Claims
- 1. A method for controlling a fractionation tower and process wherein feed and heat flow into the tower and feed is distilled and separated into distillate and bottoms, said distillate flowing from the tower through an overhead line into a condenser where it is condensed before it is drawn off as product with a portion of this product being returned to the tower as reflux, and said bottoms being allowed to at least partially collect in the tower thereby establishing a liquid level which is allowed to fluctuate within predetermined limits, which method comprises: monitoring the pressure within said tower; providing a signal thereof and transmitting said signal to a pressure controller; utilizing said pressure controller to generate a scaled ouput signal which increases when the measured pressure decreases and vice versa; simultaneously generating and using a composite signal:
- Q.sub.I =K.sub.p (K.sub.R +K.sub.D -K.sub.F)
- where
- Q.sub.I is the heat required by the fractionation tower;
- K.sub.p is the pressure controller output signal;
- K.sub.R is the reflux flow rate signal;
- K.sub.D is the distillate flow rate signal;
- K.sub.F is a scaled feed flow rate signal; and; transmitting said composite signal to a second controller which controls heat input to provide an energy balanced and stable fractionation tower and process even during periods of severe and extreme operating conditions by controlling amount of reflux and heat into said tower and amount of distillate and bottom exiting said tower.
- 2. The method of claim 1 wherein the signal Q.sub.I and second flow controller are used to control heat input at a reboiler.
- 3. An apparatus for controlling a fractionation tower and process where feed and heat flow into the tower and feed is distilled and separated into distillate and bottoms, said distillate flowing from the tower through an overhead line into a condenser where it is condensed before it is drawn off as product with a portion of this product being returned to the tower as reflux, and said bottoms being allowed to at least partially collect in the tower thereby establishing a liquid level which is allowed to fluctuate within predetermined limits, which apparatus comprises: means for monitoring the pressure within said tower and for transmitting a signal thereof to a pressure controller; said pressure controller being capable of generating a scaled output signal which increases when the pressure signal decreases and vice versa; means for generating a composite signal:
- Q.sub.I =K.sub.p (K.sub.R +K.sub.D -K.sub.F)
- where
- Q.sub.I is the heat required by the fractionation tower;
- K.sub.p is the pressure controller output signal;
- K.sub.R is the reflux flow;
- K.sub.D is the distillate flow;
- K.sub.F is a scaled feed flow signal; and means for transmitting said composite signal to a second controller which controls heat input into said tower so that said composite signal can be used to provide an energy balanced and stable fractionation tower and process by controlling amount of reflux and heat into said tower and amount of distillate and bottom exiting said tower.
- 4. The apparatus of claim 3 wherein a pressure transmitter situated in the overhead line of the fractionation tower monitors tower pressure provides a signal directly proportional to this pressure to the pressure controller.
- 5. An apparatus for controlling the heat input to a fractionation tower comprising:
- flow meter for measuring the reflux rate K.sub.R ;
- flow meter for measuring the distillate flow rate K.sub.D ;
- means for measuring the scaled feed flow rate K.sub.F ; means for measuring the pressure in said tower and transmitting a signal thereof to a pressure controller for generating a scaled signal K.sub.p which increases when the pressure signal decreases and vice versa; means for generating a composite signal corresponding to K.sub.p (K.sub.R +K.sub.D -K.sub.F); and a second controller responsive to said composite signal for controlling heat input so that said composite signal can be used to provide an energy balanced and stable fractionation tower by controlling amount of reflux and heat into said tower and amount of distillate and bottom exiting said tower.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of patent application Ser. No. 614,205, filed Sept. 17, 1975, now abandoned.
US Referenced Citations (12)
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
614205 |
Sep 1975 |
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