Gas analysis apparatus and gas analysis method

Abstract

The present invention includes a first flow path through which a sample gas flows, a first analyzer that is provided in the first flow path to measure total hydrocarbon concentration in the sample gas, a second flow path through which the sample gas flows, a non-methane non-ethane cutter that is provided in the second flow path to remove the hydrocarbon components other than the methane and the ethane in the sample gas, a second analyzer that is provided downstream of the non-methane non-ethane cutter in the second flow path to measure the total methane ethane concentration of the methane and the ethane in the sample gas, and a calculation part that calculates the concentration of the hydrocarbon components other than the methane and the ethane in the sample gas with use of the total hydrocarbon concentration by the first analyzer and the total methane ethane concentration by the second analyzer.

Claims

1. A gas analysis apparatus comprising: a first flow path through which sample gas flows; a first analyzer that is provided in the first flow path to measure total hydrocarbon concentration in the sample gas; a second flow path through which the sample gas flows; a non-methane non-ethane cutter that is provided in the second flow path to remove hydrocarbon components other than methane and ethane in the sample gas; a second analyzer that is provided downstream of the non-methane non-ethane cutter in the second flow path to measure total methane ethane concentration of the methane and the ethane in the sample gas; and a calculation part that calculates concentration of the hydrocarbon components other than the methane and the ethane in the sample gas with use of the total hydrocarbon concentration by the first analyzer and the total methane ethane concentration by the second analyzer.

2. The gas analysis apparatus according to claim 1, wherein the second analyzer is calibrated with ethane used and passed through the non-methane non-ethane cutter.

3. The gas analysis apparatus according to claim 1, wherein the calculation part calculates the concentration of the hydrocarbon components other than the methane and the ethane in the sample gas with use of the total hydrocarbon concentration by the first analyzer, the total methane ethane concentration by the second analyzer, and specific organic matter penetrability that is a ratio at which specific organic matter having a carbon number of 3 or more passes through the non-methane non-ethane cutter.

4. The gas analysis apparatus according to claim 1, wherein the calculation part calculates the concentration of the hydrocarbon components other than the methane and the ethane in the sample gas in accordance with an expression below: $\begin{array}{cc}\left[\mathrm{Expression}4\right]& \\ x_{\mathrm{NMNEHC}}=\frac{x_{\mathrm{TCH}\left[\mathrm{THC}-\mathrm{FID}\right]}-x_{\mathrm{THC}\left[\mathrm{NMNEC}-\mathrm{FID}\right]}}{1-{\mathrm{PF}}_{C_3{H}_8\left[\mathrm{HMNEC}-\mathrm{FID}\right]}}& \end{array}$ x.sub.NMNEHC: the concentration of the hydrocarbon components other than the methane and the ethane in the sample gas x.sub.THC[THC-FID]: the total hydrocarbon concentration by the first analyzer x.sub.THC[NMNEC-FID]: the total methane ethane concentration by the second analyzer PF.sub.C3H8[THC-FID]: the specific organic matter penetrability that is a ratio at which the specific organic matter having a carbon number of 3 or more passes through the non-methane non-ethane cutter.

5. The gas analysis apparatus according to claim 1, wherein the second flow path is provided with a heating part that increases temperature of the non-methane non-ethane cutter to 200 to 250° C.

6. The gas analysis apparatus according to claim 1, further comprising: a first flow rate regulating mechanism provided in the first flow path; and a second flow rate regulating mechanism provided in the second flow path, wherein the first flow rate regulating mechanism and the second flow rate regulating mechanism match response timing between the first analyzer and the second analyzer.

7. The gas analysis apparatus according to claim 1, further comprising: a third flow path through which the sample gas flows; a non-methane cutter that is provided in the third flow path to remove hydrocarbon components other than the methane in the sample gas; and a third analyzer that is provided downstream of the non-methane cutter in the third flow path to measure methane concentration in the sample gas.

8. The gas analysis apparatus according to claim 7, wherein the calculation part calculates concentration of the hydrocarbon components other than the methane in the sample gas with use of the total hydrocarbon concentration by the first analyzer and the methane concentration by the third analyzer.

9. The gas analysis apparatus according to claim 7, wherein the calculation part calculates ethane concentration in the sample gas with use of the total methane ethane concentration by the second analyzer and the methane concentration by the third analyzer.

