Deaerator

Deaerators are mechanical devices that remove dissolved gases from boiler feedwater. During the deaeration process, concentration of the dissolved carbon dioxide and oxygen is reduced to a level where corrosion is minimized; hence the steam generation system is protected from the harmful effects of corrosive gases. Figures show that in order to prevent corrosion in steam generation systems working with a pressure more than 200 psig, a dissolved oxygen level of at least 5 parts per million (ppb) is required. However the dissolved carbon dioxide is essentially completely removed during the deaeration.

Deaerators use steam to heat the water to the full saturation temperature corresponding to the steam pressure in the deaerator and to carry away dissolved gases. The deaeration system consists of deaeration tank, a storage tank and a vent. In the deaeration tank, water is heated and agitated by steam bubbling through the water. Steam is cooled by the incoming water and condensed at the vent condenser. Non-condensable gases and some steam are released through the vent. Steam provided to the deaerator provides physical stripping and action and heats the mixture of returned condensate and boiler feedwater make-up to saturation temperature. While most of the steam condenses, a small percentage of steam (5-14%) must be vented to accommodate the stripping requirements.

The deaerator is a vertical cylinder, 72 inches high, tangent to tangent, by 72 inches in diameter. It is supported in a pipe 14″ in diameter. Entry is through an 18″ diameter manhole in the side of the vessel. A metal frame is welded inside the deaerator to hold trays and rings

The storage tank is a horizontal cylinder 213″ long, tangent to tangent, by 72″ in diameter. Entry is through a 12″ x 16″ manhole in the north head.