JP4091571B2 - Calorific value calculation formula generation unit, calorific value calculation device, and calorific value measurement system - Google Patents

Description

  The present invention relates to a calorific value calculation formula generation unit that generates a calorific value calculation formula for calculating a calorific value of a mixed gas based on a sensor output of a catalytic combustion gas sensor, and based on a sensor output output from a catalytic combustion gas sensor. The present invention relates to a calorific value calculation device that calculates the calorific value of a mixed gas, and a calorific value measurement system including the calorific value calculation device.

  As for the raw material of city gas, the transition to liquefied natural gas (hereinafter referred to as LNG) that can be imported from a conventional petroleum system at a stable price for a long time has steadily progressed, and most of the city gas raw material has become LNG nationwide. ing. In addition, local city gas operators are making a switch to LNG.

The method of supplying LNG as city gas is basically the same in large cities and small and medium-sized cities. After gasifying with an air temperature or seawater heating type vaporizer, about 46 MJ with liquefied propane gas (LPG). / Nm ³ is adjusted to increase heat and supplied as high calorie gas. The calorific value of the supply gas is calculated by measuring the gas component and the concentration contained in the mixed gas using a gas chromatograph.

  Here, in the gas chromatograph, a gas sample, a vaporized liquid, and a solid sample are developed with a carrier gas in a column uniformly packed with an appropriate packing, and the sample is allowed to pass in a gaseous state without being chemically changed. An apparatus for separating components.

  A thermal conductivity type (Thermal conductivity detector, TCD) is used in a general gas chromatograph detector, which utilizes the difference in thermal conductivity of gas and detects the difference in electrical resistance of the thermistor. Characteristically, the structure is simple and anything other than the carrier gas can be detected, but there is a drawback that the sensitivity is low.

In addition, a gas chromatograph has been proposed in which a minimum detection amount is small and measurement with good reproducibility is possible. According to this gas chromatograph, a TCD having a small volume is used, and one end of the capillary column is arranged in the TCD, so that the dead volume between the capillary column and the TCD is substantially eliminated, thereby enabling the TCD. The flow rate of the same kind of gas as the carrier gas to be supplied is reduced, the minimum detection amount is small, and measurement with good reproducibility is possible (see Patent Document 1).
JP 2002-228647 A (page 3-4, FIG. 1)

  However, since the above-described gas chromatograph is expensive, when the calorific value of the supply gas is measured by the gas chromatograph, there is a problem that the measurement is expensive. In addition, since a gas chromatograph uses a column such as a capillary column, only a discontinuous measurement can be performed every 10 to 30 minutes, which causes a problem that it takes time to measure a calorific value.

  By the way, since the catalytic combustion type gas sensor uses a combustion reaction of gas, an output proportional to the calorific value is theoretically obtained. Therefore, the sensor output and the calorific value of the catalytic combustion type gas sensor for hydrocarbon gas are obtained. Therefore, the calorific value of the mixed gas can be continuously measured with a simple and inexpensive configuration without using a gas chromatograph by using a well-known catalytic combustion type gas sensor.

FIG. 14 is a graph showing the relationship between the sensor output of the catalytic combustion type gas sensor and the calorific value for each gas component, in which the vertical axis represents the sensor output (mV) and the horizontal axis represents the combustion heat (MJ / Nm ³ ). Each is shown. A graph G1 in FIG. 14 is an approximate straight line for methane, ethane, propane, butane, and pentane, which are components of LNG, and the calorific value for the sensor output can be calculated from the graph G1.

  However, since the intercept of the graph G1 is not 0, that is, the graph G1 in FIG. 14 does not pass through the origin, when the calorific value is calculated based on this graph G1, there is no effect in the region where the calorific value is higher than that of methane. However, there is a problem that the error increases in a region below that. In particular, since the calorific value of nonflammable gas is 0, if a nonflammable gas such as nitrogen is mixed in a hydrocarbon-based mixed gas whose component ratio, component composition, etc. are unknown, an error in the calorific value to be calculated Could be bigger.

  Therefore, in view of the above-described problems, the present invention provides a calorific value calculation formula generation unit, a calorific value calculation device, and a calorific value measurement system that can accurately and inexpensively measure the calorific value of a hydrocarbon-based mixed gas. It is an issue.

  In order to solve the above problems, the calorific value calculation formula generation unit according to claim 1 made according to the present invention comprises a detection element sensitive to a test substance in a test gas, as shown in a basic configuration diagram of FIG. Based on a sensor output indicating a thermal balance between the detection element and the comparison element output from the catalytic combustion gas sensor 10 having a comparison element that is insensitive to the test substance in the test gas, a plurality of types of gas components are used. A calorific value calculation formula generation unit that generates a calorific value calculation formula for calculating the calorific value of the mixed gas, and is a drive control that controls the driving of the catalytic combustion gas sensor 10 by switching to a desired sensor driving temperature. The calorific value of the gas component corresponding to the sensor output outputted by the means 21a and the catalytic combustion type gas sensor 10 corresponds to the sensor driving temperature of the catalytic combustion type gas sensor 10. The calorific value specifying information storage means 34 for storing the calorific value specifying information that can be specified in this manner, and the sensor output output by the catalytic combustion gas sensor 10 for the plurality of types of gas components are output from the catalytic combustion gas sensor 10. Sensor output collecting means 31a11 that collects in correspondence with the sensor driving temperature, and the heat generation amount that the heat generation amount corresponding to the sensor output collected by the sensor output collection means 31a11 is stored in the heat generation amount specifying information 34 An identification unit 31a12 that is identified based on information, and a linear expression that indicates the relationship between the sensor output collected by the sensor output collection unit 31a11 and the amount of heat generated by the identification unit 31a12, corresponding to the sensor driving temperature. Calculating means 31a13, and the intercept of the linear expression among the linear expressions calculated by the calculating means 31a13 is zero. Further, based on the extraction unit 31a14 for extracting a linear equation near zero and the linear equation extracted by the extraction unit 31a14, the mixed gas is calculated from the sensor output corresponding to the mixed gas output by the catalytic combustion gas sensor 10. A calorific value calculation formula generating unit 31a15 that generates a calorific value calculation formula for calculating the calorific value, and the generation of the calorific value calculation formula by the calorific value calculation formula generating unit 31a15 correspond to the calorific value calculation formula. The sensor drive temperature includes a mixed gas measurement temperature specifying means 31a16 for specifying the mixed gas measurement temperature for driving the catalytic combustion gas sensor 10 when measuring the calorific value of the mixed gas.

