Microwave real-time detection device and method for moisture content of alcohol solution

Abstract

The invention discloses an alcohol liquid moisture content microwave real-time detection device and method.The detection device comprises a microwave sensor, a microwave generator, a power divider and a detection circuit, the microwave sensor comprises a reference transmission line, a liquid receiving transmission line, base materials and a carrier, the base materials cover the upper surface and the lower surface of the middle of the carrier respectively, and the power divider is connected with the power divider; the liquid receiving transmission line is located on the outer side of the upper surface base material, and the reference transmission line is located on the outer side of the lower surface base material. The microwave generator is electrically connected with the power divider, the power divider outputs two paths of electric signals which are respectively connected with the liquid receiving transmission line and the reference transmission line, and output signals of the liquid receiving transmission line and the reference transmission line are respectively connected with the detection circuit. According to the detection device and method, sampling, testing and other processes are not needed, real-time and continuous monitoring can be achieved, the alcohol liquid product processing, transportation and storage processes are monitored in real time, and the specific device is easy to manufacture and implement and has great practical significance.

Description

Technical Field

[0001] The invention belongs to the technical field of alcohol liquid detection, and specifically relates to a microwave real-time detection device and method for the water content of alcohol liquid. Background Art

[0002] Alcohol fuels such as ethanol fuel and methanol fuel (alcohol liquid) are generally considered to be clean, green and environmentally friendly fuels that can reduce environmental pollution and replace fossil fuels. They can replace gasoline and diesel and are used in various motor vehicles, stoves, etc. In particular, methanol can be produced by electrolysis to produce hydrogen and react with carbon dioxide in the air, which will not cause an increase in greenhouse gases. At the same time, it not only overcomes the problem that new energy sources such as solar or wind power generation are unstable and difficult to use directly and continuously, but also solves the problem that simple hydrogen production as a fuel is difficult to store and has poor safety. It has attracted great attention in the field of engineering technology research and the business community.

[0003] At present, the market for ethanol fuel vehicles and methanol fuel vehicles has emerged. In particular, methanol has become a new type of clean green energy recognized by the global industry and an important choice for building future green energy.

[0004] Since alcohol fuels such as ethanol fuel and methanol fuel have strong water absorption, excessive water content not only leads to incomplete combustion and low efficiency (water vaporization wastes energy), but also seriously affects the life of key components such as the engine. At present, the water content (or alcohol concentration) detection methods of alcohol fuels mainly include Karl Fischer method, gas chromatography, infrared spectroscopy or conductivity method, etc., which require sampling and sending to the laboratory for moisture content detection. This method requires expensive instruments and reagents and harsh laboratory conditions. In addition, alcohol liquids are hazardous chemicals that are inconvenient to carry, and alcohol fuel samples from filling stations are difficult to send to the laboratory. Other alcohol liquid concentration detections such as propanol, butanol, ethylene glycol, and glycerol all have similar problems.

[0005] In addition, the existing detection method must comply with GB / T6283-2008 "Determination of Water Content in Chemical Products - Karl Fischer Method (General Method)" and other standard requirements during the testing process to ensure the purity of samples and reagents and avoid external contamination; keep the environment dry during operation to prevent the introduction of moisture; follow safe operating procedures, especially when using chemical reagents.

[0006] In short, the existing methods for detecting the water content (or water content, which can also be called alcohol concentration) of alcohol liquids are less convenient, more expensive, and cannot be detected online in real time. Summary of the invention

[0007] The object of the present invention is to provide a device and method for real-time online detection of alcohol solution concentration or water content, so as to achieve convenient, fast, real-time and accurate acquisition of alcohol solution concentration data.

