I. Project Overview

Coal powder preparation is a critical process in thermal power generation, cement production, metallurgy, and the chemical industry. The Raymond mill (pendulum roller mill), as a vertical roller grinding mill, works by crushing materials through compression between grinding rollers and a grinding ring, and performs excellently in processing medium‑hard materials. Raymond mills are suitable for small‑ to medium‑scale coal powder production, with mature technology and relatively low investment costs.

However, coal powder is a flammable and explosive material. Grinding coal with a Raymond mill requires explosion‑proof design and comprehensive safety measures. Conventional Raymond mills cannot be used directly for coal processing; an explosion‑proof Raymond mill or an open‑circuit system mill must be selected.

This solution is designed for bituminous coal/anthracite (Mohs hardness approximately 1.5–3) using an explosion‑proof Raymond mill as the core equipment for a coal powder production line.

II. Raw Material and Product Specifications

2.1 Raw Material Requirements

2.2 Product Specifications

Note: If ultra‑fine coal powder of >400 mesh (e.g., 800 mesh, 1250 mesh or finer) is required, a standard Raymond mill cannot meet the requirement. An ultra‑fine vertical mill or ultra‑fine ring roller mill must be used instead.

III. Process Flow

3.1 Process Flow Diagram

Raw coal → Screening (impurity removal) → Jaw crusher (primary crush to ≤30 mm) →
Bucket elevator → Raw coal storage bin → Electromagnetic vibrating feeder (uniform and quantitative feeding) →
Explosion‑proof Raymond mill (grinding) → Air‑borne powder → Explosion‑proof classifier →
    ├─ Coarse powder → Returned to grinding chamber for re‑grinding
    └─ Qualified fine powder → Explosion‑proof cyclone collector → Finished powder discharge → Automatic packing
         ↓
    Explosion‑proof pulse bag filter (purified exhaust discharged to atmosphere)

3.2 Detailed Description of Each Step

(1) Raw material pretreatment (screening and crushing)

Raw coal is first screened through a grizzly screen to remove large impurities. The large coal lumps are then crushed by a jaw crusher to ≤30 mm. During conveying, an electromagnetic separator should remove ferrous impurities to protect downstream equipment from damage.

(2) Feeding

The crushed coal is conveyed by a bucket elevator to a storage bin. At the bottom of the bin, an electromagnetic vibrating feeder delivers the material uniformly, quantitatively and continuously into the Raymond mill. Uniform feeding is critical to ensuring output and product quality.

(3) Drying (depending on raw material moisture)

If the raw coal moisture exceeds 6–10%, drying must be carried out before or during grinding. A hot‑air furnace can be used to provide hot air, enabling simultaneous drying and grinding. The inlet air temperature must be controlled within an appropriate range, and the outlet air temperature is recommended to be controlled at 75–95 °C.

(4) Grinding

After the small coal pieces enter the grinding chamber, the shovel blades lift the material and feed it between the grinding rollers and the grinding ring. Under centrifugal force, the main unit rollers swing outward and press tightly against the ring, pulverising the coal by compression and shearing.

(5) Classification

The ground coal powder is carried by the blower air stream to the classifier at the top for separation. By adjusting the classifier speed, the finished fineness can be controlled within the range of 80–400 mesh. Unqualified coarse powder is returned to the grinding chamber for re‑grinding.

(6) Collection

The qualified fine powder is carried by the air stream into the explosion‑proof cyclone collector, where it is collected and discharged through the powder outlet as finished product.

(7) Dust collection and exhaust treatment

The system operates under negative pressure. An explosion‑proof pulse bag filter is used for exhaust gas purification. Temperature and pressure monitoring points are installed at each dust hopper to ensure no dust accumulation.

IV. Equipment Selection and Configuration

4.1 Core Equipment Selection

Coal powder of 80–325 mesh is typically produced using a Raymond mill. The two key selection criteria are fineness and output.

Conventional Raymond mills have an output range of 1–55 t/h and a finished fineness of 80–400 mesh. The MTW European‑type mill, as an upgraded version of the traditional Raymond mill, offers an output of 3–55 T/H and a fineness range of 0.045–1.6 mm.

4.2 Complete Equipment List

V. Safety Measures (Top Priority)

Due to the flammable and explosive nature of coal powder, safety measures are the core of the entire solution.

5.1 Inert Gas Protection

Nitrogen is introduced into the closed system and circulated. An online oxygen content monitor keeps the oxygen concentration strictly below the safe limit, fundamentally eliminating combustion and explosion conditions. The mill is designed with an inert gas inlet for easy integration of the fire‑suppression system.

5.2 Ignition Source Control

5.3 Explosion Venting and Pressure Relief Devices

Multiple explosion‑relief valves are installed inside the Raymond mill to provide early pressure relief and prevent damage from spreading. The mill shell should be capable of withstanding 345 kPa of explosion pressure, and explosion‑relief valves are provided at the top.

5.4 Gas and Temperature Monitoring

CO‑O₂ gas analysers and temperature sensors are installed at the inlet, outlet, and bag filter outlet:

• Temperature exceeding the preset alarm level → alarm
• CO concentration exceeding the preset alarm level → audible/visual alarm → start fire‑suppression system

5.5 Sealing and Anti‑Accumulation Design

• All equipment, piping and coal powder silos must be reliably sealed to prevent fresh air leakage
• The classifier, dust collector and all non‑standard air ducts should be insulated to prevent condensation and coal dust accumulation
• Air‑lock devices are installed at each discharge point
• Temperature and pressure monitoring points are set at each hopper of the dust collector to ensure no dust accumulation

VI. Main Applications of Coal Powder

Coal powder is an important industrial raw material and fuel with a wide range of applications.

6.1 Main Application Areas

6.2 Detailed Applications in Various Industries

(1) Thermal Power Generation (largest consumer)

Coal powder is the most basic and important fuel in coal‑fired power generation. It is suitable for large coal‑fired units above 300 MW. The thermal energy from coal powder combustion is converted into electrical energy.

(2) Cement Industry

Coal powder is the main fuel for cement rotary kilns, offering high combustion efficiency and significant influence on the quality of cement clinker.

(3) Iron & Steel Metallurgy (Blast Furnace Injection)

Injecting coal powder through blast furnace tuyeres can replace part of the expensive coke, reducing iron‑making costs. The coke replacement ratio can reach up to 200 kg/t iron.

(4) Foundry Industry

Adding coal powder to green sand for iron castings can prevent burn‑on surface defects, improve surface finish, reduce sand‑inclusion defects, and enhance the collapsibility of the moulding sand.

(5) Industrial Boilers and Kilns

Coal powder can be used in high‑efficiency pulverised‑coal boilers, lime kilns, rotary kilns, etc. Low‑dust coal powder combustion technology can be applied to retrofit oil‑fired industrial kilns to coal‑fired operation.

(6) Coal Chemical Industry

Coal powder can be used to produce chemicals such as activated carbon and humic acid. The clean and efficient utilisation of coal has been included in national development plans, and the future of deep coal processing is promising.

(7) Clean Coal Powder

Coal powder has high combustion efficiency and low harmful impurity content, making it an energy‑saving and environmentally friendly fuel.

VII. Investment and Economic Estimates (Reference)