Study On Size Change Of Unclassified Tailings Flocs And Its Thickening Performance

Developing paste technology is an important action for carrying out the concept of national "green mine".As the the foundation and primary link of the paste technology,unclassified tailings paste thickening is a complicated processing for paste,in the process,the low density tailings slurry and flocculant were mixed,then solid is separated from liquid through gravity and shearing.For researchs on unclassified paste thickening performance which is the relationship between solid flux,throughput and underflow concentration,the traditional gravity thickening theory has the bad adaptability,which cause many problems in actual engineering application.The size change of unclassified tailings flocs is the internal reasons for its compressibility and permeability which are relative with paste thickening performance.Studying on size change of unclassfied tailings flocs and its compressibility and permeability has important significance.The foes sturuture was regared as spherical.The parameters of the gel point and the compressive yield stress are to characterize the compressibility and the hindered settling is to characterize the permeability.Physical experiments,theoretical analyses and numerical calculation were carried out in trems of size change of flocs,dewaterability of flocs and paste thickening performance.The evolvement of the compressibility and permeability of tailings flocs in paste thickener with full pressure were studied.Finally the internal relations between size change of flocs and its compressibility and permeability under different shearing environment was illustrated.Efficient analysis of paste thickening performance was achieved.The research work could be summarized as follows:(1)The flocculant selection and optimization of settling experiments conditions were completed.The evaluating indicator of static settling performance was put forward.The flocculant which is suitable for the copper tailings from Xinjiang province was selected.A four-factor Box-Behnken design scheme was adopted to carry out the optimization of settling conditions.The effect of the factors including feeding concentration,flocculant dosage,concentration of flocculant slurry and feeding velocity on settling performance was analyzed.The predicating model of thickening perofomance factor was obtained.The best conditions of settling experiments were obtained based on response surface methodology:feeding mass concentration of 18.43%,flocuulant dosage of 19.57 g/t,flocculant slurry concentration of 0.04%,feeding velocity of 0.38m/s.(2)The change law of compressibility and peamebility of talings flocs in paste thickener with full pressure was investigated.Based on the mathematical model of settling and filtration behavior of flocs,the dymaical settling experiments and filtration experiments were carried out.The full pressure in paste thickener was stimulated under different shearing conditions.The influence law of rational speed on compressibility and permeability was investigated.The functions between the parameters of dewaterability and the underflow concentration were established under different shearing environment at steady-state conditon.(3)The size change of flocs under different shearing condtions was studied deeply.Shearing of rake cause the changes of foes,which make flocs densification.The scaled aggregate diameter was used to describe the densification extent of folcs and the aggregate diameter densification rate was used to describe the densification pace of flocs.Based on the characterization of settling velocity,the equations of foes densification with time were established.The effect of flocs size change on its compressibility and permeability was studied combining with parameters of dewaterability from steady-state condition.The time response evolution equations of compressibility and permeability of flocs was obtained.(4)A method for analyzing dynamic paste thickening performance was presented.Based on dimension of the paste thickener from a copper mine in Xinjiang province,the change law between solid flux,throughput and underflow concentration in the static thickening model were invesitgted combining C-C settlement and B-W dewatering theory.The time response evolution equations of compressibility and permeability of flocs were induced to produce the method to analyze dynamic thickening model,then the difference of thcikenng performance between static and dynamic paste thickening model was studied.(5)The recommended design process of paste thickening system was summarized.With the background of a paste backfill project,the design of relative parameters and the improvement of the dilution system were carried out.The validity of paste thickener model and research results were verified.Under the same underflow concentration,the average error between the actual and the theoretical value of mud pressure is 3.25%,the average theoretical throughput of thickener is 99.3 t/h,the average actual throughput of thickener is 102.0 t/h,which means the theoretical value is basically the same as the actual value.Last,the recommended design process of tailings paste thickening system was formed.