Belt dryer
Encyclopedia
A belt dryer
is an apparatus which is used for continuous drying and cooling of pellets, pastes, moulded compounds and panels using air, inert gas
, or flue gas
.
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.
Different kinds of dryers are possible to construct, e.g.
, wood fiber insulating boards, paints, molding materials, synthetic rubber, superabsorbent polymer
, stearate
, catalysts, coke, fruits, vegetables, cereals.
Drying
Drying is a mass transfer process consisting of the removal of water or another solvent by evaporation from a solid, semi-solid or liquid. This process is often used as a final production step before selling or packaging products. To be considered "dried", the final product must be solid, in the...
is an apparatus which is used for continuous drying and cooling of pellets, pastes, moulded compounds and panels using air, inert gas
Inert gas
An inert gas is a non-reactive gas used during chemical synthesis, chemical analysis, or preservation of reactive materials. Inert gases are selected for specific settings for which they are functionally inert since the cost of the gas and the cost of purifying the gas are usually a consideration...
, or flue gas
Flue gas
Flue gas is the gas exiting to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator. Quite often, the flue gas refers to the combustion exhaust gas produced at power plants...
.
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.
Design features
Belt dryers / Belt coolers are designed in modular system. Each belt dryer consists of infeed head, 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.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:- Chemical Industry
- Pharmaceutical industry
- Food and feeding-stuff industry
- Non-metallic minerals industry
- Plastics industry
- Wood industry
- Ceramics Industry
Product examples
VeneersWood veneer
In woodworking, veneer refers to thin slices of wood, usually thinner than 3 mm , that are typically glued onto core panels to produce flat panels such as doors, tops and panels for cabinets, parquet floors and parts of furniture. They are also used in marquetry...
, wood fiber insulating boards, paints, molding materials, synthetic rubber, superabsorbent polymer
Superabsorbent polymer
Superabsorbent polymers are polymers that can absorb and retain extremely large amounts of a liquid relative to their own mass....
, stearate
Stearic acid
Stearic acid is the saturated fatty acid with an 18 carbon chain and has the IUPAC name octadecanoic acid. It is a waxy solid, and its chemical formula is CH316CO2H. Its name comes from the Greek word στέαρ "stéatos", which means tallow. The salts and esters of stearic acid are called stearates...
, catalysts, coke, fruits, vegetables, cereals.
Sources and further reading
- Sattler, Klaus: Thermische Trennverfahren. 3. Aufl. Weinheim: Wiley-VCH, 2001
- Draxler, J.: Skriptum zur Vorlesung Thermische Verfahrenstechnik. Loeben: Montan Universität, 2002
- Krischer, O.; Kast, W.:Trocknungstechnik – Die wissenschaftlichen Grundlagen der Trocknungstechnik. 3. Band. 3.Aufl. Berlin: Springer, 1992