Effect of Chemical Impurities on Centrifugal Machine Performance: Implications for Compressor Sizing In A CO2 Transport Pipeline

Abstract

Several research studies have been published on CO2 pipeline transportation. Most of them focus on developing hydraulic models of entire CO2 pipeline networks. From these studies, a lot of original knowledge has been produced to understand the behaviour of CO2 pipeline networks under dense phase or supercritical conditions. The globalized modelling approach used in these studies are generally sufficient for carrying out an overall design and operation of an entire CO2 pipeline network. However, such models are too insufficiently detailed for use in optimizing the performance of a compressor in a CO2 transport pipeline. This is because in hydraulic models, compression is simulated with adiabatic or polytropic equations which do not account for the geometry and internal fluid flow processes within the compressor. Moreover, in energy requirement calculations involving these equations, compressor efficiency is assumed to be fixed, where as in reality, it varies with change in the purity of the CO2 stream being compressed. Given that compressors consume most of the energy needed to operate an entire CO2 pipeline network, it is vital that a detailed analysis of the effect of impurities on machine performance is done as a prerequisite for developing an optimal procedure for compressor sizing and selection. To this end, a quasi-dimensional model based on the laws of conservation was developed and validated for a detailed investigation of the effect of various impurities on the performance of a centrifugal machine handling supercritical carbon dioxide. Results of the study confirm that the power requirement of a compressor is affected by the impurities and provides an insight into the relationship between compressor size, work input and the pressure required to maintain the CO2 stream flowing in a transport pipeline network in supercritical state.