Regarding the issue of non-condensable gases in boilers and heat exchangers

1. If a deaerator is not used, even when desalinated water obtained through two-stage reverse osmosis is used as boiler feedwater, a certain amount of dissolved oxygen will still be present in that desalinated water. This dissolved oxygen accelerates the corrosion of the metal materials inside the boiler under high-temperature and high-pressure conditions, especially affecting the steel components of the boiler. This type of corrosion typically manifests as pitting and cratering, and over time it can severely affect the service life and safety of boilers. 2. Regarding the dissolved air in demineralized water, if deoxygenation is not carried out, this air enters the steam system along with the steam; at high temperatures, the oxygen present in this dissolved air can continue to accelerate corrosion of metals within the system. The resulting non-condensable gases (mainly nitrogen) may, during the use of steam in devices such as heat exchangers, cause gas blockages due to their difficulty in condensing, which affects the heat exchange efficiency and leads to a reduced heat transfer performance. Therefore, proper deoxygenation treatment is essential to ensure the efficiency of the entire steam system and extend the service life of the equipment. .

I. If a 10-ton gas boiler uses desalinated water produced by two-stage reverse osmosis as its boiler feedwater, what will be the consequences of not using an oxygen remover? Will the boiler corrosion be severe? Consequence analysis: Boiler corrosion: Although most salts are removed from the desalinated water, it still contains a certain amount of dissolved oxygen. If the deaerator is not used, dissolved oxygen will react with the metal components in the high-temperature and high-pressure environment of the boiler, leading to corrosion of the boiler. This type of corrosion not only reduces the service life of the boiler but may also pose safety hazards. For a 10-ton gas boiler, the severity of corrosion depends on the level of dissolved oxygen, the operating conditions of the boiler, and the corrosion resistance of the metal material. If the dissolved oxygen level is high or the boiler operates under harsh conditions, corrosion can be very severe. Decline in steam quality: The presence of dissolved oxygen also affects the quality of steam. When steam contains a high level of dissolved oxygen, it reacts with other substances in subsequent processes to form substances that are insoluble in water, thereby affecting the purity of the steam and its thermal efficiency. Underscale corrosion: Dissolved oxygen can also cause iron oxide scale to form on the inner walls of boilers. This scale not only has poor thermal conductivity, causing the water wall tubes to overheat and get damaged due to inadequate cooling, but it also leads to corrosion beneath the scale, accelerating the damage to those tubes. II. If deoxygenation is not carried out, will the dissolved air in the demineralized water form non-condensable gases in the steam, thereby affecting heat exchange in the heat exchangers used in subsequent processes? Analysis: Formation of non-condensable gases: The dissolved air in the deionized water (including oxygen and other gases) is released from the water during the heating process. If the deaerator is not used, these gases will enter subsequent processes along with the steam. In the heat exchanger, these gases form non-condensable gases, that is, gases which do not condense on the surface of the heat exchanger. Decreased heat transfer efficiency: The presence of non-condensable gases significantly reduces the heat transfer efficiency of the heat exchanger. This is because the non-condensable gas forms a gas film on the surface of the heat exchanger, hindering the transfer of heat from the steam to the cooling water. This will cause the temperature of the cooling water to rise, reducing the efficiency of steam condensation and thus affecting the proper operation of subsequent processes.

A boiler of 10 tons should be equipped with a deaerator; those below 10 tons do not need one