WO2016104270A1 - Method for calculating methane number and device for determining methane number - Google Patents

Abstract

The purpose of the present invention is to provide: a method for methane number calculation with which a probably reliable methane number of a natural gas to be examined can be easily obtained regardless of the composition of the gas; and a device for methane number determination with which it is possible to monitor the fuel properties of a natural gas being used as a fuel gas. In the present invention, a specific relationship between methane number and basic calorific value is acquired in advance with respect to multiple reference gases which each consist of natural gas and which differ in methane number, and the basic calorific value of a natural gas to be examined is determined. The methane number of the gas being examined is calculated from the measured value of basic calorific value of the gas being examined and from the specific relationship.

Description

Methane number calculation method and methane number measuring apparatus

The present invention relates to a methane number calculating method and a methane number measuring apparatus.

In recent years, development and introduction of gas engines using liquefied natural gas (LNG) as a marine fuel have been progressing for the purpose of suppressing emission of nitrogen oxides (NO _x ) and reducing CO ₂ emission.
Problems related to commercialization of ships using LNG include the composition of fuel gas due to the fact that the composition of LNG differs depending on the place of production, and that the amount of fuel gas consumed varies when the gas engine starts up and when the load fluctuates. There are points that change. If the composition of the fuel gas changes, characteristics such as the calorific value and methane number of the fuel gas change, which may cause abnormal combustion such as engine knocking or misfire. Here, the methane number is an index indicating a resistance value against knocking corresponding to the octane number of a gasoline engine, and is an index evaluated with pure methane as 100 and hydrogen as 0.

In order to avoid such abnormal combustion, it is considered to be an effective means to capture the fuel properties such as the calorific value of the fuel gas and the methane number in real time and to control the combustion of the gas engine based on this data.

For example, as a method for measuring the calorific value of fuel gas such as LNG, for example, a method of measuring a physical property value having a specific correspondence relationship with the calorific value and obtaining a calorific value (converted calorie value) based on the measured value is applied. It has been proposed by a person (for example, see Patent Document 1).

On the other hand, as a method of calculating the methane number of fuel gas,
(A) A method proposed by AVL (hereinafter also referred to as “AVL standard”),
(B) A method of calculating by a specific arithmetic expression defined by the California Air Resources Council (hereinafter also referred to as “CARB standard”),
(C) A method of calculating by a method based on ISO / TR 22302 3.1.1 (hereinafter also referred to as “GRI (Lc) standard”),
(D) A method of calculating by a method based on ISO / TR 22302 3.1.2 (hereinafter also referred to as “GRI (H / C) standard”).
The four types are mainly used. Here, the methane number shows a different value depending on the calculation method even for the same fuel gas. For example, a methane number based on a different standard for each region is required.
However, since both methods calculate the methane number based on the gas composition, as described above, when the gas composition fluctuates, the gas composition is measured when calculating the methane number. Is required.

JP 2009-42216 A

Thus, for example, a gas obtained by vaporizing LNG (hereinafter referred to as “LNG vaporized gas”) usually contains an incombustible gas component, and the extent of the influence of the incombustible gas component on the calorific value. Therefore, there is no specific correlation between the calorific value (true calorific value) of the LNG vaporized gas and the value of the methane number.
However, as a result of intensive studies by the present inventors, there is a specific correlation between the value of the basic calorific value of natural gas used as the fuel gas and the value of the methane number calculated by each of the above criteria. It was found that by measuring the basic calorific value of natural gas, which is the measurement target gas, it is possible to obtain approximate solutions of the methane number corresponding to each standard. Here, the “basic heat amount” refers to the amount of combustion heat of the combustible gas component when the non-combustible gas component is removed from the natural gas. For example, in the case of LNG vaporized gas, since the non-combustible gas component can be regarded as only N ₂ , the basic heat amount of the LNG vaporized gas refers to the amount of combustion heat when N ₂ is removed from the LNG vaporized gas.

The present invention has been made based on the circumstances as described above, and for a natural gas that is a measurement object gas, a methane number that can be easily obtained regardless of the gas composition. An object is to provide a calculation method.
In addition, the present invention can easily obtain a methane number having a certain degree of reliability for natural gas, which is a measurement target gas, regardless of the gas composition, and can monitor the fuel properties of natural gas used as fuel gas. It aims at providing the methane number measuring apparatus which can be performed.

In the methane number calculation method of the present invention, a specific relational expression between the methane number and the basic calorific value is obtained in advance for a plurality of kinds of reference gases each having a different methane number value each made of natural gas,
Measure the basic calorific value of natural gas, the measurement target gas,
The methane number of the measurement target gas is calculated from the measured basic calorific value of the measurement target gas and the specific relational expression.

In the methane number calculation method of the present invention, it is preferable that the specific relational expression is represented by the following formula (1).

　但し、式（１）において、ＭＮはメタン価、ｆ_(Q´₎ は、測定対象ガスの基礎熱量Ｑ´〔ＭＪ／ｍ³ 〕の値に応じて選択される下記式（ａ）～下記式（ｄ）で表されるいずれかの関数であり、Ａは－２．０～２．０の範囲から選択される値である。

However, in the formula (1), MN is the methane number, and f _(Q ′ ₎ is selected according to the following formula (a) to the following formula selected according to the value of the basic calorie _Q ′ [MJ / m ³ ] of the measurement target gas. Any function represented by (d), and A is a value selected from the range of -2.0 to 2.0.

Further, in the methane number calculation method of the present invention, when obtaining an approximate value of the methane number calculated by a specific arithmetic expression stipulated by the California Air Resources Council, the following relation ( Those represented by 2) are used. Moreover, when acquiring the approximate value of the methane number calculated by the method based on ISO / TR 22302 3.1.1, what is represented by following formula (3) is used as said specific relational expression. Furthermore, when obtaining an approximate value of the methane number calculated by a method based on ISO / TR 22302 3.1.2, the specific relational expression represented by the following expression (4) is used. .

　但し、式（２）において、ＭＮはメタン価、ｆ´_(Q´₎ は、測定対象ガスの基礎熱量Ｑ´〔ＭＪ／ｍ³ 〕の値に応じて選択される下記式（ｅ）および下記式（ｆ）で表されるいずれかの関数であり、Ｂは－２．０～２．０の範囲から選択される値である。

However, in the formula (2), MN is the methane number, and f ′ _(Q ′ ₎ is selected according to the following formula (e) and the following formula selected according to the value of the basic calorie _Q ′ [MJ / m ³ ] of the measurement target gas. Any function represented by the formula (f), and B is a value selected from the range of −2.0 to 2.0.

　但し、式（３）において、ＭＮはメタン価、Ｑ´は、測定対象ガスの基礎熱量〔ＭＪ／ｍ³ 〕、Ｃは－２．０～２．０の範囲から選択される値である。

In Equation (3), MN is the methane number, Q ′ is the basic heat quantity [MJ / m ³ ] of the gas to be measured, and C is a value selected from the range of −2.0 to 2.0.

