Characterization of calcium carbonate sorbent particle in furnace environment

Lee, Kang Soo; Jung, Jae Hee; Keel, Sang In; Yun, Jin Han; Min, Tai Jin; Kim, Sang Soo

doi:10.1016/j.scitotenv.2012.03.075

Cited by 12 publications

(6 citation statements)

References 22 publications

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“…Calcium carbonate is a polymorphous, variform compound, which nucleates into three different crystal modifications: calcite, aragonite, and vaterite. − Most limestone sources consist essentially of calcite as it is the thermodynamically most stable polymorph under ambient conditions . The most common crystal system of calcite is the rhombohedral one, which exposes {101̅4} faces, and is frequently used in experimental and theoretical studies as a model structure. , With all their advantages, calcium carbonate rock, that is, limestone, marble, and chalk, enjoy considerable industrial utilization. ,, They are important in the pharmaceutical, paper, plastic, and food industries and are also used in water purification as precipitates strengthening the soils and as a sorbent for exhaust gasses. ,− Moreover, it is considered as a key mineral to build many organisms’ exoskeletons for protecting and supporting purposes, as well as tissues for light perception and storage of calcium ions. ,,, Understanding the surface chemistry of calcium carbonates and their interactions with other substances is thus essential. In particular, the dynamic nature of the calcite surface is an important issue where much information can be gained by use of scanning probe methods. − …”

Section: Introductionmentioning

confidence: 99%

Surface-Modified and Unmodified Calcite: Effects of Water and Saturated Aqueous Octanoic Acid Droplets on Stability and Saturated Fatty Acid Layer Organization

et al. 2021

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A profound understanding of the properties of unmodified and saturated fatty acid-modified calcite surfaces is essential for elucidating their resistance and stability in the presence of water droplets. Additional insights can be obtained by also studying the effects of carboxylic acid-saturated aqueous solutions. We elucidate surface wettability, structure, and nanomechanical properties beneath and at the edge of a deposited droplet after its evaporation. When calcite was coated by a highly packed monolayer of stearic acid, a hydrophilic region was found at the three-phase contact line. In atomic force microscopy mapping, this region is characterized by low adhesion and a topographical hillock. The surface that previously was covered by the droplet demonstrated a patchy structure of about 6 nm height, implying stearic acid reorganization into a patchy bilayer-like structure. Our data suggest that during droplet reverse dispensing and droplet evaporation, pinning of the three-phase contact line leads to the transport of dissolved fatty carboxylic acid and possibly calcium bicarbonate Ca(HCO 3 ) 2 molecules to the contact line boundary. Compared to the surface of intrinsically hydrophobic materials, such as polystyrene, the changes in contact angle and base diameter during droplet evaporation on stearic acid-modified calcite are strikingly different. This difference is due to stearic acid reorganization on the surface and transport to the water−air interface of the droplet. An effect of the evaporating droplet is also observed on unmodified calcite due to dissolution and recrystallization of the calcite surface in the presence of water. In the case where a water droplet saturated with octanoic acid is used instead of water, the stearic acid-coated calcite remains considerably more stable. Our findings are discussed in terms of the coffee-ring effect.

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Section: Introductionmentioning

confidence: 99%

Surface-Modified and Unmodified Calcite: Effects of Water and Saturated Aqueous Octanoic Acid Droplets on Stability and Saturated Fatty Acid Layer Organization

et al. 2021

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“…The multicyclic loss of CaO conversion in the carbonation stage is accentuated even more by the introduction of a recarbonation stage if sorbent regeneration is performed under CO 2 .X-ray Diffraction (XRD) analysis of limestone decomposition in air shows that CaCO 3Bragg peaks totally disappear at calcination temperatures T c 800 • after which further increase of temperature or calcination time leads to an increase of the CaO crystal coherence length (crystallite size)[42][43][44][45]. Likewise, crystallite size is promoted by multicyclic c/c[46] and high CO 2 partial pressure in the calcination environment[44,47]. Empirical studies demonstrate that the specific surface area of CaO derived from limestone calcination is decreased as the crystallite size is increased following a common trend for a diverse variety of conditions such as varying calcination time and temperature, CO2 concentration in the calcination atmosphere, and presence of impurities/additives [43, 44, 48].…”

