Scaling on the first-stage impeller of the 2-in-1 compressor? Everyone, take a look at what’s going on!

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Brief description of the equipment: Our company is engaged in methanol synthesis, using low-pressure synthesis methods with coal as the raw material. The raw gas at 2.00 MPa enters a compressor where its pressure is increased to 5.5 MPa. After being cooled to 100°C, it is then cooled further to 45°C before entering the circulation section, where its pressure is raised again to 5.5 MPa and its temperature adjusted to 48°C. Subsequently, it passes through a heat exchanger for heat exchange, after which it enters the synthesis tower. This tower is of the tubular type and uses C307 copper-based catalysts. After the reaction, the gas undergoes two stages of cooling before entering the alcohol separation unit, where crude alcohol is separated out. The remaining gas goes into an alcohol washing tower, where it is absorbed using deionized water; the leftover gas then returns to the circulation system. The compressor is driven by an electric motor and operates on a 9-stage, single-circulation centrifugal principle. The composition of the incoming gas is as follows: H2: 68%, CO: 20%, CO2: 10%. The reaction temperature is around 210°C. The compressor has been in operation for over two years. Scaling issue: Scaling mainly occurs on the first stage impeller at the compressor inlet as well as in the inlet chamber; there is a significant amount of pale yellow scaling, which severely blocks the inlet, causing overpressure during production. No scaling is present on the other impellers. This scaling does not dissolve in water but can be dissolved in hydrochloric acid. It appears pale yellow, and crystal-like substances can be seen. I would appreciate it if colleagues could help analyze how this scaling forms. Thank you.