10. The gas analysis apparatus according to claim 7, wherein the third flow path is provided with a heating part that increases temperature of the non-methane cutter to 300° C. or more.

11. The gas analysis apparatus according to claim 10, further comprising a third flow rate regulating mechanism provided in the third flow path, wherein the first flow rate regulating mechanism, the second flow rate regulating mechanism, and the third flow rate regulating mechanism match response timing among the first analyzer, the second analyzer, and the third analyzer.

12. A gas analysis apparatus calibration method for the gas analysis apparatus according to claim 1, the gas analysis apparatus calibration method calibrating the second analyzer with ethane used and passed through the non-methane non-ethane cutter.

13. The gas analysis apparatus calibration method according to claim 12, calibrating the first analyzer with use of propane.

14. A gas analysis method using the gas analysis apparatus according to claim 1, the gas analysis method using Expression (A) below in a case where the first analyzer is calibrated with use of propane:
x.sub.THC[THC-FID]=x.sub.CH4×RF.sub.CH4[THC-FID]+x.sub.C2H6×RF.sub.C2H6[THC-FID]+x.sub.NMNEHC  Expression (A): x.sub.THC[THC-FID]: the total hydrocarbon concentration by the first analyzer x.sub.CH4: methane concentration in the sample gas RF.sub.CH4[THC-FID]: a methane response factor in the first analyzer x.sub.C2H6: ethane concentration in the sample gas RF.sub.C2H6[THC-FID]: an ethane response factor in the first analyzer x.sub.NMNEHC: concentration of the hydrocarbon components other than the methane and the ethane in the sample gas, and Expression (B) below in a case where the second analyzer is calibrated with ethane used and passed through the non-methane non-ethane cutter
x.sub.THC[NMNEC-FID]=x.sub.CH4×RF.sub.CH4[NMNEC-FID]×PF.sub.CH4[NMNEC-FID]+x.sub.C2H6+x.sub.NMNEHC×RF.sub.C3H8[NMNEC-FID]×PF.sub.C3H8[NMNEC-FID]  Expression (B): x.sub.THC[NMNEC-FID]: the total methane ethane concentration by the second analyzer RF.sub.CH4[NMNEC-FID]: a methane response factor in the second analyzer RF.sub.C3H8[NMNEC-FID]: methane penetrability in the second analyzer RF.sub.C3H8[NMNEC-FID] a propane response factor in the second analyzer PF.sub.C3H8[NMNEC-FID]: propane penetrability in the second analyzer to derive Expression (1) below: $\begin{array}{cc}\left[\mathrm{Expression}5\right]& \\ x_{\mathrm{NMNEHC}}=\frac{x_{\mathrm{THC}\left[\mathrm{THC}-\mathrm{FID}\right]}-x_{\mathrm{THC}\left[\mathrm{NMNEC}-\mathrm{FID}\right]}}{1-{\mathrm{PF}}_{C_3{H}_8\left[\mathrm{NMNEC}-\mathrm{FID}\right]}}& \left(1\right)\end{array}$ x.sub.NMNEHC: the concentration of the hydrocarbon components other than the methane and the ethane in the sample gas x.sub.THC[THC-FID]: the total hydrocarbon concentration by the first analyzer x.sub.THC[NMNEC-FID]: the total methane ethane concentration by the second analyzer PF.sub.C3H8[NMNEC-FID]: specific organic matter penetrability that is a ratio at which specific organic matter having a carbon number of 3 or more (in this case, propane C.sub.3H.sub.8) passes through the non-methane non-ethane cutter, and calculating the concentration of the hydrocarbon components other than the methane and the ethane in the sample gas with use of Expression (1) above.

