Techno-economic Analysis of ECF Bleaching and TCF Bleaching for A Bleached Eucalyptus Kraft Pulp Mill

摘要

Due to the implementation of environmental regulations to reduce the discharge of bleached pulp effluents containing harmful levels of COC (chlorinated organic compounds), two bleaching technologies have emerged after 1990: ECF (Elemental Chlorine Free) and TCF (Total Chlorine Free). ECF has become the dominant technology (93% of the world bleached chemical pulp in 2012-AET, 2016) and modern ECF plants can achieve low levels of COC emissions. On the other hand, TCF is claimed to have a clear environmental advantage because no chlorine based chemicals are used. However, poor efficiency, high costs, low brightness stability and reduction of degree of polymerization are some of the reasons for the low acceptance of TCF. In this context, a TCF sequence [O O A (ZEO) (ZEO) P] has been developed and optimized to minimize ozone usage and to maintain pulp quality (Perrin, Pouyet, & Lachenal, 2015). Therefore, in this work, an early stage techno-economic analysis was performed to compare a traditional ECF sequence [O O D (EOP) D P] with the proposed TCF sequence for a greenfield bleached eucalyptus kraft pulp mill. Similar operating costs (ECF = U$ 467/AD tonne; TCF = U$ 470/AD tonne) and similar internal rate of return (ECF = 16.4%; TCF 16.3%) were obtained. Probabilistic analysis has shown that the price volatility of sodium hydroxide, and sodium chlorate have a significant impact on the probability distribution of internal rate of return (IRR). Despite its promising potential, the TCF bleaching has only been tested in laboratory scale and further scale up has to be performed to validate the proposed technology. However, the presented techno-economic economic analysis shows that the proposed TCF technology has a promising potential for industrial application.