The Ultimate Guide to Choosing Grain Cleaning and Screening Equipment

In grain processing, screening is often the first step. Grains are often contaminated with impurities such as stones and dust, and grains of varying particle sizes can be quite troublesome.

Therefore, cleaning and screening are the first steps in ensuring food safety—removing stones and other impurities ensures the safety of subsequent processing equipment and food. Therefore, choosing the right equipment is paramount.

The concept of cleaning and filtering:

Before selecting equipment, it’s important to understand the concepts of cleaning and screening to help you plan your purchase.

1. Cleaning: Cleaning focuses on “destruction,” removing impurities that could damage processing equipment and taint the quality of the finished product.

For example, stones can cause wear and tear on milling equipment during grinding, leading to malfunctions; dust can adhere to the surface of grain, reducing the hygienic quality of the finished product. Cleaning is like a “miner” during wartime, removing “mines” to allow the passage of incoming troops.

2. Screening: Screening focuses on “grading,” separating grains of varying particle size, shape, and quality into different grades.

For example, during wheat processing, wheat is screened, with full grains used for flour and small, empty grains used for feed. Rice is screened to separate grains of varying lengths and grade them into different rice products for sale.

Common cleaning or screening equipment:

Our company recommends six types of grain screening and cleaning equipment.

1. Circulating Air Separator

A circulating air separator utilizes the circulating airflow generated by a fan to lift lighter impurities toward a collection port, allowing heavier grains to fall vertically to the discharge port under their own gravity. This circulating airflow design improves wind power efficiency while also reducing energy consumption.

It removes low-gravity impurities such as dust, shriveled grains, and grass clippings, reducing impurities adhering to the grain surface and reducing dust pollution during subsequent processing. It can remove most light impurities before deep cleaning and screening, reducing subsequent workload.

The circulating air separator typically has a processing capacity of 65-150 tons/hour and is suitable for large-scale processing plants with daily outputs exceeding 200 tons. When integrated with a central dust removal system.

It can precisely separate and remove impurities using a PCL controller, meeting the efficiency requirements of continuous large-scale production while ensuring a clean production environment.

2. Rotary Vibrating Screen

The rotary vibrating screen operates on a vertical vibrating motor with eccentric weights mounted above and below the motor, producing three-dimensional vibrations on the screen surface: horizontal, vertical, and inclined.

Grains and impurities of varying particle sizes undergo a parabolic motion on the screen surface. Smaller particles pass through the sieve holes, while larger particles remain trapped. The rotary vibrating screen provides finer screening and evenly distributes the material, avoiding problems such as material accumulation and blind spots.

High-precision grain grading allows grains of varying particle sizes to be used in different product production, enhancing product differentiation and competitiveness. It can also screen out minute impurities from the grain, ensuring the purity of the finished product and improving product quality.

Current models of rotary vibrating screens have a processing capacity of 50-150 tons/hour, making them suitable for both medium-sized and large-scale processing plants. Multi-layer rotary vibrating screens can be used to separate grain impurities.

Some large-scale processing plants also feature variable frequency drive (VFD) and automatic screen cleaning functions, enabling adjustable vibration frequency and automatic screen cleaning.

3. Vibrating Screens

There are many types of vibrating screens, including linear vibrating screens and high-efficiency vibrating screens. A vibrating screen is driven by a motor to produce periodic vibrations, causing the screen surface to reciprocate.

During vibration, particles smaller than the aperture are screened out, while particles larger than the aperture are retained above and subsequently dispensed. The structure of a vibrating screen is relatively simple among cleaning and separation equipment, making it suitable for a wide range of screening scenarios.

Vibrating screens are used for preliminary separation, separating grain into large, medium, and small particles, making them convenient for producing and further processing rice of varying specifications.

They effectively utilize grain resources; they remove large impurities such as straw, hemp rope, and plastic lumps from grain, reducing subsequent production and processing risks and ensuring safe and stable operation of the production line; and they provide a preliminary separation of stones, reducing the burden on subsequent fine stone removal equipment.

Due to their simple structure and relatively low production capacity, ranging from 5 to 110 tons, vibrating screens are suitable for small, medium, and large processing plants.

For small processing plants, the typical hourly processing capacity is around 10 tons, sufficient to meet the screening needs of small production volumes. Medium- and large-scale processing plants typically operate in conjunction with other equipment or systems.

4. Gravity Concentrator

The principle of a gravity concentrator is density separation. Grains and impurities of varying densities are separated by a combination of a vibrating screen and airflow.

Dense grains sink to the lower layer of the screen, while less dense grains float to the upper layer. Reverse airflow or mechanical scrapers then separate the materials.

A gravity concentrator can remove low-quality grains, such as insect-damaged grains, shrunken grains, and diseased grains, significantly improving flour quality and ensuring high-end flour quality. Screening out extremely dense impurities like lead pellets and iron filings reduces the risk of serious accidents in subsequent processing equipment caused by these impurities.

In addition, compared to the limitations of vibrating screens in stone removal, a gravity concentrator can completely separate similar-sized stones from grains by adjusting airflow and vibration parameters, thereby improving grain purity.

Our gravity concentrator has a production capacity of 3-10 tons/hour and is suitable for small and medium-sized processing plants. Small processing plants typically process around 30 tons, and a 5-ton/hour gravity concentrator is a perfect fit. For medium-sized processing plants, typically processing over 50 tons, a 10-ton/hour gravity concentrator is required.

5. Destoner

Destoners are machines that focus on removing stones and are commonly used for grading and removing stones from grain particles. They can also remove pebbles from grains through air separation and perform seed selection for various grains. Destoners are used to remove stones and heavy impurities from grains and are suitable for a variety of industries.

Destoners specialize in removing stones and impurities from grains, particularly the common pebbles. Removing stones reduces damage to the equipment, improves product quality, and ensures smooth subsequent processing.

Destoners typically have a capacity of 3-22 tons/hour and are suitable for a wide range of processing plants, from small to medium-sized to large. For example, for a small flour mill, a 3-5 ton/hour destoner is generally sufficient to remove stones from wheat. Medium and large mills are typically integrated with other equipment to enhance the cleaning effect.

6. Planar Rotary Screen

Planar rotary screens use a gyratory motion to sieve the grain mixture across the screen surface, resulting in high screening efficiency and uniform material distribution.

Flat rotary screens offer finer screening, high overall strength, and easy grid installation and removal. Available in both fixed and mobile configurations, they are ideal for cleaning and screening large quantities of material.

Flat rotary screens reduce blind spots, improving screening accuracy and efficiency. For grains requiring high-precision grading, flat rotary screens can ensure effective grading while enhancing finished product quality.

ACME’s flat rotary screens have a production capacity of 4 to 20 tons per hour and are most suitable for medium-sized processing plants, which typically operate at 5 to 20 tons per hour. While they can be used in larger plants, the production volume is generally too high, limiting their use to a limited number of production lines.

Customer Concerns

1. Equipment Pricing

Equipment quotes are for the equipment only. Shipping and taxes are determined based on the customer’s location.

2. After-Sales Service

Our equipment, except for core components, is under warranty. Other components are covered by free replacement and repair within one year. If you have any questions, please contact our official website, and customer service will respond within 24 hours.

3. Equipment Customization

If the customer has additional requirements for the equipment, we can customize it to suit their needs; additional customization fees will apply.

4. Equipment and Environmental Safety

Our equipment meets all applicable standards. The noise level during operation does not exceed environmental standards, and the equipment is airtight, ensuring no dust or other leaks.