A sensor for measuring humidity of high-temperature flue gas on line and a method for measuring humidity of high-temperature flue gas

Abstract

The present application belongs to the technical field of flue gas humidity measurement, and particularly relates to a sensor for online measurement of high-temperature flue gas humidity and a measurement method thereof. The sensor is mainly composed of a humidity sensor measurement cavity, a flue gas inlet, a flue gas outlet, and a signal processing controller connected by a signal cable. Two oxygen sensor units, the head of the 1# oxygen sensor unit and the head of the 2# oxygen sensor unit are located at the same flow cross section of the humidity sensor measurement cavity. The present application solves the problem of online measurement of flue gas humidity under the condition that the flue gas temperature is higher than 180℃, and provides a humidity sensor that can measure flue gas humidity for a long time. Further, the present application solves the problem that the existing similar technology is only applicable to humidity measurement in a closed or static environment, and provides a method that can be applied to high-temperature flue gas humidity measurement in an open environment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of flue gas humidity measurement, and particularly relates to a sensor for online measurement of high-temperature flue gas humidity and a measurement method thereof. BACKGROUND

[0002] Currently, the flue gas humidity is generally measured by using a resistance-capacitance method humidity meter. In the working condition where the flue gas temperature is higher than 180℃, the capacitance method humidity sensor cannot be used because of insufficient temperature resistance, and cannot meet the needs of online measurement of flue gas humidity in the working condition where the flue gas temperature is higher than 180℃, and thus the problem of long-term online measurement of humidity in the high-temperature flue gas environment has not been completely solved. Therefore, it is an urgent need in the field of flue gas humidity measurement in the environmental protection industry to solve the flue gas humidity sensor required by the humidity measurement instrument in the working condition where the flue gas temperature is higher than 180℃, and to ensure that the flue gas humidity meter can long-term online measure the flue gas humidity parameter.

[0003] Another limit current oxygen sensor, commonly used in relatively clean measurement environment, such as "fumigation oven cavity humidity rapid detection device and method" (application publication number: CN106370711A, application date: August 29, 2016). Limit current oxygen sensor application technology development, also put the research focus on how to use single-chip microcomputer to limit current oxygen sensor signal acquisition processing, display and other circuit processing, such as "high temperature and humidity instrument and its measuring method" (authorized announcement number CN103543190B, application date: September 18, 2013) patent. These are relatively mature technology, with a limit current oxygen sensor to realize humidity measurement, seemingly feasible, in fact, there are two serious defects. The first defect is that the limit current oxygen sensor is divided into two categories, one only measures the oxygen content in the measured gas, and the other measures the oxygen content in the measured gas containing moisture, and the switching of the working voltage of the sensor directly leads to the ambiguity of the measurement results obtained by the sensor, because it cannot be determined whether the measurement results obtained before and after the switching of the working voltage contain moisture or have completely contained moisture. The sensor needs to be stable time, otherwise it cannot work stably. If the stable time is long, the measured gas is not the same, and if the stable time is short, the measurement value obtained by the sensor is meaningless. The second more serious defect is that the subtraction of the two measurement values has no practical significance, because the two measurements are not made at the same time. Therefore, the subtraction of the two physical quantities has no practical significance and cannot be related to the humidity of the measured gas (we can only consider that the measurement value described in the patent has physical significance in a closed space, because the humidity in the closed space will not change during the measurement period). It can be seen that the measurement data of the existing technology for dynamic gas in an open environment cannot be related to the actual humidity, and has no physical significance, so the data is naturally unreliable. The principle and method for measuring the humidity of waste flue gas in an open environment also have serious defects, and the products based on the existing technology also have serious defects. SUMMARY

[0004] 1. Technical problems to be solved by the invention

[0005] The present application mainly solves the problem of reliability of flue gas humidity measurement data. First, a humidity sensor suitable for online flue gas humidity measurement is constructed, which can reflect the actual flue gas humidity, i.e. the problem of measuring the dry basis oxygen content and the wet basis oxygen content of the same flue gas at the same time is solved.

[0006] Further, an oxygen sensor unit capable of measuring the oxygen content of flue gas at a temperature higher than 180℃ is constructed. The oxygen sensor unit can achieve real-time and dynamic protection conditions, so that the internal temperature of the oxygen sensor unit is very stable and is not easily affected by the fluctuations of the external open environment.

[0007] Further, to solve the data processing problem and obtain reliable humidity measurement value, the application provides a high-temperature flue gas humidity measurement method which can be applied to open environment flue gas humidity measurement.

