NI43-101Pre-Feasibility Study Report - page 226

Rare Element Resources
Bear Lodge Project
Canadian NI 43-101 Technical Report
October 9
, 2014
10135-200-46 - Rev. 0
13.7 Conversion of Rare Earth Oxalates
A kiln has been found to provide the most economic conversion of Rare Earth
oxalates to rare earth oxides. At 700°C the rare earth oxalates are decomposed
releasing CO2 and converting the rare earths to oxides. In bench scale and pilot
testing, this was found to function satisfactorily.
In pilot testing, the average composition of the kiln discharge was 74.1% TREE (71%
LREE and 3.1% HREE). Thorium levels were between 1.0% and 3.1% with uranium
levels below 70 g/t. Carbon concentrations in the kiln discharge solids were around
0.6% once the operation was steady. The base metals in the kiln discharge solids
were below 1% with the exception of silicon, which was as high as 8%, though this
was not related to the kiln operation but rather to the precipitation circuit operation.
13.8 Acid/Water Recovery
Acid Recovery and Oxalic Acid Crystallization
The barren PLS was vaporized to recover a mixture of acid and water (Azeotropic
conditions) under a vacuum (-21 inches Hg) and 87 °C.
The mixed vapor was selectively condensed in order to split acid (HCl) and water
O) streams.
Total acid recovered to the azeotropic acid and water streams ranged from 19 to
58% (average 33%), depending on the feed rate. Low acid recovery was
attributed to initial lower acid concentration in the feed to the distillation column.
The residual solution at the bottom of the distillation column was passed through
a chiller. Oxalic acid crystals were recovered from the chiller containing 87.5%
oxalate, 0.2% TREE and 5% Ca.
The filtrate from the chiller contained several metal ions including 1.8 g/L TREE,
22 g/L Ca and 19.7 g/L Fe and 13.9 g/L Mn. This filtrate was subjected
neutralization with lime rock and quicklime to precipitate all base metals.
Figure 13.16 shows a photograph of the pilot distillation column used for distilation
testing at SGS Lakefield.
1...,216,217,218,219,220,221,222,223,224,225 227,228,229,230,231,232,233,234,235,236,...587
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