US-12625116-B2 - Gas monitoring device for gas chromatograph

US12625116B2US 12625116 B2US12625116 B2US 12625116B2US-12625116-B2

Abstract

A gas monitoring device for gas chromatograph comprises a pump to remove gas in a column oven of the gas chromatograph, a flow rate detection unit including a self-heating element arranged in a measurement flow path, a temperature acquisition unit configured to acquire temperature information about the gas flowing into the measurement flow path, and a controller configured to set the reference temperature of the self-heating element of the flow rate detection unit to a temperature of the gas flowing into the measurement flow path based on the temperature information acquired by the temperature acquisition unit and determine normality of the operation of the pump based on the signal acquired by the flow rate detection unit.

Inventors

Yuki Komori
Shori KINOSHITA
Nami HONGO

Assignees

SHIMADZU CORPORATION

Dates

Publication Date: 20260512
Application Date: 20240209
Priority Date: 20230323

Claims (10)

1 . A gas monitoring device for gas chromatograph, comprising: a pump configured to draw out a gas from a space in a column oven of the gas chromatograph; a measurement flow path through which the gas drawn out of the space in the column oven by the pump flows; a gas sensor having a sensing unit exposed to an inside of the measurement flow path, the gas sensor being configured to detect a specific component in the gas flowing through the measurement flow path; a flow rate detection unit including a self-heating element arranged in the measurement flow path, the flow rate detection unit being configured to acquire a signal corresponding to a flow rate of the gas flowing through the measurement flow path by controlling a voltage applied to the self-heating element so that a temperature of the self-heating element is kept constant at a reference temperature; a temperature acquisition unit configured to acquire temperature information about the gas flowing into the measurement flow path; and a controller configured to control operations of the pump and the flow rate detection unit, wherein the controller is configured to set the reference temperature of the self-heating element of the flow rate detection unit to a temperature of the gas flowing into the measurement flow path based on the temperature information acquired by the temperature acquisition unit and determine normality of the operation of the pump based on the signal acquired by the flow rate detection unit, the gas monitoring device for gas chromatograph further comprising: a correlation data holding unit configured to hold correlation data indicating a correlation between the temperature of the gas flowing into the measurement flow path and a temperature to be set as the reference temperature of the self-heating element, and wherein the reference temperature is configured to be determined using the temperature information acquired by the temperature acquisition unit and the correlation data held in the correlation data holding unit.
2 . The gas monitoring device for gas chromatograph, as recited in claim 1 , wherein the correlation data holding unit holds correlation data between the flow rate of the gas flowing through the measurement flow path and the signal under a plurality of temperature conditions that are a combination of the reference temperature of the self-heating element and the temperature of the gas flowing into the measurement flow path, and wherein the controller is configured to acquire the flow rate of the gas flowing through the measurement flow path from the signal acquired by the flow rate detection unit, using the correlation data held in the correlation data holding portion, and determine the normality of the operation of the pump by whether the flow rate of the gas flowing through the measurement flow path is equal to or less than a predetermined flow rate.
3 . The gas monitoring device for gas chromatograph, as recited in claim 1 , wherein the temperature acquisition unit includes a temperature sensor disposed in the measurement flow path separately from the self-heating element of the flow rate detection unit.
4 . The gas monitoring device for gas chromatograph, as recited in claim 3 , wherein the temperature sensor of the temperature acquisition unit is placed at a position downstream of the self-heating element of the flow rate detection unit.
5 . The gas monitoring device for gas chromatograph, as recited in claim 1 , wherein the temperature acquisition unit is configured to acquire a set temperature of the column oven as temperature information about the temperature of the gas flowing into the measurement path.
6 . The gas monitoring device for gas chromatograph, as recited in claim 1 , further comprising: an inlet flow path for introducing the gas into the measurement flow path, wherein the inlet flow path is provided to introduce the gas into the measurement flow path from a direction perpendicular to a flow path direction of the measurement flow path, and wherein the self-heating element has a longitudinal direction, the longitudinal direction being within a plane parallel to the flow path direction, and is placed at a position where the gas flows into the measurement flow path from the inlet flow path so that the gas flowing into the measurement flow path is introduced onto the self-heating element from a direction perpendicular to the longitudinal direction.
7 . The gas monitoring device for gas chromatograph as recited in claim 6 , wherein a cross-sectional area of a flow path cross-section of the inlet flow path is smaller than a cross-sectional area of a flow path cross-section of a flow path upstream of the inlet flow path and that downstream of the inlet flow path.
