JP5001908B2 - Mixed gas component measuring apparatus and component measuring method - Google Patents

Description

  The present invention relates to a mixed gas component measurement device and the like in which other gases are mixed in saturated hydrocarbon gas, and more particularly to a component measurement device and the like that can easily and quickly measure the components and heat generation amount of the mixed gas and are inexpensive.

  In the process of generating city gas and supplying it to consumers, other gases such as nitrogen and air may be mixed with saturated hydrocarbon gases such as methane, ethane, and propane, which are the main components. For example, when using gas vaporized in a liquefied gas storage tank, when using natural gas from a gas well, or when intentionally diluting saturated hydrocarbon gas, saturated hydrocarbon gas and other gases are used. The mixed gas is supplied. In such a case, in order to perform gas supply that satisfies the necessary conditions, it is necessary to monitor the heat generation amount of the mixed gas and the mixing amount of the other gas.

Regarding the measurement technique for monitoring such a gas, for example, the following Patent Document 1 describes obtaining the calorific value of a saturated hydrocarbon gas using a flow meter, and the following Patent Document 2 describes city gas. A technique for measuring a nitrogen component therein is described, and Patent Document 3 below describes a method for monitoring the mixing of miscellaneous gas into a city gas feedstock.
JP-A-3-39623 JP-A-6-50967 JP 10-38827 A

  However, in the apparatus described in Patent Document 1, measurement is impossible when other gases are mixed into the saturated hydrocarbon gas and the gas concentration fluctuates. Further, in the apparatus described in Patent Document 2, it is necessary to prepare a concentration measuring sensor for each gas component, which makes the apparatus expensive. Further, in the apparatus described in Patent Document 3, the calorific value is measured using the thermal conductivity, but it takes about several seconds for the response, and calibration with a known standard gas is necessary, so that it is faster and easier. A method is desired.

  Accordingly, an object of the present invention is a component measurement device for a mixed gas in which another gas is mixed into a saturated hydrocarbon gas, and the component measurement device that can easily and quickly measure the component and the calorific value of the mixed gas and is inexpensive. , Etc. is to provide.

  In order to achieve the above object, one aspect of the present invention is a mixture of a first gas composed of one or more kinds of saturated hydrocarbons and a second gas having a known component different in kind from the first gas. The mixed gas component measuring device detects a differential pressure of the flowing gas, and obtains the flow rate of the gas based on a relational expression between the differential pressure, the viscosity of the gas, and the flow rate of the gas. A first flow meter that detects the differential pressure by circulating the mixed gas; detects a differential pressure of the circulating gas; and based on a relational expression between the differential pressure, the density of the gas, and the flow rate of the gas A flow meter for determining a flow rate of the gas, wherein the mixed gas flowing out from the first flow meter flows into the flow meter, or the mixed gas flowing out from the flow meter is It is arranged to flow into the flow meter and distributes the mixed gas. A second flow meter for detecting a differential pressure, a density meter for detecting the density of the mixed gas, a differential pressure detected by the first flow meter and the second flow meter, and detected by the density meter. Density, the relational expression in the first flowmeter and the second flowmeter, the density and viscosity of the first gas being in an inversely proportional relationship, and the viscosity of the mixed gas and the first flowmeter And calculating means for obtaining a mixing ratio of the first gas and the second gas based on a relational expression between the gas and the viscosity of the second gas.

  Furthermore, in the above invention, a preferred aspect is characterized in that the calculation means further obtains the calorific value of the mixed gas by using a proportional relationship between the density of the first gas and the calorific value. And

  In order to achieve the above object, another aspect of the present invention is that a first gas composed of one or more kinds of saturated hydrocarbons is mixed with a second gas having a known component different in kind from the first gas. A first flow meter that detects a differential pressure of a flowing gas and determines a flow rate of the gas based on a relational expression between the differential pressure, the viscosity of the gas, and the flow rate of the gas. Detecting a differential pressure by circulating the mixed gas, detecting a differential pressure of the circulating gas, and determining the pressure of the gas based on a relational expression of the differential pressure, the density of the gas, and the flow rate of the gas. A flow meter for obtaining a flow rate, wherein the mixed gas flowing out from the first flow meter flows into the flow meter, or the mixed gas flowing out from the flow meter flows into the first flow meter. The mixed gas flows into a second flow meter arranged to flow in. Detecting the differential pressure, detecting the density of the mixed gas with a density meter, and detecting the differential pressure detected with the first flow meter and the second flow meter with the density meter. Density, the relational expression in the first flowmeter and the second flowmeter, the density and viscosity of the first gas being in an inversely proportional relationship, and the viscosity of the mixed gas and the first flowmeter And a step of obtaining a mixing ratio of the first gas and the second gas based on a relational expression between the gas and the viscosity of the second gas.

