Process Engineering Perspectives on CO2 Capture Technology Development

This paper provides a broad overview of CO2 capture technologies from the perspective of the process engineer who is challenged to develop, evaluate, and scale these technologies up from laboratory, bench, and pilot-scale to full-scale, commercial applications. The CO2 capture problem is stated in process engineering terms, and implications of the source characteristics including composition, temperature, pressure, flow, and the variability of these characteristics - and corresponding CO2 purity/delivery specifications for various end users - are analyzed. The process engineer's tasks are described in terms of the wide range of process engineering activities that are involved, ranging from experimental data collection and process simulation, process and equipment design, and economic analyses, along with the challenges that each task presents. The nature and importance of the universal thermodynamic constraints and resulting minimum energy requirements that govern all CO2 capture process are described, and the need to integrate the CO2 capture process with the CO2 source process and CO2 use or storage locations is explored. CO2 capture technologies are categorized and compared in terms of the key process design parameters that affect each group of processes in a different way, revealing the various process advantages and disadvantages of the different approaches. Capture approaches that are discussed include chemical and physical absorption, chemical and physical adsorption along with temperature, pressure, and vacuum regeneration approaches, organic and inorganic membranes, cryogenic separation, as well as emerging approaches including chemical looping, electrochemical, and microbial capture technologies. Equipment challenges such as the physical size of mass and heat transfer devices, mechanical limitations on compression technology, and materials of construction issues are described. Conventional methods of estimating and comparing capital and operating costs among CO2 capture technologies are reviewed.