Phillips Petroleum Company

Applied Automation, Inc.

Bruce A Jensen

Terrence A Davis

Gary L Funk

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tower which is divided into a plurality of sections by total drawoff trays, and wherein at least one fraction is withdrawn from each section.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.

Automatic control of feedstock vacuum towers

A computer system for a zone fired furnace generates a plurality of temperature set point signals for a plurality of furnace zones. The set point signals are derived from a master controller acting on the measured temperature of fluid that is heated in the plurality of furnace zones and then combined to form a heated stream. The master signal, which is a velocity type signal, is provided to a plurality of zone control stations corresponding to the plurality of furnace zones. Each zone control station integrates the master signal, and then biases the master signal for use as a zone temperature set point. The zone control station can be used to bias the individual coils so as to balance the temperature of the coils with respect to each other, or to intentionally unbalance one or more coils, as desired, so as to improve furnace operations. In addition a tracking signal is generated in each zone control station which accurately tracks the set point of it's associated zone temperature controller to facilitate automatic bumpless transfer from manual to automatic even when a zone temperature is limited to a maximum or minimum value.

Furnace zone temperature control

A supervisory computer automatically equalizes the temperature of effluent streams of a multipass heating system to maximize heat transfer, without substantially disturbing a desired total flow through the heating system. Temperature control is achieved by manipulating the division of a feed stream among the multiple passes. In addition, if the flow in one or more passes cannot be manipulated, the control scheme automatically equalizes the temperatures of the remaining passes. This is accomplished by calculating a flow rate for adjusting the flow through the number of passes under supervisory control to a value, which in addition with any uncontrolled flow, will provide the desired total flow through the heating system. This adjusted flow rate is used as an approximate set point for the flow rate in each controlled pass. The adjusted flow rate signal is modified for control of each individual pass by applyng a bias through a conventional controller acting on a weighted average temperature signal. This temperature biased signal is further modified by applying another bias through a gap controller acting on an average flow signal. The thus twice biased signal is provided as a flow rate set point for it's individual pass.

Preheat temperature balancing control

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.

Preheat control for a fractional distillation process

In a fractional distillation process in which both a heating fluid and a waste heat stream are utilized to supply heat to the fractional distillation process, the heat input to the fractional distillation process is controlled by scaling the output of the heat controller so that such output is representative of the percentage of the total heat available which should be supplied to the fractional distillation column to maintain a desired heat input to the fractional distillation column. The set point for the flow of both the heating fluid and the waste heat stream are then derived based on the output of the heat controller which allows control of heat input to the fractional distillation process and also provides a situation where the heat controller output may be linear which makes tuning the heat controller easier and improves stability of the heat controller.

Control of a fractional distillation process

In a fractional distillation process in which the designation of the primary product stream changes, the desired composition of the primary product stream and a secondary product stream are maintained without losing automatic control of the process for an extended period of time while the controllers controlling the process are retuned for the new operating conditions. Two sets of tuning constants are available to each controller and these tuning constants are automatically switched as required by the designation of the primary product stream.

Fractional distillation process control

A control system for distillation column with a sidedraw line is provided wherein a prediction on the influence by changes in the feed stream with respect to the sidedraw composition is made.

Control of sidedraw on distillation column

In a fractional distillation process in which the designation of the primary product stream changes, the desired composition of the primary product stream and a secondary product stream are maintained without loosing automatic control of the process for an extended period of time while the controllers controlling the process are retuned for the new operating conditions. Two sets of tuning constants are available to each controller and these tuning constants are automatically switched as required by the designation of the primary product stream.

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Bartlesville, OK, United States of America

Bruce A Jensen