[0008] 2. Technical solution

[0009] To achieve the above-mentioned purpose, the application adopts the technical solution of designing an online flue gas humidity sensor, which is mainly composed of a humidity sensor measurement cavity and a signal processing controller, wherein the humidity sensor measurement cavity has a flue gas inlet connected with a flue gas pipeline and a flue gas outlet; two oxygen sensor units are installed on the same flow cross section of the humidity sensor measurement cavity, which are a 1# oxygen sensor unit and a 2# oxygen sensor unit respectively. The 1# oxygen sensor unit measures the oxygen content of flue gas without water vapor, which is called dry basis oxygen content, and the 2# oxygen sensor unit measures the oxygen content of flue gas containing water vapor, which is called wet basis oxygen content. The signal processing controller is electrically connected with the oxygen sensor units.

[0010] Further, the heads of the 1# oxygen sensor unit and the 2# oxygen sensor unit are arranged oppositely, and are respectively installed on the left and right sides of the humidity sensor measurement cavity; they can also be installed in a vertical arrangement on the humidity sensor measurement cavity; or they can be installed side by side in the same direction on the same side of the humidity sensor measurement cavity.

[0011] Further, the oxygen sensor unit is composed of an oxygen sensor base, a limiting current oxygen sensor, a ring-shaped heat tracing element, a heat insulation sleeve, a dust blocking filter cover and a signal processing controller connected through a signal cable. The oxygen sensor base is a carrier of the limiting current oxygen sensor and the ring-shaped heat tracing element, the inner diameter of the ring-shaped heat tracing element is slightly larger than the outer diameter of the limiting current oxygen sensor, the ring-shaped heat tracing element is sleeved outside the limiting current oxygen sensor, and the two are in a basic gap-free assembly position relationship.

[0012] Further, there are 6 gold needles on the oxygen sensor base, 4 pins of the limiting current oxygen sensor are welded on the 4 gold needles near the center of the oxygen sensor base, and 2 pins of the ring-shaped heat tracing element are welded on the other 2 gold needles of the base. The gold needles are electrically connected with the signal processing controller through the signal cable.

[0013] Further, the ring-shaped heat tracing element is connected with the signal processing controller through the 2 gold needles on the base, and is driven by the condition protection control circuit on the mainboard to heat the limiting current oxygen sensor sleeved inside to reach the protection condition, thereby protecting the limiting current oxygen sensor in real time.

[0014] Further, the inner diameter of the heat insulation sleeve is slightly larger than the outer diameter of the annular heat tracing element, and the heat insulation sleeve is completely sleeved outside the annular heat tracing element, and the two are in a slightly gap assembly relationship, which blocks the direct contact and heat exchange between the annular heat tracing element and the external environment, and together with the annular heat tracing element, a small measuring environment of the limiting current oxygen sensor is formed, which is stable and controllable in temperature.

[0015] Further, the dust blocking filter cover is located between the limiting current oxygen sensor and the external environment, and is connected with the heat insulation sleeve in a threaded connection manner. The dust blocking filter cover effectively blocks the dust particles in the measured flue gas from entering and polluting the limiting current oxygen sensor, while the gas components and water vapor in the measured flue gas can enter the limiting current oxygen sensor, and the measuring signal of the limiting current oxygen sensor changes correspondingly.

[0016] Further, the limiting current oxygen sensor measuring signal and the monitoring signal of the annular heat tracing element are transmitted to the signal processing controller for processing through the signal cable connected to the 6 gold needles at the lower end of the oxygen sensor base.

[0017] The measurement method of the on-line flue gas humidity sensor is as follows: the measured flue gas enters the humidity sensor measuring cavity from the flue gas inlet, the 1# oxygen sensor unit detects the dry basis oxygen content (accurately, the oxygen content of the measured flue gas corresponds to a micro-current signal I d ). The I d signal is converted into the current oxygen content O 2d of the flue gas after being processed by the collection circuit, amplification circuit and MCU software program of the humidity sensor signal processing controller; at the same time, the 2# oxygen sensor unit detects the wet basis oxygen content of the measured flue gas containing flue gas moisture, and the 2# oxygen sensor unit is designed to output a micro-current signal I w corresponding to the oxygen content of the measured flue gas containing flue gas moisture, and the I w signal is converted into the oxygen content O 2w of the flue gas containing flue gas moisture after being processed by the collection circuit, amplification circuit and MCU software program of the humidity sensor signal processing controller. The difference (ΔO2) between O 2w and O 2d represents the current moisture content of the flue gas.

[0018] The logarithm of the oxygen content O 2d of the flue gas and the corresponding micro-current signal I d are in a linear function relationship, and the simplified function expression with I d as the independent variable is: O 2d =(1–e (-Id / k)x 100, wherein k is a sensor constant coefficient, O 2d is the oxygen content of flue gas, I d is the micro-current signal of the oxygen sensor.

