Rate and diffusional study of the reaction of calcium oxide with sulfur dioxide

Marsh, Daniel Walter; Ulrichson, Dean L.

doi:10.1016/0009-2509(85)85104-6

Cited by 95 publications

(58 citation statements)

References 10 publications

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“…Current sulfation models (Hartman and Coughlin, 1976, 1978; Bhatia and Perlmutter, 1981a,b;Christman and Edgar, 1983;Bardakci, 1984;Marsh and Ulrichson, 1982; Ramachandran and Smith, 1977) describe the intraparticle diffusion of SO, through porous CaO, the intrinsic kinetics of the CaO + SO, reaction, the buildup of the product layer (CaSO,), the subsequent particle deactivation due to the relatively slow diffusion of SO, through the CaSO, to the unreacted CaO, and the ultimate termination of the reaction due to the plugging of the entire local porosity with the product deposits. These models are analyzed, and the results suggest an alternative deactivation mechanism: the plugging of the smallest pores and the associated loss in internal surface area.…”

Section: Scopementioning

confidence: 99%

Small pore closure and the deactivation of the limestone sulfation reaction

Simons

Garman

1986

AIChE Journal

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The sulfation model of Simons and Rawlins (1980) is extended to include the effect of product deposits. The model includes: 1. the plugging of the smallest pores and the subsequent loss in the internal surface area, 2. the diffusion of the SO, through the product deposits, and 3. the loss of intraparticle diffusion due to the complete plugging of the largest pores. It is shown that the plugging of the smallest pores is generally rate-controlling. G. A. Simons, A. R. GarmanPhysical Sciences Inc.Andover, MA 01810 SCOPECurrent sulfation models (Hartman and Coughlin, 1976, 1978; Bhatia and Perlmutter, 1981a,b;Christman and Edgar, 1983;Bardakci, 1984;Marsh and Ulrichson, 1982; Ramachandran and Smith, 1977) describe the intraparticle diffusion of SO, through porous CaO, the intrinsic kinetics of the CaO + SO, reaction, the buildup of the product layer (CaSO,), the subsequent particle deactivation due to the relatively slow diffusion of SO, through the CaSO, to the unreacted CaO, and the ultimate termination of the reaction due to the plugging of the entire local porosity with the product deposits. These models are analyzed, and the results suggest an alternative deactivation mechanism: the plugging of the smallest pores and the associated loss in internal surface area. A pore-plugging model is developed that is compatible with a treelike description of pore branching (Simons, 1982). Product deposits systematically fill pores of all sizes, with the result that the entire local porosity is eventually plugged. The model is validated with both SO, and H, S sorption data without invoking any adjustable parameters, such as the product layer diffusion coefficient. The model is readily available for parametric studies of the effect of sulfur concentration, particle size, porosity, internal surface area, and temperature on the calcium utilization achieved within specified time scales appropriate to various combustor or gasification devices. CONCLUSIONS AND SIGNIFICANCEThe sorption of H,S and SO, by a porous sorbent material (CaO) is described. The present model is distinct from previous models in its treatment of the role of the deposit layer, CaS for H, S sorption and CaSO, for SO, sorption. The development of this product layer induces the deactivation of the sorbent particle. Previous models attribute this deactivation to diffusion through the product layer, whereas the present model attributes this deactivation to the plugging of the smallest pores and the subsequent loss of internal surface area. The plugging of small pores is validated by comCorrespondence concerning this paper should be addressed to G. A. Simons.parison of the present theory to data on BET surface evolution with sulfur sorption. The time-dependent sorbent model is validated by extensive comparisons with SO, and H,S sorption data. The larger late time utilization of CaO by H, S and the faster late time utilization rate are explained solely on the basis of the smaller molar volume of the product, CaS. The plugging of small pores simply occurs at higher ...

