Constraint control of a fractional distillation process
AssigneePhillips Petroleum Company
InventorGary L. Funk
Life of this patent
Estimating the term…
Abstract
In a fractional distillation process in which a compressor is used to supply heat to the fractional distillation process, a plurality of signals representative of a plurality of speeds of the compressor, required to prevent various process constraints from being violated or maintain various desired process operating conditions respectively, are compared. The signal representative of the highest compressor speed is utilized to control the compressor. In this manner, the compressor is run at the minimum speed required to satisfy the various process constraints and maintain the desired process operating conditions.
Claims7
Apparatus comprising:
- a fractional distillation column having a reboiler associated therewith;
- means for providing a feed stream containing components to be separated to said fractional column;
- a compressor having a suction inlet and a discharge outlet;
- means for providing an overhead stream from said fractional distillation column to the suction inlet of said compressor;
- first control valve;
- means for providing fluid from the discharge outlet of said compressor through said first control valve to said reboiler to thereby supply heat to said fractional distillation column;
- means for establishing a first signal representative of the actual position of said first control valve;
- means for establishing a second signal representative of the desired position of said first control valve;
- means for comparing said first signal and said second signal and for establishing a third signal which is responsive to the difference between said first signal and said second signal, wherein said third signal is scaled so as to be representative of the speed of said compressor required to maintain said first signal substantially equal to said second signal;
- means for establishing a fourth signal representative of the actual suction pressure for said compressor;
- means for establishing a fifth signal representative of the maximum allowable suction pressure for said compressor;
- means for comparing said fourth signal and said fifth signal and for establishing a sixth signal which is responsive to the difference between said fourth signal and said fifth signal, wherein said sixth signal is scaled so as to be representative of the speed of said compressor required to maintain the magnitude of said fourth signal substantially equal to the magnitude of fifth signal;
- means for establishing a seventh signal representative of the actual discharge pressure for said compressor;
- means for establishing an eighth signal representative of the minimum allowable discharge pressure for said compressor;
- means for comparing said seventh signal and said eighth signal and for establishing a ninth signal which is responsive to the difference between said seventh signal and said eighth signal, wherein said ninth signal is scaled so as to be representative of the speed of said compressor required to maintain the magnitude of said seventh signal substantially equal to the magnitude of said eighth signal;
- high select means;
- means enabling provision of said third signal, said sixth signal and said ninth signal as inputs to high select means, wherein the one of said third, sixth and ninth signals representing the highest speed of said compressor is selected by high select means and is provided as a tenth signal from said high select means;
- and
- means for controlling the speed of said compressor in response to said tenth signal.
Dependencies are inferred from the claim text.