Patent ID: 8795409
Filing Date: 2014-08-05
Classification: F25J,G05B

Abstract:
1. A method of controlling an air separation plant to optimize production of an argon product, said method comprising: continually executing a computer program programmed with models of each of a higher pressure column, a lower pressure column, an argon column, a condenser reboiler operatively associated with the higher pressure column and the lower pressure column and an argon reflux condenser connected to the argon column, the higher pressure column, the lower pressure column, the argon column, the condenser reboiler and the argon reflux condenser constituting components of the air separation plant; the models containing stage models of each stage of separation within each of the higher pressure column, the lower pressure column and the argon column, the condenser reboiler and the argon reflux condenser each consisting of a single stage model; the stage models connected to each other by internal vapor and liquid flows between the stage models and the models containing the stage models connected to each other by external vapor and liquid flows to and from the stage models that are situated at locations of feeds and draws to and from each of the higher pressure column, the lower pressure column and the argon column; during each execution of the computer program: calculating current values of controlled variables in response to manipulated variables by conducting a dynamic material balance, a vapor-liquid equilibrium calculation and an energy balance calculation for the stage models with the use of the internal and external vapor and liquid flows, the controlled variables comprising a nitrogen concentration within a crude argon feed stream fed from the lower pressure column to the argon column and an argon concentration within a waste nitrogen stream withdrawn from the lower pressure column and the manipulated variables comprising a set of flow rates of an air feed stream to the air separation plant, a product oxygen stream removed from the lower pressure column and the crude argon feed stream; and inputting the current values of the controlled variables calculated by the models into a controller and calculating, within the controller, the manipulated variables from the current values of the controlled variables that will result in the controlled variables having concentration values within targeted ranges, preset in the controller, that will maximize argon product yield of the argon product; and controlling the manipulated variables within the air separation plant to have the set of flow rates calculated by the controller.