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Can you tell me how can cleaning the convection tubes of asphalt heater without change the tubes by chemical or any method because we face several problem and bad condition for convection zone & finned tubes which their fins choked with ashes to improve the convection coil heating duty also access for replacing the deteriorated convection zone refractory?
 
Answers
20/07/2012 A: Mike Watson, Tube Tech International Ltd, mike.watson@tubetech.com
The new Fired Heater Robot now solves the problem of cleaning choked convection zone finned or bare tubes. This dramatically improves convection coil heating duty and avoids replacing finned tubes unneccesarily and does not damage the refractory. Unlike Dry Ice, Chemicals, Water Jetting, Sand Blasting, Explosives, Soot blowers which provide about 1% to 5% surface area contact, the Robot accesses between each row of finned tubes overcoming access problems and substantially improving cleanliness and therefore asset life.
20/07/2012 A: SImone Robinson, Tube Tech International Ltd, simone@tubetech.com
Please find below a list of techniques used to clean fired heaters. There is also a recently introduced robotic cleaning system which is far more effective than any of the methods listed below. Happy to provide more information if needed.
•Hydrant hose wash (off-line): Ineffective. Superficial cleaning. Only used where access doors allow. Only removes the lightest dust. Water damage to refractory.
•Chemical/powder injection (on-line): Cleans in one direction with updraft from burner. Only cleans soft to medium fouling. Does not make 360 degree tube/fin surface contact.
•Soot blowers (on-line): Only effectively cleans within specific vicinity of soot blower nozzle radius. Does not remove hard scale. Does not make 360 degree tube/fin surface contact as soot blowers are static.
•Flame ball (on-line): Can damage refractory, only effective where the sonic blast reaches.
•CO²/Dry Ice (on-line): Ineffective – ice melts!
•CO²/Dry Ice (off-line): Ineffective. Superficial cleaning of what operator can see or large CO² nozzle can touch. Cannot access between finned tubes. Can only be used where access doors allow. Only removes light dust. Extremely slow.
•Traditional Manual Water Jetting (off-line): Ineffective. Superficial cleaning. Can only be used where access doors allow. Water damage to refractory, Cannot access between finned tubes.
•Sand/Grit blasting (off-line): Ineffective. Erodes tubes/fins. Lots of dust. Need to collect blast media. Grit sticks between tubes. Creates ‘key’ thus increasing future fouling rates. Cannot access between finned tubes.
•Air blasting (off-line): Can only remove light dust. Creates lots of dust. Superficial cleaning. Cannot access between finned tubes. Can only be used where access doors allow.
20/07/2012 A: Sudhakara Babu Marpudi, Dangote Oil Refinery Company, m_sudhakarababu@yahoo.com
Normal way to clean the finned tubes in Convection banks is to run soot blowers. If you have soot blowers installed in your furnace convection zone, try them with a measured quantity of condensate left in the soot blowing steam header. The effect will be similar to spalling (sudden cooling caused by condensate resulting in cracks i flakes in the hard soot deposits and blowing off the flakes with high velocity steam) and there will be relief. Do it with small quantities of condensate initially and increase the condensate levels as the experience is gained with the activity.
19/07/2012 A: SImone Robinson, Tube Tech International Ltd, simone@tubetech.com
We have a tried and tested a robotic method for cleaning convection tubes which a) removes all deposits remotely b) provides better heat transfer and c) reduces running costs. Please visit our website to review cases studies on robotic cleaning of fired heaters.