Precious Metals Recovery LLC RCRA Permit Application Dry Hills ...

Step 3: Solid-Liquid separation (filter press).
Step 4: Filtrate treatment.
The calomel caustic leach circuit is designed as a batch operating process where poly drums of
calomel slurry will be transported with a forklift from the temporary calomel storage area to the
calomel feed preparation station. The calomel feed preparation station is designed to be a fully
automated and enclosed unit (see Figure 1.2-2).
Calomel slurry will be agitated to suspend the settled solids in the drum. Process water may be
added to the drum as needed to decrease the viscosity of the slurry and make it suitable for
pumping. When a homogeneous mixture is attained, the calomel slurry will be pumped from the
drum in the calomel feed preparation station to an agitated reaction tank (Decomposition Tank)
which contains a caustic solution of sodium hydroxide (NaOH). The caustic solution will
decompose calomel into a mixture of elemental mercury and mercuric oxide as per the following
reaction:
Hg2Cl2 (s) + 2 NaOH (aq) Hg⁰ (l) + HgO (s) + 2 NaCl (aq) + H2O (l)
After transferring calomel slurry to the Decomposition Tank, the drum will be triple rinsed in the
calomel feed preparation station, and the rinsed drum will be transported to a temporary storage
area. The drum rinsate will be added to the Decomposition Tank.
PMR RCRA Permit Application, Dry Hills Facility Page 20
JBR Environmental Consultants, Inc. | HATCH March 2013