How to Select a Carbon-in-Pulp (CIP) Plant for Carlin-Type Gold Deposits? Complete CIP/CIL Equipment and EPC Turnkey Solutions

In short: A carbon-in-leach (CIL) plant for Carlin-type gold deposits does not “directly leach the raw ore,” but rather “processes flotation concentrates (or pretreated material).” The first step in plant design is to determine the pre-treatment route; the second step is to configure the CIP/CIL equipment.

Route 1: Flotation concentrate → Pretreatment → Cyanidation (CIP/CIL)

Applicable to: Typical Carlin-type ores containing arsenic, carbon, and finely dispersed, encapsulated particles.

Process Logic: Crushing and grinding (fine grinding to achieve single-particle liberation of sulfides)→ Flotation to concentrate gold-bearing sulfides (carbon-bearing ores require suppression of carbon-rich materials) → Concentrate pretreatment (proprietary reagents/roasting/pressurized oxidation/biological oxidation/chemical oxidation) → Cyanide leaching → CIP/CIL adsorption → Desorption electrolysis → Gold slime smelting.

Key Considerations for Process Selection: The pretreatment method is the core variable. Roasting, pressurized oxidation, and bio-oxidation vary significantly in capital and operating costs and must be determined through pilot testing; the grade of the flotation concentrate and the sulfur recovery rate directly impact the economic viability of subsequent pretreatment.

Route 2: Flotation Concentrate → Direct Cyanidation (CIP/CIL)

Applicable to: Ore with low encapsulation and acceptable leaching rates after pretreatment, or cases where gold can be partially liberated after fine grinding of the flotation concentrate.

Process Logic: Flotation enrichment → Concentrate regrinding → Cyanide leaching → CIP/CIL adsorption → Desorption electrolysis.

Key Considerations: Pilot testing is required to confirm whether direct leaching of the concentrate is economically viable; the fineness of the concentrate regrinding is a critical parameter.

Route 3: Raw Ore Pretreatment → Whole-Slurry Cyanidation (CIP/CIL)

Applicable to: Ore containing carbonaceous material that causes gold entrapment but where the gold is not deeply encapsulated.

Process Logic: Crushing and grinding of raw ore → Pretreatment to eliminate the gold-capture effect (e.g., suppression of carbon-bearing materials, passivation treatment) → Whole-slurry cyanidation → CIP/CIL → Desorption electrolysis.

Key Considerations for Selection: Pretreatment must be highly targeted, and the effectiveness of eliminating the gold-sequestration effect must be verified through testing.

Core Principle: When selecting a carbon-in-leach plant for Carlin-type gold deposits, it is essential to first conduct ore characterization and pre-treatment tests to determine the pre-treatment route and leaching parameters based on data before discussing CIP/CIL equipment configuration. Skipping pre-treatment and proceeding directly to carbon-in-leach equipment selection is the biggest mistake in Carlin-type mine design.

1. Crushing and Grinding Stage—Fine grinding is a prerequisite for liberation

• Crushing: Jaw crusher for coarse crushing + cone crusher for medium and fine crushing, following the principle of “more crushing, less grinding”;
• Grinding: Ball mills (two-stage grinding: grid type + overflow type) in a closed circuit with hydrocyclones, grinding to achieve individual liberation of gold-bearing sulfides;
• Key Selection Criteria: Carlin-type ores have a fine grain size distribution and require high grinding fineness; the mill specifications and classification efficiency directly determine the effectiveness of flotation and leaching.

2. Flotation Circuit (specific to Carlin-type ores) — Enrichment of gold-bearing sulfides

• Floating machines: SF type (self-aspirating), XCF/KYF type (air-agitated, preferred for large-scale operations), BF type, and JJF type, configured into roughing, scavenging, and cleaning units;
• Reagent Regimen: Collectors, frothers, pH adjusters, and inhibitors (to suppress carbon-bearing materials in carbon-bearing ores and arsenopyrite in arsenic-bearing ores, or for the separate flotation of arsenic-gold concentrate);
• Key Considerations for Selection: The number of flotation stages and the reagent regime determine the concentrate grade and sulfur recovery rate, directly affecting subsequent pretreatment costs.

3. Pretreatment Stage—Unwrapping and Eliminating Interferences

• Method Selection: Proprietary chemical pretreatment, roasting, pressurized oxidation, biological oxidation, or chemical oxidation—determined based on ore properties and test data;
• Key Considerations: Pretreatment accounts for the lion\'s share of capital and operating costs for Carlin-type ores; the economic viability of different methods must be evaluated through comparative testing. Carbon-bearing ores must be passivated or have their carbonaceous matter removed prior to leaching.

4. Leaching and Adsorption Section—The Core of CIP/CIL

• Leaching Tanks: Equipped with agitation and aeration; multiple tanks connected in series; cyanide and lime are added to adjust the pH to 10–11;
• Activated Carbon Adsorption System: CIL employs simultaneous leaching and adsorption (compact process), while CIP uses sequential leaching followed by adsorption (allowing for precise segmented control); activated carbon concentration and management of gold-loaded carbon are critical;
• Gold-Loaded Carbon Separation Screen: Carbon retention screen/air lift to prevent carbon loss;
• Design Considerations: Matching leaching and adsorption times, the number of tanks and their series configuration, and the efficiency of agitation and aeration—all determined based on the leaching characteristics of the material after pretreatment.

5. Desorption, Electrolysis, and Tailings Section

• Desorption Column: Ambient temperature and pressure or high temperature and high pressure, determined by the difficulty of desorbing gold-loaded carbon;
• Electrolysis tanks: Sized to match the volume of precious metal solution and gold concentration; focus on current efficiency and gold slurry grade;
• Tailings Treatment: Dry discharge via filter presses or treatment to meet regulatory standards after thickening; for arsenic-containing tailings, environmental requirements such as stabilization and solidification must be considered;
• Key Selection Considerations: Tailings from arsenic- and carbon-bearing ores are subject to stringent environmental compliance requirements; for overseas projects, local environmental standards must be considered in advance.

Estimated Timeline: For Carlin-type gold deposits, the testing and commissioning periods are longer than for conventional deposits due to the addition of flotation and pre-treatment stages. Conventional validation takes approximately 3–4 weeks, and a comprehensive proposal report takes 30–45 days; the overall project duration is 8–15 months, with additional buffer time required for difficult-to-process ores.