  Further objects and features of the present invention will become apparent from the embodiments of the invention described below.

  Embodiments of the present invention will be described below with reference to the drawings. However, such an embodiment does not limit the technical scope of the present invention. In the drawings, the same or similar elements are denoted by the same reference numerals or reference symbols.

  FIG. 1 is a configuration diagram according to an embodiment of a mixed gas component measuring apparatus to which the present invention is applied. A component measuring apparatus 1 shown in FIG. 1 is an apparatus according to the present embodiment. A hydrocarbon gas composed of one or more kinds of saturated hydrocarbons (hereinafter referred to as a hydrocarbon gas) is replaced with another type of other gas ( (Hereinafter referred to as “mixed gas”), the mixed gas is mixed, the differential pressure is detected by each of the laminar flow meter and the differential pressure type flow meter, and the density is detected by the density meter. Based on the property that hydrocarbon gas can be handled as one kind of gas regardless of its component ratio, and the relational expression related to the physical properties of the mixed gas, the concentration of the mixed gas and the calorific value of the mixed gas are obtained. It is intended to measure the quantity simply and at high speed.

  A main pipe 2 shown in FIG. 1 is a pipe through which the mixed gas to be measured flows. As described above, the measurement target gas is a mixture of a hydrocarbon gas composed of one or more kinds of saturated hydrocarbons such as methane, ethane, and propane, and a mixed gas whose components are known, such as nitrogen, air, and carbon dioxide. Gas.

  The sampling pipe 3 is a pipe that guides the mixed gas from the main pipe 2 to the component measuring apparatus 1, and although not shown, a device such as a valve is attached as necessary. Further, after the measurement by the component measuring apparatus 1, the gas discharged from the density meter 13 is appropriately disposed by a method such as atmospheric release.

  As shown in FIG. 1, the component measuring apparatus 1 includes a laminar flow meter 11, a differential pressure type flow meter 12, a density meter 13, a calculation unit 14, a communication unit 15, and the like. The laminar flow meter 11, the differential pressure flow meter 12, and the density meter 13 are connected by piping, and these meters are arranged in series. In the embodiment shown in FIG. 1, the laminar flow meter 11, the differential pressure meter 12, and the density meter 13 are arranged in this order, but this is an example, and other arrangements and It is also possible to do. However, the laminar flow meter 11 and the differential pressure flow meter 12 need to be arranged in series regardless of the order from the measurement principle of the component measuring apparatus 1 described later. That is, it is necessary to measure a mixed gas having the same flow rate Q in both flow meters. In this embodiment, the measurement target gas is branched from the main pipe 2 and measured. However, the component measuring device 1 may be installed in the main pipe 2 if possible.

  The calculation means 14, the laminar flow meter 11, the differential pressure flow meter 12, the density meter 13, and the communication means 15 are connected by a communication line, and each detection value, measurement result, etc. are exchanged.

The laminar flow meter 11 is a general laminar flow meter that uses the viscosity (viscosity μ (Pa · s)) of the measurement target gas. FIG. 2 is a diagram showing the structure of the laminar flow meter 11. In FIG. 2, the measurement target gas (mixed gas) of the flow rate Q (m ³ / s) flowing in from the left side passes through n _l diameter _dl (m) and length l _l (m) narrow tubes on the right side. Spill to At that time, the differential pressure dp ₁ (Pa) before and after the narrow tube is detected by a differential pressure gauge. At this time, in the laminar flow meter 11, the following relational expression 1 holds.

In the case of normal use, the viscosity of the measurement target gas μ is known, by detecting the differential pressure dp _l, it can be determined the flow rate Q from the formula in Formula 1. In the component measuring device 1, the value of the detected pressure difference dp _l is sent to the arithmetic unit 14.

Next, the differential pressure type flow meter 12 is a general differential pressure type flow meter using the density ρ (kg / m ³ ) of the measurement target gas. FIG. 3 is a diagram showing the structure of the differential pressure type flow meter 12. Flowmeter shown in FIG. 3 is a Venturi flow meter as an example, the flow rate Q flowing from the left (m ³ / s) measured gas (mixed gas), the passage diameter D _{v (m),} the diameter D _v ( It flows to the right after passing through a passage narrowed from m) to diameter d _v (m). At that time, the differential pressure dp _v (Pa) before and after the passage in which the diameter is reduced is detected by a differential pressure gauge. At this time, in the laminar flow meter 12, the following relational expression 2 holds.

