A thermogravimetric study of the effect of pore volume-pore size distribution on the sulfation of calcined limestone

Ulerich, N.H.; O'Neill, E.P.; Keairns, D.L.

doi:10.1016/0040-6031(78)80074-4

Cited by 46 publications

(21 citation statements)

References 3 publications

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“…This might be because of the more limited extent of sintering to which the sorbent is exposed in the first case. Sintering results in an enlargement of the average particle pore size (Gullett and Bruce, 1987), and ultimately in an increase of the maximum degree of sulfation (Ulerich et al, 1978). This mechanism would also be consistent with the stronger sensitivity of the sulfation rate on particle size (related to stronger intraparticle diffusional resistances) observed under differential reaction conditions (Figure 10) compared to integral reaction conditions ( Figure 6).…”

Section: Apparent Kinetics Of Calcination and Sulfationsupporting

confidence: 71%

Comminution of limestone during batch fluidized‐bed calcination and sulfation

et al. 1997

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Batchwise fluidized-bed calcination and sulfation of a limestone were done to investigate particle comminution phenomena and their relation with parallel occurrence of reactions. Operating conditions of the bed were those typical of atmospheric bubbling fluidized-bed combustors. A general framework of comminution phenomena is outlined, which includes different types of fragmentations as well as attrition by abrasion. Comminution processes were characterized by following the modifications of bed sorbent particle-size distribution and the elutriation rates of fines throughout conversion. Mutual interactions between comminution processes and the progress of chemical reactions are assessed

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Section: Apparent Kinetics Of Calcination and Sulfationsupporting

confidence: 71%

Comminution of limestone during batch fluidized‐bed calcination and sulfation

et al. 1997

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“…By integrating over the pore size distribution, the macroscopic properties necessary to obtain the pseudo-steady state concentration profile in the pellet were obtained. Figure 11 shows the predictions of the model as compared to experimental data taken by Ulerich et al [51]. During the initial reaction period, the model closely fits the experimental data; however, at later times, the model is seen to overestimate solid conversion, …”

Section: E Lime Sulfation Modelsmentioning

confidence: 70%

“…[51] found that calcination in an atmosphere containing COg produced calcines with pores of larger diameters than those of calcines prepared in nitrogen. The overall porosity and surface area of the calcines prepared in the presence of COg were less than those produced in nitrogen as a result of the shift from finer to wider mouthed pores in the former.…”

Section: Evaluation Of Model Parametersmentioning

confidence: 99%

“…Ulerlch et [51] found that Increasing the mean pore diameter of CaO Increases the ultimate conversion. The SOg which arrives at the pore mouths can do one of two things.…”

Section: Evaluation Of Model Parametersmentioning

confidence: 99%

“…Equation (51) assumes that the gas phase thermal conductivity is negligibly small. WoodsIde and Messmer [55] proposed the following expression for systems that have a significant gas phase thermal conductivity;…”

Section: Evaluation Of Model Parametersmentioning

confidence: 99%

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Experimental gas-solid reaction kinetics of lime sulfation

Marsh

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The effect of pore structure on fluid‐solid reactions: Application to the SO₂‐lime reaction

1981

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The effect of varying pore structures on the kinetics of fluid-solid reactions is investigated through the random pore model developed in prior papers Perlmutter, 1980, 1981). By considering several idealized pore-size distributions it is shown that a solid having a uniform pore size is intrinsically less reactive than one possessing a pore-size distribution. For solids with bimodal pore size distributions optimal structures are shown to exist for which the reactivity is a maximum.Numerical solutions were obtained to the model equations for various values of the parameters characterizing the pore structure, the diffusion, and the chemical kinetics. The results show that the conversion-time behavior and the expected ultimate conversion can be very sensitive to variations in surface area and porosity for reactions accompanied by an increase in volume of the solid phase.These findings are in agreement with experimental literature on the SO 2-1' ime reaction (Ulerich e t al., 1978; Borgwardt and Harvey, 1972;Potter, 1969; Falkenberry and Slack, 1968) and the model is shown to fit the data of Borgwardt (1970), and of Coughlin (1974, 1976). It is seen that this reaction is diffusion controlled under the conditions of Hartman and Coughlin, in consonance with their own finding using the grain model, and a prior Pigford and Sliger (1973) interpretation. The temperature behavior of the diffusion coefficient in the product layer suggests the participation of an activated process, possibly a solid state diffusion step. SCOPEResults are reported on the effects of pore structure differences on the reaction behavior of solids, particularly in terms of variations in surface area, porosity, and dispersion in the pore size distribution. The analysis utilizes the random pore model developed by Perlmutter (1980,1981), representing a further development of these prior treatments.To demonstrate its use the model is applied to the data of Borgwardt (1970) and Coughlin (1974, 1976) on the lime-S02 reaction. The evaluation includes examination of the relative diffusional and kinetic resistances, of the incomplete conversions arising from pore closure in the solid, and of optimal pore distributions. Further comparisons are made with experimental reports of Ulerich et al. (1978), Borgwardt (1970), and Falkenberry and Slack (1968), to relate porestructure to the frequently observed differences in reaction behavior. CONCLUSIONS AND SIGNIFICANCEAn analysis of various simple pore size distributions shows that of all the pore structures with the same surface area and porosity, the one with pores of uniform size offers the least intrinsic reactivity. For bimodal pore size distributions optimal structures exist for which the reactivity is a maximum. Such results may offer guidance in the compaction of microporous solids by suggesting the desired pore structure.As expected, reactivity generally increases with surface area, but such variation can reduce ultimate conversion by more rapidly plugging pores a t the particle surface. Practical...

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A thermogravimetric study of the effect of pore volume-pore size distribution on the sulfation of calcined limestone

Cited by 46 publications

References 3 publications

Comminution of limestone during batch fluidized‐bed calcination and sulfation

Comminution of limestone during batch fluidized‐bed calcination and sulfation

Experimental gas-solid reaction kinetics of lime sulfation

The effect of pore structure on fluid‐solid reactions: Application to the SO₂‐lime reaction

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A thermogravimetric study of the effect of pore volume-pore size distribution on the sulfation of calcined limestone

Cited by 46 publications

References 3 publications

Comminution of limestone during batch fluidized‐bed calcination and sulfation

Comminution of limestone during batch fluidized‐bed calcination and sulfation

Experimental gas-solid reaction kinetics of lime sulfation

The effect of pore structure on fluid‐solid reactions: Application to the SO2‐lime reaction

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Product

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The effect of pore structure on fluid‐solid reactions: Application to the SO₂‐lime reaction