초록
Nine redox potential-controlled operating conditions during ethanol fermentation were evaluated by means of a process simulator. Results show that the lowest unit production cost (0.764$/kg ethanol) was estimated for ~250gglucose/L among all studied conditions. Controlling the redox potential at -150mV increases the ethanol yield when glucose concentrations are greater than 250g/L; while no significant effects were observed at glucose feeds below 250g/L. For a facility with an annual production capacity of ~85-130millionkg ethanol, the shortest payout period of ~5.33 years was obtained under ~250gglucose/L conditions, either with or without redox potential control. If ~300gglucose/L is applied, controlling the redox potential at -150mV is required to limit the process payout period to be less than 6 years. Carbon dioxide disposal options are presented. Selling CO<SUB>2</SUB> as a byproduct can bring in 1.43million$/year income for an ethanol plant with a capacity of 100millionkg ethanol/year. Capture and transport of CO<SUB>2</SUB> to deep injection sites for geological underground storage is economically unprofitable and adds ~4.78million$/year in processing costs; however, this option results in a net removal of CO<SUB>2</SUB> from the atmosphere, making it environmentally preferable. The presented process model is available upon request.