The Inhibition On Pellets Sticking In COREX Shaft Furnace

COREX is a smelting reduction process using non-coke as the main fuel,reducing the dosage of coke,reducing the dependence on coke.During the operation of COREX process,many problems have been encountered,such as tuyere damage,charge sticking,low metallization degree,the gas flow back up,et al.In this case,the charge sticking of shaft furnace is one of the biggest problems in COREX process.Therefore,the study of inhibition of sticking of burden will provide the theory and technology supporting for solving the sticking phenomenon and it has great significance to promote COREX process.In this paper,COREX pellets were used to experiment under the reduction conditions simulating COREX atmosphere.The microstructure of the pellets was studied by means of X-ray fluorescence spectrometer(XRF),X-ray diffraction analysis(XRD),mineral microscopy,scanning electron microscopy(SEM)and energy dispersive spectrum(EDS).The behavior of the pellets sticking,the behavior of inhibiting sticking of the solid inhibitor were studied,and it illustrated the mechanism of sticking and the mechanism of inhibition.The sticking behavior and mechanism illustrated that with the increasing of temperature,the sticking index and metallization degree were increasing,it could conclude that temperature has dominated influence for sticking.The sticking mechanism of the pellets indicated that sticking index increased from 6.7% to 90.43%,and the metallization degree increased from 50.23% to 78.21% at 750?-950?.When the hydrogen was rich in the reducing atmosphere,the precipitated iron was dominated by layered iron.Sticking between pellets is a solid-phase sticking type in which metallic iron atoms permeate to each other by a diffusion mode in COREX shaft furnace.Continual precipitated iron migrates toward the surface of pellet in a diffusion,forming layer and whisker iron,and sticks tighter under higher temperature.The inhibition behavior and mechanism of pellets illustrated that coating is equivalent to form a dense layer of the “shell” structure on the pellet surface while inhibitor join in the form of coating.Particles diffuse between the iron atoms,reducing the precipitation of iron atoms,reducing the rate of diffusion of iron atoms.Ca O and Mg O forms sosoloid with iron,which changes the morphology of precipitated iron atoms,which effectively inhibit the growth of iron whiskers.Coating hinders the exchange of gas,reduce s the metallization degree of reduction pellets.The use of plastic mixed with light burned dolomite as coating,plastic combustion at high temperature,forming a "honeycomb structure shell" under the action of the formation of a large number of pores,increases the reaction contact area,reduces the influence of coating on the metallization degree.At 850?,The results show that the best is when the ratio of the them is 1:1,the metallization degree of the pellet is 60.19%,close to the metallization degre e is 61.10% of no coating pellets,and the sticking index descend 15.22% compared with no coated pellets.