(1257) Behaviour of Low-Grade Carbonaceous Reductants in the Reduction of Dust-Carbon Composite Agglomerates: A Mathematical Modeling Approach

摘要

Recycling of iron-bearing wastes using a rotary hearth furnace (RHF) has gained considerable attention in the past two decades as a steel production technology with reduced environmental impact. Coal-based dust reduction in the form of a dust-carbon composite pellet has been successfully practiced. Application of low-grade carbonaceous materials, such as waste plastics and high-volatile coals, as reductants would further enhance the sustainability of the RHF process, which would lead to steel manufacturing from secondary source materials. Several researchers have also reported that the reduction of iron oxide-based pellets can be accelerated with the addition of plastics. However, the utilization of low-grade reductants has been proved to be a demanding task due to the unpredictability of their influence on the reaction behaviour of the dust-carbon composite pellet. A significant volume of volatile matter contained in the reductant is released within the pellet during the heating. The released gases affect both the reduction behaviour of iron oxide and the pressure increase in the pellet that in turn influences the pellet strength. As a low-cost and versatile approach to the development and optimization for the simultaneous value recovery from dust and carbonaceous wastes, a mathematical model was developed. The model simulates the behaviour of dust-carbon composites during the reduction process in RHFs by taking into consideration the reactions of iron oxide reduction and carbon gasification as well as heat/mass transfer. The model was validated with experimental results and can be utilized as a process design tool for recycling dust-carbon composite agglomerates with RHFs. Some calculation outputs and findings specific to the impact of low-grade carbonaceous reductants on dust-related reactions will be presented.