Minco Announces Positive Economic Assessment on Woodstock Manganese Project
On July 10, 2014, Minco announced the completion of a positive Preliminary Economic Assessment on its 100% owned Woodstock electrolytic manganese metal project located 5 km west of the town of Woodstock and the junction of the Trans Canada and I95 Highways in west-central New Brunswick.
The Preliminary Economic Assessment (“PEA”) indicates a pre-tax Net Present Value (“NPV”) of CDN$846 million at a 8% discount rate and a pre-tax Internal Rate of Return (“IRR”) of 17.97%, based on a 3,000 tonne per day (“tpd”) open pit mining, hydrometallurgical and electrowinning operation, with a pre-production capital expenditure of CDN$864 million and average annual payable production of approximately 80,000 tonnes of electrolytic manganese metal.
The PEA was completed by Tetra Tech (“Tetra Tech”) and Thibault & Associates Inc. (“Thibault”) and is compliant with National Instrument 43-101 (“NI 43-101”) based on an updated NI 43-101 compliant mineral resources estimate prepared by Mercator Geological Services (“Mercator”).
The PEA’s base case indicates a long project life of 40 years with operating costs anticipated to be the lowest in the world averaging US$0.64/lb of electrolytic manganese metal (“EMM”) produced over the first 20 years and US$0.68/lb EMM over the life of project.
- Base Case Sensitivity
- Capital Costs
- Alternative Case Analysis
- Updated Mineral Resource Estimate
- Open Pit Resources
- Open Pit Mine Plan
- Metallurgy & Processing
- Technical Report
Approximately 98% of the world’s EMM is produced in China with reported average operating costs of US$0.91/lb EMM1 (with the lowest reported at approximately ~US$0.81/lb EMM1), indicating that the Woodstock project will have a clear competitive advantage with its projected low operating costs. Woodstock’s low operating costs are attributed in large part to the amenability of the Woodstock Plymouth deposit to low cost open pit mining methods with low stripping ratios and relatively low industrial electricity rates in New Brunswick that are sustainable for the duration of the project. Conversely, it is believed that Chinese and South African EMM producers continue to face steady upward pressure on mining, electricity, labour and environmental costs and, in the case of China, from mineralization of diminishing grade. As Chinese and South African production costs increase and marginally profitable capacity continues to be phased out, it is expected that Woodstock’s product will become increasingly competitive in the global EMM market, strengthening the earning potential of the project and sustainability of EMM production from the Woodstock deposits in the long term.
Woodstock PEA Base Case Highlights:
Grade to Mill
Note Fig1. Woodstock operating cost breakdown calculated based on base case average life of project operating costs for the 3,000 t/d resource processing rate with integrated sulphuric acid plant as defined by the PEA study.
Note Fig 2. Chinese average operating cost breakdown adapted from SMM EMM Industrial Chain Report (SMM, December, 2013).
The PEA is based on Inferred Mineral Resources, which are not Mineral Reserves and do not have demonstrated economic viability. Inferred Mineral Resources are considered too speculative geologically to have the economic considerations applied to them that would enable them to be categorized as Mineral Reserves and there is therefore no certainty that the conclusions of the PEA will be realized.
Base Case Sensitivity:
The sensitivity analysis produced for the base case shows that the earning potential of the Woodstock project is most sensitive to the total revenue and therefore to commodity pricing. The sensitivity of the project to commodity pricing is primarily influenced by the market price of EMM since the sale of iron ore by-product represents just over 1% of the total revenue.
The following table highlights the economics of the Woodstock project using spot pricing for EMM as of March, 2014. The March 2014 EMM spot price was close to the bottom of the three-year pricing trend and represents a 17% discount to the three-year trailing average price.
At the March 2014 spot EMM price of CDN$1.27 /lb or US$1.15/lb the project economics remain positive with an average annual revenue to operating cost ratio of 1.72.
The life-of-project revenue to operating cost ratio is greater than 1.65 even at EMM prices of 80% of the three year trailing average prices (equivalent to CDN$1.22/lb or US$1.11/lb) for the base case, at which price Woodstock would continue to operate with a positive net revenue while higher cost Chinese and South African EMM producers would be operating at or below their break-even point.