  According to the calorific value calculation formula generation unit of the present invention described in claim 1 above, when the catalytic combustion type gas sensor 10 is driven by being switched to a desired sensor drive temperature by the control by the drive control means 21a, a plurality of types of calorific value calculation formula generation unit are provided. The sensor output output from the catalytic combustion type gas sensor 10 for the gas component is collected by the sensor output collecting means 31a11 in correspondence with the sensor driving temperature. Then, the heat generation amount corresponding to the collected sensor output is specified by the specifying unit 31a12 based on the heat generation amount specifying information stored in the heat generation amount specifying information 34, and shows the relationship between the heat generation amount and the sensor output. A linear equation is calculated by the calculation means 31a13 corresponding to the sensor driving temperature. Then, when the extraction unit 31a14 extracts a linear equation having zero or near zero from the linear equation corresponding to the sensor driving temperature, the calorific value calculation equation is calculated based on the linear equation. The sensor driving temperature generated by the generating unit 31a15 and corresponding to the calorific value calculation formula is specified by the mixed gas measurement temperature specifying unit 31a16 as the mixed gas measurement temperature.

  In order to solve the above-mentioned problem, the invention according to claim 2 is that, as shown in the basic configuration diagram of FIG. 1, in the calorific value calculation formula generation unit according to claim 1, the extraction means 31 a 14 has the linear formula. When the sensor cannot be extracted, the sensor drive temperature that makes the intercept zero or near zero is estimated based on each linear equation intercept calculated by the calculation means 31a13 and the sensor drive temperature corresponding to the intercept. An estimation unit 31a17 is further provided, and the drive control unit 21a performs the control at the sensor driving temperature estimated by the estimation unit 31a17.

  According to the calorific value calculation formula generation unit of the present invention described in claim 2, if the linear formula is not extracted by the extraction means 31a14, the intercept of each calculation formula calculated by the calculation means 31a13 and the sensor corresponding to the intercept Based on the drive temperature, the sensor drive temperature that makes the intercept zero or near zero is estimated by the estimation means 31a17. When the drive of the catalytic combustion type gas sensor 10 is controlled by the drive control means 21a based on the estimated driving temperature, the sensor output output from the catalytic combustion type gas sensor 10 is collected by the sensor output collecting means 31a11, and the calorific value thereof. Is specified by the specifying means 31a12, and a linear expression indicating the relationship between the calorific value and the sensor output is calculated by the calculating means 31a13 corresponding to the sensor driving temperature.

  In order to solve the above problems, the calorific value calculation device according to claim 3 according to the present invention includes a detection element sensitive to a test substance in a test gas and the test target as shown in a basic configuration diagram of FIG. 3. A sensor output indicating a thermal balance between the detection element and the comparison element output from the catalytic combustion gas sensor 10 having a comparison element that is insensitive to a test substance in the gas, and a calorific value according to claim 1 or 2. A calorific value calculation device for calculating a calorific value of a mixed gas composed of a plurality of types of gas components based on a calorific value calculation formula generated by the calculation formula generation unit 300, comprising: mixing of the calorific value calculation formula generation unit 300 The mixed gas drive control means 21b for controlling the driving of the catalytic combustion gas sensor 10 at the mixed gas measured temperature specified by the gas measured temperature specifying means 31a16, and the mixed gas drive control Sensor output capturing means 31a21 that captures the sensor output corresponding to the mixed gas output by the catalytic combustion gas sensor 10 according to the control of the stage 21b, sensor output captured by the sensor output capturing means 31a21, and the sensor output Based on the heat generation amount calculation formula generated by the heat generation amount calculation formula generation means 31a15 of the heat generation amount calculation formula generation unit 300, the heat generation amount calculation means 31a22 that calculates the heat generation amount, and the heat generation calculated by the heat generation amount calculation means 31a22 And a calorific value information output means 31a23 for outputting in order to notify the calorific value information indicating the quantity.

  According to the calorific value calculation device of the present invention described in claim 3, when the calorific value of the mixed gas is calculated, the mixed gas measurement temperature specified by the mixed gas measurement temperature specifying means 31a16 of the calorific value calculation formula generation unit is determined. The driving of the contact combustion type gas sensor 10 is controlled by the mixed gas drive control means 21b. The sensor output corresponding to the mixed gas output from the catalytic combustion type gas sensor 10 is captured by the sensor output capturing means 31a21, and the sensor output and the calorific value calculation formula generating means 31a15 of the calorific value calculation formula generating unit 300 are generated. Based on the calorific value calculation formula, the calorific value of the mixed gas is calculated by the calorific value calculation means 31a22, and the calorific value information indicating the calorific value is output by the calorific value information output means 31a23 to, for example, a display device, a communication device or the like. As a result, the heat generation amount of the mixed gas is notified.

  The calorific value measurement system according to claim 4 made in accordance with the present invention to solve the above-mentioned problems is a calorific value for measuring the calorific value of a mixed gas composed of a plurality of types of gas components as shown in the basic configuration diagram of FIG. A measurement system, comprising: a sensing element that is sensitive to a test substance in a test gas; and a comparison element that is not sensitive to a test substance in the test gas, wherein the thermal sensing between the detection element and the comparison element A contact combustion type gas sensor 10 that outputs a sensor output indicating a balance, a calorific value calculation formula generation unit 300 according to claim 1, and a calorific value calculation device 30 according to claim 3, wherein the contact The combustion type gas sensor 10 is driven by the mixed gas drive control means 21b of the calorific value calculation device 30, and the sensor output take-in means 31a21 of the calorific value calculation device 30 is the contact combustion type gas sensor. Wherein the capturing sensor output of 0.