In the case of normal use, the density ρ of the gas to be measured is known, by detecting the differential pressure dp _v, it can be determined the flow rate Q from the formula of Equation 2. In the component measuring device 1, the value of the detected pressure difference dp _v is sent to the arithmetic unit 14.

  Next, the density meter 13 is a general density meter that measures the gas density, and for example, a vibrating tube type or an ultrasonic type can be used. The density meter 13 detects the density ρ of the mixed gas flowing out from the differential pressure type flow meter 12, and the value is sent to the calculation means 14. As described above, the arrangement of the density meter 13 may not be as shown in FIG. 1, and measurement may be performed by introducing a mixed gas from the main pipe 2 through a sampling pipe different from the flow meters 11 and 12. .

  The calculation means 14 uses the detection results of the laminar flow meter 11, the differential pressure flow meter 12, and the density meter 13, the physical property values received and held in advance, and the like, and the heat generation of the mixed gas that is the measurement target This is a part for calculating the amount and concentration of the mixed gas. Specific relational expressions and numerical values used for the calculation will be described later. In addition, this calculating means 14 may be comprised with hardware, such as ASIC, and may be comprised with CPU etc. which perform a process according to the program and its program.

  The communication unit 15 is a communication interface between the component measurement device 1 and the outside, and transmits the measurement result (calculation result) in the calculation unit 14 to a predetermined external device. In addition, data such as physical property values required by the calculation means 14 is received from the outside and transmitted to the calculation means 14. The physical property value or the like may be received by providing an operation / input unit in the component measuring apparatus 1 and manually inputting a value from the operation / input unit.

Next, the measurement procedure and processing contents in the component measuring apparatus 1 having such a configuration will be described. First, how to handle the above-described mixed gas as a measurement target will be described. As for the density and viscosity of a gas in which a plurality of types of saturated hydrocarbons are mixed, as described in JP-A-3-39623, the density ρ with respect to the calorific value H (J / m ³ ) of the mixed gas. Is proportional and viscosity μ is inversely proportional, and the following equations (a) and (b) hold.

ρ = K ₂ H (a) Formula μ = K ₄ / H (b) Formula From these two formulas, it can be seen that the density and the viscosity are in an inversely proportional relationship as shown in the following formula (c).

μ = K ₄ K ₂ / ρ (c) Formula Here, the density ρ is proportional to the average molecular weight m _ave of this mixed gas as represented by the following formula (d).

ρ = K ₇ m _ave (d) Formula K ₂ , K ₄ , and K ₇ are respectively predetermined constants.

  From the above, for a gas in which a plurality of saturated hydrocarbons are mixed, the viscosity is the same for a gas having the same density (average molecular weight) regardless of the component ratio of the saturated hydrocarbon constituting the gas. It turns out that it becomes. This indicates that a gas mixed with saturated hydrocarbons can be regarded as a single gas if the average molecular weight (or density or viscosity) is the same, regardless of the component ratio of the saturated hydrocarbons constituting the gas. Yes.

Therefore, another type of gas mixed with saturated hydrocarbons, that is, a mixed gas as a measurement target in which the mixed gas is mixed can be handled as a mixed gas of two types of gases. Therefore, in this component measuring apparatus 1, the mixed gas to be measured is handled as a mixture of two types of gases, the hydrocarbon gas and the mixed gas, and the mixing ratio (component fraction) is x _1. and the _{x 2.}

FIG. 4 is a flowchart illustrating a measurement / processing procedure in the component measurement apparatus 1. At the time of measurement, the mixed gas is introduced from the sampling pipe 3 described above, and measurement is first performed in the laminar flow meter 11 (step S1). Here, when the guided mixed gas passes through the flow meter, and detects the differential pressure dp _l described above, and sends the value to the computation means 14.

Next, the mixed gas that has passed through the laminar flow meter 11 is guided to the differential pressure flow meter 12 for measurement (step S2). Again, when the guided mixed gas passes through the flow meter, and detects the differential pressure dp _v described above, and sends the value to the computation means 14.

  Thereafter, the mixed gas that has passed through the differential pressure type flow meter 12 is guided to the density meter 13, where the density is detected (step S3). The detected density is sent to the calculation means 14.

