A continuous hydrothermal pretreatment system for efficient sugar production from wheat straw

A continuous tube reactor was developed to investigate the autohydrolysis of wheat straw and its effect on enhancing enzymatic hydrolysis efficiency. The well-dispersed and stable wheat straw slurries were prepared using the wet ball-milled method to avoid clogging issues caused by particle sedimentation. The effect of operation parameters (e.g., flow rate, temperature) on the autohydrolysis of wheat straw in the continuous tube reactor was investigated. Solid recovery decreased significantly with increasing pretreatment temperature, and oligosaccharides were the predominant sugars in the liquid phase. The maximum xylooligosaccharide and arabinooligosaccharide concentrations of 4.3 g/L and 0.6 g/L were both achieved when wheat straw slurry was pretreated at 180 degrees C for 20 min. Fourier transform infrared spectroscopy analysis confirmed a significant removal of the acetyl group from hemicellulose at elevated pretreatment temperatures. Consequently, the highest final cellulose conversion during subsequent enzymatic hydrolysis was achieved at 98.9% when wheat straw was pretreated at 200 degrees C. The mass flow of the cascading process showed that 29.2 kg of glucose and 6.7 kg of xylose could be produced from 100 kg dry wheat straw, while 8.6 kg of xylooligosaccharides, 0.9 kg of glucooligosaccharides and 1.1 kg of arabinooligosaccharides can be co-produced. The exergy analysis highlighted that the utilization of lignin would significantly improve the exergy efficiency, increasing it from 29.0% to 38.5%. This study provides valuable insights into achieving and optimizing continuous hydrothermal pretreatment for integrated lignocellulosic biomass biorefineries.