15. The gas analysis method according to claim 14, in the Expression (A), considering the ethane response factor RF.sub.C2H6[THC-FID] as 1.0 to derive Expression (A′) below:
x.sub.THC[THC-FID]=x.sub.CH4×RF.sub.CH4[THC-FID]+x.sub.C2H6+x.sub.NMNEHC  Expression (A′): in the Expression (B), considering PF.sub.CH4[NMNEC-FID] as 1.0, and also considering the propane response factor in the second analyzer subjected to ethane calibration as 1.0 to derive Expression (B′) below:
x.sub.THC[NMNEC-FID]=x.sub.CH4×RF.sub.CH4[NMNEC-FID]+x.sub.C2H6+x.sub.NMNEHC×PF.sub.C3H8[NMNEC-FID]  Expression (B′): deriving Expression (C) below because when the first analyzer and the second analyzer are the same in configuration, RF.sub.CH4[THC-FID] and RF.sub.CH4[NMNEC-FID] are the same:
x.sub.THC[THC-FID]=x.sub.THC[NMNEC-FID]−x.sub.NMNEHC×PF.sub.C3H8[NMNEC-FID]+x.sub.NMNEHC  Expression (C): and deriving Expression (1) above from Expression (C).

16. A gas analysis apparatus comprising a flow path through which sample gas flows; a hydrocarbon selective catalyst that is provided in the flow path to remove a predetermined hydrocarbon component in the sample gas; an analyzer that is provided downstream of the hydrocarbon selective catalyst in the flow path to measure concentration of hydrocarbon components in the sample gas; and a temperature switching mechanism that switches temperature of the hydrocarbon selective catalyst, wherein the temperature switching mechanism heats the hydrocarbon selective catalyst to 200 to 250° C. to make the hydrocarbon selective catalyst serve as a non-methane non-ethane cutter that removes hydrocarbon components other than methane and ethane in the sample gas, and heats the hydrocarbon selective catalyst to 300° C. or more to make the hydrocarbon selective catalyst serve as a non-methane cutter that removes hydrocarbon components other than the methane in the sample gas.

17. A gas analysis method: providing a first analyzer in a first flow path through which sample gas flows, the first analyzer measuring total hydrocarbon concentration in the sample gas; providing a non-methane non-ethane cutter in a second flow path through which the sample gas flows, the non-methane non-ethane cutter removing hydrocarbon components other than methane and ethane in the sample gas; providing a second analyzer downstream of the non-methane non-ethane cutter in the second flow path, the second analyzer measuring total methane ethane concentration of the methane and the ethane in the sample gas; and calculating concentration of the hydrocarbon components other than the methane and the ethane in the sample gas with use of the total hydrocarbon concentration by the first analyzer and the total methane ethane concentration by the second analyzer.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a diagram schematically illustrating the configuration of a gas analysis apparatus in the present embodiment;

(2) FIG. 2 is a graph illustrating the relationships between the temperature of NMNEC and the permeabilities of hydrocarbons in the same embodiment;

(3) FIG. 3 is a diagram schematically illustrating the configuration of a gas analysis apparatus in a variation;

(4) FIG. 4 is a diagram schematically illustrating the configuration of a gas analysis apparatus in a variation; and

(5) FIG. 5 is a diagram schematically illustrating the configuration of a gas analysis apparatus in a variation.

DESCRIPTION OF EMBODIMENTS

(6) In the following, a gas analysis apparatus according to one embodiment of the present invention will be described with reference to the drawings.

(7) <Apparatus Configuration>

(8) The gas analysis apparatus 100 of the present embodiment is one that, for example, analyzes hydrocarbons contained in exhaust gas discharged from an internal combustion engine.

(9) Specifically, as illustrated in FIG. 1, the gas analysis apparatus 100 includes: a first flow path L1 through which exhaust gas as sample gas flows; a first analyzer 2 that is provided in the first flow path L1 to measure total hydrocarbon concentration (THC concentration) in the exhaust gas; a second flow path L2 that is provided separately from the first flow path L1 and through which the exhaust gas flows; a non-methane non-ethane cutter (NMNEC) 3 that is provided in the second flow path L2 to remove hydrocarbon components other than methane and ethane (NMNEHC) in the exhaust gas; and a second analyzer 4 that is provided downstream of the NMNEC 3 in the second flow path L2 to measure the total methane ethane concentration of the methane and the ethane in the exhaust gas.

(10) The first flow path L1 and the second flow path L2 in the present embodiment branch from a predetermined branching point BP in a main flow path ML having an introduction port P1 through which the exhaust gas is introduced.

(11) The first flow path L1 and the second flow path L2 are respectively provided with a first flow rate regulating mechanism 5 and a second flow rate regulating mechanism 6 so as to match response timing between the first analyzer 2 and the second analyzer 4.

