%0 Journal Article
%K Formaldehyde
%K HVAC
%K Carbon dioxide
%K Regenerative sorbent
%A Xiaochen Tang
%A Sébastien Houzé de l’Aulnoit
%A Mark T Buelow
%A Jonathan L Slack
%A Brett C Singer
%A Hugo Destaillats
%B Indoor Air
%D 2020
%G eng
%R https://doi.org/10.1111/ina.12695
%T Performance of a CO2 sorbent for indoor air cleaning applications: Effects of environmental conditions, sorbent aging, and adsorption of co-occurring formaldehyde
%8 05/2020
%X <p>Indoor air cleaning systems that incorporate CO2 sorbent materials enable HVAC<br />load shifting and efficiency improvements. This study developed a bench-scale experimental<br />system to evaluate the performance of a sorbent under controlled operation<br />conditions. A thermostatic holder containing 3.15 g sorbent was connected to a<br />manifold that delivered CO2-enriched air at a known temperature and relative humidity<br />(RH). The air stream was also enriched with 0.8-2.1 ppm formaldehyde. The CO2<br />concentration was monitored in real-time upstream and downstream of the sorbent,<br />and integrated formaldehyde samples were collected at different times using DNPHcoated<br />silica cartridges. Sorbent regeneration was carried out by circulating clean air<br />in countercurrent. Almost 200 loading/regeneration cycles were performed in the<br />span of 16 months, from which 104 were carried out at reference test conditions<br />defined by loading with air at 25°C, 38% RH, and 1000 ppm CO2 and regenerating<br />with air at 80°C, 3% RH and 400 ppm. The working capacity decreased slightly from<br />43-44 mg CO2 per g sorbent to 39-40 mg per g over the 17 months. The capacity increased<br />with lower loading temperature (in the range 15-35°C) and higher regeneration<br />temperature, between 40 and 80°C. The CO2 capacity was not sensitive to the<br />moisture content in the range 6-9 g/m3 and decreased slightly when dry air was used.<br />Loading isothermal breakthrough curves were fitted to three simple adsorption models,<br />verifying that pseudo-first-order kinetics appropriately describes the adsorption<br />process. The model predicted equilibrium capacities decreased with increasing temperature<br />from 15 to 35°C, while adsorption rate constants slightly increased. The<br />formaldehyde adsorption efficiency was 80%-99% in different cycles, corresponding<br />to an average capacity of 86 ± 36 μg/g. Formaldehyde was not quantitatively<br />released during regeneration, but its accumulation on the sorbent did not affect CO2<br />adsorption.</p>