Practical experience in post-combustion CO2 capture using reactive solvents in large pilot and demonstration plants

Significant progress on post combustion carbon dioxide (CO2) capture technology using reactive solvents has been reported since the IPCC report of 2005. This has included both the advances in the fundamental knowledge of the technology and practical experience in pilot, demonstration and commercial plants. This second paper looks specifically at the latter aspect. There has been a widespread deployment of pilot and demonstration plants as well as the birth of a commercial size CO2 capture plant. The research and development work being carried out in pilot and demonstration plants have enabled the use of real conditions to study the CO2 capture process and to provide realistic guidance in the design of commercial plants. The lessons learned from the pilot and demonstration plants have been very varied but have contributed to the continuous improvement of the amine-based CO2 capture technology in terms of off gas emissions, operational issues, solvent management, corrosion, plant size reduction, new and blended amine solvents, and non-amine based solvents. Some of these issues have been resolved through the development and use/experimentation of corrosion inhibitors, degradation inhibitors, non corrosive materials as construction materials, and non thermal reclaiming methods, as well as the application of operating conditions that are compatible with the solvent system used. Since the solvent-based CO2 capture technology constitutes a relatively new industry, measurement standards involving sampling and analysis of the off-gas, and analysis of the solvent system in use were not in place prior to the IPCC 2005 report. Therefore, the emergence of the demonstration plants has thrown light on both the need for these standards and what are currently in place. Specifically, sampling techniques are being introduced which aim to reliably obtain representative samples from the off-gas of an amine based CO2 capture plant. Techniques are also being developed to analyze the current complex amine solvent system itself. Progress has also been seen on the reporting of the heat duty for solvent regeneration, especially for smaller pilot plants. Bigger demonstration plants have been hesitant to share results on heat duty. However, reports from small pilot plants show that heat duty improvements have been achieved based on two approaches: namely, development of energy efficient solvents and process optimization. Based on these two approaches, the heat duty has been brought down from about 5.0-1.8 GJ/ton CO2 produced. On this issue, it has been noticed that even though the solvent used in conjunction with the process optimization method employed are capable of providing an acceptable heat duty (i.e., close to 1.8 GJ/ton CO2 produced), the actual heat duty obtained in pilot and demonstration plants, in most cases, is higher than design specifications. Catalysis in amine-based post combustion CO2 capture has become a new trend which may possibly pave the future direction for solvent-based post combustion CO2 capture. Solid mineral catalysts are used in one approach, whereas a biocatalyst is employed in another approach. Both approaches are expected to see extensive research and development work all the way to demonstration plants in order to perfect the respective processes, and to generate reliable data for design of a commercial plant. Thus, future trends could see significantly smaller vessels and heat duties for post-combustion CO2 capture from combustion flue gases using reactive solvents. These would result in significantly lowering the cost for post-combustion CO2 capture. More activity at pilot plant and large demonstration scale plants on the use of amino acid salts and chilled ammonia process have been coming up (CAP), which may help to enhance the performance of these alternative post combustion capture processes. (C) 2015 Elsevier Ltd. All rights reserved.