The consensus that global CO2 emissions must be controlled to prevent a catastrophic change to the climate has dominated a significant proportion of global research and technology development.
The IPPC Synthesis Report on climate change (2014) calls for urgent action to minimise an increase in global temperatures to prevent irreversible harm to the planet’s ecosystem and its inhabitants. The more recent IPPC Special Report (Global Warming of 1.50C) places specific culpability on human actions. Whilst economical technologies have emerged for power generation, and to a certain extent transport and heating, cost competitive solutions to industrial CO2 emissions continue to elude these businesses. As demand for steel is expected to rise with growing populations, quality of life and new low-carbon infrastructure, this carbon intensive manufacturing process must be addressed. Globally, the steel industry accounts for 4.3Gton, about 8% of anthropogenic CO2 emissions. To reach the Paris Agreement of a maximum 20C increase in global temperature, we must find viable, cost-effective solutions to lower not only domestic but global steel industry emissions. Steel is a globally traded commodity and CO2 is not patriotic.
At present, there is no cost-effective method for significant decarbonisation of the steelmaking process. The following thesis documents this journey of research, identifying gaps within the field of knowledge and producing three world-firsts. It focuses upon two propriety technologies (CO2 plasma dissociation and microbubbles) and places these into the context of an integrated steel plant, along with a complimentary, detailed techno-economic strategic model.
Through experiential design and testing, we find that the integration of microbubbles to the CO2-NH3-H2O system can lead to rapidly improved kinetics, achieving high CO2 loadings within a remarkable 8 minutes. This discovery would be directly applicable to low-energy aqueous ammonia carbon capture systems, whereby reaction kinetics are a limiting factor on commercial deployment, cost and scale.
Current CO2 plasma chemistry devices are unable to achieve both high conversion and high efficiency simultaneously. A new reactor design has been invented, which compliments the two stages of CO2 dissociation in two plasma regions that operate within a single reactor. It was proven that a single rector can operate with two distinct plasma regions, a primary region with a high-power input to initiate the reaction and a subsequent low-power region to continue the reaction, without compounding energy losses. This resulted in a 40% increase in efficiency.
A first-of-a-kind, detailed techno-economic model for the transition to a future low-carbon steel production system has been developed, to compliment the analysis of the two low-carbon technologies and to understand their deployment in a future steel plant scenario. Simulation of multiple scenarios has been conducted on a year-by-year assessment to demonstrate if cost-effective low-carbon steel production will be possible prior to 2050.
Following the detailed assessment of potential future steelmaking operations, we find that the application of CO2 micro-plasma dissociation may have a limited role within a future steel making operation for deep (>80%) decarbonisation. Nevertheless, we have shown that a revolutionary new multi-staged plasma invention has superior benefits over the current plasma reactors as it is more aligned to the CO2 dissociation mechanisms, and that the first application of microbubbles to an aqueous ammonia capture system is highly applicable to steel plant decarbonisation and could yield annual saving in excess of £68m.
The techno-economic simulation has shown, for the first time within literature, that acting quickly with currently available technologies will critically have an equal, if not greater, effect on the cumulative carbon emissions to atmosphere, in contrast to waiting for the ‘ideal solution’, which maybe at a lower technology readiness level or currently uneconomical. If hydrogen is to be used as the steelmaking technology of the future, greater emphasis must be taken into accelerating the deployment of this technology, in particular making sufficient, affordable zero-carbon hydrogen available.
