Process design and costing of an air-contactor for air-capture

Abstract

Abstract Carbon Engineering (CE) has developed an air-contactor design, specifically optimized to the challenge of efficiently removing CO2 from atmospheric air. CE’s air-contactor design is based on the wet-scrubbing method, where air is brought into contact with an alkali hydroxide CO2-absorbing liquid solution. This is a similar process to that carried out in absorption or reactor towers commonly used in the chemical processing industry, but unique constraints posed by the challenge of removing CO2 from atmospheric air have led CE to a number of original, innovative, and proprietary design modifications to these existing technologies. These key differences have led CE to depart from traditional chemical industry practice involving packed reactor towers, and to develop an intermittently- wetted air-contactor with cross-flow slab geometry. This design has as much in common with induced draft cooling towers as with chemical reactor towers. Design has been tested in a 5 m tall packed tower prototype and detailed tests of packing performance have been performed in a laboratory system that enables us to control CO2, air velocity, relative humidity while accurately measuring packing performance. In addition to CE’s on-going in-house engineering and experimental evaluations, the structural design and cost estimation of the air-contactor system was performed by an independent Engineering, Procurement and Construction (EPC) firm (SolTech Projects Inc., Calgary, Alberta). The cost estimate produced by this EPC firm forms a conservative upper bound on the cost of the air-contactor because it is based on 2008/09 Alberta, Canada construction and labour costs, which were among the highest in the world. The EPC firm collected quotes from vendors for major equipment and components, and the total system cost was estimated using standard engineering cost-evaluation procedures. The total estimated cost of the air-contacting system, evaluated using conservative labour and energy rates as mention equates to $80/tonne- CO2 and CE has identified specific areas of research to decrease this cost to $49/tonne- CO2.