coil inlet temperature

[daniel]

All,

Will higher coil inlet temperature contributes to higher fouling rate especially on lowerconvection and top radiant section? What is the highest inlet temperature in coker heaters?

Many thanks.

[Anonymous]

sometime the high rate in that zone coming for the high temperature in that above 800F and low velocity (media velocity steam or water) . where do you inject velocity steam or water ? in the inlet of the heater or crossover, what ype of heater do you have? double fire or single?

[Nor Syamrin Wagirin]

the velocity steam @ 760F is introduced at the double fired heater.. the furnace inlet temperature was recently raised from 540F to 600F.. could this contributed to the higher fouling rate observed at the top radiant section?

[Anonymous]

One of the problem of the double fire is the high temperature in the convection section, sometime in this type of heater fyou can see that attain the maximum skin temperature of tubes in this zone before that in the radiation section, for this reason the velocity steam or water is injected into the furnace preferably at the inlet heatre than in the crossover as was the traditional design

[daniel samuel]

what is your cross over temperature, if its less than 400 degC then u don’t have much problem provided u are maintaining the velocity.

[Nor Syamrin Wagirin]

the crossover temperature is in the region of 370-380oC.. what is the right velocity? how much velocity steam should be maintained? 

[Anonymous]

according with the normal design for this heater before the flow is going to the crossover section the lineal velocity have to be over 10 f/seg and the amoung of steam or water injeted have to increase this velocity . Make the calculation

[Sim Romero]

The rule of thumb is 1 to 2 wt% velocity steam but more is better.  The problem with more is better is the high velocities produced in the coke drum and fractionator plus the sour water produced. 
 
Crossover temperatures are typically between 365C to 377C.  At these low temperatures there is no significant thermal cracking/polymerization so the velocities are not critical in the convection section but adding the steam to the crossover does not buy you much in pressure drop – usually.
 
If the feed has high inorganic solids (greater than .2wt%) there can be significant fouling in the convection section and upper radiant section. With solids more steam in the convection section might not be better.

[senthil kumar]

max 315 as per last exp

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