Abstract: A method for automated control of a petroleum distillation column in which signals representing temperatures, pressures and fluid flow rates for selected product streams withdrawn from the column are transmitted to a digital computer where, by means of a programmed algorithm, they are used to derive a true boiling point curve for the petroleum products of such product streams. The true boil point curve is then used to infer selected properties for the petroleum products which are compared with desired properties for the products of the monitored product streams and the differences between the inferred and desired properties are utilized to adjust automatically one or more of the operating parameters for the column so as to move the column's performance incrementally towards optimization.

Abstract: For parallel heat exchangers, one using a more preferred heat exchange medium as a heat exchange source and another using a less preferred heat exchange medium, maximum use of the more preferred heat exchange medium is used prior to use of the less preferred heat exchange medium in achieving a desired total heat exchange through the parallel heat exchange system. In employing such a heat exchange system in a cracking process it is combined with individual control of flows of feed fluid and diluent fluid to a plurality of individual cracking tubes in a cracking furnace to maintain a desired mass flow of feed fluid and ratio of mass diluent fluid to steam fluid to each such cracking tube.

Abstract: 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.

Abstract: For parallel heat exchangers, one using a more preferred heat exchange medium as a heat exchange source and another using a less preferred heat exchange medium, maximum use of the more preferred heat exchange medium is used prior to use of the less preferred heat exchange medium in achieving a desired total heat exchange through the parallel heat exchange system. In employing such a heat exchange system in a cracking process it is combined with individual control of flows of feed fluid and diluent fluid to a plurality of individual cracking tubes in a cracking furnace to maintain a desired mass flow of feed fluid and ratio of mass diluent fluid to steam fluid to each such cracking tube.

Abstract: An improved distillation process and apparatus are provided whereby liquid product recovery other than bottom product is maximized and feed stream heating is minimized. Inert gas streams combined with the feed stream and introduced into the distillation tower are controlled whereby feed stream heater residence time and partial pressures of feed stream components are minimized. The temperature of the combined inert gas-feed stream exiting the feed stream heater is controlled at a minimum temperature by establishing signals representative of overflash, bottom product specification and other conditions and comparing such signals whereby the signal which represents the lowest heater outlet temperature is utilized for controlling the heater operation.

Abstract: In an acid alkylation process wherein a fresh isobutane stream is combined with an olefin stream to form a combined isobutane olefin feed stream, a control system maintains a desired ratio of isobutane to olefin in the combined feed stream by manipulating the flow rate of the fresh isobutane stream. In addition, the controller automatically compensates for the effect of changes in the fresh isobutane feed stream by making equal changes in the flow rate of reactor effluent. Thus, the liquid level in the alkylation reactor is unaffected by changes made in the fresh isobutane stream to maintain the desired isobutane to olefin ratio.

Abstract: In an extrusion process, desired product quality parameters are maintained very accurately by manipulating the rotational speed of the screw associated with the extrusion process so as to maintain a desired ratio of feed rate to drag flow in the extrusion process and by manipulating the feed rate of the material to the extrusion process so as to maintain a desired energy input per unit of the material being processed.

Abstract: For parallel heat exchangers, one using a more preferred heat exchange medium as a heat exchange source and another using a less preferred heat exchange medium, maximum use of the more preferred heat exchange medium is used prior to use of the less preferred heat exchange medium in achieving a desired total heat exchange through the parallel heat exchange system. In employing such a heat exchange system in a cracking process it is combined with individual control of flows of feed fluid and diluent fluid to a plurality of individual cracking tubes in a cracking furnace to maintain a desired mass flow of feed fluid and ratio of mass diluent fluid to steam fluid to each such cracking tube.

Abstract: A multi-source feedstock distribution system is controlled by an optimization so as to substantially minimize the total cost of the feed while also meeting set points for flow rate and composition to feedstock users supplied by the multi-source feedstock distribution system.

Abstract: In a process in which a heating fluid supplied from a furnace is utilized to supply heat to a plurality of processes, method and apparatus is provided for substantially optimizing the operation of the heater by minimizing the amount of the heating fluid which is bypassed around the processes to which the heating fluid is supplied.

Abstract: In a process in which it is desired to provide P units of feed during a time period ending at time T and in which the available feed has been limited for a part of such time period, method and apparatus is provided for increasing the feed rate when additional feed becomes available so as to provide the total feed P to the process during such time period without subjecting the process to more rapid changes in feed rate than are necessary and without violating process constraints.

