Purpose:

The purpose of this experiment is to introduce students to elementary aspects of the most widespread separation technique in the chemical industry – distillation. The assignments allow the important concepts of reflux and reboil to be demonstrated, and to examine how these variables influence the purity of the distillate and bottoms streams. Because the column is fitted with view ports on many trays, hydrodynamic effects such as flooding and weeping can also be observed.

The parameters that can be varied in this experiment are:

• feed flow rate
• feed tray
• reflux rate
• steam heating rate to reboiler

• purity of distillate and bottom streams
• tray efficiency
  
• tray temperature
  
• visualization of column hydrodynamics
  
• dynamic response to disturbance

Experimental Setup:

A 13-tray bubble-cap column with an equilibrium reboiler and total condenser is available. Consult column blueprints for tray spacing and determination of column diameter. The reboiler is heated using a steam coil. Tanks are available for distillate and bottoms collection. Feed can be introduced on any of five trays, and most trays are fitted with liquid and vapor sample ports, thermocouples and view ports. Feed rate, reflux rate, steam heating rate, and distillate and bottoms flow rate (not all of these variables are independent, of course) are computer-controlled. The computer also provides data acquisition for the tray temperatures. Compositions are measured using gas chromatograph.

This experiment demonstrates the complex interrelationship between the many variables that can be measured, manipulated, and controlled on a distillation tower. By varying the feed tray (and other operating variables) the students get a chance to practice retrofitting the column to changing demands (i.e., changing feed composition with fixed product purities or changing purity requirements on one or both of the product streams).

Notes:

1. Check the composition of the feed before beginning experimentation. If the feed is lower than 20 mole % methanol, ask the laboratory staff to add methanol.
   
2. For determination of steady state operation, compare individual tray temperatures (within a designated time frame, e.g., ten minutes).
   
3. Avoid weeping and flooding conditions by ensuring that the reboiler level is consistently in the green range.
   
4. For the preliminary presentation calculate the proper flow rate settings for the column. Assume a 50% tray efficiency. Also be sure to specify exactly what variables will be measured to achieve the goals set in the project statement. Be sure to discuss the methods to be utilized in the determination of these variables.
   
5. For more information on the distillation column, review the “detailed descriptions” document accessible on the course website

Flow Charts for the Distillation Column:

• Overhead System
• Column System
• Tank System

1. New LabView program description

2. Column startup manual

3. Column operation manual

Detailed Procedure by Group C