Techno-economic analysis of packed bed and structured adsorbent for direct air capture

Abstract

This study investigates a direct air capture (DAC) process using a solid-DAC S-VTSA (steam-assisted vacuum thermal swing adsorption) process. A commercially available sorbent, commonly used in packed bed configurations, is selected as the benchmark sorbent, while a monolithic geometry is also examined to assess its potential performance. The process is modelled using Aspen Adsorption and incorporates physico-chemical data in DAC environmental conditions, including binary isotherms under humid condition. In a reference case comparing the two geometries, the packed bed exhibits higher productivity (2.4 kgCO₂/(h.m³)), while the monolith achieves 1.2 kgCO₂/(h.m³). However, the monolith allows for a significant reduction in pressure drop and associated fan work by about two orders of magnitude. These findings highlight the trade-off between productivity in favor of packed bed and energy requirement in favor of monolithic design. A sensitivity analysis is then conducted on various environmental and process parameters such as sorbent and bed dimension, air velocity, temperature and humidity, adsorption/desorption loading, mass transfer kinetic, and regeneration pressure, temperature, and steam flowrate. Detailed techno-economic analysis, using Aspen Process Economic Analyzer software for capital cost estimation, is performed at capture scale of 100 ktCO₂/yr, with capture costs higher than 1500 €/tCO₂.