Kinetics and characteristics of light oil and heavy oil cracking in the micro-fluidized bed reactor
The kinetics of tar cracking is essential to an accurate pyrolysis model and reactor design.Previous studies have predominantly focused on the overall cracking behavior of tar.However,it is evident that the cracking behavior differs significantly between light and heavy tar fractions.In order to gain a more precise understanding of the cracking behavior at different temperatures and establish a second-ary reaction model,the cracking behavior and reaction kinetics of two distinct tar fractions were investigated using a micro fluidized bed re-action analyzer(MFBRA)under Ar atmosphere conditions at 550,600,650,700 ℃.The results demonstrate that higher temperatures re-sult in increased yields of cracking-formed gases.Specifically,light tar cracking primarily produces CO and CH4,while heavy tar gener-ates CO,CH4,and H2 as its main products.Moreover,heavy tar exhibits more readily occurring cracking with shorter reaction times com-pared to light tar.By employing an isothermal method in MFBRA analysis,it is found that the average activation energy for light oil crack-ing was 49.49 kJ/mol,which is higher than that for heavy oil cracking(33.47 kJ/mol).Furthermore,by comparing activation energies obtained from isothermal methods with mechanism models,suitable mechanism functions are identified:a chemical reaction(n=2)model for CO during heavy oil cracking,three-dimensional diffusion models(spherical symmetry)for CH4 during both types of oil cracking,and a contraction geometry model(cylindrical symmetry)for H2 specifically during heavy oil cracking but not present in light oil cracking sce-narios.These results provide valuable insights into developing reasonable secondary reaction models for simulating selective oil cracking.
tar crackingkineticsmicro fluidized bedheavy tarlight taractivation energymechanism function
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