Automatic control of feedstock vacuum towers
AssigneeApplied Automation, Inc.
InventorBruce A. Jensen
Life of this patent
Estimating the term…
Abstract
In a fractional distillation tower which is divided into a plurality of sections by total drawoff trays, and wherein at least one fraction is withdrawn from each section. The cut point temperature between fractions is determined based on the partial pressure and temperature of the vapor in the upper portion of a section. The thus determined cut point temperature may be compared to a set point with the results of the comparison being utilized to maintain the actual cut point temperature between fractions substantially equal to the desired cut point temperature.
Claims15
Apparatus comprising:
- a fractional distillation tower;
- means for providing a feed oil stream containing hydrocarbons to said fractional distillation tower, wherein the hydrocarbon components of said feed oil stream exhibit a sufficiently wide boiling range to yield a plurality of fractions;
- a first total drawoff tray located at a first point along the length of said fractional distillation tower, wherein the volume of said fractional distillation tower above said first total drawoff tray defines a first section;
- means for maintaining a desired liquid level above said first total drawoff tray, wherein said first section includes a first liquid zone and a first vapor zone;
- means for withdrawing an overhead vapor fraction from said fractional distillation tower;
- condenser means for at least partially condensing said overhead vapor fraction;
- means for withdrawing a first liquid fraction from said condenser means;
- means for providing a first reflux stream at a second point along the length of said fractional distillation tower, wherein said second point is located in the upper part of said first vapor zone;
- means for withdrawing a second liquid fraction from said fractional distillation tower, wherein said second liquid fraction is withdrawn from said first total drawoff tray;
- means for withdrawing a bottom fraction from said fractional distillation tower;
- means for establishing a first signal representative of the vapor pressure at the top of said fractional distillation tower;
- means for establishing a second signal representative of the pressure differential between said first total drawoff tray and the top of said fractional distillation tower;
- means for establishing a third signal representative of the vapor temperature in said first vapor zone;
- computer means, operatively connected to respond to said second signal and said third signal, for establishing a fourth signal which is representative of the cut point temperature between said first liquid fraction and said second liquid fraction;
- means for establishing a fifth signal representative of a desired cut point temperature between said first liquid fraction and said second liquid fractions;
- 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;
- and
- means for manipulating the flow rate of said first reflux stream in response to said sixth signal to thereby maintain said fourth signal substantially equal to said fifth signal.
A method for maintaining a desired cut point between fractions withdrawn from a fractional distillation tower, wherein a feed oil stream containing hydrocarbons is distilled in said tower, wherein the hydrocarbon components of said feed oil stream exhibit a sufficiently wide boiling point range to yield a plurality of fractions, wherein a total drawoff tray is located at a first point along the length of said fractional distillation tower, wherein the volume of said fractional distillation tower above said total drawoff tray defines a section of said fractional distillation tower, wherein an overhead vapor stream is withdrawn from an upper portion of said fractional distillation tower, cooled, and then provided to an overhead accumulator, said method comprising the following steps:
- maintaining a liquid level above said drawoff tray, such that said section of said fractional distillation tower includes a liquid zone and a vapor zone;
- withdrawing a first liquid fraction from said overhead accumulator;
- providing a reflux stream at a second point along the length of said fractional distillation tower wherein said second point is located above said first point in the upper part of said vapor zone;
- withdrawing a second liquid fraction from said fractional distillation tower from said total drawoff tray;
- withdrawing a bottom fraction from said fractional distillation tower;
- establishing a first signal representative of the vapor pressure at the top of said fractional distillation tower;
- establishing a second signal representative of the pressure differential between said total drawoff tray and the top of said fractional distillation tower;
- establishing a third signal representative of the vapor temperature in said vapor zone;
- establishing a fourth signal which is representative of the cut point temperature between said first liquid fraction and said second liquid fraction;
- comparing said fourth signal and said fifth signal and for establishing a sixth signal responsive to the difference between said fourth signal and said fifth signal;
- and
- manipulating the flow rate of said reflux stream in response to said sixth signal to thereby maintain said fourth signal substantially equal to said fifth signal.
Dependencies are inferred from the claim text.