  According to the calorific value measurement system of the present invention described in claim 4, when the catalytic combustion type gas sensor 10 driven at the mixed gas measurement temperature by the calorific value calculation device 30 outputs the sensor output corresponding to the mixed gas, The sensor output is taken into the calorific value calculation device 20 by the sensor output capturing means 31a21, and the calorific value of the mixed gas is calculated based on the sensor output and the calorific value calculation formula generated by the calorific value calculation formula generation unit 300. The calorific value information indicating the calorific value is output to, for example, a display device, a communication device, etc., so that the calorific value of the mixed gas is notified.

  As described above, according to the calorific value calculation formula generation unit of the present invention described in claim 1, when the catalytic combustion type gas sensor is driven by switching to a desired sensor driving temperature, the sensor output corresponding to the sensor driving temperature is output. The amount of heat generated corresponding to the sensor output is identified, a linear expression indicating the relationship between the sensor output and the amount of heat generated is calculated, and heat is generated based on a linear expression in which the intercept of the linear expression is zero or near zero. Since the amount calculation formula is generated and the sensor driving temperature corresponding to the calorific value calculation formula is specified as the mixed gas measurement temperature, the sensor output and the calorific value of the catalytic combustion type gas sensor driven at the mixed gas measurement temperature Based on the calculation formula, the calorific value of the mixed gas can be accurately calculated even in a region where the calorific value is lower than that of methane gas. Therefore, even if a mixed gas whose component ratio is unknown contains a non-combustible gas such as nitrogen, the calorific value of the mixed gas can be accurately and inexpensively calculated without using an expensive gas chromatograph. Can do.

  According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, a linear expression whose intercept is zero or near zero is extracted from the linear expressions calculated based on the collected sensor outputs. If not, based on the linear intercept and the sensor driving temperature, the sensor driving temperature that the intercept is zero or near zero is estimated, and the driving of the contact combustion type gas sensor is controlled by the sensor driving temperature. It is possible to obtain a linear equation whose intercept is zero or near zero, and a calorific value calculation equation can be generated more accurately based on the linear equation.

  As described above, according to the calorific value calculation device of the present invention described in claim 3, the mixed gas of the catalytic combustion type gas sensor driven by the mixed gas measurement temperature corresponding to the calorific value calculation formula of the calorific value calculation formula generation unit. When the calorific value calculation device captures the sensor output corresponding to the above, the calorific value of the mixed gas is calculated based on the sensor output and the calorific value calculation formula. Even if incombustible gas is included, the calorific value of the mixed gas can be accurately and inexpensively calculated without using an expensive gas chromatograph. Further, since it is not necessary to use a gas chromatograph, it is possible to continuously measure a plurality of mixed gases, and to measure the calorific value in a short time.

  As described above, according to the calorific value measurement system of the present invention described in claim 4, the calorific value is based on the catalytic combustion type gas sensor and sensor outputs corresponding to a plurality of gas components output by the catalytic combustion type gas sensor. A calculation formula, a calorific value calculation formula generating unit that generates a mixed gas measurement temperature corresponding to the calorific value calculation formula, a sensor output of a catalytic combustion type gas sensor driven at the mixed gas measurement temperature, and the calorific value calculation formula And a calorific value calculation device that calculates the calorific value of the mixed gas based on the above, and constitutes a calorific value measurement system, so that the gas component ratio including a non-combustible gas such as nitrogen is unknown. However, the calorific value can be accurately and inexpensively measured using a catalytic combustion type gas sensor. Therefore, it is not necessary to use an expensive gas chromatograph, and the cost of the system can be reduced. Therefore, the cost required for supplying the mixed gas whose component ratio is unknown can be reduced.

  Hereinafter, an embodiment of a calorific value measurement system including a calorific value calculation device incorporating a calorific value calculation formula generation unit according to the present invention will be described with reference to the drawings of FIGS.

  Here, FIG. 2 is a block diagram showing an example of a schematic configuration of the calorific value measurement system of the present invention, FIG. 3 is a diagram for explaining an example of a catalytic combustion type gas sensor, and FIG. 4 is a detection of FIG. FIG. 5 is a diagram illustrating an example of the configuration of an element, FIG. 5 is a configuration diagram illustrating a schematic configuration of a calorific value calculation device according to the present invention, and FIG. 6 is a graph illustrating temperature characteristics of a catalytic combustion type gas sensor. 7 is a graph showing the correlation between the sensor output and the heat generation amount when the sensor driving temperature is 275 ° C., and FIG. 8 is a graph showing the correlation between the sensor output and the heat generation amount when the sensor driving temperature is 310 ° C. FIG. 9 is a graph showing the correlation between the sensor output and the calorific value when the sensor driving temperature is 340 ° C., and FIG. 10 shows the correlation between the sensor output and the calorific value when the sensor driving temperature is 375 ° C. FIG. 11 is a graph showing FIG. 12 is a flowchart showing an example of a sensor output collection process executed by the CPU of FIG. 5, and FIG. 13 is a flowchart executed by the CPU of FIG. It is a flowchart which shows an example of the sensor output measurement process to perform.

  As shown in FIG. 2, the calorific value measurement system includes a container 1 that contains a supply gas that is a mixed gas, a flow path 2 that is connected to the container 1, and a mixed gas that is interposed in the flow path 2. A dilution section 3 that dilutes into a test gas (for example, 1 to 5% gas), a switching cock 4 connected to the flow path 2 on the downstream side of the dilution section 3, and a flow connected to the switching cock 4 A measurement tank 5 such as a chamber into which the test gas flows through the passage 2a, and a contact combustion gas sensor whose output changes depending on the concentration of the test gas in the measurement tank 5 (hereinafter referred to as a gas sensor). 10 and a calorific value calculation device 30 that calculates the calorific value of the test gas based on the output of the gas sensor 10.

