Unlocking WA’s potash resource

Historically, Australia has had few known resources of potash, but ongoing exploration has led to some deposits discovered in Western Australia, South Australia and Victoria. Kalium Lakes is one of the exploration companies leading the race to become the first domestic sulphate of potash (SOP) producer in Australia, and is currently undertaking a Bankable Feasibility Study on its Beyondie Sulphate Of Potash Project (BSOPP) in Western Australia.

What is potash?

Potash is the common name for various salts that contain potassium minerals in water‐soluble form. While not as glamorous as other mining commodities, it is becoming increasingly sought after because it is an important component of many fertilisers as it is a source of potassium which helps raise yields and disease resistance for plants.

With the global population expected to grow to 9.6 billion by 2050 and the amount of arable land per capita declining, the global demand for fertiliser will also grow due to the need to improve agricultural yields and productivity. There are four main forms of potash: potassium chloride (KCl or MOP), potassium sulphate (K2SO4 or SOP), potassium nitrate (KNO3), and sulphate of potash magnesia (SOPM).

SOP in particular is sought after for fertilisers due to its minimal chloride content and lower salinity index than other forms of potash, both of which can be harmful to plants, and diminish quality and crop yield. There has been a surge in SOP demand with the market growing from 3.5Mtpa in 2009 to 7Mtpa in 2016, and it now attracts a price premium over MOP of between 40 to 100 per cent.

Mining for SOP

SOP is not a naturally occurring mineral and primary production requires extracting potassium and sulphate ions from naturally occurring complex ores or brines via evaporation and/or chemical methods. SOP can be produced from either: salt lake brine processing; potassium chloride and sulphate salts reaction; or the Mannheim process.

Salt lake brine processing

Processing of natural brines is a relatively low-cost option, but is limited because of the small number of salt lakes in the world that contain both potassium and sulphate. There are brine operations in Utah (Great Salt Lake Minerals Corporation, owned by Compass Minerals International), Chile (Salar de Atacama, owned by SQM) and China (with the largest producer being SDIC Xinjiang Luobupo Potash). As lakes with sufficient brine mineral levels are rare, this method only accounts for 15-20 per cent of global supply.

Potassium chloride and sulphate salts reaction

Potassium chloride can be reacted with various sulphate salts to form a double salt that can be decomposed to yield potassium sulphate. The most common raw material employed for this purpose is sodium sulphate. Sodium sulphate, either in the form of mirabilite (also known as Glauber’s Salt) or sulphate brine, is treated with brine saturated with MOP to produce glaserite. The glaserite is separated and treated with fresh MOP brine, decomposing into potassium sulphate and sodium chloride. There are only a few operations in the world with K+S Kali and Rusal being the key producers utilising this method.

Mannheim process

The most common method of producing potassium sulphate is the Mannheim process, which is the reaction of potassium chloride with sulphuric acid at high temperatures. The raw materials are poured into the centre of a muffle furnace heated to above 600oC.

Potassium sulphate is produced, along with hydrochloric acid, in a two-step reaction via potassium bisulphate. There are a number of operations in the world with Tessenderlo Group and Chinese privates being the key producers utilising this method. This method for creating SOP accounts for 50 per cent to 60 per cent of global supply. The Mannheim process is also the most expensive of the processing techniques due to the high input costs associated with purchasing MOP and sulphuric acid.

The Beyondie Sulphate Of Potash Project (BSOPP)

The BSOPP covers an area of around 2,400km2 in Western Australia’s Beyondie, 10 Mile and Sunshine Lakes area, and Kalium Lakes intends to develop a sub-surface brine deposit to produce approximately 150 kilotonne per annum of SOP product and by-products through evaporation and processing operations.

The project includes the development of evaporation and crystalliser ponds, installation of production bores, trenches, pumps, pipelines, purification facility, access road upgrades, natural gas pipeline, and expansion of accommodation village, buildings, and services and utilities (including water, power and waste disposal).

The project, which is located close to key infrastructure, is already well progressed and has completed a Pre-Feasibility Study (PFS) involving detailed technical reports, test pumping of brine, environmental, heritage surveys and economic analysis; and a Bankable Feasibility study is currently underway.

The pilot project

Kalium Lakes is undertaking a pilot project using trenches and bores to capture brine from beneath the surface and pump it to lined evaporation ponds. The liquid is then dried by the sun, leaving behind a solid mixed-potassium salt which is sent to a German purification plant that produces the final SOP product.

The pilot evaporation pond trials begun construction in June 2017 with first brine entering the system in August 2017. These pilot ponds have been run continuously and form the basis of pond design for the Bankable Feasibility Study (BFS).

Since August last year, more than 164 million litres of brine has been pumped from a bore and/or trench, with 83 million litres pumped into the trial ponds where it has evaporated prior to reaching the salting point.

At this point brine is gravity fed to the next series of ponds where the sodium salts crystallise out of solution. The brine is again gravity fed to the series of ponds where potassium salts begin crystallising out of solution. Finally, a residual magnesium bittern remains, representing only one to two per cent of the original brine volume pumped into the concentrator pond. This residual brine has been the subject of magnesium product investigations and pilot trials. Importantly, all the ponds are tiered so that the brine can flow via gravity, without the need for pumping between ponds.