　但し、式（４）において、ＭＮはメタン価、Ｑ´は測定対象ガスの基礎熱量〔ＭＪ／ｍ³ 〕、Ｄは－２．０～２．０の範囲から選択される値である。

In Equation (4), MN is the methane number, Q ′ is the basic heat quantity [MJ / m ³ ] of the gas to be measured, and D is a value selected from the range of −2.0 to 2.0.

In the methane number calculation method of the present invention, a specific relational expression between the methane number and the basic calorific value is obtained in advance for a plurality of kinds of reference gases made of natural gas each containing nitrogen gas and having different methane number values. ,
Measure the basic calorific value of the natural gas containing nitrogen gas that is the measurement target gas and the concentration of nitrogen gas contained in the measurement target gas,
The methane number of the measurement target gas is calculated from the measured basic calorific value of the measurement target gas, the nitrogen gas concentration value, and the specific relational expression.

In the methane number calculation method of the present invention, it is preferable that the specific relational expression is represented by the following formula (5).

　但し、式（５）において、ＭＮはメタン価、ｆ_(Q´₎ は、測定対象ガスの基礎熱量Ｑ´〔ＭＪ／ｍ³ 〕の値に応じて選択される下記式（ｇ）～下記式（ｊ）で表されるいずれかの関数であり、Ｅは－２．０～２．０の範囲から選択される値である。

However, in the formula (5), MN is the methane number, and f _(Q ′ ₎ is selected according to the following formula (g) to the following formula selected according to the value of the basic calorie _Q ′ [MJ / m ³ ] of the measurement target gas. (J) is one of the functions, and E is a value selected from the range of -2.0 to 2.0.

　但し、式（ｇ）～式（ｊ）において、Ｘ_N2 は測定対象ガスに含まれる窒素ガスの、体積百分率で示される濃度〔ｖｏｌ％〕である。

However, in the formulas (g) to (j), X _N2 is the concentration [vol%] of the nitrogen gas contained in the measurement target gas, expressed as a volume percentage.

In the methane number calculation method of the present invention, when obtaining an approximate value of the methane number calculated by a method based on ISO / TR 22302 3.1.1 for natural gas containing nitrogen gas, What is represented by the following formula (5) is preferably used as the specific relational expression.

　但し、式（６）において、ＭＮはメタン価、Ｑ´は、測定対象ガスの基礎熱量〔ＭＪ／ｍ³ 〕、Ｘ_N2 は測定対象ガスに含まれる窒素ガスの、体積百分率で示される濃度〔ｖｏｌ％〕、Ｆは－２．０～２．０の範囲から選択される値である。

However, in Formula (6), MN is the methane number, Q ′ is the basic calorific value [MJ / m ³ ] of the measurement target gas, and X _N2 is the concentration of the nitrogen gas contained in the measurement target gas expressed as a volume percentage [ vol%], F is a value selected from the range of -2.0 to 2.0.

In the above methane number calculation method of the present invention, the natural gas as the measurement target gas is preferably obtained by vaporizing liquefied natural gas.

Furthermore, in the methane number calculation method of the present invention, the basic calorific value of the measurement target gas is a refractive index conversion calorie obtained from the refractive index of the measurement target gas and a sonic conversion calorie obtained from the sound speed of the measurement target gas. It is preferable that it is obtained based on these.

The methane number measuring device of the present invention is a calorimetric mechanism that measures the basic calorific value of natural gas that is a measurement target gas;
A specific relational expression between a methane number and a basic calorific value for a plurality of kinds of reference gases made of natural gas, each of which has a different methane value, and the measurement target gas measured by the calorimetric mechanism. And a methane number calculating mechanism for calculating the methane number of the measurement target gas from the value of the basic calorific value.

In the methane number measuring apparatus of the present invention, it is preferable that the specific relational expression is represented by the above formula (1).

Furthermore, in the methane number measuring device of the present invention, the specific value represented by the above formula (2) for obtaining an approximate value of the methane number calculated by a specific arithmetic expression defined by the California Air Resources Council. Relational expression, specific relational expression represented by the above expression (3) to obtain an approximate value of methane number calculated by a method based on ISO / TR 22302 3.1.1, and ISO / TR 22302 3. It is preferable that a specific relational expression represented by the above formula (4) for obtaining an approximate value of the methane number calculated by a method based on 1.2 is further set.

The methane number measuring device of the present invention is a calorimetric mechanism for measuring the basic calorific value of natural gas containing nitrogen gas as a measurement target gas,
A concentration measuring mechanism for calculating the concentration of nitrogen gas contained in the measurement target gas;
A specific relational expression between a methane number and a basic calorific value for a plurality of kinds of reference gases made of natural gas containing nitrogen gas, each of which has a different methane number value, obtained in advance, and measured by the calorimetric mechanism. And a methane number calculating mechanism for calculating the methane number of the measurement target gas from the basic calorific value of the measurement target gas and the concentration value of the nitrogen gas measured by the concentration measurement mechanism.

In the methane number measuring apparatus of the present invention, it is preferable that the specific relational expression is represented by the above formula (5).

Furthermore, in the methane number measuring device of the present invention, the specific value represented by the above formula (2) for obtaining an approximate value of the methane number calculated by a specific arithmetic expression defined by the California Air Resources Council. Relational expression, specific relational expression represented by the above expression (6) for obtaining an approximate value of methane number calculated by a method based on ISO / TR 22302 3.1.1, and ISO / TR 22302 It is preferable that a specific relational expression represented by the above formula (4) for obtaining an approximate value of the methane number calculated by a method based on 1.2 is further set.

In the above methane number measuring apparatus of the present invention, the natural gas that is the measurement target gas is preferably obtained by vaporizing liquefied natural gas.

Furthermore, in the methane number measuring device of the present invention, the calorimetric measurement mechanism includes a refractive index converted calorific value measuring means for obtaining a refractive index converted calorie from a refractive index value of the measuring target gas, and a sound velocity value of the measuring target gas. It is preferable that the apparatus includes a sonic conversion calorie measuring unit for obtaining a sonic conversion calorie from a calorie calculating unit for calculating a basic calorie of the measurement target gas based on a refractive index conversion calorie and a sonic conversion calorie. .

According to the methane number calculation method of the present invention, by using a specific relational expression between the basic heat quantity and the methane number acquired in advance, it is only necessary to measure the value of the basic heat quantity of the measurement target gas. Can be obtained. The specific relational expression is a quantitative clarification of the correlation between the basic calorific value and the methane number, based on experiments, for multiple types of reference gas consisting of natural gas with different methane number values. The obtained methane number has a certain reliability.
Further, the correction based on the concentration of nitrogen gas contained in the gas to be measured makes the methane number obtained more reliable.

According to the methane number measuring apparatus of the present invention in which the above methane number calculation method is executed, the basic calorific value of the measurement target gas is continuously measured by the calorimetric measurement mechanism, so that the measurement target gas in accordance with the actual situation is measured. Since the methane number can be obtained continuously, the actual fuel properties of natural gas as fuel gas can be monitored. Therefore, when a change in gas composition occurs, a change in methane number accompanying a change in gas composition can be detected quickly.

