In steam drying processes, goods are dried in a steam atmosphere. The process steam is circulated and reheated by a natural gas burner. The water removed from the product is present in the form of excess steam. Usually, the excess steam cannot be used further because there is no heat demand at this temperature and it is therefore wasted.
Open loop heat pumps, also called Mechanical Vapor Recompression (MVR) allow for recovery of the excess steam, it is used as thermal energy source. In the open loop heat pump, the dryer is the evaporator of the heat pump. The compressor increases the pressure level of the excess steam, so that is can be condensed at higher temperatures. In the condenser, the hot excess steam reheats the process steam of the dryer. Thereby the natural gas burner can be replaced.