[0008] The present invention designs a microwave real-time detection device for the water content of alcohol liquid. The detection device comprises a microwave sensor, a microwave generator, a power divider and a detection circuit. The microwave sensor comprises a reference transmission line (also called a reference microstrip line), a liquid-connected transmission line (also called a liquid-connected microstrip line), a substrate and a carrier. The substrate respectively covers the upper surface and the lower surface of the middle part of the carrier (it can also completely cover the middle part of the carrier. The upper and lower surfaces are relative concepts. The upper surface of the present invention is defined as a measuring side, where the liquid-connected transmission line is installed, and the lower surface is defined as a reference side, where the reference transmission line is installed). The liquid-connected transmission line on the measuring side is located outside the substrate on the upper surface, and the reference transmission line on the reference side is located outside the substrate on the lower surface. It includes insulating materials to ensure that the upper and lower surface transmission lines transmit microwave signals independently. The carrier includes heat-conducting materials to ensure that the upper and lower surface transmission lines are measured under basically the same temperature environment. The microwave generator generates microwave signals and is electrically connected to the power distributor. The power distributor outputs two electrical signals that are respectively connected to the liquid-contacting transmission line and the reference transmission line. The output signals of the liquid-contacting transmission line and the reference transmission line are respectively connected to the detection circuit. The reference transmission line is placed outside the measured liquid or wrapped in an insulating sealing material (insulated and sealed relative to the measured liquid). In short, the external measurement environment of the reference transmission line is equivalent to the air environment and does not contact the measured liquid. The transmission line includes copper wires, silver wires, etc.

[0009] Furthermore, the detection circuit includes at least a phase-sensitive detector, a low-pass filter, a microcontroller, a power supply circuit and other units electrically connected in sequence, the input signal of the phase-sensitive detector is respectively connected to the output ends of the reference transmission line and the liquid-connected transmission line, and the microcontroller is connected to the microwave generator.

[0010] Furthermore, the wire length, shape and material of the liquid-contacting transmission line and the reference transmission line are consistent, the liquid-contacting transmission line contacts the measured medium, and the reference transmission line contacts the air or a low dielectric constant material; the measuring side and the reference side substrate (insulating layer) are made of the same material and have the same configuration (shape).

[0011] Furthermore, the microwave generator outputs a variable frequency signal of 200-960 MHz, and the power divider divides two signals in a 1:1 ratio and outputs them to the measurement side circuit and the reference side circuit respectively.

[0012] Furthermore, the substrate includes non-metallic materials such as epoxy resin glass fiber board, PEEK (polyetheretherketone), polytetrafluoroethylene or polyimide; the carrier includes metal materials such as steel, aluminum, copper, or rigid hard materials covered with metal materials.

[0013] Furthermore, the microwave sensor also includes sealing plugs located at both ends of the carrier; the detection device also includes a temperature sensor located at one end of the carrier, and the temperature sensor is electrically connected to the microcontroller for monitoring the ambient temperature.

[0014] Furthermore, the carrier includes a compact structure or a hollow structure; when the hollow structure is adopted, the microwave generator, the power distributor and the detection circuit are arranged inside the carrier.

[0015] Furthermore, the shape of the carrier includes cylindrical, elongated, flat or box-shaped shapes.

[0016] Furthermore, the carrier also has a grounding function, which can improve the safety of the detection device on the one hand, and reduce the influence of external interference on the detection circuit on the other hand.

[0017] On the other hand, a microwave real-time detection method for the water content of an alcohol liquid is provided. Based on any one of the above-mentioned microwave real-time detection devices for the water content of an alcohol liquid, the detection method includes calibration of the phase difference voltage (or amplitude difference) output value under typical temperature and typical water content (concentration) combination values, and an actual measured value interpolation method.

[0018] The advantages and beneficial effects of the present invention are: according to the relationship between the transmission speed and dielectric constant of microwaves in different medium environments, and the characteristics of different dielectric constants of different alcohol liquid concentrations (water content), the relative alcohol liquid concentration can be obtained by measuring the transmission phase difference between the measured medium and the reference medium. Due to the inherent advantages of real-time and continuity of microwave measurement, the method can be implemented by designing microwave sensors and corresponding detection circuits, thereby realizing convenient, fast, real-time and accurate detection of alcohol liquid concentrations such as general methanol, ethanol (including liquor, alcohol), propanol, butanol, ethylene glycol, glycerol, etc., especially realizing real-time detection of the water content of methanol and ethanol fuels, which can effectively solve the timely monitoring of the quality of alcohol new energy fuels in the future and promote the popularization and use of such new energy.

