Iron and steel manufacturing is considered a major contributor to the global carbon emission and energy-intensive industry. To sustainably produce iron and steel, various approaches have been explored to generate the needed power to support the production while mitigating the carbon dioxide emission. One of the viable approaches is the integration of a biomass-polygeneration system to produce biochar and other energy streams needed by the iron and steel manufacturing plant. A polygeneration system is composed of a combination of various existing technologies which seeks to recover wasted energy and to reuse by-products through process integration, thus, improving the overall thermodynamic efficiency of the system. In designing such complex systems, multiple objectives should be considered to assimilate the real-life requirements of the system. However, recent studies on the design of polygeneration system for iron and steel industry used a single-objective approached which may not consider the trade-offs between multi-objectives. Hence, this study proposes to design a biomass-based polygeneration system using a multi-objective approach employing fuzzy linear programming (FLP) model. The FLP model allows partial satisfaction of multi-objectives through the use of linear membership functions. A case study is presented involving biochar production from torrefaction, pyrolysis, and gasification together with power and heat production. The results indicate the optimal polygeneration process network consisting of a gas turbine for the generation of power, a heat recovery steam generator attached to the gas turbine for the heat generation, a gasifier for syngas, and torrefaction for biochar production. The developed model aims to aid engineers and managers in cost-effectively integrating a biomass-based polygeneration system in iron manufacturing.
