Improving Binary Distillation Column Design and Operation Using Exergy Analysis
This study developed methodologies that would improve the design and operation of distillation column by reducing the irreversibility within the column and improving the column efficiency. This was with a view to minimize the consumption of energy in distillation processes. Two binary systems benzene-toluene and methanol-water were considered for this research. The performance parameters for these systems were obtained from McCabe Thiele and 'Ponchon-Savarit methods of designing distillation columns in chemical engineering. The systems were simulated using process simulator software HYSYS with capabilities for generating the thermodynamic and physical data of the components. Different variations were made for the design and simulation of the column. Exergy analysis of the data was carried out using a program developed and written in C++ language. The enthalpy versus exergy factor graph and the temperature versus exergy graph were used to identify the best operating and design variables. Also the total cost (energy and capital) was used to identify the best design variables. Efficiencies and irreversibility calculations were made for each of the design and simulation variation. The results showed that the optimum operating feed temperature for the systems were 95°C and 79°C for benzene-toluene and methanol-water systems respectively. Feed rate of the systems were 260kmol/hr and 84.4kmol/hr for benzene-toluene and methanol water systems respectively and column pressure for the systems was l atm as against feed rate of 350kmol/hr for benzene-toluene system and feed temperature of 53°C for methanol-water system. Also optimum reflux ratio for the systems was 2 for benzenexv toluene and 1.5 for methanol-water from the thermodynamic diagrams as well as from the cost analysis method. It can be concluded that the developed methodologies could be used to know the optimum operating conditions for a distillation column and the methodologies were found to be useful tools in the design and operation of energy efficient distillation column.