Working Principle, Process, and Advantages of Air Screen cleaner with Gravity separator for Soybeans and Sesame

I. Working Principle

The working principle of the air-screen gravity cleaner can be broken down into two core mechanisms—air separation and gravity-based stone removal—complemented by a screening process. Together, these three elements form a comprehensive separation logic.

1. Air Separation Principle — Removing light impurities based on "suspension velocity/density"

Upon entering the equipment, the material first passes through an air-suction or air-blowing system. As the airflow acts on the material, the various components—differing in density, projected area, and orientation relative to the wind—exhibit distinct "suspension velocities."

Light impurities (such as straw, husks, weed seeds, dust, and shriveled grains) have a low suspension velocity; they are easily lifted by the airflow and drawn away by the suction system toward the dust/light-impurity outlet.

Heavier materials, such as soybeans or sesame seeds, possess a high suspension velocity. They remain unaffected by the standard airflow and continue to descend into the screening and gravity-separation stages.

By precisely adjusting the air volume and pressure, a clear separation between light impurities and the target product can be achieved. For instance, because sesame seeds are tiny and highly sensitive to airflow, a gentler, more stable, and lower-velocity airflow is required to prevent the product itself from being inadvertently drawn out; soybeans, by contrast, can withstand a slightly higher airflow volume.

2. Gravity-Based Stone Removal Principle — Separating stones of similar size based on "density differences"

This serves as the machine’s primary mechanism for removing stones, relying on the physical effects of a "fluidized bed" combined with "automatic stratification." The material is fed onto a perforated destoning screen (also known as a vibrating destoning deck). A continuous upward airflow from beneath keeps the material in a "semi-suspended, fluidized" state on the screen surface.

Driven by this airflow, the material layer undergoes automatic stratification: denser impurities—such as stones, clods of soil, or metal fragments—sink and settle directly against the screen surface, while the lighter product (e.g., beans or sesame seeds) rises to the top.

The screen vibrates with a specific frequency and amplitude, propelling the heavy impurities—which are in contact with the screen surface—toward the discharge end (the elevated end), where they are removed via an outlet.

Meanwhile, the lighter, cleaned product moves along the screen surface toward the discharge end (the lower end) and exits through the product outlet.

3. Auxiliary Screening — Separating Impurities by Size

In addition to air separation and gravity-based separation, equipment is typically equipped with one or more screening layers. These serve to intercept large impurities (such as straw, husks, and large stones) and remove small impurities (such as broken grains and fine sand), acting as a complement to air and gravity separation to ensure a clear division of functions across each separation stage.

II. Workflow

The complete cleaning process for soybeans or sesame seeds using an cleaner can be summarized into five stages: feeding, air-based removal of light impurities, screen-based removal of size-based impurities, gravity-based stone removal, and the multi-channel discharge of cleaned product and various impurities.

1. Uniform Feeding and Initial Dispersion

Material is delivered into the feed hopper via an elevator. A distribution mechanism ensures the material is spread evenly as it enters the equipment, guaranteeing that every individual grain or seed is fully exposed to the airflow and screen surface, thereby preventing clumping or "dead zones" that could hinder separation.

2. Air-based Removal of Light Impurities (First Stage of Separation)

As the material enters the air-separation zone, light impurities—such as straw, pod husks, weed seeds, dust, and shriveled/empty grains—are lifted by the airflow and directed into a dust collection system. The heavier, sound material continues downward into the screening and gravity-separation zones. For sesame, the airflow should be reduced to prevent the product itself from being drawn out, while for soybeans, the airflow can be increased accordingly.

3. Screen-based Removal of Size-based Impurities (Second Stage of Separation)

The material passes through a screening mechanism, where large impurities (oversized debris) are trapped and discharged, while smaller particles—such as broken grains, fine sand, and debris—are sifted out. This process also achieves an initial classification of the soybeans or sesame seeds based on particle size.

4. Gravity-based Stone Removal (Third Stage of Separation – Core Process)

The material moves onto a gravity-separation (destoning) screen. Through a combination of fluidization (via airflow) and vibration-induced auto-stratification, heavy impurities—such as stones (including those similar in size to the product), clods of soil, insect-damaged grains, and moldy grains—sink to the bottom and are conveyed toward the discharge end for removal. Meanwhile, the sound material "floats" to the top and flows toward the main product outlet. This is the critical stage for ensuring the final product meets purity standards.

5. Multi-channel Discharge and System Integration

The equipment ultimately separates the material into distinct streams: the cleaned product (for the next stage of processing), light impurities (dust, straw, etc., sent to the dust collection system), heavy impurities (stones, soil clods), and size-based impurities (broken grains, fine sand). In a complete cleaning line, this machine is typically positioned after the vibrating grading screen, serving as the primary unit for precision destoning and the removal of impurities similar in size to the grain. Downstream, it can be integrated with a magnetic separator (for iron removal) and a polisher or color sorter (to enhance the commercial value of the product).

III. Core Advantages

1. Multi-functional in a Single Unit for Comprehensive Impurity Removal

A single machine performs three types of separation—removing light impurities, size-based impurities, and stones of similar size—eliminating the need for a series of single-function machines. This results in a smaller footprint, lower investment costs, and a compact processing workflow.

2. High-Precision De-stoning with Purity Levels Exceeding 99.5%

Utilizing the principle of gravity-based separation, the system effectively removes stones, insect-damaged grains, and moldy kernels—even when they are similar in size to the target product but differ in density. This is crucial for enhancing the commercial value of pulses and oilseeds, consistently meeting the purity standards required for export trade.

3. Flexible Switching Between Soybeans and Sesame (High Versatility)

The system can be easily adapted for different commodities—such as soybeans and sesame—by simply changing the screen mesh size, adjusting airflow volume and pressure, and fine-tuning vibration amplitude and frequency. This allows a single machine to handle multiple types of materials, significantly increasing equipment utilization.

4. Minimal Damage to Delicate Materials like Sesame

The air-separation system employs a gentle airflow, while the gravity-separation screen is designed with low-amplitude vibration. Parameters are optimized to account for the specific characteristics of soybeans (round shape) and sesame (small size), minimizing breakage, hulling, and crushing damage, thereby preserving the commercial value of the oilseeds.

5. Sealed Dust Removal for an Eco-friendly, Clean Environment

The integrated design—incorporating negative/positive pressure air circuits and a dust-collection mechanism—ensures centralized dust recovery. This maintains a clean working environment and complies with standards for export processing and food hygiene.

IV. Scope of Application

Applicable Materials: Primarily soybeans and sesame; also suitable for various other oilseeds and pulses (including peanuts, rapeseed, sunflower seeds, black soybeans, kidney beans, white kidney beans, etc.).

The Hebei Taobo Machinery  cleaner employs a three-in-one mechanism—combining air separation (to remove light impurities), screening (to remove impurities based on size), and gravity separation (to remove stones of similar size to the product)—to achieve efficient, precise, and low-damage cleaning of oilseeds such as soybeans and sesame. Offering advantages such as multi-functional versatility, high purity, flexible switching between different crop varieties, and eco-friendly, clean operation, it serves as a core dry-processing unit for establishing a quality assurance system that transforms raw materials into commercial-grade oil seeds.