It is a block diagram which shows the outline of a structure in an example of the methane number measuring apparatus of this invention. It is a graph which shows an example of the methane number calculation curve based on an AVL standard which shows the relationship between a basic calorie | heat amount and a methane number. It is a graph which shows an example of the methane number calculation curve based on CARB criteria which shows the relationship between a basic calorie | heat amount and a methane number. It is a graph which shows an example of the methane number calculation curve based on GRI (Lc) reference | standard which shows the relationship between a basic calorie | heat amount and a methane number. It is a graph which shows an example of the methane number calculation curve based on a GRI (H / C) reference | standard which shows the relationship between a basic calorie | heat amount and a methane number. It is a graph which shows the relationship between nitrogen gas concentration and methane number.

Hereinafter, embodiments of the present invention will be described in detail.
In the present invention, natural gas, specifically, LNG vaporized gas, for example, may be a gas to be measured, and may contain an incombustible gas component such as nitrogen gas. In addition, in the purification process of LNG vaporized gas, It includes those from which heavy hydrocarbon components have been removed or whose contents have been adjusted.

FIG. 1 is a block diagram showing an outline of a configuration in an example of a methane number measuring apparatus of the present invention.
The methane number measuring device includes a calorific value measuring mechanism 20 that measures the calorific value of the measurement target gas, a methane number calculation mechanism 40 that calculates the methane number of the measurement target gas, and information such as the calorific value and methane number of the measurement target gas. A display mechanism 45 for displaying is arranged in the explosion-proof container 10, for example.

The calorific value measuring mechanism 20 includes, for example, a sonic converted calorific value measuring mechanism 25 for obtaining a sonic converted calorific value Qs obtained from a sonic value of the measurement target gas, and a refractive index converted calorific value obtained from the refractive index value of the measurement target gas. Refractive index conversion calorimeter 21 for obtaining Qn, nitrogen concentration measuring mechanism 30 for measuring nitrogen gas concentration X _N2 [vol%] contained in the measurement target gas, value of calorie Qns of the measurement target gas, and And a calorific value calculation mechanism 35 for calculating the value of the basic calorific value Q ′.

The sonic-converted calorie measuring mechanism 25 is a sonic-velocity measuring unit 26 that measures the propagation speed of sound waves in the measurement-target gas (the sonic velocity of the measurement-target gas), and the sonic-converted calorific value based on the value of the sonic velocity measured by the sonic velocity measuring unit 26. Sonic-heat quantity conversion processing means 27 having a function of obtaining the value of Qs is provided.
The sonic-calorie conversion processing means 27 graphs, for example, a specific gas consisting only of a combustible gas component (paraffinic hydrocarbon gas) that does not contain an incombustible gas component (N ₂ ) in the LNG vaporized gas that is the measurement target gas. By using the correlation between the sound speed and the amount of heat acquired in advance, etc., the sound speed is obtained by contrasting the correlation assuming that the sound speed value obtained for the measurement target gas is the sound speed of the specific gas. The converted heat quantity Qs is calculated.

The refractive index converted calorific value measuring mechanism 21 has a refractive index measuring unit 22 that measures the refractive index of the gas to be measured, and a function that calculates the refractive index converted calorie Qn based on the value of the refractive index measured by the refractive index measuring unit 22. And a refractive index-heat quantity conversion processing means 23.
The refractive index-heat quantity conversion processing means 23 graphs, for example, a specific gas composed only of a combustible gas component (paraffinic hydrocarbon gas) that does not contain an incombustible gas component (N ₂ ) in the LNG vaporized gas that is the measurement target gas. Assuming that the refractive index value obtained for the measurement target gas is the refractive index of the specific gas, using the correlation between the refractive index and the amount of heat acquired in advance, etc. By contrast, the calorific value Qn in terms of refractive index is calculated.

The nitrogen concentration measuring mechanism 30 is based on the following formula based on the value of the sonic converted calorific value Qs obtained by the sonic converted calorific value measuring mechanism 25 and the value of the refractive index converted calorific value Qn obtained by the refractive index converted calorific value measuring mechanism 21. According to (7), the nitrogen gas contained in the measurement target gas under the condition of using a value selected as the correction factor α in the range of 1.1 to 4.2, preferably in the range of 2.40 to 2.60. The concentration of is calculated. X _N2 in the formula (7) is a nitrogen gas concentration [vol%] expressed as a volume percentage. K _N2 is an error coefficient and represents the magnitude of the influence of the error exerted by N ₂ as a miscellaneous gas component. The unit of the value of the sonic converted heat quantity Qs and the refractive index converted heat quantity Qn used in the calculation is [MJ / m ³ ].

The calorific value calculating mechanism 35 is based on the value of the sonic converted calorific value Qs obtained by the sonic converted calorific value measuring mechanism 25 and the refractive index converted calorific value Qn obtained by the refractive index converted calorific value measuring mechanism 21 based on the following formula ( According to 8), the value of the calorific value Qns of the measurement target gas is set under the condition that the correction factor α is a value selected within the range of 1.1 to 4.2, preferably 2.40 to 2.60 calculate. Based on the value of the heat quantity Qns thus obtained and the value of the nitrogen gas concentration X _N2 obtained by the nitrogen concentration measuring mechanism 30, the value of the basic heat quantity Q ′ [MJ / M ³ ] is calculated.

The methane number calculating mechanism 40 calculates an approximate solution of the methane number value obtained by the method based on the criterion selected from the above four criteria (a) to (d) for the LNG vaporized gas as the measurement target gas. calculate. Hereinafter, for example, for an LNG vaporized gas not containing nitrogen gas, (a) an approximate solution of a methane number value (hereinafter also referred to as “AVL value”) obtained by a method based on the AVL standard is taken as an example. Will be described in detail.

The methane number calculating mechanism 40 includes a plurality of kinds of standards composed of natural gas having different values of the methane number, which have been acquired in advance, and the basic calorific value Q ′ of the measurement target gas measured by the calorific value measuring mechanism 20. For the gas, the methane number of the measurement target gas is calculated from a specific relational expression between the value of the methane number (AVL value) obtained by a method based on the AVL standard and the value of the basic heat quantity Q ′.

For example, as shown in FIG. 2, in the coordinate system in which the horizontal axis is the basic calorie and the vertical axis is the methane number, the specific relational expression is the value of the basic calorie Q ′ and the AVL for each of the plurality of types of reference gas. An actual measurement value indicating a relationship with the value can be acquired, and the obtained actual measurement value can be acquired, for example, by approximating the curve with a polynomial. Specifically, it is preferable that the specific relational expression related to the AVL standard is represented by the above expression (1).

