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Show 2.1.23 In Fig.9. the measured curve for a willow cylinder (height 15 and diameter 24 mm, V/S=3.3 mm) is compared with the calculated points for a plate having the same V/S ratio. The value 610 kJ/kg for the heat of pyrolysis gives a good agreement. The furnace was insulated and the wall temperature was estimated to be in the range 793...823 K. It should be stressed that the good correspondence between the measured and the calculated results may partly be accidental, since the material properties are not accurately known. In Fig.10. measured results for dried willow cylinders of different shape having approximately the same V/S ratio are presented. The furnace walls were uninsulated in these experiments, but the conditions are approximately the same in all tests. It can be seen that the curves nearly coincide, the ratio V/S is slightly greater for the cylinder B, which may be the reason for the difference. MASS FLOW RATE/INITIAL MASS 1 u MASS/INITIAL MASS ^Sk u=0 X s Tr=873 K V > G "\v \) (UNINSULATED '\ w A FURNACE, NOT \/\ B KNOWN), SAME \ J FOR ALL TESTS c\ N c \ S GAS VELOCITY WILLOW CYLINDERS \ ' \ 0.9 M/S (HEIGHT X DIAMETER)*^ -v A 15 X ?H MM7 ^V"*-- 7" - B 20 X 20 INITIALLY C 30 X 17 (SHRINKAGE OCCUR DURING PYROLYSIS) 1 INITIAL DENSITY/ FINAL DENSITY A '197/196 . B 508/203 \>C 514/189 TIME (S) 300 TIME (S) Fig.10. The effect of the shape (measured) for dried cylinders. Fig.11. Comparison of theoretical results with the measurements for a finite cylinder, when u=0.70. MASS FLOW RATE/INITIAL MASS MASS/INITIAL MASS U=0.70 ?0 = 381 KG/HJ | = 3.HI MM 0.004 (1/S) 0.002 0 300 TIME (SECONDS) 600 i / \ \ / \ PLATE > \ w V u=C70 ' \\Jf\ \ MEASURED \ VN \ /<CYLINDER,16x21) \ \ ^CYLINDER (INFINITE) SPHERE >. 0 300 TIME (SECONDS) 600 When the initial moisture content increases, the shape of the particles has more influence on the curves. In Fig.11. the measured curve is compared with the thoeretical results. The shape of the measured cylinder (height 16, diameter 24 mm) is between a plate |