[0019] The detection device and method of the present invention do not require tedious and complicated experimental and testing processes such as sampling and testing, and can achieve real-time and continuous monitoring, and real-time monitoring of the processing, transportation and storage process of alcohol liquid products. It can also be processed into a portable detection device for testing whenever needed, and the specific device is simple to manufacture and implement, and has great practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structural principle of the detection device of the present invention; Figure 2 is a schematic diagram of a microwave sensor.

[0021] Markings in the figure: 1. Reference transmission line; 2. Liquid-connected transmission line; 3. Substrate; 4. Sealing plug; 5. Temperature sensor; 6. Carrier. DETAILED DESCRIPTION

[0022] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0023] Embodiment 1: The present invention provides a microwave real-time detection device for the water content of alcohol liquid, such as Figure 1 As shown, the detection device includes a microwave sensor, a microwave generator, a power divider and a detection circuit. The microwave sensor includes a reference transmission line 1 (also called a reference microstrip line), a liquid-connected transmission line 2 (also called a liquid-connected microstrip line), a substrate 3 and a carrier 6. The substrates respectively cover the upper surface and the lower surface of the middle part of the carrier 6 (it can also completely cover the middle part of the carrier. The upper and lower surfaces are relative concepts. The upper surface of the present invention is defined as a measuring side, where the liquid-connected transmission line is installed, and the lower surface is defined as a reference side, where the reference transmission line is installed). The liquid-connected transmission line 2 on the measuring side is located outside the upper surface substrate, and the reference transmission line 1 on the reference side is located outside the lower surface substrate. The substrate includes an insulating material to ensure that the upper and lower surfaces are transparent to each other. The transmission line independently transmits microwave signals, and the carrier includes a heat-conducting material to ensure that the upper and lower surface transmission lines are measured under basically the same temperature environment; the microwave generator generates a microwave signal and is electrically connected to the power divider. The power divider outputs two electrical signals that are respectively connected to the liquid-connected transmission line 2 and the reference transmission line 1. The output signals of the liquid-connected transmission line 2 and the reference transmission line 1 are respectively connected to the detection circuit. The reference transmission line is placed outside the measured liquid or wrapped in an insulating sealing material (insulated and sealed relative to the measured liquid). The external measurement environment of the reference transmission line is equivalent to the air environment, or other dielectric constant medium environments. In short, it does not contact the measured liquid; the transmission line includes a copper wire, a silver wire, etc.

[0024] The basic principle of the present invention is that the microwave signal generated by the microwave generator is transmitted to the detection circuit through the measurement side liquid transmission line (2) and the reference side reference transmission line (1) after passing through the power distributor. The detection circuit completes the reception, comparison and detection of the two microwave signals. Due to the different external medium environments of the transmission lines (different mixing ratios of water and alcohol), the dielectric constants thereof are different. According to the microwave transmission principle: Where c is the speed of light, ε is the mixed dielectric constant, and μ is the magnetic permeability. The magnetic permeability of 1 can be ignored, so the transmission speed of microwaves depends on the mixed dielectric constant. Due to the difference in dielectric constants between the reference side and the measurement side, the microwave transmission speed and transmission path are different. Different transmission speeds / paths lead to different phase shifts and / or amplitudes of microwave signals. Therefore, by simultaneously detecting and comparing the phases and amplitudes of the two microwave signals on the reference side and the measurement side, and outputting different detection voltage signals, the relative change of the dielectric constant can be obtained, and the relative change of concentration (water content) can be obtained through the relative change of the dielectric constant.

[0025] The mixed dielectric constant of the reference side circuit is composed of the dielectric constant of the reference side insulation layer and air or low dielectric constant material filler, and is a fixed value under constant temperature conditions. The mixed dielectric constant of the measurement side circuit is composed of the dielectric constant of the measurement side insulation layer and the dielectric constant of the measured medium (alcohol-water mixture). When ethanol and water are mixed in a certain ratio, their dielectric constant is related to the concentration. The higher the alcohol concentration, the lower the dielectric constant. Therefore, through the voltage signal output by the phase-sensitive detector, the relationship between the output voltage of the phase-sensitive detector and the alcohol concentration can be obtained.

