Inside a Raymond Grinding Line: From Crushing to Packaging Flowchart

The Complete Flow: What Goes Inside a Grinding Line

A Raymond grinding line is a closed-circuit, dry processing system that converts raw minerals from large lumps into fine powder through four tightly integrated phases: crushing, grinding and classification, powder collection, and automatic packaging. The entire sequence is designed to handle feed sizes typically below 30 mm and deliver finished products ranging from 30 to 425 mesh (0.6 mm to 0.033 mm), with capacities spanning 1 to 30 tons per hour depending on the model and material hardness.

Understanding each internal stage helps operators optimize throughput, reduce unplanned downtime, and maintain consistent product quality. Below is a detailed walk‑through of the equipment and process logic that makes up the line.

Raw Material Handling and Primary Crushing

The line begins with a feeding and size‑reduction station that guarantees the mill receives material it can process efficiently. Oversized stones are first loaded into a hopper and passed to a jaw crusher. This crusher reduces rocks as large as 200–300 mm down to less than 30 mm, the maximum safe feed size for the grinding rollers.

Jaw Crusher and Bucket Elevator

The crushed material is lifted by a bucket elevator into a storage silo situated above the mill. A vibrating feeder meters a controlled, steady stream of feed into the grinding chamber. Interlocking controls stop the feeder if the mill motor current spikes, protecting the equipment from overload.

The Grinding and Dynamic Classification Core

This is the heart of the line, where comminution and sizing happen simultaneously. The mill host contains a rotating grinding ring and multiple suspended rollers that press against the ring under centrifugal force. Material fed into the bottom is ground between the ring and rollers, carried upward by airflow, and presented to a high‑efficiency classifier.

Pendulum Roller Mill Mechanics

As the main shaft rotates, the rollers swing outward and grind the material in a multi‑layer compression zone. Typical roller diameters range from 300 mm to 600 mm, and the grinding ring can reach diameters of 1,000 mm to 1,800 mm. The large contact area and the material bed’s residence time – typically a few seconds – produce a sharp particle size distribution with minimal over‑grinding.

Classifier and Airflow Control

A dynamic turbo classifier sits above the grinding zone. Its speed is adjustable; higher RPM produces finer powder. For example, running at 200–400 rpm yields a product around 200–325 mesh. The system fan pulls negative pressure through the mill, sweeping fine particles up into the classifier while coarse material falls back for regrinding. Airflow and classifier speed together set the final cut point.

Powder Collection and Dust Control

Once the material passes the classifier, it must be separated from the conveying air stream and collected without loss or environmental release. This stage uses a combination of cyclones and fabric filters.

Cyclone Collector Efficiency

A high‑efficiency cyclone removes 95–99% of the product from the air. The collected powder is discharged through a rotary airlock valve into a surge bin or directly to the packaging machine. The remaining dust‑laden air proceeds to the baghouse for final cleaning.

Baghouse and Emission Control

A pulse‑jet bag filter captures the sub‑micron dust that escapes the cyclone. This unit typically holds 200–500 filter bags, with filtration velocities of 0.8–1.2 m/min. Cleaned air is then either recirculated into the mill circuit or exhausted outside, meeting strict dust emission standards often below 30 mg/Nm³.

Automatic Packaging and Storage

Final powder handling bridges production and dispatch. The collected product flows into a storage silo or hopper, from which an automatic valve bag filling machine fills bags at rates of 3–6 bags per minute. Weighing accuracy is typically within ±0.2 kg per bag. For bulk loading, a pneumatic conveying system can send the powder to a truck or super‑sack filling station.

Process Flowchart: Step‑by‑Step from Crusher to Bag

The sequential path ensures continuous, controlled material progression. The following ordered list maps the exact route a rock takes before leaving as bagged powder.

1. Large raw stone enters the jaw crusher and is reduced to <30 mm.
2. Crushed material is lifted by bucket elevator into a buffer silo.
3. A vibrating feeder discharges a uniform flow into the grinding chamber.
4. Inside the mill, material is ground between rotating rollers and the ring; airflow picks up fine particles.
5. The classifier allows only on‑spec fines to exit; coarse material falls back for further grinding.
6. Qualified powder is captured in the cyclone and discharged via rotary valve.
7. Residual dust is removed by the baghouse filter.
8. Collected powder is transferred to the packaging machine and filled into bags, or stored in silos.

Equipment Summary and Typical Performance Data

The table below consolidates each main component, its role, and common working parameters. These values vary with material type (limestone, calcite, dolomite, etc.) and desired fineness.

This integrated chain turns raw stone into market‑ready powder with high consistency. Mastering each internal module lets operators tune output, lower energy per ton, and extend component life.