(12) The first flow rate regulating mechanism 5 is formed of, for example, a capillary provided on the upstream side of the first analyzer 2 in the first flow path L1, and the second flow rate regulating mechanism 6 is formed of, for example, a capillary provided on the upstream side of the second analyzer 4 in the second flow path L2.

(13) The NMNEC 3 provided in the second flow path L2 is an oxidation catalyst, which can use manganese dioxide or may be another metal serving as an oxidation catalyst. Also, the NMNEC 3 is heated to 200 to 250° C. Specifically, the second flow path L2 is provided with a heating part 7 for heating the NMNEC 3 to that temperature. As illustrated in FIG. 2, by heating to that temperature, the NMNEC 3 can efficiently burn and remove the hydrocarbon components other than the methane and the ethane (in FIG. 2, propane C.sub.3H.sub.8) and allow the methane and the ethane to pass therethrough efficiently (e.g., 80% or more).

(14) Each of the first analyzer 2 and the second analyzer 4 is an FID that detects hydrocarbons in the exhaust gas by a hydrogen flame ionization (FID) method. The FID is supplied with fuel gas (e.g., H.sub.2 or mixed gas of H.sub.2 and He) and burning supporting air. In FIG. 1, reference sign 8 represents a fuel gas supply line for supplying the fuel gas to the first analyzer 2 and the second analyzer 4, and reference sign 9 represents a burning supporting air supply line for supplying the burning supporting air to the first analyzer 2 and the second analyzer 4. In addition, reference sign 10 represents calibration gas supply lines respectively for supplying calibration gas for calibrating the first analyzer 2 and the second analyzer 4. Further, in the gas analysis apparatus 100, the respective analyzers 2 and 4 and the respective flow paths are heated to a predetermined temperature by heating blocks B1 to B3.

(15) Also, the gas analysis apparatus 100 includes a calculation part 11 that calculates the concentration of the NMNEHC in the exhaust gas from the respective concentrations obtained by the first analyzer 2 and the second analyzer 4.

(16) The calculation part 11 is one that calculates the concentration of the hydrocarbon components other than the methane and the ethane in the sample gas using the total hydrocarbon concentration by the first analyzer 2 and the total methane ethane concentration by the second analyzer 4.

(17) Specifically, the calculation part 11 calculates the NMNEHC concentration in accordance with the following expression using the THC concentration x.sub.THC-[THC-FID] by the first analyzer 2, the total methane ethane concentration x.sub.THC[NMNEC-FID] by the second analyzer 4, and specific organic matter penetrability PF.sub.C3H8[NMNEC-FID] that is a ratio at which specific organic matter having a carbon number of 3 or more (in this case, propane C.sub.3H.sub.8) passes through the NMNEC 3.

(18) $\begin{array}{cc}\left[\mathrm{Expression}3\right]& \\ x_{\mathrm{NMNEHC}}=\frac{x_{\mathrm{THC}\left[\mathrm{THC}-\mathrm{FID}\right]}-x_{\mathrm{THC}\left[\mathrm{NMNEC}-\mathrm{FID}\right]}}{1-{\mathrm{PF}}_{C_3{H}_8\left[\mathrm{NMNEC}-\mathrm{FID}\right]}}& \left(1\right)\end{array}$

(19) The derivation of Expression (1) above will be described below.

(20) The THC concentration x.sub.THC-[THC-FID] obtained by the first analyzer 2 is given by the following expression using a methane response factor RF.sub.CH4-[THC-FID] in the first analyzer 2, an ethane response factor RF.sub.C2H6-[THC-FID] in the first analyzer 2, methane concentration x.sub.CH4 in the sample gas, ethane concentration x.sub.C2H6 in the sample gas, and the concentration x.sub.NMNEHC of the hydrocarbon components other than the methane and the ethane in the sample gas.
x.sub.THC[THC-FID]=x.sub.CH4×RF.sub.CH4[THC-FID]+x.sub.C2H6×RF.sub.C2H6[THC-FID]+x.sub.NMNEHC  (2)

