As mentioned several times this McCabe-Thiele diagram can be used to determine the number of theoretical stages too. Knowing the number of theoretical stages is crucial in order to get a rough estimation of the cost and other aspects of distillation.
First of all, mark all those given or known compositions in the diagram. Then draw a feed line from the feed composition that depends on the feed phase. In this example we again use a saturated-liquid feed. So the feed line will be a vertical line.
Secondly draw an operating line for the rectifying section, provided we know the reflux ratio that we want to operate at. Since it is known, we can simply calculate the slope and/or the y-intercept of the operating line. Draw the line until it intercepts with the feed line.
Next step is to connect the intersection point with the bottom composition, forming another straight line. This is the operating line for a stripping section of the column.
Last step is to draw steps in between those operating lines and the equilibrium curve. This is drawn in red. In total we need 10 stages, 9 stages and 1 reboiler as reboiler is counted as a stage as well.
First of all, mark all those given or known compositions in the diagram. Then draw a feed line from the feed composition that depends on the feed phase. In this example we again use a saturated-liquid feed. So the feed line will be a vertical line.
Secondly draw an operating line for the rectifying section, provided we know the reflux ratio that we want to operate at. Since it is known, we can simply calculate the slope and/or the y-intercept of the operating line. Draw the line until it intercepts with the feed line.
Next step is to connect the intersection point with the bottom composition, forming another straight line. This is the operating line for a stripping section of the column.
Last step is to draw steps in between those operating lines and the equilibrium curve. This is drawn in red. In total we need 10 stages, 9 stages and 1 reboiler as reboiler is counted as a stage as well.
No comments:
Post a Comment