In continuous running plants or in equipment running on stable loads, flash steam can be recovered through a process of thermocompression and re-utilized in the plant.
A large number of industries vent flash steam to the atmosphere because it is at a low-pressure. At such a low temperature (typically 05 to 1 bar) it cannot be usefully redeployed in the process. However in continuous running plants, it is possible to utilize this steam using a device known as a Thermo-compressor.
A thermo compressor is a fluid jet device that enables compression of low pressure steam to a higher pressure. To achieve this high pressure steam is used as motive force in the compression process. In a thermo compressor high pressure motive steam accelerates through a nozzle. As the motive steam enters the suction chamber at supersonic speeds, it entrains and mixes with low pressure steam from the suction inlet. The resultant steam mixture then enters the convergent-divergent diffuser where its velocity reduces and pressure increases. Thus now the low pressure stream at the suction gets boosted to a higher pressure (typically equal to the low pressure steam pressure in the plant).This steam at a higher pressure can now be usefully utilized in the process.
Thus through the process of thermocompression, we can very easily increase the pressure of flash steam and thereby reclaim all the energy that was earlier being vented to the atmosphere. This scheme is most beneficial where the flash steam cannot be recovered to the boiler house (due to long distances or otherwise) and where the steam consumption in the process is fairly consistent.