Vessel Internals – Flow Straightening

Usually heavy gravity and mid-range crude oils are relatively easy to degas and do not have serious foaming tendencies. When the liquid gravity is above 40API (a light crude or condensate) we use lami-flow stablisers to produce essentially laminar flow of the gas, which in turn promotes free-settling of any liquid droplets. For this purpose vertical parallel plates are used to reduce the hydraulic radius of the vapour area without any appreciable reduction in flow area or velocity. The lami-flow stabiliser is capable of solving most foaming problems.

Foam Breakers

However, knowledge of API gravity alone is not sufficient to determine whether or not crude oil will exhibit a serious tendency to foam. For crudes that have a serious tendency to foam, foam breakers can be extremely effective. Usually foam breakers are corrugated plates with pockets. Large bubbles burst on contact with the pack. Smaller bubbles are forced into a smaller area, thereby stretching and thinning the liquid film until it bursts. In cases of extreme foaming structured packing can be used to provide the high surface area to stop the foam migrating and promote the drainage of liquid films that contain the entrapped vapour.