By Nidhi DhullReviewed by Susha Cheriyedath, M.Sc.Oct 21 2024A recent article published in Engineering Proceedings proposed a framework integrating Shannon’s entropy and multi-criteria decision-making (MCDM) approaches to drive the cement sector toward net-zero emissions and sustainability. Four MCDM methods were employed to rank different energy efficiency alternatives for cement production.
Study: From Grinding to Green Energy: Pursuit of Net-Zero Emissions in Cement Production. Image Credit: Bilanol/Shutterstock.com
Background
The energy-intensive cement industry accounts for approximately 12-15% of all industrial energy usage. Cement production comprises combining iron ore, alumina, limestone, silica, and trace elements and heat treating them for chemical transformation. Raw materials such as chalk, clay, and limestone are crushed and milled before heating in furnaces, pre-heaters, and coolers to obtain clinker. This clinker is ground, blended with gypsum, and packed.
The crushing and grinding processes consume most electrical energy; clinker grinding accounts for 38% of total electricity consumption, while raw material crushing uses 33%. Other energy consumers are air blowers, fuel delivery, and motors in kilns.
Energy-saving measures during grinding are key aspects of sustainable cement production. MCDM methods help assess and prioritize energy-saving alternatives effectively. Thus, this study employed Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), VIekriterijumsko KOmpromisno Rangiranje (VIKOR), ÉLimination Et Choix Traduisant la REalité (ELECTRE), and Weighted Sum Model (WSM) approaches to assess and rank alternatives according to standards.
Methods
The researchers examined six grinding processes to enhance heat efficiency in the cement sector. These included improved grinding media (IGM) or ball mill internals, high-pressure roller press (HPRP), vertical roller mills (VRMs), high-efficiency classifiers (HECs), horizontal roller mills (HRMs), and process control and management in grinding mills (PCMG).
The above alternatives were evaluated across energy consumption’s technical, financial, and environmental dimensions through the following scenarios: energy/fuel savings, electricity savings, cost, emission reduction, and payback period. Additionally, a scenario giving equal weightage to all these dimensions was also considered.
Entropy and MCDM methods were employed to rank energy efficiency alternatives in cement production to achieve net-zero emissions and reduce greenhouse gas emissions. Shannon’s entropy was used to determine the relative significance of evaluation criteria while reducing decision-making bias. This entropy weight method derived objective weights from real data.
Subsequently, four MCDM methods were applied to rank energy efficiency options, comprehensively examining possibilities. The combination of WSM, TOPSIS, VIKOR, and ELECTRE methods enhanced the study’s replicability and credibility. Based on these, comprehensive guidelines were framed for the cement sector to promote sustainable and efficient production approaches and net-zero emissions.
Finally, a sensitivity analysis was performed to assess the robustness of the MCDM methods under different conditions, exhbiting their flexibility and consistency in results regardless of variations in criteria weights.
Results and Discussion
The application of Shannon’s entropy to the initial data for energy savings in finish grinding gave the weights and rankings for each evaluation criterion. Electric savings (kWh/ton) emerged to be the most crucial factor for the cement industry. It was followed by emissions reduction (kgCO2/ton), cost (USD/ton), payback period (years), and energy/fuel savings (GJ/ton).
The sensitivity analysis involving different weight assignments revealed the influence of varying criterion weights on method rankings. Therefore, criterion weightings played an important role in determining decision outcomes.
MCDM-based decision-making exploited the aggregation approach to incorporate individual choices, perspectives, or assessments into an ultimate decision. The alternative receiving the maximum points and the highest rank was considered the best. Additionally, using Shannon’s entropy with the MCDM approaches resulted in a more sophisticated analysis of energy-efficient solutions.
Considering the equal weight scenario, the explored alternatives ranked as HRM>VRM>IGM>HPRP>PCMG>HEC. Additionally, the HRM alternative turned out to be best in the scenarios prioritizing energy/fuel savings, electricity savings, and payback period. Alternatively, VRM was most suitable for cost and emission reduction.
Apart from promoting sustainability in the cement industry using alternatives like HRMs and VRMs, the authors suggest governmental efforts to encourage the adoption of energy-efficient grinding methods through subsidies, incentives, or regulations. Additionally, research institutions and industry associations should collaborate to share best practices and study the effectiveness of these methods.
Conclusion
Overall, the researchers effectively integrated entropy and MCDM methods to develop a framework for guiding the cement sector toward sustainable practices and attaining net-zero emissions. While Shannon’s entropy was employed for unbiased criteria significance identification, four MCDM methods were used to rank energy-efficient options.
The assessment of six scenarios demonstrated the proposed framework’s flexibility, emphasizing the versatility of the HRM and the emission-reduction capabilities and cost-effectiveness of VRMs. Thus, this interdisciplinary approach provided valuable insights to align global sustainability goals and economic viability.
However, the researchers suggest conducting a further analysis beyond emissions reduction to consider the influence of the discussed alternatives on biodiversity, resource conservation, and the overall ecological footprint. Additionally, scalability, lifecycle analyses, and long-term environmental benefits should be considered to effectively comprehend sustainable methods in the cement sector.
Journal Reference
Ahmed, M. S., Tasnim, A., & Kabir, G. (2024). From Grinding to Green Energy: Pursuit of Net-Zero Emissions in Cement Production. Engineering Proceedings, 71(1), 8. DOI: 10.3390/engproc2024076008, https://www.mdpi.com/2673-4591/76/1/8
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