[0026] Preferably, the detection circuit includes at least units such as a phase-sensitive detector, a low-pass filter, a microcontroller and a power supply circuit which are electrically connected in sequence, the input signal of the phase-sensitive detector (in1 and in2 shown in the figure) is respectively connected to the output ends of the reference transmission line and the liquid-contacting transmission line, and the microcontroller is connected to a microwave generator.

[0027] The microcontroller controls the microwave generator to generate a microwave signal of 200MHz-960MHz through the SPI bus. The microwave signal is sent to the power divider, and the power divider outputs two signals with the same power. The out1 signal is connected to the external liquid transmission line through the connecting line through the sealing plug, and the return signal connecting line passes through the sealing plug to the phase detector. The out2 signal is connected to the internal reference transmission line and returned to the phase detector. The phase detector performs phase detection on the two return signals to obtain the phase difference voltage of the two signals with the same frequency. The phase difference voltage is sampled by the microcontroller after low-pass filtering.

[0028] The output voltage of the phase-sensitive detector is inversely proportional to the phase lag. The smaller the phase difference, the lower the voltage. When the phase difference is 0, the voltage is 0. The greater the phase lag, the higher the voltage. When the phase difference lags 180 degrees, the voltage reaches the highest.

[0029] When there is no liquid to be measured, the liquid-connected transmission line is exposed to the air, and the two microwave signals output by the power divider are basically in the same environment. The phase difference returned to the phase-sensitive detector is very small and fixed. When there is a liquid to be measured, the liquid-connected transmission line is immersed in the liquid medium to be measured, such as ethanol. When immersed in pure ethanol medium, the relative dielectric constant of pure ethanol is between 16 and 24 depending on the temperature, which is much larger than the relative dielectric constant of air 1. Therefore, the phase on the liquid-connected transmission line is delayed relative to the transmission line, which can be reflected by the phase-sensitive detector; when immersed in pure water medium, the relative dielectric constant of pure water is between 76 and 81 depending on the temperature, which is larger than the relative dielectric constant of pure ethanol. Therefore, the phase on the liquid-connected transmission line is delayed relative to the transmission line.

[0030] Preferably, the wire length, shape and material of the liquid-contacting transmission line and the reference transmission line are consistent, the liquid-contacting transmission line contacts the measured medium, and the reference transmission line contacts air or a low dielectric constant material; the measuring side and the reference side substrate (insulating layer) are made of the same material and have the same configuration (shape).

[0031] Preferably, the microwave generator outputs a variable frequency signal of 200-960 MHz, and the power divider splits two signals in a 1:1 ratio and outputs them to the measurement side circuit and the reference side circuit respectively.

[0032] In principle, it is not necessary for the two powers to be consistent, nor is it necessary for the conductor lengths, shapes, and materials of the two transmission lines to be consistent, or for the substrates on both sides to be completely consistent. For inconsistent situations, it is only necessary to calibrate the value relationship in advance, but the implementation is more cumbersome. The design of this embodiment to be consistent is more convenient and simple for measurement and calculation processing, which is also a reasonable choice in actual engineering applications.

[0033] Preferably, the substrate includes non-metallic materials such as epoxy resin glass fiber board, PEEK (polyetheretherketone), polytetrafluoroethylene or polyimide; the carrier includes metal materials such as steel, aluminum, copper, or rigid hard materials covered with metal materials.

[0034] Preferably, the carrier includes a compact structure (solid structure) or a hollow structure; when the hollow structure is adopted, the microwave generator, power distributor and detection circuit are arranged inside the carrier, and a signal transmission interface or an information display screen is arranged at one end of the carrier, so that the detection device can be miniaturized, easy to install and transport, and the safety and reliability are better guaranteed; the circuit boards are installed in the carrier, the outside is wrapped with a metal shell, and the inside is filled with dry air. Although the microwave generator, power distributor and detection circuit can also be arranged outside the microwave sensor or outside the carrier, additional sealing and protection measures need to be considered, which should be determined according to the actual needs of the detection site.

