Gold Mineral Processing: CIP Carbon-in-Pulp Process

Precious metal metallurgy and mineral processing engineering remain a field deeply cultivated by mining professionals. After years of data analysis and customer feedback, CHUNLEI discovered that the root cause of low recovery rates lies not in chemical process defects, but in carbon management. While the carbon-in-pulp (CIP) process appears straightforward, the physical dynamics between carbon and pulp—such as carbon transport, adsorption, screening, and regeneration—ultimately dictate the project’s profitability. This article analyzes key design details of the CIP process, explaining how CHUNLEI engineers these systems to enhance gold recovery from carbon-in-pulp fines.

In-Depth Analysis of CIP Process – Why Carbon Management Determines Success or Failure?

What is the CIP Gold Extraction Process?

CIP, also known as the carbon-in-pulp process, is a mature gold extraction technology. It operates on a “leach first, adsorb later” model. During the leaching stage, gold carriers are fully dissolved across multiple leaching tanks. Subsequently, the pulp is adsorbed by activated carbon. Unlike carbon-in-leach (CIL) processes, which combine leaching and adsorption, CIP separates these steps, offering operators greater control flexibility.
The CIP process employs a counter-current flow design: the pulp flows forward from the first tank to the last, while the activated carbon moves in the opposite direction, from the end toward the front. This design ensures that highly active carbon consistently contacts low-concentration gold solution, maximizing adsorption and minimizing gold loss.
Because leaching and adsorption operate independently, operators can better control parameters at each stage and make timely adjustments. This design is particularly suitable for complex ores and mineral processing requiring staged treatment.

Why Do Most CIP Plants Have Insufficient Recovery Rates?

Based on CHUNLEI’s analysis of data from 87 CIP plants worldwide, it was found that:

Performance Metrics	Industry Average	Optimized achievable values	Increase
Gold Adsorption Rate	94-96%	99.2–99.8%	2.95
Gold Load per Carbon	4000-6000 g/t	8,000–12,000 g/t	100%
Cyanide Consumption	0.8-1.2 kg/t	0.4–0.6 kg/t	-50%
Carbon Loss Rate	15-25%/year	5–8%/year	-70%

Core Issue Identification:

• Uneven Carbon Distribution: Leading to excessive saturation in some areas and underutilization in others
• Low Screening Efficiency: Fine carbon losses account for 40-60% of gold losses
• Incomplete Regeneration: Activation recovery rate only reaches 70-80%
• Imprecise Oxygen Control: Fluctuations in dissolved oxygen cause a 5-10% decline in leaching efficiency

Detailed Explanation of CIP Six-Step Process Optimization

Achieving high gold recovery rates requires precise, systematic management of material and chemical flows. The CIP (Carbon-in-Pulp) process is an interconnected continuous operation whose efficient execution begins with a critical preparatory stage—slurry preparation.

Step 1. Slurry Pretreatment – Laying the Foundation for Efficient Leaching

Gold ore is crushed and grinded to the target particle size (typically 95% passing 200 mesh) to break it down. Concentration and impurity removal are then performed using hydrocyclones, vibrating screens, etc. (impurity removal >98%, hydrocyclone underflow concentration >65%) to prevent clogging of downstream equipment. Finally, parameters such as pulp concentration are adjusted to prepare for cyanide leaching.
The combination of high-frequency vibrating screens and hydrocyclones elevates impurity removal from 85% in traditional processes to 98%, significantly reducing interference from gold-displacing substances.

Step 2. Cyanide Leaching – Precise Chemical Reaction Control

Cyanide is added to the pulp in a series of tandem leaching tanks, dissolving gold through chemical reaction. As the pulp sequentially flows through multiple leaching tanks, adding cyanide to the final tank achieves over 90% gold leaching efficiency.

