BobGreenfield wrote: Canada Carbon made it clear today, Thermal was an immensley better approach to upgrading than caustic bake. Miller concentrate was already Nuclear purity, thermal upgrading performed better in every metric than caustic bake, that's obvious.
TD: What would you call the process that requires chemicals or acids to achieve high purity, greater than 99%?
OP: This approach is referred to as a hydrometallurgical process. Two common routes are a hydrofluoric (HF) leach process or a caustic bake. In addition, a graphite flotation concentrate can also be upgraded through electro-thermal purification. So there are different routes.
TD: So there are two routes to pursue when a graphite company is attempting to achieve ultra high purity?
OP: There are two main processing routes — chemical and electro-thermal purification. I’ve mentioned two chemical purification methods before, but there are other options and with the revived focus on graphite in recent years. More process development in the hydrometallurgical field is currently being conducted.
TD: Do all two high-purity paths that can be pursued all involve acid?
OP: Not the electro-thermal. Electro-thermal purification exposes graphite materials to temperatures up to 3,000°C to remove any impurities.
TD: Is the electro-thermal process a more expensive path? Meaning is it something that would be less likely to be commercially viable on a larger scale?
OP: Well, for example, one of the North-American major off-takers for graphite employs electro-thermal purification on a commercial scale — so it is definitely viable. The more economically attractive route will depend on many factors such as the location of the deposit, on the flake-size distribution, the amenability of the flakes to purification, and the maximums grade that can be achieved with flotation only. Both purification routes are not cheap and that’s why flotation is essential to upgrade the ore from 2% to 25% carbon head grade to the maximum grade that you can achieve before introducing the chemical or electro-thermal purification. Every impurity that has to be removed by the purification process is going to cost substantially more money compared to flotation.
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