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Columbia, MD, United States

Singbeil D.L.,FPlnnovations | Frederick L.,FPlnnovations | Keiser J.R.,Oak Ridge National Laboratory | Sandy Sharp W.B.A.,SharpConsultant
2013 PEERS Conference, Co-located with the 2013 International Bioenergy and Bioproducts Conference | Year: 2013

A laboratory-based program was designed to evaluate candidate alloys for superheaters operating at temperatures substantially higher than currently used in practice for biomass and chemical recovery boilers. However, the data is also applicable to superheaters operating in very corrosive conditions at lower temperatures. Alloys are ranked according to their performance in simulated environments. Copyright © (2013) by the TAPPI Press. Source


Keiser J.R.,Oak Ridge National Laboratory | Sandy Sharp W.B.A.,SharpConsultant | Singbeil D.L.,FPlnnovations
2013 PEERS Conference, Co-located with the 2013 International Bioenergy and Bioproducts Conference | Year: 2013

Operating superheater tubes of biomass-fired boilers at considerably higher temperatures than can be tolerated by commonly used structural materials could improve boiler efficiency. However, corrosion of the superheater tubes promoted by interaction with the relatively low melting point deposits that accumulate on the tubes becomes a major issue. The objective of this task was to use field exposures to determine if there are materials acceptable for use as superheater tubes that can operate at temperatures at least 100 Celsius degrees above the current maximum superheater temperature. Corrosion probes containing multiple specimens of nine different alloys were exposed for at least 2,000 hours in the superheater area of three biomass boilers where the deposits were determined to be enriched in potassium or chlorine. Similar specimens were also exposed in a boiler co-firing coal and wood. For the probes, specimen temperatures ranged from a low of less than 400°C to temperatures above 600°C for all but one case. Following exposure, a section was taken from each specimen and examined using light microscopy and scanning electron microscopy. Results of the examination of these specimens showed some alloys performed considerably better than others, but the corrosion resistance could not be related to chromium or molybdenum content of the alloys. Copyright © (2013) by the TAPPI Press. Source


Keiser J.R.,Oak Ridge National Laboratory | Sharp W.B.A.,SharpConsultant | Singbeil D.A.,Pulp and Paper Research Institute of Canada | Frederick L.A.,Pulp and Paper Research Institute of Canada | Clemmons C.,Meadwestvaco Corporation
Tappi Journal | Year: 2013

One method to significantly improve the efficiency of biomass-fired boilers is to increase the temperature and pressure of the steam generated. However, this requires operating the superheater tubes at considerably higher temperatures than can be tolerated by conventional structural materials. The limiting temperature for conventional materials is primarily determined by corrosion of the superheater tubes that is promoted by interaction with the relatively low melting point deposits that accumulate on the tubes. An air-cooled deposit probe was used to collect samples of the deposits that accumulated on tubes in the superheater area of a recovery boiler in a mill processing primarily hardwood. These deposits were found to be enriched in potassium. Subsequently, a corrosion probe containing multiple samples of nine different alloys was exposed for 2000 h in the same location of the superheater area of the same recovery boiler. The temperature of samples in the probe ranged from a low of about 400°C (752°F) to temperatures above 620°C (1148°F), compared to the boiler's estimated maximum tube temperature of 470°C (878°F). Following exposure, sections were taken from each of the 30 samples and examined using light microscopy and scanning electron microscopy. Results of the examination of these samples showed significant differences among the corrosion rates at temperatures 100°C above the current upper superheater tube temperature. A brief comparison is made to data from a parallel laboratory study. Application: This paper provides guidance on the selection of an alternate material for the highest temperature portion of the superheater tubes. Source


Sharp W.B.A.,SharpConsultant | Singbeil D.L.,Pulp and Paper Research Institute of Canada | Keiser Jr. J.R.,Oak Ridge National Laboratory
NACE - International Corrosion Conference Series | Year: 2012

About 90% of the world's bioenergy is produced by burning renewable biomass fuels. Low-cost biomass fuels such as agricultural wastes typically contain more alkali metals and chlorine than conventional fuels. Although the efficiency of a boiler's steam cycle can be increased by raising its maximum steam temperature, alkali metals and chlorine released in biofuel boilers cause accelerated corrosion and fouling at high superheater steam temperatures. Most alloys that resist high temperature corrosion protect themselves with a surface layer of Cr 2O 3. However, this Cr 2O 3 can be fluxed away by reactions that form alkali chromates or volatilized as chromic acid. This paper reviews recent research on superheater corrosion mechanisms and superheater alloy performance in biomass boilers firing black liquor, biomass fuels, blends of biomass with fossil fuels and municipal waste. Source


Sharp W.B.A.S.,SharpConsultant | Kiefer L.A.,Bluewave Microbics
Tappi Journal | Year: 2015

This introduction to microbiologically influenced corrosion (MIC) describes how bacteria can cause MIC where inadequate disinfection of mill water or white water allows biofilms to grow on metal surfaces. Although planktonic bacteria (that float in solution) rarely cause corrosion, sessile bacteria (that adhere to surfaces) can produce corrosive chemicals or promote under-deposit corrosion. The diagnosis of MIC requires knowledge not only of corrosion processes, but also of microbiology, water treatment, and plant operations. Although the presence of bacteria does not prove that the corrosion was caused by MIC, factors such as the presence in the corroded area of bacteria that can cause MIC, of chemical indicators of MIC, of features of the corrosion damage that are characteristic of MIC, and recent operational changes that could have enhanced the activity of microorganisms can combine to provide compelling evidence. Because of the complexity of mill water environments, test data must be reviewed with care because of the possibility that other components of the water could have interfered with the analytical results. Application: Although MIC is one of the most difficult types of corrosion to diagnose, the characteristic features and tests described in this paper can help identify it as the cause of corrosion damage in cooling water or white water systems. Source

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