Recover waste heat with ORC technology

Last April, Siemens Energy (Erlangen, Germany; www.siemens.com/energy) introduced the Siemens organic Rankine cycle (ORC) modules, which enable operators of industrial plants to generate power from low-temperature (around 300°C) waste heat. Unlike a conventional Rankine cycle, which converts water to steam, the ORC vaporizes an organic fluid with a high molecular weight. The organic fluid has a boiling point lower than water, thus enabling heat to be recovered from low-temperature sources, such as biomass and biogas combustion, industrial waste heat (for example, in the glass and cement industries), geothermal heat, solar ponds and so on. The recovered heat is then converted into useful work, driving a turbine to generate electricity. The ORC module (flowsheet) consists of a turbine (with generator), a recuperator with condenser combined in a functional unit, a feed pump, pre-heater(s), an evaporator and the interconnecting piping. The vapor produced in the evaporator is supplied to the ORC turbine, which drives the generator. After leaving the turbine, the vapor enters the recuperator to transfer the energy from the superheated exhaust vapor to the liquid side of the process. Afterwards, it is condensed. The condensate (collected…