Process flowsheet analysis of pervaporation-based hybrid processes in the production of ethyl tert-butyl ether
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The manufacturing process of ethyl tert-butyl ether (ETBE) involves the separation of ETBE, mixed C4 hydrocarbons and unreacted ethanol. Unfortunately, the unreacted ethanol forms azeotropic mixtures with ETBE that are difficult to separate by distillation. One of the alternative methods to overcome this limitation is the application of hybrid distillation–pervaporation processes with alcohol-selective membranes.
Simulation tasks were carried out with the process simulation software Aspen Plus and the results of alternative process flowsheets that result from the relative location of the separation technologies (for a target product purity) have been compared on the basis of the required membrane area and energy consumption. Thus, in the case study analyzed seven pervaporation modules located on a sidestream withdrawal, with a total membrane area of 210 m2, are required to obtain 6420 kg h−1 of ETBE with a purity of 95.2 wt%. The retentate stream is returned to the column while the permeate stream, with a high ethanol content, is recycled back to feed the reactors
Incorporating pervaporation modules in the process flowsheet for production of ETBE allows unloading of the main separation unit (debutanizer column), thereby reducing energy consumption and operating costs and increasing throughput.