Design, dynamic modeling, and control of a multistage CO2 compression system

Abstract

This paper presents a comprehensive model of a post-combustion CO 2 compression system that uses a multistage centrifugal compressor train to take the CO 2-rich gas from the regenerator of a CO 2 capture system and compress it to the supercritical conditions required for pipeline transport. The compression system model includes inter-stage coolers, flash vessels, glycol tower for water removal, and the CO 2 inventory of the associated system. Both inline and integral gear compressors are designed using dimensionless numbers and appropriate design constraints. The steady-state integral gear compressor model is validated against industrial compressor performance data provided by a commercial CO 2 compressor manufacturer. Its performance is also compared to the performance of an inline compressor model using a typical feed stream from a post-combustion CO 2 capture process. Performance curves using dimensionless exit flow coefficient and isentropic head coefficient are used for simulating off-design performance of the integral gear compressor. To avoid surge during operation, a controller has been designed. Transients of key process variables in response to various disturbances have been studied.

Operating flexibility of natural gas combined cycle power plant integrated with post-combustion capture

“…An 8 stage variable speed integrally geared compressor system design has been chosen due to relatively high part-load efficiencies (Liebenthal and Kather 2011, Modekurti et al 2017, Bovon and Habel 2007, and due to the wide operating range advantageous for solvent storage and delayed regeneration. There are several different compression strategies that could be used as detailed in González-Díaz et al (2017) and Vermeulen (2011).…”

“…The part load performance of the variable speed integrally geared compressor system is modelled according to the methodology described in Modekurti et al (2017) and Liese and Zitney (2017). In the absence of directly available and reliable CO 2 compressor performance maps in the publically accessible literature, it is a sufficiently accurate method of assessing the off design behaviour of the compression unit.…”

“…An eight stage integrally geared compressor design was chosen following the methodology outlined in Modekurti et al (2017) and Liese and Zitney (2017). It is worth noting that with eight stages of compression instead of the six stages frequently considered in the CCS literature, the tip speed of the impellers reduces to Mach numbers below 1.…”

Step by Step Derivation of the Optimum Multistage Compression Ratio and an Application Case

“…The isentropic efficiency of the n stages of a compression might not be equal. Apart from the evolution of the thermodynamic properties of the gas from stage to stage, engineering requirements at each stage may impose limitations, so that the maximum theoretical efficiency cannot be reached; for example, in [ 15 ], designing a multistage compression of CO with centrifugal compressors, the maximum stress of the impeller is identified as the limiting condition for the impeller tip speed.…”

“…Logically, this will show that each stage will be operating with a different isentropic efficiency. Sometimes engineering constraints do not allow for reaching the intended compression ratio at a certain stage [ 15 ].…”