Study On Separation Behavior Of Diasporic Low-grade Bauxite In Cyclonic Field

Bauxite is the main raw material to produce alumina, whose mineralogical characteristic and processing technology affect its general utilization directly. Diasporic bauxite is the major kind in China, charactered by high-aluminum, high-silicon, low ratio of Al2O3 to SiO2, complicated mineral compositions and nearly disseminated associations of aluminous minerals and silicate minerals. These lead to a high production cost and a poor product quality in alumina industry. It’s an important research project to carry out economical and effective beneficiation to desilicate from diasporic low-grade bauxite with great reserves in China and then provide excellent material for alumina production.With diasporic bauxite of A/S 4.39 as samples, the influence of different factors on its cyclonic separation and cyclonic-reverse flotation was studied systemically, and numerical simulation of fluent field in cyclone was carried out in the condition of many factors, according to which the mechanism of structural and operating parameters influence the cyclonic separation of bauxite was analysed. The main work in the present paper includes the following:(1) The influence of apex diameter and feed pressure under different cone angles on the cyclonic separation effect of bauxite was investigated systemically. The results showed the increase of apex diameter can reduce the flow ratio of overflow, particles in overflow becomes finer and the A/S of overflow decreases, and the A/S of underflow also decreases, the recovery of Al2O3 in underflow increases; Cone angle and apex diameter have interaction in classification efficiency; When the feed pressure increases under different cone angles, the flow ratio of overflow keeps invariable basically, but the classification efficiency decrease in different degree, particles in overflow becomes finer, the function of classification was weakened; Feed pressure and cone angle have interaction in cyclonic separation of bauxite, in the condition of special cone angle, the function of separation is strengthened; The increase of cone angle can also increase the flow ratio of overflow, the solid ratio of overflow can be increased accordingly. When cone angle is 11°, apex diameter is 6mm, and feed pressure is 0.4MPa, better separation indexes are obtained:The A/S of underflow is 7.33, the recovery of Al2O3 in underflow is 70.52%; the A/S of overflow is 2.30 and the recovery of SiO2 in overflow is 57.14%.(2) The influence of feed concentration, feed particle size and dispersant dosage on the cyclonic separation effect of bauxite was investigated. The results showed that the increase of feed concentration is disadvantageous to the process of cyclonic separation, it makes the separation indexes worsen obviously especially in the range of 10%～20%; Bigger particle size of bauxite is more advantageous to improve its cyclonic separation indexes, namely-0.074mm 60%; The separation environment and selectivity can be improved obviously by adding dispersant with suitable quantity.(3) The tests of desliming-cyclonic separation showed that in the condition of little cone angle and big apex diameter, feed pressure of 0.3～0.4MPa is suitable to deslime from bauxite; By desliming in hydrocyclone of 7°and separation in hydrocyclone of 11°, the A/S of concentrate is 7.54, the recovery of Al2O3 in it is 71.11%, the indexes are improved than those by cyclonic separation without desliming.(4) The influence of aeration quantity, flotation reagents and feed particle size on the effect of cyclonic-reverse flotation of bauxite was investigated systemically. The results showed that the aeration quantity have some influence on the fluent field and separation effect of mineral particles, when the aeration quantity increases in the range of 0～0.8m3/h, the envelope of zero vertical velocity shrinks to the axis slightly, the classification function is weakened, but the separation function is strengthened, the separation indexes are improved than no aeration; By adding some modified starch and laurylamine acetate, the separation indexes are better than those obtained by cyclonic separation in the same condition of structural and operating parameters; Feed particle size has remarkable influence on the separation indexes of cyclonic-reverse flotation,-0.074mm 60% is also suitable.(5) Numerical simulation of fluent field in cyclone was carried out in the condition of many factors, according to which the mechanism of different factors influence the cyclonic separation of bauxite was analysed. The results showed that structural parameters make the envelope of zero vertical velocity changed, make flow ratio of overflow to underflow accordingly, and the separation behavior of mineral particles changed. However, they have basically no influence on the velocity distribution in the effective separation district, which accords with the inference according to the test results of cyclonic separation; Because the distribution of pressure in different cone angles change finely with apex diameter, which makes the force, motion behavior and distribution characteristics of particles changed in radial, and so the interaction of cone angle and apex diameter on the classification effect of bauxite appears; When the structural parameters is certain, the increase of feed pressure has no obvious influence on the envelope of zero vertical velocity, but can increase the vertical and tangential velocity in the effective separation district, and can change the force and distribution characteristics of particles in the radial of hydrocyclone, finally makes the separation effect of mineral particles improved.