[0019] the oxygen content O 2w is the logarithm of the corresponding micro-current signal I w is a linear function, and the simplified function expression with I w as the independent variable is: O 2w = (1 - e (-Iw / k) )x 100, wherein k is a sensor constant coefficient, O 2w is the oxygen content of flue gas containing flue gas moisture in the flue gas, I w is the micro-current signal of the oxygen sensor corresponding thereto.

[0020] The change amount of ΔO2 and the change of flue gas humidity are in a linear function relationship, according to the standard HJ-76 of the Ministry of Environmental Protection, the flue gas humidity is represented by X sw , then the linear function relationship is represented as: X sw =A*ΔO2+B, wherein A is a slope constant, which is generated when the humidity sensor is calibrated, B is a pitch constant, which is also generated when the humidity sensor is calibrated, and is usually a constant very close to zero, and the conversion of the above function relationship is realized by the MCU software program of the humidity sensor signal processing controller, and finally the real-time measurement value of the flue gas humidity is obtained.

[0021] During the measurement process, the oxygen sensor unit is driven by the condition protection circuit on the humidity sensor signal processing controller to work the annular heat tracing unit in the oxygen sensor unit, to track the internal temperature of the limiting current oxygen sensor in real time, and whether the protection condition is reached is judged by the MCU program on the mainboard in real time.

[0022] 3. Beneficial effects

[0023] The technical scheme provided by the present application has the following beneficial effects:

[0024] (1) By the method for constructing a humidity sensor provided by the present application, two oxygen sensor units based on limiting current oxygen sensors located in the same laminar cross section are constructed, the dry basis oxygen content and the wet basis oxygen content of the flue gas of the same laminar cross section are measured at the same time, the instantaneous flue gas humidity is obtained after data processing, and the online measurement of flue gas humidity based on the limiting current principle is realized. The measurement environment of flue gas humidity is an open environment for the flue gas humidity sensor, the flue gas flow is large, and the real-time change of flue gas humidity is fast. By using the method described in the present application, the instantaneous online measurement of flue gas humidity is realized, the measurement data comes from the same flue gas, the same time, and the same laminar surface cross section, and the data reliability is high.

[0025] (2) The method for constructing the oxygen sensor unit of the present application is based on the measurement of flue gas humidity in such an open environment, and can work under the condition that the flue gas temperature is higher than 180℃. The corrosiveness and dust pollution of high-temperature flue gas to the sensor and the service life are fully considered, and a ring-shaped heat tracing element and a heat insulation sleeve are added in the structural design, and a condition protection circuit and an MCU program on the mainboard are added in the implementation method to realize real-time tracking and control of the protection condition by the MCU program on the mainboard, so that the internal temperature of the oxygen sensor unit is very stable and is not affected by the fluctuations of the external open environment, and the damage of the limiting current oxygen sensor caused by this factor is avoided.

[0026] (3) The measurement method of the sensor for measuring the flue gas humidity on-line solves the problem of the serious influence of the measurement environment on the sensor when measuring the flue gas humidity in such an open environment, and realizes the on-line measurement of the flue gas humidity. At the same time, the flue gas humidity and the oxygen content of the flue gas at the same time are measured, and the flue gas humidity data is directly obtained through the processing of the humidity sensor signal processing controller, so that the measurement efficiency is improved, and the measurement cost of simultaneously collecting the flue gas humidity and the oxygen content of the flue gas data is reduced. The characteristics of one measurement can output two flue gas parameters of the flue gas humidity and the oxygen content of the flue gas. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a schematic diagram of the exploded structure of the oxygen sensor unit of the present application;

[0028] Figure 2 It is a schematic diagram of the combined structure of the oxygen sensor unit of the present application;

[0029] Figure 3 It is a schematic diagram of the cross-sectional structure of the oxygen sensor unit of the present application;

[0030] Figure 4 It is a schematic diagram of the structure of the humidity sensor of the present application;

[0031] Figure 5 It is a schematic diagram of the cross-sectional structure of the humidity sensor of the present application.

[0032] Explanation of the reference numerals in the schematic diagram: oxygen sensor unit 100, 1# oxygen sensor unit 1001, 2# oxygen sensor unit 1002, humidity sensor measurement cavity 200, flue gas inlet 201, flue gas outlet 202, signal processing controller 203, oxygen sensor base 101, limiting current oxygen sensor 102, ring-shaped heat tracing element 103, heat insulation sleeve 104, dust blocking filter cover 105, signal cable lock head 106. DETAILED DESCRIPTION

[0033] In order to further understand the content of the present application, the present application is described in detail in combination with the drawings and examples.

