Convert the reciprocating compressor designed for natural gas to one designed for hydrogen
Thread Content
I have a question: what impact will it have on a reciprocating compressor that is originally designed to use natural gas if the working medium is changed to hydrogen? What’s the reason?
The molecular weight of natural gas is 16, while that of hydrogen is 2; the compression ratios of these gases differ； The design requirements for hydrogen compressors are higher than those for other types of compressors.
GB/T 20322-2006 Reciprocating compressors for the petroleum and natural gas industry, JB/T10909-2008 Small reciprocating piston hydrogen compressors
I won’t go into details about the outlet pressure; you can check it on site yourselves. For long-term operation, I think several issues need to be confirmed: 1. Whether the material choices for the original compressor cylinder liners and pistons are suitable for hydrogen-rich operating conditions. 2. Changing the process medium disrupts the balance of the original design. Since the mass of the piston remains unchanged and its rotation speed is also unchanged, the inertial force of the piston stays the same. A decrease in the molecular weight of the medium means that the reaction force exerted by the compressing medium decreases, thereby breaking this balance. Over time, components such as the main shaft bearings and crossheads are prone to increased wear at the dead center positions, which can even lead to accidents. If the molecular weight increases, it can still be adjusted by changing the clearance; but when the molecular weight decreases, it’s not clear what to do. 3. Regarding electrical components, it is necessary to check whether the explosion protection rating meets the requirements for hydrogen environments
As the molecular weight of the gas changes, the corresponding gas valve needs to be replaced; it is recommended to consult the manufacturer for an assessment
In reality, the outlet temperature rises to a higher level; it’s too risky to continue operating under such conditions. I just can’t understand why the temperature increase is so significant when the compression ratio remains unchanged
With the compression ratio remaining unchanged, is the temperature higher than before?
It’s a simple principle: when the K value is different, the temperature rise varies even with the same compressor ratio. The temperature of the hydrogen gas rises; therefore, in terms of performance, this manifests as a high exhaust temperature. Furthermore, there is a fundamental difference between the design of hydrogen and that of natural gas; their sealing levels are different, and so are their safety standards.
Are there any recommended materials that introduce the K values of various gases? I’d like to learn about it a bit :)