Pueblo Viejo Refractory Gold Recovery: POX and CIL Process

Source: Barrick Mining Corporation (2026)
Website: https://www.barrick.com/English/operations/pueblo-viejo/default.aspx

Critical Data

Overview

Barrick Mining Corporation, in partnership with Newmont, operates the Pueblo Viejo gold mine in the Dominican Republic, one of the world’s largest refractory gold processing facilities. The plant processes approximately 14 Mtpa of run-of-mine and stockpiled refractory ore through an integrated recovery circuit that includes crushing, grinding, flotation, pressure oxidation (POX), and dual carbon-in-leach (CIL) cyanidation stages. The ore is refractory, meaning gold is locked within sulfide minerals, requiring oxidation before conventional cyanidation can achieve high recovery. The process begins with two parallel primary gyratory crushers reducing ore to a P80 of ~130 mm, followed by grinding in SAG and ball mill circuits targeting a P80 of 75 µm. A flotation circuit concentrates sulfide minerals and associated gold, which is then oxidized in four parallel autoclaves at 225°C and 3,100 kPaG using onsite-produced oxygen. The oxidized slurry undergoes hot curing, lime boiling, and CCD washing before entering the POX Discharge CIL (PDCIL) circuit. Flotation tailings are processed separately in the Flotation Tails CIL (FTCIL) circuit. Gold and silver are recovered from loaded carbon via Zadra elution, electrowinning, and smelting into doré bullion. The facility’s significance lies in its ability to treat complex refractory ores with high recovery rates while managing environmental impacts through effluent neutralization, cyanide destruction, and a dedicated effluent treatment plant. This state-of-the-art refractory gold ore processing plant exemplifies advanced extractive metallurgy applied to a world-class deposit.

Key Process Stages

• Stage 1: Crushing – Two parallel primary gyratory crushers (one 375 kW, one 450 kW) reduce ROM and stockpiled ore to a P80 of approximately 130 mm. Crushed ore is conveyed to adjacent coarse ore stockpiles and reclaimed via apron feeders for grinding.
• Stage 2: Grinding – Two parallel grinding lines: an SABC circuit (SAG mill 9,000 kW, ball mill 16,400 kW) and a single-stage SAG mill (23,000 kW). Both circuits include vibrating screens, pebble crushers, and hydrocyclones, targeting a product P80 of 75 µm.
• Stage 3: Flotation – Overflow from hydrocyclones feeds two parallel flotation trains, each with a surge tank, conditioning tank, and five 600 m³ flotation cells. Reagents (PAX, CuSO₄, guar gum, MIBC) promote sulfide mineral separation. Rougher concentrate returns to grinding; tailings go to FTCIL circuit.
• Stage 4: Pressure Oxidation (POX) – Four parallel autoclaves oxidize thickened flotation concentrate at 225°C and 3,100 kPaG (500 PSIG) for 60 minutes using high-purity oxygen (7,000 tpd total). The oxidized slurry is flash discharged, hot cured (>90°C for 12 hrs), and washed in a three-stage CCD circuit to remove sulfuric acid and metal sulfates.
• Stage 5: Cyanidation, Carbon Elution & Refining – The PDCIL circuit (11 agitated tanks with counter-current carbon) and FTCIL circuit (5 tanks) extract gold and silver using cyanide. Loaded carbon is acid-washed and stripped via the Zadra elution process. Pregnant solution undergoes electrowinning, and the sludge is retorted, fluxed, and smelted into doré bullion bars.

Additional Interesting Data and Summary

Beyond the main recovery circuit, the Pueblo Viejo plant integrates several critical ancillary systems that ensure process efficiency and environmental compliance. Three parallel oxygen production plants supply a total of 7,000 tpd of high-purity oxygen for the autoclaves, with oxygen consumption driven by sulfide concentration in the feed. Limestone and lime are produced onsite from quarried limestone: a gyratory crusher (820 tph), a SAG/ball mill grinding circuit (P80 60 µm) for fine limestone slurry used in neutralization, and vertical kilns for lime calcination. The lime boil stage uses excess lime at >85°C for 4.5 hours to break down jarosite and liberate entrained silver. Effluent neutralization treats CCD overflow containing >99% of dissolved metal sulfates and sulfuric acid via ferric precipitation tanks using limestone, followed by a high-density-sludge (HDS) circuit with lime. The HDS thickener overflow is cooled to <40°C and recycled. Cyanide destruction employs the INCO process (SO₂ with copper sulfate catalyst) on combined CIL tailings. An Effluent Treatment Plant (ETP) treats tailings effluent and mining area contact water, raising pH to 8.5 with lime/limestone, clarifying, and discharging to the Margajita River at a minimum rate of 1,655 m³/h. Water management includes abstraction from Hatillo Reservoir (max 3,200 m³/h) and reclaim water from the TSF (600–1,000 m³/h). Power is supplied at 230 kV stepped down to 34.5 kV, with a steady-state demand of ~210 MW and annual consumption of 1,740 GWh. Reagent consumption data is detailed: grinding media (0.7–1.4 kg/t), limestone (307–400 kg/t), lime (51–63 kg/t), cyanide (0.89–1.2 kg/t), and flotation reagents (PAX 140 g/t, CuSO₄ 100 g/t, etc.). The facility’s significance extends to its role in demonstrating sustainable refractory gold processing through integrated water recycling, onsite reagent production, and robust environmental controls. Future operations expect no significant changes to water streams, and the plant remains a benchmark for large-scale pressure oxidation technology.

Key Processes: Flotation, CIP/CIL, Cyanidation, SAG Mill, Ball Mill, Crushing

Target Commodities: Gold, Silver, Copper