A compact CO2 capture process to combat industrial emissions

Industrial emissions are an important source of atmospheric CO2 that must be tackled for the UK to meet its legally binding targets. 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.

The research will benefit policymakers planning carbon capture development worldwide and industrial CO2 emitters. High capital and operational costs have been the major concerns in CO2 capture and are the principal barriers to implementation of CCS within industry. By reducing these costs the financial burden on industry and financial companies is also reduced (compared to other carbon capture methods), which benefits consumers as well.

Academic and industrial workers in the area of CO2 capture will benefit from the developed novel technique for CO2 capture.

Academic and industrial workers in the area of microwave heating will benefit from reference data of the dielectric heating behaviour of solvents, and from the insight gained into microwave interactions with solvents at the molecular level.

This technique could potentially benefit academic and industrial workers in many other gas separation processes, e.g. the separation of higher pressure H2/CO2 mixtures for pre-combustion carbon capture via IGCC power plants.

The CCS community will benefit from the personnel trained during this project.

The research will also feed into investigators' teaching in chemical and mechanical engineering at the University of Edinburgh, the University Hull and the University of Newcastle, and for all staff members through short UG research projects.

The experimental rigs developed for this project will continue to be used for future undergraduate and postgraduate research projects at these universities