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confidence: 99%

Calcium-looping for post-combustion CO2 capture. On the adverse effect of sorbent regeneration under CO2

2014

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The multicyclic carbonation/calcination (c/c) of CaO solid particles at high temperature is at the basis of the recently emerged Calcium-looping (CaL) technology, which has been shown to be potentially suitable for achieving high and sustainable post-combustion CO 2 capture efficiency. Despite the success of pilot plant projects at the MW th scale, a matter of concern for scaling-up the CaL technology to a commercial level (to the GW th scale) is that the CaO carbonation reactivity can be recovered only partially when the sorbent is regenerated by calcination at high temperatures (around 950 • C) as required by the CO 2 high concentration in the calciner. In order to reactivate the sorbent, a novel CaL concept has been proposed wherein a recarbonator reactor operated at high temperature/high CO 2 concentration leads to further carbonation of the solids before entering into the calciner for regeneration. Multicyclic thermogravimetric analysis (TGA) tests demonstrate the feasibility of recarbonation to reactivate the sorbent regenerated at high calcination temperatures yet at unrealistically low CO 2 partial pressure mainly because of technical limitations concerning low heating/cooling rates. We report results from multicyclic c/c and carbonation/recarbonation/calcination (c/r/c) TGA tests at high heating/coling rates and in which the sorbent is regenerated in a dry atmosphere at high CO 2 partial pressure. It is shown that that at these conditions there is a drastic drop of CaO conversion to a very small residual value in just a few cycles. Moreover, the introduction of a recarbonation stage has actually an adverse effect. Arguably, CaCO 3 decomposition in a CO 2 rich atmosphere is ruled by CO 2 dynamic adsorption/desorption in reactive CaO (111) surfaces as suggested by theoretical studies, which would preclude the growth of the regenerated CaO crystal structure along these reactive surfaces and would be intensified by recarbonation. Nevertheless, the presence of H 2 O in the calciner, which is also adsorbed/desorbed 2 dynamically in CaO reactive planes, would shield CO 2 adsorption/desorption thus mitigating the deeply detrimental effect of CO 2 on the carbonation reactivity of the regenerated CaO structure. Oxy-combustion, which produces a significant amount of H 2 O, is currently used in pilot-scale plants to raise the temperature in the calciner although alternative techniques are being explored since it represents an important penalty to the CaL technology. Our study suggests that steam injection would be necessary in a dry calciner environment to avoid a sharp loss of CaO conversion if the sorbent is regenerated at high CO 2 partial pressure.

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“…Calcination, sintering and sulphation behaviour under high CO 2 concentration is different from that in conventional combustion atmosphere, which is possibly an important reason for the high desulphurization efficiency in oxyfuel combustion [36]. Lee et al [37] found that sorbent particles (CaCO 3 ) rapidly calcined and sintered in the air atmosphere, whereas, calcination was delayed in the CO 2 atmosphere due to the higher CO 2 partial pressure. Instead, the sintering effect was dominant in the CO 2 atmosphere early in the reaction.…”

Section: Desulphurisation Tests With Limestone Addition At Various Camentioning

confidence: 99%

Oxyfuel technology: Oil shale desulphurisation behaviour during unstaged combustion

Al-Makhadmeh

Maier

Batiha

et al. 2015

Fuel

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Characterization of calcium carbonate sorbent particle in furnace environment

Cited by 12 publications

References 22 publications

Surface-Modified and Unmodified Calcite: Effects of Water and Saturated Aqueous Octanoic Acid Droplets on Stability and Saturated Fatty Acid Layer Organization

Surface-Modified and Unmodified Calcite: Effects of Water and Saturated Aqueous Octanoic Acid Droplets on Stability and Saturated Fatty Acid Layer Organization

Calcium-looping for post-combustion CO2 capture. On the adverse effect of sorbent regeneration under CO2

Oxyfuel technology: Oil shale desulphurisation behaviour during unstaged combustion

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