Studies on combustion of carbon particles in flames and fluidized beds

Yagi, Shuhei; Kunii, Daizō

doi:10.1016/s0082-0784(55)80033-1

Cited by 147 publications

(83 citation statements)

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“…The standard SCM (Yagi and Kunii, 1955) is able to account for three mechanisms which determine the overall rate of conversion of the solid reactant. These mechanisms are: (i) mass transfer from the ambient fluid through the fluid film surrounding the particle; (ii) diffusion through the inert product layer left behind as the core shrinks; and (iii) chemical reaction at the surface of the unreacted core.…”

Section: Shrinking Core Modelsmentioning

confidence: 99%

“…This intra-particle modelling is usually done by means of the shrinking core model (SCM) or one of its variants. In the standard SCM (Yagi and Kunii, 1955), each particle is assumed to be a sphere of initially unreacted material. Reaction takes place on the surface of the sphere and then progresses inwards, such that the core of unreacted material shrinks and leaves behind a layer of inert, permeable, solid product.…”

Section: Introductionmentioning

confidence: 99%

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Models for apparent reaction kinetics in heap leaching: A new semi-empirical approach and its comparison to shrinking core and other particle-scale models

et al. 2016

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Particle-scale effects are critically important to the performance of heap leaching operations. In a heap-scale simulation, the transport of fluid phases and reactive species external to the ore particles might be modelled with thousands of grid elements by the finite volume or finite element method. The inter-and intra-particle diffusions and reactions are usually parametrised by a deterministic model, such as the shrinking core model (SCM), that translates the external conditions into an effective product extraction rate. However, the rate equation takes the form of an implicit or partial differential equation for all but the simplest models and kinetic regimes, becoming expensive to solve on large grids. We instead propose an economical, easily calibrated semi-empirical approach in which the dependencies on external conditions and the current state of the ore are considered to be mathematically separable. We show that the standard SCM does not suffer greatly from this approximation even when there is a mixed control regime with nonlinear kinetics. The dependency on the state of the ore is derived empirically, inherently capturing heterogeneous features and cluster-scale effects. We demonstrate that this method scales correctly when fitted to data from physical column leaching experiments.

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Section: Shrinking Core Modelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Models for apparent reaction kinetics in heap leaching: A new semi-empirical approach and its comparison to shrinking core and other particle-scale models

et al. 2016

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“…As reported in the literature among fluidparticle reaction theories [24][25][26][27], one model (and several variants) has been successfully used: the Shrinking Core Model (SCM), originally developed by Yagi and Kunii [24,25]. On the scale of one particle (Fig.…”

Section: Chemical Reaction On the Particles: An Obstacle To Gas Progrmentioning

confidence: 99%

Development of Reactive Barrier Polymers against Corrosion for the Oil and Gas Industry: From Formulation to Qualification through the Development of Predictive Multiphysics Modeling

Lefebvre

Pasquier

Gonzalez

et al. 2015

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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-Corrosion is a key issue for operators in the oil and gas industry since production fluids contain some water and both CO 2 and H 2 S acid gases. In this context, this paper illustrates the development of a reactive barrier polymer against corrosion by H 2 S of offshore flexible pipes. The role of this reactive material, called anti-H 2 S material, is to avoid H 2 S reaching the structural steel layers of the flexible pipe during the whole service life of the structure, usually 20 years, and hence to place the steel layers in a sweet service environment. Placed between the existing pressure sheath and the steel layers, the anti-H 2 S material has the ability to neutralize H 2 S during its diffusion within the material. The neutralization is ensured by an irreversible chemical reaction on reactive components that are dispersed in the material. The raw material selection is based on both accurate requirements for their use in a flexible pipe and expected performances in a sour service environment over a long period of time. Some laboratory qualifications and experimental techniques are used to qualify the behavior of the material and build the material database. A dedicated multiphysics model is developed based on the coupling of permeation mechanisms and gas-solid reactions. Qualification of both the material and the model is performed thanks to middle-scale and full-scale tests conducted in representative sour service conditions. Résumé -Développement de matériaux barrières réactifs contre la corrosion pour l'industrie pétrolière : de la formulation à la qualification industrielle en passant par le développement de modèles multiphysiques prédictifs -La corrosion liée à la présence de gaz acides tels que CO 2 et H 2 S en présence d'eau dans les effluents pétroliers est un enjeu majeur pour les opérateurs pétroliers. C'est dans ce contexte que cet article décrit le développement d'un matériau barrière réactif permettant de limiter la corrosion par H 2 S des flexibles offshore. Le rôle de ce matériau barrière, appelé matériau anti-H 2 S, consiste à empêcher l'H 2 S d'atteindre les éléments métalliques structuraux du flexible pendant toute sa durée de vie, généralement 20 ans. De cette manière, les éléments métalliques bénéficient d'un environnement « sweet service » , peu agressif en terme de corrosion. Placé entre l'actuelle gaine de pression et les éléments métalliques, le matériau anti-H 2 S a la faculté de pouvoir neutraliser l'H 2 S pendant sa diffusion au sein même du matériau. La neutralisation est assurée par une réaction chimique irréversible sur des charges réactives dispersées au sein du matériau. Les matières premières constitutives de ce matériau sont sélectionnées selon leur performance en milieu fortement corrosif « sour service », tout en garantissant leur compatibilité avec les applications flexibles offshore. La qualification du matériau à l'échelle du laboratoire est décrite ainsi que les techniques qui nous permettent d'alimenter la base de données nécessaire à l'identification d'un mo...