[0034] The structure, proportion, size and the like shown in the drawings of the specification are only used to cooperate with the content disclosed in the specification, to be understood and read by those skilled in the art, and are not used to limit the defined conditions that the present application can be implemented, so they do not have technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effect and purpose that the present application can produce, should still fall within the scope covered by the disclosed technology.

[0035] Embodiment 1

[0036] The limit current oxygen sensor based on high-temperature solid electrolyte can realize the measurement of oxygen content in high-temperature gas, and has been used to measure oxygen content in high-temperature environment such as vehicle exhaust. Further research found that water vapor contained in high-temperature gas has an effect on the limit current oxygen sensor, and it is understood that the amount of water vapor contained in high-temperature gas is related to the output signal of the oxygen sensor. This correlation makes it possible to construct a humidity sensor based on the principle of limit current oxygen sensor suitable for measuring humidity in high-temperature environment. Therefore, the present application develops and researches a sensor that can measure flue gas humidity on a long-term basis under the working condition that the flue gas temperature is higher than 180℃ (but lower than 300℃) based on the limit current flue gas humidity sensor.

[0037] The first step of the present application is to construct an oxygen sensor unit that can be applied to online flue gas humidity measurement. The oxygen sensor unit includes an oxygen sensor base, a limit current oxygen sensor, an annular heat tracing element, a heat insulation sleeve, a dust blocking filter cover, a signal cable lock head, and a signal cable connected to the humidity sensor mainboard. The oxygen sensor base is a common carrier of the limit current oxygen sensor and the annular heat tracing element. The inner diameter of the annular heat tracing element is slightly larger than the outer diameter of the limit current oxygen sensor, and the annular heat tracing element is sleeved outside the limit current oxygen sensor. There are 6 gold needles on the oxygen sensor base. The 4 pins of the limit current oxygen sensor are welded to the 4 gold needles near the center of the base, and the 2 pins of the annular heat tracing element are welded to the other 2 gold needles of the base. The inner diameter of the heat insulation sleeve is slightly larger than the outer diameter of the annular heat tracing element, and it is sleeved outside the annular heat tracing element, blocking the direct heat exchange between the annular heat tracing element and the external environment, playing a role in heat preservation and stabilizing the internal temperature. Then the dust blocking filter cover is fixed on the heat insulation sleeve in a thread connection manner, isolating the smoke dust particles in the flue gas and preventing the pollution of the sensor by the smoke dust particles. Finally, the signal cable connected to the 6 gold needles at the bottom of the base is connected to the humidity sensor mainboard through the signal cable lock head.

[0038] The second step of this invention is to construct a humidity sensor suitable for online measurement of flue gas humidity in high-temperature flue gas. The humidity sensor comprises a #1 oxygen sensor unit, a humidity sensor measurement chamber, a #2 oxygen sensor unit, a flue gas inlet, a flue gas outlet, an internal space within the measurement chamber, and a signal processing controller, using a pair of oxygen sensor units with their sensor heads facing each other. The #1 oxygen sensor unit is threadedly connected to the left side of the humidity sensor measurement chamber, and the #2 oxygen sensor unit is threadedly connected to the right side of the humidity sensor measurement chamber. Furthermore, the humidity sensor measurement chamber is designed with a flue gas inlet and a flue gas outlet at its upper and lower parts, structurally designed so that the flue gas being measured passes through these two oxygen sensor units simultaneously, or in other words, the flue gas measured by these two oxygen sensor units is the flue gas at the same moment. For better understanding, the functions of these two oxygen sensor units are categorized and described as follows: The #1 oxygen sensor unit is designed to only measure the oxygen content of the output flue gas; that is, the #1 oxygen sensor unit is defined as the oxygen content of the output flue gas (in O2). 2d (Indicated); The #2 oxygen sensor unit is designed to measure only the oxygen content, including moisture in the output flue gas. That is, the #2 oxygen sensor unit is defined as the output oxygen content including moisture in the flue gas (in O...). 2w (This is indicated by the text). The above classification is crucial, giving the subtraction of the measurements from these two oxygen sensor units a clear physical meaning and clearly distinguishing it from existing technologies. When the flue gas being measured enters the measuring chamber from the flue gas inlet, it simultaneously passes through both oxygen sensor unit #1 and oxygen sensor unit #2. The measurement value from oxygen sensor unit #1 is the oxygen content of the flue gas (expressed as O2). 2d (Indicated), the measured value of oxygen sensor unit #2 includes the oxygen content (in O2), which is the amount of moisture in the flue gas. 2w (represented), the difference between the two (O) 2w -O 2d ) using Δ O2 It means, i.e., Δ O2 =O 2w -O 2d Δ O2 The change in flue gas humidity is a linear function f(Δ) O2 ).

