Devolatihdtion and combustion of large particles of Eastern Canadian coals (Evans and Minto), 5-50 mm dia., were studied in a bench-scale atmospheric fluidized bed reactor at 1023-1 173 K with 0.5 mm sand particles as the bed material. The devolatilization time, mass loss history, changes in proximate volatiles content and C/H mass ratio, and temperature history at the centre of the particle during devolatilization were determined. The mass loss during devolatilization is correlated with the proximate volatiles content of the parent coal. The devolatilization time is correlated with the initial particle diameter by a power-law relation with an exponent of 1.54-1.64. The results show insignificant effect of superficial velocity on devolatilization.On a CtudiC la dtvolatilisation et la combustion de larges particules de charbon de I'Est du Canada (Evans et Minto), dc 5 a 50 mm de diamktre, dans un reacteur B lit fluidis6 atmospherique de laboratoire, 2i des tempkratures de 1023 a I173 K et avec des particules de sable de 0,5 rnm de diamhre comme matCriau du lit. On a determine le temps de devolatilisation, l'histoire de la perte de masse, les changements dans la teneur des volatils voisins et le bilan massique C/H ainsi que I'histoire de la temperature au centre de la particule durant la dbvolatilisation. La perte de charge durant la dkvolatilisdtion est corrClCe ? i la teneur des volatils voisins d'un chdrbon apparentk. Le temps de dtvolatilisation est corrCIC au diamktre initial des particules par une relation de loi de puissance avec un exposant de 134-I ,64. Les rtsultats montrent un effet non significatif de la vitesse superficielle sur la devolatilisation.
Devolatilization and char burning were studied in an electrically heated bench-scale fluidized-bed reactor at 750 to 900°C bed temperature, gas oxygen mole fractions ranging from zero to 0.21, superficial gas velocities from 0.3 to 0.7 m/s and coal particle diameters 5 to 3.5 mm. The coals investigated include lignite, bituminous and anthracite. The coal devolatilization and char burning times, H/C ratio histories, and particle fragmentation were measured. Statistical correlations with the operating variables were developed for the devolatilization time. A mathematical model is given for the combustion of char. Most predictions of the model agree quite well with the experimental results.On a CtudiC la dCvolatilisation et la combustion de produits de carbonisation dans un riacteur a lit tluidisk chauffe h I'ilectricitb 9 1'Cchelle exPCrimentale pour des temperatures de 7.50 a 900°C. des fractions molaires de I'oxygkne gazeux de zbro 9 0,21, des vitesses superficielles de gaz de 0,3 2 0,7 m/s et des diamkres de particules de charbon de 5 9 35 mm. Les charbons CtudiCs comprennent la lignite, les bitumineux et I'anthracite. On a mesurC la dCvolatilisation du charbon et les temps de combustion des produits de carbonisation, I'histoire des rapports HIC ainsi que la fragmentation des particules. Des corrClations statistiques du temps de dtvolatilisation avec les variables de fonctionnement ont CtC mises au point. On prCsente un modele mathCmatique pour la combustion des produits de carbonisation. La plupart des prCdictions du modMe concordent relativement bien avec les rCsultats experimentaux.
Trials on the burning of Syncrude coke (solid residue of Athabasca oil sands after processing at the Syncrude plant, Fort McMurray, Alberta), were performed in an atmospheric fluidized bed combustion (AFBC) pilot plant (bed area 0.155 m2 ). The coke is high in sulphur, up to 7% by mass, and reduction of SO2 emissions is therefore necessary. An Athabasca limestone was used as the SO2 sorbent. The conditions of the trials were mean coke particle diam. 0.26 mm; mean limestone particle diam. 0.34 - 0.94 mm; fluidizing velocity 0.8 - 1.3 m/s; excess air, up to 7%; recycle ratio (fraction of cyclone catch recycled) 0 - 0.83; Ca/S mole ratio 1.7 - 2.9; bed temperature 966 - 1105 ° C. The high bed temperatures were needed to achieve stable burning and reasonable combustion efficiency. The combustion efficiency as measured by carbon burnup was 77 - 97%. At these temperature levels, sulphur capture was influenced most strongly by bed temperature. The capture was unexpectedly good up to 1050 ° C then fell sharply, practically to zero above 1100 ° C. It is concluded that Syncrude coke can be burned by AFBC with acceptable combustion efficiency and sulphur capture at bed temperatures of 950-1050 ° C and fluidizing velocities up to 1.3 m/s. Syncrude coke is high in vanadium, 0.18% by mass, as well as in sulphur. The results indicate that the vanadium is fixed in the ash and is not selectively concentrated in any of the product streams.
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