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“…Consequently, it was necessary to consider the effect of both film diffusion and ash layer diffusion in selecting an appropriate model for a pellet core. The two effects are accounted for in the following expressions provided by Levenspiel: 49 t total = t film alone + t ash alone (14) t total = τ film X + τ ash [1 -3(1 -X) 2/3 + 2(1 -X)]…”

Section: Development Of a Model For The Absorption Processmentioning

confidence: 99%

Engineering a New Material for Hot Gas Cleanup

Wheelock¹,

Doraiswamy²,

Constant³

2003

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The overall purpose of this project was to develop a superior, regenerable, calcium-based sorbent for desulfurizing hot coal gas with the sorbent being in the form of small pellets made with a layered structure such that each pellet consists of a highly reactive lime core enclosed within a porous protective shell of strong but relatively inert material. The sorbent can be very useful for hot gas cleanup in advanced power generation systems where problems have been encountered with presently available materials.An economical method of preparing the desired material was demonstrated with a laboratory-scale revolving drum pelletizer. Core-in-shell pellets were produced by first pelletizing powdered limestone or other calcium-bearing material to make the pellet cores, and then the cores were coated with a mixture of powdered alumina and limestone to make the shells.The core-in-shell pellets were subsequently calcined at 1373 K (1100°C) to sinter the shell material and convert CaCO 3 to CaO. The resulting product was shown to be highly reactive and a very good sorbent for H 2 S at temperatures in the range of 1113 to 1193 K (840 to 920°C) which corresponds well with the outlet temperatures of some coal gasifiers. The product was also shown to be both strong and attrition resistant, and that it can be regenerated by a cyclic oxidation and reduction process.A preliminary evaluation of the material showed that while it was capable of withstanding repeated sulfidation and regeneration, the reactivity of the sorbent tended to decline iv with usage due to CaO sintering. Also it was found that the compressive strength of the shell material depends on the relative proportions of alumina and limestone as well as their particle size distributions. Therefore, an extensive study of formulation and preparation conditions was conducted to improve the performance of both the core and shell materials. It was subsequently determined that MgO tends to stabilize the high-temperature reactivity of CaO. Therefore, a sorbent prepared from dolomite withstands the effects of repeated sulfidation and regeneration better than one prepared from limestone. It was also determined that both the compressive strength and attrition resistance of core-in-shell pellets depend on shell thickness and that the compressive strength can be improved by reducing both the particle size and amount of limestone in the shell preparation mixture.A semiempirical model was also found which seems to adequately represent the absorption process. This model can be used for analyzing and predicting sorbent performance, and, therefore, it can provide guidance for any additional development which may be required.

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Studies on combustion of carbon particles in flames and fluidized beds

Cited by 147 publications

References 1 publication

Models for apparent reaction kinetics in heap leaching: A new semi-empirical approach and its comparison to shrinking core and other particle-scale models

Models for apparent reaction kinetics in heap leaching: A new semi-empirical approach and its comparison to shrinking core and other particle-scale models

Development of Reactive Barrier Polymers against Corrosion for the Oil and Gas Industry: From Formulation to Qualification through the Development of Predictive Multiphysics Modeling

Engineering a New Material for Hot Gas Cleanup

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