Abstract: A feedforward control system for a multiple-effect evaporator is provided wherein control is based on maintaining desired values for inferential variables of concentration and boiling point rise for a solution of a solid inorganic substance.

Abstract: Control of an isomerization process is based on a known relationship between the octane number and temperature of a reaction at equilibrium; and a predetermined relationship between octane number and temperature of the reaction product of a reactor using a specific catalyst. In use, measurements of actual octane number and temperature are compared with the octane number and temperature of a reaction at equilibrium to determine if the reaction is at equilibrium. If the reaction is not at equilibrium, a control signal is developed to restore equilibrium. Thus control of an isomerization process is accomplished so as to substantially maximize the efficiency of the isomerization process both from a production standpoint and from an energy usage standpoint by maintaining the isomerization reaction at desired equilibrium conditions. Also, for a dual reactor system, the differential temperature between the two reactors is manipulated so as to maintain more favorable isomerization conditions in the tail reactor.

Abstract: In an aromatic extraction process, the flow rate of aromatics to the extraction column is utilized to control the downstream stripping column so as to maintain a desired purity of the aromatic extract stream withdrawn from the stripping column. Also, the flow rate of solvent to the extraction column is manipulated so as to maintain a desired aromatic concentration in the raffinate stream withdrawn from the extraction column. This control, together with other interactive control functions, results in a control of the aromatic extraction process which substantially maximizes the profitability of the extraction process.