Study On Relationship Between Properties And Effect Of Bentonite As Iron Ore Pellet Binder And Its Acting Mechanism

Bentonite is widely used as pellet binder in metallurgical industry. Using high efficient binder is one precondition for production of good quality pellet according to beneficiated burden materials policy for BF. Study on relationship between properties and effect and selecting high quality bentonite are very important for pellet production. In this paper, ten bentonites and three iron concenrates were involved to study on relationship between properties and effect of bentonite as iron ore peller binder. Then the relation of physicochemical properties and quality of green pellet was studied. The behavior of bentonite in green pellet was detected with ESEM. Based on analyses of the fracture modes of green pellet and the important physicochemical properties relating to the green pellet properties, an interpration for the mechanism of bentonite in the green pellet was made in this paper.Water adsorption(water adsorption speed), colloidal value, swelling value, relative viscosity and apparent zate-potential can be used to evaluate bentonite grossly. The bentonite with water adsorption up to 300%, colloidal value up to 100mL/(5g), swelling value up to 100mL/(5g), relative viscosity under 0.80 and apparent zate-potential up to-70mv have good properties.The drop number of green pellet added bentonite with high plastic viscosity suspension is bigger than the pellet with low plastic viscosity bentonite. The thixotropy of bentonite suspension is decreased obviously if there are divalent cations in the solution, because divalent cations bridge the smectite layers for large electrostatic attraction and as a result to decrease the house-of-cards structure. The apparent viscosity is obviously increased and the plastic viscosity is slightly increased, when there this univalent cations(K+, Na+)in the solution. Because the smectite quasicrystals are demixed by the univalent cations and as a result the number of quasicrystals is increased.The studies on mechanism of bentonnite in green pellet showed that drop number of green pellet depended on plasticity of pellet and viscous force of liquid in green pellet. The drop number reflects the shear resistance property of liquid bridge between solid particles. The wet compression strength reflects the tensile resistance property of liquid bridge between solid particles. Bentonite, fine particles in the iron concentrate and water forms colloid mater, which fill the gap between the iron concentrate particles as good bridge, after mixing the iron concentrate and bentonite. In bentonite colloid, the quasicrystals is dynamic and the house-of-cards structure is made from the quasicrystals by edge-to-face and edge-to-edge forms. The viscous force and shear resistance of liquid bridge was improved by gel structure of bentonnite colloid, so the drop number can be increased by adding bentonite. The viscosity and surface tension was improved by gel structure of bentonite colloid, so the capillary force is increased and therefore the wet compression strength is improved. The water vapor can transfer easily through the house-of-cards structure, and the water adsorbed by bentonite is evaporated later. Therefore, the crack temperature can be improved by adding bentonite into pelleting.