Drying of biomass (sugar cane bagasse, wood bark, sawdust, wood shavings and other types) serves as a preliminary stage of pelleting, briquetting and gasification. Reducing the moisture of biomass to 10-15%, its calorific value is increased from 2kWh/kg to approximately 4.5kWh/kg.
This process reduces the costs of transport, storage and creates ideal conditions for direct combustion or biomass briquettes for high quality. The drying process also ensures the reduction of emissions during combustion of the biomass and also reduce the amount of biomass consumed during burning.
This type of dryer is universal and is basically a rotating drum that inputs both the product to dry and heat drying fluid at an elevated temperature (300-800 ° C).
In the case of the indirect drying, heat transfer fluid is the actual air heated through a heat exchanger, passing through the dryer and biomass and through a condenser to separate the substance evaporated, to be heated and then returns to be used again.
So is formed a closed circuit. The only are the emissions to the atmosphere gases from the heat zones. A process of high efficiency environmental point of view, suitable for products which are highly toxic volatile substances.
Rotary Biomass Dryer of One Stage
One stage dryers are built with fins welded inside the dryer by the total length of its drum.
While the drum rotates at a constant speed, the fins raise the biomass and continuously pass it through a hot air source. At the same time, specially designed barriers maintain a consistent mechanical and pneumatic transport of biomass particles through the dryer. The drying process takes place while the biomass is suspended in hot air source. When the proper amount of moisture is removed, the dry matter is transported to a collection system for the propeller blade of the dryer.
Rotary Biomass Dryer of Three Stages
The dryer of three stages consists of two concentric cylinders inside a large outer cylinder. These cylinders are fixed and aligned to rotate at the same speed. As the biomass passing through the inner cylinder is exposed to the higher temperature of the hot gases.
As the biomass is conveyed pneumatically to the outer cylinder by a fan, is exposed to lower temperatures and speeds of the hot gases and air. Finally, when the proper amount of moisture is removed, the biomass is transferred to the collector and separate from the flow of hot gases.