  Further, the switching cock 4 is connected to one of the component flow paths 6 through which a plurality of calibration gases such as methane and propane can flow, which can be mixed gas as a gas component, and the other is used for the component. A component switching cock 7 for switching a plurality of calibration gases that flow out to the flow path 6 is connected.

  The component switching cock 7 is connected to component containers 8a, 8b, 8c, 8d, and 8e that contain a plurality of gas components such as methane, ethane, propane, butane, and pentane. In FIG. 2, only five component containers are shown, but the number is not limited to this, and various embodiments such as adding a component container containing other calibration gas are used. You can also.

  In the component flow path 6 between the switching cock 4 and the component switching cock 7, the pressure of the gas component or the like that is switched by the component switching cock 7 and flows in is the pressure indicated by the measurement conditions in the measurement tank 5. A pressure regulator 9 for adjusting (reducing pressure) is interposed. Each of the flow path 2 and the component flow path 6 has a flow meter M for measuring the flow rate flowing therethrough.

  Further, an air container 8f for storing air is further connected to the above-described component switching cock 7. Then, before starting measurement of the mixed gas, calibration gas (gas component), etc., an operator or the like performs the switching operation of the switching cock 4 and the component switching cock 7, thereby measuring the sensor output in the clean atmosphere. Therefore, the air base can be adjusted by flowing air into the measurement tank 5.

  Next, as shown in FIG. 3, the gas sensor 10 includes a detection element 11 a that is sensitive to a gas to be detected such as a supply gas and a calibration gas filled in the measurement tank 5. As shown in FIG. 4, the detection element 11a is formed with a coil-shaped portion 11 at the center of a platinum wire functioning as a resistance wire, and this coil-shaped portion 11 is made of, for example, palladium on a carrier of aluminum oxide powder. It is formed into a spherical shape by covering with a powder containing an appropriate oxidation catalyst.

  The gas sensor 10 further includes a comparison element 11b for eliminating the influence of the ambient environment such as temperature on the measurement value. The comparison element 11b is configured in the same manner as the detection element 11a except that it does not have a combustion catalyst. ing. The platinum wires of these elements are connected to a pair of pins 12a and 12b penetrating the sensor base 14, and the output values from these elements are applied to the tips of the pins 12a and 12b protruding from the back side of the sensor base 14. It is output to the outside of the sensor housing through the connected lead wire 16.

  Further, the gas sensor 10 is provided with an interference prevention plate 13 between the detection element 11a and the comparison element 11b so that they do not interfere with each other, and these are formed of a stainless steel double wire mesh, a porous sintered alloy, or the like. The cap 15 and the sensor base 14 are housed and protected in a sensor housing.

  The cap 15 is formed in a cylindrical shape and has a peripheral wall and a top wall. When the test gas hits the cap 15, the test gas permeates into the cap 15 so that the flow rate of the test gas hardly enters when entering the cap 15.

  In the configuration described above, the detection element 11a and the comparison element 11b are heated to a desired sensor driving temperature (for example, about 400 ° C.) by energization through the lead wire 16 and the pins 12a and 12b. When the detected gas comes into contact with the detection element 11a, a catalytic combustion reaction is caused by the catalyst, and this reaction raises the temperature of the detection element 11a to increase the electrical resistance, and the resistance balance with the comparison element 11b that does not cause the catalytic combustion reaction. In response to the breakdown of the resistance balance, a change in voltage taken out from a resistance bridge circuit (to be described later) of the gas sensor 10 occurs, and the concentration of the test substance can be detected based on the change.

  Next, as shown in FIG. 5, the calorific value calculation device 30 described above includes a sensor drive unit 21 that energizes the detection element 11 a and the comparison element 11 b of the gas sensor 10, and thermal detection between the detection element 11 a and the comparison element 11 b. A sensor output unit 22 that outputs a sensor output indicating a balance, a microcomputer (μCOM) 30 that operates according to a predetermined program, an operation unit 40 that allows an operator to perform various inputs, and in response to instructions from the μCOM 30 And a display unit 50 for performing various displays.

  The sensor drive unit 21 and the display unit 50 are connected to the output port of the μCOM 30, and the sensor output unit 22 and the operation unit 40 are connected to the input port, respectively. And the sensor drive part 21 controls a drive / stop so that the gas sensor 10 may become sensor drive temperature or mixed gas measurement temperature according to the request | requirement from microCOM30. Therefore, in this best mode, the sensor drive unit 21 corresponds to the drive control means and the mixed gas drive control means described in the claims. Then, the μCOM 30 collects sensor outputs that are A / D converted and output from the sensor output unit 22, and calculates the heat generation amount of the mixed gas based on the sensor outputs. The display unit 50 displays various information requested to be displayed by the μCOM 30.

  As is well known, the μCOM 30 controls the energization and stop of the central processing unit (CPU) 31 and the gas sensor (the detection element 11a and the comparison element 11b) 10 that perform various processes and controls according to a predetermined program, and sensor output. The ROM 32, which is a read-only memory storing various programs for causing the CPU 31 to execute various processes such as taking in the sensor output output by the unit 22 and calculating the calorific value, stores various data, and processes the CPU 31 The RAM 33 is a readable / writable memory having areas necessary for the above.

  Further, an electrically erasable / rewritable read-only memory (EEPROM) 34 capable of holding stored contents even when the apparatus main body is in an off state is connected to the input / output port of the μCOM 30. The EEPROM 34 corresponds to a plurality of types of gas components that can be components of the mixed gas, generates a calorific value table for obtaining a calorific value corresponding to the sensor output output from the gas sensor 10, and sensor output output from the gas sensor 10 to the mixed gas. The calorific value calculation information for calculating the calorific value of the mixed gas, the sensor driving temperature of the gas sensor 10 and the like are stored.

  In the best mode, the case where the heat generation amount corresponding to the sensor output is specified with reference to the heat generation amount table corresponding to the gas component corresponding to the heat generation amount specifying information will be described, but the present invention is not limited to this. For example, the heat generation amount calculation information for the gas component indicating the calculation formula for calculating the heat generation amount based on the sensor output corresponding to the gas component is used as the heat generation amount specifying information. can do. Therefore, in the best mode, the EEPROM 34 functions as the heat generation amount specifying information storage means described in the claims.

