62 MARCH 2016 | HydrocarbonProcessing.com
Heat Transfer
from affecting the operation of electronics in or near the heat- er, such as the ignition and flame monitoring instrumentation. Another way to purge using steam is with a steam edu- cator (FIG. 10). Steam is injected into the stack above the
damper. As the steam rises, it draws air into the bottom of the heater and pushes it up through the heater, expelling any combustible gases.
Mandatory purging with a burner management sys- tem. The most important function for the use of a burner management system (BMS) is to prevent the possibility of an accumulation of combustible gas within the heater prior to in- troducing a flame inside the heater.10 The issue becomes how
to “prove” that four to five volume changes have taken place. With a steam purge, or a purge using a steam educator, this is possible. If it is proven with the stack damper open, and if the flowrate of the purge steam is known, it can be determined how long it takes to evacuate the air and any combustibles from within the heater. With a natural purge, this is not possible. For facilities that lack available steam, the next resource is to install a purge fan to perform the purge function. With this method and the known flowrate of air, the purge time period can be determined. FIG. 11 shows a typical flow diagram for the man-
datory purge using an automated burner management system.
These simple and commonsense rules for the safe operation of a process heater—keeping the flames in the box and off the tubes, maintaining the process in the tubes, and shutting flam- mables out during lightoff—are not intended to be compre- hensive, but are designed to be easy to remember, particularly for those with less experience in operating process heaters. Failure to abide by these four rules can produce serious con- sequences, including personnel injury and equipment damage. Companies should have their own detailed processes and pro- cedures for operating specific heaters. Heaters must be con- stantly monitored with regular visual inspections both inside and outside of the heater. This will help prevent flames from exiting the heater, along with the leakage of flammable liquids from the process tubes.
LITERATURE CITED
1 ANSI/API Standard 560, “Fired heaters for general refinery service,” Fourth
ed., 2007, American Petroleum Institute, Washington, DC.
2 API Recommended Practice 535, “Burners for fired heaters in general refinery
services,” Third ed., 2014, American Petroleum Institute, Washington, DC.
3 Baukal, C. E., “Safety,” The John Zink Hamworthy Combustion Handbook, Vol. 2:
Design and Operations, CRC Press, Boca Raton, Florida, 2013.
4 Baukal, C. E., I-P Chung, S. Londerville, J. G. Seebold and R. T. Waibel,
“Pollutant Emissions,” The John Zink Hamworthy Combustion Handbook, Vol. 1: Fundamentals, CRC Press, Boca Raton, Florida, 2013.
5 Baukal, C. E. and W. Bussman, “NO
x emissions,” The John Zink Hamworthy
Combustion Handbook, Vol. 1: Fundamentals, CRC Press, Boca Raton, Florida,
2013.
6 Baukal, C. E. and W. Bussman, “Thermal Efficiency,” The John Zink Hamworthy
Combustion Handbook, Vol. 1: Fundamentals, CRC Press, Boca Raton, Florida,
2013.
7 Newnham, R., Direct-Fired Heaters: Improving Efficiency and Capacity While
Reducing Emissions, Kingsley Knowledge Publishing, Alberta, Canada, 2013.
8 Waibel, R. T., M. G. Claxton and B. Reese, “Burner design,” The John Zink
Hamworthy Combustion Handbook, Vol. 2: Design and Operations, CRC Press,
Boca Raton, Florida, 2013.
9 Newnham, R., Direct-Fired Heaters: Operator Training Manual, Kingsley
Knowledge Publishing, Alberta, Canada, 2013.
10 Newnham, R., Direct-Fired Heaters: A Practical Guide to Their Design and
Operation, Kingsley Knowledge Publishing, Alberta, Canada, 2012.
11 Johnson, W., E. Platvoet, M. Pappe, M. Claxton and R. Waibel, “Burner
Troubleshooting,” The John Zink Hamworthy Combustion Handbook, Vol. 2: Design and Operations, CRC Press, Boca Raton, Florida, 2013.
CHARLES BAUKAL is the director of the John Zink Institute, which is part of John Zink Co. LLC, where he has worked since 1998. He is the author and editor of 13 books on industrial combustion, including multiple versions of The John Zink Hamworthy Combustion Handbook, and is also an inventor on 11 US patents. Dr. Baukal has 35 years of industrial experience, and earned BS and MS degrees in mechanical engineering from Drexel University, an Ed.D from Oklahoma State University, and a PhD in mechanical engineering from the University of Pennsylvania. He also holds numerous professional engineering and environmental engineering licenses.
BILL JOHNSON began his career in the power industry in 1969 designing coal-fired power plants. He started working at John Zink in 1977, and his roles have included the design, sales, testing and startup of process burners. Mr. Johnson is a co-author of The John Zink Hamworthy Combustion Handbook. He has written several technical papers for the hydrocarbon processing industry (HPI), and has been involved with the John Zink Burner School since 1982.
ROGER NEWNHAM is the senior vice president for OnQuest Canada ULC, a Primoris company. He has over 40 years of experience in the design and operation of direct-fired heaters, including the writing and publishing of four books on this subject. He earned a BSc degree in mechanical engineering from Brighton University in the UK, and is a fellow of the Institute of Mechanical Engineers.
Manual checks complete Ready to purge And Start purge fan Purge flow detected in 1 minute? Start purge Start 5-minute purge timer Purge permissive OK and flow maintained? Timer complete? To light pilots Common alarm Purge fail Purge in progress Alarm reset No No No Yes Yes Yes Purge permissives satisfied Purge in progress
Stop purge fan
Purge complete
FIG. 11. A typical flow diagram for a mandatory purge using an automated burner management system.
Hydrocarbon Processing | MARCH 2016 63