Q & A > Question Details
Is it a myth or reality that in a refinery fired heater for the same throughput, same coil outlet temperature and everything else being the same, a fuel oil fired furnace will give a lower skin temperature in the convection section than a natural gas fired one?
 
Answers
16/04/2016 A: L K Maheshwari, Essar Oil, laju1984@yahoo.co.in
Skin temperature has nothing to do with Fuel oil firing or Fuel gas Firing.Fuel oil has much more calorific value than fuel gas so fuel consumption will be lower nothing else.
19/12/2015 A: RUPAM MUKHERJEE, ENGINEERS INDIA LIMITED, rupammukherjee86@gmail.com
I m not sure what the convection skin temperature is meant with.
Is it the firebox temperature or the radiant section tube metal temperature?
These are two I should be concerned with.
Both of these may decrease by firing fuel oil. FO firing generally calls for a higher excess air requirement, typically 5-8% higher than gas.
This leads to higher flue gas quantity and better convective heat transfer. Thus, the radiant load is pretty reduced and the skin/ arch temperature reduces.
15/01/2014 A: Mike Watson, Tube Tech International Ltd, mike.watson@tubetech.com
Don't forget that oil fired furnaces typically foul more quickly and settles deep inside the finned convection bank's and often goes unnoticed. To clean convection banks back to as new condition Www.tubetech.com have developed a bespoke robotic cleaning and inspection technology that is incredibly fast and efficient because it physically penetrates between every tube row, up to 12 deep, typically 10 mm to 15 mm between finned tubes. The same applies for outer tube surfaces of assets such as steam methane reformers, HRSG's, radiant sections etc. Their system removes deposit from between both finned or bare tubes ranging from compact refractory dust - to solid concrete, even coke hydrocarbons. What's good about the Tube Tech International service is that they also simultaneously inspect between the finned tubes after cleaning, using a "Blade Camera", again small enough to penetrate between the 3 to 10 mm tube space. Return on investment as you can imagine is extremely quick.
03/05/2013 A: Dhiren Rindani, Reliance Industries Ltd, dhiren.rindani@ril.com
Liquid fuel having higher carbon needs less air for combustion and hance higher flame temperature, more radiation, higher heat transfer in radiation zone. 12Kg C needs 32 Kg O2
On the other hand gaseous fuel having higher H2 needs more air for combustion (1kg H2 needs 8 Kg O2) and hence lower flame temperature, less radiation, higher heat transfer in convection zone. convection zone efficiency depends on mass flow and velocity, radiation zone efficiency depends on flame temperature and distance between flame and tubes.
12/12/2012 A: Sudhakara Babu Marpudi, Oman Refineries and Petroleum Industries Company, m_sudhakarababu@yahoo.com
Fuel Oil fired burners in good health have lower probability high skin temperatures in Convection zone than gas fired burners. Fuel Oil fired generally contributes to the good heat supply in the radiation zone. Gas fired burners if the combustion air supply patterns (combustion air registers) are not good can take the combustion to the the Convection zone because of the pressure drop offered by the convection zone allows the combustion air and the Fuel gas to come in contact with each other. This phenomena could lead to higher skin temperatures in convection section. However Fuel Oil burners with extremely longer flames than desired, also can take the flames close to the arch leves of a furnace and can cause higher skin temperatures in convection while the radiation zone skin thermocouples can sit in the colder zones of the Fuel oil flames. So every thing depends on the mechanical health of the burner parts.