ABSTRACT
Today the roller screen has a wide range of applications in the steel making industry. The roller screen will be used for screening of green pellets before kiln. Since the appropriate size of green pellet is -16+9mm, there are different gaps between rollers that make green pellets classified to three categories such as -9mm (undersize), -16+9mm (onsize) and +16mm (oversize). The efficiency of roller screen will be specified according to the weight percent of undersize in onsize as a fine material and weight percent of onsize in oversize (loss). This efficiency will be influenced by different operational parameters such as roller diameter, roller speed, and roller gap, material type of rollers and inclination of roller screen. This study investigates the effect of different material types of rollers in efficiency of Ardakan roller screens, located in Yazd province of Iran. The rollers of the existing roller screens in this pelletizing plant are made of polyurethane which in accordance to this investigation, has a maximum lifetime of about 6 months. Operating the polyurethane rollers beyond its lifetime generates serious problems such as high wear of rollers, and consequently, material buildup on the roller surface which then significantly decreases the roller screen efficiency. So, after examination of different roller materials, stainless steel 304 with higher surface roughness that will help pellets move properly on the roller screen surface was selected as a solution for this problem. So the new roller screen was constructed by Fakoor Meghnatis Spadana (FMS) Company and was replaced by previous one. In this condition, the maximum capacity of roller screen was increased about 17% and the roller screen efficiency was increased about 15%.
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