Combustion of coke with high ash content in fluidised beds

Mota, O.D.S.; Campos, J.B.L.M.

doi:10.1016/0009-2509(94)00242-j

Cited by 9 publications

(2 citation statements)

References 5 publications

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“…To determine the overall combustion resistance based on the experimental data, it is supposed that the combustion of the char particles only took place in the dense phase of the bed, as previously suggested by many authors. ,,− According to the same authors, it is also assumed that the oxygen concentration in this phase is uniform due to the high degree of bed agitation, while the oxygen concentration in the bubble size is obtained in accordance with the two phase theory of fluidization.…”

Section: Theoretical Mathematical Modelmentioning

confidence: 99%

Determination of Fluidized Bed Combustion Kinetic and Diffusive Data of Four Wood Chars from the Central Region of Portugal

Pereira

Pinho

2013

Energy Fuels

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The fluidized bed reactor is suitable for the combustion of biomass solid fuels because of its advantages in terms of pollution control. At the same time it is a useful laboratory tool to determine kinetic and diffusive combustion data in operating conditions similar to those found in industrial systems. Because of the heterogeneous nature of biomass, available information on its combustion is still limited. During the combustion of ligneous biomass, the burning of the solid carbonaceous residues formed after the initial steps of drying and volatiles release is the time-consuming step. In the present work, kinetic and diffusive data from the fluidized bed combustion of chars produced from four Portuguese wood speciesQuercus ilex (holm oak), Eucalyptus globulus (eucalyptus), Pinus pinaster (maritime pine), and Quercus suber (cork oak)were obtained in the 750–900 °C temperature range. Subsequently, activation energies and pre-exponential factors were calculated from the Arrhenius plot of the kinetic data. The obtained activation energies from 38 to 121 kJ/mol are coherent with results obtained for other wood chars and demonstrate that the fluidized bed technology is a fruitful and reliable methodology to achieve a collection of results of real and industrial interest. The main goal of the present work is to widen the information on the kinetic and diffusive data of wood chars in order to better understand the mechanisms of ligneous biomass combustion, and the data now published increases the range of available kinetic data on wood char combustion.

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Section: Theoretical Mathematical Modelmentioning

confidence: 99%

Determination of Fluidized Bed Combustion Kinetic and Diffusive Data of Four Wood Chars from the Central Region of Portugal

Pereira

Pinho

2013

Energy Fuels

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“…1.64 x 0.504 = 0.65 x Ffa + 0.52 x &a (6) 3.8 x 0.05 x 0.9 = 0.09 x Ffa + 0.16 x system. The effect of sorbent characteristics on attrition properties have been previously discussed in the case of an anthracite waste fired boiler [2], where a relatively minor amount of the ash flow from the boiler was derived from the sorbent particles.…”

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confidence: 99%

The measurement of flyash and bottom ash flow rates from a circulating fluidized bed boiler

Rozelle¹,

Pisupati

Scaroni

2000

Environ. Prog.

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The measurement of the flow rates offtyash and bottom ashfiom a Circulating Fluidized Bed (CFB) boiler has a number of uses. Among these are the requirements of boiler pe$rmance testing, the devehpment ofparticle population modeb for assessing key chemical interactions taking place in the combustion chamber, and the partitioning of key species between flyash and bottom ash. Identification of partitioning of key species betweenfl ash and bottom ash in key parameters of boih operation.Current methodsfor the computing of the flow rates of these ash streams include the measurement of the flow rates offeed solids, one ash stream flow rate, and infevence of the otherfiom a material balance. This is effort intensive and as such, not routinely feasible.Offered here is a methodfor computing the flow rates of ash streams through measurement of the solid feed rates to the system, and solving material balances around inorganic solid (total ash), cahium, and/ or su&, using these material balances as a simple set of simultaneous equations. This methodpermits the calculation of the ash stream flow rates without the direct measurement of either, and can bepracticed on a routine basi s. (com bustibles, calcium, sulficr) can t ' ead to improvements INTROMlcTONThere are several key parameters related to the performance of circulating fluidized bed (CFB) boilers that are influenced by the nature of the particles making u p the bed inventory. Among these are the amount and characteristics of bed particles that can be maintained in the combustion chamber, which can affect heat transfer 111, and ultimately heat rate. Another is the distribution and characteristics of sorbent particles within the system [21, which can affect sorbent consumption, and ultimately compliance costs.CFB boilers classify bed particles into flyash and bottom ash streams according to their gas flow resistance (size, density). As such, the ash split (the relative contributions of flyash and bottom ash to the composite ash flow from the boiler) will be impacted by the responses of feed particles to the chemical and physical stimuli encountered in the system 131. Lastly, there are interactions among bed particles and with the boiler that can adversely impact availability. Included among these are erosion of pressure parts and bed agglomeration.These considerations all relate to the transformations to which the feed particles are subjected during their residence in the system. Included among the transformations are combustion of fuel particles, calcination, sulfation, and reductive decomposition of sorbent particles, and attrition. Fuel, sorbent, and possibly inert bed particles are fed to a CFB boiler. The transformations exhibited by individual classes of particles have been elucidated in many cases. Among the results of relevant studies have been attrition of relatively low ash content coal char particles through percolative fragmentation [4,51. Similarly, the combustion of relatively high ash fuel particles has seen some attention [4,61 and a "shrinking core" me...

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Effective diffusivity of oxygen in the ash layer of Huadian oil shale semicoke

Huang

Zhang

et al. 2020

Front. Energy

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Combustion of coke with high ash content in fluidised beds

Cited by 9 publications

References 5 publications

Determination of Fluidized Bed Combustion Kinetic and Diffusive Data of Four Wood Chars from the Central Region of Portugal

Determination of Fluidized Bed Combustion Kinetic and Diffusive Data of Four Wood Chars from the Central Region of Portugal

The measurement of flyash and bottom ash flow rates from a circulating fluidized bed boiler

Effective diffusivity of oxygen in the ash layer of Huadian oil shale semicoke

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