Preheat control for a fractional distillation process
AssigneePhillips Petroleum Company
InventorsGary L. Funk, Terrence A. Davis, Bruce A. Jensen
Life of this patent
Estimating the term…
Abstract
A computer control system for automatically optimizing the temperature of the feed supplied to a distillation column from a fuel fired preheat furnace, wherein the furnace temperature is manipulated in response to a measured ratio of distillate flow (D) from the tower to fuel flow (F) to the furnace. The D/F ratio is maximized by periodically comparing the present value of D/F to the previous value and incrementally increasing the furnace temperature as long as the D/F ratio increases. When no change is detected or the D/F ratio starts to decrease the furnace temperature is incrementally decreased until the D/F ratio again increases and reverses the control action once more.
Claims12
Apparatus comprising:
- a distillation column;
- a furnace for preheating feed to said distillation column;
- means for supplying fuel to said furnace wherein the combustion of said fuel supplies heat to said feed;
- means for introducing feed heated in said furnace into said distillation column;
- means for withdrawing at least one distillate stream from said distillation column, wherein each said distillate stream flows a fraction of said feed;
- means for establishing a first signal representative of the total distillate flow rate;
- means for establishing a second signal representative of the fuel flow rate to said furnace;
- means for establishing a third signal representative of the ratio of said first signal to said second signal;
- means for withdrawing a residue stream from the bottom of said distillation column;
- means for establishing a fourth signal representative of the viscosity of said residue based on the experimentally determined relationship of said viscosity to said third signal;
- means for establishing a fifth signal representative of the actual viscosity of said residue;
- means for establishing an initial value of a sixth signal representative of the desired viscosity of said residue, wherein said initial value of said sixth signal is responsive to said fourth signal;
- means for updating said sixth signal, wherein said sixth signal is incremented or decremented responsive to changes in said third signal;
- means for comparing said fifth signal and said sixth signal and for establishing a seventh signal responsive to the difference between said fifth signal and said sixth signal wherein said seventh signal is scaled so as to be representative of the temperature of said furnace required to maintain said fifth signal substantially equal to said sixth signal;
- and
- means for manipulating the temperature of said furnace in response to said seventh signal.
A method for controlling a fractional distillation process wherein the feed, which is preheated in a fired furnace, is provided to a fractional distillation column and wherein at least one distillate stream is withdrawn from said fractional distillation column, said method comprising the steps of:
- establishing a first signal representative of the total distillate flow rate.
- establishing a second signal representative of the fuel flow rate to said furnace;
- establishing a third signal representative of the ratio of said first signal to said second signal;
- establishing a fourth signal representative of the viscosity of said residue based on the experimentally determined relationship of said viscosity to said third signal;
- establishing a fifth signal representative of the actual viscosity of said residue;
- establishing an initial value of a sixth signal representative of the desired viscosity of said residue, wherein said initial value of said sixth signal is responsive to said fourth signal;
- updating said sixth signal, wherein said sixth signal is incremented or decremented responsive to changes in said third signal;
- comparing said fifth signal and said sixth signal and establishing a seventh signal responsive to the difference between said fifth signal and said sixth signal wherein said seventh signal is scaled so as to be representative of the temperature of said furnace required to maintain said fifth signal substantially equal to said sixth signal;
- and
- manipulating the temperature of said furnace in response to said seventh signal.
Dependencies are inferred from the claim text.