[0035] Preferably, the carrier shape includes cylindrical, elongated, flat or box-shaped shapes.

[0036] The transmission line of this embodiment uses a silver wire with a diameter of 1.5 mm and a length of 30 mm. The substrate is polytetrafluoroethylene, and the carrier uses a stainless steel shell. A microwave generator, a power divider and a detection circuit board are installed inside. The center frequency of the microwave generator is 330 MHz (common center frequencies also include 500 MHz, 750 MHz, etc.), and the bandwidth is 1 MHz.

[0037] Embodiment 2: The difference from Example 1 is that the transmission line and the substrate of this embodiment are formed by etching a copper-clad laminate, wherein the microstrip transmission line has a width of 2 mm and a length of 30 mm, the substrate is the substrate of the copper-clad laminate, the carrier adopts a hard plastic compact structure covered with a layer of conductive copper, is flat, and has a thickness not less than the thickness of the substrate (i.e., the thickness of the copper-clad laminate), the transmission line leads to an external interface line, the microwave generator, the power divider and the detection circuit board are integrated into an external independent sealing and shielding box, which is connected to the external interface line of the transmission line as needed, and can be decomposed into two parts when not tested and installed.

[0038] Embodiment 3: The difference from Example 1 is that sealing plugs 4 are provided at both ends of the carrier 6 in this embodiment, which are used in special use environments such as pipeline fluids. When the sensor body is installed, the measured alcohol liquid does not leak and affect the signal measurement of the reference transmission line on the reference side. In this embodiment, the out1 signal is connected to the external liquid transmission line through the connecting line through the sealing plug, and the return signal in1 connecting line passes through the sealing plug to the phase detector; Embodiment 4: The difference from Example 1 is that a temperature sensor 5 is installed at one end of the carrier 6 in this embodiment. The temperature sensor is electrically connected to the microcontroller and is used to monitor the ambient temperature. Considering that the dielectric constant of the medium will also change at different temperatures, this design can be used for concentration measurement temperature coefficient correction (if the temperature effect is ignored, the temperature sensor can be installed). If the measurement is only at room temperature or a constant temperature, there is no need to install a temperature sensor specifically.

[0039] The detection circuit also includes a communication circuit for signal transmission and / or display, and can upload the on-site real-time moisture content detection results to a centralized monitoring terminal by wired or wireless means. For example, a winery can realize real-time and continuous monitoring of the alcohol concentration in all pipelines, fermentation tanks, wine barrels, etc. that need to be monitored.

[0040] Embodiment 5: The difference from Example 1 is that the carrier described in this embodiment also has a grounding function, which on the one hand improves the safety of the detection device, and on the other hand can reduce the influence of external interference on the detection circuit.

[0041] Embodiment 6: A microwave real-time detection method for the water content of an alcohol liquid, characterized in that, according to any one of the microwave real-time detection devices for the water content of an alcohol liquid in the above embodiments and preferred embodiments thereof, the detection method includes calibration of a phase difference voltage (or amplitude difference) output value under a typical temperature and a typical water content (concentration) combination value, and an actual value interpolation method; the typical temperature in this embodiment includes uniformly spaced points of every 5°C or 10°C in 0-80°C, the typical water content includes uniformly spaced points of every 5% or 10% in 0-100% (the concentration is 100%0-0), generally including at least two boundary points of 0 and 100%, and the combination includes all predetermined combination points of the water content from 0, 10%, 20%, ..., 100% at each temperature point; the interpolation method includes bilinear interpolation, bicubic interpolation, Lagrangian interpolation, etc., and the present embodiment adopts bilinear interpolation.

[0042] In fact, if the influence of temperature is ignored, the focus should be on calibrating the phase difference voltage output values ​​at different typical water contents at normal temperature (such as 20°C and / or 25°C, etc.) or normal working temperature of alcohol liquid, and the interpolation of measured values ​​only needs to be performed on univariate variables.

