Abstract: The flow rate of a diluent fluid, such as steam, hydrogen or methane, to a cracking furnace is controlled so as to maintain a desired outlet velocity for the effluent flowing from the cracking furnace or to maintain a desired residence time for the feed stream in the cracking furnace. Feed forward control for the flow rate of the diluent fluid is provided by using an empirical model of the cracking furnace to predict either the outlet velocity or the residence time based on measured system parameters. Feedback control for the flow rate of the diluent fluid is provided by calculating the actual outlet velocity or actual residence time based on measured system parameters. The measured outlet velocity or residence time is utilized to bias or correct the predicted outlet velocity or residence time to provide a corrected prediction of the outlet or residence time.

Abstract: In a selective hydrogenation process wherein at least two catalyst beds in series are utilized, the temperature of the feed stream to the first catalyst bed and the temperature of the feed stream from the first catalyst bed to the second catalyst bed are manipulated so as to maintain a desired reaction temperature in both catalyst beds. The desired reaction temperature of the first catalyst bed is manipulated so as to insure that a desired percent of a specific feed component is selectively hydrogenated in the first catalyst bed. The reaction temperature of the second catalyst bed is manipulated so as to maintain a desired concentration of the specific feed component in the product stream from the second catalyst bed.

Abstract: The heat supplied to a cracking furnace is controlled so as to maintain a desired conversion rate for the material being cracked in the cracking furnace by comparing a prediction of the conversion rate for the material being cracked in the cracking furnace to a desired conversion rate for the material being cracked in the cracking furnace to thereby determine the heat required to maintain a desired conversion rate for the material being cracked in the cracking furnace. A measured conversion rate for the material being cracked in the cracking furnace is utilized to correct the predicted conversion rate as required. A signal representative of the heat required to maintain a desired conversion rate for the materal being cracking in the cracking furnace is utilized to manipulate the flow of fuel to the cracking furnace to thereby control the heat supplied to the cracking furnace.