Questions about the convection section of hydrogen production converters?
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The flue gas temperature in the convection section of the converter is controlled, based on empirical rules, to be above 175°C in order to prevent dew point corrosion as well as corrosion caused by sulfuric acid formed from water, sulfur, sulfur dioxide, and sulfur trioxide. Is there then oxygen-induced corrosion in the flue gas? Is the water produced by the reaction always acidic? No oxygen? Seeking answers from fellow netizens? ?
Theoretically, the gas composition in the convection section of the converter is determined by the components of the fuel natural gas; generally, natural gas contains trace amounts of sulfur； It has extremely low corrosivity to devices.
We use dry gas as fuel, which has a relatively high sulfur content
During the initial design, a service life of several years was planned; in theory, this was taken into consideration, and a temporary solution is to increase the excess oxygen content.
In my opinion, flue gas is generated as a result of the combustion of natural gas and air. During this combustion process, an excess of air is ensured, so the flue gas necessarily contains some excess oxygen from the combustion process. Therefore, oxygen corrosion does occur; however, compared to sulfur corrosion, it is considered a less significant form of corrosion. To prevent dew point corrosion, in addition to controlling the exhaust gas temperature during operation, appropriate measures must also be taken inside the chimney to slow down the rate of corrosion and extend the service life of the equipment.
Well, relatively speaking, corrosion does occur as well, only to a lesser extent!
Increasing the excess coefficient results in a not very high oxygen content, and the thermal efficiency will also be low!
Keeping it around 3.0 to 5.0 is sufficient; higher values do affect thermal efficiency； But was dry gas used in the fuel design of your equipment? If dry gas was used from the beginning, then check the design documents; if the fuel was modified by yourself, then it’s necessary to increase the excess air volume to reduce corrosion.