The Next Generation of Coal Beneficiation

As mining companies strive to improve coal quality while reducing water consumption, operating costs, and environmental impact, dry beneficiation technologies are rapidly emerging as the preferred alternative for first-stage coal preparation.

Unlike conventional washeries that depend on large volumes of water and complex slurry management systems, modern dry beneficiation utilizes the physical characteristics of coal and impurities to achieve efficient separation without generating wastewater.

Among these innovations, Ardee Hi-Tech Pvt. Ltd. has developed an integrated dry beneficiation ecosystem comprising two complementary technologies:

• AAKSS (Ardee Air Knife Separation System) – an advanced dry sorting technology for removing shale, stone, and pyritic impurities.
• ARCAM DE-XRT - a real-time, online coal quality analyser that continuously measures ash content and enables automated process optimization.

Together, these technologies provide a fully integrated beneficiation solution capable of improving coal quality while minimizing environmental impact.

Why Dry Beneficiation Makes Sense

Coal and the unwanted materials mined alongside it differ significantly in their physical characteristics.

Coal is a naturally porous material with a relatively low apparent density.

By comparison:

Material	Typical Density (g/cc)
Coal	Lower apparent density due to porosity
Shale	2.2–2.7
Stone	2.2–2.7
Pyrites	3.2–5.0

Rather than using water to exploit these density differences, AAKSS uses carefully engineered high-velocity air streams to separate lighter coal from heavier contaminants.

The result is an efficient, water-free beneficiation process requiring significantly less infrastructure than a conventional washery.

Inspired by Nature: The Principle of Winnowing

The concept behind AAKSS originates from one of humanity's oldest grain-cleaning techniques—winnowing.

For centuries, farmers have separated grain from chaff by dropping harvested material through a steady breeze.

The heavier grain falls almost vertically, while the lighter chaff is carried further by the airflow.

AAKSS applies the same physical principle using advanced engineering.

Instead of grain and chaff, the system separates:

• Coal
• Shale
• Stone
• Pyritic contaminants

Instead of natural wind, it uses precisely engineered high-velocity air knives.

Instead of manual collection, automated separation plates continuously produce distinct product streams.

A centuries-old principle has thus been transformed into a sophisticated industrial beneficiation technology.

How the Ardee Air Knife Separation System (AAKSS) Works

AAKSS consists of several integrated components working in precise coordination:

• Low-amplitude, high-frequency vibratory feeder
• High-volume industrial blower
• Specially engineered Air Knife nozzles
• Precision electronic drives
• Automated separation plates
• Integrated control system
• ARCAM DE-XRT online ash analysers

Coal is first crushed to below 100 mm and classified into narrow size fractions.

This sizing step is essential because particle size strongly influences aerodynamic behaviour.

Each size fraction is then fed into a dedicated Air Knife module.

As particles leave the feeder, they pass through a thin, high-velocity fan-shaped air stream.

The response depends on each particle's density and aerodynamic characteristics:

Clean Coal

Being lighter and more porous, coal particles remain suspended in the airflow for a longer distance before landing.

These particles form the clean coal stream.

Rejects

Dense shale, stone, and pyrites are minimally affected by the airflow.

They fall almost vertically into the reject stream.

Middlings

Intermediate particles travel an intermediate distance.

These become the middlings, which may be blended, reprocessed, or utilized depending on quality requirements.

Unlike wet washing, the process generates no slurry, no wastewater, and requires no tailings ponds.

Engineering Precision Behind AAKSS

Achieving efficient separation requires far more than simply blowing air across falling coal.

Each AAKSS module is individually engineered based on several critical parameters:

• Air velocity
• Air pressure
• Fan beam thickness
• Nozzle geometry
• Separation plate positioning
• Feed rate
• Particle size distribution
• Motor speed
• Blower capacity

Even minor adjustments influence separation efficiency.

This precision engineering enables AAKSS to achieve consistent performance across different coal types and operating conditions.

Intelligent Coal Preparation Begins with Proper Sizing

One of the defining strengths of the AAKSS process is its emphasis on particle size classification.

After primary crushing, coal passes through rotary screens that divide it into several narrow fractions:

• 100–75 mm
• 75–50 mm
• 50–30 mm
• 30–20 mm
• 20–12 mm
• 12–6 mm

Each fraction is processed independently using dedicated Air Knife modules.

This approach allows airflow conditions to be optimized for each size range, improving separation accuracy and maximizing clean coal recovery.

Particles smaller than 6 mm are bypassed and evaluated separately.

