Tuesday, April 24, 2007

Packed Column...sometime better than tray column

PACKED COLUMN
A packed bed is a hollow tube or pipe that is filled with a packing material. The packing can be randomly filled small objects like Raschig rings or else it can be a specifically designed structured packing.

The purpose of a packed bed is typically to improve contact between two phases in a chemical or similar process. Packed beds can be used in a chemical reactor, distillation process, or a scrubber, but packed beds have also been used to store heat in chemical plants. In this case, hot gases are allowed to escape through a vessel that is packed with a refractory material until the packing is hot. Air or other cool gas is then fed back to the plant through the hot bed, thereby pre-heating the gas feed.


WHY PACKED COLUMN IS USED ?
Packed columns are preferred to tray columns
  1. PROCESS WITH 2-PROCESS FLUIDS (liquid- gas, liquid-liquid, liquid-solid, liquid-vapor) are in contact and separation take place.
  2. LOW PRESSURE DROP (typically 0.35 - 2mm Hg per theoretical plate for packed column compared to 3.05m Hg for trays)
  3. HIGH CAPACITY
  4. LOW LIQUID HOLD-UP
  5. GOOD RESISTANCE TO FOULING

DESIGN & APPLICATION

Packed Column Design, an article from Cheresources, well known online Chemical Engineering information site, briefly describe step-by-step approach in packed column sizing.

Sizing of Packed Towers in Acid Plants, Cheresources - An application for Packed column with absorption of SO3 in the Interpass and Final Towers and recovers as product sulfuric acid...

FREE Packed Column spreadsheet from
Cheresources .

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