(509) Techno-Economic Evaluation of an Integrated Membrane-Based Direct Air Capture and Steel Slag Mineralization System

This presentation covers a process systems and techno-economic evaluation of a membrane-based direct air capture (m-DAC) process integrated with steel-slag mineralization for CO₂ utilization. The study addresses the rising need for scalable carbon dioxide removal technologies capable of offsetting both ongoing and historical emissions, while producing useful materials from captured CO₂. Our work investigates the capture and utilization combined into a single framework, enabling early assessments of both process performance and economic viability in a realistic and current industrial context. The m-DAC process was simulated in AVEVA Process Simulation as a multistage hollow-fiber membrane system and analyzed using the operability framework. Operability provided a systematic approach to identify feasible and optimal operating regions early in the design phase, linking intrinsic membrane and material properties achievable CO₂ capture levels and system energy efficiency. This early-stage assessment allows screening of process configurations prior to detailed design, reducing engineering time and identifying bottlenecks. Inverse design methods and machine-learning algorithms were then incorporated to determine the combinations of CO₂ permeance and CO₂/N₂ selectivity that meet target capture performances. The results showed that performance is primarily governed by the first-stage membrane, where high permeance (6000–7000 GPU) and selectivity (~2000) produced permeate concentrations of approximately 5% CO₂, 120 times higher than ambient levels (420 ppm), at an estimated minimum cost of $3000 per ton CO₂. The study was also extended to facilitated-transport membranes (FTMs), introducing equilibrium and diffusion parameters (Keq, DCO2) to explore performance improvements at DAC conditions. The optimized system achieved capture rates of 1.2 tons CO₂ per day, supplying a downstream steel-slag mineralization unit that consumed roughly 950–970 tons CO₂ per year. The Techno-Economic Analysis (TEA) of the integrated system demonstrated breakeven potential at carbonated-slag prices between $99 and $116 per ton, across a 45 year lifespan. Overall, this work shows how coupling operability, process simulation, and data-driven tools can accelerate the evaluation and scale-up of emerging capture technologies, bridging experimental membrane developments with practical, carbon removal process deployment.