Analysis of internal leakage in the bottom reboiler of the catalytic unit
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The bottom reboiler of the catalytic unit analysis tower often leaks internally, with all the leaking tube banks located at the bottom. It is preliminarily judged to be wet hydrogen sulfide corrosion, but since there is no sample analysis from the bottom of the stripping tower, can it be determined based on the sulfur content in liquid hydrocarbons and stable steam? The hydrogen sulfide content in liquid hydrocarbons is 0.5%, and the total sulfur content in the stabilized steam is 170 mg/kg. Can this concentration lead to wet hydrogen sulfide corrosion?
In a reboiler, the areas most prone to corrosion are generally at the gas-liquid interface, where the two phases coexist, creating a more severe corrosive environment.
However, at present, the reboiler has experienced multiple internal leaks, all of which occurred in the lower tube bank
In addition to considering the sulfur form, it is recommended to assess whether the presence of free water is possible. Alternatively, try dehydration at the low point of the reboiler to determine whether there is free water present. Wet hydrogen sulfide corrosion is accelerated by the presence of water; furthermore, consider the possibility of repeated internal leaks in the heat exchanger, and think about upgrading the material used.
A wet H2S corrosion environment is defined as one in which the medium in contact with the container contains free water in the liquid phase, and one of the following conditions is met: (1) The concentration of H2S dissolved in the free water is greater than 50 mg/L； (2) The pH value of free water is less than 4.0, and it contains H2S ； (3) The pH of free water is >7.6, and the water contains 20 ppm of dissolved hydrogen cyanide (HCN) as well as some dissolved H2S. (4) The partial pressure of H2S in the gas phase (absolute pressure) is greater than 0.3 kPa.