Compressor coking and operating cycle issues
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Everyone: The dry gas compressors in our dehydrogenation units are experiencing serious coking problems after operating for a while. Last year, major repairs were required every 20 days; the composition of the cleaning oil was adjusted, and things improved for about a year. Now this problem has arisen again – the pistons and valves are coking and becoming blocked. Initially, the temperature of the exhaust valve was extremely high; currently the temperature is not as high, but efficiency has decreased. Those with similar experience – how did you make adjustments? Please share your insights so we can solve this problem together. Take a look at the pictures. Those with experience in dehydrogenation processes – have you analyzed the components that cause coking? How to avoid it and ensure long-term operation
1. Coking is mainly caused by heavy components such as tar and naphthalene; I’m not sure what heavy components are present in the dry gas, so a purification device should be installed before it enters the compressor. 2. When designing the compressor, the exhaust temperature should be kept under control; for example, by using an additional compressor stage, the theoretical exhaust temperature can be maintained at around 110°C or lower. While the initial investment may be higher, it will result in significant savings in the long run. 3. What can be done now is to install a purification device at the inlet, or reduce the exhaust temperature (by increasing the inlet pressure or reducing the outlet pressure, or lowering the inlet temperature), and then observe the operating conditions before conducting further analysis.
It’s already great that it’s been a year; just keep going.
In my opinion, it’s basically due to high temperatures or heavy material components; in such cases, it’s possible to lower the temperature slightly or passivate the surface of the piston.
There’s no good way to lower the exhaust temperature.