Curipamba-El Domo: SAB Comminution Paired With Two-Stage Regrinding in Ecuadorian Polymetallic Plant

The planned 666 ktpa processing plant at the Curipamba-El Domo project in central Ecuador will use a single-stage open-circuit crushing step followed by SAG and ball milling, with a two-stage regrind circuit designed to handle the deposit's ultra-fine-grained sulphide mineralisation.

Critical Data

Overview

The Curipamba-El Domo project sits in Bolívar Province, central Ecuador, roughly 150 km from Guayaquil. This is a planned open pit operation, 75% owned by Silvercorp Metals Inc. and 25% by Salazar Resources Ltd., with construction of related facilities and infrastructure under way and permits for construction in place. The target commodities are copper, gold, silver, lead, and zinc from a volcanogenic massive sulphide deposit. The mine plan provides for a 13-year life of mine starting January 2026, with about 1.5 years of construction and pre-production followed by 11.5 years of commercial operation.

The processing plant has a nominal design capacity of 666 ktpa and treats ore from the open pit. DRA Global Ltd. prepared the feasibility study in December 2021, and Yantai Oriental Metallurgical Engineering Co., Ltd. completed the preliminary design in February 2026. The plant runs continuously for 330 days per year with two 12-hour shifts per day, while the crushing system works two shifts per day at 6 hours per shift.

Designed final products are copper concentrate at 25.35% Cu, zinc concentrate at 53.50% Zn, and lead concentrate at 20.65% Pb. Gold and silver are distributed among these three concentrates for overall recovery.

Key Process Stages

The flowsheet shows decisions made during the preliminary design phase that depart from the earlier feasibility study in several respects. DRA's study called for two-stage closed-circuit crushing followed by single-stage closed-circuit grinding, with crushing product at 18 mm and grinding fineness at 80% passing 125 μm. The Yantai Oriental design uses single-stage open-circuit crushing plus a SAB configuration. The crushing product size is P80 = 150 mm with the same grinding fineness of 80% passing 125 μm. SRK notes that with an open pit operation and high wet-season rainfall, slime in the ore stream is unavoidable, and a conventional multi-stage crushing circuit is more prone to blockages that disrupt production. The SAB process offers a simpler flowsheet and more compact plant layout, reducing material handling and intermediate storage.

Run-of-mine ore is dumped into the coarse ore bin, or hauled to the ROM stockpile and rehandled by wheel loader. A fixed grizzly with 500 by 500 mm apertures sits on top of the bin, and oversized rock is broken by a mobile hydraulic rock breaker. One GBZ1858 heavy-duty apron feeder withdraws ore to a C106 jaw crusher. The crushed product travels by belt conveyor to an intermediate stockpile.

Material from the intermediate stockpile moves via three GBZ12-6 apron feeders onto a belt conveyor that delivers it to a Φ5.03 by 2.8 m SAG mill. SAG mill discharge goes to a 2ZKR2052 linear vibrating screen with 5 mm apertures. Screen undersize pumps to a cluster of FX500 by 6 hydrocyclones, with four operating and two on standby. Cyclone overflow passes through a ZKR2052 trash screen and flows by gravity to flotation. Cyclone underflow goes to a Φ3.6 by 6.5 m overflow ball mill, with ball mill discharge returning to the cyclone feed pump box. Primary grinding produces P80 = 125 μm at a slurry density of 30% solids. Space is reserved in the grinding circuit for a Knelson centrifugal gravity concentrator.

The flotation area combines several flotation columns and mechanical cells in a sequence designed for the ore's fine-grained character. The classified overflow feeds a CT-3 by 12 flotation column for first-stage copper-lead preferential rougher flotation. Column tailings flow by gravity to four XCF/KYF-30 air-inflation cells for the second rougher stage. Combined concentrates from both rougher stages go to a CT-2 by 9 flotation column for cleaning. Cleaner tailings pass through a Φ2500 by 2500 mm agitated tank for reagent conditioning, then to two XCF/KYF-30 cells for cleaner-scavenger flotation. The cleaner-scavenger concentrate joins the cleaner concentrate to form the copper-lead preferential 1# concentrate, which pumps either to copper-lead separation or directly to the copper concentrate thickener.

Second rougher tailings from the preferential stage are conditioned and flow to three XCF/KYF-30 air-inflation cells for bulk flotation roughing. Rougher tailings undergo two stages of scavenger flotation. When oxidized zinc minerals are present, copper sulfate and other reagents are added to the second scavenger cells, and that scavenger concentrate reports to the rougher stage of zinc-sulfur separation. Otherwise the final bulk flotation tailings pump to a Φ20 m high-efficiency thickener. Bulk rougher concentrate passes through a Φ3000 by 3000 mm agitation tank for defoaming, then joins cleaner-scavenger tailings from the preferential flotation at the bulk concentrate regrind circuit.

The regrind system uses two stages with classification between them. The first stage is a VGX-1000 vertical mill in closed circuit with a cluster of FX200 by 12 hydrocyclones producing P80 = 25 μm. That product classifies again through FX100 by 18 hydrocyclones. Underflow goes to an SMD-355 stirred mill operating in open circuit. Stirred mill discharge and second-stage cyclone overflow report to the copper-zinc separation flotation circuit. Final regrind fineness is P80 = 15 μm.