(21) Expression (2) above is based on the assumption that the first analyzer 2 (THC-FID) is calibrated using propane C.sub.3H.sub.8 reference gas. Accordingly, RF.sub.CH4[THC-FID] and RF.sub.C2H6[THC-FID] are the methane and ethane response factors of the first analyzer 2 subjected to the propane calibration. In addition, a response factor is a sensitivity difference (ratio) of a target component from calibration gas. Further, the ethane response factor can be considered as 1.0, and therefore Expression (2) can be considered as the following expression.
x.sub.THC[THC-FID]=x.sub.CH4×RF.sub.CH4[THC-FID]+x.sub.C2H6+x.sub.NMNEHC  (3)

(22) For the concentration obtained by the second analyzer 4 (NMNEC-FID), a concentration arithmetic expression is different depending on a calibration method.

(23) (A) Case of Calibration with Propane Used and Bypassing NMNEC
x.sub.THC[NMNEC-FID]=x.sub.CH4×RF.sub.CH4[NMNEC-FID]×PF.sub.CH4[NMNEC-FID]+x.sub.C2H6×RF.sub.C2H6[NMNEC-FID]×PF.sub.C2H6[NMNEC-FID]+x.sub.NMNEHC×PF.sub.C3H8[NMNEC-FID]  (4)
(B) Case of Calibration with Methane Used and Passed Through NMNEC
x.sub.THC[NMNEC-FID]=x.sub.CH4×x.sub.C2H6×RF.sub.C2H6[NMNEC-FID]×PF.sub.C2H6[NMNEC-FID]+x.sub.NMNEHC×RF.sub.C3H8[NMNEC-FID]×PF.sub.C3H8[NMNEC-FID]  (5)
(C) Case of Calibration with Methane Used and Bypassing NMNEC
x.sub.THC[NMNEC-FID]=x.sub.CH4×PF.sub.CH4[NMNEC-FID]+x.sub.C2H6×RF.sub.C2H6[NMNEC-FID]×PF.sub.C2H6[NMNEC-FID]+x.sub.NMNEHC×RF.sub.C3H8[NMNEC-FID]×PF.sub.C3H8[NMNEC-FID]  (6)
(D) Case of Calibration with Ethane Used and Passing Through NMNEC
x.sub.THC[NMNEC-FID]=x.sub.CH4×RF.sub.CH4[NMNEC-FID]×PF.sub.CH4[NMNEC-FID]+x.sub.C2H6+x.sub.NMNEHC×RF.sub.C3H8[NMNEC-FID]×PF.sub.C3H8[NMNEC-FID]  (7)
(E) Case of Calibration with Ethane Used and Bypassing NMNEC
x.sub.THC[NMNEC-FID]=x.sub.CH4×RF.sub.CH4[NMNEC-FID]×PF.sub.CH4[NMNEC-FID]+x.sub.C2H6×PF.sub.C2H6[NMNEC-FID]+x.sub.NMNEHC×RF.sub.C3H8[NMNEC-FID]×PF.sub.C3H8[NMNEC-FID]  (8)

(24) x.sub.THC[NMNEC-FID]: Measured value of NMNEC-FID

(25) RF.sub.CH4[NMNEC-FID]: Methane response factor in NMNEC-FID

(26) PF.sub.CH4[NMNEC-FID]: Methane penetrability in NMNEC-FID

(27) RF.sub.C2H6[NMNEC-FID]: Ethane response factor in NMNEC-FID

(28) PF.sub.C2H6[NMNEC-FID]: Ethane penetrability in NMNEC-FID

(29) RF.sub.C3H8[NMNEC-FID]: Propane response factor in NMNEC-FID

(30) PF.sub.C3H8[NMNEC-FID]: Propane penetrability in NMNEC-FID

(31) In Expressions (2) to (8) above, since the methane concentration and the ethane concentration cannot be measured, they have to be eliminated in order to simplify the concentration arithmetic expressions. Therefore, when focusing on Expressions (3) and (7), if PF.sub.CH4[NMNEC-FID] and RF.sub.C3H8[THC-FID] can be removed, these two expressions can be combined. In addition, in the case of using Expression (4), (5), (6), or (8), the methane concentration and the ethane concentration cannot be eliminated, and therefore the NMNEHC concentration cannot be calculated.

(32) Further, since the NMNEC 3 is heated to 200 to 250° C., PF.sub.CH4[THC-FID] can be assumed to be approximately 1.0, and therefore removed from Expression (7).

