Technical Bulletin No. 0044: Factors Affecting Reduced Sulfur Emissions from the Kraft Recovery Furnace and Direct Contact Evaporator (AQTB)

The attached Technical Bulletin was prepared under the direction of Russell 0. Blosser, Leon Duncan, Joseph Megy, with assistance from Thomas Tucker, Michael Franklin and Hal B. H. Cooper of the National Council staff. It summarizes the results of a major staff study encompassing 26 kraft recovery furnace systems located on the West Coast and in the South. This study succeeded in defining the reduced sulfur emission control potential of numerous recovery furnaces by identifying the principal factors responsible in each case for increases above the minimal emission levels. The study was facilitated by (a) earlier NCASI and member mill development of the bromine coulometric titration method to a workable analytical tool, and process control instrument and (b) member mill cooperation in adjusting operating variables of numerous furnaces to meet the objectives of the study program. The study also clarified the role of the direct contact evaporator as a reduced sulfur emission source. While the bulk of this program has been completed, several phases remain under study, including (a) determination of emission levels for oxides of nitrogen and sulfur within the furnace and leaving the direct contact evaporator, (b) reduced sulfur emission levels in new furnaces operating without direct contact evaporation, and (c) influence of complete black liquor oxidation on organic sulfur emission at the direct contact evaporator. We hope that the findings of this study emphasizing the interrelation of furnace solids firing rate, air distribution and other operating variables will be brought to the attention of corporate mill engineering groups so that its full benefits can be realized in design of new recovery furnace systems and modification of existing furnace systems for maximum sulfur odor emission control.