Simulation and Optimization of Distillation Processes for Separating a Close-Boiling Mixture of n-Butanol and Isobutanol

Abstract

Separation of close-boiling mixtures by conventional distillation consumes a large amount of energy because of the very high reflux ratio required. Mechanical vapor recompression heat pumps (MVRHPs) can recycle the energy of the vapor and can thus be used in such distillation processes to save energy. Three different distillation schemes, namely, conventional distillation, top MVRHP distillation, and bottom-flashing MVRHP distillation, were simulated for the separation of the closeboiling mixture of n-butanol and isobutanol using Aspen Plus to determine the economically best option. The research results indicate that, compared to conventional distillation, the energy savings for bottom-flashing MVRHP distillation and top MVRHP distillation can reach 67.92% and 72.92%, respectively, and the TACs correspondingly decrease by 71.74% and 75.57%.

Design and optimization of the separation process of acrylic acid and corresponding esters from aqueous solution of formaldehyde–a systematic procedure

“…A number of methods have emerged and been applied to the industry in the past few decades, but distillation is the most widely used . The advantages of distillation are a simple process, a wide range of applications, simple operation, and easy engineering.…”

“…Step 3: Separation Methods A number of methods have emerged and been applied to the industry in the past few decades, but distillation is the most widely used. [29][30][31] The advantages of distillation are a simple process, a wide range of applications, simple operation, and easy engineering. If the relative volatility of the separated components is less than 1.2, in order to reduce the energy consumption, distillation is generally replaced by other energy saving methods.…”

Simulation and optimization of different pressure thermally coupled distillation for separating a close-boiling mixture of n-butanol and iso-butanol

“…The simulation of distillation columns is based on the rigorous equilibrium stage module ''RadFrac'', which uses MESH equations, including material balance, vapor-liquid equilibrium, component summation and enthalpy balance equations for each stage, and the same tray type (sieve) and tray spacing are employed in every column. The Wilson model is employed to obtain indispensable vapor-liquid equilibrium data of the binary system in this work, and the effectiveness was demonstrated by previous studies [22,24].…”

“…In this section, in order to obtain optimal compression ratio, the influence of compression ratio on the heat transfer temperature difference (DT) and compressor duty (Q comp ) is estimated, respectively. Generally, DT refers to the difference between the outflow temperature of compressor and the bottom liquid stream temperature of column, and it should not be lower than the minimum heat transfer temperature difference (DT min = 10°C) [20,22]. However, when the DT is equal to or larger than the lower limit of temperature difference, the temperature difference of heat exchanger between two outlet fluids may be small or even less than zero, which will lead to considerable heat transfer area or abnormal operation.…”

“…Generally, because the boiling points of n-butanol and iso-butanol are very close, a large amount of energy is consumed to separate them by conventional distillation. To reduce energy consumption in the separation of this close-boiling mixture, Gao et al [22] investigated three different distillation schemes, namely conventional distillation, top mechanical vapor recompression heat pumps (MVRHP) distillation, and bottom-flashing MVRHP distillation, and the two innovative processes can achieve about 70% reduction in both energy requirement and TAC compared with the conventional distillation. Besides, top MVRHP distillation was demonstrated the most economical option.…”