Pressurized calcium looping in the presence of steam in a spout-fluidized-bed reactor with DFT analysis

Fan, Yaming; Yao, Joseph G.; Zhang, Zili; Sceats, Mark G.; Zhuo, Yuqun; Li, Liangliang; Maitland, Geoffrey C.; Fennell, Paul S.

doi:10.1016/j.fuproc.2017.09.006

Cited by 32 publications

(21 citation statements)

References 64 publications

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“…Obviously, for O‐top site, the lowest adsorption energy, −144.23 kJ/mol, suggests that it is the most active one. The adsorption energy is different from the previous work, −128.9 kJ/mol, due to setting different parameters and using the DFT‐D in this paper. The shorter distance of C‐O s , which is similar to the bond length of C‐O1 and C‐O2 (bond of CO 2 after its adsorption on the CaO (001) surface), verifies the strong interaction between CO 2 and the CaO (001) surface.…”

Section: Resultscontrasting

confidence: 65%

“…The realistic carbonation atmosphere in CaL contains both H 2 O and CO 2 and steam might be injected into the system to improve the carbonation, so it is important to ascertain whether the binary adsorption of CO 2 and H 2 O is promoted or inhibited and how carbonation is enhanced by the addition of H 2 O. Comparing the simulations of CO 2 adsorption over a clean CaO surface (without steam) with a CaO surface with the presence of steam, Fan et al . suggested that steam promotes CO 2 adsorption via the formation of surface OH groups on the CaO surface by DFT calculations.…”

Section: Introductionmentioning

confidence: 99%

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Explaining steam‐enhanced carbonation of CaO based on first principles

et al. 2018

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Calcium-based sorbents have been regarded as effective agents for capturing CO 2 from industrial flue gas. Recent studies have shown that steam can enhance the carbonation performance of calcium-based sorbents. In this paper, a CaO (001) surface was made to investigate the micro-level mechanism of steam-enhanced carbonation based on first principles calculations. Charge transfer and bond population were calculated to evaluate an interaction effect between adsorbates and the CaO (001) surface. Individual adsorption of CO 2 and H 2 O was compared with binary adsorption and co-adsorption of the two molecules on the CaO (001) surface, based on dispersion-corrected density functional theory (DFT-D) calculations. First, the predicted adsorption energies suggest the O-top site is the best site. It forms carbonate-like structure and hydroxyl-like structure for the individual adsorption of CO 2 and H 2 O. Binary adsorption calculations indicate that H 2 O is more easily adsorbed by the CaO (001) surface than CO 2 . The adsorption of H 2 O and CO 2 adsorption are promoted in comparison with their individual adsorption on the CaO (001) surface. Moreover, the analysis of adsorption energies and partial density of states (PDOS) suggests that a H 2 O-CaO (001) surface (CaO (001) surface that has already adsorbed H 2 O) is more reactive than the clean CaO (001) surface for CO 2 adsorption, which further supports the idea that the steam-enhanced mechanism is an Eley-Rideal (E-R) mechanism, which means H 2 O is adsorbed on the CaO surface, and then CO 2 is adsorbed. C

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Section: Resultscontrasting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Explaining steam‐enhanced carbonation of CaO based on first principles

et al. 2018

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“…The Castep module was used to calculate the bond number and the Mulliken population value between the scale inhibitor molecule and the surface. The functional used for these calculations is the GGA of Perdew, Burke, and Enzerhof (PBE) 16,17 .…”

Section: Molecular Models and Simulation Detailsmentioning

confidence: 99%

The inhibition effect mechanisms of four scale inhibitors on the formation and crystal growth of CaCO3 in solution

