This paper is giving an overview of advanced, innovative and proven technologies for CO2 compression. This includes reciprocating and centrifugal compression - with focus on modern gear type designs for Onshore CO2 applications - in comparison with other technologies. This comparison is related to demands for upcoming Enhanced Oil Recovery (EOR), Carbon Capture & Storage (CCS), Coal Gasification (IGCC, Oxyfuel) and an outlook to offshore high pressure CO2 compression.
CO2 has a long tradition in modern industrial processes and furthermore plays an increasing role in the present discussion of the world wide climate change. Especially in refinery and food industry applications it is used and a common good since several decades. Nowadays numerous industrial procedures require CO2 not in a gaseous but in a compressed state at a specific pressure and temperature.
The use of high-speed reciprocating compressors for Sequestration (CCS) or Enhanced Oil Recovery (EOR) is the historical and traditional approach for the manufacturing of compressed CO2. Nevertheless recent investigations reveal several limits of this technology - e.g. the upper capacity of possible flow rates have strong restrictions due to the mechanical design.
For this reason centrifugal type compressor systems are now state of the art and a promising solution for future CO2 projects. Centrifugal compressors generally can be split into two major building types which distinguish by design namely single-shaft (in-line, between bearings) centrifugals and multi-shaft integral-gear centrifugals. These assembly alternatives will be compared in this paper.
MAN Diesel & Turbo has manufactured reciprocating compressors in the past and still is manufacturing both types of centrifugal technologies (single-shaft and multi-shaft type, according to API 617 as stated by MACEYKA, PICKEREL in 2007) for CO2 services. We therefore feel confident and in a position to give a sophisticated overview and comparison of all technologies.
Before we step into compression technology some explanations concerning CCS and EOR are given:
A steeply rising demand for energy world-wide, combined with increasingly strict environmental regulations have created the need for new technologies for the clean and sustainable generation of power. Carbon Capture and Storage labels a group of technologies which all have one aim: To separate carbon dioxide in the process of conventional thermal power generation.
Whether the method by which CO2 is separated is IGCC, Oxyfuel or Post-Combustion: Every one of these processes requires the compression of CO2 for transport and storage for future use. The process path can be seen in Figure 1.