Discussion on centrifugal compressors for large-scale air separation
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As the title suggests, it refers to compressors used in large-scale air separation units: 1 axial flow + centrifugal type, 2 isothermal type + gear-driven. The goal is undoubtedly to ensure stable operation of the unit and high efficiency. Everyone should be aware of the methods to improve compressor efficiency. But while focusing on certain aspects to boost efficiency, do we also overlook some losses or disadvantages arising from other factors? ...Please join the discussion!
The isothermal method + gear assembly is used quite frequently!
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Are there any pictures of these two? ? ? ? There isn’t enough text. . . . . . . . . . . . . . . . . . . . .
In actual operation, there isn’t much need to adjust the unit, nor are there many ways to do so; adjustments and optimizations are mainly made from a process perspective. The equipment is designed to serve the manufacturing process, but it is indeed necessary to achieve a perfect integration of both the equipment and the process on a subjective level. The fundamental principles remain unchanged: first, the equipment must operate stably over long periods of time; second, it must be able to operate at high loads and full capacity for extended periods. Only on this basis can we determine which parameters in the process need further adjustment or optimization, as well as which aspects can be improved, with the ultimate goal of achieving stable, high-performance operation over long periods at full capacity. Regarding a specific piece of equipment, I think it is achieved mainly through ensuring its stable and safe operation; by adjusting process parameters, unnecessary power losses are minimized. For example, it is necessary to control the pressure difference across the inlet filters properly and maintain efficient inter-stage isothermal cooling. This requires taking into account factors such as the cooling effect of the circulating cooling water, the production load of the air separation unit, and the power consumption of the equipment, in order to ensure that there is no internal leakage in the anti-surge valves and that the bearings are properly lubricated. As for other aspects, if the equipment is driven by turbines, there are many more considerations to be addressed. Lastly, I hope that the temperature remains low during working hours. There are many more; I look forward to seeing more experts provide detailed explanations, so that I can benefit from them as well.
Are axial flow compressors used in large air separation units? In China, centrifugal isothermal compressors are generally employed. What are the advantages and disadvantages of axial flow compressors compared to centrifugal compressors?
Haven’t you figured out his username yet? It’s the one who provides air separation compressors.
Axial flow + centrifugal seems to be the trend for high flow rates in the future; both MAN and SIEMENS follow this approach. Isotherm is limited by the primary impeller diameter/material, while flow rate is limited. Domestic air separation equipment should be designed for low flow rates only.
Axial flow compressors are suitable for high flow rates, while centrifugal compressors are suitable for low flow rates. Man and Siemens have cleverly combined the advantages of both to create hybrid compressors. Domestically, Shengyu and Shaanxi Gas Turbine can also do it, though with slightly lower efficiency.
It is precisely the respective characteristics of axial and centrifugal compressors that determine whether centrifugal compressors are suitable for applications with a capacity of less than 80,000 cubic meters per hour; for larger capacities, the impellers of centrifugal compressors become too large, exceeding the manufacturing capabilities available. Therefore, for large-scale air separation systems, an axial + centrifugal combination is used.
Our centrifugal impeller is 1500mm in diameter, and the motor has a power of 6700KW.