[0043] The above method belongs to numerical method. In fact, if the empirical formula of dielectric constant of alcohol solution with different concentrations is obtained, the concentration value (or water content value) can be directly calculated based on the empirical formula and the phase difference voltage measured by the microwave sensor.

[0044] The above is only a partial and more systematic and comprehensive embodiment of a microwave real-time detection device and method for the water content of alcohol liquid of the present invention. In fact, there can be many optimization schemes regarding the structure of the detection device, changes in symmetry, structural design for easy installation and carrying, display method of detection results, distribution ratio of the power divider, substrate shape and material, carrier structure shape and material, addition of other auxiliary circuits such as communication, recombination of preferred schemes, etc., including a design scheme in which the substrate and the carrier are combined into one, all of which belong to the protection scope of the present invention and are not listed one by one here.

Claims

1. A microwave real-time detection device for water content of alcohol solution, characterized in that: The detection device comprises a microwave sensor, a microwave generator, a power distributor and a detection circuit. The microwave sensor comprises a reference transmission line (1), a liquid-connected transmission line (2), a substrate (3) and a carrier (6). The substrate (3) covers the upper surface and the lower surface of the middle part of the carrier (6) respectively. The liquid-connected transmission line (2) is located outside the upper surface substrate. The reference transmission line (1) is located outside the lower surface substrate. The substrate comprises an insulating material and the carrier comprises a heat-conducting material. The microwave generator generates a microwave signal and is electrically connected to the power distributor. The power distributor outputs two electrical signals which are respectively connected to the liquid-connected transmission line (2) and the reference transmission line (1). The output signals of the liquid-connected transmission line (2) and the reference transmission line (1) are respectively connected to the detection circuit. The reference transmission line (1) is placed outside the liquid to be detected or wrapped in an insulating sealing material.

2. The microwave real-time detection device for water content of alcohol solution according to claim 1, characterized in that: The detection circuit at least includes a phase-sensitive detector, a low-pass filter, a microcontroller and a power supply circuit unit which are electrically connected in sequence. The input signal of the phase-sensitive detector is respectively connected to the output ends of the reference transmission line and the liquid-contacting transmission line. The microcontroller is connected to the microwave generator.

3. The microwave real-time detection device for water content of alcohol solution according to claim 1, characterized in that: The liquid-contacting transmission line and the reference transmission line have the same conductor length, shape, and material. The liquid-contacting transmission line contacts the measured medium, and the reference transmission line contacts air or a low dielectric constant material.

4. The microwave real-time detection device for water content of alcohol solution according to claim 1, characterized in that: The microwave generator outputs a variable frequency signal of 200-960 MHz, and the power distributor divides two signals in a 1:1 ratio and outputs them to the measurement side circuit and the reference side circuit respectively.

5. The microwave real-time detection device for water content of alcohol solution according to claim 1, characterized in that: The substrate includes epoxy resin glass fiber board, PEEK, polytetrafluoroethylene or polyimide; the carrier includes a metal material or a rigid hard material covered with a metal material.

6. The microwave real-time detection device for water content of alcohol solution according to claim 1, characterized in that: The microwave sensor further comprises sealing plugs (4) located at both ends of the carrier (6); the detection device further comprises a temperature sensor (5) located at one end of the carrier (6), and the temperature sensor is electrically connected to the microcontroller.

7. The microwave real-time detection device for water content of alcohol solution according to claim 1, characterized in that: The carrier includes a compact structure or a hollow structure. When the hollow structure is adopted, the microwave generator, the power distributor and the detection circuit are arranged inside the carrier.

8. The microwave real-time detection device for water content of alcohol solution according to claim 1, characterized in that: The carrier shape includes cylindrical, strip, flat or box-shaped.

9. The microwave real-time detection device for water content of alcohol solution according to claim 1, characterized in that: The carrier also has a grounding function.

10. A microwave real-time detection method for water content of alcohol solution, characterized in that: According to any one of claims 1 to 9, the microwave real-time detection device for the water content of an alcohol liquid, the detection method comprises calibration of the phase difference voltage output value under typical temperature and typical water content (concentration) combination values, and an actual measured value interpolation method.

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