(33) Also, the propane response factor of the second analyzer 4 subjected to the ethane calibration can be considered as 1.0, and therefore removed from Expression (7).

(34) As a result, the following expression can be obtained.
x.sub.THC[NMNEC-FID]=x.sub.CH4×RF.sub.CH4[NMNEC-FID]+x.sub.C2H6+x.sub.NMNEHC×PF.sub.C3H8[NMNEC-FID]  (9)

(35) In addition, since the first analyzer 2 and the second analyzer 4 are the same in configuration, RF.sub.CH4[THC-FID] and RF.sub.CH4[THC-FID] can be considered as the same.

(36) Accordingly, from Expressions (3) and (9), the following expression can be obtained.
x.sub.THC[THC-FID]=x.sub.THC[NMNEC-FID]−x.sub.NMNEHC×PF.sub.C3H8[NMNEC-FID]+x.sub.NMNEHC  (10)

(37) By rewriting Expression (10) above in terms of x.sub.NMNEHC, Expression (1) above can be derived. As described above, to derive Expression (1), the penetrability PF and response factor RF of each hydrocarbon component are taken into account.

(38) From Expression (1) above, it turns out that by examining only PF.sub.C3H8[THC-FID], the NMNEHC concentration can be obtained from the concentration x.sub.THC[THC-FID] obtained by the first analyzer 2 (THC-FID) and the concentration x.sub.THC[NMNEC-FID] obtained by the second analyzer 4 (NMNEC-FID).

(39) <Effects of the Present Embodiment>

(40) Since the gas analysis apparatus 100 of the present embodiment can continuously measure the total methane ethane concentration of the methane and the ethane in the sample gas by the second analyzer 4 using the NMNEC 3 that removes the hydrocarbon components other than the methane and the ethane, the concentration of the hydrocarbon components other than the methane and the ethane in the sample gas can be calculated in combination with the THC concentration continuously measured by the first analyzer 2. As a result, the concentration of the hydrocarbon components other than the methane and the ethane (NMNEHC) in the sample gas can be continuously measured.

(41) <Variations>

(42) Note that the present invention is not limited to the above-described embodiment.

(43) As illustrated in FIG. 3, the gas analysis apparatus 100 may further include: a third flow path L3 through which the sample gas flows and that is provided with a non-methane cutter (NMC) 12 for removing hydrocarbon components other than the methane in the sample gas; and a third analyzer 13 that is provided in the third flow path L3 to measure the methane concentration in the sample gas. In this case, the third flow path L3 is provided with a heating part 14 that increases the temperature of the NMC 12 to 300° C. or more.

(44) In addition, the calculation part 11 can calculate the concentration of the hydrocarbon components other than the methane in the sample gas using the total hydrocarbon concentration by the first analyzer 2 and the methane concentration by the third analyzer 13. Further, the calculation part 11 can also calculate the ethane concentration in the sample gas using the total methane ethane concentration by the second analyzer 4 and the methane concentration by the third analyzer 13.

(45) Still further, the third flow path L3 is provided with a third flow rate regulating mechanism 15 in order to match response timing among the first analyzer 2, the second analyzer 4, and the third analyzer 13. The third flow rate regulating mechanism 15 is formed of, for example, a capillary provided on the upstream side of the third analyzer 13 in the third flow path L3.

(46) In addition, as illustrated in FIG. 4, the gas analysis apparatus 100 may be adapted to merge the downstream side of the NMC 12 in the third flow path L3 and the downstream side of the NMNEC 3 in the second flow path L2 and introduce the sample gas to the analyzer 4 in common. In this case, a flow path switching mechanism 16 that consists of, for example, on-off valves V1 and V2, and between the second flow path L2 and the third flow path L3, switches a flow path through which the sample gas flows is provided. Switching to the second flow path L2 allows the analyzer 4 to measure the total methane ethane concentration, and switching to the third flow path L3 allows the analyzer 4 to measure the methane concentration. This configuration makes it possible to reduce the number of analyzers, thus enabling cost reduction and the like of the gas analysis apparatus.

