A deaerating heater utilizes steam by spraying the incoming water into an atmosphere of steam in the preheated section (first stage). It then mixes this water with fresh incoming steam in the deaerator section (second stage).
In the first stage the water is heated to within 1.1C of steam saturation temperature and virtually all of the oxygen and free carbon dioxide are removed. This is accomplished by spraying the water through self-adjusting spray valves which are designed to produce a uniform spray film under all conditions of load and consequently a constant temperature and uniform gas removal is obtained at this point.
From the first stage the preheated water, containing minute traces of dissolved gases, flows into the second stage. This section consists of either a distributor or several assemblies of trays,
Here the water is in intimate contact with an excess of fresh gas-free steam. The steam passes into this stage and it is mixed with the preheated water. Deaeration is accomplished at all rates of flow if conditions are maintained in accordance whit design criteria. Very little steam is condensed here as the incoming water has a high temperature caused by the preheating.
The steam then rises to the first stage and carries the small traces of residual gases. In the first stage most of the steam is condensed and remaining gases pass to the vent where the non condensable gases flow to the atmosphere, A very small amount of steam is also discharged to the atmosphere which assures that the deaerating heater is adequately vented at all times.
The water which leaves the second stage falls to the storage tanks where it is stored for use. At this time the water is completely deaerated and is heated to the steam saturation temperature corresponding to the pressure within the vessel.