Why are tangential entrances recommended for certain tower feeds?
Tangential feeds, with helical baffles or vapor horns are most commonly found in atmospheric and vacuum crude towers. This type of feed arrangement is preferred when there are very high vapor velocities in conjunction with liquid droplets. The tangential feed entrance causes the vapor to follow the contour of the vessel as it begins to expand and decrease in velocity. A second effect is that the liquid droplets, since they have a greater mass than the vapor molecules, tend to maintain a straight path and collide with the tower wall. This is a desirable effect in that it reduces the entrainment carried to the first section of the tower. In a vacuum tower this is especially beneficial since the liquid droplets in the feed stream are primarily heavy bottoms and metals.
