Modelling and optimization of the pyrolysis of low-rank lignite by central composite design (CCD) method

ABSTRACT

In this study, the modeling and optimization of lignite pyrolysis were investigated through Central Composite Design (CCD) by using Stat-Ease Design Expert software version 10. The process parameters such as pyrolysis temperature, heating rate, and nitrogen gas flow rate, which were thought to be the most effective on pyrolysis, were studied between initially determined levels, and oil yield was considered as the response variable. The results were assessed by Analysis of Variance (ANOVA) and a regression model was created. The model was found to be statistically significant because its p-value is smaller than 0.05. The consistency of the model was also proved by the high value of R² (0.9770). Linear effects of the studied factors were found to be statistically significant as their p-values are smaller than 0.05 while pyrolysis temperature and heating rate have quadratic effects on oil yield. Optimization studies revealed that predicted values of oil yield were validated with actual test results which were obtained from a verification experiment.

KEYWORDS:

• Modeling and optimization
• pyrolysis
• oil yield
• response surface methodology
• lignite