Zhang

2019

Sci Rep

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The experimentation, molecular dynamics simulation and DFT calculation were used to study the inhibition effects of four scale inhibitors, including polyacrylic acid (PAA), hydrolyzed polymaleic anhydride (HPMA), polyepoxysuccinic acid (PESA) and polyaspartic acid (PASP), on formation and crystal growth of CaCO3 in solutions. According to concentrations of Ca2+ in solutions, the sequence of inhibition effects of scale inhibitors on formation of CaCO3 in the solution was PESA > PASP > HPMA > PAA. Characterization of CaCO3 crystals by XRD and a laser particle size analyzer indicated that the sequence of inhibition effects of scale inhibitors on crystal growth of CaCO3 in solutions was PESA > HPMA > PASP > PAA. Interaction energies between the scale inhibitor molecule and Ca2+, and between the scale inhibitor molecule and the CaCO3 (104) surface indicated that the difference of the inhibition effects was derived from the difference in the interaction energy. The results of DFT calculation indicated that the difference between the interaction energies of these inhibitors and Ca2+ was derived from differences of number and the Mulliken population values of the chemical bonds which formed between the inhibitor molecule and Ca2+ and between the inhibitor molecule and the CaCO3 surface.

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“…To know more about the real reaction characteristics, the interaction of the two reactions in the simultaneous calcination/sulfation process requires attention. It is worth noting that the issue of reaction product interfering with limestone calcination is not only limited to SO 2 capture in CFBs, but is also important for other processes like CO 2 capture by calcium looping . Therefore, in our previous work, the characteristics of the simultaneous calcination/sulfation reaction were investigated by thermogravimetric analysis (TGA).…”

Section: Introductionmentioning

confidence: 99%

The combined effect of H₂O and SO₂ on the simultaneous calcination/sulfation reaction in CFBs

et al. 2019

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The combined effect of H2O and SO2 on the reaction kinetics and pore structure of limestone during simultaneous calcination/sulfation reactions under circulating fluidized bed (CFB) conditions was first studied in a constant‐temperature reactor. H2O can accelerate the sulfation reaction rate in the slow‐sulfation stage significantly but has a smaller effect in the fast‐sulfation stage. H2O can also accelerate the calcination of CaCO3, and should be considered as a catalyst, as the activation energy for the calcination reaction was lower in the presence of H2O. When the limestone particles are calcining, SO2 in the flue gas can react with CaO on the outer particle layer and the resulting CaSO4 blocks the CaO pores, increases the diffusion resistance of CO2, and, in consequence, decreases the calcination rate of CaCO3. Here, gases containing 15% H2O and 0.3% SO2 are shown to increase the calcination rate. This means that the accelerating effect of 15% H2O on CaCO3 decomposition is stronger than the impeding effect caused by 0.3% SO2. The calcination rate of limestone particles was controlled by both the intrinsic reaction and the CO2 diffusion rate in the pores, but the intrinsic reaction rate played a major role as indicated by the effectiveness factors determined in this work. This may explain the synergic effect of H2O and SO2 on CaCO3 decomposition observed here. Finally, the effect of H2O and SO2 on sulfur capture in a 600 MWe CFB boiler burning petroleum coke is also analyzed. The sulfation performance of limestone evaluated by simultaneous calcination/sulfation is shown to be much higher than that by sulfation of CaO. Based on our calculations, a novel use of the wet flue gas recycle method was put forward to improve the sulfur capture performance for high‐sulfur low‐moisture fuels such as petroleum coke. © 2019 American Institute of Chemical Engineers AIChE J, 65: 1256–1268, 2019

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Pressurized calcium looping in the presence of steam in a spout-fluidized-bed reactor with DFT analysis

Cited by 32 publications

References 64 publications

Explaining steam‐enhanced carbonation of CaO based on first principles

Explaining steam‐enhanced carbonation of CaO based on first principles

The inhibition effect mechanisms of four scale inhibitors on the formation and crystal growth of CaCO3 in solution

The combined effect of H₂O and SO₂ on the simultaneous calcination/sulfation reaction in CFBs

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Pressurized calcium looping in the presence of steam in a spout-fluidized-bed reactor with DFT analysis

Cited by 32 publications

References 64 publications

Explaining steam‐enhanced carbonation of CaO based on first principles

Explaining steam‐enhanced carbonation of CaO based on first principles

The inhibition effect mechanisms of four scale inhibitors on the formation and crystal growth of CaCO3 in solution

The combined effect of H2O and SO2 on the simultaneous calcination/sulfation reaction in CFBs

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The combined effect of H₂O and SO₂ on the simultaneous calcination/sulfation reaction in CFBs