The response of the water levels to brine abstraction has been monitored in a number of monitoring bores throughout the filling and operations of the trial evaporation ponds.

During the filling of the ponds flow rates ranged from 10 litres per second (L/s) to 20 L/s, associated with approximately 17m of aquifer drawdown in the deep confined aquifer between August and October 2017.

Between October 2017 and April 2018, abstraction continued intermittently in response to water levels in the ponds, pumping rates ranged from six to 12 L/s with deep confined aquifer drawdown steady at approximately six metres during March and April 2018 in relation to constant pumping at 6.5 L/s.

Kalium Lakes Managing Director, Brett Hazelden, said, “These Large Scale Pilot Evaporation Ponds cover around five MCGs in total size and have proved invaluable in testing every facet of a fully operational potash evaporation pond process.

“It has enabled Kalium Lakes to assess pump and pipe requirements from bores and trenches, determine pond design parameters to achieve a fully gravity fed system, observe brine evaporation behaviour, and measure salt crystallisation and growth, test harvesting techniques and identify maintenance requirements.”

Key considerations during pump procurement

Kalium Lakes procured Franklin 8” 22.30 kW bore pumps for the trial bores, with flexibility a key consideration during the testing phase to allow trials on the evaporation ponds, as well as monitoring and testing the aquifer.

“With the two pilot bores currently operating, we performed many trials to determine the actual pumping dynamics and pressure losses within our trial system. With this data, when we up-scale to full production, a more fit for purpose solution can be installed,” Mr Hazelden said.

“As we have a total brine flow rate of over 300 L/s within summer in a network over 50km long, an overly conservative design will add significant capital cost to the project. Our trial equipment has allowed a more narrowly defined design to be completed to reduce the upfront costs to the project.”

With the procurement of pumps for the final production bores underway, energy efficiency has become an important consideration forequipment, as well as material selection to reduce maintenance and repair costs.

“Energy is a special consideration for the full production bores as the project is drawing from over 30 bores over an 80km2 area. Operating cost will become a major driver of this project. The procurement of the full production bores is currently ongoing and the pumping efficiencies will be adjudicated for each vendor within the tender process,” Mr Hazelden said.

“As we are dealing with brine, materials selection is critical to ensure our production targets are met and corrosion can be managed with pump maintenance and replacement. As we have a large number of bores, dependent on the time of year, there is redundancy within our system. During winter months, bores can be taken offline for servicing where required.”

Gaining further insight for the final design

A Bankable Feasibility Study of the project is currently underway with the results of the pilot pond trial being used to inform design parametres. In May, the sonic monitoring bore installation and air-core geological programs were successfully completed.

The program has involved drilling 142 aircore exploration holes on transects totalling 7,794m of drilling. This has closed the drill spacing to between 265m and 422m at the 10 Mile and Sunshine deposits respectively, and confirmed the geological extent of the target geology and brine mineralisation. A sonic drilling rig has followed up the aircore drilling to twin 10 key aircore holes, in order to obtain cores for laboratory testing, and install monitoring bores for a total of 710m of drilling.

Downhole geophysics (spectral gamma, conductivity and Borehole Magnetic Resonance (BMR)) has been completed on all monitoring bores to measure lithological changes and in-situ aquifer properties and will be calibrated to laboratory testing of core plugs to assist with resource estimation.

Notably, the BMR tool has been able to provide insight into aquifer properties on a resolution across the palaeovalley sequence and bedrock lithologies not previously observed from test pumping, drilling or laboratory testing. The results indicate that in-situ specific yields of the basal sand and silcrete aquifer zones may be between eight and 25 per cent, however these zones are significantly thicker than previously considered, the sandy lenses of the lower clay sequences have higher specific yields which were previously categorised as lacustrine clays, which will now be incorporated into to the deep aquifer resource.

The drilling and geophysical surveys have also identified additional resources within the weathered zones of the sandstone and vesicular basalts encountered within the stage one area. These zones will now be brought into the brine resource envelope.

An additional production bore has been installed within the weathered sandstone aquifer at Lake Sunshine and is currently undergoing long- term test pumping.

Tapping into a new resource
More than 10,000 tonnes of salts have been produced so far, including 3,160 tonnes of mixed potassium salts that can be processed to generate approximately 520 tonnes of SOP.

The project’s pre-feasibility study suggests BSOPP will generate $1 billion in free cash flow over a 20-plus year mine life.

“The program has continued to confirm the Pre-Feasibility Study Resource model within our initial stage one Mining Lease Areas,” Mr Hazelden said.

“We envisage these results will enable an upgrade of the deposit to include a future Measured Resource and Proved Reserve, which in turn will support the Bankable Feasibility Study and project financing.”

The current assumed stage one Area has a mine life of 23 years at 75ktpa SOP, when utilising the existing Probable Reserve. If the project were to be expanded to ramp up to a rate of 150Ktpa, the stage one production from Beyondie, 10 Mile and Sunshine would comprise 45km of trenches with eight pumping stations and 30-40 bores.

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