A tube mill is a type of long, horizontal grinding mill widely used in the cement industry, mining, metallurgy, and chemical industries. Because a tube mill has a large length-to-diameter ratio and operates continuously for long periods, the feeding device structure has a significant influence on mill capacity, energy consumption, liner wear, and operational stability.

The main functions of a tube mill feeding device are:

• Feeding materials into the mill continuously and evenly
• Preventing material leakage and dust escape
• Reducing blockage during feeding
• Adapting to the rotation of the mill
• Reducing wear on feeding components

1. Main Components of a Tube Mill Feeding Device

A typical feeding system consists of:

Feeding Equipment
        ↓
Feed Chute
        ↓
Feed Pipe
        ↓
Feed Screw
        ↓
Mill Chamber

Main components include:

1. Feed Chute

Function:

• Receives material from belt conveyors, bucket elevators, or screw conveyors
• Guides material into the mill

Structure:

• Welded steel construction
• Lined with wear-resistant steel plates or ceramic liners

2. Feed Pipe

The feed pipe connects the external feeding system with the inside of the mill.

Common materials:

• Carbon steel plate
• Wear-resistant steel
• Cast steel

Requirements:

• High wear resistance
• Anti-blocking design
• Easy replacement and maintenance

3. Feed Screw

A screw conveyor is installed inside the feeding section of the mill.

Functions:

• Pushes material into the mill
• Prevents material backflow

Types:

• Single-start screw
• Double-start screw

2. Main Structural Types of Tube Mill Feeding Devices

1. Trumpet-Type Feed Device (Chute Feeding)

This is one of the simplest and most traditional feeding structures.

Structure:

The feed inlet has a trumpet or funnel shape:

        Material
            ↓
        \       /
         \     /
          \   /
          Feed Pipe
              |
          Mill Shell

Working Principle:

Material enters the mill by gravity.

Advantages:

✅ Simple structure
✅ Low manufacturing cost
✅ Easy maintenance

Disadvantages:

❌ Poor sealing performance
❌ More dust leakage
❌ Limited application for large mills

Application:

• Small tube mills
• Open-circuit grinding systems

2. Screw-Type Feeding Device

This is one of the most commonly used feeding systems in industrial tube mills.

Structure:

A screw conveyor is installed inside the feed pipe.

Feed inlet
    ↓
=================
  Screw blades
=================
    ↓
Mill chamber

Working Principle:

During operation:

1. Material enters the screw section
2. The rotating screw pushes the material forward
3. Material enters the first grinding chamber

Advantages:

✅ Continuous and stable feeding
✅ Prevents material backflow
✅ Suitable for high-capacity mills

Disadvantages:

❌ Screw blades wear quickly
❌ Replacement can be difficult

Applications:

• Cement tube mills
• Mining ball mills

3. Combined Feed Device (Chute + Screw)

This is a common design for large tube mills.

Structure:

It consists of:

1. External feed chute
2. Internal screw cylinder
3. Feed cone

Flow:

Material
    ↓
Feed Chute
    ↓
Feed Cone
    ↓
Screw Conveyor
    ↓
First Grinding Chamber

Features:

• Combines gravity feeding and screw conveying
• Better sealing performance
• Suitable for large production capacity

Applications:

• Large cement mills
• Slag grinding mills

4. Central Feeding Device

Material enters through the center axis of the mill.

Structural Features:

• Feed opening located at the center of the hollow shaft
• Material enters along the mill centerline

Advantages:

✅ Uniform material distribution
✅ Reduces uneven feeding
✅ Suitable for large mills

Disadvantages:

❌ More complicated structure
❌ Higher manufacturing precision required

5. Composite Feeding Device

Used for large-capacity and heavy-duty tube mills.

Structure includes:

• Feed chute
• Screw feeder
• Guide cone
• Wear-resistant liners
• Sealing system

Features:

• High reliability
• Large feeding capacity
• Long service life

Applications:

• Cement production lines
• Large mining grinding systems

3. Comparison of Different Feeding Structures

4. Design Requirements for Tube Mill Feeding Devices

1. Wear Resistance

Because the incoming materials often contain:

• Quartz
• Iron ore
• Cement clinker
• Slag

The feeding parts experience severe abrasion.

Common materials:

• NM400 wear-resistant steel
• High manganese steel
• Cast stone liners
• Ceramic liners

2. Good Sealing Performance

The feeding system should prevent:

• Dust leakage
• Air leakage
• Material overflow

Common sealing methods:

• Graphite seals
• Rubber seals
• Labyrinth seals

3. Uniform Feeding

Stable feeding affects:

• Mill capacity
• Product fineness
• Power consumption

5. Typical Feeding Arrangement in Mining/Cement Tube Mill Systems

Example: Φ2.4 × 8 m tube mill

Belt Conveyor
       ↓
Feed Hopper
       ↓
Feed Chute
       ↓
Screw Feeder
       ↓
First Chamber
       ↓
Grinding by Impact and Attrition
       ↓
Second Chamber
       ↓
Discharge