Intelligent Oxygen Control System:

• Real-time Monitoring: Dissolved oxygen sensors installed in each tank
• Automatic Adjustment: Oxygen injection rate automatically adjusted based on gold concentration feedback
• Energy Savings: 35% improvement in oxygen utilization, 30% reduction in cyanide consumption

Step 3. Activated Carbon Adsorption – Core Carbon Management Process

Activated carbon is added to the cyanidated pulp, which flows countercurrently with the carbon through multiple adsorption tanks. Carbon is introduced into the final tank with the lowest gold concentration and progressively transferred to the initial tank with higher gold content. Gold-loaded carbon is ultimately discharged from the first tank. Gold adsorption typically exceeds 99%.

Five-stage countercurrent adsorption tank configuration:

Trough Number	Gold Concentration (g/t)	Carbon Concentration (g/L)	Carbon Load Capacity (g/t)	Adsorption Efficiency
Trough 1	10月15日	15-20	8000-12000	85-90%
Trough 2	2月5日	20-25	4000-6000	90-95%
Trough 3	0.5–1.5	25-30	2000-3000	95-98%
Trough 4	0.1–0.5	30-35	800-1500	98-99%
Trough 5	<0.1	35-40	200-500	99-99.5%

Key Carbon Management Technologies:

• Automatic Carbon Transfer System: Real-time adjustment of carbon transfer rates based on online gold analyzer data
• High-Efficiency Screening System: Dual-layer vibrating screen design achieves carbon recovery rate >99.5%
• Carbon Concentration Control: Maintains target carbon concentration within ±2g/L per tank

Step 4. Gold-Loaded Carbon Processing – Maximizing Gold Recovery

Remove impurities such as calcium carbonate from the carbon surface using dilute hydrochloric acid. Concentrate gold from the carbon at high temperature and pressure within the desorption column. The gold-enriched solution undergoes chemical reactions in the electrolytic cell, where gold is adsorbed to form gold sludge. The desorbed activated carbon can be recycled after high-temperature treatment (approximately 700°C).

Optimized Desorption Process Parameters:

Acid Washing Pretreatment: 3-5% dilute hydrochloric acid, 90°C, 2-4 hours

Desorption Conditions: 1% NaOH + 0.2% NaCN, 130-150°C, 300-500 kPa

Desorption Efficiency: >99.5%, reduced desorption time to 8-12 hours (traditional method requires 24-48 hours)

Electrolytic Recovery: Steel wool cathode, current density 10-20 A/m², gold recovery rate >99.8%

Breakthrough in Thermal Regeneration System:

Regeneration Temperature: 700-750°C (Precise temperature control ±10°C)

Dwell Time: 20-30 minutes

Activity Recovery Rate: 92-95% (Industry average only 75-85%)

Carbon Loss: <2% per regeneration cycle

Step 5. Gold Recovery & Purification – Yielding 99.99% Refined Gold

Impurities are removed from gold slime using nitric or hydrochloric acid to produce crude gold ingots. Electrolytic refining then reduces these into 99.99% refined gold.

Step 6. Tailings Treatment and Water Resource Recovery

Hydrogen peroxide is used to reduce cyanide concentrations in tailings, preventing environmental pollution.

Fully Automated CIP Plant Solutions

The mining industry is advancing toward full automation, with CIP having abandoned traditional manual control modes. Outdated operational methods directly impact recovery rates. Today’s automation enables precise control.

[Automatic Carbon Transfer System]: Dynamically drives carbon pumps based on real-time gold-loading data, eliminating reliance on fixed schedules for transferring carbon between adsorption columns. Carbon remains near saturated loading prior to desorption, maximizing adsorption efficiency.
[Intelligent Oxygen Regulation]: By continuously monitoring dissolved oxygen levels in the agitation tank, the system automatically adjusts oxygen injection rates. This ensures stable oxidation reactions while preventing excessive oxygen consumption.
[Efficient Tailings Disposal]: Facing increasingly stringent environmental regulations, dry stacking has become standard practice. We integrate high-pressure filters and dewatering screening systems at the end of the CIP circuit, significantly increasing water recovery rates and producing dry tailings cakes ready for direct transport or stockpiling.
This comprehensive closed-loop automation solution not only optimizes gold recovery processes but also achieves data-driven resource minimization and production stability maximization, setting new standards for sustainable mining operations.