ARCAM DE-XRT: The Intelligence Behind the Process

Efficient dry sorting depends not only on effective separation but also on accurate, real-time quality measurement.

This is where ARCAM DE-XRT plays a pivotal role.

Developed by Ardee, ARCAM DE-XRT is an online Dual Energy X-Ray Transmission (DE-XRT) analyser that continuously measures coal ash on conveyor belts or transfer chutes without physically contacting the material. Unlike conventional dual gamma analysers, it uses an electrically activated X-ray generator rather than radioactive isotopes, enhancing operational safety and simplifying regulatory compliance.

Key capabilities include:

• Continuous online ash analysis
• Wide sensing area covering a substantial portion of the material stream
• Non-contact measurement
• Real-time data acquisition
• Fast response times
• PLC, SCADA, and plant automation integration
• Remote diagnostics and calibration
• Optional integration with moisture analysers for real-time Gross Calorific Value (GCV) estimation on an as-received basis.

This enables operators to monitor coal quality continuously rather than relying solely on periodic laboratory sampling.

Why DE-XRT Represents a Significant Advancement

Conventional online coal analysers commonly employ Americium-241 and Caesium-137 radioactive sources.

Although effective, these systems introduce several operational challenges:

• Regulatory approvals
• Radioactive source handling
• Disposal responsibilities
• Frequent recalibration
• Limited measurement width
• Imported service support

ARCAM DE-XRT addresses many of these limitations through its use of electrically generated X-rays. According to Ardee's technical data, the system provides a much wider measurement width, faster integration time, larger effective sampling volume, remote auto-calibration capability, and eliminates the need for long-term radioactive source disposal.

The result is a safer and more maintenance-friendly online analyser that supports continuous coal quality management.

Closed-Loop Quality Control

Perhaps the greatest advantage of combining AAKSS with ARCAM DE-XRT is automation.

Instead of operating as independent systems, they function as a closed-loop beneficiation platform.

The process works continuously:

1. Raw coal enters the AAKSS plant.
2. Air Knife modules separate cleans, middlings, and rejects.
3. ARCAM DE-XRT measures the quality of each product stream in real time.
4. Control software analyses the measurements.
5. If product quality deviates from target specifications, operating parameters—such as feeder speed or airflow—can be adjusted automatically.
6. Separation performance is continuously optimized.

This intelligent feedback loop minimizes human intervention while maintaining consistent coal quality.

More Than a Sorter—A Complete Coal Quality Management System

Beyond separation, ARCAM DE-XRT enables several operational improvements across the mine and coal handling chain.

Stockpile Management

Incoming coal can be assessed before stacking, allowing mines to create stockpiles based on ash content or estimated GCV rather than relying solely on mine block data.

Blending

Different quality coal streams can be blended to meet customer specifications more consistently.

Washery Optimization

Coal already meeting the desired quality can bypass washing, reducing unnecessary processing, lowering operating costs, and increasing effective washery capacity.

Dispatch Quality

Real-time monitoring helps reduce grade variation in dispatched coal, improving customer confidence and minimizing commercial disputes.

Mine Planning

Continuous quality data enables better planning of excavation, stock management, and production scheduling.

Proven Technology in Industrial Applications

The technologies developed by Ardee have moved beyond laboratory concepts into practical implementation.

AAKSS has been successfully deployed for applications such as pyrite removal from lignite, where industrial trials demonstrated complete removal of pyrites from the clean lignite product, while identifying opportunities to recover additional lignite through reprocessing of rejects.

Ardee has also implemented dry beneficiation plants using its proprietary technologies, reinforcing its capability to deliver integrated, turnkey solutions from engineering and equipment supply through commissioning.

Environmental and Operational Benefits

By eliminating water from the primary separation process, AAKSS offers several sustainability advantages:

• Conserves freshwater resources.
• Eliminates slurry generation.
• Reduces tailings management requirements.
• Lowers civil infrastructure needs.
• Decreases energy consumption associated with pumping and dewatering.
• Simplifies plant operation.
• Reduces maintenance demands.
• Supports cleaner coal production closer to the mine.

These benefits align closely with the mining industry's growing focus on resource efficiency, environmental stewardship, and responsible coal utilization.

Looking Ahead

Coal beneficiation is evolving from a water-intensive mechanical process into a digitally controlled, data-driven operation.

The combination of AAKSS and ARCAM DE-XRT demonstrates how dry separation and real-time analytics can work together to improve coal quality, enhance operational efficiency, and reduce environmental impact.