Corrosion analysis of mercury in natural gas feedstock on aluminum alloy cold box materials
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Help needed: We have a cryogenic cold box with a design pressure of 2.5 MPa. The operating pressure in the feed gas channel is approximately 2.1 MPa, and the operating temperature ranges from 45°C to -75°C. For the refrigerant channel, the operating pressure is 1.8 MPa, with the same temperature range. The materials used for these channels are aluminum alloys 5052, 3003, and 5083. After about 6 months of operation, leakage occurred between the feed gas channel and the refrigerant channel. A full-component analysis of the feed gas entering the cold box revealed that it contains roughly 25 ppm of mercury, about 30 ppm of SO2, approximately 0.77% CO2, around 68.8 mg/m³ of H2S, and a water content of roughly 4459 mg/m³. Current analyses suggest that incomplete removal of SO2, CO2, H2S, and mercury is the cause of internal leakage in the cryogenic tank. Some experts have analyzed that SO2, CO2, and H2S have little impact on the cold box and can be ignored; the main reason for the problems is the severe corrosion caused by mercury in the feed gas, which leads to leaks. I would appreciate it if experts could analyze what is causing the leaks in the feed gas channels and the coolant channels of the cold box. Thank you!
It may be better to approach this issue from another perspective; this is for reference only. Corrosion is the most severe consequence; it doesn’t matter which element causes the corrosion, as it cannot be removed under the current conditions anyway. If it’s possible to eliminate a certain potential elemental factor, then do so. If it cannot be eliminated or if we currently lack the capability to do so, should we consider switching to corrosion-resistant materials to resolve the problem at its root? Continuing as per the instructions may not necessarily solve the problem. This is just a thought for reference.
I can provide you with a polyaniline coating that is durable; one layer of anti-corrosion treatment will be sufficient
Yes, it is a plate-fin heat exchanger, designed and manufactured in accordance with the NB/T47006 standard.
Corrosion prevention can help solve this issue, but the heat exchange efficiency will decrease; I’m not sure if that’s acceptable
What kind of solution is it? The inside of the device is made of corrugated plates
How thick should the anti-corrosion coating be applied? Does it affect heat transfer efficiency?
200μm is normal; it affects heat exchange efficiency
Activated carbon adsorption can be considered to remove a portion of sulfur and mercury. It is also feasible to use corrosion protection