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Ca(OH)2 superheating as a low - attrition steam reactivation method for CaO in calcium looping applications / Vlatko Materic in Industrial & engineering chemistry research, Vol. 49 N° 24 (Décembre 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 24 (Décembre 2010) . - pp.12429-12434 Titre : Ca(OH)2 superheating as a low - attrition steam reactivation method for CaO in calcium looping applications Type de document : texte imprimé Auteurs : Vlatko Materic, Auteur ; Susan Edwards, Auteur ; Stuart I. Smedley, Auteur Année de publication : 2011 Article en page(s) : pp.12429-12434 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Attrition  rate  Calcium  Carbonation/calcination  cycle  Dehydration  Dehydration  reactions  Dewatering  Fluid-beds  Fluidization  Free  lime  Heat  storage  Hydration  Initiation  temperature  Lime  Non  equilibrium  Reactivation  process  Sorption  Steam  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 [...] [article] Ca(OH)2 superheating as a low - attrition steam reactivation method for CaO in calcium looping applications [texte imprimé] / Vlatko Materic, Auteur ; Susan Edwards, Auteur ; Stuart I. Smedley, Auteur . - 2011 . - pp.12429-12434. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 24 (Décembre 2010) . - pp.12429-12434 Mots-clés : Attrition  rate  Calcium  Carbonation/calcination  cycle  Dehydration  Dehydration  reactions  Dewatering  Fluid-beds  Fluidization  Free  lime  Heat  storage  Hydration  Initiation  temperature  Lime  Non  equilibrium  Reactivation  process  Sorption  Steam  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 [...]