Hi @Semmel ,
Further to today's recycling agreement announcement with Aurubis and our discussion on recycling, this is Talga's recycling patent application to be used in the process. It was published in January 2024.
WO2024003761A1 GRAPHITE MATERIAL PURIFICATION PROCESS 20220629
A graphite material purification process (10) comprising
a pelletisation step (14),
a caustic baking step (16) providing a sintered product,
a water leach step (18) whereby impurity minerals are solubilised, forwarded for effluent treatment, and separated,
a first sulphuric acid leach step (20) wherein remaining impurity minerals are solubilised, forwarded for effluent treatment, and separated from leach solids,
a hydrofluoric acid leach step (22) wherein partially leached impurity minerals are solubilised, forwarded for effluent treatment, and separated from leach solids,
a second sulphuric acid leach step (24) wherein impurity minerals not leached in previous steps and components precipitated in the hydrofluoric acid leach step (22) are solubilised, forwarded for effluent treatment, and separated from leach solids, and
washing stages wherein remaining soluble impurities are separated, and providing a purified graphite material (32).
[0055] The caustic baking step (ii) is undertaken at between about 150 and 300°C and causes the caustic soda and, in particular, silicate impurity minerals to react and be rendered soluble in water and mild acid conditions. The caustic baking step has a residence time in the range of about 60 to 240 minutes, for example about 120 minutes. The amount of caustic soda added to the graphite material to be purified is calculated using the ratio of at least 1 mol caustic to 1 mol silicon, for example between 2.5 to 5.5 moles caustic to silicon, particularly 3.2 mol caustic : 1 mol silicon. The caustic baking step (ii) is undertaken, for example, in a rotating kiln.
[0056] The water leach step (iii) is undertaken at between about 5-60°C, for example about 35°C ±5°C. The water leach step (iii) is undertaken in a single leach step, although in certain circumstances it may be undertaken in multiple, for example three, counter-current leach stages. The water leach step (iii) has a retention time of between about 30 to 240 minutes.
[0057] The first sulphuric acid leach step (iv) is undertaken at between about 5 to 60°C, for example about 40°C ±5 °C with a retention time of between about 30 to 240 minutes, for example about 120 minutes. Concentrated sulphuric acid is added in the first sulphuric acid leach step (iv). Impurities leached in the sulphuric acid leach step (iv) preferably include residual amounts of sodium silicate, sodium alunite, iron oxide and iron hydroxide, and titanium mineral phases not removed in step (iii). Still preferably, the residual free acid at the end of the first sulphuric leach step (iv) is in the range of 5-75 g/L H2SO4, for example about 50 g/L ±5 g/L H2SO4. The first sulphuric acid leach step (iv) preferably operates with between 5 to 25% solids, for example 10% solids.
[0058] Impurities leached in the first sulphuric acid leach step (iv) include sodium silicate, sodium alunite, iron oxide and iron hydroxide mineral phases formed during the caustic baking step, together with any residual caustic.
[0059] It is envisaged that all, or a portion of, the product of the first sulphuric acid leach step (iv) may be recycled to step (i) in order to expose it to a second baking step (ii). It is understood that this may be advantageous in addressing titanium levels, as the baking step (ii) is the stage of the process of the present invention in which titanium minerals are ‘cracked’ (eg. titanite and rutile).
[0060] The hydrofluoric acid leach step (v) is undertaken at between about 5- 60°C, for example about 40°C ±5°C. Impurities leached in the hydrofluoric leach step (v) include but are not limited to quartz, titanium mineral phases, and residual amounts of albite, biotite, and pyrophyllite. The residual free acid at the end of the hydrofluoric acid leach step (v) is in the range of about 5-75 g/LHF, for example about 25 g/L ±5 g/L HF. The hydrofluoric acid leach step (v) operates with between 5 to 25% solids, for example 10% solids. [0061] The hydrofluoric acid added to the acid leach step (v) is in the range of about 20 to 70% concentration. The hydrofluoric acid concentration in the acid leach step (v) is preferably in the range of 15-50 g/L, depending on the grade and mineralogical composition of the starting graphite material. The leach solids from the hydrofluoric leach step (v) have substantially no, or only trace amounts of, silicon remaining therein.
[0062] The second sulphuric acid leach step (vi) is undertaken at between about 5-60°C, for example about 40°C ±5°C. Impurities leached in the second sulphuric acid leach step (vi) include precipitated fluoride phases, for example calcium fluoride, and remaining base metals. The second sulphuric acid leach step (vi) operates with between 5 to 25% solids, for example 10% solids. The second sulphuric acid leach step (iv) has a retention time of between about 30 to 240 minutes, for example about 120 minutes.
[0063] Concentrated sulphuric acid is added in the second sulphuric acid leach step (vi). The residual free acid at the end of the second sulphuric leach step (iv) is in the range of 5-75 g/L H2SO4, for example about 50 g/L ±5 g/L H2SO4. Acid solutions from the second sulphuric acid leach step (vi) are recovered and recycled to the first sulphuric acid leach step (iv) and the second sulphuric acid leach step (vi).
