A compact CO₂ capture process to combat industrial emissions

CO₂ emissions from industry occur typically from a number of small, low concentration sources with a wide range of flue gas compositions and impurity profiles. For example, in a refinery, CO₂ is emitted from many process furnaces, hydrogen production units and power generation plant, and emission points are scattered over several km2. If a centralized CCS plant is applied, a large piping network and compression power will be required. Moreover, the capture unit would need to deal with a wide range of impurities. This is not optimal. Instead, a much more efficient capture process design involves several separate and bespoke capture units at different locations on site, sharing only a common high concentration CO₂ export pipeline. It is therefore beneficial to have several compact and flexible capture units, with low operating and capital costs and high efficiency able to use waste heat from different process units.

CO₂ capture by using amine solvents is the most mature technology employed in most carbon capture plants, including the world’s first large-scale CCS plant at Boundary Dam, Canada. This technology is considered a reference for next-generation technologies. Incremental improvements through the use of alternative amines or amine mixtures with higher capacity and/or lower regeneration/degradation costs are potentially possible. However, major problems with this conventional process remain without a fundamentally different design. They include (a) low mass transfer efficiency in the absorber and desorber, resulting in large equipment size and high capital and operating costs, (b) high energy consumption in solvent regeneration, causing a very high energy penalty and operating cost, (c) corrosion caused by concentrated amine solutions, which makes it necessary to use more expensive materials, (d) thermal and oxidative degradation of amines above 100oC. More solvent make-up means high operating cost

We propose to meet this challenge by combining two technologies, rotating packed bed absorption and microwave-assisted regeneration, which will enable small and flexible capture devices to be installed at a wide range of industrial sites. A rotating packed bed column offers a dramatically reduced volume by 90% compared to a traditional absorption column, while microwave regeneration is a revolutionary method for regenerating amine solutions at 70oC (rather than 120oC) that can operate without a temperature swing and is very fast, leading to further significant reduction in capital costs (by around 50%), in the sensible heat used for CO₂ desorption, and in corrosion and solvent degradation by over 90%. CO₂ desorption at 70oC also enables the regenerator to use low grade industrial waste heat.