The Selinsing Gold processing plant conversion includes adding a flotation and a BIOX® leaching circuit (Selinsing Sulphide Gold Project”) based on the 2019 feasibility study.
The 2019 feasibility study (or “FS”) includes the Selinsing deposit and the adjacent Felda and Buffalo Reef deposits. It established the economic viability of the project for a six-year mine life through the extension of the existing oxide plant to incorporate additional sulphide ore extraction. The economic viability of the project described in the FS is primarily driven by adding the flotation and BIOX® processes to the current Selinsing gold processing Plant to treat sulphide ore.
Sulphide Processing Plant Conversion
The Sulphide Processing plant conversion includes plant expansion by adding a flotation plant, a BIOX® plant, other upgrades to the existing facilities, new power lines and mining development such as river diversion, expansion of tailing storage facilities and wall push backs at the current open pits. The BIOX® Process is a patented technology for pre-treatment of sulphide-based refractory ores and concentrates ahead of a conventional cyanide leach for gold recovery.
Inferred Resource Potential Opportunity
The opportunity to include Inferred Resources totaling 150koz was also discussed in the FS. The Inferred Mineral Resource inside the Reserve open pit designs potentially contains an additional 20koz of gold. The Inferred Mineral Resource external to the open pit design contains 130koz of gold. Further exploration programs could be initiated to target the conversion of Inferred Mineral Resources to Indicated Mineral Resources. The Selinsing Gold Mine has a proven record in converting oxide Inferred Mineral Resources to recovered ounces.
The diagram below shows conceptual flotation and BIOX® circuits added to the gold recovery process.
Selinsing Sulphide Project Construction Strategy
In order to reduce the initial capital investment, the Company plans to develop the Selinsing Sulphide Project through a two stage de-risking process: Stage 1 construction of a flotation plant that was originally designed to deliver sulphide gold concentrates as a semi product for further BIOX® leaching process. Under the new approach, the flotation plant will be modified to produce higher grade saleable gold concentrates, the cash generated from which may be used to fund construction of the BIOX® leaching plant.
The stage 1 flotation plant has been constructed and is ramping up to commercial production. The stage 2 construction of the BIOX® leaching plant is pending success of developing a niche market that may supply suitable sulphide gold concentrates to be toll treated through the Selinsing sulphide treatment plant, therefore underpin sustainable long-term cash flow to the Company. The expected construction timeframe for stage 2 is 12 months. The expanded plant can be converted back to process oxide ore at any time from the sulphide processing plant.
The Selinsing Gold Sulphide Flotation Plant
Monument constructed a new sulphide processing plant at the Selinsing Gold Mine with a designed capacity of 950,000tpa that consists of rougher and cleaner flotation, concentrate thickener, water recovery thickener, reagents storage and mixing and concentrate filtration. The processing plant was completed and is continuing the ramp up process to full commercial production. The detailed engineering design was done by Mincore (Australia) Pte. Ltd and the main contractor for the project was Seong Henng Engineering Works Sdn Bhd, who played a major role in previous construction phases at Selinsing.
The existing plant crushing circuit, milling circuit, gravity separation circuit and classification circuit will remain from the previous CIL plant operation. The conversion from current CIL operation to sulphide flotation will allow the Selinsing Gold Mine to continue processing the refractory sulphide gold ore and produce a saleable gold concentrate product.
The sulphide flotation plant comprises a trash screen, two conditioning tanks and six rougher tank cells followed by three stages of cleaner flotation. The flotation cells were manufactured by BGRIMM Machinery and Automation Technology Co Ltd of China. Various reagents will be added during the flotation process: soda ash as pH modifier, sodium sulphide as sulphidiser, copper sulphate as activator, carboxymethyl cellulose (CMC) as slimes depressant, potassium amyl xanthate (PAX) as collector and methyl isobutyl carbinol (MIBC) as frother.
Final flotation concentrate is transferred to a 9m diameter concentrate thickener from which thickened slurry is pumped to the concentrate filtration plant. Final flotation tailings are transferred to a 14m diameter water recovery thickener and thickened slurry is pumped to the tailings storage facility (TSF) while the supernatant water overflows to the process water tank. Both thickeners were manufactured by Metso Outotec Australia Ltd.
The thickened slurry is stored in a concentrate storage tank prior being pumped to the concentrate filter press. The concentrate filter removes 85% to 90% of the water from the thickened slurry to produce gold concentrate cake that has moisture content of 10% to 15%. The filter press was manufactured by McLanahan Corporation Pty Ltd.
The gold concentrate produced will be transported by tipper truck, shipping container or in bulk bags to the loading port and subsequently shipped to the destination port depending on the concentrate buyer.