Superheated Vapor Dryers
Superheated Vapor Dryer is an indirect-heated pneumatic dryer in which water in the product produces steam at 0.5 to 4 bar gauge pressure. There is no air or flue gas in contact with the product, and no emissions to the atmosphere produced. Boiler steam, flue gas, thermal oil, or even hot water can be used as indirect heating media. In comparison to open-type dryers, the SVD consumes less gross energy (about 1,280 BTU/pound of evaporated water). The heat recovery in the evaporated water (steam) is about 1,025 BTU/pound. Sludge, bark, and wood waste can be dried to 90–95% dryness before being used as fuel. This results in a maximum and stable production of heat from the boiler, which can be used for heating or as power production in a steam turbine. Only part of the steam is used for heating the SVD; about 80% is recovered by using the generated steam from the dryer in a pulp and paper or other process.