Application Of Moisture Capacity On Granulation Process Of The Mixture In Sintering

Under the influence, such as the downturn of the global economic development and the slowdown of Chinese high growth of economic development, crude steel production in china will soon reach the saturation stage. To improve the competitiveness, domestic steel plants will pay more and more attention on the production quality and technical progress. As the biggest mass treatment of material and the highest energy consumption procedure, iron making process, especially the blast furnace process (BF) still has a great promotion potential in economic and technical benefit, via methods like improving operation level and the properties of charging burden into BF. Under the current BF burden structure in China, the quality of sinter ore plays a key role in the quality of BF production.Granulating effect of sinter raw materials determine the permeability of the sintering green bed and the homogenization of sinter reaction, thus has a great impact on efficiency, yield and quality of sintering process. As a typical hydrophilic feature between water and powders, moisture capacity shows an obvious impact on granulation process, whose testing curve reflects some important features during water absorption process, which determined the optimal moisture content of granules. It can make a significant meaning in theoretical study and practical application by doing some research on the effect of moisture capacity on improving granulation results of sinter mixture.The effect of moisture content on granulation results were studied under different ingredients. A predictive formula of the best moisture content in granulation was found. Relationship between raw material properties and granulation output was also discussed. Several conclusions were shown as follow:①within a certain range of moisture content, permeability of the green bed of granules will be improved by increasing moisture content of the blends. But when moisture content is greater than a threshold value, the permeability behaves dramatically worse. It means that there is an inverted type of"V"relationship between moisture content and permeability index JPU, at a broad range of moisture content. Similar phenomena were also got for mass fraction of 3-7mm after granulation and granulating efficiency.②When increase moisture content in mixture during granulation process, size composition in the granules group of mixture grows up even and centralized, due to that fine particles in mixture were gradually consumed, while the fraction of big particles increased. Optimal moisture content in this paper ranges from 6.5% to 7.3%, with a mass fraction bigger than 87.16% for size >3mm , a weight percent between 6.0% to 12.70% for size of 0.7mm～3mm and a little content of adhesion particles(<0.2%).③Fractal dimension of granules decrease linearly as the increase of moisture content. This means that the granule particle group turns out to be grown up, centralized and uniform. The adherent pelletizing index-GIO will reach a maximal value quickly by increasing water content, it seems that all mixtures in this paper show good result of GIO. Relationship between moisture content and bulk density of granules is a V type curve, the lowest bulk density for different mixtures ranges from 1.47～1.65g/cm3; Average particle size of granules increases as moisture content increases.④A linear relation between moisture content and moisture capacity was found, the correlation coefficient is bigger than 0.86, which show a significant correlation between them. Combined fractal dimension and properties of water absorption, a prediction expression for optimal moisture content is shown: The correlation coefficient R2 is bigger than 0.99, which indicated that besides chemical component, water absorption also has an influence on optimal moisture content.⑤Relationship between physical chemical properties and the best permeability index JPU of green granules bed can be illustrated by: 197.30 52.58 2 3(%) 1.04 ( )50.37 4.82 (%)23.92 (%)Its correlation coefficient R2 is greater than 0.97. The best permeability of green bed would be determined by the feature of particle size distribution (Df), chemical composition and water-absorbing properties.