Key Automation Subsystems

1.Intelligent Carbon Management System

– Online Gold Analyzer: Monitors gold concentration in each tank every 30 minutes

– Carbon Gold Load Calculation: Real-time computation of gold load per carbon batch

– Automated Carbon Transfer: Optimizes transfer strategy based on mathematical models

– Carbon Inventory Management: Tracks distribution and status of carbon across the entire plant
Effect: 25% increase in carbon utilization rate, 1.5-2.5% improvement in gold recovery rate

2.Precision Oxygen Control System

– Dissolved Oxygen Sensor: Anti-interference design with ±0.1ppm accuracy

– Adaptive Control: Automatically adjusts control parameters based on ore characteristics

– Feedforward Control: Preemptively adjusts oxygen injection volume based on feed variations

– Energy-Saving Mode: Minimizes oxygen consumption while maintaining leaching rates
Benefits: 30% reduction in oxygen consumption, 25% reduction in cyanide consumption

3.Predictive Maintenance System

– Vibration Monitoring: Real-time vibration analysis of critical equipment

– Temperature Monitoring: Bearing and motor temperature surveillance

– Lubricant Analysis: Online oil quality testing

– AI Failure Prediction: Machine learning-based equipment failure forecasting
Value: 70% reduction in unplanned downtime, 40% reduction in maintenance costs

CIP vs CIL – How to Choose the Optimal Process?

Comparison Dimensions	CIP Process	CIL Process	Optimal Recommendations
Applicable Ore Types	Complex minerals, carbonaceous gold ore	Simple Oxide Gold Ore	Select based on ore characteristics:
Investment Costs	Higher (more equipment)	Lower (Shorter Flow)	Limited investment budget: Choose CIL
Operating Costs	Lower (reagent savings)	Higher (Increased Cyanide Consumption)	Long-term operation: Choose CIP
Gold Recovery Rate	95-99.5%	90-96%	High-grade ore: Choose CIP
Operational Flexibility	High (stepwise control)	Low (Coupled Control)	Requires flexible adjustments: Choose CIP
Automation Level	Easily automated	Higher Automation Difficulty	Smart factory: Choose CIP
Environmental Performance	Good (cyanide controllable)	Moderate (Cyanide Difficult to Control)	High environmental requirements: Choose CIP

Process Selection Based on Ore Characteristics Analysis

– Simple Oxide Gold Ore → CIL Process
– Complex Carbonaceous Gold Ore → CIP Process
– High-Grade Gold Ore (>5 g/t) → CIP Process
– Low-Grade Gold Ore (<1 g/t) → Requires Economic Evaluation

Considerations:

– Investment Budget: <$5 million → CIL; >$10 million → CIP

– Ore processing capacity: <1,000 t/d → CIL; >2,000 t/d → CIP

– Environmental requirements: Stringent → CIP; General → CIL

– Automation objectives: Fully automated → CIP; Semi-automated → CIL

Frequently Asked Questions

Question 1: What is the difference between CIP and CIL (Carbon-in-Leach)?

The primary difference lies in the sequence of gold leaching and carbon adsorption.
CIP: Ore undergoes cyanide leaching first, followed by adding activated carbon to a separate adsorption tank for gold adsorption. Leaching and adsorption are conducted in separate steps.
CIL: Activated carbon is directly added to the leaching tank, with leaching and adsorption occurring simultaneously. The CIL process is shorter and currently more mainstream, though “CIP” is often used as a generic term for this process type.

Question 2: Why is activated carbon used?
Activated carbon possesses a large specific surface area and strong adsorption capacity, enabling efficient and selective adsorption of gold cyanide complexes from gold-bearing solutions. This separates gold from the pulp, and the carbon can be regenerated and reused.

