Gas analyser system

A method for measuring a gaseous medium in a gas analyser system, wherein the gas analyser system comprises:

• a supply channel having an inlet supply opening at a first end of the supply channel near a gaseous environment containing the gaseous medium, and an outlet supply opening at a second end of the supply channel;
• a measuring channel, comprising a first end and a second end, wherein the measuring channel is connected to the supply channel between the first end and the second end of the supply channel, and wherein the measuring channel is connected across the supply channel in at least a four-way intersection, providing at least three pathways for the gaseous medium transported through the supply channel from the first end of the supply channel;
• a pressure system, wherein the pressure system is arranged to provide a pressure difference between a first pressure near the inlet supply opening and a second pressure near the outlet supply opening, wherein the first pressure is larger than the second pressure;
• an analysing unit, comprising an optical arrangement for analysing the gaseous medium contained in the measuring channel, wherein the optical arrangement comprises a first optical unit arranged at the first end of the measuring channel and a second optical unit arranged at the second end of the measuring channel, and wherein an optical measurement path is defined between the first optical unit and the second optical unit;
• and
• a barrier arrangement arranged near each end of the measuring channel, each barrier arrangement comprising:
• a gas source for providing a barrier gas;
• and
• a barrier gas inlet and a barrier gas outlet arranged in opposing manner across the measuring channel, the barrier gas inlet is in connection with the gas source and provided with a nozzle having a nozzle opening being directed towards the opposing barrier gas outlet having a barrier gas outlet opening,
• wherein the barrier arrangement is arranged to provide pressurized gas creating a barrier gas curtain between the barrier gas inlet and the barrier gas outlet hereby providing an area of low pressure so as to force at least a part of the gaseous medium from the supply channel into the measuring channel and entrained by the barrier gas curtain and discharged with the barrier gas curtain through the barrier gas outlet and so as to separate the gaseous medium from the first and second optical units, such that the optical measurement path passes through the barrier gas curtain, and
• wherein the barrier arrangement comprises a curtain controller for controlling a flow rate of the barrier gas curtain,
• wherein the method comprises steps of:
• providing a pressure difference between a first pressure of the gaseous medium near the inlet supply opening and a second pressure of the gaseous medium near the outlet supply opening, so as to force the gaseous medium from the supply inlet opening toward the supply outlet opening;
• providing a flow of the barrier gas through the nozzle opening toward the barrier gas outlet opening, so as to provide a barrier gas curtain and so as to force at least a part of the gaseous medium from the supply channel into the measuring channel towards the barrier gas curtain;
• controlling the flow rate of the barrier gas curtain, and thereby controlling an amount of the gaseous medium forced towards the barrier gas curtain;
• and
• measuring the gaseous medium in the measuring channel using the optical arrangement.