The ability to sustain profitability with commodity prices near the theoretical basement price is considered to be a strong asset to the Woodstock project, owing to Woodstock’s low operating costs.
Increasing the total revenue by 20% increases the earning potential of the project considerably. A 20% increase in the total revenue above the base case value is equivalent to an EMM price of CDN$1.84/lb (US$1.66/lb), which is near the level of EMM prices during most of 2011. Therefore, with an EMM price 20% higher than the base case the NPV and pre-tax IRR would be in the range of CDN$1.5 billion, and 25% respectively.
The total pre-production capital cost is $863.6 million, including a contingency of $167.4 million, calculated primarily at 25% of the direct capital costs. The capital cost includes a sulphuric acid plant and a lime kiln for production of sulphuric acid and lime onsite. The total capital cost organised in accordance with a work breakdown structure, defined to Level 2, to define the capital costs by direct capital costs, indirect capital costs, owners costs and contingency, is summarized in the table below:
Initial Capital Cost (CDN$)
Tailings Management Facility
Environmental monitoring during construction
Total Direct Capital
1 The “Processing” capital cost assessment of $526.8 million, which includes the concentrator, hydrometallurgical plant, electrowinning plant and sulphuric acid plant, is considered to be Class V based on the Association for the Advancement of Cost Engineers (AACE) guidelines, with an opinion of probable cost accuracy in the range of -10% to +40%, and is comprised of $262.3 million for hydrometallurgical processing equipment, $166.9 million for hydrometallurgical plant installation, $90.7 million for sulphuric acid plant and $6.9 million for limestone quarry development.
Alternative Case Analysis:
The base case is one of four cases evaluated in the PEA which can be reviewed in detail in the Technical Report to be filed within 45 days of this news release. The parameters of these alternative cases are as follows:
3,000 t/d operation, with a sulphuric acid plant, importing sulphur to produce sulphuric acid on site, producing on average 80,104 t/a EMM, Pricing based on 50/50 average three-year trailing average of US & European prices to March 31, 2014
Alternate case “A”:
1,500 t/d operation, with a sulphuric acid plant, importing sulphur to produce sulphuric acid on site, producing on average 41,062 t/a EMM, pricing based on three-year trailing average of US prices
Alternate case “B”:
3,000 t/d operation, without a sulphuric acid plant, importing sulphuric acid, producing on average 80,104 t/a EMM, pricing based on 50/50 average three-year trailing average of US & European prices to March 31, 2014
Alternate case “C”:
1,500 t/d operation, without a sulphuric acid plant, importing sulphuric acid, producing on average 41,062 t/a EMM, pricing based on three-year trailing average of US prices to March 31, 2014
Updated Mineral Resource Estimate:
Mercator updated the May 6th, 2013 Woodstock Manganese Project mineral resource estimate by assigning a 3.5% Mn minimum block grade as the updated cut-off grade. The new cut-off grade was selected on the basis of more detailed economic analysis information generated since the last estimate of May 6th, 2013 which assigned a 5% minimum cut-off grade. The updated resource estimate is shown below and has an effective date of July 10, 2014.
All resource estimation factors and modelling methods are otherwise as previously disclosed in the Company’s press release dated May 23rd, 2013 and detailed in the supporting resource estimate Technical Report filed on SEDAR.
Updated Woodstock Manganese Project Mineral Resource Estimate – Effective July 10, 2014
Mn % Cut-off
1. *Resource statement cut-off grade is based on parameters established by the current PEA and reflects a reasonable expectation of economic viability based on market conditions and open pit mining methods.
2. Mineral resources that are not mineral reserves do not have demonstrated economic viability.
3. This estimate of mineral resources may be materially affected by environmental permitting, legal, title, taxation, sociopolitical, marketing, or other relevant issues.
Open Pit Resources:
For purposes of designing the open pit for the Plymouth deposit at Woodstock, the updated Inferred Resource of 44.8 million tonnes (“Mt”) grading 9.85% Mn (utilizing a 3.5% Mn cut-off) as estimated by Mercator was utilized.
