Detecting Flame Instability and/or Loss of Flame in Fired Heaters Using Advanced Pressure Diagnostics

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Title Detecting Flame Instability and/or Loss of Flame in Fired Heaters Using Advanced Pressure Diagnostics
Creator Stier, Randy S.
Contributor Miller, John P.
Date 2013-09-25
Spatial Coverage Kauai, Hawaii
Subject AFRC 2013 Industrial Combustion Symposium
Description Paper from the AFRC 2013 conference titled Detecting Flame Instability and/or Loss of Flame in Fired Heaters Using Advanced Pressure Diagnostics by Randy Stier
Abstract Maintaining stable combustion is critical to the safe operation of fired heaters. When the ratio of air flow to fuel flow to a burner transitions from a point inside the burner's operating envelope to a point outside the burner's operating envelope, the combustion process becomes unstable and then stops. If this loss of flame is not recognized and acted upon properly, an explosion may occur. One possible way to detect loss of flame may be to monitor pulsations in the difference between the flue gas pressure inside a fired heater and atmospheric pressure at a given elevation (commonly referred to as "draft"). During stable combustion, the draft will pulsate slightly (see Figure 1). This is commonly referred to as combustion rumble. As a burner's air/fuel ratio transitions from inside to outside the burner's operating envelope, the draft pulsations may exhibit a sharp increase in amplitude and frequency, caused by instability in the burner flames. Flame instability is often a precursor to flame out. Draft transmitters with Advanced Diagnostics Statistical Process Monitoring (SPM) capability monitor the pulsations in the draft measurement and detect the increase in amplitude or frequency associated with flame instability. SPM data may be integrated with heater operations. An alarm limit on the SPM standard deviation may be configured to alert a heater operator to potential combustion problems or flame out. Valero has worked with Rosemount to evaluate the use of SPM technology for detection of flame instability or flame out. Recent testing was performed on five different burners at three different burner vendors. The technology was also evaluated on a heater at the Valero Texas City Refinery. Experience gained from these tests may be used to determine where to set the alarm limit for detecting flame instability. There is a correlation between the volumetric firing rate of a burner/heater system and the draft standard deviation. This correlation can be exploited for selecting an appropriate alarm limit in an operating fired heater. Burner vendor tests indicate that a draft standard deviation alarm limit of 30 thousandths inches of water column (m-inWC) may be appropriate. Additional work is required to validate these observations but initial results indicate the use of advanced pressure diagnostics may be an effective way to detect loss of flame.
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ARK ark:/87278/s68p8xp2
Setname uu_afrc
Date Created 2014-10-14
Date Modified 2014-10-14
ID 14388
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