| Restricted by technology,economy,etc,a large number of low-grade refractory gold ore and gold tailings resources are not made full use of.At present,using the conventional equipment to handle has been unable to realize the efficient utilization of low-grade gold ore.The high pressure grinding rolls(HPGR)technology based on the particle bed breakage principle can not only decrease the particle size,but also increase the dissociation of minerals,providing a convenient for subsequent processing,and has played an important role in realizing more crushing and less grinding in different minings at home and abroad.The domestic application research of HPGR,therefore,is still relatively lack in the field of gold mines,and the significance of research in this area is obvious.In this thesis,the low-grade gold ore from Zijinshan was taken for study.Crushing effect of conventional jaw crusher and HPGR with two kinds of roller surface pressure was compared,the features of crushing products and characteristics of cyanide leaching were studied.With the help of scanning electron microscope(SEM),stereo microscope(SM),reflective microscope(RM)and EDS energy spectrum analyzer,etc.,the influence mechanism of HPGR in material characteristics and gold leaching was studied furthermore.An idealized leaching kinetics model that based on effective micro-crack was established.Specific research contents and results were as follows:The results of study on the ore mineralogical showed that the gold grade is only 0.34 g/t with free gold proportion in raw ore that is easy for cyanide leaching.The other main metal minerals are limonite and pyrite.Vast majority of gangue minerals are quartz,as well as a small amount of dickite and alunite.The gold ore has been crushed by open circuit process of HPGR(roller surface pressure of 3.5 N/mm2 and 5.5 N/mm2)and conventional jaw crusher,and some characteristics of the crushed products,such as particle size characteristics,metal weight distribution,specific surface area,porosity and particle shape etc.,have been comparative researched.The results show that the product characteristics of HPGR are outshine that of jaw crusher except that the particle distribution of the whole product is wider and nonuniform.Full-slime,micro column and mini column cyanide leaching experiments of the-0.15 mm?-6.7+0.15 mm and +6.7 mm size classes products crushed by two different crushing methods have been studied.Results show that the gold leaching rate of products crushed by HPGR(roller surface pressure of 3.5 N/mm2)are greater than that of conventional jaw crusher which can be increased by 2.7,4.3 and 2.5 percentage points,then,the consumption of leaching agent were decreased by 9%,3.9%and 9.4%;leaching rate of products crushed by HPGR(roller surface pressure of 5.5 N/mm2)are greater than that of conventional jaw crusher which can be increased by 6.4,6.8 and 3.5 percentage points,then,the consumption of leaching agent were decreased by 10%,4.6%and 14.1%.Micro cracks of different classes and its impact on gold leaching were investigated.Studies show that HPGR can produce richer innergranular and intergranular micro-cracks through the quasi-static pressure,which contribute to the penetration of leaching reagents through the cracks and improvement of leaching rate.Accordingly,a leaching kinetics model was proposed based on the effective micro cracks.HPGR can significantly improve the gold leaching rate and reduce agent consumption.The research results of this thesis have been revealed the difference between the product characteristics and gold leachable of low-grade gold ore crushed by different crushing methods which could provide some theoretical guidance to the application of HPGR in gold field. |
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