Assessment of postcombustion carbon capture technologies for power generation

A significant proportion of power generation stems from coal-combustion processes and accordingly represents one of the largest point sources of CO₂ emissions worldwide. Coal power plants are major assets with large infrastructure and engineering units and an operating life span of up to 50 years. Hence, any process design modification to reduce greenhouse gas emissions may require significant investment. One of the best options to utilize existing infrastructure is to retrofit the power station fleet by adding a separation process to the flue gas, a practice known as postcombustion capture (PCC). This review examines the recent PCC development and provides a summary and assessment of the state of play in this area and its potential applicability to the power generation industry. The major players including the various institutes, government, and industry consortia are identified along with flue gas PCC demonstration scale plants. Of the PCC technologies reviewed, amine-based absorption is preeminent, being both the most mature and able to be adapted immediately, to the appropriate scale, for power station flue gas with minimal technical risk. Indeed, current commercial applications serve niches in the merchant CO₂ market, while a substantial number of smaller scale test facilities are reported in the literature with actual CO₂ capture motivated demonstrations now commencing. Hybrid membrane/absorption systems, also known as membrane contactors, offer the potential for the lowest energy requirements, possibly 10% of current direct scrubbers but are at an early stage of development. Other methods being actively pursued as R&D projects include solid absorbents, solid adsorbents, gas membrane separators, and cryogenic separation. The variety and different maturities of these competing technologies make technical comparison largely subjective, but useful insights could be gained through the development and application of econometric techniques such as ‘real options’ within this context. Despite these limitations, it is clear from this review that amine scrubbing is likely to be adapted first into the existing power station fleet, while less mature technologies will grow and become integrated with the development of future power stations.