CO2 Capture From Air in a Radial Flow Contactor: Batch or Continuous Operation?

Abstract

The capture of CO2 from the atmosphere via Direct Air Capture using solid supported-amine sorbents is an important option to reduce the atmospheric concentration of CO2. It addresses CO2 emissions from dispersed sources and delivers a location independent, sustainable carbon source. This study evaluates the possibility for a continuous adsorption process for direct air capture in a radial flow contactor, using both batch and continuous mode of operation. Gas and solid flow were varied to determine hydrodynamic feasible operating conditions. The operation modes are compared by their capture efficiencies in the optimal adsorption time range of 0.5 tstoB and 1.5 tstoB. A 15–25% lower capture efficiency is found for a continuous process compared to a batch process in the relevant range for direct air capture. This decline in gas-solid contact efficiency is more pronounced at longer adsorption time and higher superficial gas velocity. Overall, a batch process is preferred over a continuous process in the majority of operating conditions.

Direct air capture: process technology, techno-economic and socio-political challenges

“…But the point to be made, is that although such a contactor can be operated in a moving-bed arrangement, batch operation (akin to fixed-bed operation) appears to offer better capture efficiency in most DAC situations due to the high air velocity, highlighting again the complexity involved in contactor assessment. 294 Sorbent regeneration strategies in the laboratory compared to practical direct air capture application where high-purity CO 2 is usually required. As above, it is also important to consider the production of high-purity CO 2 following contacting, i.e., sorbent regeneration.…”

“…186 Similar comments could be made for rotating-packed beds. By contrast, for solid sorbent DAC systems, contactors of monolithic, 283,284 fibre, 237,256 fluidized-bed, 285 fixed-bed, 206,[286][287][288][289][290][291][292] and moving-bed designs, 293,294 have all been investigated for DAC. The monolithic, fibre, fluidized-bed and fixed-bed concepts involve a temporal change in conditions to mediate sorption and desorption of captured CO 2 .…”

“…14). 286,293,294 Here the sorption stage is mediated in a radial flow contactor, where air crosses the sorbent bed in the radial direction. Radial flow contactors first appear promising as they combine high volumetric adsorption rates to minimize contactor size and costs, and low pressure drops, which tackle capital and operating costs, respectively.…”

“…But the point to be made, is that although such a contactor can be operated in a moving-bed arrangement, batch operation (akin to fixed-bed operation) appears to offer better capture efficiency in most DAC situations due to the high air velocity, highlighting again the complexity involved in contactor assessment. 294…”

Process Optimization of a Fixed Bed Reactor System for Direct Air Capture

“…For this, a kg-scale DAC experimental setup was designed. This design of the DAC system is based on design considerations identified in the studies of Yu and Brilman, (2017)) and Schellevis et al (2020). Fixed bed technology with temperature-vacuum swing adsorption (TVSA) without sorbent circulation is chosen.…”