Influence of process variables on the properties of pulp obtained by ethanol pulping of wheat straw

The influence of independent variables in the cooking of wheal straw with e thanol-water mixtures (ethanol concentration, cooking time and temperature) on various properties of the pulp (yield and holocellulose, alpha-cellulos e and lignin contents) was studied with a view to determining the best oper ating conditions to obtain quality pulp (pulp with high holocellulose and a lpha-cellulose contents and a low lignin content). The results were fitted to a second-order polynomial function using a BMDP system package and a 2(m ) central composite design. In this way, equations that reproduce yield and the holocellulose and alpha-cellulose contents with errors less than 3.5% and lignin content with errors less than 15% were derived. Additional equat ions were obtained that relate dependent variables to the treatment severit y parameter, R-o and reproduce the experimental yields and holocellulose, a lpha-cellulose and lignin contents with errors less than 10, 4, 4 and 15%, respectively. Obtaining pulp with high holocellulose and alpha-cellulose co ntents and a low lignin content, entails using a high temperature (190 degr ees C) and ethanol concentration (80%) for a long time period (2 h). (C) 19 99 Elsevier Science Ltd. All rights reserved.