Method for Adapting the Concentration of a Sample Gas in a Gas Mixture to be Analysed by a Gas Chromatograph Assembly, and Chromatograph Assembly Therefore

Abstract

Method for adapting the concentration of a sample gas in a gas mixture to be analysed by a gas chromatograph assembly, the assembly comprising a sample gas inlet, a secondary gas inlet, a gas chromatograph sensor, a gas chromatograph column, and a gas chromatograph bypass parallel to the column, characterized by a) introducing sample gas through the sample gas inlet, b) introducing secondary gas through the secondary gas inlet, c) mixing the sample gas and the secondary gas to a gas mixture and conducting the mixture via the bypass, d) circulating the mixture in a gas conducting loop comprising the bypass and the sensor, e) repeating steps b), c) and d) without step a) to gradually reduce the concentration of sample gas within the mixture until the concentration reaches a desired predetermined level, f) analysing the mixture by means of gas chromatography employing the column and the sensor.

Claims

1. A method for adapting a concentration of a sample gas in a gas mixture to be analysed by a gas chromatograph assembly, the gas chromatograph assembly comprising a sample gas inlet for introducing a sample gas to be analysed, a secondary gas inlet, a gas chromatograph sensor, a gas chromatograph column, and a gas chromatograph bypass parallel to the column, wherein the method comprises a) introducing an amount of sample gas through the sample gas inlet, b) introducing an amount of secondary gas through the secondary gas inlet, c) mixing the sample gas and the secondary gas to a gas mixture and conducting the gas mixture via the gas chromatograph bypass, d) circulating the gas mixture in a gas conducting loop comprising the gas chromatograph bypass and the gas chromatograph sensor, e) repeating steps b), c) and d) without step a) to gradually reduce the concentration of sample gas within the gas mixture until the concentration of sample gas within the gas mixture reaches a desired predetermined level, f) analysing the gas mixture thus obtained by means of gas chromatography employing the gas chromatograph column and the gas chromatograph sensor.

2. The method according to claim 1, wherein the sample gas concentration is measured during or before step d) to determine whether the sample gas concentration has reached the predetermined level.

3. The method according to claim 2, wherein the measuring of the sample gas concentration during or before step d) is performed with a secondary sensor assembly.

4. The method according to claim 3, wherein during step a) the sample gas from the sample gas inlet is conducted through the secondary sensor assembly and to the gas chromatograph sensor.

5. The method according to claim 3, wherein the gas conducting loop further comprises the secondary sensor assembly.

6. The method according to claim 1, wherein the repeating according to step d) is performed a predetermined number of times without measuring the sample gas concentration.

7. The method according to claim 1, wherein the gas conducting loop comprises a gas modulation valve adapted to alternatingly connect either of the sample gas inlet and the secondary gas inlet with the gas conducting loop.

8. The method according to claim 7, wherein during step a) the gas modulation valve connects the sample gas inlet with the gas conducting loop while separating the secondary inlet from the gas conducting loop.

9. The method according to claim 7, wherein during step b) the gas modulation valve connects the secondary gas inlet with the gas conducting loop while separating the sample gas inlet from the gas conducting loop.

10. The method according to claim 1, wherein during step c) both the sample gas inlet and the secondary inlet are separated from the gas conducting loop.

11. A gas chromatograph assembly for adapting a concentration of a sample gas in a gas mixture to be analysed according to the method of claim 1, comprising a sample gas inlet for introducing a sample gas to be analysed, a secondary gas inlet, a gas chromatograph sensor, a gas chromatograph column, and a gas chromatograph bypass arranged parallel to the gas chromatograph column for bypassing the same, and a gas conducting loop comprising the gas chromatograph bypass and the gas chromatograph sensor.

12. The gas chromatograph assembly of claim 11, further comprising a secondary sensor assembly for measuring the sample gas concentration during or before step d).

