| Copper resources in China commonly have low grade and complex compositions,and they are difficult to dress.Chalcopyrite ores containing talc,whose disseminated grain size is uneven,are particularly hard to separate.Talc and pyrrhotite contained in such ores are apt to be slimed after fine grinding so that flotation indexes of chalcopyrite are seriously affected.In this paper,the inherent reasons that kerosene and xanthate could be employed in the flotation and separation of chalcopyrite,talc,pyrite and pyrrhotite were explored by means of infrared spectroscopy(FTIR)and Atomic Force Microscopy(AFM).Then flotation kinetics analyses were firstly conducted on chalcopyrite,talc,pyrte and pyrrhotite to study the effects of reagent system and particle size on the flotation performances of the four minerals.On basis of these,it was the first time that simulation model of flotation kinetic was established by using the optimized neural network,and classification and differential speed flotation processes were put forward for such hard-dressing copper ores,which can provide theoretical foundation and technical support for efficient utilization of hard-dressing talcose copper ores.Results of single mineral flotation rate tests showed that in system of kerosene with a pH less than 8.3,chalcopyrite,talc,pyrite and pyrrhotite in coarse size fraction(between 0.074 and 0.109 mm)and medium size fraction(between 0.038 and 0.074 mm)were all floated at a relatively high speed simultaneously.When the four minerals above in fine fraction(less than 0.038 mm)and full size fraction(less than 0.109 mm)were floated within 1 min,phase K value of chalcopyrite was higher than those of the other three minerals,and phase K value of talc was the highest after flotation lasted for 1 min,and the recovery of chalcopyrite was close to that of talc after flotation lasted for 4.5 min.When the four minerals in fine size fraction were floated for 4.5 min with the amount of kerosene being 25.6 mg/L,total recoveries of chalcopyrite,talc,pyrite and pyrrhotite were 96.56%,87.38%,36.24%and 58.23%respectively.Under the system of xanthate,results of the single mineral flotation rate tests with CMC-Na,PAM,dextrin,SHMP and water glass alternately used showed that CMC-Na was the best depressor for flotation separation of talc and chalcopyrite,and floatability difference between chalcopyrite and talc was maximum when CaO was used to adjust pulp pH to 11.5.Under the system of xanthate with pH value of 11.5,phase K values of chalcopyrite,talc,pyrite and pyrrhotite in four different size fractions were all negatively correlated with the amount of CMC-Na and positively correlated with the amount of xanthate.When flotation lasted within 2.5 min,phase K value of chalcopyrite was much higher than those of the other three minerals.With flotation time increasing,phase K values of chalcopyrite in fine and full size fractions gradually decreased,and phase K values of chalcopyrite in coarse and medium size fractions firstly decreased rapidly and then tended to be stable after 2.5 min.However,phase K value of talc in each size fraction kept at a low value within 4.5 min of flotation.It was found by conducting differential speed flotation that floating difference of 79.97%between chalcopyrite and talc in coarse size fractions was relatively large when the amount of CMC-Na and xanthate were 4mg/L,20mg/L respectively and flotation time was 2.5 min.In medium size fractions,the floating difference of 76.56%between chalcopyrite and talc was relatively large when the amount of CMC-Na and xanthate were 8mg/L,20mg/L respectively and flotation time was 2.5 min.It was also found that floatability differences between chalcopyrite and talc in fine and full size fractions were relatively large when the amount of CMC-Na and xanthate were 32mg/L,80mg/L respectively and flotation time was 4.5 min.And in this case,floating difference between chalcopyrite and talc in fine and full size fractions were 46.72%and 70.04%,respectively.Floating difference between chalcopyrite and talc in fine size fraction was smaller than the differences in coarse,medium and full size fractions.According to analyses results of FTIR and AFM,under the system of xanthate,xanthate can be chemisorbed on the surface of chalcopyrite,pyrite,and pyrrhotite,and the amount of xanthate adsorbed on the surface of chalcopyrite is larger,while its adsorption quantities on the surface of pyrite and talc are smaller.Interaction between chalcopyrite and pyrite or pyrrhotite is relatively large,while interaction between chalcopyrite and talc is very small,so it is beneficial to the separation of chalcopyrite and talc under the system of xanthate.Under the system of kerosene,kerosene can be physically adsorbed on the surface of talc,chalcopyrite and pyrrhotite.And the amounts of kerosene adsorbed on the surface of chalcopyrite and talc are large,while its adsorption quantities on the surface of pyrite and pyrrhotite are small.Interaction between chalcopyrite and