The treatment of iron-bearing dusts and sludges by the rotary hearth furnace process has the advantage of sufficient utilization of valuable metals and a high impurity removal rate,but the lower strength of the metall...The treatment of iron-bearing dusts and sludges by the rotary hearth furnace process has the advantage of sufficient utilization of valuable metals and a high impurity removal rate,but the lower strength of the metallized product needs to be addressed.The effects of quaternary basicity R4(w(CaO+MgO)/w(SiO_(2)+Al_(2)O_(3)))on the reduction behavior and physical and chemical properties of metallized pellets,including phase composition,compressive strength,microstructure and soft melting area,were investigated with FactSage thermodynamic software and experiments.The strength of metallized pellets depended on the gangue composition,such as CaO,MgO,Al_(2)O_(3) and SiO_(2),due to the altered chemical composition,physical phase composition,microscopic morphology and stability of the slag phase.The reduction of carbon-bearing pellets was significantly promoted by suitable basicity.The lower basicity(R_(4)<1.4)facilitated the formation of low melting point iron-containing compounds from SiO_(2) and Al_(2)O_(3) with FeO,resulting in increased liquid phase generation,but lower metallization rate,due to the hindered precipitation and growth of iron grains.Interestingly,the higher basicity(R_(4)>1.8)also increased the amount of liquid phase and improved the strength of the pellets,due to the granular iron crystals bonded into sheets.Notably,the main component of the liquid phase in high-basicity conditions was calcium ferrite.Although the additional amount of liquid phase was beneficial to the strength of the metallized pellets,calcium disilicate was formed at R_(4)=1.6,resulting in a reduction in the compressive strength of the pellets to 1521.9 N/pellet.展开更多
The agglomeration of solid wastes is a key factor for subsequent utilization,while the difficulty in agglomeration and high cost have become common problems in the recycling process.The disk pelletizing process was ad...The agglomeration of solid wastes is a key factor for subsequent utilization,while the difficulty in agglomeration and high cost have become common problems in the recycling process.The disk pelletizing process was adopted,based on the optimization method by liquid binder addition,and the influence mechanism of the ratio of typical solid wastes as blast furnace dust(BFD)and sludge generated by oxygen converter gas recovery(OGS)was explored.Meanwhile,the effect of binder solution concentration on the quality of green pellets was studied.Derived from the contact angle detection and infrared spectrum analysis,the liquid bridge model was established to study the bonding mechanism.The results showed that OGS had stronger adsorption effect with binder,and the hydrophilicity of BFD was better.When the concentration of binder was higher than 0.2 wt.%,the contact angle between the binder and BFD was bigger than that with OGS,while the capillary force between particles reduced with larger contact angle.The increment in the binder concentration increased the viscous force between particles and the maximum separation distance.The ultimate drop strength and compressive strength were related to the type of viscous force,and the compressive strength reflected the strength of the force between particles intuitively,while the drop strength represented the comprehensive forces of green pellets.Reasonable combination of BFD and OGS was available for pelletizing process,while the ratio of BFD should not exceed 32.0%,and binder C was added in the form of solution with the addition amount of 0.4 wt.%,which can reduce the cost of binder by 20–30¥/t.展开更多
基金support from the Outstanding Youth Fund of Anhui Province(Grant No.2208085J19)the National Key Research and Development Program of China(Grant No.2022YFC3901405).
文摘The treatment of iron-bearing dusts and sludges by the rotary hearth furnace process has the advantage of sufficient utilization of valuable metals and a high impurity removal rate,but the lower strength of the metallized product needs to be addressed.The effects of quaternary basicity R4(w(CaO+MgO)/w(SiO_(2)+Al_(2)O_(3)))on the reduction behavior and physical and chemical properties of metallized pellets,including phase composition,compressive strength,microstructure and soft melting area,were investigated with FactSage thermodynamic software and experiments.The strength of metallized pellets depended on the gangue composition,such as CaO,MgO,Al_(2)O_(3) and SiO_(2),due to the altered chemical composition,physical phase composition,microscopic morphology and stability of the slag phase.The reduction of carbon-bearing pellets was significantly promoted by suitable basicity.The lower basicity(R_(4)<1.4)facilitated the formation of low melting point iron-containing compounds from SiO_(2) and Al_(2)O_(3) with FeO,resulting in increased liquid phase generation,but lower metallization rate,due to the hindered precipitation and growth of iron grains.Interestingly,the higher basicity(R_(4)>1.8)also increased the amount of liquid phase and improved the strength of the pellets,due to the granular iron crystals bonded into sheets.Notably,the main component of the liquid phase in high-basicity conditions was calcium ferrite.Although the additional amount of liquid phase was beneficial to the strength of the metallized pellets,calcium disilicate was formed at R_(4)=1.6,resulting in a reduction in the compressive strength of the pellets to 1521.9 N/pellet.
基金support from the Outstanding Youth Fund of Anhui Province(Grant No.2208085J19)the National Key Research and Development Program of China(Grant No.2022YFC3901405).
文摘The agglomeration of solid wastes is a key factor for subsequent utilization,while the difficulty in agglomeration and high cost have become common problems in the recycling process.The disk pelletizing process was adopted,based on the optimization method by liquid binder addition,and the influence mechanism of the ratio of typical solid wastes as blast furnace dust(BFD)and sludge generated by oxygen converter gas recovery(OGS)was explored.Meanwhile,the effect of binder solution concentration on the quality of green pellets was studied.Derived from the contact angle detection and infrared spectrum analysis,the liquid bridge model was established to study the bonding mechanism.The results showed that OGS had stronger adsorption effect with binder,and the hydrophilicity of BFD was better.When the concentration of binder was higher than 0.2 wt.%,the contact angle between the binder and BFD was bigger than that with OGS,while the capillary force between particles reduced with larger contact angle.The increment in the binder concentration increased the viscous force between particles and the maximum separation distance.The ultimate drop strength and compressive strength were related to the type of viscous force,and the compressive strength reflected the strength of the force between particles intuitively,while the drop strength represented the comprehensive forces of green pellets.Reasonable combination of BFD and OGS was available for pelletizing process,while the ratio of BFD should not exceed 32.0%,and binder C was added in the form of solution with the addition amount of 0.4 wt.%,which can reduce the cost of binder by 20–30¥/t.
