Techno-economic analysis of vanillin production from Kraft lignin: Feasibility study of lignin valorization.

Kraft lignin waste is valorized by converting it into vanillin via the oxidation process. To obtain the highest yield of vanillin, feed concentration of lignin, reaction temperature, and oxygen partial pressure are optimized. Three separation cases, i.e. solvent extraction followed by distillation (Case I), solvent extraction (Case II), and vacuum distillation (Case III) are simulated and compared to identify the most suitable separation process. The results reveal that the highest vanillin yield of 9.25% is attainable using feed concentration of Kraft lignin of 30 g/l, operating temperature of 110 °C, and oxygen partial pressure of 5 bars. Case I appears to be the most suitable method of separation since it consumes the lowest amount of energy and gives the best economic returns, with a payback period of 6.19 years and internal rate of return (IRR) of 22.63%.