8 . The gas monitoring device for gas chromatograph, as recited in claim 1 , wherein the measurement flow path is formed in a block, wherein the block has a through-hole that leads to the measurement flow path, and wherein the self-heating element of the flow rate detection unit is held by a holding board fixed to an outer surface of the block, the outer surface having the through-hole, and is inserted into the through-hole in a state in which the self-heating element is kept at a predetermined distance from the holding board.
9 . The gas monitoring device for gas chromatograph, as recited in claim 8 , wherein a septum with insulating and elastic properties is interposed between the self-heating element of the flow rate detection unit and the holding board, and wherein lead wires drawn from the self-heating element of the flow rate detection unit are covered by the septum, and the through-hole is sealed by the septum fitted into the through-hole of the block.
10 . The gas monitoring device for gas chromatograph as recited in claim 1 , wherein the specific component is hydrogen.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2023-046412 filed on Mar. 23, 2023, the entire disclosure of which is incorporated herein by reference in its entirety. BACKGROUND OF THE INVENTION Field of the Invention The present disclosure relates to a gas monitoring device for monitoring a gas leakage in a gas chromatograph (in this disclosure, also simply referred to as “GC”). Description of the Related Art The following description sets forth the inventor's knowledge of the related art and problems therein and should not be construed as an admission of knowledge in the prior art. In a GC, a gas flows through a pipe such as a column. In a case where the column is damaged or a pipe connection seal is inadequate, a gas leakage will occur, causing various problems. In particular, in a case where a flammable gas, such as a hydrogen gas, is used as a carrier gas in a GC, there is a risk of explosion or other hazards if the column oven is used in a state in which a flammable gas is leaking in the column oven. Therefore, it has been proposed to monitor a flammable gas leakage in a column oven by using a gas detector that detects a gas, such as a hydrogen gas (see Patent Document 1). The gas detector detects the concentration of the flammable gas in the air taken in by sucking the air in the column oven by means of a pump. With such a gas detector, when the concentration of the flammable gas in the sucked air exceeds a predetermined concentration, an error message is displayed on a display or other means, or the heating of the column oven and the supply of a carrier gas are suspended. This prevents occurrence of accidents. By the way, in the event that the pump of the gas detector malfunctions and fails to draw in the gas in the column oven normally, the gas detector will not detect any flammable gas despite the fact that there is a leakage of a flammable gas into the column oven. For this reason, it has also been proposed to monitor whether the pump is operating properly by detecting a flow rate of a gas which is being drawn into a gas detector. PRIOR ART DOCUMENTS Patent Documents Patent Document 1: Japanese Unexamined Patent Application Publication No. 2008-129013 As a mechanism for detecting the flow rate of a gas to be taken into a gas detector, a mechanism using a self-heating element can be exemplified. The detection of a gas flow rate using a self-heating element is performed by acquiring a signal corresponding to a heat quantity deprived from the gas by the self-heating element. In a GC, however, in some cases, an analysis is performed while changing the temperature in the column oven over a wide range. In such a case, if the temperature of the self-heating element is maintained constant during the analysis, the gas flow rate may not be accurately detected. SUMMARY OF THE INVENTION The present disclosure has been made to solve the above problems. The purpose of the present disclosure is to provide a gas monitoring device for gas chromatograph capable of accurately detecting a flow rate of a gas to be drawn in from a column oven and accurately determining the normality of a pump's operation even in an environment in which the temperature in the column oven varies greatly. A gas monitoring device for gas chromatograph, includes: a pump configured to draw out a gas from a space in a column oven of the gas chromatograph; a measurement flow path through which the gas drawn out of the space in the column oven by the pump flows;a gas sensor having a sensing unit exposed to an inside of the measurement flow path, the gas sensor being configured to detect a specific component in the gas flowing through the measurement flow path;a flow rate detection unit including a self-heating element arranged in the measurement flow path, the flow rate detection unit being configured to acquire a signal corresponding to a flow rate of the gas flowing through the measurement flow path by controlling a voltage applied to the self-heating element so that a temperature of the self-heating element is kept constant at a reference temperature;a temperature acquisition unit configured to acquire temperature information about the gas flowing into the measurement flow path; anda controller configured to control operations of the pump and the flow rate detection unit,wherein the controller is configured to set the reference temperature of the self-heating element of the flow rate detection unit to a temperature of the gas flowing into the measurement flow path based on the temperature information acquired by the temperature acquisition unit anddetermine normality of the operation of the pump based on the signal acquired by the flow rate detection unit. The gas monitoring device for gas chromatograph according to the present disclosure is provided with a temperature acquisition unit configured to acquire temperature information about a gas