Decarbonisation of the cement production process

Thesis

Cement serves as the most consumed man-made material worldwide, with its production accounting for 8% of global anthropogenic carbon dioxide (CO₂) emissions. Clinker, constituting 95% of cement's composition, is the primary contributor to CO₂ emissions, making deep decarbonisation necessary to reduce climate change impacts. Although existing studies have tapped into fuel and calcination-oriented decarbonisation options, there is clearly a lack of a systematic comparative assessment of energy and CO₂ performances focusing on alternative fuels (carbon-neutral) and alternative clinkers (characterised by low limestone content) in distinct locations, to consistently quantify their potential. This thesis addresses the literature gap through a combination of process simulation, mathematical optimisation, geospatial analysis, along with energetic and gate-to-gate CO₂ performance assessments. In this thesis, fuel-based emissions were addressed through the use of hydrogen (H₂) and solar energy as alternatives to fossil fuel for clinker production. This was followed by the evaluation of alternative clinkers projected to reduce CO₂ emissions from limestone calcination. The findings reveal that using H₂ and solar energy as alternative energy sources enables CO₂ reductions of up to 27.6%. In contrast, both alternative fuel options demanded higher energy due to water electrolysis and operation of solar photovoltaics (PV) and concentrated solar power (CSP) systems. On the contrary, the use of alternative clinkers was able to achieve CO₂ reductions of up to 35%, and 45.5% in energy reductions. Similarly, CO₂ reductions of 45% was achieved through partial substitution of clinker with supplementary cementitious materials (SCMs) from CO₂ mineralisation. Notably, the economic analysis of the solar driven process shows that in high solar regions, costs can be ~47% lower than less favourable regions, highlighting the influence of location specific solar energy characteristics. These findings accentuate the limitation of fuel substitution alone in clinker production and underscores the need for decarbonising the calcination process from the material perspective to achieve more substantial emission reductions. The collective contribution of this thesis involves insights into the carbon abatement potential from both the material and process perspectives, demonstrating the technical feasibilities of decarbonisation options.

Authors: Williams, F

• DOI: 10.5287/ora-qz8vyrexz
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: alternative fuels; deep decarbonisation; energetic assessment; cement decarbonisation; cement production
• Subjects: Civil engineering; Chemical engineering; Materials science