Technical Bulletin No. 0080: Identification and Control of Total Reduced Sulfur Gaseous Emissions from the Lime Kiln Stack (AQTB)

The attached technical bulletin describes the findings of extensive field and laboratory studies conducted by the National Council staff to identify factors related to reduce sulfur emissions from lime kilns in the kraft recovery process.  During the conduct of these studies, which have spanned a period of approximately three years, several factors have been identified which affect the reduced sulfur emissions from lime kilns. In summary these are (1) effectiveness of the lime mud washing system in removing residual sulfides; (2) maintenance of proper combustion conditions in the kiln, and (3) use of a sulfide-free water in the particulate emission control device. Information on the size of mud washing equipment which was found to accomplish sulfide removal from lime mud consistent with the lowest kiln TRS emissions being observed is included as a part of the bulletin. An extensive field study is currently underway which is designed to relate (1) various causticizing system design and operating practices, and (2) lime mud washing system component design and operation to residual sulfide in lime mud. The bulletin contains a section on the status of sulfide oxidation in lime mud as a possible emission control process. This approach is under investigation at two mills as an alternate to improved mud washing as a means of sulfide level control in lime mud. The study should therefore define the possibility of lime mud oxidation serving as an alternate emission control technology. Its results will be reported at a later date.