  As described above, when the measurement of the measurement target gas is completed, the calculation means 14 determines the detected values transmitted from the flow meters 11 and 12 and the density meter 13, various known values held in advance, and the behavior and physical properties of the mixed gas. Based on such various relational expressions, each unknown value necessary for obtaining the concentration of the mixed gas and the calorific value of the mixed gas is calculated (step S4).

  Hereinafter, the relational expression used for the calculation will be described.

First, the laminar flow the viscosity of the flow rate Q and the mixed gas flow meter 11 at the detected differential pressure dp _l mixed gas μ is the relational expression is used because the following relationship holds several 1 described above. In the formula, the flow rate Q and the viscosity μ are unknown numbers, and other values are known. That is, the differential pressure dp _l are as hereinbefore measured, other known value is held in advance in the computing unit 14 as the specification of the flowmeter.

Also, the difference in pressure flow density of meter 12 at the detected differential pressure dp _v mixed gas flow rate Q and the mixed gas ρ is the relational expression is used because the following relationship holds for two numbers as described above. In the formula, the flow rate Q is an unknown number, and other values are known. That is, the differential pressure dp _v and the density ρ are measured as described above, and other known values are held in the computing unit 14 in advance as the specifications of the flow meter.

Further, the following relational expression 3 is established between the density of the mixed gas and the density of each component gas, that is, the density ρ ₁ of the hydrocarbon gas and the density ρ _{2 of the} mixed gas, and this formula is used. It is done.

Here, the density ρ ₁ of the hydrocarbon gas and the component fractions x ₁ and x _{2 of} each gas are unknown, and the measured ρ and the density ρ _{2 of the} mixed gas are known. As described above, since the component and the component ratio of the mixed gas are known, the density ρ ₂ is also known and is held in the computing means 14 in advance.

  Further, from the above-described equation (d), the following relational expression is established for the hydrocarbon gas, and this equation is used.

Here, the density ρ ₁ of the hydrocarbon gas and the molecular weight m ₁ of the hydrocarbon gas are unknown numbers, and the coefficient K ₇ is held in advance in the computing means 14 as a known value.

Further, the relational expression shown in the following equation 5 holds between the viscosity μ of the mixed gas and the viscosity of each component gas, that is, the viscosity μ ₁ of the hydrocarbon gas and the viscosity μ _{2 of the} mixed gas. Used.

Note that the first equation shown in Equation 5 is a Superland equation, and the second and third equations are Wilke's equations. Here, the viscosity μ and μ ₁ of the mixed gas and the hydrocarbon gas, the component fraction x ₁ and x ₂ , the density ρ ₁ of the hydrocarbon gas and the molecular weight m ₁ are unknown, and the viscosity μ ₂ and density ρ of the mixed gas are unknown. ₂ and molecular weight m ₂ are known. The known value is held in advance in the calculation means 14.

Further, for the component fractions x ₁ and x ₂ which are unknown numbers, the following relational expression 6 is established, and this expression is also used.

  Further, from the above-described equation (c), the following relational expression is established for the hydrocarbon gas, and this equation is used.

Here, the density ρ ₁ of the hydrocarbon gas and the viscosity μ ₁ of the hydrocarbon gas are unknown numbers, and the coefficients K ₂ and K ₄ are held in the calculation means 14 in advance as known values.

By solving the seven equations described above (equations described in Equations 1 to 7) simultaneously, the seven unknowns are flow rate Q, density ρ ₁ , viscosity μ and μ ₁ , mixing ratio x ₁ and x. _2. It is possible to obtain the value of the molecular weight m ₁ , and the calculation means 14 calculates these values by the above seven formulas and the respective known values.

  Of the known values used in the above calculation and previously stored in the calculation means 14, those that need to be changed after the installation of the component measuring apparatus 1 are appropriately received and held via the communication means 15. . Further, as described above, an operation / input means may be provided and a value may be manually input from here and held.

When the above values are calculated in this way, the calculation means 14 calculates the mixed gas mixing ratio x _{2 and} uses it as the mixed gas concentration, and calculates the density ρ ₁ of the hydrocarbon gas. Therefore, the calorific value H of the hydrocarbon gas, that is, the calorific value of the mixed gas is calculated using the above equation (a) (step S5).

  The determined concentration of the mixed gas and the calorific value of the mixed gas are transmitted from the communication means 15 to a predetermined external location and output (step S6).

