How should high-pressure condensate flash steam be controlled to maximize heat recovery?
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How should high-pressure condensate flash steam be controlled to maximize heat recovery? Is it by directly reducing the pressure to a slight positive pressure? Then the heat is fully recovered and transported by the bottom condensate pump. Or flash it to 2-3 kilograms and then discharge the condensate under its own pressure?
I saw the steam pipeline system in a Taiwanese-owned enterprise: the boiler generates steam at 3.6–4.0 MPa, which is used by some of the equipment； The remaining steam with a pressure of 3.6 MPa is cooled and depressurized to 1.6 MPa before entering the medium-pressure balance tank; all the condensate generated from the 3.6 MPa steam goes into the medium-pressure steam balance tank. The steam at 1.6 MPa in this tank is used by another unit, while any excess steam at 1.6 MPa is further depressurized to 0.8 MPa, and together with the condensate at 0.8 MPa, it enters the low-pressure balance tank for use in heating, purging, and tank area operations. The steam from this branch line is further depressurized to 0.3 MPa, and together with the condensate at 0.8 MPa, it enters the ultra-low pressure balance tank. The steam at 0.3 MPa is used for heat removal, deoxidization processes, lithium bromide-based systems, and low-temperature heating; after being cooled, the ultra-low pressure condensate is used as feedwater for boilers, while the liquid from this branch line is used to replenish the circulating water. All steam from the steam traps is recovered into the balance tank; there is no discharge of steam condensate at the site. Even if some leakage occurs in the steam traps, it has little impact, as this leakage can be adjusted by reducing the opening degree of the pressure control valve.
A flash tank can be installed to flash the high-temperature condensate into steam at a stable pressure, which is then supplied to equipment operating in a low-pressure environment. The condensate is recovered through steam traps and can be reused in boilers.
This depends on how the steam produced after flashing is utilized. If a slight positive pressure is achieved during flashing, then the most heat will be transferred to the flashing steam; however, such steam will have a low temperature and thus limited utility. If the pressure reaches around 2-3 kilograms, with a temperature of slightly over 120 degrees, then it can be used in other applications, which would be great. So the key lies in the downstream uses of the flashing steam