Influence of the variables of the olive pruning grazed process with ethanolamine and soda on the pastes composition

It is studied the influence of the independent variables of the olive pruning wood grazed process with ethanolamine and soda [temperature (165-195 °C), cooking time (30-90 minutes), ethanolamine concentration (5-15%), soda concentration (2,5-7,5%) and liquid/solid relationship (4-6)] on the dependent variables (yield and paste content of holocellulose, α-cellulose and lignin) with the purpose to find the more appropriate working conditions, using a composed and centered factorial design of experiments. With the BMDP programme, there are some equations that relate the dependent variables considered with the independent variables of the grazed process, which reproduce the values of the former with errors lowerr than 8%. To obtain a paste with maximum content of holocellulose and α-cellulose (84,0% and 68,3%, respectively) and minimum amount of lignin (11,4%), it is necessary to work at high concentrations of ethanolamine and soda; temperature must also be high, except in case of holocellulose content that must be of 187 °C; cooking time must be long in case off lignin content; and liquid/solid relationship must be intermediate for α-cellulose content and low for lignin content. At high temperature, with high soda concentration and low ethanolamine concentration, and for saving locked up capital, with low values of cooking time and liquid/solid relationship, pastes with a yield of 38,2% and contents of holocellulose and α-cellulose which differ only in amounts of 5,1% and 7,5% of their optimum values, respectively, but with a lignin content increased in a 89,5% over the minimum value, are obtained, and those pastes will therefore be employed for the manufacture of not necessarily white papers. If the above mentioned conditions are modified, working at low temperature and high ethanolamine concentration, the yield will be of 39,0% and the holocellulose, α-cellulose and lignin content variations, with regard to their optimum values, will be of 11,1%, 11,9% and 50,9%, respectively, and this will mean a saving of heating energy and a whiter paste, although with more consumption of ethanolamine. For bleaching pastes, it is necessary to work with high concentrations of ethanolamine and soda, a medium-high temperature value (187 °C) and low values for the rest of the variables, and therefore, there will be a saving of locked up capital and energy, and pastes with small variations of holocellulose, α-cellulose and lignin content (0,0%, 5,3% y 8,2%, respectively), with regard to their optimum values, and with a better use of raw material (40,1% yield) will be obtained.