Dust recycle screws

Overview

Steelworks recycle iron oxide (excess dust) generated during the steelmaking and rolling processes as reduction pellets. Previously, excess dust (approximately 300,000 MT per year) was disposed of through landfilling or sold to external parties. As the surplus dust contains high levels of zinc, it had not been used in blast furnaces because zinc deposits would form inside the furnace, hindering its operation. Consequently, a method was developed to remove the zinc from the high-zinc steelmaking dust (300,000 MT) through a reduction reaction within a rotary hearth furnace, thereby enabling its reuse in blast furnaces. The process in the rotary hearth furnace involves pellet feeding → heating → reduction using carbon (to remove zinc and CO gas) → discharge → cooling → transport to the blast furnace. The discharged pellets are transported to the blast furnace via a screw conveyor.