Optimization strategies for the low-temperature NACO pulping process of sugarcane bagasse and response surface modeling

Abstract

This study focuses on using agricultural straw—specifically sugarcane bagasse—as the raw material and employs single-factor optimization and response surface modeling strategies to develop a low-temperature NACO pulping process. A mathematical prediction model was constructed to explore the leaching patterns of chemical components in sugarcane bagasse, reveal the reaction mechanism of selective lignin removal through the new oxygen-alkali synergistic approach, and elucidate the green pulping mechanism of the low-temperature NACO method. The research findings indicate that at a temperature as low as 114.3 °C and a Na₂CO₃/ NaOH mass ratio of 1.86, the paper pulp exhibits optimal performance, with a freeness yield of 52.83%, a viscosity of 675.77 ml/g, a whiteness of 40.95% ISO, and a kappa number of 19.85. At this condition, only 43.96% of the silicon element enters the black liquor. Response surface variance analysis shows that the studied variables have statistically significant effects on different response levels, with all correlation coefficients (R²) greater than 0.93, indicating that the model has good predictive capability for the low-temperature NACO pulping process. Finally, the paper produced from the pulp under the optimal conditions exhibits excellent physical properties, with a tear index of 4.9 kPa·m²·g⁻¹, burst index of 3.8 mN·m²·g⁻¹, tensile index of 70.9 N·m·g⁻¹, and ring crush index of 11.6 N·m·g⁻¹, which are 1.9, 1.8, 1.6, and 2.3 times, respectively, compared to the performance of paper made by traditional oxygen-alkali chemical pulping methods.