In the above formula (1), MN is the methane number, specifically, an approximate solution of the AVL value, and f _(Q ′ ₎ is selected according to the value of the basic heat quantity _Q ′ of the measurement target gas. ~ A function represented by the above formula (d).
A in the above formula (1) is a value selected from the range of -2.0 to 2.0. In the numerical range set for A, correction based on the fuel property of the actual LNG vaporized gas is performed on the methane number calculation curve itself, which is a reference expressed by the equation where A = 0 in Equation (1). Practical tolerance is shown. If the value of A is within the above numerical range, the error rate with respect to the AVL value of the calculated approximate solution is within 5.0% as shown in the results of the experimental example described later, and high reliability is obtained.
As a specific method for setting the value of A in the above formula (1), for example, the methane number is measured for a reference gas having a known composition, and the difference from the theoretical value (AVL value) is set as “A” (offset) Adjustment).

In the reference methane number calculation curve indicated by the solid line in FIG. 2, each of the curve portions represented by the above formulas (a) to (d) is continuous without causing an inflection point. The reference methane number calculation curve is set in consideration of, for example, the gas composition of LNG vaporized gas that may actually exist.
In FIG. 2, the curve indicated by the broken line is a methane number calculation curve in which A = 2.0 in Equation (1), and the curve indicated by the alternate long and short dash line is the methane number in which A = −2.0 in Equation (1). It is a calculated curve.
By using such a methane number calculation curve, the reliability of the calculated methane number can be further increased.

In the above description, reference numeral 11 in FIG. 1 denotes a measurement target gas introduction unit for supplying a measurement target gas to each of the sound velocity measurement unit 26 and the refractive index measurement unit 22, and 12 is necessary in the refractive index measurement unit 22 in terms of detection principle. Reference gas introduction unit 13 for introducing the reference gas to be used, 13 is a gas discharge unit. Moreover, the dashed-two dotted line in FIG. 1 shows gas piping.

The methane number measuring device is connected to a gas pipeline through an appropriate gas sampling device, for example, and the LNG vaporized gas flowing through the gas pipeline is used as a measurement target gas from the measurement target gas introduction unit 11 to measure the sonic conversion calorific value. The sound velocity measuring means 26 of the mechanism 25 and the refractive index measuring means 22 of the refractive index converted calorific value measuring mechanism 21 are sequentially supplied. On the other hand, for example, a reference gas such as air is supplied from the reference gas introducing unit 12 to the refractive index measuring means 22 of the refractive index converted calorific value measuring mechanism 21. As a result, the sound velocity converted heat quantity measurement mechanism 25 calculates the sound velocity converted heat quantity Qs, and the refractive index converted heat quantity measurement mechanism 21 calculates the refractive index converted heat quantity Qn. Then, based on the value of the sound velocity converted heat quantity Qs and the value of the refractive index converted heat quantity Qn, the value selected within the specific range as the correction factor α by the above formula (7) and the above formula (8) is used. Thus, the nitrogen gas concentration X _N2 [vol%] and the heat quantity Qns are calculated. Based on the value of the heat quantity Qns thus obtained and the value of the nitrogen gas concentration X _N2 [vol%], the basic heat quantity Q ′ of the measurement target gas is calculated by the above equation (9).
Subsequently, the value of the basic calorific value Q ′ obtained by the calorific value measuring mechanism 20 by the methane number calculating mechanism 40 and the above-mentioned specific relational expression, for example, an expression (1 representing a methane number calculating curve serving as a reference with A = 0) ), The methane number as an approximate solution of the AVL value is calculated.
The value of the methane number and the amount of heat Qns of the measurement target gas obtained as described above are displayed on the display mechanism 45.
Note that the measurement target gas and the reference gas are discharged to the outside of the apparatus through the gas discharge unit 13.

Thus, according to the above methane number calculation method, it is only necessary to measure the basic heat quantity Q ′ of the measurement target gas by using a specific relational expression between the basic heat quantity Q ′ and the methane number acquired in advance. The methane number of the measurement target gas can be obtained. The specific relational expression is quantified by supporting the correlation between the basic calorific value and the AVL value by experiment for multiple types of reference gas consisting of natural gas with different methane values (AVL values) based on the AVL standard. Therefore, the obtained methane number has a certain reliability.
Therefore, according to the methane number measuring apparatus having the above-described configuration in which such a methane number calculation method is executed, the basic calorific value Q ′ of the measurement target gas is continuously measured by the calorie measuring mechanism 20, thereby obtaining an actual situation. Since the methane number as an approximate solution of the AVL value of the measurement target gas can be continuously obtained, the actual fuel property of the natural gas as the fuel gas can be monitored. Therefore, when a change in gas composition occurs, a change in methane number accompanying a change in gas composition can be detected quickly.

Further, in the above methane number measuring device, the calorific value measuring mechanism 20 and the methane number calculating mechanism 40 are arranged in the explosion-proof container 10, so that the construction and operation of the measuring system becomes simple. In addition, the measurement does not take a considerable amount of time, and since there is no time lag between the calculation process of the basic heat quantity Q ′ and the calculation process of the methane number, the methane number can be measured in real time. it can.

Furthermore, the calorie measuring mechanism 20 is configured to calculate the calorific value of the gas to be measured based on the two calorific values calorie converted calorific value Qs and refractive index converted calorific value Qn. Since the difference from the true value of the calorific value Q of the measurement target gas is small regardless of the gas composition of the target gas, the reliability of the calculated methane number value is further increased.

As described above, when natural gas is used as fuel gas, in actuality, for example, a methane number calculated by a calculation method based on a different standard for each region is required. And (b) CARB standard, (c) GRI (Lc) standard, and (d) GRI (H / C) standard. It is preferable that In such a configuration, a specific relational expression between the value of the methane number calculated by the method based on each criterion and the value of the basic heat amount may be acquired.

(B) It is preferable that the specific relational expression based on the CARB standard is represented by the above expression (2).
The numerical range for B in the above equation (2) is the same as the numerical range for A in the above equation (1), but the actual LNG vaporized fuel of the methane number calculation curve itself as a reference with B = 0. This indicates a practical allowable range in which correction according to properties is performed. If the value of B is within the above numerical range, the error rate of the calculated methane number (approximate solution) relative to the CARB-based methane number is within 5.0%, as shown in the results of the experimental example described later. High reliability can be obtained. An example of a methane number calculation curve according to the CARB standard is shown in FIG. A curve indicated by a solid line in FIG. 3 is a reference methane number calculation curve. The reference methane number calculation curve is such that each of the curve parts represented by the above formula (e) and the above formula (f) is continuous without causing an inflection point. It is set in consideration of the gas composition of the gas. The curve indicated by the broken line in FIG. 3 is a methane number calculation curve in which B = 2.0 in Equation (2), and the curve indicated by the alternate long and short dash line is the methane number in which B = −2.0 in Equation (2). It is a calculated curve.
The value of B in the above equation (2) can be set by the same method as the method of setting the value of A in the above equation (1), for example.

