Studies on slag deposit formation in pulverized-coal combustors. 4. Comparison of sticking behaviour of minerals and low-temperature and ASTM high-temperature coal ash on medium carbon steel substrates

Abbott, Murray F.; Austin, L.G.

doi:10.1016/0016-2361(82)90254-x

Cited by 16 publications

(2 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Cited are studies that establish that Fe 2+ phases such as Fe 1-x S and FeO tend to deposit more than Fe 3+ phases such as Fe 2 O 3 . These studies are confirmed by Abbott and Austin [4], who demonstrated that FeS has a higher propensity for deposition than Fe 2 O 3 , thereby arresting earlier speculations that Fe 2 O 3 initiates deposition.…”

Section: Introductionsupporting

confidence: 75%

Mechanisms of Pyrite Oxidation to Non-Slagging Species

Mitchell¹

2002

View full text Add to dashboard Cite

Executive SummaryA project was undertaken to characterize the oxidation of iron pyrite to the non-slagging species magnetite during pulverized coal combustion. The work was aimed at defining the pyrite transformations responsible for the higher slagging propensity of staged, low-NO x pulverized coal combustor burners. With such burners, coal is injected into a reducing environment. Consequently, the products of pyrite combustion become shifted from non-depositing, oxidized species such as Fe 3 O 4 to highly-depositing, reduced species such as FeO and Fe 1-x S, where x ranges from 0 to 0.125. The propensity for slagging can be minimized by the judicious redistribution of furnace air to maximize the oxide formation rate. This must be accomplished with minimal degradation of other aspects of boiler performance. To effect this, an understanding of the rate-limiting mechanisms of pyrite oxidation is required.The overall objectives of this project were to characterize the various mechanisms that control overall pyrite combustion rates and to synthesize the mechanisms into a pyrite combustion model. These objectives were achieved. The model produced has the capability of being incorporated into numerical codes developed to predict phenomena occurring in coal-fired boilers and furnaces. Such comprehensive codes can be used to formulate and test strategies for enhancing pyrite transformation rates that involve the minor adjustment of firing conditions. Ultimately, the benefit of this research project is intended to be an increase in the range of coals compatible with staged, low-NO x combustor retrofits. Project activities were aimed at identifying the mechanisms of pyrite combustion and quantifying their effects on the overall oxidation rate in order to formulate a model for pyrite conversion during coal combustion. Chemical and physical processes requiring characterization included pyrite intraparticle kinetics and mass transfer, gas-phase kinetics and mass transfer, and carbon matrix kinetics and mass transfer.In our efforts, time-resolved phase identifications of extraneous pyrite combustion products were used to determine a pyrite oxidation pathway. Combustion tests indicated that pyrite oxidizes through the following reaction sequence:Pyrite (FeS 2 ) is transformed to troilite (FeS), which is oxidized to wusite (FeO). The troilite-towusite transformation involves oxidation of an oxysulfide melt (Fe-S-O) melt to an iron-oxide melt (Fe-O) melt . Magnetite (Fe 3 O 4 , really, FeO·Fe 2 O 3 ) crystallizes from the oxide melt after complete melt oxidation. At high oxygen levels, crystallized magnetite is oxidized to hematite (Fe 2 O 3 ). Pyrrhotite (Fe 1-x S) is a product of FeS 2 decomposition that rapidly oxidizes as part of the 3 oxysulfide melt. Based on the above reaction sequence, a detailed chemical reaction mechanism for pyrite oxidation was developed. The mechanism was employed in models developed for the oxidation of extraneous pyrite particles and pyrite inclusions in coal.A key feature of the experimental app...

show abstract

Section: Introductionsupporting

confidence: 75%

Mechanisms of Pyrite Oxidation to Non-Slagging Species

Mitchell¹

2002

View full text Add to dashboard Cite

show abstract

“…MgO will suppress this mechanism, as it is reduced before SiO 2 . But the content of magnesia in coke ash and AUPC ash is extremely small, so the suppress of magnesia is negligible [29]. In the meantime, AUPC ash generates chemical reaction with coke ash to form some substance yoshiokaite (Ca(Al, Si) 2 O 4 ) and calcium iron oxide (CaFeO 2 ) that has a lower melting point than mullite.…”

Section: Effect Of Aupc On the Microscopic Morphology And The Carbon ...mentioning

confidence: 99%

Assessment on the effect of unburned pulverized coal on the properties of coke in blast furnace

Zhang

Wang

et al. 2020

Ironmaking & Steelmaking

View full text Add to dashboard Cite

The influence of anthracite unburned pulverized coal (AUPC) on the properties of coke at high temperature was studied using the thermogravimetric equipment. The micro morphology and mineral transformation were analyzed by scanning electron microscope with energy spectrum (SEM-EDS) and X-Ray diffracton (XRD) in present research. The results show that CO 2 preferentially reacts with AUPC, making SiC easier to form and wet the slag, which can enter pores and passivate gas from entering. Meanwhile, AUPC ash generates chemical reaction with coke ash to form yoshiokaite and calcium iron oxide that has a lower melting point than mullite and decrease the viscosity of ash slag, allowing SiO 2 to diffuse quicker to the coke surface and react to SiC, enabling quicker wetting. Besides, CaO may also catalyse gasification reactions. The ash wetting and catalysis of iron or CaO might shift inner-pore gasification to the outside and delaying the degradation of coke.

show abstract

Classification System for Ash Deposits Based on Sem analyses

Laursen

Frandsen

Impact of Mineral Impurities in Solid Fuel Combustion

View full text Add to dashboard Cite

Studies on slag deposit formation in pulverized-coal combustors. 4. Comparison of sticking behaviour of minerals and low-temperature and ASTM high-temperature coal ash on medium carbon steel substrates

Cited by 16 publications

References 6 publications

Mechanisms of Pyrite Oxidation to Non-Slagging Species

Mechanisms of Pyrite Oxidation to Non-Slagging Species

Assessment on the effect of unburned pulverized coal on the properties of coke in blast furnace

Classification System for Ash Deposits Based on Sem analyses

Contact Info

Product

Resources

About