Analysis of Common Corrosion Types in Hydrogen Production Equipment and Protective Measures

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This post was last edited by Aggregated Cat_IEB8P on 2020-6-30 at 10:14. Analysis of the causes of high-temperature hydrogen corrosion: High-temperature hydrogen corrosion occurs in two forms – internal decarburization and surface decarburization. Internal decarburization usually occurs under the combined effect of lower temperatures and high hydrogen partial pressures ； Surface decarburization usually occurs under the combined effect of high temperature and low hydrogen partial pressure. Hydrogen corrosion occurs when hydrogen, which diffuses into steel under high temperature and pressure, reacts chemically with unstable carbides to form methane bubbles. These bubbles accumulate in intergranular voids and non-metallic inclusions, leading to a decrease in the strength, ductility, and toughness of the steel, as well as intergranular fracture. Factors affecting high-temperature hydrogen corrosion include operating temperature, hydrogen partial pressure, the stability of carbides, the segregation of alloying elements, and stress conditions. Protection measures: High-temperature hydrogen corrosion in hydrogen production plants using the steam reforming process mainly occurs between the reformer outlet and the feedwater heat exchanger of the medium-pressure shift gas boiler. Since high-temperature hydrogen corrosion is a concern at temperatures above 220°C, materials such as 20# steel and 15CrMo are commonly used in this section. Analysis of the causes of flue gas dew point corrosion: The main reason for this corrosion reaction is that the capacity to remove sulfur from the gas is insufficient; as a result, the sulfur content in the gas increases, the dew point of the flue gas rises, and the flue ducts end up below this dew point, leading to flue gas dew point corrosion. When sulfur-containing fuels burn, the sulfur compounds decompose and oxidize to form SO2 gas; part of this SO2 is converted into sulfur trioxide, which then reacts with water vapor to produce sulfuric acid. The dew point of flue gas containing sulfuric acid vapor rises significantly; when the wall temperature of the heating surface is below this dew point, the sulfuric acid-containing vapor condenses on the heating surface to form a sulfuric acid-containing liquid, causing severe corrosion to the heating surface. Protective measures: Reduce the generation of SO2. To completely resolve the problem of sulfuric acid dew point corrosion, use fuel with a sulfur content of less than 0.5%, or employ desulfurized low-sulfur fuel. Flue gas is emitted at high temperatures. It is recommended to increase the flue gas temperature of the furnace to 180°C. 3) Temperature control target for the air preheater: Ensure that the inlet temperature of the combustion air is >80°C. Materials resistant to sulfuric acid dew point corrosion should be used. Analysis of the causes of high-temperature creep corrosion in converter tubes: Initially, about 1/3 of the inner side of the tube wall reached the \"creep acceleration phase,\" resulting in the formation of voids; these voids generally formed at the boundary between the carbides and the matrix ； As creep progresses further, voids increase and connect with carbides to form microcracks ； Tiny cracks first spread inward before moving outward; under the combined effect of thermal stress and pressure inside the furnace tube, the tube eventually cracks and breaks. Protective measures include operating the furnace smoothly and conducting regular inspections of the wall temperature of the furnace tube. Control the temperature of the converter tubes