STUDY OF GOLD AND SILVER RECOVERY PROCESS FROM HAIRY ORE PT. NUSA HALMAHERA MINERALS

• Main Author: DWIYAN WIJAYA (NIM : 12514062), GALIH
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/27443
• Institution: Institut Teknologi Bandung

PT. Nusa Halmahera Minerals (PT. NHM) uses fibre materials for strengthening activity using shotcrete in underground mining activity. During mining activity by blasting, parts of minerals and valuable metals within the ore are entrapped within the fibre material which are scattered with ore materials. The ore which is contaminated with fibre is called hairy ore and discharged from processing plant circuit in trash screen of SAG Mill cyclone underflow and Ball Mill cyclone underflow and subsequently stored in several stockpiles. The amount of hairy ore dumped in the stockpile increases from time to time as well as value of inventory gold in this hairy ore. In this research, physical separation of ore from fibre material in hairy ore by screening method using trommel screen and the influence of the presence of fine fibre in the ore on the cyanidation performance of gold and silver are studied. <br /> <br /> Sampling and preparation of hairy ore samples were carried out which consist of blending, mixing and splitting. The hairy ore sample characterization was conducted to determine the percentage of fiber and ore, bulk density, gold and silver grades in ore, moisture content in the sample, the distribution of the ore size in the sample, as well as the distribution of gold at various size fractions. The result of hairy ore characterization was used to estimate the amount of gold and silver contained in the material and to determine the design of the trommel screen for physical separation of ore and fibre. Physical separation by trommel screen was done by varying rotation speed, water flow, and separation time. The effect of fiber on the performance of gold and silver extractions in cyanidation process was evaluated by performing pulverized cyanidation test using 1000 ppm cyanide concentration for 48 hour. <br /> <br /> The screening analysis shows that the ore particle size of hairy ore is mostly (88.05%) in the range of 0.074 mm to 0.149 mm, while the remaining (11.95%) material size is less than 0.074 mm. Gold distribution in ore particles shows that gold particle is most dominantly (i.e. 40.2%) found in ore particle size distribution of 0.149 – 1.19 mm. Visual observations of screening products, indicated that the most appropriate screen size to separate the ore from the fiber in the hairy ore material is 8 mesh (2.38 mm). The best ore recovery of 75.9% was obtained from separation using trommel screen with rotational speed 25 rpm, flow rate of water injection of 13.2 liter/minute and separation time of 3 minutes. The cyanidation experiment shows that the presence of fine fiber lowered the dissolution kinetics of gold and silver but did not notably decrease total extraction of gold and silver after 48 hours (after cyanidation is finished).