Sunflower Seeds Liquefaction for Bio-char Production: Parametric Optimization via Full Factorial Design

This paper aimed to investigate the conversion of sunflower seeds to bio-char through hydrothermal liquefaction (HTL) process. The effect of reaction temperature (X-1, 240-320 degrees C), residence time (X-2, 10-60 min) and biomass/solvent ratio (X-3 , 20-80%) was analyzed and optimized using full factorial design of response surface methodology. The developed regression model gave accurate predictions and fitted well with the experimental results with a determination coefficient R-2 of 92.89%. The optimized conditions for bio-char production have been found to be 240 degrees C, 60 min and 20%, temperature, time and biomass to solvent ratio, respectively. These optimum values were validated by experimental runs which produced a bio-char yield of 32.24 wt% with higher heating value of 32.24 MJ/kg and high carbon content of 65.45%. The quadratic model revealed a strong interaction between reaction temperature and residence time, as well as, reaction temperature and biomass/solvent ratio. Based on the thermal decomposition mechanism of bio-char, derivative thermogravimetry revealed two major peaks were observed at 275 and 400 degrees C indicating the improvement in thermal stability of the bio-char after HTL process. In addition, the obtained bio-chars were different in terms of their organic and ash content depending on the HTL operating conditions.

Automated summary

This paper investigated the conversion of sunflower seeds to bio-char through the hydrothermal liquefaction (HTL) process. The optimized conditions for bio-char production were determined and validated, resulting in high bio-char yield, high heating value, and high carbon content. Derivative thermogravimetry analysis revealed an improvement in the thermal stability of the bio-char after the HTL process.