TIDMSO4
RNS Number : 6856Q
Salt Lake Potash Limited
14 September 2017
14 September 2017 AIM/ASX Code: SO4
SALT LAKE POTASH LIMITED
Expert Testwork Confirms SOP Process With Excellent Recoveries
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Salt Lake Potash Limited (the Company or SLP) is pleased to
report excellent results from SOP process development testwork
performed by globally recognised potash process leaders,
Saskatchewan Research Council (SRC).
The comprehensive testwork program validates and refines the
parameters used in the process plant flowsheet for the Company's
Goldfields Salt Lake Project (GSLP). Importantly, the testwork was
conducted on a 60kg representative sample of kainite harvest salt
produced on site at Lake Wells.
Highlights from the SRC process testwork include:
High Potassium Recovery Indicated
Ø Bench scale testing on the complete plant process confirms an
overall process plant potassium recovery of over 92% is achievable,
validating parameters of GSLP mass balance models to date.
Ø SOP produced exceeds the industry high-grade benchmarks of 52%
K(2) O and 54% SO(4) .
Flexible Process Options
Ø The feed salt can be easily upgraded through removal of coarse
halite, reducing the mass feed to flotation by up to 25%.
Ø Both reverse and direct flotation show excellent recovery (up
to 97%), providing optionality in process selection depending on
brine handling requirements.
Ø Both mechanical cell and column flotation were tested
successfully.
Potential for Additional Co-products
Ø The SRC work has opened an opportunity to make a valuable
MgSO(4) co-product with limited additional process input.
Further Development Work Accelerated
Ø SRC has been engaged to perform selected further optimisation
tests followed by a continuous locked cycle operation, to produce
significant quantities of schoenite flotation product and SOP to be
produced for further testing and marketing.
Commenting on the testwork, SLP's CEO, Matt Syme, said "We are
very pleased with the results received from SRC, the world's
leading potash laboratory, which reiterate the excellent attributes
of the Project. The testwork results validate the flowsheet for the
GSLP and provide us with a number of important options to further
optimize the production process and therefore the Project."
The GSLP SOP Production Process
The proposed process for production of SOP at the GSLP sees
brine extracted from Lake Wells concentrated in a series of solar
ponds to induce the sequential precipitation of salts, firstly
eliminating waste halite and then producing potassium-containing
salts (Harvest Salts) in the harvest ponds.
The Harvest Salts are then treated in a processing plant to
convert these salts into SOP, while minimising deportment of sodium
chloride (a contaminant) to the product. The SOP production process
consists of attrition, reverse flotation to remove chlorides,
conversion of the mixed sulphate salts to schoenite, and
crystallisation of the schoenite to SOP, before drying and
packaging.
SRC Process Development Work
The testwork was performed by the SRC in Saskatchewan, Canada.
SRC is a recognized global leader in potash process metallurgical
testing. SRC's Minerals team has the facilities and expertise to
design and perform potash processing and metallurgical testing work
for the potash industry worldwide.
The objective of the SRC testwork was to validate and refine the
process parameters used in the production model and process
flowsheet at the Company's GSLP. These process parameters were
designed by the Company's metallurgical consultants based on
experience overseas and results for GSLP lab testwork in the USA
and Australia.
The testwork program was designed to improve the Company's
understanding of the processing plant component of the operation
using actual Harvest Salts produced from Lake Wells brines under
site conditions. These Harvest Salts differ from salts produced in
laboratory evaporation trials and provide a much more
representative basis from which to develop an economic process
route.
The testwork program was designed and managed by the Company and
international brine-processing expert Mr Carlos Perucca of Carlos
Perucca Processing Consulting Ltd (CPPC).
Harvest Salt Sample Preparation
The Company selected a single harvest (60kg) of harvest salt
from the Site Evaporation Trial (SET) at Lake Wells which produces
Harvest Salts from Lake Wells' brine under actual site conditions.
The Harvest Salts are within the range of salt composition
(chemical and physical characteristics) expected in a commercial
scale operation.
Feed Assay and Characterisation
The received harvest salt had excess brine removed before being
homogenised and sampled for chemical assay and mineralogical
analysis by SRC. The remaining salt was screened at 2mm with
oversize crushed to 100% passing 2mm. This formed the feedstock for
the process development work. ICP analysis of the homogenised feed
sample is shown in Table 1.
