Exploration of gradient energy-saving separation processes for ethylene glycol mixtures based on energy, exergy, environment, and economic analyses

Energy-saving separation processes for ethylene glycol (EG) were investigated. These processes were a basic separation process (BSP), a first-grade energy-saving process (FEP), and a secondary energy-saving process (SEP). The optimal operating parameters for each process were determined through multiple indicator analysis-based energy, exergy, environment, and economic performance. The energy analysis results indicated that the steam consumption of EG dehydration decreased from 12.21% to 0.64%, and the steam consumption of EG refined (EGR) decreased from 20.89% to 3.20%. Furthermore, the total steam consumption for the SEP was 30.49% lower than that of the BSP. The exergy analysis showed that the 50.69% exergy destruction and the 15.64% exergy loss recorded for the SEP were lower than those for BSP, which were 43.42% and 9.50% lower than for the FEP. Both the flow rate and cost of waste gas emissions for the SEP were reduced by 31.18%. The total annual cost (TAC), operating cost (OC), and equipment cost for the SEP were 2.95 × 106 $/y, 3.47 × 106 $/y and 4.06 × 106 $/y, respectively. The TAC and OC of the SEP process decreased by 11.20% and 13.16%, respectively, compared to the benchmarked BSP process. The novel SEP process shows high energy efficiency, low economic cost, and low exergy loss, and has great industrial application prospects compared to the benchmarked process.