Study On The Theory Related To Clarification Of Slurry With High Alumina Concentration In Sintering Process

Clarification of red mud slurry is an important part in production of alumina, and it is the key to find appropriate flocculants, which can accelerate separation process of red mud to increase the concentration of alumina in sintering process.Therefore,it is of value to develop new efficient flocculants for separating red mud from slurry. In addition, we study the course of clarification and flocculation mechanism in the high concentration alumina (Al2O3≥180g/L) slurry with mineral compositions, which contributes to optimization of clarification and will play a guiding role in synthesis and modification of efficient flocculants.Then, some contents as follows were studied.1.Modification of hydroxamated polyacrylamide and starch xanthateThe effects of temperature,time and addition of hydroxylamine hydrochloride on modification of hydroxamated polyacrylamide were studied. The results showed that modified hydroxamic polyacrylamide had a best performance in high concentration slurry when the reaction temperature is 85℃,time is 3h, and dosage is 15g/L.Modified starch xanthate did not make the high concentration alumina of sinter leaching slurry settled, but it performanted well in the high concentration alumina goethite slurry.2.Flocculation properties of pure mineral and its mixtureThe influences of temperature, concentration of alumina and solid content on clarification of pure mineral and its mixture from slurry were studied.The results showed that well effect of settlement could be obtained when we increased temperature, reduced solid content and alumina concentration. In the high alumina concentration slurry, the average settling rate of calcium titanate, dicalcium silicate, sodium aluminosilicate hydrate with high pressure, atmospheric sodium aluminosilicate hydrate and hydrogarnet slurry reached 9.8,9.6,9.3,9.land 8.3mm·min-1 respectively in the first 10min after adding flocculant C, while this flocculant didn't work on the goethite slurry. So the settling properties of pure mineral followed the order:calcium titanate> dicalcium silicate>sodium aluminosilicate hydrate with high pressure> atmospheric sodium aluminosilicate hydrate>hydrogarnet>goethite. Goethite is the main constraint of settlement in high alumina concentration slurry by sintering process.When the goethite content is less than 25% in the mixture, the other minerals can absorb by goethite and then co-flocculation.3.Flocculation mechanism of flocculants in the high concentration slurryThe flocculation mechanism was discussed based on the analysis of IR, Zeta potential and contact angle.The results showed that there exists an interaction physical adsorption or chemical adsorption between flocculants and the mineral particles in the high concentration slurry after adding flocculants.Meanwhile solid easily adsorbed more Flocculant C and the interface appeared fairly changeable in Zeta potential, angle contact and free energy of solid surface with addition of C instead of A or B.These facts imply that flocculation is mainly attributed to the adsorption of flocculants onto particles and forming flocs by bridge action in the concentrated solutions instead of the charge neutralization by sintering process.