Abstract:
A multicomponent feed is fractionated in a distillation column to produce an overhead vapor stream, which is then partially condensed and passed to an accumulator to obtain a liquid external reflux stream and an overhead vaporous product stream. The accumulator pressure is maintained substantially constant. A signal representative of the predicted accumulator temperature is established, based on measurements of feed flow rate, feed composition, overhead product specifications, accumulator pressure, and bottoms product flow rate. The predicted accumulator temperature is compared with the measured accumulator temperature to obtain a bias signal. This bias signal is used to manipulate the bottoms product flow rate to effect the adjustment of the accumulator temperature to a value at which the concentration of a key component of the overhead vaporous product is substantially equal to the desired concentration thereof.