NI43-101Pre-Feasibility Study Report - page 187

Rare Element Resources
Bear Lodge Project
Canadian NI 43-101 Technical Report
October 9
, 2014
10135-200-46 - Rev. 0
The rare earth (RE) metals plus thorium are selectively precipitated from the pregnant
leach solution (PLS) using oxalic acid while all the base metals, including uranium,
remain in the barren PLS. Rare earth oxalate precipitates are dried and roasted to
produce a +97% pure mixed REO powder.
Bulk REO powder or RE carbonate solids are dissolved in nitric acid to generate a
bulk RE nitrate solution containing thorium that serves as feed to the thorium
extraction plant. A double hydroxylation process is applied to extract thorium
selectively from RE nitrates. The thorium hydroxide residue is contained and
transported to a third-party disposal facility while the pure RE nitrate solution is
subjected to a final precipitation process to produce RE hydroxide solids. The RE
hydroxide cake is dried and calcined at moderate temperature to produce a
marketable +97% mixed REO powder.
13.3.5 Acid and Water Recovery
The barren PLS is a source of significant amounts of reagents (free hydrochloric and
oxalic acid) , water and base metals. Therefore, a distillation process is applied to
recover water and hydrochloric acid at atmospheric pressure. Energy costs
associated with boiling water are mitigated by a cheaper energy source (natural gas)
and a heat recovery system that is coupled to the distillation column. Residual
solution from the column is pumped through a chiller to crystallize and recover
unreacted oxalic acid.
13.3.6 Neutralization and Base Metal Recovery
The metal-rich liquor from the distillation column is neutralized with limerock and
small amounts of quicklime to produce a mixed base metal hydroxide cake. This cake
is then mixed with the leach residue, dewatered and transported to the double lined
tailing storage facility.
The filtrate is passed through a chiller to crystallize calcium as CaCl
crystals with
smaller amounts of NaCl crystals. The final filtrate, with few metal ions, is recycled to
the distillation column for water recovery. The metallurgical plant is designed to run
without effluent discharge to the environment.
13.4 Overall Rare Earth Recovery Used in Economic Evaluation
In this PFS, overall rare earth recovery was calculated by combining individual
recoveries from the PUG and Hydromet plants.
13.4.1 Screening and PUG Recovery
In years 1-9, the recovery of rare earth oxides (REOs) to the mineral pre-concentrate
is based on ore passing the 3 inch cut-off size and the rejection of coarse material
1...,177,178,179,180,181,182,183,184,185,186 188,189,190,191,192,193,194,195,196,197,...587
Powered by FlippingBook