing all the data in the data processor, the test time, and the instrument power every 1 minute to the remote memory. The laser rangefinder measures the distance from the oil surface in the groundwater monitoring well to the upper bracket as 10.012 cm, and the light receiver measures the lateral propagation distance L 测 from the light source to the receiving surface as 15.306 mm. According to the method described in the patent, the data processor calculates the oil layer thickness in this groundwater monitoring well as 0.62 mm. Through the app, access the oil layer thickness in the groundwater monitoring well at 9 am in the remote memory, which is 0.62 mm.

[0063] <Example 4>

[0064] Use the vertical intercept method to sample the liquid in the monitoring well and roughly detect the oil layer thickness to be about 1 mm. Take the refractive index n of the upper oil layer of the groundwater o as 1.5146, adjust the length H of the fixed-distance rod to 15 cm, the incident angle α of the light source is 10 degrees. Use the rope fixed to the device traction hole to lower the device into the groundwater monitoring well, place the light source about 7 cm below the oil-water interface, keep the laser rangefinder in the gas phase above the oil layer, ensure that the fixed-distance rod of the detection device is perpendicular to the underground water level, turn on the oil layer thickness measuring instrument, and input the set fixed-distance rod length of 15 cm and the measured refractive index n of the oil in the groundwater monitoring well o , the refractive index n of water W , the refractive index n of air A , and the incident angle α of the light source into the data processor. Set the data remote transmission device to send a data packet containing all the data in the data processor, the test time, and the instrument power every 1 minute to the remote memory. The laser rangefinder measures the distance from the oil surface in the groundwater monitoring well to the upper bracket as 8.533 cm, and the light receiver measures the lateral propagation distance L 测 from the light source to the receiving surface as 22.735 mm. According to the method described in the patent, the data processor calculates the oil layer thickness in this groundwater monitoring well as 4.95 mm. Through the app, access the oil layer thickness in the groundwater monitoring well at 9 am in the remote memory, which is 4.95 mm.

[0065] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which does not affect the essence of the present invention.

Claims

1. An on-line monitoring device for the thickness of the water surface LNAPL layer based on the principle of light refraction, characterized in that, It has: A light source (108) placed in the aqueous phase and emitting light towards the outside at a non-vertical angle; and A light receiver (104) placed above the water surface and receiving the light emitted by the light source (108); and A laser rangefinder (103) placed above the water surface for measuring the distance between the light receiver (104) and the upper surface of the oil layer; and A bracket for carrying the light source (108), the light receiver (104) and the laser rangefinder (103); and A data processing device for receiving the data detected by the light receiver (104) and the laser rangefinder (103) and performing calculations to output the LNAPL layer thickness value.

2. The on-line monitoring device for the thickness of the LNAPL layer on the water surface based on the principle of light refraction according to claim 1, characterized in that The bracket includes a fixed-distance rod (106), an upper bracket (105) and a lower bracket (107). The upper bracket (105) and the lower bracket (107) are parallel to each other and are respectively perpendicular to the fixed-distance rod (106) and are arranged at its upper and lower ends. The laser rangefinder (103) and the light receiver (104) are arranged on the upper bracket (105), and the light source (108) is arranged on the lower bracket (107).

3. The on-line monitoring device for the thickness of the LNAPL layer on the water surface based on the principle of light refraction according to claim 2, characterized in that The fixed-distance rod (106) is a telescopic straight rod.

4. The on-line monitoring device for the thickness of the LNAPL layer on the water surface based on the principle of light refraction according to claim 2 or 3, characterized in that The upper bracket (105) is provided with a traction hole, and the connection line between the center of the traction hole and the center of gravity of the device is parallel to the fixed-distance (106) rod, and a suspension rope (102) is installed on the traction hole.

5. The on-line monitoring device for the thickness of the LNAPL layer on the water surface based on the principle of light refraction according to claim 4, characterized in that The test accuracy of the optical rangefinder is 0.01 mm; The resolution of the light receiver is higher than 0.01 mm; The light source can emit direct light, and the thickness of the light beam is not greater than 0.01 mm.

6. The on-line monitoring device for the thickness of the LNAPL layer on the water surface based on the principle of light refraction according to claim 2, characterized in that The data processing device includes a data processing unit (110) and a data transmission unit (111). The data processing unit (110) has functions of data display, input and editing calculation. The data transmission unit (111) has components for transmitting the data on the data processor to a remote memory, components for an app to call the data from the remote memory, and components for running the app.

7. The on-line monitoring device for the thickness of the LNAPL layer on the water surface based on the principle of light refraction according to claim 6, characterized in that The data transmitted by the data transmission unit (111) includes input data, measured data, test time, calculated oil layer thickness data, and instrument status.

8. An on-line monitoring method for the thickness of the LNAPL layer on the water surface based on the principle of light refraction, characterized in that S1. Roughly detect the thickness of the oil layer in the groundwater monitoring well, and measure the refractive index n of the upper oil layer of the groundwater o ; S2. Adjust the length of the fixed-distance rod to be greater than the roughly measured thickness of the oil layer, and then lower the device into the groundwater monitoring well using the rope fixed to the traction hole of the device. Place the light source in the aqueous phase, and keep the laser rangefinder and the optical receiver in the gas phase above the oil layer. Ensure that the fixed-distance rod of the detection device is perpendicular to the underground water level, and turn on the light source (108), the optical receiver (104), and the laser rangefinder (103). S3. The data processing device receives the data from the optical receiver (104) and the laser rangefinder (103), and calculates the real-time thickness H of the LNAPL layer through the following formula o :[[]]END]] L 测 -(H L tan α + H A tan γ) = H o (tan β - tan α) wherein, L 测 is the lateral propagation distance of the light measured by the optical receiver; H L is the length of the fixed-distance rod extending below the groundwater level; H A is the distance from the optical receiver to the upper surface of the oil layer measured by the laser rangefinder; H O is the real-time thickness of the LNAPL layer; α is the incident angle set by the light source; β is the exit angle when the light enters the oil layer; γ is the exit angle when the light exits the water surface and enters the air.

9. The online monitoring method for the thickness of the LNAPL layer on the water surface based on the principle of light refraction according to claim 8, wherein in the step S1, the vertical intercept method is used to sample the liquid in the monitoring well to roughly detect the thickness of the oil layer in the groundwater monitoring well.

10. The online monitoring method for the thickness of the LNAPL layer on the water surface based on the principle of light refraction according to claim 9, wherein β and γ are calculated by the following formula: Among them, n o is the refractive index of oil, n W is the refractive index of water, and n A is the refractive index of air.

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