Sample CaO, % K(2) O, % MgO, % Na2O, % S, % Insol, %
----------- ------- ---------- ------- -------- ----- ---------
Feed Salt 0.02 10.1 12.4 16.4 9.88 0.1
----------- ------- ---------- ------- -------- ----- ---------
Repeat 0.02 10.4 12.5 16.8 9.92 0.1
----------- ------- ---------- ------- -------- ----- ---------
Table 1: Harvest Salt ICP Assay
X-ray Diffraction (XRD) analysis of the harvest salt showed the
species present as predominantly Kainite (>50%) with lower
proportions of Halite and various hydrations of magnesium sulphate,
correlating well with the chemical analysis.
The harvest salts were also analysed by Scanning Electronic
Microscope (SEM) to ascertain the level of crystal agglomeration in
the as-harvested salt.
Product Salt Liberation and Kainite Destruction
In order to achieve an effective and selective flotation result
it is necessary to liberate the product salts from waste
halite.
A short residence time in an attrition cell was partially
effective in liberating the product salts. As a potential
alternative approach the feed salt was also subjected directly to
kainite decomposition (converting kainite to schoenite) which
comprised a 2 hour residence time at 45% solids in a sulphate
saturated brine (simulated process recycle brine). SEM of the
resulting salt showed excellent salt liberation.
Overall potassium recovery from the destruction reaction was
greater than 100%, up to 146% under optimised conditions, with
excess potassium in the brine reporting as schoenite in the solid
phase. XRD of the decomposition product showed >96% conversion
of kainite to schoenite was achievable in a two hour residence
time.
Once the salts were liberated, size by grade analysis on the
destruction product showed the majority of the potassium containing
salts reported to the fine (<425 um) fraction. A selective
screening of the product allows around 23% of the mass of the
flotation feed to be discarded while retaining 98.5% of the
potassium.
Flotation
Harvest Salts produced from Lake Wells contain approximately 50%
kainite. This allows both direct flotation (of schoenite) and
reverse flotation (of waste halite) as a potential production
model. Both methods were tested on the decomposition product, with
an aim to produce a concentrated schoenite product with less than
5% NaCl out of the flotation circuit. This then allows an SOP
product of commercial quality in the conversion circuit.
Direct flotation in both mechanical cells and column flotation
were tested, successfully recovering up to 93.3% of the potassium
to the flotation product.
Column reverse flotation tests demonstrated excellent
selectivity, indicating potassium recovery of 97.1% was achievable
with excellent halite rejection. The reverse flotation product
contained only 0.6% Na and as such has the potential to product
high purity SOP product.
The balance of the mass in the reverse flotation product is
schoenite and magnesium sulphate, providing an opportunity to apply
a second, direct flotation to the reverse flotation product and
make both a low sodium schoenite feed to crystallisation and a
magnesium sulphate co-product. Magnesium sulphate has a ready
market in Asia as a crop nutrient but also provides potential
operation flexibility in the GSLP project to maximise SOP
production by providing a transportable sulphate source.
SOP Conversion
Tests of SOP conversion of schoenite flotation product at
various solid-liquid ratios were carried out with the optimum ratio
between 1.3 and 1.5 tonnes of water per tonne of feed salt.
Optimisation of reaction time at a solid-water ratio of 1/1.5
showed a minimum retention time of 1.5 hours was required to reach
the Company's target SOP purity of >98%.
The product quality produced from flotation product at varying
retention times is detailed in Table 2, below. At 1.5 hour
retention time the product purity surpasses SLP's internal quality
target of 98% (>53% K(2) O) with a very low sodium content.
