- Conventional and well understood process flowsheet announced for the production of lithium carbonate and boric acid on site
- Preliminary site layout completed with small footprint allowing project to be considered for a shorter permitting process
- Rhyolite Ridge is a unique hard-rock sedimentary (non-clay) lithium-boron deposit on track to become a major lithium and boric acid producer in North America
NORTH SYDNEY, Australia, June 05, 2018 (GLOBE NEWSWIRE) — Australian-based lithium-boron mine developer Global Geoscience Limited (“Global” or the “Company”) (ASX:GSC) today unveiled additional details of its development plan for the 100%-owned Rhyolite Ridge Lithium-Boron Project (“Project”) in Nevada, USA.
Global is pleased to provide the proposed process flowsheet and site layout for Rhyolite Ridge. This flowsheet is based on findings from the Project’s recently completed first phase of the Pre-Feasibility Study (“PFS”) and comprises three key parts:
- Sulphuric acid leach to extract lithium and boron from crushed rock into a Pregnant Leach Solution (“PLS”). This step is similar to acid leaching commonly used in oxide copper mines.
- Evaporation and concentration of the PLS followed by crystallisation of boric acid. Using mechanical evaporators, which result in a substantial water savings, the PLS is further concentrated. The boric acid product is then further refined by flotation and recrystallisation to produce high-purity boric acid. This step is broadly similar to the process used at Rio Tinto’s Boron Mine in California.
- Further evaporation and concentration of the PLS to allow for removal of remaining impurities via precipitation and ion exchange, followed by precipitation of lithium carbonate. This step is very similar to the process used in lithium brine operations.
The Rhyolite Ridge site layout has been designed with the total surface disturbance footprint of the mine and related facilities being less than one square mile (640 acres), allowing the Federal Bureau of Land Management (“BLM”) to consider the project for the Environmental Assessment (“EA”) process. The EA process is less time consuming than the Environmental Impact Statement (“EIS”) process. The site layout includes the open pit, process plant, haul roads, overburden storage, leach residue storage and salt storage. No evaporation ponds or tailings dams are required.
Global Geoscience’s Managing Director, Bernard Rowe commented:
“Our PFS work to date has provided a clear path to developing Rhyolite Ridge into a major, low-cost producer of lithium and boron in an environmentally sustainable manner.
“We are prudently progressing Rhyolite Ridge toward production and remain on track to release the PFS outcomes in Q3 2018.”
Global Geoscience expects to complete the necessary environmental baseline studies by the end of Q3 2018. Once this work is complete and the Plan of Operations (Application) is submitted to the BLM, the BLM will make the determination regarding the Environment Assessment pathway forward for permitting and approval.
The Company is increasingly confident that Rhyolite Ridge will qualify for the EA approval process, which typically can be completed within six to nine months of completion of baseline studies.
Based on this permitting outcome and the anticipated time required to complete feasibility studies, an indicative timeline to initial lithium carbonate and boric acid production is provided below.
*This timeline is preliminary and subject to change and assumes an Environmental Assessment for permitting.
Overview of Development Approach
The Project plan envisages mining between 3-4 million tonnes per annum of lithium-boron rich mineralisation.
The proposed steps to produce lithium carbonate and boric acid at Rhyolite Ridge are:
- Shallow open-pit mining of the mineralisation
- Crushing the mineralisation to circa 25mm (1 inch)
- An on-site acid plant producing sulphuric acid, power and steam for the operation
- Acid leaching of the mineralisation in a series of vats
- A processing plant extracting boron and then lithium from solution via a series of evaporation, crystallisation and precipitation steps.
A schematic overview of these proposed steps is provided below.
The proposed processing technologies are well understood and have been proven at commercial scale. An overview of the proposed processing flowsheet is provided below.
Key aspects of the proposed flowsheet are:
- On-site acid plant provides all of the steam and power required
- The acid solution contains about 10-20% sulphuric acid and 80-90% water
- Vat leaching to be done at 50-60o C and at ambient pressure
- Boron will be separated first from the PLS
- Impurities to be removed via precipitation are primarily sodium, magnesium, calcium, iron
- Precipitation of lithium carbonate and/or other lithium products
The acid plant will produce large amounts of steam through an exothermic reaction. This steam will be used in the processing plant as well as generating electricity via steam-driven turbines. Sufficient power will be generated to meet all site requirements plus a circa 20-30MW surplus to be sold into the grid.
The acid plant will be a standard, off-the-shelf design similar to various acid plants constructed recently in the USA and globally. A schematic overview of the plant is provided below.
In the proposed vat leach at Rhyolite Ridge, the crushed lithium-boron mineralisation and acid leach solution will be contained in rectangular lined concrete vats. This approach limits heat losses and permits operation at an elevated temperature to increase boric acid solubility.
