Constructal design for an iron and steel production process based on the objectives of steel yield and useful energy

Abstract

An iron and steel production whole process (ISPWP) with coking, sintering, iron-making, steel-making, continuous casting and steel-rolling procedures is considered in the paper. A complex function (CF) composed of steel yield (SY), useful energy (UE) and maximum temperature difference (MTD) is chosen as the optimization objective. The chemical compositions of the sinter ore, hot metal and iron slag, raw material dosages, process temperatures, cooling water flow rates and total cost of the raw materials, fuels and power investments of the ISPWP in one year are taken as the constraints, respectively. Constructal optimization of the ISPWP is conducted with the help of constructal theory and finite time thermodynamic (FTT) theory. The maximum CF of the ISPWP, optimal cost distributions among the procedures (generalized optimal construct) and optimal parameters in the thermodynamic cycles are obtained. Some parameters, such as equivalent diameter of the sinter particle, sinter layer porosity and casting speed, on the optimization results of the ISPWP are analyzed. The results show that compared with the initial scheme, the CF, SY and UE after optimization are increased by 27.63%, 2.70% and 32.91%, and the MTDs of the slab and strip are decreased by 3.84% and 11.56%, respectively. Therefore, the generalized optimal construct of the ISPWP makes a slight increment of the SY, evident increment of the UE, slight decrement of the slab MTD and big decrement of the strip MTD, which realizes an evident performance improvement of the ISPWP. New design guidelines for the ISPWP are provided after optimizations, which enriches the generalized thermodynamic optimization theory for ISPWP.