SHORT COMMUNICATION Alkali-Vapor Emission from PFBC of Illinois Coals

Lee, Sheldon H.D.; Teats, F.G.; Swift, W.M.; Banerjee, Debargha

doi:10.1080/00102209208947202

Cited by 27 publications

(7 citation statements)

References 2 publications

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“…The behavior of sodium species during coal combustion has been studied using both offline and online measurements. Offline analysis of fuel and ash compositions continues to be used for supporting and complementing online data [11][12][13][14][15]. These results reveal physical and chemical characteristics of sodium in the ash residues, which aids in understanding the transformations of sodium.…”

Section: Introductionmentioning

confidence: 94%

Measurement of atomic sodium release during pyrolysis and combustion of sodium-enriched Zhundong coal pellet

Wang

Liu

Whiddon

et al. 2017

Combustion and Flame

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Temporally resolved measurements of surface temperature, pellet diameter and proximal sodium concentration field are presented for the combustion of a high sodium coal (Zhundong) pellet. Non-resonant Planar laser-induced fluorescence (PLIF) was used to image the atomic sodium distribution around the coal pellet. The release profile of atomic sodium demonstrates three phases of combustion: (I) the devolatilization stage, (II) the char burnout stage, and (III) the ash reaction stage. Highest peak sodium concentration occurred in the char burnout stage, while the ash stage had the longest duration. The radial and axial sodium concentration decay during different phases of combustion was analyzed. During char burnout and ash stages, the maximum concentration of atomic sodium was near the pellet. In the devolatilization stage, burning of volatile-gases creates a high temperature region away from the surface of the coal pellet, which enhances the decomposition of sodium compounds in this region. Axial decay of atomic sodium concentration was governed by chemical reactions during all combustion stages. Calculation of atomic sodium flux (Na * flux) indicate that the smaller pellet releases atomic sodium more strongly in the devolatilization and char burnout stages than larger pellet. The mechanism of sodium release was inferred from the time derivatives of Na * flux , pellet-surface temperature (T) and pellet diameter (d). During the devolatilization stage, only Na * flux and T show variations, indicating that atomic sodium release is due to pyrolysis of the coal pellet. In the char burnout stage, time derivatives of the three parameters obey a common trend, indicating that the sodium release is associated with the burning of organic components in the pellet. In the ash reaction stage, T and d remain constant, indicating that the release of atomic sodium may be attributed to slow processes in the ash, likely vaporization of sodium from crystalline solids. A two-steps sodium release kinetics has been developed in this study and the simulation results agree well with measurements at three burning stages of coal pellet.

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Section: Introductionmentioning

confidence: 94%

Measurement of atomic sodium release during pyrolysis and combustion of sodium-enriched Zhundong coal pellet

Wang

Liu

Whiddon

et al. 2017

Combustion and Flame

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“…Unfortunately, little is known about the connections among fuel properties, combustion conditions, and alkali concentrations in PFBC exhausts. Based on the few laboratory studies in the literature (Bonn et aI., 1999;Greger et aI., 1996;Lee et al, 1993;Lee et al, 1992;Lee and Carls, 1990;Lee and Carls, 1989;Lee and Myles, 1987;Laatikainen et aI., 1993;Hippinen, et aI., 1992;Hulkkonen et aI., 1989), it appears that alkali concentrations are very sensitive to coal quality, particularly to coal rank and to the initial levels of alkali, chlorine, and sulfur, and also to the operating temperature. This paper describes the results of a modeling study undertaken to identify the major ways that coal quality affects alkali vapor emissions in PFBC exhaust streams.…”

Section: Introductionmentioning

confidence: 99%

Coal Quality Impacts on Alkali Vapor Emissions from Pressurized Fluidized Bed Coal Combustors

Niksa¹,

Helble

Haradac

et al. 2001

Combustion Science and Technology

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This paper describes a modeling study that was undertaken to identify the major ways that coal quality affects alkali vapor emissions in PFBC exhaust systems. The central premise is that the impact of coal quality can be reliably evaluated from kinetically based predictions of the concentrations of NaCI, KCI. S02. HCI, 02. and H 2 0 in the exhaust from the bubbling bed in combination with thermochemical equilibrium relations for conversion of alkali chlorides into alkali sulfate fumes in the freeboard. This hypothesis was implemented in a PFBC simulator that accounts for the major aspects of coal combustion and sulfur capture, and includes several mechanisms for alkali transformations,The model predicts a huge variation in exhaust Na vapor levels for different coals, ranging from the ppm-level with low rank coals to tens-of-ppb with hv bituminous coals for realistic levels of in-bed sulfur capture. This range is consistent with measured Na vapor emissions from two laboratory-scale systems. Hence. this approach exhibits the potential to predict Na-vapor emissions within useful quantitative tolerances at temperatures above 900°C with any coal type that contains sufficient chlorine to shift all alkali vapors into their chloride forms. It also demonstrates that the impact of all the coal properties that affect alkali vapor emissions can be expressed in terms of only two primary variables, the S02 and HCI concentrations in the exhaust after the alkali sulfate fume has formed. Whereas the essential connections among alkali vapor emissions and the concentrations of alkali vapors. S02' and HCI are not widely recognized. this study identified a complete set of test conditions that are essential elements for stringently evaluating predicted alkali levels. Simultaneous measurements of alkali vapors, S02, and HCI are the most important data requirements, together with the Na-, K-, and Cl-tevets in the test coals and accurate measurement of the temperature and cooling rate at the sampling point.

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“…Several different methods are suggested in the literature: [3][4][5][6][7][8][9][10][11] surface ionization ͑SI͒, 3 molecular beam mass spectroscopy, 4,5 plasma excited alkali resonance line spectroscopy, 6,7 flame emission excimer laser induced fragmentation fluorescence, 8,9 fiber optical alkali monitor, 10 and a sorber bed method. 11 Most methods have been reviewed by Monkhouse. 12 All are associated with one or more of the problems of complicated calibration, difficulties in quantification, high service requirements, or expensive equipment.…”

Section: Introductionmentioning

confidence: 99%

Principle, calibration, and application of the in situ alkali chloride monitor

Forsberg

Broström

Backman

et al. 2009

Review of Scientific Instruments

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The extended use of biomass for heat and power production has caused increased operational problems with fouling and high-temperature corrosion in boilers. These problems are mainly related to the presence of alkali chlorides (KCl and NaCl) at high concentrations in the flue gas. The in situ alkali chloride monitor (IACM) was developed by Vattenfall Research and Development AB for measuring the alkali chloride concentration in hot flue gases (less than or approximately 650 degrees C). The measurement technique is based on molecular differential absorption spectroscopy in the UV range. Simultaneous measurement of SO(2) concentration is also possible. The measuring range is 1-50 ppm for the sum of KCl and NaCl concentrations and 4-750 ppm for SO(2). This paper describes the principle of the IACM as well as its calibration. Furthermore, an example of its application in an industrial boiler is given.

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SHORT COMMUNICATION Alkali-Vapor Emission from PFBC of Illinois Coals

Cited by 27 publications

References 2 publications

Measurement of atomic sodium release during pyrolysis and combustion of sodium-enriched Zhundong coal pellet

Measurement of atomic sodium release during pyrolysis and combustion of sodium-enriched Zhundong coal pellet

Coal Quality Impacts on Alkali Vapor Emissions from Pressurized Fluidized Bed Coal Combustors

Principle, calibration, and application of the in situ alkali chloride monitor

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