2 replies to this topic

[and210]

Hi,
I need to size a vertical double barrel separator vessel, I follow the API 12J Recomendations but I don´t know if in this type of separator a retention time is needed for liquid in the first chamber/barrel. Is this barrel only for gas -liquid separation without liquid accumulation ? what is the liquid level recommended in this first barrel?

Thanks for your help.

AND

[Art Montemayor]

AND:

The question of how to design and size a vapor-liquid separator is one subject that has been discussed and described countless number of times on our Forums - ever since we started the Forums.

People still try to literally "re-invent" or "re-interpret" the design and sizing of these very simple apparatti. Please refer to my posts in the past regarding this subject. You will find thorough discussions and definitions of how to design a separator - no matter what type. Milton Beychok participated on a lot of these past threads and he has taken the definition and teaching of sizing separators to a new level on several webpages. Refer to my post on this very subject in a thread yesterday on this very Forum. You will profit a lot if you read Milton's articles.

I have repeated this ad nauseum: a liquid level (or liquid inventory) is kept in the separator ONLY for contributing a residence time that is comensurate with giving the operation of the device sufficient time for an operator to react to process changes. Besides that simple need, a liquid SEAL is needed (from common sense) in order to effect a separation of the two phases: gas flows out over the top and liquid is drained on demand out of the bottom. Contrary to what some members believe, there is NO SEPARATION CONTRIBUTION MADE to the operation by maintaining a liquid level in the separator. This is totally erroneous. All you need to understand this fact is an analysis of the Brown-Souders relationship: only liquid density, vapor density, and an empirical factor play a role in determining the basic dimension (diameter) of the vessel.

A "double-barrel" (as in the famous shot gun) design was developed in the western USA in order to facilitate the separation of the two phases - that is all it was meant to do. A liquid level of approximately 3/4 diameter of the lower "barrel" is normally sufficient to locate a level transmitter to control the level there. The upper barrel is nothing more that a basic separation device that uses gravity (and sometimes demister pads or screens to assist in agglomerating liquid particles) to effect the basic separation. There should be NO LIQUID INVENTORY OR LEVEL in the upper barrel. You can use the Brown-Souders relationship or more sophisticated methods to design the separator. Most designers and fabricators of these devices rely on EMPIRICAL factors and know-how to design and build successful working models.

I hope this helps.

[and210]

Ok, thanks. I know that design and size of separator are widely discussed, the point is that I need to check an existing vertical two barrel separator. It is installed in some Colombian production fields and we need to evaluate its capacity and operation.

AND