Simulation and Process Integration of Clean Acetone Plant

Abstract

Acetone is produced worldwide by cumene hydroperoxide process. Alternatively, free of aromatic compounds acetone is obtained by isopropyl alcohol (IPA) dehydrogenation. The feedstock is azeotropic mixture IPA-water (Luyben, 2011). This contribution aims to evaluate process feasibility both in terms of reaction engineering and separation by distillation. Rational use of energy is based on process integration A process flowsheet with better performance is proposed. The dehydrogenation reaction is endothermic with number of moles increase. Higher temperature and decreased IPA partial pressure using inert (water) are favourable. Reaction kinetics in vapour phase is simulated in Aspen HYSYS ® with LangmuirHinshelwood-Hougen-Watson (LHHW) model, considering both direct reaction and reverse reaction terms, based on experimental data (Lokras, 1970). Such more realistic model is not considered in other papers (Luyben, 2011). The chemical reactor is simulated as an ideal CSTR. High volatile and non-condensable compounds from the cooled reactor effluent are separated into a flash unit. To minimize the loss of acetone in gas stream, an absorption column with water is considered. Possible separation schemes for liquid effluent (consisting of acetone, IPA and water) are evaluated with residual curves maps (RCM) built in SIMULIS ® ver.1.3. This system has IPA-water azeotrope, a saddle node. The boundary, separes two distillation regions. Both direct and reverse separation schemes are possible. Two distillation columns are used to separate the components of flash unit bottom stream product and absorbtion column bottom stream product. As designed by RCM, for direct scheme, acetone separates in first column top product, and IPA-water azeotropic mixture separates as second column top product. This is recycled to meet plant feedstock stream. Water separated as second column bottom stream product is partly recycled, after cooling, to the absorption column. To minimise utilities consumption and to synthesize process heat exchangers network (HEN), maximum energy recovery (MER) methodology is used with SPRINT © software. The proposed HEN is included in process flowsheet. Energy saving is 35 % for hot utilities and 37 % for cold utilities, compared to non-integrated scheme.