A blowdown separator is the best choice when space limitations preclude using a large tank to collect and hold the effluent while it cools to an acceptable drain temperature. The blowdown separator accepts boiler blowdown, vents the portion that flashes to steam, but does not store the effluent until it cools. Instead, a temperature controlled mixing valve mounted in the tank’s discharge piping adds cold make-up water to cool the effluent as it immediately discharges to the drain.
- Standard blowdown separator design pressure is 50 psi; the tank’s vent is sized to limit the vessel pressure to 5 psi
- Boiler blowdown enters the vessel’s lower-pressure environment, where approximately 30% flashes to steam, then flows out the tank’s vent or can be piped so that its latent heat is recovered and used to preheat boiler feedwater
- Blowdown effluent collects in the bottom of the tank, where a mixing valve in the tank’s discharge piping adds cold make-up water, cooling the effluent below 140°F as it immediately discharges to the drain
- Most commonly used where space limitations preclude a large tank