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

The highly alkaline decomposed slurry and salt solution in the Decomposition Tank will be
pumped to a filter press (see Figure 1.2-3) for physical separation (see Appendix 1-C Process
Flow Diagrams). The filter press is designed with ventilation hoods that connect to the hygiene
exhaust system as discussed in Section 1.2.6.
The mercuric oxide filter cake will drop down the filter press chutes and be collected in drums
and will be retorted. The filtrate will be discharged into a neutralization tank (Waste Solution
Treatment Tank) where hydrochloric acid (HCl) will be added to neutralize the alkaline waste
solution into salt (NaCl) as per the following reaction:
NaOH (aq) + HCl (aq) NaCl (aq) + H2O (l)
A reagent (TMT 15, or functional equivalent) will be added to the Waste Solution Treatment
Tank, which will precipitate dissolved mercury and assist with the settling of other heavy metals
in a conical tank (Waste Solution Settling Tank) downstream in the waste solution treatment
circuit. The waste solution treatment circuit is discussed in more detail in Section 1.2.7. The
reagent material will be stored in the original vendor provided containers in the plant spaces.
All tanks as well as the calomel feed preparation station will be maintained under slight negative
pressure by localized ventilation systems which are discussed in Section 1.2.6. All tanks in the
calomel caustic leach circuit will be covered.
PMR RCRA Permit Application, Dry Hills Facility Page 22
JBR Environmental Consultants, Inc. | HATCH March 2013