OCR Text |
Show ,...., - 20 - and the temperature profiles during the devolatilization stage of the combustion are presented in Fig. 13, 14 and 1 5 • There are also significant temperature differences inside a fuel particle during the drying stage. The temperatures at the surface and at the centre and the temperature profiles during the drying stage are presented in Fig. 16 and 17. The result is based on the numerical solution of the equation (17). l~~~~~£l~~~S ~~~~~~ ~~W~~® m~--------------------------. d=O.ll11l11 Tg=Tw=l lOOK 1~~~~~£1~~~ ~~Sl~~~~l~@~ IIDlOlI! 16~G I!lIllI'I I ~ G ~~------------------------~ Tg=Tw=1 lOOK ~200 u=O.15 w d=O. I mm a:: ::l fa: a:: w w~ 100 f- 8.00 D CENTRE d densi ty IOOOk 1m3 0.01 TIME (s) o. ~ Fig. 17. Temperatures during the drying. ACKNOWLEDGEMENTS 8.':-0 ------'-o.z-----0....L4...-----0.L6- --'..L..-o-'.-a-------ll.o PLACE (Centre-O . Surface- I) Fig. 18. Temperature profiles during the drying. This work was financed by the Finnish National Combustion Research Program LIEKKI. NOMENCLATURE Symbols A pre-exponential constant for char combustion B combustion parameter, YOoofc(1+~a) t" heat capacity flow rate/area, m~cg c specific heat Da effective gas diffusivity in the ash layer Dg diffusivity, Do at reference temperature To d particle diameter E activation energy for char combustion |