| Čoahkkáigeassu: | in the thermal cracking of sub-bitumenous coal tar, under non-isothermic condition, the long chain paraffins would crack to form methane, propane, butane, acetylene, and hydrogen. The pyrolysis was conducted in a retort made of Stainless-steel 304, 40 cm long and 2.54 cm inside diametre, equipped with some type K thermocouples. A tube furnace, Thermolyne F21-100 with a power of 1350 W, was used as the heat source. The furnace was operated at low level heating rate. Based on the plug-flow reactor model and a simple pseudo single C181-138 9C2Hq +H2, a mathematical model could be
arranged as follows :
�FT �d: = D241 � X)/(1 + 9X)r (P / RT)"
dT �FT (9HFc2114�HFCiaH38)(dXIdz)U2ztD(T�Tf) dz FT (1� X)Cpci81138 + FT X Cp H2 + 9FT X Cpc2R,
with k =A exp(-E/R'/T) and FT was the molar flow rate of the tar vapour entering the reaction zone.
By solving those equations numerically and comparing the results to the experimental data, the kinetic parameters could be evaluated. The mathematical model was close to the experimental data, and it worked best at the range of the reaction temperature of 985 K to 1113 K, and at the average temperature gradient of 9,14 ° C/min. Under this condition, the value of reaction order (n) was 1.1, and the relationship between reaction rate constant and the reaction temperature could be represented by :
k = 139072 exp(-17867/R'/T).
Key words : long chain paraffins, coal-tar, thermal cracking
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