(47) Without limitation to the configuration of the gas analysis apparatus of the above-described embodiment, the gas analysis apparatus of the present invention only has to include: a first flow path through which sample gas flows; a first analyzer that is provided in the first flow path to measure total hydrocarbon concentration in the sample gas; a second flow path through which the sample gas flows; a non-methane non-ethane cutter that is provided in the second flow path to remove hydrocarbon components other than methane and ethane in the sample gas; a second analyzer that is provided downstream of the non-methane non-ethane cutter in the second flow path to measure the total methane ethane concentration of the methane and the ethane in the sample gas; and a calculation part that calculates the concentration the hydrocarbon components other than the methane and the ethane in the sample gas with use of the total hydrocarbon concentration by the first analyzer and the total methane ethane concentration by the second analyzer.

(48) In addition, as illustrated in FIG. 5, the gas analysis apparatus 100 may include: a first flow path L1 through which exhaust gas as sample gas flows; a first analyzer 2 that is provided in the first flow path L1 to measure total hydrocarbon concentration (THC concentration) in the exhaust gas; a second flow path L2 that is provided separately from the first flow path L and through which the exhaust gas flows; a hydrocarbon selective catalyst 17 that is provided in the second flow path L2 to remove a predetermined hydrocarbon component in the exhaust gas; an analyzer 18 that is provided downstream of the hydrocarbon selective catalyst 17 in the second flow path L2 to measure the concentration of hydrocarbon components in the exhaust gas; and a temperature switching mechanism 19 that switches the temperature of the hydrocarbon selective catalyst 17. The analyzer 18 is an FID that detects the hydrocarbons in the exhaust gas by a hydrogen flame ionization (FID) method. The hydrocarbon selective catalyst 17 is a catalyst capable of, depending on a temperature, selecting a hydrocarbon component to be removed, and serves as, for example, a non-methane cutter or a non-methane non-ethane cutter depending on a temperature. In addition, the hydrocarbon selective catalyst 17 may be one that not only selectively removes methane, or methane and ethane, but can selectively remove another hydrocarbon. The temperature switching mechanism 19 is configured to include a heating part whose set temperature is changeable as in the above-described embodiment.

(49) Further, the temperature switching mechanism 19 heats the hydrocarbon selective catalyst 17 to 200 to 250° C. to make the hydrocarbon selective catalyst 17 serve as a non-methane non-ethane cutter that removes hydrocarbon components other than methane and ethane in the exhaust gas. In doing so, the analyzer 18 measures the total methane ethane concentration of the methane and the ethane in the exhaust gas. In this case, a calculation part of the gas analysis apparatus 100 calculates the concentration of the hydrocarbon components other than the methane and the ethane in the exhaust gas from the THC concentration by the first analyzer 2 and the total methane ethane concentration by the analyzer 18.

(50) Also, the temperature switching mechanism 19 heats the hydrocarbon selective catalyst 17 to 300° C. or more to make the hydrocarbon selective catalyst 17 serve as a non-methane cutter that removes hydrocarbon components other than the methane in the exhaust gas. In doing so, the analyzer 18 measures the concentration of the methane in the exhaust gas. In this case, the calculation part of the gas analysis apparatus 100 calculates the concentration of the hydrocarbon components other than the methane in the exhaust gas from the THC concentration by the first analyzer 2 and the methane concentration by the analyzer 18.

(51) In addition, the temperature switching by the temperature switching mechanism 19 may be configured to be manually settable by a user or be automatically settable by, for example, a predetermined measurement sequence or the like. Further, in the above description, the analyzers 2, 4, and 18 are the FIDs; however, any analyzer can be used as long as the analyzer can measure hydrocarbon components.

(52) Besides, various modifications and combinations of the embodiment and the variations may be made without departing from the scope of the present invention.

REFERENCE SIGNS LIST

(53) 100: Gas analysis apparatus L1: First flow path 2: First analyzer L2: Second flow path 3: Non-methane non-ethane cutter (NMNEC) 4: Second analyzer 5: First flow rate regulating mechanism 6: Second flow rate regulating mechanism 7: Heating part 11: Calculation part L3: Third flow path 12: Non-methane cutter (NMC) 13: Third analyzer 14: Heating part 15: Third flow rate regulating mechanism 17: Hydrocarbon selective catalyst 18: Analyzer 19: Temperature switching mechanism