Question 3: What are the primary factors affecting gold recovery rates?
Activated carbon activity: Fresh or well-regenerated carbon exhibits superior adsorption capacity.
Carbon concentration and movement: Sufficient carbon must be maintained within the tank, with regular, metered counter-current movement to ensure thorough contact between depleted carbon and rich leachate, as well as between enriched carbon and depleted leachate.
Dissolved oxygen levels: Adequate dissolved oxygen is critical for gold cyanide leaching; oxygen deficiency leads to reduced leaching rates.
Slurry Properties: pH (typically maintained at 10.5-11), temperature, viscosity, and the presence of gold-sequestering substances (e.g., organics, sulfides, copper) all impact efficiency.

Question 4: What is “gold loading capacity”? Why is it important?
This refers to the amount of gold adsorbed per unit weight of activated carbon (e.g., grams of gold per ton of carbon). It serves as a core metric for evaluating carbon adsorption efficiency and production economics. Too low a loading capacity is uneconomical, while excessively high levels may cause premature gold desorption or loss in tailings. Operations must be optimized to achieve the maximum designed capacity before desorption.

CHUNLEI CIP Optimization Case Study

Comparison Analysis Table of CIP System Upgrades at a Large Gold Mine in Tanzania

Key Performance Indicators Comparison

Comparison Dimensions	Before Renovation (Baseline Condition)	After modification (optimized state)	Increase	Economic Benefits
Gold Recovery Rate	86-88% (Significant Fluctuations)	94.5% (stable operation)	7.50%	Annual Revenue Increase: $32 million
Annual Processing Capacity	5 million tons/year	5.5 million tons/year	10%	Capacity Enhancement: $12 million
Operating Costs	$32/ton	$25/ton	-22%	Annual Savings: $3.85 million
Payback Period	–	3.2 months	–	Rapid Return on Investment

Critical System Components Comparison

Indicator	Before Renovation	After renovation	Effectiveness Boost
Recovery Rate	87%	94.50%	7.50%
Annual Revenue	–	+$32 million	Direct Revenue Increase
Operating Costs	$32/ton	$25/ton	-22%
Payback Period	–	3.2 months	Rapid Return on Investment

Process Parameters Comparison

System	Before Renovation	After modification	Improvement Results
Carbon Management	Manual operation, uneven distribution	Automatic transmission, real-time monitoring	Carbon Loss ↓71%
Screening Efficiency	82-85%	99.20%	Gold Recovery ↑3.2%
Cyanide Consumption	1.1 kg/ton	0.55 kg/ton	Usage Halved
Level of Automation	30%	95%	Operators ↓62%

Economic Benefits Summary

Parameters	Before Modification	After renovation	Control Accuracy
Dissolved Oxygen	3-10 ppm (high fluctuation)	6±0.5ppm	Stable at 83%
pH Value	10-11 (manual)	10.8±0.1	Automatic Control
Desorption Temperature	130±15°C	135±3℃	Accuracy ↑80%

Summary of Economic Benefits

Investment Categories	Investment Amount	Annual Revenue	Payback Period
Carbon Management System	$1.8 million	$6.2 million	3.5 months
Automation System	$2.8 million	$4.5 million	7.5 months
Screening System	$950,000	$3.2 million	3.6 months
Total	$9.4 million	$22 million	3.2 months

Conclusion

In the gold carbon-in-pulp extraction process, every 1% increase in recovery rate translates to millions of dollars in annual revenue. The key to achieving this lies not in complex chemical formulations, but in a refined carbon management system. Optimizing each stage—from carbon screening, transportation, and adsorption to regeneration—delivers tangible economic returns.

CHUNLEI’s experience across over 200 CIP projects demonstrates that scientific carbon management can boost gold recovery by 3-8% and shorten the payback period to 3-6 months. Against the backdrop of elevated gold prices and increasingly stringent environmental regulations, optimizing CIP processes is not merely a pursuit of technology but a strategic investment in corporate competitiveness.

Remember: In CIP processes, carbon is not merely an adsorbent—it is the carrier of gold. Managing carbon effectively means managing your gold profits.

CHUNLEI Global CIP Technology Expert Team – Providing Professional Technical Support 24/7.

Contact CHUNLEI today to explore your  Gold Ore Purification and Processing needs.