The regrind product is conditioned with reagents and pumped to a CT-5.5 by 12 flotation column for first-stage rougher flotation. Column tailings flow to four XCF/KYF-30 cells for the second rougher stage, and those tailings flow to zinc-sulfur separation. Combined rougher concentrates feed a CT-3 by 9 flotation column for cleaning. Cleaner tailings pump to a cluster of FX75 by 12 hydrocyclones for thickening and classification, with underflow returning to the SMD-355 stirred mill and overflow going back to the rougher conditioning tank.

Concentrates from the preferential flotation and from copper-zinc separation cleaning enter the copper-lead separation circuit with one-stage roughing and one-stage cleaning. Rougher tailings are the copper concentrate and pump to a Φ20 m high-efficiency thickener. Cleaner concentrate is the lead concentrate and goes to a Φ3.6 m lead concentrate thickener.

The zinc-sulfur separation circuit receives scavenger tailings from copper-zinc separation plus the second scavenger concentrate from the bulk flotation stage. The flowsheet uses two-stage roughing, one-stage cleaning, and one-stage scavenging. Cleaner concentrate is the zinc concentrate, pumped to a Φ15 m zinc concentrate thickener. First scavenger tailings pump to a Φ18 m tailings thickener.

For dewatering, the copper concentrate thickener underflow goes through one TPS38/38M45 and one HDLY/Ⅱ-36 vertical automatic filter press. Lead concentrate uses one HDLY/Ⅰ-9 vertical automatic filter press. Zinc concentrate uses one TPS26/26M45 vertical automatic filter press. The dewatered concentrates are packed into one-tonne bags by an automatic bagging machine and stored by forklift.

Bulk flotation tailings thicken in a Φ20 m high-efficiency thickener to 50% solids. Zinc tailings thicken in a Φ18 m unit, also to 50% solids. Both streams pump separately by slurry pumps to the tailings storage facility. The tailings pipelines are HDPE laid along the ground surface, with steel casing pipes buried where they cross roads. The final dam crest elevation of the TSF is +830 m. The ground elevation at the concentrator tailings pump station is +941 m, and the horizontal distance from the tailings pumps to the dam shoulder is roughly 1,800 m.

Additional Interesting Data and Summary

The design draws on metallurgical testwork from BML and GRINM, with adjustments based on operating data from comparable plants in the region. The indicators represent life-of-mine averages and will vary with feed grade and lithology. Copper and zinc concentrates are saleable products with gold and silver credits, though payability is less favourable for gold and silver in the zinc concentrate. The lead concentrate has a relatively low lead grade and high copper content, and the report describes its marketing as not positive, though it carries a significant gold and silver credit.

Approximately 34% of gold and 26% of silver losses occur in the zinc rougher tailings. The preliminary design selected a mechanical cell-column combined flotation scheme over an all-mechanical arrangement, balancing separation efficiency and operating costs against the local availability of skilled flotation operators.

The processing plant layout uses a linear, I-shaped configuration for crushing, grinding-flotation, and dewatering. Gravity flow is adopted wherever practicable. The plant includes a ROM stockpile, ROM bin, crushing plant, crushed ore stockpile, grinding and flotation plant, concentrate thickeners and dewatering plant, concentrate storage, tailings thickeners, a high-level process water tank, fuel and oil storage, blower house, generator room, mechanical workshop, reagent storage, materials warehouse, laboratory, and administrative building.

Water supply for the concentrator comes primarily from stream flow in a gully approximately 3 km northwest of the plant. Backup sources are treated effluents from the EWTP1 tailings storage facility water treatment plant and the EWTP2 open pit water treatment plant. Both primary and backup sources pump to an inclined-plate thickener, with clarified water used as process water. One high-level fresh water tank provides 800 m³ of capacity. Reclaimed water includes plant reclaim water from thickener overflow and filter press filtrate, plus TSF reclaim water. Two high-level reclaim water tanks each hold 2,000 m³. TSF water undergoes natural settling and is pumped from a floating pontoon station through an intermediate tank back to the concentrator.

Power comes from a 69/13.8 kV substation southwest of the plant feeding the concentrator's 13.8 kV/0.48 kV substation. The 13.8 kV vertical mill, SAG mill, ball mill, and reclaim water pontoon pumps are high-voltage consumers. During initial production, high-voltage diesel generator sets supply power, with the external 69 kV grid intended to take over and the generators retained as backup. The MCC is adjacent to the grinding-flotation building with three transformers supplying low-voltage power and lighting.

Ventilation and dust control include independent mechanical exhaust systems in laboratories, assay rooms, and reagent storage. Spray dust suppression is installed at dust-prone locations, and floors are washed once per shift. Dust-tight enclosures with dust collectors are provided at material transfer points.

Key Processes

• Single-stage open-circuit jaw crushing with grizzly scalping
• SAG and ball mill grinding in SAB configuration
• Partial preferential copper-lead flotation using columns and mechanical cells
• Copper-lead-zinc bulk flotation with two-stage scavenging
• Two-stage regrinding from 125 μm to 25 μm to 15 μm using vertical and stirred mills
• Copper-zinc separation flotation
• Copper-lead separation flotation
• Zinc-sulfur separation flotation
• Concentrate thickening and pressure filtration dewatering
• Tailings thickening to 50% solids and pumping to tailings storage facility

Source: Technical Report on Curipamba-El Domo Polymetallic Project, in Ecuador, Dec. 31, 2025. Project website: Curipamba-El Domo