Preheat control for a fractional distillation process

摘要

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.