Corrosion in lower furnace of kraft recovery boilers--in-situ characterization of corrosive environments.APPLICATION: Fireside corrosion in kraft recovery boilers Recovery boiler is the part of Kraft process of pulping where chemicals for white liquor are recovered and reformed from black liquor. In the process lignin of the wood, bound in black liquor at this phase, is burned and heat generated. in lower and mid furnace is a continuing problem in the pulp and paper industry The global pulp and paper industry is dominated by North American (United States, Canada), northern European (Finland, Sweden) and East Asian countries (such as Japan). Australasia and Latin America also have significant pulp and paper industries. . This paper describes some of the reasons for higher corrosion in localized areas of waterwall in the lower furnace. Findings from this study can be used to mitigate some of the lower furnace corrosion problems by making changes in operating conditions to avoid intentional or unintentional spray of black liquor Black liquor is a byproduct of the Kraft process, (also known as Kraft pulping or sulfate process) during the production of paper pulp. Wood is decomposed into cellulose fibers (from which paper is made), hemicellulose and lignin fragments. on waterwalls. Fireside corrosion in kraft recovery boilers is a continuing problem, especially in the boilers using carbon steel tubes in lower furnace areas. Certain areas in the lower furnace of kraft recovery boilers consistently have higher corrosion rates than the nearby areas. As the tube material in these areas is the same, differences in the corrosion rate suggest that the local environmental conditions in the two areas are different. Corrosive corrosive /cor·ro·sive/ (kor-o´siv) producing gradual destruction, as of a metal by electrochemical reaction or of the tissues by the action of a strong acid or alkali; an agent that so acts. environments were characterized in a kraft recovery boiler, which had well-defined areas with high corrosion rates and low corrosion rates. Three important variables, tube surface temperature, gas composition at the waterwall surface, and smelt composition were monitored in the selected areas. Recovery boiler gases were analyzed using an on-line gas chromatograph gas chromatograph n. An instrument used in gas chromatography to separate a sample of a volatile substance into its components. . Temperature and smelt did not have any effect on differences in the corrosion rate in the two areas. Smelt was not present in either the low or the high corrosion rate areas. Gas compositions were found to be significantly different in the high corrosion area compared to the low corrosion area. This study demonstrated that direct pyrolysis py·rol·y·sis n. Decomposition or transformation of a chemical compound caused by heat. pyrolysis (pīrol´isis), n of black liquor on the waterwall surface results in significantly higher concentrations of sulfur containing gases in the high corrosion areas, leading to higher corrosion rates of the waterwall. View this paper online at http://www.tappi.org/index.asp?pid=28651 Preet M. Singh is with the School of Materials, Science & Engineering, Georgia Institute of Technology Georgia Institute of Technology, in Atlanta, Ga.; coeducational; state supported; chartered 1885, opened 1888. It is a member school in the university system of Georgia. Significant among its facilities and programs are the Frank H. , Atlanta; Safaa J. Al-Hassan, Sloane Stalder, and Greg Fonder are with the Institute of Paper Science and Technology, 500 10th Street., NW, Atlanta, GA, 30318. Email Singh at preet.singh@ipst.edu. |
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