Velocity steam vs Feedrate

[kingkong]

Good day,

i am new member here,hence a lot of thing need to be learned.
i have a question which is keep buzzling in my mind,

The relation of velocity steam and feedrate.
I’ve read in an article saying that velocity steam is added 1%wt from feed rate.meaning to say, once feed rate is increased, velocity steam shall be increased/adjusted as well.

but come another theory saying that, if feedrate is being increased,relative velocity in the tube increased as well, hence velocity steam shall be reduced.

which one is right?

[Claus Graf]

Welcome to the forum.
 
You might find this document helpful. Follow the link:
 
http://www.fwc.com/publications/tech_papers/files/NPRA2005%20FW%20Fired%20Heater%20Design%20%26%20Decoking%20Techniques%2Epdf
 
Regards,
 
CG

[Anonymous]

thanks Claus for the material, really appreciate that.

however can i predict, how much velocity steam need to be added for a given feedrate..
Mass flow can be easily calculated,but it will not consider steam flow inside the tube as well.

i would assume that the steam will flow in annular pattern, where steam will flowing in the middle(core) of the tube, where vacuum residue will cripplingly flow at the tube wall.

For your info, our furnace mass flow is around 230 lb/ft2.s , we are planning to increase our mass flow to 300 lb/ft2.s, quite hard to predict how much velocity steam is needed.unless there is already a correlation between the steam flow needed vs vacuum residue rate.

Nice to discuss with you…

[Anonymous]

there are standards governing the mass velocity and heat flux at coker furnaces?

[Author]

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