Plantwide control for TAME production using reactive distillation

The synthesis and control of a plantwide flowsheet to produce tert-amyl methyl ether (TAME) is reported. The flowsheet consists of a plug-flow reactor, one reactive distillation column, and two conventional distillation columns. The two conventional columns are needed for the recovery of excess methanol and the inert C5s. The columns are operated at different pressures to overcome separation limitations resulting from the presence of azeotropes. The reactive distillation is run with an excess of methanol because it is needed for both the reaction and the azeotropic vapor liquid equilibrium (VLE) requirements in the column. The reactive distillation column is the critical unit in this flowsheet that needs to be carefully controlled. An effective control structure is one in which a temperature in the stripping section and a methanol composition in the reactive zone are controlled. This control scheme is similar to that applied to other reactive distillation systems of the same type (that is, ETBE, MTBE). Because there is no reaction in the other two columns, they are effectively controlled by simple temperature controllers. The fresh feed of methanol must be manipulated to maintain the overall balance of methanol in the flowsheet. The proposed control structure is able to handle disturbances in feed rate and composition lip to +/-20%. (C) 2004 American Institute of Chemical Engineers.