talc is very large,while interaction between chalcopyrite and pyrite or pyrrhotite is relatively small,so it is beneficial to the separation of chalcopyrite from pyrite and pyrrhotite under the system of kerosene.Flotation processes of chalcopyrite,talc,pyrite and pyrrhotite in coarse,medium and fine size fractions are all in accordance with the kinetic models of fractional speed flotation under different technological conditions.Kinetic simulation models of differential speed flotation for the minerals above in each size fraction were established using optimization algorithm of extremely learning machine based on genetic algorithm(or GA-ELM for short),achieving bidirectional prediction of reagent system and flotation kinetics equation.On the basis of GA-ELM flotation kinetic prediction model,calling range of this model was enlarged to[ε-Δε,ε+Δε].According to the law that flotation rate is changed by flotation reagent with a constant ratio,flotation kinetics curve and reagent dosages were calculated and simulated corresponding to the cumulative recovery rate under certain time to reduce the prediction errors avoiding the lack of data.By seeking difference minimum between flotation reagent amounts of two minerals in flotation separation,prediction models of kenitics for flotation separation of the two minerals were established,and the predicted reagent systems for flotation separation of chalcopyrite and talc were validated by the results of classification flotation tests.Results of flotation rate tests on artificially mixed ores showed that flotation separation of chalcopyrite-talc biphasic artificially mixed minerals in four size fractions could be achieved under the xanthate system by adopting the reagent system recommended by flotation kinetic prediction model.For chalcopyrite-talc biphasic artificially mixed minerals in coarse and medium size fractions,copper concentrates with copper grade of 33.51%and 33.72%respectively and cumulative recovery of 94.27%and 92.94%respectively were obtained after flotation lasted for 4 min.For biphasic artificially mixed minerals in fine and full size fractions,copper concentrates with copper grade of 27.66%and 28.63%respectively and cumulative recovery of 87.04%and 91.68%respectively were obtained after flotation lasted for 7 min.Compared with mixed minerals in fine and full fractions,flotation time of those in coarse and medium fractions were shorter and their separation results were better,which were consistent with the results of single mineral classification flotation.When flotation separation of chalcopyrite and talc were conducted mixed with pyrite and pyrrhotite under the recommended reagent system,copper concentrates with copper grade of 25.40%and 20.90%respectively and cumulative recovery of 59.23%and 63.07%respectively were obtained after chalcopyrite-talc-pyrite-pyrrhotite quaternary artificially mixed minerals in coarse and medium size fractions were floated for 7 min.Copper concentrates with copper grades below 15.30%were obtained after the above quaternary artificially mixed minerals in fine and full size fractions were floated for 7 min.It could be seen that the existence of pyrrhotite and pyrite made it impossible for flotation separation of chalcopyrite and talc in fine and full size fractions under a single system of xanthate or kerosene.Under the kerosene-xanthate mixed system,the quaternary artificially mixed minerals above in fine size fraction were subjected to flotation tests,and copper concentrates with a copper grade of 21.60%and a cumulative recovery of 78.65%were obtained,thereby achieving the effective separation of chalcopyrite from the other three minerals.Based on the studies above,classification and differential speed flotation tests are carried out on the refractory copper ores containing talc in Dongguashan of Tongling Nonferrous Metals Group Holdings Co.,Ltd,which were conducting closed-circuit flotation tests on copper ores with particle size greater than 0.038 mm under the xanthate system and on those less than 0.038 mm under kerosene-xanthate system respectively.And copper concentrates with a copper grade of 22.88%,yield of 3.65%and recovery of 84.21%could be obtained,thereby achieving flotation separation of such refractory copper ores.In this paper,simulation model of flotation kinetic(GA-ELM)and prediction model of mineral flotation kinetics were established based on flotation tests validation on single mineral and artificially mixed minerals.By combing simulation results of prediction model of mineral flotation kinetic with classification test researches on actual ores,classification and differential speed flotation process in which minerals in different size fractions should be treated under different reagent systems was proposed,which improved the stability of flotation separation process for refractory copper ores containing talc in Dongguashan,and provided a reference for flotation separation of relevant refractory chalcopyrite ores. |
PDF Full Text Request