Iran 1200 t/d Oxidized Gold Processing Plant Expansion: A Fast-Track, High-Stability Gold Mine Upgrade | Xinhai Mining

1. Project Background: Expanding from 500 t/d to 1200 t/d

The project is located in Iran and processes oxidized gold ore with an average grade of around 1.2 g/t. It is an expansion of the gold cyanidation plant commissioned in 2020, originally designed for 500 t/d. Because the first phase was completed quickly—built and commissioned within one year—and consistently exceeded its design output, the client decided to continue working with Xinhai Mining for the second-phase expansion.

The first plant was designed for 500 t/d but achieved a stable 600 t/d in actual operation. As ore supply increased, the existing capacity became insufficient, prompting the construction of an additional 600 t/d line. This expansion increased the total planned capacity to 1200 t/d, and after system optimization, the plant reached 1500 t/d in actual stable output.

A key feature of this project is that no additional mineral processing testwork was required. The expansion was engineered based on the fully validated flowsheet and equipment configuration from Phase I. With consistent ore characteristics and clear design parameters, the project followed a streamlined engineering path. From down payment to full production, the expansion took only 10 months, and performance indicators—including throughput and recovery—surpassed client expectations.

2. Design Scope and Process Description

Under the EPC framework, Xinhai Mining was responsible for the complete construction drawing design and equipment supply (excluding the tailings storage facility). The design scope covered:

Ø  Ore bin and feeding system

Ø  Grinding and classification workshop

Ø  Cyanide leaching workshop

Ø  Thickening and water supply units

Ø  Tailings dewatering workshop

Ø  Desorption, electro-winning and refining workshop

Ø  Supporting civil works, power supply, water supply & drainage, and general layout

(1) Crushing System

The project fully leveraged the client’s existing crushing and screening system. Only a belt conveyor to the fine ore bin was added. The crushed product size remained at ≤ 15 mm, ensuring adequate grinding efficiency while minimizing new investment.

(2) Grinding and Classification

A two-stage closed-circuit grinding process was adopted:

Stage 1: Ball mill + classifier

Stage 2: Ball mill + hydrocyclone

The final grinding fineness was controlled at 80–85% passing 200 mesh, optimized based on ore characteristics to balance recovery and throughput.

(3) Cyanide Leaching

The leaching section used double-impeller agitation tanks, upgraded to 10 leaching stages.

Main parameters:

Ø  Pulp density: ~40%

Ø  Total leaching time: 26 hours

Ø  Aeration: high-pressure Roots blowers

Ø  This ensured a stable oxidation environment and high leaching efficiency.

(4) Carbon Adsorption

The pregnant solution passed through adsorption tanks where gold was loaded onto activated carbon. Loaded carbon was then transferred to the desorption and electro-winning workshop.

(5) Desorption, Electro-winning and Refining

The expansion used Xinhai’s high-efficiency desorption & electro-winning system, known for:

Ø  High desorption rate

Ø  Short cycle time

Ø  Fast carbon regeneration

Ø  Gold sludge was then smelted to produce doré bullion.

(6) Tailings Dewatering

Post-leaching tailings were dewatered using a pressure-filter system, producing low-moisture filter cakes suitable for transportation and environmentally compliant storage.

3. Project Highlights: Technical, Operational and Construction Advantages

3.1 Actual throughput significantly exceeded design capacity

Although designed for 1200 t/d, the plant achieved a stable 1500 t/d, demonstrating excellent process stability and equipment performance.

3.2 Optimized grinding fineness without affecting recovery

Based on real-time ore characteristics, the grinding fineness was adjusted slightly coarser. This optimization:

Ø  Maintained leaching and overall recovery rates

Ø  Significantly improved processing capacity

Ø  Reduced unnecessary over-grinding

3.3 Pressure-filter with washing and squeezing improves pregnant solution recovery

The selected pressure filter provided:

Ø  Higher gold-bearing solution recovery

Ø  Low filter-cake moisture

Ø  Easier tailings transportation

Ø  Environmental compliance

3.4 Increased fresh-water storage capacity

Due to limited local water availability, the design expanded water storage to ensure stable plant operation and eliminate bottlenecks during peak production.

3.5. Maximum reuse of the existing crushing line

By continuing to utilize the original crushing system, the project:

Ø  Reduced capital expenditure

Ø  Shortened construction time

Ø  Minimized disturbance to existing operations

3.6 Replacing steep-angle conveyors with a classifier for return sand

This modification eliminated issues such as material spillage, leakage, and environmental contamination. Additional benefits included:

Ø  Cleaner site conditions

Ø  Lower labor intensity

Ø  Reduced maintenance cost

Ø  Higher operational safety

3.7 Enlarged leaching-tank pipelines while keeping the plant in continuous production

Pipeline upgrades significantly enhanced slurry flow capacity without interrupting production—ensuring no revenue loss during construction.

3.8 Upgraded cylindrical screens to improve slurry-passing capacity

Optimized screen structure and flow distribution allowed the system to accommodate higher throughput.

3.9 High-efficiency desorption & electro-winning system

Xinhai’s technology ensured:

Ø  High desorption efficiency

Ø  Short operational cycles

Ø  Higher gold recovery from loaded carbon

3.10 Entire expansion completed without stopping production

Through precise scheduling and sectional construction, all modifications were executed while maintaining full plant operation—maximizing economic benefits for the client.

4. A Replicable Model for Fast, Stable Gold Processing Plant Expansion

This 1200 t/d gold processing plant expansion demonstrates what a well-planned, engineering-driven upgrade can achieve:

Ø  Short construction period

Ø  Fast start-up and early revenue

Ø  High operational stability

Ø  Low risk and strong cost-effectiveness

Building on the proven Phase-I flowsheet and focusing on targeted process optimization, the project achieved a significant performance leap—from 500 t/d to 1200 t/d, and eventually to 1500 t/d in stable operation.

With extensive experience in gold ore processing, cyanidation technology, and EPC project delivery, Xinhai Mining continues to provide global mining clients with efficient, reliable and fully integrated processing plant solutions—especially for brownfield expansions and capacity upgrades where downtime must be minimized.