A coal drum dryer, also known as a rotary dryer or drum dryer, is a key piece of equipment in modern coal processing and utilization. Its primary purpose is to reduce the moisture content of high-moisture wet coal (such as raw coal, washed coal, and coal slime) to a level suitable for subsequent use through efficient heat exchange.
I. Working Principle
A coal drum dryer operates based on direct or indirect heat transfer, with direct heating being the most common. Its workflow can be summarized in the following steps:
Feeding and Dispersion: High-moisture wet coal is uniformly and continuously fed into the feed end of the drum dryer via a feeder (such as a belt conveyor or scraper conveyor). Lifting plates are installed on the inner wall of the drum. As the drum rotates, these plates continuously lift and drop the material, forming a uniform curtain, significantly increasing the contact area between the material and the hot air.
Hot Air Contact Drying: High-temperature drying medium (hot air) from a heat source system (such as a hot air furnace or gas burner) enters the drum in either co-current (co-directional) or counter-current (opposite) directions with the material. In the co-current method, the wettest material meets the hot air at the highest temperature, rapidly evaporating surface moisture without over-combustion. In the counter-current method, the driest material meets the hottest gas, resulting in high drying intensity but also requiring high heat resistance.
Heat Transfer and Moisture Evaporation: As the material is repeatedly lifted and dropped within the drum, it undergoes extensive heat exchange with the hot air. The material absorbs heat, rapidly vaporizing moisture within and on its surface.
Exhaust Gas Emission and Product Collection: The evaporated water vapor, along with the cooled and humidified exhaust gas, is drawn out of the drum by an induced draft fan. It is then purified by a subsequent dust removal system (such as a bag filter or cyclone) before being discharged. The dried coal, with its reduced moisture content and finer particle size, is discharged from the drum as a dry coal product meeting the required standards.
II. Main Application Areas
Coal drum dryers are widely used in the following scenarios:
Coal washing plants: Dehydrate and dry clean coal after washing to increase its calorific value and transportation efficiency.
Coal slime drying: Dry high-moisture, high-viscosity coal slime, a byproduct of coal washing, into commercially valuable fuel, turning waste into treasure.
Steam coal pretreatment: Reduces the moisture content of fuel coal for power plants, improving combustion efficiency and reducing transportation costs.
Bracket/coal slurry preparation: Provides raw coal with the correct moisture content for briquette production lines or coal slurry preparation.
Lignite upgrading: Drys high-moisture, self-igniting lignite to increase its calorific value and economic value, facilitating long-distance transportation and storage.
In summary, coal drum dryers, with their mature technology, powerful processing capacity, and excellent economic efficiency, play an irreplaceable role in the clean and efficient utilization and resource recovery of coal. With continuous technological advancement, they are continuously developing towards greater energy efficiency, environmental friendliness, and intelligence.
