Carving the way with carbon capture

This is the second half of an article by Dr S B Hegde. The first half can be found here.

Integrated carbon capture and utilisation (CCU):

In addition to CCS, cement plants can explore the concept of integrated carbon capture and utilisation (CCU). CCU involves capturing CO₂ emissions and converting them into valuable products, thereby offering economic incentives alongside emission reduction. Several CCU pathways hold potential for cement plants:

CO₂ mineralisation

CO₂ can be reacted with calcium and magnesium-rich materials, such as steel slag or waste concrete, to form stable carbonate minerals. These carbonated minerals can be utilised as supplementary cementitious materials, providing a dual benefit of carbon sequestration and improved cement properties.

CO₂ in concrete curing

CO₂ can be injected into concrete mixtures during curing to promote faster and more efficient carbonation, leading to the carbonation of calcium hydroxide to form calcium carbonate. This process consumes CO₂ and enhances the strength and durability of concrete.

Carbonation for aggregates production

CO₂ can be utilised in the production of aggregates by carbonating industrial waste materials, such as steel slag or fly ash, to enhance their properties and reduce their environmental impact.

Safety and regulatory considerations

The successful integration of CCS technologies in cement plants requires meticulous attention to safety and regulatory considerations. The storage of captured CO₂ in geological formations necessitates stringent risk assessments to prevent any potential leaks or hazards. Adherence to local, national, and international regulatory frameworks and best practices is essential to ensure the safe and responsible operation of CCS facilities.

Financial and policy support

The implementation of CCS technologies in cement plants often entails significant upfront capital investments. To encourage widespread adoption, financial incentives, subsidies, and supportive policies from governments and international organisations can play a crucial role. Carbon pricing mechanisms and emission reduction targets can incentivise cement producers to invest in CCS and promote sustainable practices.

Collaborative research and development

Advancing carbon CCS technologies for cement plants requires collaborative research and development efforts involving academia, industry, and government agencies. Investment in research and technology development can lead to innovations, cost reductions, and improved efficiency of CCS systems, making them more accessible to cement manufacturers worldwide.

Most suitable process for the cement industry

Considering the nature of cement production and the existing infrastructure, oxy-fuel combustion is often considered one of the more suitable processes for carbon capture in the cement industry.

Oxy-fuel combustion

In oxy-fuel combustion, pure oxygen is used instead of air during the cement kiln combustion process. This results in a flue gas stream consisting primarily of CO₂ and water vapour, making it easier to capture CO₂ without the need for extensive separation from nitrogen.

• Compatibility with existing infrastructure: Oxy-fuel combustion can be relatively straightforward to implement in existing cement plants with some modifications to the combustion process. It allows for a gradual transition to a low-carbon process without requiring a complete overhaul of the plant.
• High CO₂ concentration: The flue gas from oxy-fuel combustion has a high CO₂ concentration, making the subsequent carbon capture more efficient and cost-effective.
• Reduction of NOx emissions: Oxy-fuel combustion can also lead to a reduction in nitrogen oxides (NOx) emissions, which are a common environmental concern in cement production.
• Experience in other industries: Oxy-fuel combustion has been successfully demonstrated in other industries, such as power generation, providing valuable insights and learnings for its implementation in the cement sector.

Challenges

• Oxygen supply: Providing a reliable and cost-effective source of pure oxygen can be a challenge, and it requires additional infrastructure for oxygen production and supply.
• Energy requirements: Oxy-fuel combustion can consume more energy than conventional combustion processes, which may impact overall energy efficiency.

Conclusion

The integration of suitable and feasible CCS processes in cement plants offers a promising pathway to mitigate greenhouse gas emissions and align the cement industry with global climate goals. Each CCS technology presents unique opportunities and challenges, and the choice of the most suitable approach should consider factors such as plant-specific infrastructure, available resources, and local regulations.

As governments, industries, and society collectively prioritise environmental sustainability, the cement sector’s commitment to adopting CCS technologies will play a pivotal role in shaping a more sustainable future. By actively embracing and investing in these innovative solutions, cement manufacturers can take significant strides towards reducing their carbon footprint and driving the transition towards a low-carbon and environmentally responsible cement production industry.

While oxy-fuel combustion is considered one of the more suitable carbon capturing technologies for the cement industry, it is essential to conduct a comprehensive feasibility study at the individual cement plant level. Other carbon capturing technologies, such as post-combustion capture and pre-combustion capture, may also be viable depending on specific site conditions and economic considerations. Each technology has its advantages, and the optimal choice will depend on the cement plant’s unique circumstances and long-term sustainability goals.

Ultimately, successful implementation of any carbon capturing technology in the cement industry requires careful evaluation, collaboration with experts and stakeholders, and ongoing support from governments and industry leaders to achieve the desired carbon reduction targets.

About the author

Dr S B Hegde is a seasoned and accomplished cement industry professional with over three decades of experience, both in India and internationally.

Currently, he holds the position of professor at Jain University, India and also serves as a visiting professor at Pennsylvania State University in the US.

With a proven track record of leadership positions in reputed major and multinational cement companies, he is a recipient of the prestigious ‘Global Visionary’ award for his contributions to the Cement field.

Read the article online at: https://www.worldcement.com/indian-subcontinent/09112023/carving-the-way-with-carbon-capture/