How much does oxygen with heat tracing corrode the material of oxygen pipelines?
Thread Content
The oxygen temperature is required to be 100 degrees before mixing it with steam, but our facility does not have an oxygen heating device. During the winter of 2007, freezing occurred in the pipes after mixing oxygen with steam, which caused severe damage to the oxygen nozzles. During the autumn inspection in 2008, I used oxygen pipes with a DN150 diameter and made of 304 material, along with 6 pipes with a DN25 diameter and made of 10# steel, each being 70 meters long. Outside these oxygen pipelines, distilled condensate was used to heat the oxygen to 45 degrees Celsius; the temperature of the condensate itself was 130 degrees Celsius. To what extent does this kind of heating of oxygen with condensate affect the corrosion resistance of the pipe materials?
May I ask, the steam that enters the oxygen pipeline should be superheated steam at around 400 degrees – why can it freeze? Is it ice that has formed on that part of the oxygen tube? The oxygen supplied by air separation must be free of water; the freezing is probably due to steam in the oxygen pipeline condensing and forming ice in some dead-end section If the heat tracing consists of a steam pipe running alongside the oxygen pipeline, there should be no corrosion; and even if electrochemical corrosion occurs, it will be the steam pipe that corrodes first. Many processes involve feeding oxygen directly into the heating furnace to raise its temperature. However, in the process of producing methanol from coke oven gas, frequent start-up and shutdown operations certainly affect the service life of the oxygen coils, and leaks can cause significant problems. Here are my humble opinions; please give me some guidance.
Bro Li, is it necessary to add steam to the oxygen from the air, after it has been preheated, before it enters the conversion furnace?
Heating is necessary; the temperature of the gas entering the converter must be above 550 degrees. If oxygen is introduced without being heated, a large temperature difference occurs in the central tube, which causes severe damage to the material. This is especially true for oxygen pipelines that are not protected from steam. What material is used for the pipeline after the oxygen heater, 304 or 316? I think it is normal for the temperature to be controlled at 270 degrees after heating with an oxygen heater.
Adding steam is not just about heating the oxygen; rather, it is crucial for preventing backflow of coke oven gas and resulting explosions when oxygen supply is cut off. Oxygen pipes are made of 304, which is relatively corrosion-resistant.
Our company uses INCONEL600 for the oxygen-steam mixing pipes in other projects. The original poster can take a look
It is certain that the corrosion of pipelines by oxygen increases when heat tracing is used; however, at 45°C alone the impact should be minimal. But I think another corrosion issue worth the original poster’s attention is the corrosion caused by the heat tracing line on the oxygen pipeline. Pipelines made of the sample materials used for the heat tracing line and the oxygen line will work fine; otherwise, the oxygen pipeline will corrode very quickly.