Optimal Shut-Down Policy for Air Separation Units in Integrated Steel Enterprises during a Blast Furnace Blow-Down

Optimal shut-down policy for air separation units (ASUs) in the oxygen distribution system is studied for the integrated steel enterprises with a captive oxygen plant during a blast furnace blow-down. A multiperiod mixed-integer linear programming (MILP) model was proposed, which includes the minimum time constraints for ASU shut-down and start-up and the zero vent constraint of gaseous oxygen. When the decision variables are scheduled simultaneously, such as the on/off states of the fixed-load compressors and ASUs, the rate of the variable-load compressors, and the rate of liquefaction units, the model can easily offer the on-site manager a solution to operate the facilities in the oxygen distribution system while avoiding oxygen venting and minimizing the pressure levels of the high-pressure network in the buffer system, thereby reducing the overall energy consumption for oxygen production. The applicability of the model was demonstrated and justified using a real-world case study.