The core function of a gravity separator in grain cleaning is to separate materials that are “similar in size but different in quality” based on the difference in density (specific gravity) between grains and impurities. It is particularly adept at removing defective grains and impurities with abnormal density, making it a key piece of equipment for improving grain quality.
I. Core Function: Precise Separation of “Materials with Density Differences” In grain cleaning, screening machines (sorted by size) and air separators (sorted by weight) cannot handle materials that are “similar in size and appearance but different in density.” The gravity separator fills this gap, and its specific functions can be divided into two categories:
1. Removing “Defective Grains” from Grains During the growth and harvesting process, grains may contain immature grains, insect-damaged grains, moldy grains, broken grains, and other defective grains. These grains are similar in size to normal grains, but due to their loose internal structure (e.g., immature grains) and voids (e.g., insect-damaged grains), their density is much lower than normal grains. A gravity separator can precisely separate these.
Typical scenarios: 1. Wheat cleaning: Removing shriveled, wrinkled, and immature wheat grains;
2. Rice cleaning: Separating sprouted and moldy broken rice;
3. Bean cleaning: Removing hollow beans damaged by insects.
2. Separating “Impurities of similar size but different densities”: Some impurities (such as pebbles and glass shards) are similar in size to grain particles and cannot be separated by screening machines, but their density is much higher than that of grains; other lightweight impurities (such as plastic flakes and weed seeds) have a lower density than grains and are difficult for air separators to completely remove, but can be separated by a gravity separator based on density differences.
II. Working Logic: “Airflow + Vibration” Facilitates Density Separation
The gravity separator operates on a unique principle: it uses “airflow suspension + table vibration” to stratify materials by density, then separates them through a conveying mechanism on an inclined table. The specific steps are as follows:
* **Airflow Suspension:** Low-pressure airflow is introduced below the gravity separator’s sorting table (perforated plate). The airflow passes through the sieve holes and rises, creating a “loose suspension state” for grains and impurities, thus facilitating density separation.
* **Density Separation:** Denser, normal grains (such as plump wheat grains) are more affected by gravity and overcome airflow resistance, sinking to the bottom of the sorting table. Denser, defective particles (such as immature grains) and light impurities float on the surface.
* **Vibration Separation:** The sorting table is tilted and vibrates at high frequency. Normal grains at the bottom are conveyed forward along the tilt direction, eventually entering the “finished product channel.” Low-density defective particles and impurities on the surface are pushed in the opposite direction into the “impurity channel,” achieving separation.
* III. Position in the Grain Cleaning Process: “Fine Purification Stage” The gravity separator is not the first step in grain cleaning, but rather a “subsequent fine purification device.” It is usually used in conjunction with other equipment. A typical process is as follows: Raw grain → air separation (removing light impurities: broken husks, dust) → screening (removing impurities of different sizes: large stones, weeds) → magnetic separation (removing magnetic metals) → gravity separator (removing defective particles, impurities with abnormal density) → color sorting (removing discolored impurities) → finished product is visible. The gravity separator’s role is “secondary purification.” After basic impurities are removed, it further improves the purity and quality of the grain, meeting the high standards required for food processing (such as polished rice and flour) or seed-grade grains.
Post time: Nov-04-2025
