Black liquor evaporator upgrades— life cycle cost analysis

Black liquor evaporation is generally the most energy intensive unit operation in a pulp and paper manufacturing facility. The black evaporators can represent third or more of total mill steam usage, followed by machine digester. Evaporator economy defined as mass required to evaporate water from (i.e., lb/lb kg/kg.) determined number effects an evaporator train system configuration. Older systems use four six effects, which are long tube vertical rising film type. Newer may be designed with seven even eight using falling forced circulation crystallization technology for high product solids. median age all North American 44 years. Roughly 25% current operating 54 years older. require periodic maintenance have higher risk unplanned downtime. Also, older chronic issues persistent vapor leaks, shell wall thinning, corrosion, plugged tubes. Often these worsen point requiring rebuild replacement. When considering age, technology, lower efficiency systems, major new warranted. intent this review state America present basic method determining whether installation warranted life cycle cost analysis (LCCA).