| Titre : | Ca(OH)2 superheating as a low - attrition steam reactivation method for CaO in calcium looping applications (2011) |
| Auteurs : | Vlatko Materic, Auteur ; Susan Edwards, Auteur ; Stuart I. Smedley, Auteur |
| Type de document : | Article : texte imprimé |
| Dans : | Industrial & engineering chemistry research (Vol. 49 N° 24, Décembre 2010) |
| Article en page(s) : | pp.12429-12434 |
| Note générale : | Chimie industrielle |
| Langues : | Anglais |
| Tags : | Attrition rate Calcium Carbonation/calcination cycle Dehydration reactions Dewatering Fluid-beds Fluidization Free lime Heat storage Hydration Initiation temperature Lime Non equilibrium Reactivation process Sorption Steam hydration Superheated state Temperature Thermodynamic equilibria water vapor |
| Résumé : | Steam hydration of lime is an effective method for restoring CO2 capture activity but gives rise to high particle attrition rates in a fluid bed reactor. This paper describes the phenomenon of Ca(OH)2 superheating, also referred to as superheated dehydration (SD). The potential of an attrition-free lime reactivation process using this phenomenon is also investigated. Attrition rates of the sorbent are measured when a reactivation step using steam hydration is implemented every three carbonation/calcination cycles. It has been shown that the presence of CO2 during the dehydration step reduces attrition during subsequent cycles. Experiments performed in a small fluid bed reactor show that the presence of 40-100% CO 2 during the dehydration step increases the initiation temperature of the decomposition of Ca(OH)2 from 445 to 618 °C. The thermodynamic equilibrium water vapor pressure for the dehydration reaction at 618 °C is 516 kPa, whereas no water vapor was detected in the reactor during the dehydration step before the temperature reached 618 °C. Under these circumstances it is proposed that the Ca(OH)2 is in a nonequilibrium "superheated state". A CO2 capture cycling experiment, with a reactivation step every three carbonation/calcination cycles, maintained an average activity of 60%, creating only 3.25% of fines < 150 μm after 28 carbonations. The reactivation step consisted of hydrating the sorbent at a temperature of 270 °C and dehydrating it in 100% CO2 with a 23 min hold at 520 °C. It is proposed that the SD phenomenon may be a key step in the development of an industrially feasible method of lime reactivation for use in CO2 capture and in thermal energy storage applications. © 2010 American Chemical Society. |
| DEWEY : | 660 |
| ISSN : | 0888-5885 |
| En ligne : | http://www.irl.cri.nz/caoh2-superheating-low-attrition-steam-reactivation-method-cao-calcium-looping-applications |
