Operation scheduling optimization of gas–steam–power conversion systems in iron and steel enterprises

•A model considering the start–stop state of the equipment is established.•Relationship between boiler heat efficiency and operating load is considered.•The influence of initial state of equipment on optimization results is investigated.•The total cost can be reduced by 5.20% compared to the unoptimized system. Iron and steel enterprises exhibit the characteristics of a large amount of energy conversion equipment, many different energy media, and frequent changes in energy supply and demand. Nonetheless, the actual production process involves multiple working conditions that affect the efficiency of energy conversion equipment and can cause unnecessary start–stop behavior. This significantly impacts the energy consumption and operating cost. Therefore, in this study, an optimal operation scheduling model for gas–steam–power conversion systems was established in integrated iron and steel enterprises, considering the minimum energy operating cost and the energy conversion equipment start-up and shut-down cost as the objective functions. The results of single objective optimization, focusing only on energy operation cost, show that the gasholder can play a storage role and the total operating cost of the system can be reduced by 4.70% compared with an unoptimized system. In a multi-objective optimization considering both the energy operating cost and the start–stop cost of energy conversion equipment, only seven input devices are needed to meet the energy demand (with 1# 35 t boiler shut down). Boiler heat efficiency compares favorably with that of the single objective optimization, and the total cost can be reduced by 5.20% compared with the unoptimized system. These results provide guidance for steel and iron enterprises to improve their equipment efficiency and reduce energy costs.