Category: Food Engineering

Jul 03

Feed Plate and Various Feed Conditions

The plate where feed is administered is called feed plate. In feed plate, the liquid rate or vapor rate or both may change depending upon thermal condition of feed.

Cold feed: the entire feed stream adds to the liquid flowing down the column. In addition, some vapor condenses to heat the feed to boiling point. This makes the liquid flow even greater in stripping section and decrease flow of vapor in rectifying section. V < V̅ and L̅ > L +F. Read more

Jun 27

Minimum Reflux (infinite no. of plates)

At any reflux less than total, the number of plates needed for given separation is larger than total reflux. The number of plate increases continuously as reflux ratio is decreased. As the ratio becomes smaller, no. of plates required becomes very large and at definite minimum reflux ratio, number of plate become infinite.

This minimum reflux ratio can be defined as the reflux ratio (Rm) that will require infinite no. of trays for given desired separation of XD and XB. This corresponds to minimum vapor flow in tower and hence minimum reboiler and condenser sizes. Read more

Jun 26

Total Reflux (minimum no. of plates)

The total reflux condition represents operation with no product removal. All the overhead product is condensed and returned as reflux. Consequently D = 0 and reflux ratio becomes infinite. (RD = L/D = ∞). This in turn, makes the operating line, 45° line where V = L and slope = 1. The operating line then coincides with diagonal. This condition is called total reflux. Read more