  Next, the gas sensitivity characteristic of the gas sensor 10 will be described with reference to the graph of FIG. Here, in FIG. 6, the vertical axis represents the sensor output (mV), the horizontal axis represents the sensor element temperature (° C.), and the results when each gas concentration is 1500 ppm are shown.

  The characteristics of the sensor output of the gas sensor 10 vary depending on the sensor driving temperature for the sensor elements of the detection element 11a and the comparison element 11b. That is, as shown in FIG. 6, a high sensor output cannot be obtained unless the temperature of the sensor element is increased as the molecular weight decreases with n-butane (butane), methane, ethane, and propane.

Therefore, since the sensor output of the gas sensor 10 also changes in accordance with the change in the sensor driving temperature, the slope and intercept of the graph G1 (approximate straight line) shown in FIG. Can be changed. In this graph G1, if the sensor output is Y, the calorific value is X, the slope is a, and the intercept is b,
Y = aX + b (Formula 1)
The calorific value calculation formula for calculating the calorific value from the sensor output is
X = (Y−b) / a (Formula 2)
Thus, the calorific value can be calculated by substituting the sensor output for Y in (Expression 2).

For example, each graph shown in FIGS. 7 to 10 shows the correlation between the sensor output and the calorific value with respect to methane, ethane, propane, and butane when the sensor driving temperature is changed. The axis represents sensor output (mV), and the horizontal axis represents combustion heat (MJ / Nm ³ ).

When the sensor driving temperature of the gas sensor 10 is 275 ° C. (applied voltage: 1.6 V), as shown in FIG.
Y = 0.0557X-1.0639 (Formula 3)
It can be expressed as.

Similarly, when the sensor driving temperature is 310 ° C. (applied voltage: 1.8 V), 340 ° C. (applied voltage: 2.0 V), and 375 ° C. (applied voltage: 2.2 V), FIG. 8 to FIG. As shown, the graphs G3-G5 are
Y = 0.0737X + 1.0754 (Formula 4)
Y = 0.0992X + 2.3141 (Formula 5)
Y = 0.0975X + 4.3384 (Formula 6)
Respectively.

  When the sensor driving temperature is 275 ° C. (Equation 3), the intercept is −1.0639 minus, and when the sensor driving temperature is 310 ° C. (Equation 4), the intercept is 1.0754 plus. . Since the intercepts are positive for (Equation 5) and (Equation 6), it can be seen that the intercept becomes positive when the sensor driving temperature is 310 ° C. or higher.

  In other words, since the intercept of the approximate straight line is 0 when the sensor driving temperature is 275 to 310 ° C., the gas sensor 10 is driven at the sensor driving temperature, and the intercept is 0 or near 0 based on the sensor output. Since an approximate straight line can be obtained, by using this approximate straight line as the calorific value calculation formula shown in Formula 2, the measurement accuracy of the mixed gas mixed with a nonflammable gas such as nitrogen can be improved.

  In the best mode, a calculation program for executing the calorific value calculation formula shown in (Expression 2) described above is stored in the ROM 32, and its inclination a and intercept b are stored in the calorific value calculation information of the EEPROM 34 described above. In addition, the calculation program calculates the heat generation amount with reference to the slope a and the intercept b of the heat generation amount calculation information.

  Further, in this best mode, 1 mV for each intercept is obtained based on the intercept of each approximate linear expression that is the intersection where the above-described graphs G2 to G5 intersect the vertical axis (sensor output) and the sensor driving temperature corresponding to the intercept. A temperature change table showing the hit temperature change is generated, and this temperature change table is stored in the EEPROM 34 in advance.

  Therefore, by referring to the temperature change table based on the calculated linear intercept and the sensor driving temperature, a linear equation passing through the origin or its vicinity shown in FIGS. The sensor driving temperature can be estimated. In this way, the number of measurements can be reduced.

  Next, an example of a processing outline according to the present invention executed by the CPU 31 of the calorific value calculation device 30 will be described below with reference to the flowcharts of FIGS.

  When the CPU 31 is activated, in step S11 shown in FIG. 11, the initial value of the sensor driving temperature of the gas sensor 10 is set and stored in the sensor driving temperature of the EEPROM 34. In step S12 (sensor output collecting means), sensor output collection is performed. The process is executed, and the process proceeds to step S13 in accordance with the end of the process.

  Here, an example of the sensor output collection process executed by the CPU 31 will be described with reference to the flowchart of FIG. When the sensor output collection process shown in FIG. 12 is called, in step S41, the display unit 50 displays a menu screen for requesting the operator to specify the gas component to be measured and requesting the end of collection of the sensor output. The menu screen information is output to the display unit 50, whereby the menu screen is displayed on the display unit 50, and then the process proceeds to step S42.

  In step S42, it is determined whether or not a gas component is designated based on input data from the operation unit 40 according to the display of the menu screen. If it is determined that it is not designated (N in S42), the process proceeds to step S46. On the other hand, if it is determined that it is designated (Y in S42), the process proceeds to step S43.

  In step S43, gas component identification data capable of identifying a gas component designated by an operator or the like is stored in the EEPROM 34, and the gas component identification data is designated and measured in order to measure the sensor output for the gas component. An output measurement process is executed, and the process proceeds to step S44 when the process ends.

  Here, an example of the sensor output measurement process executed by the CPU 31 will be described with reference to the flowchart shown in FIG. When the sensor output measurement process shown in FIG. 13 is called, the designated gas component identification data is stored in the RAM 33, and in step S51, a sampling timer that times out when a predetermined sampling time (for example, 5 minutes) elapses. In step S52, the gas sensor 10 is driven by instructing the sensor drive unit 21 to start driving at the sensor drive temperature of the EEPROM 34. Then, the process proceeds to step S53.