(C) It is preferable that the specific relational expression based on the GRI (Lc) standard is represented by the above formula (3).
C in the above formula (3) is a value selected from the range of −2.0 to 2.0, and this numerical range is C = 0 as in the numerical range for A in the above formula (1). The practical allowable range in which the methane number calculation curve itself serving as a reference is corrected in accordance with the actual fuel properties of the LNG vaporized gas is shown. If the value of C is within the above numerical range, the error rate of the calculated methane number (approximate solution) with respect to the methane number based on the GRI (Lc) is 5.0 as shown in the result of an experimental example described later. %, And high reliability is obtained. An example of the methane number calculation curve according to the GRI (Lc) standard is shown in FIG. A curve indicated by a solid line in FIG. 4 is a methane number calculation curve serving as a reference in which C = 0 in Equation (3). The curve indicated by the broken line is a methane number calculation curve in which C = 2.0 in the formula (3), and the curve indicated by the alternate long and short dash line is a methane number calculation in which C = −2.0 in the formula (3). It is a curve.
The value of C in the above equation (3) can be set, for example, by the same method as the method for setting the value of A in the above equation (1).

(D) It is preferable that the specific relational expression based on the GRI (H / C) standard is represented by the above formula (4).
D in the above formula (4) is a value selected from the range of −2.0 to 2.0, and this numerical range is D = 0 similarly to the numerical range for A in the above formula (1). The practical allowable range in which the methane number calculation curve itself serving as a reference is corrected in accordance with the actual fuel properties of the LNG vaporized gas is shown. If the value of D is within the above numerical range, the error rate of the calculated methane number (approximate solution) with respect to the methane number based on the GRI (H / C) is 5 as shown in the result of an experimental example described later. Within 0.0%, high reliability is obtained. An example of a methane number calculation curve according to the GRI (H / C) standard is shown in FIG. A curve indicated by a solid line in FIG. 5 is a methane number calculation curve serving as a reference in which D = 0 in Equation (4). Moreover, the curve shown with a broken line is a methane number calculation curve which set D = 2.0 in Formula (4), and the curve shown with a dashed-dotted line is the methane number calculation curve which set D = 2.0 in Formula (4). It is.
The value of D in the above equation (4) can be set, for example, by the same method as the method of setting the value of A in the above equation (1).

In the methane number measuring apparatus having such a configuration, the display mechanism 45 is calculated from each of the plurality of specific relational expressions and the basic calorific value measured by the calorimeter measuring mechanism 20 for the same measurement target gas. Even if it has a function to display a plurality of methane values according to each standard at the same time, or a function to display the methane value according to the selected standard so as to be switchable with another, it may be either . With such a configuration, it is possible to obtain a methane number according to a required standard, so that high convenience can be obtained.

In the above description, for example, the case where the methane number of the measurement target gas that is an LNG vaporized gas not containing nitrogen gas is calculated has been described. However, when the measurement target gas contains nitrogen gas, there is no practical problem. However, a measurement error occurs due to the nitrogen gas contained. However, as a result of intensive studies by the present inventors, for example, there is a specific correlation between the concentration of nitrogen gas contained in the LNG vaporized gas and the variation amount (error) of the methane number caused by the nitrogen gas concentration. As a result, it has been found that an approximate solution of the methane number corresponding to each standard can be obtained with higher reliability by correcting with a correction amount according to the nitrogen gas concentration.

Hereinafter, for example, for an LNG vapor containing nitrogen gas, (a) a case where an approximate solution of a methane value (AVL value) obtained by a method based on the AVL standard will be described as an example.

When calculating the methane number, when performing correction based on the concentration of nitrogen gas contained in the measurement target gas, the methane number calculation mechanism 40 determines the basic calorie Q ′ of the measurement target gas measured by the calorific measurement mechanism 20. Of nitrogen gas concentration X _N2 [vol%] obtained by the value and nitrogen measurement calculation mechanism 35, the value of methane number (AVL value) obtained by the method based on the AVL standard, and the value of basic heat quantity Q ′ From the relational expression, the function of calculating the methane number of the measurement target gas is assumed.

The specific relational expression relating to the AVL standard for the LNG vaporized gas containing nitrogen gas is preferably represented by the above formula (5). This specific relational expression is obtained by the same method as the specific relational expression expressed by the expression (1) related to the AVL standard.
In the above equation (5), MN is the methane number, specifically, an approximate solution of the AVL value, and f _(Q ′ ₎ is selected according to the value of the basic heat quantity _Q ′ of the measurement target gas. Is any function represented by the above formula (j), and E is a value selected from the range of -2.0 to 2.0.
The term of 0.320 × _{N2 in} the above formulas (g) to (j) represents the methane number correction amount based on the nitrogen gas concentration. For example, as shown in FIG. 6, the correction amount of the methane number is a coordinate system in which the horizontal axis represents the concentration (vol%) of the nitrogen gas contained in the measurement target gas, and the vertical axis represents the methane number. For each of a plurality of types of reference gases having different methane values, an actual measurement value indicating the relationship between the nitrogen gas concentration value X _N2 [vol%] and the AVL value is obtained, and the obtained actual measurement value is, for example, linear This is set based on the approximate straight line obtained by approximation. As is apparent from FIG. 6, it is understood that the approximate curves for the respective reference gases have the same magnitude of inclination.
The numerical range set for E in the above equation (5) is based on the actual fuel properties of the LNG vaporized gas in the methane number calculation curve itself, which is the reference expressed by the equation where E = 0 in equation (5). Practical tolerances for the corrections made are shown. If the value of E is within the above numerical range, the error of the calculated methane number (approximate solution) with respect to the AVL value is within 5.0% as shown in the result of the experimental example described later, and the reliability is high. Is obtained.
The value of E in the above equation (5) can be set by the same method as the method of setting the value of A in the above equation (1), for example.

In such a methane number measuring device, based on the value of the sonic converted calorific value Qs obtained by the sonic converted calorific value measuring mechanism 25 and the value of the refractive index converted calorific value Qn obtained by the refractive index converted calorific value measuring mechanism 21. The nitrogen gas concentration X _N2 [vol%] and the calorific value Qns are calculated by the above formula (7) and the above formula (8) using the value selected within the specific range as the correction factor α. Then, based on the value of the heat quantity Qns thus obtained and the value of the nitrogen gas concentration X _N2 [vol%], the basic heat quantity Q ′ of the measurement target gas is calculated by the above equation (9). .
Next, the value of the basic calorific value Q ′ and the nitrogen gas concentration value X _N2 [vol%] obtained by the calorific value measuring mechanism 20 are determined by the methane number calculating mechanism 40 and, for example, E = 0 in the above formula (5) From the relational expression, the methane number as an approximate solution of the AVL value is calculated.

Thus, according to the above methane number calculation method, by using the correlation between the nitrogen gas concentration X _N2 and the methane number quantitatively clarified through experimental support, the nitrogen contained in the measurement target gas Since the error caused by the gas is compensated, the methane number of the measurement target gas can be obtained with higher reliability.
Therefore, according to the methane number measuring apparatus having the above configuration in which such a methane number calculation method is executed, the methane number as an approximate solution of the AVL value of the measurement target gas in accordance with the actual situation can be obtained with higher reliability. Since continuous acquisition is possible, the actual fuel properties of natural gas as fuel gas can be monitored more reliably.

