Control of zinc-containing dust agglomerates in basic oxygen furnace flue gas cleaning system

Abstract

Basic oxygen furnace (BOF) flue gas cleaning system is a crucial flue gas purification device to ensure the cleaner production in steelmaking process. Due to utilization of galvanized steel scrap in steelmaking process, zinc-containing dust collected by the cleaning system forms unremovable high-strength dust agglomerates on the inner wall of evaporative cooler, which can affect the normal operation of cleaning system and seriously hinder the cleaner production in steelmaking process. This issue continuously aggravates as the use of galvanized steel scrap increases, while there are currently no effective control methods. Consequently, how to keep down the zinc-containing dust agglomeration strengthening in the evaporative cooler is a crucial issue for investigation. In this paper, X-ray fluorescence spectrometer, X-ray diffraction, scanning electron microscopy and strength test under high-temperature roasting were carried out to investigate characteristics and strengthening mechanism of dust agglomerates. Based on this, easy implementation of control methods were proposed. The results show that ZnO reacts with Fe2O3 at a high temperature above 600°C to form tightly ZnFe2O4 phase, and chemical adsorption of ZnFe2O4 with BOF dust particles is the primary cause of dust agglomeration strengthening in evaporative coolers. Solid state sintering of low melting point substances containing Na+ and K+ promotes strengthening. Decreasing the temperature in evaporative cooler and controlling the content of low melting point substances in BOF dust are effective measures to reduce dust agglomerates, optimize the environment of cleaning system, and ensure the cleaner production in steelmaking process.