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Section: Scopementioning

confidence: 99%

Small pore closure and the deactivation of the limestone sulfation reaction

Simons

Garman

1986

AIChE Journal

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“…The pelleting process may fracture CaO particles and thus increase surface area. This was also reported by Marsh and Ulrichson [13]. In a typical run, the pellet holder containing solid particles was first put into the diffusion cell.…”

Section: Methodsmentioning

confidence: 93%

Effective Diffusivities and Convective Coefficients for CaO‐CaSO₄ and CaO‐CaCl₂ Pellets

Akosman¹,

Zirekgür

2004

Chem Eng & Technol

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Diffusion and convective flow in the pores of pellets formed by compressing mixtures of calcined limestone and CaSO 4 /CaCl 2 powders have been studied experimentally by using the single pellet moment technique. The experiments were conducted in a diffusion cell by flowing nitrogen gas (carrier) through both faces of the pellet. Limestone powder was calcined in an atmosphere of N 2 at 800 C and mixed with CaSO 4 /CaCl 2 for diffusion experiments. Effective diffusivity of helium has been estimated by exposing the upper face of the pellet to a pulse of and matching the response peak on the lower face of the pellet with theoretical expressions. The values of the effective diffusivities increased with temperature, but decreased with increasing CaSO 4 /CaCl 2 content in the pellet. The convective flow contribution to the diffusion flux was found to increase with increasing pressure drop across the pellet.

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“…(6) applies for SO 2 concentrations up to 3,950 ppm with the value of c given in Eq. (5). The special condition of m 0 =0 will be analyzed further in the next section.…”

Section: Sulfation Model For Sorbent Clustersmentioning

confidence: 98%

“…A thin layer of Ca(OH) 2 was deposited onto a quartz glass plate to obtain a chemically controlled model to study the reaction rate and gas diffusion [5]. A small amount of Ca(OH) 2 was put into the 'net' sample-holder to give a variety of conditions to collect kinetic data from thermogravimetric data [6].…”

Section: Introductionmentioning

confidence: 99%

Sulfation diffusion model for SO2 capture on the T-T sorbent at moderate temperatures

Yang

You

et al. 2009

Korean J. Chem. Eng.

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A sulfation model was developed for dry flue gas desulfurization (FGD) at moderate temperatures to describe the reaction characteristics of the T-T sorbent clusters and the fine CaO particles that fall off the sorbent grains in a circulating fluidized bed (CFB) reactor. The cluster model describes the calcium conversion and reaction rate for various size sorbent clusters. The sulfation reaction is first order with respect to the SO 2 concentration above 973 K. The calcium conversion and reaction rate for the CaO particles were obtained by extrapolation. In the model for CaO particle, the reaction rate is linearly related to the calcium conversion and the SO 2 concentration in the rapid reaction stage and linearly related only with the calcium conversion after the product layer forms. The sulfation model accurately describes the sulfation of the T-T sorbent flowing through a CFB reactor.

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Rate and diffusional study of the reaction of calcium oxide with sulfur dioxide

Cited by 95 publications

References 10 publications

Small pore closure and the deactivation of the limestone sulfation reaction

Small pore closure and the deactivation of the limestone sulfation reaction

Effective Diffusivities and Convective Coefficients for CaO‐CaSO₄ and CaO‐CaCl₂ Pellets

Sulfation diffusion model for SO2 capture on the T-T sorbent at moderate temperatures

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Rate and diffusional study of the reaction of calcium oxide with sulfur dioxide

Cited by 95 publications

References 10 publications

Small pore closure and the deactivation of the limestone sulfation reaction

Small pore closure and the deactivation of the limestone sulfation reaction

Effective Diffusivities and Convective Coefficients for CaO‐CaSO4 and CaO‐CaCl2 Pellets

Sulfation diffusion model for SO2 capture on the T-T sorbent at moderate temperatures

Contact Info

Product

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Effective Diffusivities and Convective Coefficients for CaO‐CaSO₄ and CaO‐CaCl₂ Pellets