Moreover, it is preferable that the specific relational expression based on the (c) GRI (Lc) standard for, for example, the LNG vaporized gas containing nitrogen gas is represented by the above formula (6).
F in the above formula (6) is a value selected from the range of −2.0 to 2.0, and this numerical range is F = 0 as in the numerical range for A in the above formula (1). The practical allowable range in which the methane number calculation curve itself serving as a reference is corrected in accordance with the actual fuel properties of the LNG vaporized gas is shown. If the value of F is within the above numerical range, the error rate of the calculated methane number (approximate solution) with respect to the methane number based on the GRI (Lc) is 5.0 as shown in the result of the experimental example described later. %, And high reliability is obtained.
The value of F in the above equation (6) can be set, for example, by the same method as the method of setting the value of A in the above equation (1).

(B) When calculating the methane number according to the CARB standard and the (d) methane number according to the GRI (H / C) standard, the above formula (2) is used regardless of the concentration of nitrogen gas contained in the measurement target gas. And a specific relational expression represented by the above formula (4) are used.

As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment, A various change can be added.
In the present invention, the calorific measurement mechanism is not limited to the one having the above-described configuration, and an apparatus having a configuration for obtaining a calorific value based on a thermal conductivity converted calorific value and a refractive index converted calorific value. May be used. Further, one of the physical property values having a specific correspondence with the amount of heat, for example, one selected from refractive index, thermal conductivity, and sound velocity is measured, and the amount of heat is obtained based on the measured value. May be. Even if the basic calorific value calculated based on the calorific value of the gas to be measured obtained in this way is used, a methane value within a predetermined allowable range can be obtained with respect to the methane value based on each standard. Can do.

Hereinafter, experimental examples of the present invention will be described.

[Experimental Example 1]
Eleven types of sample gases having the gas compositions shown in Table 1 below were prepared, and the methane number of each of the sample gases A to K was measured using the methane number measuring apparatus having the configuration shown in FIG. The methane number was calculated using a specific relational expression in which A = 0 in the above formula (1). When the value of the basic heat quantity Q ′ measured for the sample gas is 42.0 [MJ / m ³ ] or less, the above formula (a) is selected, and the value of the basic heat quantity Q ′ is 42.0. When it is larger than [MJ / m ³ ] and 55.0 [MJ / m ³ ] or less, the above formula (b) is selected, and the value of the basic heat quantity Q ′ is 55.0 [MJ / m ³ ]. If it is larger and 63.0 [MJ / m ³ ] or less, the above formula (c) is selected, and if the value of the basic heat quantity Q ′ is larger than 63.0 [MJ / m ³ ], The above formula (d) was selected. Further, except that the specific relational expression in which A = −2.0 and the specific relational expression in which A = 2.0 were used in the above formula (1), the same method as in Experimental Example 1 was used. The methane number of each sample gas A to K was calculated. The results are shown in Table 2 below.

Calculated for each sample gas A to K based on the basic calorific value when the methane number calculated based on the gas composition is set to a true value by a method based on the AVL standard (Methane number calculation software manufactured by AVL). The error rate with respect to the true value of the calculated methane number value (calorie value) was calculated. The error rate is a value obtained by [(absolute value of error) / true value] × 100 [%]. The following table shows the maximum error rate with respect to the true value of the methane number value (heat value conversion value) calculated when the value of A in the above formula (1) is set within the range of -2.0 to 2.0. It is shown in 2.

[Experimental example 2]
The methane number of each of the sample gases A to K was calculated by the same method as in Experimental Example 1, except that a specific relational expression with B = 0 in the above formula (2) was used. In the calculation of the methane number, when the value of the basic heat quantity Q ′ measured for the sample gas is 55.0 [MJ / m ³ ] or less, the above formula (e) is selected, and the basic heat quantity Q ′ When the value was larger than 55.0 [MJ / m ³ ], the above formula (f) was selected. In addition to using the specific relational expression in which B = −2.0 in the above formula (2) and the specific relational expression in which B = 2.0 in the above formula (2), an experimental example 1 was used to calculate the methane number of each sample gas A to K. The results are shown in Table 3 below.
For each sample gas A to K, the methane number calculated based on the basic calorific value (calculated in terms of calorific value) when the methane number calculated based on the gas composition is set to the true value by a method based on the CARB standard. Value) with respect to the true value was calculated. The following table shows the maximum error rate with respect to the true value of the methane number (heat value conversion value) calculated when the value of B in the above formula (2) is set within the range of -2.0 to 2.0. 3 shows.

[Experimental Example 3]
The methane number of each of the sample gases A to K was calculated by the same method as in Experimental Example 1, except that a specific relational expression where C = 0 was used in the above formula (3). In addition to the use of the specific relational expression in which C = −2.0 in the above formula (3) and the specific relational expression in which C = 2.0 in the above formula (3), an experimental example 1 was used to calculate the methane number of each sample gas A to K. The results are shown in Table 4 below.
For each sample gas A to K, the value of the methane number calculated based on the basic calorific value when the methane number calculated based on the gas composition is regarded as a true value by a method based on the GRI (Lc) standard The error rate [%] with respect to the true value of the (heat value converted value) was calculated. The maximum value of the error rate for the true value of the methane number value (heat value conversion value) calculated when the value of C in the above formula (3) is set within the range of -2.0 to 2.0 is shown in the table below. 4 shows.

[Experimental Example 4]
The methane number of each of the sample gases A to K was calculated in the same manner as in Experimental Example 1 except that a specific relational expression with D = 0 in the above formula (4) was used. In addition to the fact that the specific relational expression in which D = −2.0 in the above formula (4) and the specific relational expression in which D = 2.0 in the above formula (4) were used, experimental examples 1 was used to calculate the methane number of each sample gas A to K. The results are shown in Table 5 below.
For each sample gas A to K, the methane number calculated based on the basic calorific value when the methane number calculated based on the gas composition is assumed to be a true value by a method based on the GRI (H / C) standard. The error rate [%] with respect to the true value of the value (heat value converted value) was calculated. The following table shows the maximum error rate with respect to the true value of the methane number value (heat value conversion value) calculated when the value of D in the above formula (4) is set within the range of -2.0 to 2.0. As shown in FIG.

[Experimental Example 5]
Eleven types of sample gas having the gas composition shown in Table 6 below were prepared, and the methane number of each of the sample gases a to k was measured using the methane number measuring apparatus having the configuration shown in FIG. The calculation of the methane number utilized a specific relational expression in which E = 0 in the above formula (5). When the value of the basic heat quantity Q ′ measured for the sample gas is 42.0 [MJ / m ³ ] or less, the above formula (g) is selected, and the value of the basic heat quantity Q ′ is 42.0. When it is larger than [MJ / m ³ ] and 55.0 [MJ / m ³ ] or less, the above formula (h) is selected, and the value of the basic heat quantity Q ′ is 55.0 [MJ / m ³ ]. If it is larger and 63.0 [MJ / m ³ ] or less, the above formula (i) is selected, and if the value of the basic heat quantity Q ′ is larger than 63.0 [MJ / m ³ ], The above formula (j) was selected. In addition, except that the specific relational expression in which E = −2.0 and the specific relational expression in which E = 2.0 are used in the above formula (5), each of the respective methods is performed in the same manner. The methane number of the sample gases a to k was measured. The results are shown in Table 7 below.