[0039] The third step of this invention is to transform the linear function f(Δ) from the second step... O2 The relationship is realized through a signal processing controller connected to a humidity sensor to measure the humidity of the flue gas; at the same time, the measured value of the oxygen sensor unit #1 of the flue gas is O 2d The measured value of O from oxygen sensor unit #2 2wThe current flue gas humidity real-time measurement value is obtained by converting the linear function f(Δ O2 ) relationship of the hardware units on the condition protection control circuit, data acquisition circuit, signal amplification circuit, PWM constant temperature control circuit, voltage / current conversion circuit, 232 / 485 data communication circuit and other hardware units on the signal processing controller and the MCU program.

[0040] Further, the application occasion of the present application is environmental protection waste gas emission. In addition to water vapor, the waste flue gas also contains smoke dust particles and SO2, NOx and other corrosive gas components. The measurement environment is harsh, and sufficient smoke blocking device and corrosion prevention method must be designed to realize long-term online measurement of flue gas humidity. The present application focuses on solving the humidity measurement in open environment, especially the humidity measurement in harsh measurement environment (high temperature flue gas). First, the method for measuring humidity (especially flue gas humidity) in open environment is proposed based on the characteristics of the limiting current oxygen sensor, which can measure in high temperature environment and has certain correlation with humidity. Second, the structure is provided to quickly reach the protection condition and stabilize the internal temperature of the sensor to minimize the influence of temperature fluctuation in the use environment on the service life of the sensor.

[0041] In combination Figures 1-5 , the flue gas humidity sensor of the present application mainly comprises a 1# oxygen sensor unit 1001, a 2# oxygen sensor unit 1002, a humidity sensor measurement cavity 200, a flue gas inlet 201, a flue gas outlet 202 and a signal processing controller 203 connected by a signal cable.

[0042] As Figure 5As shown, the head parts of the 1# oxygen sensor unit 1001 and the 2# oxygen sensor unit 1002 are arranged oppositely, and are respectively installed on the left and right sides of the humidity sensor measuring cavity 200, as the first preferred mode. By properly adjusting the size of the humidity sensor measuring cavity 200, the 1# oxygen sensor unit 1001 and the 2# oxygen sensor unit 1002 are installed side by side and in the same direction on the same side of the humidity sensor measuring cavity 200, as the second installation mode. By further adjusting the size of the humidity sensor measuring cavity, the 1# oxygen sensor unit 1001 and the 2# oxygen sensor unit 1002 are installed in a perpendicular arrangement on the humidity sensor measuring cavity 200, as the third installation mode. In the above three installation modes, the head parts of the 1# oxygen sensor unit 1001 and the 2# oxygen sensor unit 1002 are located on the same flow cross section of the humidity sensor measuring cavity 200. All of them can achieve the purpose of measuring the same moment of flue gas by the 1# oxygen sensor unit 1001 and the 2# oxygen sensor unit 1002, which is one of the important links of the present application distinguishing from other technologies in the field of flue gas humidity measurement. The position structure of the two oxygen sensor units 100 specified in this link determines that the two oxygen sensor units 100 measure the oxygen content of the same moment of flue gas, and the functional difference of the two oxygen sensor units 100 determines that the 1# oxygen sensor unit 1001 measures the oxygen content of the current flue gas, and the 2# oxygen sensor unit 1002 measures the oxygen content of the current flue gas containing the water content of the flue gas, so as to determine the physical meaning of the value obtained by subtracting the two values, that is, it represents the current flue gas humidity. It is completely applicable to the measurement of gas humidity in an open measurement environment or in a flowing state, such as humidity measurement in the field of flue gas humidity measurement, and is also applicable to humidity measurement in a closed measurement environment. Most importantly, there is no fundamental defect of theoretically meaningless physical quantity.

