Centrifugal Fans for Grain Processing Plants: Applications + Complete Selection Guide

For grain processing plants (rice mills, flour mills, corn processing plants, and grain cleaning lines), centrifugal fans are the preferred choice.

Core advantages: High pressure capability, able to overcome pipeline resistance and grain-layer resistance, suitable for enclosed duct systems.

Axial fans have lower pressure and are mainly used for open warehouse ventilation, rarely for production line applications.

1. Main Applications of Centrifugal Fans in Grain Processing Plants (6 Key Areas)

1. Pneumatic Conveying (Grain Suction / Transport, Bran, Rice Husk, Broken Grain Conveying)

The airflow carries granular materials through pipelines for lifting and transferring wheat, corn, rice, bran, and rice husks.

Requirements:

• Medium to high pressure
• Wear-resistant impeller
• Prevent abrasion caused by particle impact

2. Grain Cleaning and Separation (Stone Removers, Cleaning Screens, Air Separators)

Using airflow separation to remove:

• Light impurities
• Dust
• Empty grains
• Weed seeds

Heavy grains fall down while lighter materials are blown away.

Centrifugal fans are standard equipment in grain cleaning sections.

3. Drying System Air Supply / Moisture Exhaust

(Grain Dryer Hot Air Circulation and Exhaust)

Hot air enters the grain layer to remove moisture, while exhaust fans remove humid air.

Note:
For hot and humid air conditions, high-temperature resistant fan models should be selected.

4. Dust Collection and Air Purification

(Pulse Dust Collectors, Rice Milling / Flour Milling Dust Extraction)

Used for collecting:

• Rice milling dust
• Flour dust
• Bran ash

Benefits:

• Improves workshop environment
• Reduces dust pollution

⚠️ Flour and starch processing areas must consider dust explosion protection.

5. Grain Storage Ventilation and Cooling (Silo Aeration)

Airflow penetrates the grain layer to:

• Remove heat
• Prevent mold growth
• Control grain temperature

The higher the grain pile, the higher the required pressure. Centrifugal fans are usually required.

6. Finished Product Cooling

Used after drying to cool grains and prevent:

• Grain cracking
• Quality deterioration
• Mold formation

2. Common Centrifugal Fan Models for Grain Industry

4-72 / 4-79 Centrifugal Fans (Low Pressure)

Applications:

• Dust removal
• Workshop ventilation
• Cleaning screen air separation
• Light impurity removal

Features:

• Lower pressure
• Not suitable for long-distance grain conveying

6-30 / 6-41 / 6-23 Medium Pressure Fans (Grain Machinery Fans)

✅ Mainstream models for grain processing plants.

Commonly used for:

• Air separation
• Short-distance pneumatic conveying
• Grain dryer circulation air

9-19 / 9-26 High Pressure Centrifugal Fans

Applications:

• Long-distance grain suction
• Long pipeline conveying
• Systems with high resistance

Simple Selection Rule:

• Short pipeline air separation → 6 series
• Long-distance grain conveying → 9 series
• General dust removal and ventilation → 4-72 series

3. Step-by-Step Fan Selection Method

Step 1: Determine Air Volume Q (m³/h)

1) Grain cleaning equipment:

Use the recommended fan parameters provided by the equipment manufacturer.

2) Pneumatic conveying:

As an experience reference:

For grain conveying:
800–1200 m³/h airflow per ton of grain

(Longer pipelines require higher airflow.)

3) Grain drying systems:

Select according to the dryer manufacturer’s airflow requirements.

4) Grain storage ventilation:

For wheat/corn:
6–10 m³/h per ton of grain

Safety Margin:

Required airflow = Calculated airflow × 1.1–1.2 safety factor

Step 2: Calculate Total Pressure (Most Important)

Fan total pressure should be:

Fan pressure ≥ System resistance × 1.1–1.2

System resistance includes:

• Pipeline friction loss
• Elbow and reducer losses
• Grain layer resistance
• Dust collector resistance

⚠️ Common mistake: Selecting only according to airflow while ignoring pressure.

Result:

• Airflow exists but cannot move grain
• Pipeline blockage
• Insufficient drying performance

Step 3: Select Fan Structure and Material

Impeller Blade Type

Forward Curved Blades (6 Series)

• Higher pressure at the same size
• Widely used in grain machinery

Backward Curved Blades (4-72 Series)

• Higher efficiency
• Less dust accumulation
• Mainly used for ventilation and dust removal

Radial Blades

• Excellent wear resistance
• Suitable for high-concentration particle conveying

Wear Resistance Requirements

Conveying:

• Raw grain
• Broken grain
• Bran

Recommended:

• Thickened impeller plates
• Wear-resistant coating

Clean air / General dust removal:

Normal Q235 carbon steel is usually sufficient.

Explosion Protection Requirements

✅ Flour mills, starch plants, and rice milling workshops may contain combustible dust.

Required:

• Dust explosion-proof motor Ex tD A21
• Prevent friction sparks between impeller and casing
• Avoid using standard non-explosion-proof fans

For grain cleaning workshops with low dust concentration:

• Standard motors may be acceptable

Transmission Type

Direct Drive (A Type)

Advantages:

• Simple structure
• Low maintenance

Suitable for:

• Small and medium-sized fans

Belt Drive (C/D Type)

Advantages:

• Flexible speed adjustment
• Suitable for unstable operating conditions
• Easy future frequency converter upgrade

Temperature Selection

Normal temperature:

• ≤80℃

Hot air drying systems:

• 100℃

Require:

• High-temperature bearings
• Reinforced casing design

Step 4: Motor Power and Variable Frequency Drive (VFD)

For continuous 24-hour operation:

• Reserve 10% motor power margin

For unstable operating conditions:

• Production fluctuations
• Wet/dry grain changes

Recommend:

• VFD control

Benefits:

• Energy saving
• Adjustable airflow and pressure
• Avoid excessive system pressure

4. Common Fan Selection Mistakes in Grain Plants

❌ Copying old fan parameters while pipelines are extended or more elbows are added
→ Insufficient pressure

❌ Using 4-72 low-pressure fans for long-distance grain conveying
→ Frequent material blockage

❌ Using non-explosion-proof fans in flour processing areas
→ Serious dust explosion risk

❌ No safety margin reserved
→ Small increases in resistance cause rapid airflow reduction

❌ Hard connection between fan and pipeline without flexible connector
→ Vibration transmission causes cracks and structural damage

5. Quick Fan Selection Information Template

(You Can Send Directly to Fan Manufacturers)

Application:
Cleaning screen / Grain conveying / Dryer / Dust collection

Required airflow:
____ m³/h

Required total pressure:
____ Pa

Medium:
Normal temperature / Hot air ____℃
Dust content / Grain particle conveying?

Dust explosion protection required:
Yes / No

Transmission type:
Direct drive A / Belt drive C or D

Power supply:
380V
Need VFD control? Yes / No