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Thermal process engineering: graphite, lithium, vanadium and cobalt

The recent advent of the electric vehicle and battery markets has seen the global mining industry move with speed to acquire and develop graphite, lithium, vanadium and cobalt projects – driving this entire sector of the market into a booming growth phase.

These commodities require unique processing requirements and this demand has seen Drytech International quickly evolve its business model to cater to this sector.

Drytech delivers thermal process engineering expertise that, in addition to its conventional drying technologies, now includes applications which require thermal input for chemical reactions, says MD Ryan Carpenter.

AUTHOR: Editor of Mining Review Africa, Laura Cornish

Drytech International’s (Drytech) current work portfolio reflects not only recent trends in those areas with a developed mining sector, but also those regions whose mining sectors are in a state of growth.

This article first appeared in Mining Review Africa Issue 7, 2018

“All of our business at present is focused on work beyond South Africa’s border as the country continues to shy away from major capital investments.

“In addition, the demand for battery metals is also booming and we are taking on the number of enquiries and projects in this niche market sector,” Carpenter reveals.

The situation has required Drytech to adapt its business, which has focused primarily on thermal drying solutions since its establishment in 1981.

“We are quickly expanding our capabilities to include thermal process engineering – a vital component in the graphite/lithium/vanadium/cobalt and high purity alumina space.”

As it looks to build a solid track record of successful installations across this suite of commodities, the company is working closely with an Australia-based research company and at home is conducting extensive test work with its own pilot-scale plants and 3D computerised modelling technology.

This has already seen it install and commission drying equipment for Syrah Resources’ large-scale Balama graphite project in Mozambique – a 44 tph fines flash dryer and a 12.5 tph flakes flash dryer.

Further to this the company is now working to deliver a similar solution for other players in this sector.

Judging by its portfolio of projects currently in negotiation, design or execution phase, the company’s footprint will extend across the globe and currently includes operating installations in tungsten, vanadium, lithium, high purity alumina and bauxite and even diatomaceous earth.

Understanding graphite’s thermal requirements

Graphite value lies in its particle/flake size – coarse flakes are worth substantially more than fines graphite.

The final export product is required to be dried after undergoing the necessary hydro-metallurgical processes.

“Our drying solution, tried and tested at Balama, has proven that we can dry the material with minimal particle degradation,” Carpenter discusses.

The optimal solution for achieving this is flash drying technology which encompasses a pneumatic system to eliminate spillage.

The dry product can also be placed at the beginning of the final screening and bagging process, thus eliminating additional material handling steps.

“And because of the shape of the graphite coarse and fine flakes, our disintegrator doesn’t cause additional degradation of the particles but merely breaks up the filter cake exposing the product’s maximal surface area to air flow.

“This improves the overall thermal efficiency of the drying process.”

Another plus is their maintenance requirements which are minimal and therefore ideally suited to African conditions.

Rotary dryers are an alternative option Carpenter continues and while particle degradation is also minimal, it does offer others challenges around material sticking at the entrance of the dryer.

Dusting can be another challenge. Graphite is lightweight, easily air-born and if leaked from the dryer will coagulate on the outside and become very slippery.

“In essence, our expertise has evolved beyond the thermodynamics of drying, as we must understand the material handling aspects of how our dryers handle the material.

“And because the market is hard pressed to find experts in the field generally, we are working to establish ourselves as a leader in this field by taking the risk in designing customised processing solutions.”

Understanding the complexity for lithium

Drytech is also involved with test work on sulphation roasting for lithium.

“Producing lithium is a chemically intensive process and requires greater understanding of the chemical composition of spodumene and how best to extract the lithium from its host material,” Carpenter explains.

Lithium processing involves numerous thermal and chemical processing steps.

One area of extracting of lithium involves the sulphation roasting of the host material – sulphation roasting creates the right environment to precipitate lithium sulphate which can afterwards be used to further precipitate lithium carbonate on the route to obtain a final lithium product.

“Understanding these processes and conducting extensive pilot plant scale test work is essential for our up and coming lithium miners across the globe and our objective is to develop a sound understanding of lithium chemistry which in turn will enable us to deliver optimal thermal processing solutions for the product.”

Cobalt hydroxide

Cobalt forms part of the current surge in demand for Lithium ion battery manufacturers and has seen a significant increase in market prices over the last 2 years.

This is driving demand to develop cobalt hydroxide processing facilities.

Drytech has again undergone extensive test work on drying this material and has developed tailored large-scale flash drying solutions to be ideally suited to the product, as opposed to the smaller scale spin flash drying option.

Flash dryers can also accommodate significantly higher volumes than spin flash drying – which is better suited to large-scale tonnages which are in greater demand as the value of cobalt continues to climb.

Drytech is in the execution phase for three of the largest known cobalt hydroxide flash dryers projects currently under development in the market.

This article first appeared in Mining Review Africa Issue 7, 2018

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