Improvement of Sinter Productivity and Qualities by Placing Low Slag Green Pellet at Lower Layer of Sinter Packed Bed

In order to blend PF (pellet feed) or concentrates for 20 mass% in sinter mixture and to displace coke fines or anthracite to biomass for 25 mass% in BAR (Bonding Agent Rate), sinter packed bed has been designed in ISIJ Research workshop. Outline of the design is shown as below. As designing, most important factor is permeability, and it has to be maintained even though fine materials as PF or concentrates is highly blended (20 mass%). For high permeability, GP [Green Pellet] granulated from fine materials, is placed in lower layer of raw materials packed bed. In the lower layer, mill scale and biomass char, which has characteristic of different oxidation or combustion temperature and rate compared to coke fine, are placed with coke fines for keeping high temperature (>1200°C), because GP needs longer sintering time due to large diameter. In addition, chemical composition of GP is low bacisity (1.5) and low CaO content for keeping its shape through restricting melt formation at sintering. Restricting melt formation has possibility of improving sinter quality (RI, RDI). In this study, Effect of the packed bed mentioned above on sinter performance and quality has been confirmed by sintering simulator which has performance of continuous charging and igniting with moving pallet car. The main results are shown as below. 1) Sintering speed and product yield are maintained at blending 20 mass% of PF. So, sinter productivity are also maintained. 2) Sinter reducibility (RI) has been improved in addition to maintaining sinter reduction disintegration index (RDI) because of low FeO and low SiO₂ content and restricting secondary hematite formation as mineral of sinter. 3) Remaining object is recovering sinter strength (TI) at the condition of low CaO content in sinter.