Factors influencing the transformation of minerals during pulverized coal combustion

Helble, J.J.; Srinivasachar, S.; Boni, A.A.

doi:10.1016/0360-1285(90)90036-3

Cited by 78 publications

(59 citation statements)

References 16 publications

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“…Table 5 shows fraction >200 mesh of pulverized torrefied material at various mass losses. The table indicates that above 8.4% mass loss, after grinding the fraction of <200 mesh is >70%, which is consistent with of the typical coal power plant requirements (Helble et al, 1990).…”

Section: Sizing Distributionsupporting

confidence: 80%

Properties of Torrefied U.S. Waste Blends

Zinchik

Kolapkar

et al. 2018

Front. Energy Res.

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Power generation facilities in the U.S. are looking for a potential renewable fuel that is sustainable, low-cost, complies with environmental regulation standards and is a drop-in fuel in the existing infrastructure. Although torrefied woody biomass, meets most of these requirements, its high cost, due to the use of woody biomass, prevented its commercialization. Industrial waste blends, which are also mostly renewable, are suitable feedstock for torrefaction, and can be an economically viable solution, thus may prolong the life of some of the existing coal power plants in the U.S. This paper focuses on the torrefaction dynamics of paper fiber-plastic waste blend of 60% fiber and 40% plastic and the characterization of its torrefied product as a function of extent of reaction (denoted by mass loss). Two forms of the blend are used, one is un-densified and the other is in the form of pellets with three times the density of the un-densified material. Torrefaction of these blends was conducted at 300 • C in the mass loss range of 0-51%. The torrefied product was characterized by moisture content, grindability, particle size distribution, energy content, molecular functional structure, and chlorine content. It was shown that although torrefaction dynamics is of the two forms differs significantly from each other, their properties and composition depend on the mass loss. Fiber content was shown to decrease relative to plastic upon the extent of torrefaction. Further, the torrefied product demonstrates a similar grinding behavior to Powder River Basin (PRB) coal. Upon grinding the fiber was concentrated in the smaller size fractions, while the plastic was concentrated in the larger size fractions.

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Section: Sizing Distributionsupporting

confidence: 80%

Properties of Torrefied U.S. Waste Blends

Zinchik

Kolapkar

et al. 2018

Front. Energy Res.

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“…Mineral matter present in coal may occur as minerals, mineraloids and as organically-associated inorganic elements [1], which may interact in different ways during combustion [2][3][4][5][6][7], coking [8] and gasification processes [9][10][11][12][13]. A distinction is sometimes made between "included minerals" and "excluded minerals", especially in pulverized fuel combustion.…”

Section: Introductionmentioning

confidence: 99%

Behaviour of coal mineral matter in sintering and slagging of ash during the gasification process

Matjie

French

Ward

et al. 2011

Fuel Processing Technology

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The mineral matter in typical feed coals used in South African gasification processes and the ash derived from gasifying such coals have been investigated using a variety of mineralogical, chemical and electron microscope techniques. The mineral matter in the feed coals consists mainly of kaolinite, with minor proportions of quartz, illite, dolomite, calcite and pyrite plus traces of rutile and phosphate minerals. The calcite and dolomite occur in veins within the vitrinite macerals, and are concentrated in the floats fraction after density separation. Some Ca and Ti also appear to be present as inorganic elements associated with the organic matter. Electron microscope studies show that the gasification ash is typically made up of partly altered fragments of non-coal rock, bonded together by a slag-like material containing anorthite and mullite crystals and iron oxide particles, with interstitial vesicular glass of calcic to iron-rich composition. Ash formation and characteristics thus appear to be controlled by reactions at the particle scale, allowing the different types of particles within the feed coal to interact with each other in a manner controlled mainly by the modes of mineral occurrence. Integration of such techniques provides an improved basis for evaluating ash-forming processes, based on quantitative phase identification, bulk and particle chemistry, and the geometric forms in which the different phases occur.

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“…This lowers the viscosity and temperature at which a significantly less viscous slag melt is formed. It is further noted that compositions of Fe2O3> 10 wt% increase the slagging risk as the ash viscosities can be lowered significantly [25,34]. This would explain why the GEr, CAn and USi coals all exhibit medium and high slagging potentials, characterised by their respective ash viscosities (SR, EQ-3).…”

Section: Mass Balancementioning

confidence: 97%

An experimental study of ash behaviour and the potential fate of ZnO/Zn in the Co-combustion of pulverised South African coal and waste tyre rubber

Singh

Nimmo

Williams

2013

Fuel

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A Novel combustion application utilising waste tyre rubber (WTR) as a secondary fuel in pulverised coal power plants is presented. Co-combustion of a South African coal (SAf) with WTR at the fuel fractions (FF) 4.1%, 14.1% and 19.7% along with the pure firing of WTR was conducted in an 80 kWth combustion test facility (CTF). This study assessed the potential slagging and fouling behaviour of the resultant ashes produced from co-firing SAf/WTR and pure fired WTR. XRF and ICP/OES analysis of the co-fired SAf/WTR and pure fired WTR ashes revealed a high composition of acidic oxides. Based on the fusibility indices (B/A, RS, SR, F and Fu) it was determined that co-fired SAf/WTR and pure fired WTR ashes carry a low risk of slagging and fouling. ZnO is incorporated in the manufacturing of tyres as a compounding additive. ZnO is present within raw WTR, posing the question as to its fate during combustion. In this study ash collected and analysed from the pure fired WTR and co-fired SAf/WTR exhibited lower levels of Zn than anticipated. It is suggested that ZnO remains in the vapour phase within the CTF at temperatures >1200 o C. Experimental analysis found Zn enrichment at lower temperatures was not significant within the fly ash collected by the cyclone trap or ash deposits collected from the water cooled sections of the CTF. This suggests that Zn could be forming a submicron aerosol. It is further noted that ZnO/Zn is not likely to contribute significantly in the slagging/fouling mechanisms, due to its volatile nature. However this present study highlights the need for further experimental assessment of co-firing SAf/WTR required prior to any industrial application.

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Factors influencing the transformation of minerals during pulverized coal combustion

Cited by 78 publications

References 16 publications

Properties of Torrefied U.S. Waste Blends

Properties of Torrefied U.S. Waste Blends

Behaviour of coal mineral matter in sintering and slagging of ash during the gasification process

An experimental study of ash behaviour and the potential fate of ZnO/Zn in the Co-combustion of pulverised South African coal and waste tyre rubber

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