The Plymouth resource is categorized by two types of mineralization defined respectively as the “red” mineralization and “grey” mineralization. For both the red and grey mineralization the manganese is characterized by rhodochrosite, a manganese carbonate mineral that is readily leachable. The key difference between the red and grey mineralization is determined by the mineralogy of the iron, with the red mineralization containing iron predominantly in oxide form (comprised of hematite, magnetite, ilmenite), whilst the iron in the grey mineralization is primarily in carbonate form (comprised of siderite). The difference in the mineralogy impacts the operating costs when entering the leach circuit with the grey mineralogy being more readily leachable and therefore consuming more sulphuric acid and therefore costing more to process. Given this difference, the open pit mine plan is based on calculating Net Smelter Return (“NSR”) values per block for the red and grey mineralization and prioritizing the higher NSR value blocks in the mine plan scheduling.
From the Mercator Inferred Resource, Tetra Tech calculated the following in-pit resources for 3,000 t/d (base case) and 1,500 t/d scenarios:
Mill Throughput 3,000 t/d
Mill Throughput 1,500 t/d
Open Pit Mine Plan:
Open pit mine plans were designed for both the 3,000 t/d and 1,500 t/d scenarios whereby the optimum economic results are achieved by completing the open pit mining operations in the first 13 years out of a total project life of 40 years for the 3,000 t/d scenario and the first 20 years out of a total project life of 61 years for the 1,500 t/d scenario. During the open pit operation, high grade mineralised material will be directly delivered to the processing plant and the remainder will be stockpiled for processing at a later date. After the open pit mining operations are completed the mill will draw down material from stockpiles via a conveyor system for the remaining 27 years and 41 years of each of the 3,000 t/d and 1,500 t/d scenarios respectively.
In the case of the 3,000 t/d scenario the key parameters of the open pit mine plan are that it will provide mill feed at a rate of 3,000 t/d (1.05 Mt/a). A total of 96.96 Mt of material will be mined at an average strip ratio of 1.34 over a 13-year life of open pit. The total material to be moved includes 41.41 Mt of Inferred Mineral Resources with an average manganese grade 9.92%, 51.61 Mt of waste rock and 3.94 Mt overburden. The total mining start-up capital is estimated to be CDN$15.4 million and the unit operating cost over the life of open pit is estimated to be CDN$2.75/t mined.
In the case of the 1,500 t/d scenario the key parameters of the open pit mine plan are that it will provide mill feed at a rate of 1,500 t/d (0.525 million tonnes per year (“Mt/a”). A total of 57.1 Mt of material will be mined at an average strip ratio of 0.78 over a 20-year life of open pit. The total material to be moved will include 32.01 Mt of Inferred Mineral Resources with an average manganese grade of 10.12%, 22.43 Mt of waste rock, and 2.66 Mt of overburden. The total mining start-up capital is estimated at CDN$9.7 million and the unit operating cost over the life of open pit is estimated at CDN$4.11/t mined.
Metallurgy & Processing:
An extensive bench scale metallurgical test program completed by Thibault over the last three years (July 2011 to present) has defined a technically viable hydrometallurgical process technology for the production of commercial grade EMM containing between 99.70% to 99.76% Mn. The process development program was focused on the assessment of competitive processing methods with measures to minimize the environmental impact based on commercially proven processing technologies.
The fully integrated process for pre-concentration of the mill feed, hydrometallurgical processing of the concentrate and treatment of the waste streams includes: magnetic separation, leaching of concentrate, purification of leach solutions, electrowinning of manganese metal, iron precipitate and solid waste stabilization and wastewater treatment.
The process technology defined for processing of the mill feed is based on the technology to achieve an ultra-pure solution of manganese sulfate. Manganese occurs in the Plymouth mineral resource predominately as a manganese carbonate (Rhodochrosite) as a reduced form of manganese (Mn with an oxidation state of II) and provides a competitive edge for EMM production relative to high grade manganese oxide feed material (Mn with an oxidation state of III or IV). Many manganese resources around the world are of the oxide type and are not readily soluble in acid, thus requiring high cost roasting, reduction and environmental processing technologies to reduce manganese and form manganese sulphate in solution as is required for EMM production. The Plymouth deposit material is readily soluble in sulphuric acid forming a solution containing manganese sulphate with a minimal amount of heavy metal impurities.
