How does the concentration of CO<sub>2</sub> affect its uptake by a synthetic Ca‐based solid sorbent?

Pacciani, Roberta; Müller, Christoph R.; Davidson, John; Dennis, John S.; Hayhurst, A.N.

doi:10.1002/aic.11611

Cited by 43 publications

(36 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The evolution of CaO conversion would be strongly affected whenever solid-state diffusive carbonation, which is a crystal structure sensitive property, is relevant. For example, CaO/mayenite polycrystalline composites are seen to exhibit reactivation similarly to pretreated limestones [47][48][49][50][51] even under severe calcination conditions [51]. As well known, solid-state diffusion is enhanced in polycrystalline materials as compared to pure crystals because of the accelerated diffusion along the grain boundaries [52].…”

Section: A Analysis Of Multicyclic Cao Conversion Datamentioning

confidence: 96%

Multicyclic conversion of limestone at Ca-looping conditions: The role of solid-sate diffusion controlled carbonation

Jiménez

Valverde

Pérez‐Maqueda

2014

Fuel

View full text Add to dashboard Cite

Limestone derived CaO conversion when subjected to multiple carbonation/calcination cycles is a subject of interest currently fueled by several industrial applications of the so-called Ca-looping (CaL) technology. The multicyclic CaO conversion at Ca-looping conditions exhibits two main features as demonstrated by thermogravimetric analysis (TGA). On one hand, carbonation occurs by two well differentiated phases: a first kinetically-driven fast phase and a subsequent much slower solid-state diffusion controlled phase. On the other, carbonation in the fast phase usually exhibits a drastic decay with the cycle number along the first carbonation/calcination cycles. This trend can be reversed by means of heat pretreatment, which induces a marked loss of fast conversion in the first carbonation but enhances diffusion of CO 2 in the solid. Upon decarbonation the regenerated CaO skeleton shows an increased conversion in the fast carbonation phase of the next cycle, a phenomenon which has been referred to as reactivation. Nonetheless, sorbent reactivation is hampered by looping carbonation/calcination conditions as those to be likely found in practice such as carbonation stages characterized by low CO 2 concentrations and short duration and calcination stages at high temperatures in a CO 2 enriched atmosphere, which causes a sintering and loss of activity of the regenerated CaO skeleton. We analyze in this work sorbent reactivation as affected by heat pretreatment and carbonation/calcination conditions. Aimed at shedding light on the role played by these conditions on reactivation we look separately at the multicyclic evolution of conversion in the kinetic and diffusive phases. Generally, the evolution of multicyclic conversion after the first cycle can be described by a balance between the surface area gain due to diffusive carbonation and the surface area loss as caused by sintering in the calcination stage. A significant gain of relative surface area after the first cycle, which is favored by harshening the heat pretreatment conditions, leads however to a marked decay of it during subsequent cycles, which precludes reactivation for an extended interval of cycles. On the other hand, sorbent grinding, if performed before heat pretreatment, leads to a less marked but more sustainable reactivation along the cycles. A novel observation reported in our work is that pretreatment of limestone in a CO 2 atmosphere leads upon a subsequent quick decarbonation to a CaO skeleton with extraordinarily enhanced reactivity in the kinetically-driven carbonation phase and with a high resistance to solid-state diffusion, which can be attributed to annealing of the crystal structure as reported by independent studies. 2

show abstract

Section: A Analysis Of Multicyclic Cao Conversion Datamentioning

confidence: 96%

Multicyclic conversion of limestone at Ca-looping conditions: The role of solid-sate diffusion controlled carbonation

Jiménez

Valverde

Pérez‐Maqueda

2014

Fuel

View full text Add to dashboard Cite

show abstract

“…Longer carbonation times can regenerate the sorbent (Barker, 1973, Lysikov et al, 2007Chen et al, 2009) though the effect of this is somewhat inconsistent elsewhere (Manovic and Anthony, 2008d). A higher CO 2 concentration during carbonation has been shown to improve the uptake of some synthetic sorbents (Pacciani et al, 2008b). In cases where the CO 2 concentration is higher during calcination this consistently leads to a more rapid drop-off in reactivity (Li et al, 2005; however there are cases where the effect of CO 2 concentration in calcination is only noticeable over the first five cycles .…”

Section: Sorbent Performancementioning

confidence: 99%

The calcium looping cycle for CO2 capture from power generation, cement manufacture and hydrogen production

Dean

Blamey

Florin

et al. 2011

Chemical Engineering Research and Design

337

226

View full text Add to dashboard Cite

“…limestone, dolomite), it makes sense to use the material over several cycles and to perform multiple regenerations before disposing of the used carbonate, so as to achieve genuine energy and CO 2 emissions reductions. Research efforts are taking place worldwide to understand the reasons for the loss of CO 2 capacity with repeated cycling and increase the durability of Ca-based CO 2 sorbent with this very aim [35][36][37][38][39][40][41][42][43]. Table 2 allows comparison of the minima of enthalpy changes of the urea-water system at 1 atm (and the temperatures at which they occur) with those of the urea-water-CaO system (with Ca:C=1), in kJ/mol of H 2 produced, alongside the H ratio, maxima of H 2 yield and of H 2 purity, also listed with their corresponding temperatures.…”

Section: Figurementioning

confidence: 99%

Thermodynamics of hydrogen production from urea by steam reforming with and without in situ carbon dioxide sorption

Dupont

Twigg²,

Rollinson

et al. 2013

International Journal of Hydrogen Energy

View full text Add to dashboard Cite

The thermodynamic effects of molar steam to carbon ratio (S:C), of pressure, and of having CaO present on the H 2 yield and enthalpy balance of urea steam reforming were investigated.At a S:C of 3 the presence of CaO increased the H 2 yield from 2.6 mol H 2 /mol urea feed at 940 K to 2.9 at 890 K, and decreased the enthalpy of bringing the system to equilibrium. A minimum enthalpy of 180.4 kJ was required to produce 1 mole of H 2 at 880 K. This decreased to 94.0 kJ at 660 K with CaO-based CO 2 sorption and, when including a regeneration step of the CaCO 3 at 1170 K, to 173 kJ at 720 K. The presence of CaO allowed widening the range of viable operation at lower temperature and significantly inhibited carbon formation. The feasibility of producing H 2 from renewable urea in a low carbon future is discussed.

show abstract

How does the concentration of CO₂ affect its uptake by a synthetic Ca‐based solid sorbent?

Cited by 43 publications

References 13 publications

Multicyclic conversion of limestone at Ca-looping conditions: The role of solid-sate diffusion controlled carbonation

Multicyclic conversion of limestone at Ca-looping conditions: The role of solid-sate diffusion controlled carbonation

The calcium looping cycle for CO2 capture from power generation, cement manufacture and hydrogen production

Thermodynamics of hydrogen production from urea by steam reforming with and without in situ carbon dioxide sorption

Contact Info

Product

Resources

About

How does the concentration of CO2 affect its uptake by a synthetic Ca‐based solid sorbent?

Cited by 43 publications

References 13 publications

Multicyclic conversion of limestone at Ca-looping conditions: The role of solid-sate diffusion controlled carbonation

Multicyclic conversion of limestone at Ca-looping conditions: The role of solid-sate diffusion controlled carbonation

The calcium looping cycle for CO2 capture from power generation, cement manufacture and hydrogen production

Thermodynamics of hydrogen production from urea by steam reforming with and without in situ carbon dioxide sorption

Contact Info

Product

Resources

About

How does the concentration of CO₂ affect its uptake by a synthetic Ca‐based solid sorbent?