Further to today's recycling agreement announcement with Aurubis and our discussion on recycling, this is Talga's recycling patent application to be used in the process. It was published in January 2024.
WO2024003761A1 GRAPHITE MATERIAL PURIFICATION PROCESS 20220629
A graphite material purification process (10) comprising
a pelletisation step (14),
a caustic baking step (16) providing a sintered product,
a water leach step (18) whereby impurity minerals are solubilised, forwarded for effluent treatment, and separated,
a first sulphuric acid leach step (20) wherein remaining impurity minerals are solubilised, forwarded for effluent treatment, and separated from leach solids,
a hydrofluoric acid leach step (22) wherein partially leached impurity minerals are solubilised, forwarded for effluent treatment, and separated from leach solids,
a second sulphuric acid leach step (24) wherein impurity minerals not leached in previous steps and components precipitated in the hydrofluoric acid leach step (22) are solubilised, forwarded for effluent treatment, and separated from leach solids, and
washing stages wherein remaining soluble impurities are separated, and providing a purified graphite material (32).
[0055] The caustic baking step (ii) is undertaken at between about 150 and 300°C and causes the caustic soda and, in particular, silicate impurity minerals to react and be rendered soluble in water and mild acid conditions. The caustic baking step has a residence time in the range of about 60 to 240 minutes, for example about 120 minutes. The amount of caustic soda added to the graphite material to be purified is calculated using the ratio of at least 1 mol caustic to 1 mol silicon, for example between 2.5 to 5.5 moles caustic to silicon, particularly 3.2 mol caustic : 1 mol silicon. The caustic baking step (ii) is undertaken, for example, in a rotating kiln.
[0056] The water leach step (iii) is undertaken at between about 5-60°C, for example about 35°C ±5°C. The water leach step (iii) is undertaken in a single leach step, although in certain circumstances it may be undertaken in multiple, for example three, counter-current leach stages. The water leach step (iii) has a retention time of between about 30 to 240 minutes.
[0057] The first sulphuric acid leach step (iv) is undertaken at between about 5 to 60°C, for example about 40°C ±5 °C with a retention time of between about 30 to 240 minutes, for example about 120 minutes. Concentrated sulphuric acid is added in the first sulphuric acid leach step (iv). Impurities leached in the sulphuric acid leach step (iv) preferably include residual amounts of sodium silicate, sodium alunite, iron oxide and iron hydroxide, and titanium mineral phases not removed in step (iii). Still preferably, the residual free acid at the end of the first sulphuric leach step (iv) is in the range of 5-75 g/L H2SO4, for example about 50 g/L ±5 g/L H2SO4. The first sulphuric acid leach step (iv) preferably operates with between 5 to 25% solids, for example 10% solids.
[0058] Impurities leached in the first sulphuric acid leach step (iv) include sodium silicate, sodium alunite, iron oxide and iron hydroxide mineral phases formed during the caustic baking step, together with any residual caustic.
[0059] It is envisaged that all, or a portion of, the product of the first sulphuric acid leach step (iv) may be recycled to step (i) in order to expose it to a second baking step (ii). It is understood that this may be advantageous in addressing titanium levels, as the baking step (ii) is the stage of the process of the present invention in which titanium minerals are ‘cracked’ (eg. titanite and rutile).
[0060] The hydrofluoric acid leach step (v) is undertaken at between about 5- 60°C, for example about 40°C ±5°C. Impurities leached in the hydrofluoric leach step (v) include but are not limited to quartz, titanium mineral phases, and residual amounts of albite, biotite, and pyrophyllite. The residual free acid at the end of the hydrofluoric acid leach step (v) is in the range of about 5-75 g/LHF, for example about 25 g/L ±5 g/L HF. The hydrofluoric acid leach step (v) operates with between 5 to 25% solids, for example 10% solids. [0061] The hydrofluoric acid added to the acid leach step (v) is in the range of about 20 to 70% concentration. The hydrofluoric acid concentration in the acid leach step (v) is preferably in the range of 15-50 g/L, depending on the grade and mineralogical composition of the starting graphite material. The leach solids from the hydrofluoric leach step (v) have substantially no, or only trace amounts of, silicon remaining therein.
[0062] The second sulphuric acid leach step (vi) is undertaken at between about 5-60°C, for example about 40°C ±5°C. Impurities leached in the second sulphuric acid leach step (vi) include precipitated fluoride phases, for example calcium fluoride, and remaining base metals. The second sulphuric acid leach step (vi) operates with between 5 to 25% solids, for example 10% solids. The second sulphuric acid leach step (iv) has a retention time of between about 30 to 240 minutes, for example about 120 minutes.
[0063] Concentrated sulphuric acid is added in the second sulphuric acid leach step (vi). The residual free acid at the end of the second sulphuric leach step (iv) is in the range of 5-75 g/L H2SO4, for example about 50 g/L ±5 g/L H2SO4. Acid solutions from the second sulphuric acid leach step (vi) are recovered and recycled to the first sulphuric acid leach step (iv) and the second sulphuric acid leach step (vi).
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