Retention Time, h Assay, %
------------------ --------------------------------------------------------------
CaO, wt% K(2) O, % MgO, % Na(2) O, % S, % SO(4) , %
------------------ --------- ---------- ------- ----------- ----- ----------
0.5 0.05 50.5 1.84 0.26 18.7 56.1
------------------ --------- ---------- ------- ----------- ----- ----------
1.0 0.06 52.4 0.42 0.21 18.5 55.5
------------------ --------- ---------- ------- ----------- ----- ----------
1.5 0.05 53.0 0.41 0.19 18.5 55.5
------------------ --------- ---------- ------- ----------- ----- ----------
2.0 0.05 53.2 0.44 0.21 18.8 56.4
------------------ --------- ---------- ------- ----------- ----- ----------
Table 2: SOP Product Purity at Varying Retention Time
The results above compare very favourably to the specifications
of products marketed as SOP for agricultural use worldwide where
average potassium assays range from 50% to 52% as K(2) O and
sulphate assays range from 52% to 54% as SO(4) .
Overall Potassium Recovery
Single pass SOP conversion from schoenite, including recovery of
schoenite from the conversion brine was determined as 39.7% in the
SRC lab, with the remaining schoenite recycling to the kainite
decomposition reactors to recover potassium.
Tests were carried out on recovery of residual potassium from
excess flotation brine as kainite, with a 98.2% recovery of
potassium from this stream achievable, which is recycled to the
plant feed.
This results in an overall potassium recovery of up to 92%,
depending on the flotation option and brine handling methods
employed in the process development. This compares favourably with
performance parameters included in the mass balance models which
the Company has generated for its feasibility studies. Future mass
balance models will be refined to reflect the SRC results.
International salt processing expert Carlos Perucca of CPPC
commented on the SRC results "I am extremely pleased with the
results of the SRC testwork and the implied potential for an
efficient SOP production process at the Goldfields Salt Lake
Project. In my experience the potential recovery indicated by this
work is at the high end of recoveries of other SOP operations
worldwide."
Next Steps and Process Validation
The work completed by SRC has highlighted several opportunities
for further refinement and development of the GSLP SOP process.
SRC has been engaged to carry out further optimisation tests to
validate and duplicate the results achieved to date, followed by a
locked-cycle continuous production test to test brine recycle
assumptions and obtain product purity information on a continuous
basis.
The locked-cycle test will also provide a significant quantity
of flotation product to allow crystalliser vendor testing and
design work, and also SOP product for product testing and
commercial purposes.
Conclusions
The work completed at SRC to date has shown:
-- Minimal comminution is required to liberate salts for flotation;
-- Kainite destruction achieves high conversion to schoenite in 2 hours at ambient conditions;
-- Both direct and reverse flotation provide viable flow sheet
options for further investigation;
-- Potassium recovery in flotation is high with up to 97.1% achieved in reverse flotation;
-- Both reverse and direct flotation options present the
opportunity to make a second saleable MgSO(4) product with minimal
additional processing;
-- SOP conversion produces high purity (>98%) SOP with a 1.5 hour residence time; and
-- Global potassium recovery for the process plant may be as
high as 92% depending on the flotation option and brine recycle
philosophy selected.
Further work is underway to further refine parameters to feed
into Pre-Feasibility Study level studies on both the commercial
operation and the pilot plant.
Competent Persons Statement
The information in this report that relates to Process Testwork
Results is based on, and fairly represents, information compiled by
Mr Bryn Jones, BAppSc (Chem), MEng (Mining) who is a Fellow of the
AusIMM, a 'Recognised Professional Organisation' (RPO) included in
a list promulgated by the ASX from time to time. Mr Jones is a
Director of Salt Potash Limited. Mr Jones has sufficient
experience, which is relevant to the style of mineralisation and
type of deposit under consideration and to the activity which he is
undertaking, 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'. Mr Jones consents to
the inclusion in the report of the matters based on his information
in the form and context in which it appears.
For further information please visit www.saltlakepotash.com.au
or contact:
Matt Syme/Sam Cordin Salt Lake Potash Limited Tel: +61 8 9322 6322
Colin Aaronson/Richard Tonthat/Daniel Bush Grant Thornton UK LLP (Nominated Adviser) Tel: +44 (0)207 383 5100
Nick Tulloch/Beth McKiernan Cenkos Securities plc (Broker) Tel: +44 (0) 131 220 6939
The information contained within this announcement is deemed to
constitute inside information as stipulated under the Market Abuse
Regulations (EU) No. 596/2014. Upon the publication of this
announcement, this inside information is now considered to be in
the public domain.
This information is provided by RNS
The company news service from the London Stock Exchange
END
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