Sintering of nascent calcium oxide

Borgwardt, Robert H.

doi:10.1016/0009-2509(89)85232-7

Cited by 284 publications

(283 citation statements)

References 16 publications

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“…under the oxy CFB calciner was selected. CO 2 is a very effective sintering agent [64], so it might affect the internal pore structure available for sulphation, depending on the time of exposure and the temperature. However, as the sorbent in a CaL will have undergone several cycles of calcination carbonation, the effect of further sintering will be negligible.…”

Section: Resultsmentioning

confidence: 99%

Modelling of the kinetics of sulphation of CaO particles under CaL reactor conditions

Cordero

Alonso

2015

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Furthermore it is demonstrated that the number of calcination carbonation cycles changes the sulphation patterns of the CaO from heterogeneous to homogeneous in all the limestones tested. For 50 carbonation calcination cycles and for particle sizes below 200 µm, the sulphation pattern is in all cases homogeneous. The sulphation rates were found to be first order with respect to SO 2 , and zero with respect to CO 2 . Steam was observed to have a positive effect only in the diffusion through the product layer controlled regime, as it leads to an improvement in the sulfation rates and effectiveness of the sorbent. Most of the experimental results of sulfation of highly cycled sorbents under all conditions can be fitted by means of the Random Pore Model (RPM) assuming that the kinetics and diffusion through the product layer of the CaSO 4 are the controlling regimes.

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Section: Resultsmentioning

confidence: 99%

Modelling of the kinetics of sulphation of CaO particles under CaL reactor conditions

Cordero

Alonso

2015

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“…Second, in the present study we prepared our CaO by calcining Carrara marble at 1100°C for 16 h. There exists a substantial body of literature dealing with the effects of calcination temperature, starting carbonate material and grain size, and various other processes (e.g. sintering) on the nature of the final CaO product [13,14,41,46,112]. For example, the rate of hydration is slower for dead-burnt lime (calcined at [1600°C) than for ''normal'' CaO, prepared at\1200°C [43].…”

Section: Applicability To Casing Expansion and Suggestions For Futurementioning

confidence: 99%

Reaction-driven casing expansion: potential for wellbore leakage mitigation

2017

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It is generally challenging to predict the postabandonment behaviour and integrity of wellbores. Leakage is, moreover, difficult to mitigate, particularly between the steel casing and outer cement sheath. Radially expanding the casing with some form of internal plug, thereby closing annular voids and fractures around it, offers a possible solution to both issues. However, such expansion requires development of substantial internal stresses. Chemical reactions that involve a solid volume increase and produce a force of crystallisation (FoC), such as CaO hydration, offer obvious potential. However, while thermodynamically capable of producing stresses in the GPa range, the maximum stress obtainable by CaO hydration has not been validated or determined experimentally. Here, we report uniaxial compaction/expansion experiments performed in an oedometer-type apparatus on precompacted CaO powder, at 65°C and at atmospheric pore fluid pressure. Using this set-up, the FoC generated during CaO hydration could be measured directly. Our results show FoC-induced stresses reaching up to 153 MPa, with reaction stopping or slowing down before completion. Failure to achieve the GPa stresses predicted by theory is attributed to competition between FoC development and its inhibiting effect on reaction progress. Microstructural observations indicate that reaction-induced stresses shut down pathways for water into the sample, hampering ongoing reaction and limiting the magnitude of stress build-up to the values observed. The results nonetheless point the way to understanding the behaviour of such systems and to finding engineering solutions that may allow large controlled stresses and strains to be achieved in wellbore sealing operations in future.

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“…9 in the appendix) show that, for pretreated sorbents, there is a progressive reduction of the gain of conversion due to diffusive carbonation On the other hand, the relative gain of conversion due to diffusive carbonation increases with the cycle number for nonpretreated sorbents (q < 0) even though regeneration in these cases is initially small (b << 1). The relative loss of surface area of the renovated soft skeleton is sintering in an inert dry atmosphere) [30]. The model yields a simple analytical equation…”

Section: Models On Multicyclic Cao Conversionmentioning

confidence: 99%

“…According to the measurements reported by Borgwardt [30,32] on the sintering of nascent CaO in an inert dry atmosphere, we may take for the sintering exponent γ s a value of 2.7.…”

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confidence: 99%

CO2 multicyclic capture of pretreated/doped CaO in the Ca-looping process. Theory and experiments

Valverde

Jiménez

Pérez‐Maqueda

2013

Phys. Chem. Chem. Phys.

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We study in this paper the conversion of CaO-based CO 2 sorbents when subjected to repeated carbonation/calcination cycles with a focus on thermally pretreated/doped sorbents. Analytical equations are derived to describe the evolution of conversion with the cycle number from a unifying model based on the balance between surface area loss due to sintering in the loopingcalcination stage and surface area regeneration as a consequence of solid-state diffusion during the looping-carbonation stage. Multicyclic CaO conversion is governed by the evolution of surface area loss/regeneration that strongly depends on the initial state of the pore skeleton. In the case of thermally pretreated sorbents, the initial pore skeleton is highly sintered and regeneration is relevant whereas, for nonpretreated sorbents, the initial pore skeleton is soft and regeneration is negligible. Experimental results are obtained for sorbents subjected to a preheating controlled rate thermal analysis (CRTA) program. By applying this preheating program in a CO 2 enriched atmosphere, CaO can be subjected to a rapid carbonation followed by a slow rate controlled decarbonation, which yields a highly sintered skeleton displaying a small conversion in the first cycle and self-reactivation in the next ones. Conversely, carbonation of the sorbent at a slow controlled rate enhances CO 2 solid-state diffusion, which gives rise, after a quick decarbonation, to a highly

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Sintering of nascent calcium oxide

Cited by 284 publications

References 16 publications

Modelling of the kinetics of sulphation of CaO particles under CaL reactor conditions

Modelling of the kinetics of sulphation of CaO particles under CaL reactor conditions

Reaction-driven casing expansion: potential for wellbore leakage mitigation

CO2 multicyclic capture of pretreated/doped CaO in the Ca-looping process. Theory and experiments

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