Studies on CO2 capture using adsorption from simulated refinery flue gas

Abstract

Carbon dioxide (CO2) capture is a major concern around the world because of its detrimental impacts on the Earth. As a mitigation measure, solid-based adsorbents have been extensively investigated to capture CO2 from dilute flue gas streams. It has been observed, in general, that CO2 adsorption-regeneration studies have been carried out on different types of adsorbents based on alkali metal carbonates as active precursor. So far, a great amount of work has been progressed with K2CO3-based adsorbents, still there is huge scope to improve the adsorption-regeneration characteristics of CO2 adsorbents; particularly to increase the capture capacity, effective dispersion of active phase (like K2CO3) inside the porous structure and stability after multiple tests. Moreover, activity of these K-based adsorbents in continuous CO2 removal is merely reported so far. The development of low cost, energy efficient CO2 capture process is also needed to minimize CO2 emissions into the atmosphere. The present work intends to bridge the gaps related with the improvement in both adsorbent and process development. CO2 adsorption studies were performed using a series of adsorbents prepared by incipient wet impregnation method. Several adsorbents using alumina-clay as support and sodium carbonate (Na2CO3) as active component were prepared and characterized for textural properties with the objective to correlate with CO2 adsorption and desorption. The effects of adsorption temperature, Na2CO3 loading on the support material and feed CO2 concentration were evaluated using simulated flue gas with 3 9 vol% CO2, 2.5 vol% H2O and balance N2 at 55 °C in a fixed bed reactor. 20-wt% Na2CO3 based adsorbent showed maximum CO2 adsorption capacity of 0.39 mmol/g of adsorbent at flue gas temperature of 55 °C and CO2 content of about 8 v/v %. At increased adsorption temperature, CO2 adsorption capacity of this adsorbent decreases. The best fitted parameters, Vm of 0.875 mmol/g and k of 0.148 bar-1 using the Langmuir equation are estimated.