  In step S53, the sensor output is taken from the sensor output unit 22, and then in step S54, the sensor output is stored in the RAM 33 in time series in association with the above-described gas component identification data, and then proceeds to step S55. In step S55, it is determined whether or not the sampling timer has timed out. If it is determined that the time-out has not occurred (N in S55), the process returns to step S53, and a series of processing is repeated, so that sensor outputs are collected in time series.

  On the other hand, if it is determined in step S55 that a time-out has occurred (Y in S55), in step S56, the start of gas injection, the maximum value of the sensor output, etc. are analyzed during the collected sensor outputs, and then step S57. The average of the sensor outputs collected for about one minute before the gas injection time detected in the analysis is calculated as the average value AVE1 in the RAM 33, and then the process proceeds to step S58.

  In step S58, the average of the sensor outputs collected for about one minute after the maximum value of the sensor output detected in the analysis is calculated as the average value AVE2 in the RAM 33. In step S59, the average value AVE2 and the average value AVE1 are calculated. Is calculated as a sensor output. In step S60, the calculated sensor output is stored in a predetermined area of the RAM 33 in association with the gas component identification data, and then returned to the caller.

  By executing the sensor output measurement process in this way, the sensor output corresponding to the specified measurement target is collected, and the average value of the sensor outputs collected after the maximum value is detected is calculated as the sensor output. Therefore, even if a difference occurs in the output due to the characteristic of the gas sensor 10 or a subtle difference in ambient temperature, the present invention is based on the characteristic that the sensor output is stabilized after the maximum value after the maximum value. By using the average output value as the sensor output, the accuracy of the sensor output is improved.

  Next, in step S44 shown in FIG. 12, the calorific value corresponding to the sensor output measured based on the gas component calorific value calculation information in the EEPROM 34 is specified. In step S45, the calorific value and the gas component identification data are determined. The sensor output measured in association with the sensor drive temperature is stored in the EEPROM 34 and then the process proceeds to step S46.

  In step S46, based on the input data from the operation unit 40, it is determined whether collection end is requested. When it is determined that the collection end is not requested (N in S46), the process returns to step S42, a series of processes are repeated, and the sensor output for the other designated gas component is measured. The sensor output for each gas component is collected and stored corresponding to the sensor driving temperature. If it is determined that the end of collection has been requested (Y in S46), it is considered that the sensor output of the gas component to be measured has been collected, and then the process returns to the caller.

  Next, in step S13 (identification means, calculation means) shown in FIG. 11, the heat generation amounts corresponding to the collected sensor outputs are specified based on the heat generation amount table of the EEPROM 34, and the heat generation amounts and sensor outputs are determined. For example, by obtaining the slope a and the intercept b in the above (Equation 1), an approximate linear equation (linear equation) indicating the relationship between the sensor output and the heat generation amount is calculated. The approximate linear equation information shown is stored in the RAM 33, and then the process proceeds to step S14.

  In step S14 (extraction means), it is determined whether or not the intercept b of the approximate linear equation is zero. For this determination, it may be determined whether or not the intercept b is in the vicinity of 0, for example, −0.1 <intercept <0.1 in consideration of an error or the like. If it is determined that the intercept b is not 0 (N in S14), the process proceeds to step S15.

  In step S15, the calculated approximate linear equation is stored in the EEPROM 34 in correspondence with the sensor driving temperature in accordance with the sensor driving temperature, and information in the EEPROM 34 is stored in the EEPROM 34 in step S16 (estimating means). The sensor driving temperature at which the intercept becomes 0 is estimated by referring to the past approximate linear equation intercept b and its sensor driving temperature, and the sensor driving temperature of the EEPROM 34 is changed to the estimated temperature, and then step S12. Then, a series of processes corresponding to the estimated sensor driving temperature is performed.

  As an example of estimating the sensor driving temperature, the temperature change table corresponding to the intercept b of the approximate linear equation is extracted from the EEPROM 34, and the temperature at which the intercept b is zero is determined from the table. It is estimated as a sensor driving temperature.

  As another embodiment, when the intercept b of the approximate linear equation is positive, the sensor output is collected by lowering the sensor temperature, the approximate linear equation is calculated from the sensor output, and the intercept b is zero or It is also possible to repeat such processing until near zero.

  If it is determined in step S14 that the intercept b is 0 (Y in S14), in step S17 (mixed gas measurement temperature specifying means), the sensor drive temperature stored in the EEPROM 34 determines the calorific value of the mixed gas. When measuring, it is specified as the mixed gas measurement temperature for driving the contact combustion type gas sensor 10 and stored in the EEPROM 34, and then the process proceeds to step S18.

  In step S18 (heating value calculation formula generating means), based on the calculated approximate linear formula, the heat generation for calculating the heating value of the mixed gas from the sensor output corresponding to the mixed gas output by the catalytic combustion type gas sensor 10 A calorific value calculation formula is generated, and calorific value calculation information having the slope a and intercept b is stored in the EEPROM 34. Thereafter, the process proceeds to step S19.

  In step S19, notification screen information for displaying on the display unit a notification screen for notifying the operator or the like that measurement of the mixed gas is possible is output to the display unit 50, thereby notifying the display unit 50. A screen is displayed, and then the process proceeds to step S20.

  In step S <b> 20, it is determined whether or not a mixed gas measurement request has been received based on input data from the operation unit 40 corresponding to the display of the notification screen. If it is determined that a measurement request has not been received (N in S20), the process proceeds to step S25. On the other hand, if it is determined that a measurement request has been received (Y in S20), the process proceeds to step S21.

  In step S21 (sensor output taking means), a sensor output measurement process for the mixed gas is executed, and when the process ends, the process proceeds to step S22. Note that the measurement of the sensor output measurement process is almost the same as the measurement object, except that the measurement object is a mixed gas unlike step S43 described above, and a detailed description thereof will be omitted. By executing the sensor output measurement process, in step S52, the sensor drive unit 21 is instructed to start driving at the mixed gas measurement temperature of the EEPROM 34, and the sensor output output from the driven gas sensor 10 is measured and mixed. The sensor output corresponding to the gas is stored in the RAM 33.

