Rare Element Resources
Bear Lodge Project
Canadian NI 43-101 Technical Report
October 9
th
, 2014
10135-200-46 - Rev. 0
17-14
17.3 Process Description Unit 200 – Hydromet Plant Leach
Figures 17.9 thru 17.32, Roche, 2014 are Block Flow Diagrams which illustrate the
Hydromet Plant Process Flows.
The Leach Unit is designed to leach the rare earth compounds from the pre-
concentrate material using hydrochloric acid in a counter current two-stage process.
Upon arrival at the Hydromet plant, the pre-concentrate transport trucks are emptied
in the underground chute (200-CHU-001). From the bottom of the chute an ore apron
feeder (200-APF-001 discharges onto an inclined conveyor (200-CVO-001) to the top
of the pre-concentrate feed silos (200-SIL-001A/B). The pre-concentrate is then
conveyed (200-CVO-002 & 003) to the leach slurry surge tank (200-TAK-001). (In
Phase I, the minus 3” ore is fed to a ¾” cone crusher (110-CCR-001) and through the
wet grinding and screening circuit down to minus 48 mesh size). Recycled water (acid
water) from the HCl recovery process is also added to the leach slurry surge tank to
make a 40% solid slurry. The dust generated in the conveying process is controlled
using bin vents and bag houses with standard cartridges at every transfer / drop
point.
The leach reactors are organized in 2 rows of 3 agitated reactors in series (200-REA-
001 – 006). Each row operates as two independent stages. The slurry flows through
the leach reactors by overflow. Any one of the three leach tanks may be taken out of
service and bypassed for maintenance. The remaining two leach tanks are sized to
provide the required residence time of 4 hours. Pre-concentrate 65% solids slurry
from the leach slurry surge tank is pumped to the first stage of leach reactors and
combined with the filtered leach solution from the second leach reactor stage to
formulate a 22% solids slurry. The overflow from the 3rd leach reactor is filtered
(PLS) and sent to the oxalate reactors (300-REA-001,2,3,4). Fresh 35% HCl, 18%
recovered HCl, and acid water as needed is combined with the filtered solids from the
first leach reactor stage to formulate a 24% solids slurry feed to the second leach
reactor stage (200-TAK-004).
Two belt filters running in parallel are required for each stage to handle the volume of
solids that need to be filtered. A spare leach reactor solids 2 belt filter system has
been included in the design for a total of six belt filters. (200-BLF-001A/B, 200-BLF-
002A/B, 200-BLF-003A/B). Also, as a general practice, all slurry and liquid pumps
will be in duplicate with the second pump on standby as a spare. The extra
equipment is included to minimize process down time and maximize the on-line
operating factor for the Hydromet plant.
