Ash transformation and deposit build-up during biomass suspension and grate firing: Full-scale experimental studies

Bashir, Muhammad Shafique; Jensen, Peter Arendt; Frandsen, Flemming; Wedel, Stig; Dam‐Johansen, Kim; Wadenbäck, Johan; Pedersen, Søren Thaaning

doi:10.1016/j.fuproc.2012.01.018

Cited by 67 publications

(91 citation statements)

References 23 publications

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“…A larger mixer, or homogenizer, known a drop tank [8] serves as the buffer for continuous operation. The slurry is then pumped at a low pressure into a hammer mill [13] to break agglomerates and avoid damage and blockages downstream. It is then brought to high pressure and conducted into the tower [15].…”

Section: Experimental Methodology Unit Design and Operationmentioning

confidence: 99%

“…The bonds between wall-borne clusters, however, need sustaining the stresses derived from the impact. If they are large enough, they may cause the breakage of the microstructure and re-entrainment in [11,12,13], or in [11,12,5,6,7] denoted as dry erosion or shedding, described later. Impacts develop a larger contact area when the droplets are deformable in stage [1].…”

Section: Deposition and Contact Mechanicsmentioning

confidence: 99%

“…Thus the particle impacts must be necessary to trigger it. This can be explained by (1) outer layers growing sufficiently so that gravity cause the detachment in stages [2,3,4,5,6,7] in Figure 15, or (2) breakage due to the impact of dry particles in [11,12,13] or wet droplets in [1,8,9]. In each case, re-entrainment occurs at very different time scales: (1) a long one occurs after deposition, aging, and shedding so that the size of the re-entrained cluster is related to the microstructure of the multilayer, and (2) a short one occurs as a result of impacts, and thus the size of the reentrained cluster is also related to the properties of the particles or droplets responsible.…”

Section: Origin Of the Disruptive Stressesmentioning

confidence: 99%

“…However, gravity driven mechanisms such as the detachment of large sections, or shedding, are significant in other fields such as combustion, where ash deposition, aging, and shedding are widely recognized phenomena. [11][12][13] The effect of particle impacts at higher particle inertia can also lead to resuspension. This has received little attention, not the least due to the difficulties in describing the microstructure at the wall.…”

Section: Introductionmentioning

confidence: 99%

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The role of wall deposition and re‐entrainment in swirl spray dryers

et al. 2015

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A new experimental method is outlined to study fouling in spray dryers and similar devices. In essence, it makes the deposits traceable so that one can quantify the material that comes off the walls, how long it remains there and how the deposits agglomerate with particles in the air. This paper investigates a countercurrent swirl spray dryer of detergent and provides sound evidence that fouling is a dynamic process: clusters form and break at the walls renewing an active layer of deposits. Remarkably, the wall generates >20% of the product and most of the large granules, and increases drastically the residence time of the powder. The assumptions of current numerical models are clearly invalid (i.e. particles rebound at the wall or deposit indefinitely). Several re-entrainment mechanisms and their times scales are identified in this work, and accordingly, a new general framework to describe fouling in spray dryers is proposed.

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Section: Experimental Methodology Unit Design and Operationmentioning

confidence: 99%

Section: Deposition and Contact Mechanicsmentioning

confidence: 99%

Section: Origin Of the Disruptive Stressesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The role of wall deposition and re‐entrainment in swirl spray dryers

et al. 2015

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“…Ash related operational problems, like slag and deposit creation in combustion devices and also fine particle emissions, are major concerns in biomass combustion that decreases the overall performance and may prevent an extension of the biomass resource base for heat and power production. The phenomenon of fouling is described in general terms by [32], and specifically for grate boilers by [33,34]. The mechanisms of slag formation in grate boilers are not covered to the same extent in the literary works, but [35] depict the present understanding.…”

Section: Introductionmentioning

confidence: 99%

Preparation and Characterization of Fuel Pellets from Corn Cob and Wheat Dust with Binder

El‐Sayed

Khairy

2017

IJEE

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A B S T R A C TThis study concentrates on pelletization of powdered corn cob and wheat dust with 40% Epoxy binder. Two cylindrical pellets of different sizes and a new hexagonal one were investigated in this work. By densification process, the bulk density increased 8-10 times, having its maximum value fora hexagonal shape (new shape). It was found that the compressive resistance, the water resistance and the impact resistance of the pellets were in general higher for pellets produced at higher pressure. It was found that due to the binder and pelletization, the fuel quality was enhanced compared to the raw biomass as: the moisture content decreased, both fixed carbon and carbon contents increased, ash content reduced, oxygen content decreased and higher heating value (H.H.V) increased. Scanning Electron Microscopy was used to identify the binding mechanism of biomass dust particles in pellets. Pelletization process had improved combustion characteristics compared to raw biomass as: high combustion temperature ranges [T_onset becomes lower and T_offset becomes higher], maximum weight loss rates decreased and reduced residues which leads to a higher combustion efficiency. The analysis of ash yields of combustion process was investigated. It was found that the fouling index (FI) and slagging index (SI) tendency of wheat dust pellets are higher than that of corn cob pellets.

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Modeling of ferric sulfate decomposition and sulfation of potassium chloride during grate‐firing of biomass

Jespersen

Frandsen

et al. 2013

AIChE Journal

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in Wiley Online Library (wileyonlinelibrary.com) Ferric sulfate is used as an additive in biomass combustion to convert the released potassium chloride to the less harmful potassium sulfate. The decomposition of ferric sulfate is studied in a fast heating rate thermogravimetric analyzer and a volumetric reaction model is proposed to describe the process. The yields of sulfur oxides from ferric sulfate decomposition under boiler conditions are investigated experimentally, revealing a distribution of approximately 40% SO 3 and 60% SO 2 . The ferric sulfate decomposition model is combined with a detailed kinetic model of gas-phase KCl sulfation and a model of K 2 SO 4 condensation to simulate the sulfation of KCl by ferric sulfate addition. The simulation results show good agreements with experiments conducted in a biomass grate-firing reactor. The results indicate that the SO 3 released from ferric sulfate decomposition is the main contributor to KCl sulfation and that the effectiveness of ferric sulfate addition is sensitive to the applied temperature conditions. V C 2013 American Institute of Chemical Engineers AIChE J, 59: [4314][4315][4316][4317][4318][4319][4320][4321][4322][4323][4324] 2013

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Ash transformation and deposit build-up during biomass suspension and grate firing: Full-scale experimental studies

Cited by 67 publications

References 23 publications

The role of wall deposition and re‐entrainment in swirl spray dryers

The role of wall deposition and re‐entrainment in swirl spray dryers

Preparation and Characterization of Fuel Pellets from Corn Cob and Wheat Dust with Binder

Modeling of ferric sulfate decomposition and sulfation of potassium chloride during grate‐firing of biomass

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