A fluidized bed moisture-based direct air capture system for carbon capture and utilization applications

Direct air capture offers a decentralized pathway for supplying CO2 to low-concentration utilization applications, including controlled environment agriculture, microalgae cultivation, biocatalytic conversion, and enhanced weathering. Solid sorption is favored for these applications, yet existing technologies require complex and expensive equipment to manage heat for desorption and/or regeneration. Here we present a fluidized bed direct air capture system that uses controlled liquid water spray to drive moisture-swing desorption from a commercial ion exchange resin, using low-grade heat only for sorbent drying (regeneration) where inlet air temperature is increased to 36–43 °C. Breakthrough experiments revealed moisture-activated CO2 uptake, with optimal performance at 20–40% relative humidity and capacity reaching 3.080 mmol g−1 at 35 °C and 400 ppm. A prototype operating cyclically on 2.8 kg of sorbent achieved productivity of 8.7 gCO2 kgsorbent−1 h−1, electrical energy for the fan of 2.5–3.1 kWh kgCO2−1, and thermal energy for regeneration of 14.7–42.7 MJ kgCO2−1. We demonstrate performance is strongly governed by regeneration conditions, water injection volume and inlet air conditions, with warm, dry conditions yielding the best performance.