For each of the sample gases a to k, calculated based on the basic calorific value when the methane number calculated based on the gas composition is assumed to be a true value by a method based on the AVL standard (AVL's methane number calculation software) The error rate [%] with respect to the true value of the value of the methane number (calorific value converted value) was calculated. The error rate is a value obtained by [(absolute value of error) / true value] × 100 [%]. The following table shows the maximum error rate with respect to the true value of the methane number (heat value conversion value) calculated when the value of E in the above formula (5) is set within the range of -2.0 to 2.0. 7 shows.

[Experimental Example 6]
The methane number of each of the sample gases a to k was calculated by the same method as in Experimental Example 5, except that a specific relational expression with B = 0 in the above formula (2) was used. In the calculation of the methane number, when the value of the basic heat quantity Q ′ measured for the sample gas is 55.0 [MJ / m ³ ] or less, the above formula (e) is selected, and the basic heat quantity Q ′ When the value was larger than 55.0 [MJ / m ³ ], the above formula (f) was selected. In addition to using the specific relational expression in which B = −2.0 in the above formula (2) and the specific relational expression in which B = 2.0 in the above formula (2), an experimental example 5 was used to calculate the methane number of each of the sample gases a to k. The results are shown in Table 8 below.
For each of the sample gases a to k, the methane number calculated based on the basic calorific value (calculated in terms of calorific value) with the methane number calculated based on the gas composition as a true value by a method based on the CARB standard Value) with respect to the true value was calculated. The following table shows the maximum error rate with respect to the true value of the methane number (heat value conversion value) calculated when the value of B in the above formula (2) is set within the range of -2.0 to 2.0. It is shown in FIG.

[Experimental Example 7]
The methane number of each of the sample gases a to k was calculated by the same method as in Experimental Example 5 except that the specific relational expression in which F = 0 was used in the above formula (6). In addition to using the specific relational expression in which F = −2.0 in the above formula (6) and the specific relational expression in which F = 2.0 in the above formula (6) are used, 5 was used to calculate the methane number of each of the sample gases a to k. The results are shown in Table 9 below.
For each of the sample gases a to k, the value of the methane number calculated based on the basic calorific value when the methane number calculated based on the gas composition is regarded as a true value by a method based on the GRI (Lc) standard The error rate [%] with respect to the true value of the (heat value converted value) was calculated. The following table shows the maximum error rate with respect to the true value of the methane number value (heat value conversion value) calculated when the F value in the above formula (6) is set within the range of -2.0 to 2.0. 9 shows.

[Experimental Example 8]
The methane number of each of the sample gases a to k was calculated by the same method as in Experimental Example 5 except that a specific relational expression with D = 0 in the above formula (4) was used. In addition to the fact that the specific relational expression in which D = −2.0 in the above formula (4) and the specific relational expression in which D = 2.0 in the above formula (4) were used, experimental examples 5 was used to calculate the methane number of each of the sample gases a to k. The results are shown in Table 10 below.
For each of the sample gases a to k, the methane number calculated based on the basic calorific value when the methane number calculated based on the gas composition is assumed to be a true value by a method based on the GRI (H / C) standard. The error rate [%] with respect to the true value of the value (heat value converted value) was calculated. The following table shows the maximum error rate with respect to the true value of the methane number value (heat value conversion value) calculated when the value of D in the above formula (4) is set within the range of -2.0 to 2.0. 10 shows.

From the above results, according to the methane number calculation method according to the present invention, the composition of the sample gas can be determined regardless of the AVL standard, CARB standard, GRI (Lc) standard, or GRI (H / C) standard. Nevertheless, it was confirmed that the methane number (approximate solution) having a value within a certain error range can be calculated with respect to the methane number according to these standards. Here, if the error rate is within 5.0%, it can be said that the error has a practically no problem.

Since the present invention can detect in real time a change in fuel properties such as a change in methane number and a change in calorific value due to a change in the gas composition of natural gas as a fuel gas, combustion control of an LNG fuel engine can be performed. In doing so, it is expected to be extremely useful.

DESCRIPTION OF SYMBOLS 10 Explosion-proof container 11 Measurement target gas introduction part 12 Reference gas introduction part 13 Gas discharge part 20 Calorie measurement mechanism 21 Refractive index conversion calorie measurement mechanism 22 Refractive index measurement means 23 Refractive index-calorie conversion processing means 25 Sonic conversion calorie measurement mechanism 26 Sonic velocity measurement means 27 Sonic velocity-calorie conversion processing means 30 Nitrogen concentration measurement mechanism 35 Calorific value calculation mechanism 40 Methane number calculation mechanism 45 Display mechanism

Claims (20)

Acquire in advance a specific relational expression between the methane number and the basic calorific value for a plurality of kinds of reference gases each consisting of natural gas and having different methane number values,
Measure the basic calorific value of natural gas, the measurement target gas,
A methane number calculation method, comprising: calculating a methane number of the measurement target gas from the measured value of the basic calorific value of the measurement target gas and the specific relational expression. The methane number calculation method according to claim 1, wherein the natural gas that is the measurement target gas is obtained by vaporizing liquefied natural gas. The methane number calculation method according to claim 2, wherein the specific relational expression is represented by the following expression (1).

However, in the formula (1), MN is the methane number, and f _(Q ′ ₎ is selected according to the following formula (a) to the following formula selected according to the value of the basic calorie _Q ′ [MJ / m ³ ] of the measurement target gas. Any function represented by (d), and A is a value selected from the range of -2.0 to 2.0.

The specific relational expression is represented by the following expression (2), and an approximate value of a methane number calculated by a specific arithmetic expression defined by the California Air Resources Council is obtained. The methane number calculation method according to claim 2.

However, in the formula (2), MN is the methane number, and f ′ _(Q ′ ₎ is selected according to the following formula (e) and the following formula selected according to the value of the basic calorie _Q ′ [MJ / m ³ ] of the measurement target gas. Any function represented by the formula (f), and B is a value selected from the range of −2.0 to 2.0.

The specific relational expression is represented by the following expression (3), and an approximate value of the methane number calculated by a method based on ISO / TR 22302 3.1.1 is obtained. Item 3. The method for calculating the methane number according to Item 2.

In Equation (3), MN is the methane number, Q ′ is the basic heat quantity [MJ / m ³ ] of the gas to be measured, and C is a value selected from the range of −2.0 to 2.0. The specific relational expression is represented by the following expression (4), and an approximate value of a methane number calculated by a method based on ISO / TR 22302 3.1.2 is obtained. Item 3. The method for calculating the methane number according to Item 2.