[0043] The flue gas humidity sensor, as shown in Figure 4 As shown, the head parts of the 1# oxygen sensor unit 1001 and the 2# oxygen sensor unit 1002 are arranged oppositely, and are respectively installed on the left and right sides of the humidity sensor measuring cavity 200, as the first preferred mode. By properly adjusting the size of the humidity sensor measuring cavity 200, the 1# oxygen sensor unit 1001 and the 2# oxygen sensor unit 1002 are installed side by side and in the same direction on the same side of the humidity sensor measuring cavity 200, as the second installation mode. By further adjusting the size of the humidity sensor measuring cavity, the 1# oxygen sensor unit 1001 and the 2# oxygen sensor unit 1002 are installed in a perpendicular arrangement on the humidity sensor measuring cavity 200, as the third installation mode. In the above three installation modes, the head parts of the 1# oxygen sensor unit 1001 and the 2# oxygen sensor unit 1002 are located on the same flow cross section of the humidity sensor measuring cavity 200. All of them can achieve the purpose of measuring the same moment of flue gas by the 1# oxygen sensor unit 1001 and the 2# oxygen sensor unit 1002, which is one of the important links of the present application distinguishing from other technologies in the field of flue gas humidity measurement. The position structure of the two oxygen sensor units 100 specified in this link determines that the two oxygen sensor units 100 measure the oxygen content of the same moment of flue gas, and the functional difference of the two oxygen sensor units 100 determines that the 1# oxygen sensor unit 1001 measures the oxygen content of the current flue gas, and the 2# oxygen sensor unit 1002 measures the oxygen content of the current flue gas containing the water content of the flue gas, so as to determine the physical meaning of the value obtained by subtracting the two values, that is, it represents the current flue gas humidity. It is completely applicable to the measurement of gas humidity in an open measurement environment or in a flowing state, such as humidity measurement in the field of flue gas humidity measurement, and is also applicable to humidity measurement in a closed measurement environment. Most importantly, there is no fundamental defect of theoretically meaningless physical quantity.

[0044] Example 2

[0045] As shown in Figure 1 , Figure 5The oxygen sensor unit 100 is composed of an oxygen sensor base 101, a limiting current oxygen sensor 102, a ring-shaped heating element 103, a heat insulation sleeve 104, a dustproof filter cover 105, a signal cable lock head 106, and a signal cable connected with the signal processing controller 203 of the humidity sensor.

[0046] The oxygen sensor base 101 is a carrier of the limiting current oxygen sensor 102 and the ring-shaped heating element 103. The inner diameter of the ring-shaped heating element 103 is slightly larger than the outer diameter of the limiting current oxygen sensor 102. The ring-shaped heating element 103 is completely sleeved outside the limiting current oxygen sensor 102, and the assembly position relationship between them is basically without gap. The oxygen sensor base 101 has six gold needles. Four pins of the limiting current oxygen sensor 102 are welded on the four gold needles near the center of the oxygen sensor base 101. The structure position of 101, 102 and 103 is shown in Figure 3 The ring-shaped heating element 103 is connected with the signal processing controller 203 through two gold needles on the base 101, and is driven by the condition protection control circuit on the mainboard of the signal processing controller 203. The limiting current oxygen sensor inside the ring-shaped heating element 103 can be rapidly heated to reach the protection condition. The time is fast enough, only tens of seconds, usually not more than 1 minute, to reach the protection condition, which plays the effect of real-time protection of the limiting current oxygen sensor 102.

[0047] The inner diameter of the heat insulation sleeve 104 of the oxygen sensor unit is slightly larger than the outer diameter of the ring-shaped heating element 103, and is completely sleeved outside the ring-shaped heating element 103. The assembly relationship between them is with a little gap, which blocks the direct contact and heat exchange between the ring-shaped heating element 103 and the external environment, and together with the ring-shaped heating element 103 forms a temperature stable and controllable measuring small environment for the limiting current oxygen sensor 102. For the limiting current oxygen sensor 102 completely sleeved inside, this small environment is a temperature stable measuring small environment with pre-set protection condition. This is the second important innovation point of the application.

[0048] The dustproof filter cover 105 of the oxygen sensor unit is connected with the heat insulation sleeve 104 in a threaded manner. The dustproof filter cover 105 effectively blocks the dust particles in the measured flue gas from entering the limiting current oxygen sensor 102 to contaminate the limiting current oxygen sensor 102. At the same time, the gas components and water vapor in the measured flue gas can enter the limiting current oxygen sensor 102, and the measurement signal of the limiting current oxygen sensor 102 changes accordingly. The measurement signal of the limiting current oxygen sensor 102 and the control signal of the annular heat tracing element 103 are transmitted to the signal processing controller 203 through the signal cable connected to the 6 gold needles at the lower end of the oxygen sensor base. The signal processing controller 203 feeds back the control signal to the annular heat tracing element 103. The signal cable lock head 106 fixes the input and output signal lines.

