3 replies to this topic

[CRB]

I want to check an existing horizontal vessel size due to increasing liquid flow rate. The vessel is simply a degasser and has no mist eliminator. In the GPSA section 7 I assumed a particle size and calculated the terminal velocity. I then used this terminal velocity in the following equation:
L = 4Qa / 3.142VtDv. However this equation assumes no liquid retention and I need to have a 50% liquid level in the degasser. How do I now modify the diameter to use in this equation ( I assumed half of the crosssectional area and calculated a dimater based on this - is this a valid assumption?)

Also in vessels with mist eliminators there is a maximum allowable vapor velocity criteria using a K factor. Is there a recommended range of K factors for vessels without demisters??

[mbeychok]

CRB:

Also in vessels with mist eliminators there is a maximum allowable vapor velocity criteria using a K factor.  Is there a recommended range of K factors for vessels without demisters??

<{POST_SNAPBACK}>

In regard to the above question, I believe you are asking about the K factor to be used with the Souders-Brown equation. The GPSA Engineering Data Book recommends the following k values for vertical drums with horizontal mesh pads (at the denoted operating pressures):

0 psig: 0.35
300 psig: 0.33
600 psig: 0.30
900 psig: 0.27
1500 psig: 0.21

GPSA Notes:
1. K = 0.35 at 100 psig; subtract 0.01 for every 100 psi above 100 psig
2. For glycol or amine solutions, multiply above K values by 0.6 – 0.8.
3. Typically use one-half of the above K values for approximate sizing of vertical separators without mist eliminators.
4. For compressor suction scrubbers and expander inlet separators, multiply K by 0.7 – 0.8

Although the GPSA recommended factor are for vertical drums, they may also apply to horizontal drums.

[djack77494]

I've heard that there are some "high efficiency" demisters that claim to enhance droplet removal beyond that achieved with conventional mesh or chevron elements. A former coworker told me that with these devices one could effectively increase the K factor beyond 0.35 (Imperial units) which I've always thought of as a maximum. I'd be interested in any comments on this topic and also a description of any enhanced approaches to demisting. What K values can be attained?
Regards,
Doug

[benabed]

I've heard that there are some "high efficiency" demisters that claim to enhance droplet removal beyond that achieved with conventional mesh or chevron elements.  A former coworker told me that with these devices one could effectively increase the K factor beyond 0.35 (Imperial units) which I've always thought of as a maximum.  I'd be interested in any comments on this topic and also a description of any enhanced approaches to demisting.  What K values can be attained?
Regards,
Doug

<{POST_SNAPBACK}>

I have read in the litterature of mist eliminators manufactrers that some devices can have a k factor of 0.65 such as vane pad type with horizontal flow invertical drums. Also I am interested to know how to calculate the spacing in the vessel between the mst eliminator and the inlet and the outlet nozzles.
best regards,
Lazreg