In step S22 (heat generation amount calculation means), Y in the heat generation amount calculation formula (formula 2) is the sensor output corresponding to the mixed gas in the RAM 33, constants a and b are the slope a and intercept b of the heat generation amount calculation information of the EEPROM 34. By calculating by substituting each, the calorific value corresponding to the mixed gas is calculated by the calorific value calculation formula (formula 2), and in step S23, the calorific value is converted to be displayed as MJ / Nm ^3. Then, the calorific value information indicating the calorific value is generated and stored in the EEPROM 34, and then the process proceeds to step S24.

  In step S24 (heat generation amount information output means), the heat generation amount information is output to the display unit 50, whereby the heat generation amount is displayed on the display unit 50, and then the process proceeds to step S25. In addition, about the output of calorific value information, when providing a communication part in an apparatus configuration and transmitting, it can be set as various different embodiments, such as outputting to the communication part.

  In step S25, it is determined whether an end request has been received based on input data from the operation unit 40. If it is determined that an end request has not been received (N in step S25), the process returns to step S20, and a series of processes is repeated. On the other hand, if it is determined that an end request has been received (Y in step S25), the process ends.

  Therefore, in the above-described best mode, the CPU 31 of the calorific value calculation device 30 incorporating the calorific value calculation formula generation unit, the sensor output collecting means, the specifying means, the calculating means, the extracting means, the heat generation described in the claims. It functions as an amount calculation formula generating means, a mixed gas measurement temperature specifying means, a sensor output taking means, a calorific value calculating means, and a calorific value information outputting means.

  Next, an example of the operation (action) of the best mode of the calorific value measurement system using the calorific value calculation device 30 according to the present invention will be described below.

  In FIG. 2, the component switching cock 7 is switched to the air container 8f, and the switching operation of the switching cock 4 is performed, so that air flows into the measurement tank 5 and the air base is adjusted. Then, the component switching cock 7 is switched to the methane gas component container 8a, and the switching cock 4 is switched, whereby methane gas is injected into the measuring tank 5 as a gas component.

  In this state, the calorific value calculation device 30 starts energizing the gas sensor 10 so as to reach the sensor driving temperature, takes in the sensor output output by the gas sensor 10, and associates it with the sensor driving temperature as the sensor output of methane gas. Remembered. Then, after the air base adjustment described above is performed, the component switching cock 7 is switched to the ethane gas component container 8b, and the switching cock 4 is switched, so that it is the next gas component in the measuring tank 5. Ethane gas is injected. And the sensor output which the gas sensor 10 output is taken in, and it is linked | related with sensor drive temperature and memorize | stored as a sensor output of ethane gas. By performing the above processing for each gas component of propane, butane, and pentane, sensor outputs corresponding to the same sensor driving temperature are collected.

  The calorific values corresponding to these sensor outputs are specified based on the calorific value table of the EEPROM 34, and an approximate linear equation is calculated based on the calorific values and sensor outputs. If the intercept b is not 0, the sensor driving temperature at which the intercept b is zero or near zero is estimated based on the past approximate straight line b and the sensor driving temperature. 10 is driven to obtain the following approximate linear equation.

  If the intercept b of the approximate linear equation is zero or close to zero, the mixed gas measurement temperature is specified based on the sensor driving temperature of the EEPROM 34, and the calorific value calculation formula corresponding to the temperature is generated in the approximate linear equation. Is stored as the calorific value calculation information in the EEPROM 34, and then a notification screen is displayed on the display unit 50.

  By switching the switching cock 4 to the flow path 2 in accordance with the display of the notification screen, the test gas (mixed gas) diluted to 3000 ppm is injected into the measurement tank 5. When a measurement request is generated by an operation on the operation unit 40, the calorific value calculation device 30 starts energization of the gas sensor 10 so as to reach the mixed gas measurement temperature of the EEPROM 23, and takes in the sensor output output by the gas sensor 10, A calorific value is calculated based on the sensor output and the calorific value calculation information of the EEPROM 34, and the calorific value information indicating the calorific value is output to the display unit 50, whereby the calorific value is displayed on the display unit 50.

  As described above, the calorific value calculation formula and the mixed gas measurement corresponding to the calorific value calculation formula based on the catalytic combustion type gas sensor 10 and sensor outputs corresponding to a plurality of gas components output by the catalytic combustion type gas sensor 10. A calorific value for calculating the calorific value of the mixed gas based on the sensor output of the catalytic combustion gas sensor 10 driven at the mixed gas measurement temperature and the calorific value calculation formula, provided with a calorific value calculating formula generating unit for generating the temperature Since the calorific value measurement system is configured to include the calculation device 30, even if it is a mixed gas whose ratio of gas components including non-combustible gas such as nitrogen is unknown, its heat generation is performed using a contact combustion type gas sensor. The amount can be measured accurately and inexpensively. Therefore, it is not necessary to use an expensive gas chromatograph, and the cost of the system can be reduced. Therefore, the cost required for supplying the mixed gas whose component ratio is unknown can be reduced.

  In the best mode described above, the embodiment in which the heat generation amount calculation formula generation unit of the present invention is incorporated in the heat generation amount calculation device 30 has been described. However, the present invention is not limited to this, and the heat generation amount calculation formula generation unit. The calorific value calculation formula calculated by the above and its mixed gas measurement temperature are stored in the calculation device as the calorific value, and the gas component can be in various forms such as a form in which the gas component is not measured each time the mixed gas is measured.

  Further, in the above-described best mode, the case where an approximate straight line is calculated from the sensor output for each gas component and its calorific value has been described, but the present invention is not limited to this, and for example, the main line such as LNG or the like. When the component gas is known, an embodiment in which a linear equation is calculated based on the main component methane gas and other gas components may be employed.

