What impact do changes in the composition of process gas have on compressors?
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What impact do changes in the composition of process gas have on compressors? During the operation of a 300,000-ton methanol plant in China, the hydrogen-to-carbon ratio of the fresh gas was 1.93, while the hydrogen-to-carbon ratio of the gas entering the reactor was 3.1. There is a request to increase the hydrogen-to-carbon ratio in order to prevent the formation of fusel oils; the manufacturer responded that there is a problem with the compressor’s thrust bearing, and that increasing the hydrogen-to-carbon ratio would result in an overload that the compressor cannot handle.
Increasing the hydrogen-to-carbon ratio reduces the molecular weight of the synthesized fresh gas; to maintain the same compression ratio, a higher compressor speed is required, which indeed places greater stress on the thrust bearings. If there are problems with the thrust bearings, it is not feasible to proceed. However, in production you can try increasing the compressor’s speed and see how the temperature of the thrust bearings changes
Hydrogen-to-carbon ratio, density of the indirect reaction gas, gas density range for compressor design, compression ratio. These data are kept secret from process engineers, as they are core confidential information. It is also normal for the compressor to shut down due to vibration.
The hydrogen-to-carbon ratio affects the average molecular weight of the syngas. With a low hydrogen-to-carbon ratio, the average molecular weight of the syngas increases (resulting in a higher density of the gas per unit volume), which leads to an increase in the mass flow rate in the compression stages of the compressor. If the compressor speed remains constant, the turbine must perform more work to compress and circulate the syngas; this results in increased load on the turbine, higher consumption of power steam, and greater axial thrust on the turbine. Naturally, this places higher demands on the thrust bearings.