13. The gas chromatograph assembly of claim 11, wherein the gas conducting loop comprises a gas modulation valve adapted to alternatingly connect either of the sample gas inlet and the secondary gas inlet with the gas conducting loop.

14. The method according to claim 1, wherein the gas conducting loop comprises a gas chromatograph valve adapted to switch between the gas chromatograph column and the gas chromatograph bypass to conduct gas either through the gas chromatograph column or the gas chromatograph bypass into the gas chromatograph sensor.

15. The gas chromatograph assembly according claim 11, wherein the gas conducting loop comprises a gas chromatograph valve adapted to switch between the gas chromatograph column and the gas chromatograph bypass to conduct gas either through the gas chromatograph column or the gas chromatograph bypass into the gas chromatograph sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In the following, exemplary embodiments of the invention will be explained with reference to the figures. In particular,

[0031] FIG. 1 shows the general layout of a first embodiment and

[0032] FIG. 2 shows a general layout of a second embodiment.

DESCRIPTION OF THE INVENTION

[0033] FIGS. 1 and 2 show a gas chromatograph assembly 10 comprising a sample gas inlet 20 for introducing a sample gas to be analysed, a secondary gas inlet 40, being a reference gas inlet which is open to atmosphere. The gas chromatograph assembly 10 further comprises a gas chromatograph sensor 24, a gas chromatograph column 26, and a gas chromatograph bypass 28 parallel to the column 26.

[0034] A gas chromatograph valve 30 is provided, being adapted to switch between the gas chromatograph column 26 and the gas chromatograph bypass 28 to conduct gas either through the gas chromatograph column 26 or the gas chromatograph bypass 28 into the gas chromatograph sensor 24.

[0035] A secondary sensor assembly 12 in the form of an infrared sensor assembly is provided for measurement of the sample gas concentration. The secondary sensor assembly 12 comprises a secondary sensor assembly inlet 16 at a first end, and a secondary sensor assembly outlet 18 at a second end of the secondary sensor assembly 12.

[0036] The sample gas inlet 20 and the secondary gas inlet 40 are connected in parallel to a gas modulation valve 42, which is adapted to alternatingly connect either of the sample gas inlet 20 and the secondary gas inlet 40 to the secondary sensor assembly 12. The sample gas inlet 20 is connected to the gas modulation valve 42 via a check valve 50.

[0037] The gas chromatograph sensor 24 is connected to an exhaust outlet 22 via an exhaust line 32. The exhaust line 32 is connected to the gas flow path connecting the sample gas inlet 20 and the gas modulation valve 42, thereby forming a loop 52. In particular, the loop 52 comprises the gas modulation valve 42, the secondary gas sensor assembly 12, the gas chromatograph valve 30, an additional gas pump 54 in the gas flow path connecting the secondary sensor assembly 12 and the gas chromatograph sensor 24, the bypass 28, the gas chromatograph sensor 24 and the exhaust line 32. Alternatively, the exhaust line 32 and the loop 52 may be connected to respective separate outlets of the sensor 24.

[0038] The loop 52 is adapted to circulate the gas mixture of the sample gas and of the secondary gas a number of times before measuring the sample gas concentration with the secondary gas sensor assembly 12. Once the sample gas concentration is sufficiently reduced, the gas chromatograph valve 30 switches from the gas chromatograph bypass to the gas chromatograph column 26 for a predetermined amount of time in order to inject a short gas pulse of the gas mixture into the column 26.

[0039] In both embodiments, the gas chromatograph valve 30 switches between the column 26 and the bypass 28. In the embodiment of FIG. 1, the gas chromatograph valve 30, the column 26 and the bypass 28 are comprised in the gas flow path connecting the secondary sensor outlet 18 with the gas chromatograph sensor 24. This gas flow path also comprises the additional gas pump 54. In the embodiment according to FIG. 2, the gas chromatograph valve 30, the column 26 and the bypass 28 are comprised in the gas flow path connecting the gas modulation valve 42 and the secondary sensor assembly inlet 16.