It is a figure which shows the basic composition of the calorific value calculation formula production | generation unit of this invention, the calorific value calculation apparatus, and the calorific value measuring system. It is a block diagram which shows an example of schematic structure of the calorific value measuring system of this invention. It is a figure for demonstrating an example of a contact combustion type gas sensor. It is a figure for demonstrating an example of a structure of the detection element of FIG. It is a block diagram which shows schematic structure of the emitted-heat amount calculation apparatus which concerns on this invention. It is a graph which shows the temperature characteristic of a contact combustion type gas sensor. It is a graph which shows the correlation of a sensor output and calorific value when sensor drive temperature is 275 degreeC. It is a graph which shows the correlation of a sensor output in case a sensor drive temperature is 310 degreeC, and the emitted-heat amount. It is a graph which shows the correlation of a sensor output in case a sensor drive temperature is 340 degreeC, and the emitted-heat amount. It is a graph which shows the correlation of a sensor output and calorific value when sensor drive temperature is 375 degreeC. It is a flowchart which shows an example of the process outline | summary which concerns on this invention which CPU of FIG. 5 performs. It is a flowchart which shows an example of the sensor output collection process which CPU of FIG. 5 performs. It is a flowchart which shows an example of the sensor output measurement process which CPU of FIG. 5 performs. It is a graph which shows the relationship between the sensor output of a contact combustion type gas sensor with respect to each gas component, and the emitted-heat amount.

Explanation of symbols

10 catalytic combustion type gas sensor 21a drive control means (sensor drive unit)
21b Mixed gas drive control means (sensor drive unit)
30 Calorific value calculation device 31a11 Sensor output collecting means (CPU)
31a12 specifying means (CPU)
31a13 calculation means (CPU)
31a14 Extraction means (CPU)
31a15 Calorific value calculation formula generating means (CPU)
31a16 Mixed gas measurement temperature specifying means (CPU)
31a17 Estimation means (CPU)
31a21 Sensor output capturing means (CPU)
31a22 Calorific value calculation means (CPU)
31a23 Heat generation amount information output means (CPU)
34 Heat generation amount specific information storage means (EEPROM)

Claims (4)

Thermal balance between the detection element and the comparison element output from the catalytic combustion type gas sensor having a detection element sensitive to the test substance in the test gas and a comparison element not sensitive to the test substance in the test gas A calorific value calculation formula generating unit that generates a calorific value calculation formula for calculating a calorific value of a mixed gas composed of a plurality of types of gas components based on a sensor output indicating:
Drive control means for controlling to drive the catalytic combustion type gas sensor by switching to a desired sensor drive temperature;
A calorific value for storing calorific value identification information that can identify the calorific value of the gas component corresponding to the sensor output output by the catalytic combustion gas sensor in correspondence with the sensor driving temperature of the catalytic combustion gas sensor. Specific information storage means;
Sensor output collecting means for collecting sensor outputs outputted by the catalytic combustion type gas sensor for the plurality of types of gas components in correspondence with the sensor driving temperature of the catalytic combustion type gas sensor;
Specifying means for specifying the heat generation amount corresponding to the sensor output collected by the sensor output collection means based on the heat generation amount specifying information stored in the heat generation amount specifying information;
A calculating means for calculating a linear expression indicating a relationship between the sensor output collected by the sensor output collecting means and the calorific value specified by the specifying means, corresponding to the sensor driving temperature;
Extracting means for extracting a linear expression whose intercept of the linear expression is zero or near zero from the linear expressions calculated by the calculating means;
A calorific value calculation that generates a calorific value calculation formula for calculating the calorific value of the mixed gas from the sensor output corresponding to the mixed gas output by the catalytic combustion gas sensor based on the linear equation extracted by the extracting means An expression generation means;
When the calorific value calculation formula is generated by the calorific value calculation formula generating means, the sensor driving temperature corresponding to the calorific value calculation formula is driven, and the catalytic combustion type gas sensor is driven when the calorific value of the mixed gas is measured. A mixed gas measurement temperature specifying means for specifying the mixed gas measurement temperature;
A calorific value calculation formula generation unit comprising: When the extraction unit cannot extract the linear equation, the intercept is made zero or near zero based on the intercept of each linear equation calculated by the calculation unit and the sensor driving temperature corresponding to the intercept. It further comprises an estimation means for estimating the sensor driving temperature,
The calorific value calculation formula generation unit according to claim 1, wherein the drive control unit performs the control at the sensor driving temperature estimated by the estimation unit. Thermal balance between the detection element and the comparison element output from the catalytic combustion type gas sensor having a detection element sensitive to the test substance in the test gas and a comparison element not sensitive to the test substance in the test gas The calorific value calculation for calculating the calorific value of the mixed gas composed of a plurality of types of gas components based on the sensor output indicating the calorific value and the calorific value calculation formula generated by the calorific value calculation formula generating unit according to claim 1 A device,
A mixed gas drive control means for controlling to drive the catalytic combustion gas sensor at the mixed gas measurement temperature specified by the mixed gas measurement temperature specifying means of the calorific value calculation formula generation unit;
Sensor output capturing means for capturing the sensor output corresponding to the mixed gas output by the catalytic combustion gas sensor in accordance with the control of the mixed gas drive control means;
A calorific value calculation means for calculating the calorific value based on the sensor output captured by the sensor output capturing means and the calorific value calculation formula generated by the calorific value calculation formula generating means of the calorific value calculation formula generating unit;
A calorific value information output means for outputting the calorific value information indicating the calorific value calculated by the calorific value calculating means;
A calorific value calculation device comprising: A calorific value measuring system for measuring the calorific value of a mixed gas composed of plural kinds of gas components,
A sensor element that has a detection element that is sensitive to a test substance in the test gas and a comparison element that is insensitive to the test substance in the test gas, and that shows a sensor output indicating a thermal balance between the detection element and the comparison element. A catalytic combustion gas sensor to output,
The calorific value calculation formula generation unit according to claim 1 or 2,
The calorific value calculation device according to claim 3,
With
The catalytic combustion type gas sensor is driven by a mixed gas drive control means of the calorific value calculation device,
The calorific value measuring system, wherein the sensor output capturing means of the calorific value calculating device captures the sensor output of the catalytic combustion type gas sensor.

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