Impact of water washing precipitator dust on the particulate composition and dioxins in sintering flue gas

Sintering is an important process for the smelting of iron and steel for ironmaking in a blast furnace. However, the sintering process emits air pollutants in the sintering flue gas, especially fine particles and dioxins. In order to study the effects of sintering with precipitator dust on the composition of particulate matter and dioxins in the sintering flue gas, the precipitator dust was purified by a water washing method. The influence of sintering with the precipitator dust before and after the purifying modification was determined by a sintering cup experiment. The flue gas pollutants were then collected by the impact particle sampler and dioxin sampler and the alkali content, heavy metal content and dioxin precursor emissions were determined. The experimental results indicate that potassium (K) and chlorine (Cl) in the precipitator dust are effectively removed by the water washing method. The sintering with the purifying modification and precipitator dust improve the particle size distribution of the sinter and reduce the concentration of particulates and dioxins that are emitted in the flue gas. The K content is higher in the sintered particles, especially the smaller ones, compared to sodium (Na), lead (Pb), and zinc (Zn). Sintering with the precipitator dust after washing significantly reduces the K content of the sinter burden proportion and causes the notable reduction of K in the flue gas particles, particularly in the particle size range of 1.10-2.10 μm. The Cl in the sintering raw material, along with the chlorobenzene and polychlorinated biphenyls that are generated in the sintering process, cause the generation of the dioxins. The sintering with the precipitator dust after washing effectively reduces the content of Cl. The emission of polychlorinated biphenyls is also reduced to 40%, which is beneficial in reducing the concentration of dioxins.