Kettle Boiler: shellside velocity criterion
Kettle Boiler: shellside velocity criterion
(OP)
Dear All,
There is a process condenser which generates steam in a kettle-type boiler.
What should the (average)vertical velocity of generated steam be so that a normally accepted level of disentrainment is achieved? What should the velocity be for flowsheet, and what should be the maximum allowable velocity? I would assume that the criterion would be a value for the term rho.v2.
The condenser/ boiler is fitted with a demister, but I feel that the demister should not have to carry out disentrainment below a certain small droplet size.
There is a process condenser which generates steam in a kettle-type boiler.
What should the (average)vertical velocity of generated steam be so that a normally accepted level of disentrainment is achieved? What should the velocity be for flowsheet, and what should be the maximum allowable velocity? I would assume that the criterion would be a value for the term rho.v2.
The condenser/ boiler is fitted with a demister, but I feel that the demister should not have to carry out disentrainment below a certain small droplet size.





RE: Kettle Boiler: shellside velocity criterion
I hope this helps.
RE: Kettle Boiler: shellside velocity criterion
In my experience, the vertical vapor velocity is used for an evaluation of the situation near CHF. The horizontal velocity is used in a seperator type equation. A good discussion of seperators can be found in the Engineering Data Book of GPSA, Vol 1, section 7.
RE: Kettle Boiler: shellside velocity criterion
RE: Kettle Boiler: shellside velocity criterion
One suggestion is to refer to a Art Montemayor post in the Heat Transfer & Thermodynamics engineering forum of several years ago. In his post he discusses both The Souders-Brown and the gravity seperation method.
Another suggestion is to log on to: www.amisto.com/products/eliminators. They have guidance on what vapor load factor in using the Souders-Brown method.
RE: Kettle Boiler: shellside velocity criterion
The URL should contain amistco, not amisto
RE: Kettle Boiler: shellside velocity criterion
1.Excessive pressure drop
2.Effect on bottom tray efficiency,of the vapor is part of a reboiler circuit in distiilation..etc
Up to 5% wt vapor is allowed as long as your DelP is <0.2 psi/100 ft
When you calculate DelP ,use 10% wt liquid as a safety margin
Regards
RE: Kettle Boiler: shellside velocity criterion
My 2 ¢ pledge. One typical problem with this type of boilers resides in the measurement of level. The s.g. of the water in the external indicator is ~1.0, while that inside the boiler may be perhaps ~0.5 due to the steam bubbles.
That is one reason for keeping the top of the kettle well above the top tube of the bundle (say, doubling the height of the top tube) which is itself covered with boiling water.
Sometimes domes with demisters are placed on top of the kettle to improve steam quality and to reduce entrainment of boiler feed water (BFW) in the steam.
If the steam -not generated from clean condensate and containing BFW- is to be further superheated, solid deposits due to entrainment may cause the tubes to fail. However, if the steam is used to reboil a nearby vessel, entrainment is, in general, not considered a major problem.