Tin miner Alphamin Resources Corporation has completed the front-end engineering design (Feed) and control budget estimate (CBE) for its Democratic Republic of Congo- (DRC-) based Bisie tin project, in which it has an 80.75% stake.

The miner says the completion of the Feed programme and associated CBE confirms the robust economic metrics and potential of the project, as well as its development into the North Kivu region’s first commercial mine.

Alphamin CEO Boris Kamstra says the completion of the Feed and CBE phase marks another important and exciting milestone as Alphamin advances the project.

A comprehensive process for estimating capital costs was followed and the CBE results indicate that the project has the potential to remain strongly profitable, even at lower tin prices, as well as at increased prices for key consumables. The completed Feed and CBE increase proven and probable reserves to 4.6-million tonnes at 3.58% tin, which translates into 167 300 t of tin, while increasing the life-of-mine (LoM) to 12.5 years.

The optimised process flow sheet resulted in 6% higher yearly average plant throughput rates and an increase in tin recoveries to 73%.

Further, Alphamin foresees a cash margin of about $11 040/t of tin sold, yielding LoM yearly average earnings before interest, taxes, depreciation and amortisation of about $110-million, based on constant 2017 terms.

The company claims that the robust economic performance indicators of a net present value, at an 8% discount rate, of $402.2-million, as well as a real, after-tax, project internal rate of return of 49.1%. The project payback period is 17 months from first tin production.

“The Feed programme’s emphasis was to reduce the implementation and operational risks associated with the project wherever possible, and resulted in necessary increases in certain capital and operating costs,” he says.

The improved mine design, process flow sheet optimisation and an improved tin price outlook have enhanced the forecast economic performance indicators and overall robustness of the Bisie tin project significantly, despite the cost increases, explains Kamstra. He adds that the mining project presents Alphamin shareholders with an attractive opportunity to participate in one of the highest-grade known tin deposits in the world.

The project team recently completed the optimisation of the mine and process plant for Bisie. Although the fundamental mining method has not changed, the layout and mine design parameters have changed notably from the updated feasibility study issued in June, 2016.

The mine design was developed based on the revised criteria, including a reduction in cutoff grade from 1.8% to 1.4%, owing to a far higher tin price, which resulted in a 30% increase in ore tonnes mined, a 10% increase in tin tonnes mined, and an LoM extension of 2.5 years.

The capital footprint has been defined as mine and associated infrastructure development up to and including December 2018. This includes about 64 000 t of ore from the ore drive development, which will be stockpiled prior to plant commissioning. Stoping will start outside the capital footprint.

Contractors on the Bisie tin project will mine the Mpama North orebody using proven underground mechanised mining methods to deliver ore to the process plant at an expected rate of between 25 000 t/m and 35 000 t/m.

A comprehensive programme of metallurgical testing was executed to support the CBE. An overall metallurgical recovery of 80% was achieved under laboratory conditions. Factoring in operating conditions, operator skills and an element of conservatism, an overall recovery of 73% has been applied in the evaluation of the project economics.

The process design is based on recovery of tin into concentrate using conventional gravity separation methods. The project’s process plant design capacity is between 360 000 t/y and 400 000 t/y.

Alphamin is committed to developing the first large commercial tin mine in the eastern DRC that will produce conflict-free tin concentrate, while promoting community development, safety, health and environmentally sound practices.