Why must a certain amount of steam be allowed to escape from the exhaust pipe of the deaerator?

Thread Content

Typically, atmospheric thermal deaerators use steam as a heat source to heat soft water to its boiling point, thereby removing the oxygen dissolved in it. On the one hand, the molecular weight of oxygen is 32, while that of water vapor is 18; therefore, the specific gravity of oxygen is 1.78 times that of water vapor. As a result, oxygen tends to sink after being removed from water, which helps to maintain a certain amount of steam flow in the exhaust pipe, thereby facilitating the removal of oxygen from the deaerator by means of the steam. On the other hand, according to Dalton’s law, the amount of oxygen dissolved in water is proportional to the oxygen partial pressure surrounding the soft water. Maintaining a certain level of steam flow helps to reduce the oxygen partial pressure around the soft water, thus aiding in the removal of oxygen from it. Therefore, the valve on the deaerator exhaust pipe cannot be opened very slightly in order to save steam; it can only be kept at a moderate opening degree as long as the deoxygenation of the soft water meets the required standards. The specific opening degree of the valve should be determined through adjustment tests on the deaerator. Based on practical experience, the exhaust volume from the exhaust pipe is approximately 0.2% to 0.3% of the amount of soft water; in some high-efficiency deaerators, this value is even lower. Causes and measures for increased dissolved oxygen in deaerators