The preliminary Rhyolite Ridge design envisages 12 vats, each approximately 40m wide by 40m long by 8m high. Crushed ore is loaded into the vat and then flooded with an acid leach solution running counter current to the ore. The leached ore is drained, washed and unloaded to complete the leach cycle.
A typical vat leaching setup in provided below.
Vat leach offers a high degree of control over leach kinetics – resulting in a reliable, repeatable and robust leach process.
Vat leaching also achieves relatively high concentrations of lithium and boron into PLS. The higher concentration in the vat leach PLS means less evaporation and subsequently, lower power consumption. For further information on the advantages of vat leaching Rhyolite Ridge mineralisation, see the Global Geoscience announcement dated 23 May 2018.
In the processing plant, heating and evaporation will be used to concentrate the PLS with the concentrated solution sent to crystallisers.
The solubility of boron is very temperature dependent. The PLS coming into the evaporators is planned to be at a temperature of approximately 50-60o C and contain 0.05-0.10% lithium and 5.0-5.5% boric acid.
The boric acid will be separated from the PLS first, primarily by evaporation/concentration and temperature adjustment. An overview of the boric acid circuit is provided below:
The residual PLS (brine) is then treated in the lithium carbonate circuit which is outlined in the diagram below.
The brine entering the lithium carbonate circuit is estimated to contain 1.0-1.4% lithium.
Metallurgical testwork is ongoing and now focused on vat leach optimisation, crystallisation and purification steps.
The planned pilot plant scale testwork will be done using the facilities of laboratories with expertise specific to either leaching or crystallisation stages of processing. A key purpose of the pilot plant testwork is to generate sufficient quantities of lithium carbonate and boric acid to send to various potential customers. The overall budget for the pilot plant testwork remains US$5 million.
A plan of the initial site layout is provided below.
The site layout has been designed to take advantage of the topography and to not impact on potential expansions of the initial open pit.
The planned surface disturbance is less than one square mile. A small footprint is important for the project to be considered for the Environmental Assessment (“EA”) process by the Federal Bureau of Land Management and state regulators.
The initial open pit contains approximately 20 million tonnes of lithium-boron mineralisation. This pit was constrained to minimise surface disturbance and has a footprint of 0.25 square miles. The initial open pit is located within an unconstrained open pit that would mine the current Mineral Resource. The larger pit contains 87 million tonnes of lithium-boron mineralisation and has a footprint of 2.9 square miles. The Company intends to obtain the permits necessary to mine this larger area at a later date.
The mineralisation will be trucked to the crusher and then a conveyor will transport the crushed mineralisation 3km to the processing plant. The areas designated for dry stacking of the leach residue and for salt residue are located near the processing plant.
A power line approximately 20km long is planned to be built from the processing plant to connect to the grid near Albermarle’s Silver Peak lithium mine.
Contacts at Global Geoscience
About Global Geoscience
Global Geoscience Limited (ASX:GSC) is an Australian-based lithium-boron mine developer focused on its 100%-owned Rhyolite Ridge Lithium-Boron Project in Nevada, USA. Rhyolite Ridge is a large, shallow lithium-boron deposit located close to existing infrastructure. It is a unique sedimentary deposit that has many advantages over the brine and pegmatite deposits that currently provide the world’s lithium. The Rhyolite Ridge Pre-Feasibility Study is in progress.
Global’s Rhyolite Ridge is the only lithium deposit in the world that has been demonstrated to be amenable to simple acid leach processing, reinforcing it as an economically viable alternative to spodumene and brine deposits as a major, low-cost and long-term source of lithium.
Global Geoscience is aiming to capitalise on the growing global demand for lithium and boron. Lithium has a wide variety of applications, including pharmaceuticals, lubricants and its main growth market, batteries. Boron is used in glass and ceramics, semiconductors and agriculture. Global Geoscience aims to develop the Rhyolite Ridge Lithium-Boron Project into a strategic, long-life, low-cost supplier of lithium carbonate and boric acid. To learn more please visit: www.globalgeo.com.au.
Competent Persons Statement
The information in this report that relates to Exploration Results is based on information compiled by Bernard Rowe, a Competent Person who is a Member of the Australian Institute of Geoscientists. Bernard Rowe is a shareholder, employee and Managing Director of Global Geoscience Ltd. Mr Rowe has sufficient experience that is relevant to the style of mineralisation and type of deposit under consideration and to the activity being undertaken to qualify as a Competent Person as defined in the 2012 Edition of the ‘Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves’. Bernard Rowe consents to the inclusion in the report of the matters based on his information in the form and context in which it appears.