Insights into High Temperature Sorbents for Carbon Dioxide

This article reports on an experimental research dealing with the use of solid sorbents for CO2 uptake from gaseous stream at high temperature. Hydroxyl-apatite and strontium carbonate have been adopted as starting materials for preparing a regenerable sorbent, upon calcination. Both sorbents have been characterized in TG tests with an alternating atmosphere of CO2/Ar and Ar, accomplishing steps of carbonatation and calcination/regeneration at temperature over 900 degrees C. The apatite based sorbent maintained its capability of CO2 absorption for several cycles, whilst the Sr based sorbent exhibited a quick decay of its capability due to changes of the micro-structure. The CO2 carrying capacity after conditioning reached stable values of around 3% and 5% for apatite and strontium sorbents, respectively. TG curves were worked out in order to obtain kinetic data for both carbonatation and calcination, showing that apatite is slightly more reactive than strontium sorbent. The TG tests were also complemented by a fixed bed experiment aimed at demonstrating the feasibility of apatite regeneration with steam.