This paper presents a process integration approach to analyze and evaluate usage of residual gases from coke oven, blast furnace and basic oxygen furnace in a primary steelmaking integrated with a carbon dioxide capturing and a polygeneration plant. Mathematical programming is applied to find the optimal operation of the integrated system for a given time horizon, where the polygeneration system produces methanol, electricity and district heat as by-products. As alternative technologies for steelmaking, blast furnace top gas recycling with three different integration scenarios for compressing and heating of the top gas and the blast have been studied. This includes an evaluation of the technical potential to enrich the oxygen content of the blast to full oxygen (i.e., nitrogen-free) injection operation. The results illustrate the optimal states and technologies under different external energy demands. Medium blast oxygen enrichment and top gas recycling with preheating for cold season and cold oxygen injection with preheated high top gas recycling rate is suggested for warm season.