[0049] Example 3

[0050] The measurement signal processing method is as follows: when the measured flue gas enters the internal space of the measuring cavity from the inlet, the 1# oxygen sensor unit 1001 detects the oxygen content of the measured flue gas (to be precise, the oxygen content of the measured flue gas corresponds to the micro-current signal I d . The I d signal is processed by the collection circuit, amplification circuit, MCU software program, etc. of the humidity sensor signal processing controller 203 and converted into the oxygen content O 2d of the flue gas at the current time. The relationship between the two is that the logarithm of the oxygen content O 2d of the flue gas and the corresponding micro-current signal I d are linearly related. The simplified function expression with I d as the independent variable is: O 2d =(1–e (-Id / k) ) x 100, where k is the sensor constant coefficient, O 2d is the oxygen content of the flue gas, and I d is the micro-current signal of the oxygen sensor. At the same time, the 2# oxygen sensor unit 1002 detects the oxygen content of the measured flue gas including the water content of the flue gas (in accordance with the previous definition, the 2# oxygen sensor unit 1002 is designed to output the micro-current signal I w corresponding to the oxygen content of the measured flue gas including the water content of the flue gas. The I w signal is processed by the collection circuit, amplification circuit, MCU software program, etc. of the humidity sensor signal processing controller 203 and converted into the oxygen content O 2w of the flue gas including the water content of the flue gas at the current time. The relationship between the two is also that the logarithm of the oxygen content O 2w and the corresponding micro-current signal I w are linearly related. The simplified function expression with I w as the independent variable is: O 2w =(1–e (-Iw / k))x 100, where k is the sensor constant coefficient, O 2w I represents the oxygen content in the flue gas, including its moisture content. w This is the microcurrent signal from the corresponding oxygen sensor. Thus, we obtained the current oxygen content (O2) of the flue gas at the same time using oxygen sensor unit 1#1001 and oxygen sensor unit 1#2. 2d And the current oxygen content (O2) in the flue gas, including the moisture content. 2w , use O 2w Subtract O 2d The resulting difference (ΔO2) represents the current moisture content of the flue gas. The change in ΔO2 has a linear functional relationship with the change in flue gas humidity. According to the Ministry of Environmental Protection standard HJ-76, flue gas humidity is represented by X... sw If we express this as X, then the above linear functional relationship can be expressed as: sw =A*ΔO2+B, where A is the slope constant, generated during humidity sensor calibration, and B is the pitch constant, also generated during humidity sensor calibration, which is usually a constant very close to zero (generally negligible). The conversion of the above functional relationship is implemented by the MCU software program of the humidity sensor signal processing controller 203, and finally obtains the real-time measurement value of flue gas humidity.

[0051] This invention relates to a flue gas humidity sensor that can simultaneously output the current flue gas humidity and oxygen content in a single measurement. The method involves the coordinated operation of oxygen sensor unit 1001 and oxygen sensor unit 1002, with the flue gas humidity obtained via a humidity sensor signal processing controller 203. During this process, the measured value O from oxygen sensor unit 1 is also obtained. 2d This value represents the current oxygen content of the flue gas. Therefore, a single measurement can output the current flue gas humidity value X. sw and flue gas oxygen content value O 2d .

[0052] The flue gas humidity meter sensor of this invention, specifically oxygen sensor unit 1# 1001 and oxygen sensor unit 1# 1002, are both oxygen sensor units suitable for flue gas humidity measurement as described above, rather than directly limiting current oxygen sensors. This is emphasized because the application field of this invention is flue gas humidity measurement, and the measurement environment is an open environment for the flue gas humidity sensor. Large and fluctuating flue gas flow rates and temperatures directly lead to frequent damage to the limiting current oxygen sensor. The oxygen sensor unit described in this invention is driven by a condition protection circuit on the humidity sensor signal processing controller 203, which operates the ring-shaped heat tracing unit within the oxygen sensor unit to track the internal temperature of the oxygen sensor unit in real time. The MCU program on the main board determines in real time whether the protection condition has been reached.

[0053] The above describes the present application and its embodiments in a schematic manner, and the description is not restrictive, and the embodiments shown in the drawings are only one of the embodiments of the present application, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by the above, without departing from the spirit of the present application, similar structural modes and embodiments can be designed without creativity, and all of them shall belong to the protection scope of the present application.

