High Purity Alumina
High Purity Alumina is an important co-product for the TECH Project; see below for links to each sub-section describing the benefits of TECH-produced High Purity Alumina:
Process Development
On behalf of QPM, our partners Lava Blue operated a demonstration plant for the digestion of aluminium hydroxide and crystallisation of ACH. These processing steps were as per the process design specified by technology equipment specialist KBR. For the resultant ultra high purity ACH, the demonstration plant used three-stage drying, decomposition, and calcination of ACH to produce 62kg of α-HPA for product development and marketing analysis.
The demonstration plant highlighted the extremely low concentration of impurities in the feed ACH through to HPA. Initial processing resulted in 99.995% purity HPA, with all impurities typically assaying < 1ppm, with the exception for Na (~10ppm), Ca (~ 4-5ppm) and Si (~3-7ppm). Further HPA production over a 3-month period resulted in a gradual trend toward higher purity from 99.995% to 99.998% as the process and equipment was bedded down.
Continued optimisations within the demonstration plant achieved additional rejection of Na, Ca, and Si, resulting in >99.999% HPA (5N), including being chloride free, matching world leading standards. The resultant HPA (unmilled) is D90 ~60 micron, which can be further processed (jet milled) to be tailored for off takers requirements. SEM, BET, SSA, XRD and other physical analyses can be provided upon request.
Recently, some of QPM’s HPA was manufactured into pills and subjected to thermal shock treatment leading to the formation of ultra high density alumina.
Ultra high-density alumina crackle and pills produced by QPM.
Process Description
QPM’s commercial High Purity Alumina (HPA) plant will operate continuously using concentrated hydrochloric (HCl) acid digestion of aluminium hydroxide (or other suitable precursor material) to produce aluminium chloride solution. Remaining (minor) unreacted solids will be removed by filtration.
The filtrate, containing the dissolved aluminium chloride is cooled to induce the crystallisation of ultra high purity aluminium chloride hydrate (ACH). The ACH is filtered, and impurities removed via washing of the crystals.
In the final stage, the ultra high purity ACH is washed with clean HCl and dewatered. The washed ACH is then fed into a two-stage drier and decomposer and then to a calciner which transforms ACH to HPA, which is finally converted to alpha phase HPA (α-HPA) in a calciner.
The HCl is recovered from the off gases and recycled back into the process. A general overview of the process is presented in the following schematic.
Product Specification
As part of our commitment to quality and excellence, QPM is seeking feedback from interested parties. Our initial pilot campaigns have produced a series of >4N5 (99.995% purity) and 5N (99.999% purity) HPA test samples, which have been branded as “AlumQ” (>4N) and “AlumQx” (5N).
QPM production will meet the following specifications for both product grades:
QPM/Lava Blue engaged Eurofins EAG Laboratories who prepared samples for non-destructive analysis. These samples were measured by glow discharge mass spectrometry (GD-MS).
The analysis results confirmed the 5N alumina purity with the low impurity levels of Na and Ca, providing further confidence in the process being developed by QPM and Lava Blue.
