Decarbonisation Technology - February 2023

Innovative technological paths for carbon dioxide capture

A review of advances in carbon capture technologies. Continuous improvement of existing processes for efficient removal of CO 2 from flue gases is essential

Himmat Singh Formerly Scientist ‘G’ CSIR-Indian Institute of Petroleum

T here is a clear scientific consensus major cause of global warming. In a country such as India, transportation and electricity generation contribute to 45% of the country’s total greenhouse gas emissions (Ashkanani, et al ., 2020). While the primary goal must be to reduce the world’s reliance on fossil fuels, by switching to renewable energy sources (RES), a secondary goal is to capture emissions from processes fuelled by hydrocarbons. For this reason, the technological paths of carbon capture and sequestration/storage (CCS) from power plants and other industrial plants are the subject of intensive investigations. While extensive literature reviews on CO2 capture processes exist (Boot-Handford, et al., 2014), (Bui, et al., 2018), (Global CCS Institute, 2018), Table 1 provides an overview of the three main categories for CO2 capturing processes: pre-, post- and oxy-fuel combustion. In terms of the technology used for separation, CO2 scrubbing via liquid solvents (chemical or physical) is a mature process that builds upon several commercial solutions employed in hundreds of plants (Cuellar-Franca and Azapagic, 2014). A fourth category is direct air capture (DAC), which has been demonstrated at a commercial that emissions of carbon dioxide (CO2 ) and other greenhouse gases are the scale by companies such as Climeworks and Global Thermostat. Challenges include integrating current and future technologies with renewable sources of electricity, heat, and the need for significant cost reductions (Norskov, Latimer and Dickens, 2019).

The commercial benchmark technology for carbon capture from point sources is liquid scrubbing, which uses amine mixture to absorb CO2. It is commercially available from several companies and has been applied at scale with no major challenges (Norskov, Latimer and Dickens, 2019). Recent research efforts have been directed towards improving existing technologies and developing innovative technological paths to improve CO2 capturing/trapping efficiency, resulting in lower process costs and improved process safety to facilitate environmental verification. This article summarises the current state of the art for conventional solvents and the most recent innovative investigations (second- and third-generation technologies) in this field as applicable to carbon capture from point sources (Norskov, Latimer and Dickens, 2019). CO 2 capture: innovative research paths Since 2000 the chemical industry has invested in the development of new processes that are less energy-intensive, have higher efficiency, and are more environmentally acceptable. New methods and techniques are being developed for pre-combustion, post-combustion, and oxy-fuel combustion. Dedicated research programmes, mainly in the US and Europe, have set ambitious targets to achieve a carbon capture cost approaching $20/t (Lockwood, 2017). Novel solvents with phase change systems, ionic liquids, and other non-aqueous solvents aim to achieve lower regeneration energy requirements than conventional amines. Ionic liquids (ILs) are most promising as they