Monitoring Flare Stack Pilot Burners

Abstract

A flare stack comprises an upwardly extending gas discharge duct 10 and a pilot burner 16 operative at an burner location near the open top end of the duct 10 to ignite gas discharged by way of the duct. Atmospheric samples from the burner location are delivered to a monitoring station 20 remote from the duct 10 and at ground level 12 . A sensor at the monitoring station 20 is responsive to a parameter of the sample indicative of combustion at the burner location such as increased CO 2 or NO x or decreased O 2 . An igniter is operatively associated with the sensor and arranged to light the pilot burner 16 automatically if the sensor does not detect said parameter in the sample.

1 . A flare stack comprising a gas discharge duct and a pilot burner operative at a burner location to ignite gas discharged by way of the duct, which flare stack comprises: sampling means operative to sample gases at the burner location and deliver a sample thereof to a monitoring location remote from the burner location, a sensor at the monitoring location responsive to a parameter of the sample indicative of combustion at the burner location; and a signalling device operatively associated with the sensor and arranged to provide a signal automatically if the sensor does not detect said parameter in said sample. 
     
     
         2 . A flare stack as claimed in  claim 1  wherein said flare stack comprises an igniter activated automatically in response to said signal to relight the pilot burner. 
     
     
         3 . A flare stack as claimed in  claim 2  wherein said flare stack comprises at the burner location a flame sensor operatively associated with the pilot burner and arranged to ignite the pilot burner automatically if the flame sensor does not detect a flame. 
     
     
         4 . A flare stack as claimed in  claim 1  wherein said parameter is the proportion of a selected constituent of the sample and said signal is provided automatically if the sensor detects that said proportion differs from a predetermined reference value therefor. 
     
     
         5 . A flare stack as claimed in  claim 4  wherein the reference value is an average from measurement of said proportion over time and said signal is provided automatically if the sensor detects a change from the average. 
     
     
         6 . A flare stack as claimed in  claim 4  wherein the reference value is a predicted value for said proportion. 
     
     
         7 . A flare stack as claimed in  claim 6  wherein the reference value is the predicted proportion of oxygen and/or carbon monoxide and/or carbon dioxide and/or oxides of nitrogen in the sample. 
     
     
         8 . A flare stack as claimed in  claim 1  wherein the sensor comprises an electrochemical cell or a non-dispersive infrared (NDIR) sensor ( 30 ). 
     
     
         9 . A flare stack as claimed in  claim 1  wherein the sampling means comprises a conduit extending from the burner location to the monitoring location and an aspirator operative to draw the sample through the conduit from the burner location to the monitoring location. 
     
     
         10 . A flare stack as claimed in  claim 9  wherein the aspirator operates substantially continuously. 
     
     
         11 . A flare stack as claimed in  claim 9  wherein the aspirator operates periodically. 
     
     
         12 . A flare stack as claimed in  claim 1  wherein said flare stack includes a display at the monitoring location, which display is operatively associated with the or each sensor and arranged to indicate the status of the pilot burner. 
     
     
         13 . A method of disposing of unwanted gas released from oil or gas production facilities, wherein the unwanted gas is discharged by way of a duct and ignited by a pilot burner at a burner location, which method comprises: sampling gases at the burner location, delivering the sample to a monitoring location remote from the burner location; testing the sample at the monitoring location to detect a parameter indicative of combustion at the burner location; and providing a signal automatically if said parameter is not detected in the sample. 
     
     
         14 . A method of disposing of unwanted gases as claimed in  claim 13  comprising reigniting the pilot burner automatically in response to said signal. 
     
     
         15 . A method of disposing of unwanted gases as claimed in  claim 13  wherein said parameter is the proportion of oxygen and/or carbon monoxide and/or carbon dioxide and/or oxides of nitrogen in the sample and the test measures such proportion against a predetermined reference value for the parameter. 
     
     
         17 . A method of disposing of unwanted gases as claimed in  claim 15  wherein the reference value is a time-averaged empirical value for the sample. 
     
     
         18 . A method of disposing of unwanted gases as claimed in  claim 15  wherein the reference value is a predicted value for the sample.