Research on Scheduling of Iron and Steel Scrap Steelmaking and Continuous Casting Process Aiming at Power Saving and Carbon Emissions Reducing

Abstract

Iron and steel scrap could substitute ironstone as the raw material for steelmaking and continuous casting (CC) production, and effectively reduce emissions of waste gas, water, and residue. The iron and steel scrap steelmaking and continuous casting (ISSSC) process is a compact production process involving scrap steel as a raw material, electric arc furnace, refining (RH/CAS/KIP/LF), and CC. Traditional scheduling of ISSSC has emphasized production performance indexes without considering energy and environmental factors. This study presents a new mathematical programming model for the scheduling of ISSSC that considers energy consumption with time-of-use electricity price and associated carbon emissions in addition to production performance indexes. The complexity of the multiobjective mixed-integer programming problem increases if the interval of the time-of-use electricity price is enlarged, the main and accessorial equipment is considered separately, and the flexible processing time is controllable. Under the linearization augmented Lagrangian relaxation framework, a solution methodology, based on controllable direction and a step surrogate subgradient Lagrangian algorithm, is developed according to the charge-based subproblem splitting policy. This solution could keep a smaller intersection angle between the gradient and the optimal direction, damping the zigzag, reducing the number of iterations, and ensuring the optimization efficiency for the scheduling of ISSSC. Numerical testing results show that the method generates high quality schedules in a timely fashion, while considering the time-of-use electricity price and associated carbon emissions.