Low energy packed tower and caustic recovery for direct capture of CO₂ from air

We used a 6.5 m tall packed tower prototype to study the capturing rate of CO₂ from air. The tower was operated at a pressure drop of less than 27 pa in the packing at 0.7m/sec air speed with a counter current flow mode and with NaOH or KOH solution as the absorbent. The tower consumed an average of ~30 kJe per mole CO₂. We found that via an intermittent operation with a 5% duty cycle, the fluid pumping work reduced by 90%. A novel process for removing carbonates ions from alkaline solutions based on titanate compounds is compared to the traditional lime cycle for the caustic recovery. The titanate process reduces the high-grade heat requirement by ~50%. The results from experimental data of leaching and precipitation test support process design of the titanate cycle. In this paper, we also present the chemical process design.