A Process for Capturing CO2 from the Atmosphere
By: DW Keith (August 15, 2018)
The article outlines a process for capturing CO2 from the atmosphere on an industrial scale. The process is continuous, utilizing an aqueous KOH sorbent in conjunction with a calcium caustic recovery loop. After detailing the design and its rationale, the authors share results from a pilot plant, emphasizing the performance of key unit operations. The process requires significant energy inputs, ranging from 8.81 GJ of natural gas to a combination of 5.25 GJ of gas and 366 kWhr of electricity for every ton of CO2 captured. Depending on various factors, the estimated cost per ton of CO2 captured fluctuates between $94 and $232.
Direct Air Capture (DAC) has been explored since the 1950s, first as a pre-treatment for cryogenic air separation, later as a feedstock for hydrocarbon fuel production, and most recently as a tool for managing climate risk. Despite the rising interest in DAC, no prior paper has provided a design and comprehensive engineering cost basis for a complete DAC system built on commercial engineering heritage or detailed enough for third-party assessments. The article attempts to fill this gap, focusing on DAC processes using solid sorbents or aqueous basic solutions as the capture media, each having their own advantages and challenges.