Iron is also present in the Plymouth deposit as both iron oxides (hematite, magnetite and ilmenite) and as an iron carbonate (siderite). In addition to silicates, other gangue (waste) mineralization such as dolomite and apatite are defined as acid consumers.
The development of pre-concentration process technologies has focused on the ability to selectively remove a portion of the acid consuming minerals prior to hydrometallurgical operations to reduce the demand for sulphuric acid. Low intensity magnetic separation (LIMS) to remove magnetic iron followed by high gradient magnetic separation (HGMS) has been identified as the best available technology for pre-concentration of the mill feed with an overall mass rejection of 34% of the mill feed to achieve a concentrate containing 15.65% Mn at 85.7% recovery (results based on bench scale testing completed to date).
The rejection of acid consuming metals such as iron, aluminum and magnesium (which are present in the deposit as carbonate or silicates minerals) and the co-production of magnetic iron concentrate at 54.6% Fe have improved on the economic viability of the proposed hydrometallurgical process.
Hydrometallurgical recovery of concentrate
The hydrometallurgical bench scale test program has identified reagent consumption rates, electrical power consumption rates and the operating parameters for each unit operation based on extensive testing to optimize manganese recovery and purity of the advance electrolyte solution relative to target market specifications for EMM. The operating parameters were used to simulate the hydrometallurgical flowsheet and produce a high purity manganese sulphate electrolyte for extensive bench scale electrowinning tests (using a 1.2 liter electrowinning cell – a prototype to a commercial EMM production cell). Based on quantifying the optimum economic parameters relative to acid consumption, the hydrometallurgical process was operated at reduced acid demand to achieve a 90.0% recovery of manganese (up to 99% of the manganese can be leached using aggressive sulphuric acid leach conditions).
The unique features of the hydrometallurgical process technology include:
- sulphuric acid leaching of the high gradient magnetic separation concentrate is controlled at certain temperature in the range of 60 to 80 degrees Celsius to optimize on acid consumption;
- dual-stage precipitation of iron to form an environmentally stable iron complex for conventional solids disposal, using a combination of pulverized limestone and on-site production of calcined lime for each stage. Iron residues and tailings produced by the process are defined as non-acid generating and are in general compliance with environmental guidelines for leachate quality;
- the removal of trace heavy metals from the leach solution as an environmentally stable metal sulphide followed by the removal of solution phase sulphides by activated carbon absorption prior to electrowinning;
- electrolysis of the high purity manganese sulphate solution to produce EMM using commercially proven electrowinning – membrane cell technology without the addition of toxic heavy metals such as selenium to optimize on the electrowinning efficiency;
- heat recovery (for leaching and iron precipitation unit operations) and co-generation of electricity from the acid plant operations;
- use of compressed natural gas for boiler steam production, and;
- the use of tailor-designed wastewater systems to eliminate residual ammonium sulphate (used as a buffering agent in electrowinning) and trace heavy metals in compliance with final effluent environmental guidelines.
The overall recovery of manganese based on the optimum economic parameters for the hydrometallurgical process was defined as 77.1% for the PEA, based on the recovery of manganese in both the magnetic separation and hydrometallurgical circuits.
With various tests to optimize the electrowinning cell performance relative to current efficiency and metal quality, the electrowinning tests consistently produced EMM with a metallic manganese content (based on trace metal analysis) of greater than 99.99% and a total manganese content (base on trace metals and non-metallic trace elements such as oxygen, nitrogen and hydrogen) ranging from 99.70% to 99.76% Mn. The resultant manganese metal complies with end-user EMM product specifications for steel production.
Although, the metallurgical development programs for Woodstock have focused on the production of high grade EMM, the intermediate production of purified manganese sulphate solution may be regarded as an interim step enabling the add-on production of manganese chemicals, manganese catalyst, battery grade manganese dioxide and high purity metal for electronics.
The full PEA technical report, including details of the updated mineral resource estimate, will be filed under the Company’s profile on SEDAR at www.sedar.com within 45 days of the filing of Minco's July 10, 2014 Press Release. The technical report was prepared by Tetra Tech in compliance with NI 43-101 with specific focus on mine design, infrastructure (including TSF) and environmental parameters. The geological resource sections were completed by Mercator Geological Services. The metallurgy and process design sections were completed by Thibault and Associates Inc.