In Equation (4), MN is the methane number, Q ′ is the basic heat quantity [MJ / m ³ ] of the gas to be measured, and D is a value selected from the range of −2.0 to 2.0. Acquire in advance a specific relational expression between the methane number and the basic calorific value for a plurality of kinds of reference gases made of natural gas each containing nitrogen gas and having different methane number values,
Measure the basic calorific value of the natural gas containing nitrogen gas that is the measurement target gas and the concentration of nitrogen gas contained in the measurement target gas,
A methane number calculation method, comprising: calculating a methane number of a measurement target gas from the measured basic calorific value and nitrogen gas concentration value of the measurement target gas and the specific relational expression. The methane number calculation method according to claim 7, wherein the natural gas that is the measurement target gas is obtained by vaporizing liquefied natural gas. The methane number calculation method according to claim 8, wherein the specific relational expression is represented by the following expression (5).

However, in the formula (5), MN is the methane number, and f _(Q ′ ₎ is selected according to the following formula (g) to the following formula selected according to the value of the basic calorie _Q ′ [MJ / m ³ ] of the measurement target gas. (J) is one of the functions, and E is a value selected from the range of -2.0 to 2.0.

However, in the formulas (g) to (j), X _N2 is the concentration [vol%] of the nitrogen gas contained in the measurement target gas, expressed as a volume percentage. The specific relational expression is represented by the following expression (6), and an approximate value of a methane number calculated by a method based on ISO / TR 22302 3.1.1 is obtained. Item 9. The method for calculating the methane number according to Item 8.

However, in Formula (6), MN is the methane number, Q ′ is the basic calorific value [MJ / m ³ ] of the measurement target gas, and X _N2 is the concentration of the nitrogen gas contained in the measurement target gas expressed as a volume percentage [ vol%], F is a value selected from the range of -2.0 to 2.0. The basic heat amount of the measurement target gas is obtained based on a refractive index conversion heat amount obtained from the refractive index of the measurement target gas and a sound velocity conversion heat amount obtained from the sound speed of the measurement target gas. The methane number calculation method according to any one of claims 1 to 10. A calorimetric mechanism that measures the basic calorific value of natural gas, which is the gas to be measured;
A specific relational expression between a methane number and a basic calorific value for a plurality of kinds of reference gases made of natural gas, each of which has a different methane value, and the measurement target gas measured by the calorimetric mechanism. And a methane number calculating mechanism for calculating the methane number of the measurement target gas from the basic calorific value of the methane number measuring device. The methane number measuring apparatus according to claim 12, wherein the natural gas as the measurement target gas is obtained by vaporizing liquefied natural gas. The methane number measuring apparatus according to claim 13, wherein the specific relational expression is represented by the following expression (1).

However, in the formula (1), MN is the methane number, and f _(Q ′ ₎ is selected according to the following formula (a) to the following formula selected according to the value of the basic calorie _Q ′ [MJ / m ³ ] of the measurement target gas. Any function represented by (d), and A is a value selected from the range of -2.0 to 2.0.

A specific relational expression expressed by the following formula (2) for obtaining an approximate value of the methane number calculated by a specific arithmetic expression defined by the California Air Resources Council, ISO / TR 22302 3.1.1 A specific relational expression represented by the following formula (3) for obtaining an approximate value of the methane number calculated by a compliant method, and a methane number calculated by a method based on ISO / TR 22302 3.1.2 The methane number measuring apparatus according to claim 14, further comprising a specific relational expression represented by the following formula (4) for obtaining an approximate value of:

However, MN in the formulas (2) to (4) is a methane number. In the formula (2), f ′ _(Q ′ ₎ is represented by the following formula (e) and the following formula (f) selected according to the value of the basic heat quantity _Q ′ [MJ / m ³ ] of the measurement target gas. B is a value selected from the range of -2.0 to 2.0. Moreover, in Formula (3) and Formula (4), Q 'is the basic calorie | heat amount Q' [MJ / m < ³ >] of measurement object gas. C in the formula (3) is a value selected from the range of −2.0 to 2.0. D in the formula (4) is a value selected from the range of −2.0 to 2.0.

A calorimetric mechanism for measuring the basic calorific value of natural gas containing nitrogen gas, which is the gas to be measured;
A concentration measurement mechanism for measuring the concentration of nitrogen gas contained in the measurement target gas;
A specific relational expression between a methane number and a basic calorific value for a plurality of kinds of reference gases made of natural gas containing nitrogen gas, each of which has a different methane number value, obtained in advance, and measured by the calorimetric mechanism. A methane number calculating mechanism for calculating the methane number of the measurement target gas from the value of the basic calorific value of the measurement target gas and the value of the nitrogen gas concentration measured by the concentration measurement mechanism. Value measuring device. The methane number measuring apparatus according to claim 16, wherein the natural gas that is the measurement target gas is obtained by vaporizing liquefied natural gas. The methane number measuring apparatus according to claim 17, wherein the specific relational expression is represented by the following expression (5).

However, in the formula (5), MN is the methane number, and f _(Q ′ ₎ is selected according to the following formula (g) to the following formula selected according to the value of the basic calorie _Q ′ [MJ / m ³ ] of the measurement target gas. (J) is one of the functions, and E is a value selected from the range of -2.0 to 2.0.

However, in the formulas (g) to (j), X _N2 is the concentration [vol%] of the nitrogen gas contained in the measurement target gas, expressed as a volume percentage. A specific relational expression expressed by the following formula (2) for obtaining an approximate value of the methane number calculated by a specific arithmetic expression defined by the California Air Resources Council, ISO / TR 22302 3.1.1 A specific relational expression represented by the following formula (6) for obtaining an approximate value of the methane number calculated by a compliant method, and a methane number calculated by a method based on ISO / TR 22302 3.1.2 The methane number measuring apparatus according to claim 18, further comprising a specific relational expression represented by the following formula (4) for obtaining an approximate value of:

However, MN in Formula (2), Formula (4), and Formula (6) is a methane number. In the formula (2), f ′ _(Q ′ ₎ is represented by the following formula (e) and the following formula (f) selected according to the value of the basic heat quantity _Q ′ [MJ / m ³ ] of the measurement target gas. B is a value selected from the range of -2.0 to 2.0. Q ′ in the formulas (4) and (6) is the basic heat quantity [MJ / m ³ ] of the measurement target gas. D in the formula (4) is a value selected from the range of −2.0 to 2.0. In formula (6), X _N2 is the concentration (vol%) of the nitrogen gas contained in the gas to be measured, expressed as a volume percentage, and F is a value selected from the range of −2.0 to 2.0.

The calorimetric mechanism includes a refractive index-converted calorie measuring means for obtaining a refractive index-converted calorie from a refractive index value of the measurement target gas, and a sonic-converted calorific value measuring means for obtaining a sonic speed-converted calorie from the sound velocity value of the measurement target gas; The methane number according to any one of claims 12 to 19, further comprising calorific value calculation means for calculating a basic calorific value of the measurement target gas based on a refractive index-converted calorific value and a sound velocity-converted calorific value. measuring device.

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