Exploration of Straw Fiber as Reducing Agent Utilization in Rotary Hearth Furnace Process for Direct Reduced Iron Production

Straw fiber is a waste obtained by jet milling after extracting valuable substances form corn straw through steam explosion-washing-mechanical carding process. At the same time, it is also a clean and renewable reducing agent. In this study, physical and chemical characteristics of straw fiber were investigated firstly. The usage of straw fiber in rotary hearth furnace process for direct reduced iron production was then discussed. The results show that on one hand, fixed carbon content in straw fiber is low, which is unfavorable for the productivity of direct reduced iron; on the other hand, ash and sulfur content is also low, which improves the quality of direct reduced iron. Besides, the fibrous structure is conducive to improving the pelletizing performance of carbon-containing pellets, thus reducing an additional amount of binder. Compared with common reducing agents, straw fiber provides better reduction effect, and straw fiber carbon-containing pellets possess higher compressive strength and larger volumetric shrinkage, which is beneficial to increase the thickness of the whole material layer in rotary hearth furnace. In addition, these carbon-containing pellets also have advantages of lowering C/O ratio and shortening reduction time. The appropriate C/O and reduction time are 0.8 and 15 min, respectively, and the particle size of straw fiber below 0.15 mm has better reduction effect. This study aims to provide theoretical and technical basis for the utilization of straw fiber in rotary hearth furnace process.