Techno-economic and environmental evaluation of aldehyde-assisted chemical looping separation technology in coal-based and biomass-based ethylene glycol purification

Abstract

The application of aldehyde-assisted chemical looping separation technology in the separation of ethylene glycol (EG) and 1,2-butanediol (1,2-BDO) azeotropic mixture from coal-based and biomass-based crude ethylene glycol refining process can relax the operation conditions of the 1,2-BDO removal column and EG refining column, save energy, increase the yield of EG and guarantee the quality of EG product. Formaldehyde (FA), acetaldehyde (AA) and prolyl aldehyde (PA) are feasible reactants and assessment of the opportunities and challenges of different aldehyde-assisted processes before industrial application is necessary. In this paper, the mole composition of EG and 1,2-BDO in the distillate from the 1,2-BDO removal column was optimized. FA, AA, and PA-assisted chemical-looping separation processes (FA-ACLSP, AA-ACLSP and PA-ACLSP) were developed and simulated to provide fundamental data for the techno-economic and environmental evaluation. Results show that PA-ACLSP has significant economic and technical advantages (the yield of polyester-grade EG is 94.42% and the internal rate of return is 137.28%). However, it suffers from high potential environmental impacts (PEIs) and liquid discharge (the input and output PEIs and liquid discharge per kilogram of EG per hour are 4.87, 2.95 and 0.538). AA-ACLSP has zero liquid discharge and is truly environmentally friendly. FA-ACLSP faces a tough challenge in industrial application because of the large energy consumption and waste discharge (the internal rate of return is 4.63% and the liquid discharge per kilogram of EG per hour is 4.161). Finally, the discussion and analysis of different processes are illustrated to guide commercialization.