High Temperature Multistage Centrifugal Compressor Design Challenges

Abstract In the framework of climate change, a more environmentally sustainable approach for energy production is required; this call to action towards a zero emission and zero waste future is declined into the energy transition path. To reach this goal, Original Equipment Manufacturers (OEM) are increasingly investing in technologies to operate in segments like waste heat recovery system and power technology plant with inherent carbon capture. Centrifugal compressors already play an historical role in some of the Carbon Capture Utilization and Storage (CCUS) applications, however in recent years an increasing interest in the technologies related to CO2 Capture and CO2 Utilization segments is registered. CO2 capture segment is mainly linked to the combustion processes, which may be coupled to multiple technologies that allow to prevent CO2 emission to environment. Some examples of these methods are Hot Potassium Carbonate, which enables to chemically strip CO2 from flue gas, and oxyfuel combustion, where the CO2 is the main component of the exhaust gas. Both of these two methodologies require centrifugal compressors in their cycles, adding a new technical challenge with their higher operating temperatures compared to standard centrifugal compressors applications. In addition to this, also waste heat recovery is subjected to similar critical temperatures which may affect the compressors working in this type of processes. An example of this is the Mechanical Vapour Compression (MVC) Industrial Heat Pump technology, which requires a centrifugal compressor to increase the pressure of waste vapour. Working with higher temperatures (higher than 270°C) brings to the table new technical challenges for centrifugal compressors design, which result in new mechanical configuration features. High temperature issues are related to components temperature design limit (such as sealing systems) and thermal expansion, which is critical for clearance sizing and impellers shrink fit connection. In order to overcome these challenges, new features are presented in this paper; the proposed solutions are related to material selection and thermal barrier design, clearance optimization and usage of elastic elements, optimized impellers mechanical design and operability validation. This paper presents how these design variations are validated, taking into account the secondary flow network and performing thermomechanical analysis, leveraging methodologies from gas turbines.