Session: 01-01: Decarbonizing Industrial Processes

Paper Number: 156191

156191 - Waste Heat Recovery With Carbon Capture for Sustainable Aluminum Smelter Operation 

Abstract: 

In the modern industrial landscape, primary aluminum plants are grappling with significant challenges, primarily revolving around low energy efficiency and high pollutant emissions. Addressing these issues is crucial for achieving energy conservation and emission reduction targets. A promising approach lies in the implementation of waste heat recovery systems coupled with greenhouse gas removal technologies. This investigation focuses on developing an innovative and efficient system that integrates waste heat recovery with carbon capture, aiming to enhance overall process efficiency and sustainability in aluminum production.

The proposed system integrates two key configurations: a parallel two-stage Organic Rankine Cycle (PTORC) and a monoethanolamine (MEA) post-combustion CO₂ capture system. The PTORC is designed to recover waste heat from various sources within the aluminum plant, including exhaust gases and electrolytic cell sidewalls. This recovered heat is then utilized to generate additional power, which supports the CO₂ capture process. The MEA-based CO₂ capture system, on the other hand, is employed to remove carbon dioxide from the flue gases produced during aluminum smelting.

A series of modeling activities were conducted to size and optimize each subsystem individually, ensuring their reliable integration with other system components. This comprehensive modeling approach involved sensitivity analyses of various operational parameters to understand their impact on the overall system performance. Key performance indicators (KPIs) were identified and utilized to evaluate the system's effectiveness. These KPIs focused on maximizing power generation and enhancing carbon capture capacity, and minimizing the increase in aluminum production costs.

The sensitivity analyses revealed several crucial insights into the operation and optimization of the integrated system. For instance, it was found that integrating waste heat sources through the PTORC could supply approximately 42% of the energy required for CO₂ capture from flue gases with a CO₂ concentration of 1.7% by volume. This significant contribution highlights the potential of waste heat recovery in reducing the external energy demands of the CO₂ capture process.

Furthermore, the integration of the PTORC with the CO₂ capture system demonstrated a notable cost advantage. Specifically, employing the PTORC reduced CO₂ capture costs by 20%, compared to a scenario where a simple Organic Rankine Cycle (ORC) was used to recover waste heat from the exhaust flue gases alone. In contrast, relying solely on a simple ORC for waste heat recovery resulted in a 3.1% increase in CO₂ capture costs. This finding underscores the economic viability and efficiency of the parallel two-stage configuration over simpler waste heat recovery methods.

Despite the benefits, the integration of the waste heat recovery and carbon capture system is not without its economic implications. The overall implementation of this innovative system is projected to result in a 2.67% increase in aluminum production costs. While this cost increment may appear significant, it is important to weigh it against the long-term environmental and operational benefits. The enhanced energy efficiency and reduced emissions align with global sustainability goals and regulatory requirements, potentially leading to cost savings in compliance and improved market competitiveness.

In conclusion, the investigation demonstrates that an integrated system combining PTORC and MEA-based CO₂ capture offers a viable pathway for primary aluminum plants to enhance energy efficiency and reduce pollutant emissions. By effectively utilizing waste heat and optimizing carbon capture processes, aluminum production can become more sustainable and economically feasible. The findings provide a compelling case for further research and development in this area, paving the way for broader adoption of integrated waste heat recovery and carbon capture systems in the aluminum industry and beyond.

Presenting Author: Mohamed Ali Khalifa University of Science and Technology

Presenting Author Biography: Dr. Mohamed Ibrahim Hassan Ali is an Associate Professor of Mechanical and Nuclear Engineering at Khalifa University, UAE, and the Thermal Theme Lead at the Center of Membrane and Water Technologies (CMAT). He specializes in hydrogen, biofuels, and syngas combustion, with significant contributions to energy systems, including industrial burner design and water desalination. With over 140 publications, his work enhances energy efficiency and sustainability, particularly in the integration of renewable energy and waste heat recovery.