Enhancement of Eucalypt Pulp Yield through Extended Impregnation Cooking

摘要

The cost of eucalypt wood has grown largely in the last decades. Therefore, techniques that improve cooking yield become ever more relevant to save wood, with the additional benefit of improving mill throughput. Thus, the objective of this work was improving kraft pulping performance in order to enhance eucalypt pulp yield. The idea was improving chip impregnation to allow for terminating the cook at kappa above the 15-20 range. It was found that extended impregnation cooking (EIC) of the eucalypt wood investigated results about 1% lignin- and HexA-free screen yield gains in relation to conventional cooking (CC), regardless of kappa number in the range of 15-27. The optimum kappa number for both CC and EIC cooking was about 19. The EIC technology allows for cooking eucalypt wood to kappa number up to 27, without rejects production, but such practice does not improve significantly the lignin- and HexA-free screen yield and causes large increase on ClO2 demand for full pulp bleaching. The refinability and strength properties of the CC and EIC pulps of kappa 19 are similar. It is concluded that extended impregnation cooking is an attractive technique for enhancing bleached eucalypt kraft pulp yield.