Abstract: In an ammonia manufacturing process, control of the hydrogen to nitrogen ratio for the feed to the ammonia synthesis reactor is accomplished by controlling the hydrogen to nitrogen ratio based on the ratio of hydrogen and carbon monoxide to nitrogen in the effluent withdrawn from the secondary reformer. Also, in an ammonia manufacturing process where parallel reformer trains are utilized, shifting of loading between the parallel reformer trains is accomplished using valve position control to override the control based on the ratio of hydrogen and carbon monoxide to nitrogen in the effluent withdrawn from the secondary reformer.

Abstract: In a process in which a first process variable is manipulated so as to maintain a second process variable substantially equal to a desired value for the second process variable, a set point for the first process variable is generated based on the difference between the actual value of the second process variable and the set point for the second process variable. The magnitude of the set point is determined by the probability that the second process variable may reach an undesirable value and thus control using the set point takes into the consideration the fact that large control actions may be required under some circumstances and minimal control actions may be required under other circumstances in a process.

Abstract: In a fractional distillation process in which a compressor is used to supply heat to the fractional distillation process, a plurality of signals representative of a plurality of speeds of the compressor, required to prevent various process constraints from being violated or maintain various desired process oprating conditions respectively, are compared. The signal representative of the highest compressor speed is utilized to control the compressor. In this manner, the compressor is run at the minimum speed required to satisfy the various process constraints and maintain the desired process operating conditions.

Abstract: In an ammonia manufacturing apparatus, control of the hydrogen to nitrogen ratio for the feed to the ammonia synthesis reactor is accomplished by controlling the hydrogen to nitrogen ratio based on the ratio of hydrogen and carbon monoxide to nitrogen in the effluent withdrawn from the secondary reformer. Also, in an ammonia manufacturing apparatus where parallel reformer trains are utilized, shifting of loading between the parallel reformer trains is accomplished using valve position control to override the control based on the ratio of hydrogen and carbon monoxide to nitrogen in the effluent withdrawn from the secondary reformer.

Abstract: An acid alkylation process is controlled so as to maintain a desired ratio of isobutane to olefins in a fluid stream flowing to the alkylation reactor and to maintain a desired acid to hydrocarbon ratio in the alkylation reactor. Also, if parallel alkylation reactors are utilized, the flow rate of the olefin stream to one of the alkylation reactors is manipulated so as to maintain a balanced loading on the parallel alkylation reactors. Such control results in improved quality of the alkylate produced and also improves the amount of alkylate produced from a particular amount of fluid to the alkylation reactor.

Abstract: In an alkylation process in which an acid regenerator is utilized to separate an acid catalyst from acid soluble oil contained in a spent acid catalyst stream, the heat input to the acid regenerator is manipulated based on the feed flow rate of the spent acid catalyst stream so as to maintain a substantially constant heat input per pound of feed flowing to the acid regenerator and the liquid level in the acid regenerator is manipulated so as to maintain the acid catalyst and acid soluble oil interface in the acid regenerator at a desired level. Such manipulation of the heat input to and the liquid level in the acid regenerator results in a substantially optimum separation of acid catalyst from acid soluble oil.

Abstract: In a catalytic cracking unit, the amount of the products removed from the fractionator associated with the catalytic cracking unit which has a boiling point above the highest boiling point of the desired product is calculated based on internal reflux to vapor ratios in various portions of the fractionator. The conversion of the catalytic cracking unit (the amount of the feed to the reactor having a boiling point above the highest boiling point of the desired product which is converted to a product having a boiling point below the highest boiling point of the desired product) is then determined and the reactor is controlled so as to maintain the actual conversion substantially equal to a desired conversion.

Abstract: Measurements of process variables associated with a cracking furnace are utilized to calculate the actual maximum tube skin temperature for the cracking furnace. The thus calculated actual maximum tube skin temperature is then utilized to derive a control signal which may be utilized to manipulate the rate at which heat is supplied to the cracking furnace. The accurate prediction of the actual tube skin temperature based on actual process measurements enables the conversion rate for the cracking furnace to be substantially maximized while preventing damage to the cracking tubes.

Abstract: In a fractional distillation process in which a compressor is used to supply heat to the fractional distillation process, a plurality of signals representative of a plurality of speeds of the compressor, required to prevent various process constraints from being violated or maintain various desired process operating conditions respectively, are compared. The signal representative of the highest compressor speed is utilized to control the compressor. In this manner, the compressor is run at the minimum speed required to satisfy the various process constraints and maintain the desired process operating conditions.