Distillation column control method and system

Claim 2

COMBING SAID SIGNALS TO, TR AND RE IN AN ACTUAL INTERNAL FLOW RATE COMPUTER TO PRODUCE A SIGNAL RA REPRESENTATIVE OF THE ACTUAL INTERNAL FLOW RATE BASED ON THE RELATIONSHIP: RA = RE (1 + CONSTANT(TO - TR)); M. COMPARING SAID SIGNALS RP AND RA AND PRODUCING A SIGNAL RO REPRESENTATIVE OF THE DIFFERENCE THEREBETWEEN; AND N. MANIPULATING THE FLOW RATE OF SAID STREAM OF EXTERNAL REFLUX RESPONSIVE TO SAID SIGNAL RO TO OBTAIN AN OVERHEAD DISTILLATE PRODUCT CONTAINING A DESIRED CONCENTRATION OF SAID HEAVY KEY COMPONENT.

Claim 5

The method of claim 1 which is further characterized to include the steps of: sensing the liquid level within said heated reboiler and producing a signal SL varying directly with the rise and fall thereof; and adjusting the heat input to said reboiler with said signal so that said liquid level is maintained substantially constant.

Claim 6

In a distillation column system for fractionating a multi-component feed stream containing a light key component and a heavy key component into an overhead distillate product containing a desired concentration of said heavy key component and a bottoms product containing a desired concentration of said light key component, said distillation column system including a heated reboiler, an overhead vapor condenser, an external reflux accumulator and means for returning a stream of external reflux to said distillation column, the improvement which comprises: a. means for measuring the flow rate of said multi-component feed stream and establishing a physical signal F directly proportional thereto; b. means for measuring the temperature of said feed stream and establishing a physical signal TF directly proportional thereto; c. means for analyzing said multi-component feed stream and establishing physical signals CF representative of the concentrations of at least said light and heavy key components contained therein; d. means responsive to the physical signals TF and F for determining the enthalpy of said feed stream and establishing a physical signal FE representative thereof; e. means responsive to said physical signals F and CF and to constant physical signals LB and HD which are representative of the desired concentrations of key components in the overhead and bottoms products respectively for determining and establishing a physical signal B representative of the required bottoms product flow rate based on the following relationship: B f(F, CF, HD, LB); f. means for adjusting the actual bottoms product flow rate with the signal B; g. means for measuring the pRessure of said distillation column and establishing a physical signal SP directly proportional thereto; h. means for increasing or decreasing the cooling of said external reflux stream with increases or decreases in the physical signal established in step (g) so that the pressure of said distillation column is decreased or increased accordingly; i. means responsive to the physical signals F, CF, FE, HD and LB for producing a signal RP representative of the predicted internal reflux flow rate required to produce an overhead distillate product containing the desired concentration of said heavy key component based on the relationship: RP f(F, CF, FE, HD, LB); j. means for measuring the temperature of the overhead vapors exiting said distillation column and establishing a physical signal TO directly proportional thereto; k. means for measuring the temperature of said stream of external reflux and establishing a physical signal TR directly proportional thereto; l. means for measuring the flow rate of said stream of external reflux and establishing a physical signal RE directly proportional thereto; m. means responsive to said physical signals TO, TR and RE for producing a physical signal RA representative of the actual internal reflux flow rate based on the relationship: RA RE(1 + constant(TO - TR)); n. means responsive to the physical signals RP and RA for establishing a physical signal RO varying directly with the difference between said signals; and o. means for adjusting the external reflux flow rate with the signal RO thereby adjusting the actual internal reflux flow rate to a level substantially equal to the predicted internal reflux flow rate.

Claim 7

In a distillation column system for fractionating a multi-component feed stream containing a light key component and a heavy key component into an overhead distillate product containing a desired concentration of said heavy key component and a bottoms product containing a desired concentration of said light key component, said distillation column system including a heated reboiler, an overhead vapor condenser, an external reflux accumulator and means for returning a stream of external reflux to said distillation column, the improvement which comprises: a. means for measuring the flow rate of said multi-component feed stream and establishing a physical signal F directly proportional thereto; b. means for measuring the temperature of said feed stream and establishing a physical signal TF directly proportional thereto; c. means for analyzing said multi-component feed stream and establishing physical signals CF representative of the concentrations of at least said light and heavy key components contained therein; d. means responsive to the physical signals TF and F for determining the enthalpy of said feed stream and establishing a physical signal FE representative thereof; e. means responsive to said physical signals F and CF and to constant physical signals LB and HD which are representative of the desired concentrations of key components in the overhead and bottoms products respectively for determining and establishing a physical signal B representative of the required bottoms product flow rate based on the following relationship: B f(F, CF, HD, LB); f. means for adjusting the actual bottoms product flow rate with the signal B; g. means for measuring the pRessure of said distillation column and establishing a physical signal SP directly proportional thereto; h. means for increasing or decreasing the cooling of said external reflux stream with increases or decreases in the physical signal established in step (g) so that the pressure of said distillation column is decreased or increased accordingly; i. means responsive to the physical signals F, CF, FE, HD and LB for producing a signal RP representative of the predicted internal reflux flow rate required to produce an overhead distillate product containing the desired concentration of said heavy key component based on the relationship: RP f(F, CF, FE, HD, LB); j. means for measuring the temperature of the overhead vapors exiting said distillation column and establishing a physical signal TO directly proportional thereto; k. means for measuring the temperature of said stream of external reflux and establishing a physical signal TR directly proportional thereto; l. means for measuring the flow rate of said stream of external reflux and establishing a physical signal RE directly proportional thereto; m. means responsive to said physical signals TO, TR and RE for producing a physical signal RA representative of the actual internal reflux flow rate based on the relationship: RA RE(1 + constant(TO - TR)); n. means responsive to the physical signals RP and RA for establishing a physical signal RO varying directly with the difference between said signals; and o. means for adjusting the external reflux flow rate with the signal RO thereby adjusting the actual internal reflux flow rate to a level substantially equal to the predicted internal reflux flow rate.

Claim 8

The distillation column system of claim 3 which is further characterized to include: means for sensing the level of liquid existing within said heated reboiler and establishing a physical signal SL directly proportional to the rise and fall of said liquid level; means responsive to said physical signal representative of the rise and fall of said liquid level for increasing or decreasing the heat input to said reboiler thereby decreasing or increasing the liquid level within said reboiler.