- Source: Belt dryer
A belt dryer (belt drier) a kind of industrial dryer, is an apparatus which is used for continuous drying and cooling of woodchip, pellets, pastes, moulded compounds and panels using air, inert gas, or flue gas.
Working principle
A Belt dryer / Belt cooler is a device designed for the particularly gentle thermal treatment of product. The wet product is continuously and evenly applied through an infeed chamber onto a perforated belt. The belt, predominantly in horizontal position, carries the product through the drying area which is divided into several sections. In these cells drying gas flows through or over the wet product and dries it. Each cell can be equipped with a ventilating fan and a heat exchanger. This modular design allows the drying and cooling temperatures to be controlled separately in the different sections. Thus, each dryer cell can be individually controlled and the drying / cooling air flow can be varied in each cell. In addition, the speed of the conveyor belt can be varied what gives an additional parameter for setting of drying time. The cells can be heated or cooled directly or indirectly, and all heating media, such as oil, steam, hot water or hot gas can be used. Belt dryers are ideally suited to drying almost any non-flowing product and more granular products that require a lower throughput capacity.
Design features
Belt dryers / Belt coolers are designed in modular system. Each belt dryer consists of infeed hopper, conveyor belt and discharge end.
Different kinds of dryers are possible to construct, e.g.
Single-belt dryer
Multi-stage dryer
Multi-level dryer
Multi-belt dryer
Ventilation options
In general there are two ways of gas flow pattern. The drying air can flow, according to the treatment process, either through or over the product.
Heat Sources
HEAT EXCHANGERS:
These are commonly used for application where a biomass heat source is available such as woodchip boilers to produce hot water or if there is a steam heat source available.
OIL OR GAS FIRED BURNERS:
If a separate heat source is required a direct fired furnace with diesel, kerosene, LPG or natural gas burner can be used. Alternatively a heat exchanger with the same burner can be used for indirect heating if required.
Exemplary conveyor options
Chain-guided wire mesh conveyor
Chain-guided hinge slat conveyor
Chain-guided steel plate conveyor
Chainless wire mesh conveyor
Feeding variations
Granulating mill – filter cake or amorphous and paste-like products respectively
Slewing belt conveyor – sensitive and free flowing products
Distribution spiral
Rotatable arm feeding device – stable products
Plates feeding
Typical applications
Belt dryers are predominantly used in the following industries:
Biomass
Pelleting
Wood industry
Chemical industry
Anaerobic digestate
Pharmaceutical industry
Food and feeding-stuff industry
Non-metallic minerals industry
Plastics industry
Ceramics industry
Sources and further reading
Sattler, Klaus: Thermische Trennverfahren. 3. Aufl. Weinheim: Wiley-VCH, 2001
Draxler, J.: Skriptum zur Vorlesung Thermische Verfahrenstechnik. Loeben: Mountain Universität, 2002
Krischer, O.; Kast, W.:Trocknungstechnik – Die wissenschaftlichen Grundlagen der Trocknungstechnik. 3. Band. 3.Aufl. Berlin: Springer, 1992
References
External links
Picture of belt dryer for sawdust
Picture of belt dryer for grass, forage maize and various biomass products
Double Sided Timing Belt
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