To completely realize the savings from flash steam recovery, the flash steam separated should be used in applications which have a steam demand higher than the quantity of flash steam generated.
Flash steam is generated when the condensate is moved from a high to a lower pressure. In order to make up for the difference in sensible heat, the excess heat in condensate is used to boil a part of the condensate back to steam. This constitutes flash steam.
Flash steam separated from the condensate is suitable for applications which have a low pressure steam requirement. If full use is to be made of flash steam, ideally the application should be such that at all times its steam requirement should be equal to or exceed the flash steam supply. The deficit steam can be met from the main steam supply through a control valve arrangement.
If the supply of flash steam exceeds the demand for it in the process, then the surplus steam will have to be vented to the atmosphere leading to wastage of steam. Thus the expected savings from flash steam recovery will not be achieved.
Flash steam recovery to the boiler feedwater tank is a convenient application if the distance between the point of generation of flash steam and the boiler feedwater tank is not too long, and if the total quantity of flash steam generated can be absorbed by the feedwater tank.