Optimization of Parcticle Size for Hydrolysis of Pine Wood Polysaccharides and Its Impact on Milling Energy

Abstract

Wood milling is an intensively energy consuming operation that has a significative effect on energy yield of ethanol processes as particle size is an important factor in productivity of saccharification methods. We optimized fiber particle size for  a very wide range of treatment conditions (temperature, agitation, and solid loads) for acid hydrolysis in a batch reactor. We also analysed heat and mass transfer effects by calculating the Thiele and Prater modulus at experimental conditions. Multivariate optimization results show that using a length-weighted fiber mean diameter (DL21) of 1.21-2.68 mm a better sugar yield, concentration and lower furan production can be achieved. Agitation allowed a simulteous particle size reduction and hydrolysis of polysaccharides. Heat and mass transfer studies suggest that acid diffusion is only important for hemicellulose hydrolysis at very high temperature and that particles are nearly isothermic. These results show that about 30% of the required energy for milling can be saved by using optimal particle size.

Keywords

• wood; ethanol; acid hydrolysis; saccharification;