  As described above, in the component measuring apparatus 1 according to this embodiment, the laminar flow meter 11 and the differential pressure flow meter 12 are used for the mixed gas of hydrocarbon gas and mixed gas composed of one or more kinds of saturated hydrocarbons. Based on the measurement results of the density meter 13, the property that the hydrocarbon gas can be handled as one kind of gas regardless of its component ratio, and the respective relational expressions relating to the physical properties of the mixed gas, the calorific value and the concentration of the mixed gas Ask for. Therefore, since a sensor such as a gas concentration meter is not required and calibration after measurement is not required, accurate monitoring of mixed gas can be easily performed with an inexpensive apparatus.

  In addition, by using the laminar flow meter 11, the differential pressure flow meter 12, and the density meter 13, high-speed (several tens of Hz) measurement is possible, and the change in the calorific value of the mixed gas and the concentration of the mixed gas are appropriately adjusted. It becomes possible to capture.

  The above-described component measuring apparatus 1 has the communication means 15 and transmits the measurement result to the outside. However, the component measuring apparatus 1 is provided with output means such as a display device, and the measured calorific value and mixed gas concentration are measured. May be output on the component measuring apparatus 1 side.

  The protection scope of the present invention is not limited to the above-described embodiment, but covers the invention described in the claims and equivalents thereof.

It is a block diagram which concerns on the example of embodiment of the component measuring apparatus of the mixed gas to which this invention is applied. FIG. 2 is a diagram showing the structure of a laminar flow meter 11. FIG. 3 is a diagram showing a structure of a differential pressure type flow meter 12. 3 is a flowchart illustrating a measurement / processing procedure in the component measurement apparatus 1.

Explanation of symbols

  1 component measuring device, 2 main piping, 3 sampling piping, 11 laminar flow meter, 12 differential pressure flow meter, 13 density meter, 14 computing means, 15 communication means

Claims (3)

A component measuring device for a mixed gas in which a first gas having an unknown density composed of one or more kinds of saturated hydrocarbons and a second gas having a known component different in type from the first gas are mixed,
A flowmeter that detects a differential pressure of a flowing gas and obtains a flow rate of the gas based on a relational expression between the differential pressure, the viscosity of the gas, and the flow rate of the gas, wherein the difference is obtained by circulating the mixed gas. A first flow meter for detecting pressure;
A flow meter that detects a differential pressure of a flowing gas and obtains a flow rate of the gas based on a relational expression between the differential pressure, the density of the gas, and the flow rate of the gas, The mixed gas flows into the flow meter, or the mixed gas flowing out of the flow meter flows into the first flow meter, and the mixed gas is circulated to reduce the differential pressure. A second flow meter to detect;
A density meter for detecting the density of the mixed gas;
Differential pressure detected by the first flow meter and the second flow meter, density detected by the density meter, the relational expression in the first flow meter and the second flow meter, the first Based on the property that the gas can be treated as one kind of gas, and the relational expression between the viscosity of the mixed gas and the viscosity of the first gas and the second gas, the first gas and the second gas An apparatus for measuring a component of a mixed gas, comprising: an arithmetic means for obtaining a mixing ratio of the gas. In claim 1,
The calculation unit further determines the calorific value of the mixed gas by using the fact that the density of the first gas and the calorific value are in a proportional relationship. A method for measuring a component of a mixed gas in which a first gas having an unknown density composed of one or more kinds of saturated hydrocarbons and a second gas having a known component different in type from the first gas are mixed,
The mixed gas is circulated through a first flowmeter that detects the differential pressure of the gas flowing and obtains the flow rate of the gas based on the relational expression between the differential pressure, the viscosity of the gas, and the flow rate of the gas. Detecting the differential pressure;
A flow meter that detects a differential pressure of a flowing gas and obtains a flow rate of the gas based on a relational expression between the differential pressure, the density of the gas, and the flow rate of the gas, and flows out of the first flow meter. The mixed gas is disposed in a second flow meter arranged so that the mixed gas flows into the flow meter or the mixed gas flowing out of the flow meter flows into the first flow meter. A process of detecting a differential pressure by circulating
Detecting the density of the mixed gas with a density meter;
Differential pressure detected by the first flow meter and the second flow meter, density detected by the density meter, the relational expression in the first flow meter and the second flow meter, the first Based on the property that the gas can be treated as one kind of gas, and the relational expression between the viscosity of the mixed gas and the viscosity of the first gas and the second gas, the first gas and the second gas And a step of obtaining a mixing ratio of the gas.

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