Claims

1. A sensor for measuring humidity of high-temperature flue gas on-line, mainly comprising a humidity sensor measuring cavity (200) and a signal processing controller (203), characterized in that: the humidity sensor measuring cavity (200) has a flue gas inlet (201) and a flue gas outlet (202) connected to a flue gas pipeline; two oxygen sensor units (100) are installed in the same cross section of the humidity sensor measuring cavity (200), which are a 1# oxygen sensor unit (1001) and a 2# oxygen sensor unit (1002); the 1# oxygen sensor unit (1001) measures dry basis oxygen content of flue gas, and the 2# oxygen sensor unit (1002) measures wet basis oxygen content of flue gas; the signal processing controller (203) is electrically connected to the oxygen sensor units (100); the head of the 1# oxygen sensor unit (1001) is arranged opposite to the head of the 2# oxygen sensor unit (1002), and they are respectively installed on the left and right sides of the humidity sensor measuring cavity (200); the oxygen sensor unit (100) is composed of an oxygen sensor base (101), a limiting current oxygen sensor (102), a ring-shaped heat tracing element (103), a heat insulation sleeve (104), a dustproof filter cover (105) and a signal processing controller (203) connected through a signal cable; the oxygen sensor base (101) is a carrier of the limiting current oxygen sensor (102) and the ring-shaped heat tracing element (103), the inner diameter of the ring-shaped heat tracing element (103) is slightly larger than the outer diameter of the limiting current oxygen sensor (102), the ring-shaped heat tracing element (103) is sleeved outside the limiting current oxygen sensor (102), and the two are assembled with substantially no gap therebetween. Six gold pins are provided on the oxygen sensor base (101), four pins of the limiting current oxygen sensor (102) are welded on the four gold pins close to the center of the oxygen sensor base (101), and two pins of the ring-shaped heat tracing element (103) are welded on the other two gold pins of the base; the gold pins are electrically connected to the signal processing controller (203). The ring-shaped heat tracing element (103) is connected to the signal processing controller (203) through the two gold pins on the base, and is driven by a condition protection control circuit on the mainboard of the signal processing controller (203) to heat the limiting current oxygen sensor (102) sleeved inside to reach a protection condition, thereby protecting the limiting current oxygen sensor (102) in real time. The heat insulation sleeve (104) has an inner diameter slightly larger than the outer diameter of the ring-shaped heat tracing element (103), and is completely sleeved outside the ring-shaped heat tracing element (103), thereby blocking direct contact and heat exchange between the ring-shaped heat tracing element (103) and the external environment, and together with the ring-shaped heat tracing element (103) forming a measuring small environment capable of protecting the limiting current oxygen sensor (102) and being temperature stable and controllable. ​ ​ ​ 2. The sensor of claim 1, wherein: ​ 3. The sensor of claim 2, wherein: ​ 4. The sensor of claim 1, wherein: ​ 5. The sensor of claim 1, wherein: The dustproof filter cover (105) is located between the limiting current oxygen sensor (102) and the external environment, and is connected with the heat insulation sleeve (104) in a threaded connection manner. The dustproof filter cover (105) effectively blocks dust particles in the measured flue gas from entering and polluting the limiting current oxygen sensor (102), while the gas components and water vapor in the measured flue gas can enter the limiting current oxygen sensor (102), and the measurement signal of the limiting current oxygen sensor (102) changes correspondingly.

6. The sensor of claim 2, wherein: The measurement signal of the limiting current oxygen sensor (102) and the monitoring signal of the annular heat tracing element (103) are transmitted to the signal processing controller (203) for processing through the signal cable connected to the lower end of the oxygen sensor base by 6 gold needles.

7. The method according to any one of claims 1 to 6, wherein the sensor is an on-line sensor for measuring the humidity of high-temperature flue gas. The measured flue gas enters the humidity sensor measurement cavity (200) from the flue gas inlet (201), and the 1# oxygen sensor unit (1001) and the 2# oxygen sensor unit (1002) simultaneously detect the oxygen content of the flue gas, and the real-time moisture content is obtained according to the difference.

8. The method of measuring according to claim 7, wherein: The #1 oxygen sensor unit (1001) detects the microcurrent signal I corresponding to the oxygen content of the dry basis of the measured flue gas. d , the I d The signal is processed by the humidity sensor signal processing controller (203) and converted into the current dry basis oxygen content (O2) of the flue gas. 2d The #2 oxygen sensor unit (1002) is designed to detect the microcurrent signal I corresponding to the oxygen content, including moisture, in the tested flue gas. w , the I w The signal is processed by the humidity sensor signal processing controller (203) and converted into the wet-based oxygen content (O2) of the flue gas, including the moisture content of the flue gas, at the current moment. 2w , use O 2w Subtract O 2d The difference (ΔO2) represents the moisture content of the flue gas under real-time conditions.

9. The method of measuring according to claim 8, wherein: During the measurement process, the oxygen sensor unit (100) drives the annular heat tracing element (103) in the oxygen sensor unit to work through the condition protection circuit on the humidity sensor signal processing controller (203), and real-time tracks the internal temperature of the limiting current oxygen sensor (102), and whether the protection condition is reached is judged by the MCU program on the mainboard in real time.

Images