Effect of CO2 and H2O on lignite char structure and reactivity in a fluidized bed reactor

Li, Lin; Tong, Shuai; Duan, Lunbo; Zhao, Changsui; Shi, Zhipeng

doi:10.1016/j.fuproc.2020.106564

Cited by 25 publications

(7 citation statements)

References 34 publications

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“…Hence, the formed NO is rapidly destructed via HCN + NO → N 2 + products, thereby blocking the fuel-NO conversion . Third, the development of a pore structure in unburned semi-char is facilitated with the enhanced gasification reaction, and the specific surface area and total pore volume are greatly increased . Qing et al reported that the char reactivity could be also promoted.…”

Section: Resultsmentioning

confidence: 99%

“…41 Third, the development of a pore structure in unburned semi-char is facilitated with the enhanced gas- ification reaction, and the specific surface area and total pore volume are greatly increased. 43 Qing et al 44 reported that the char reactivity could be also promoted. Hence, the heterogeneous reduction of NO by semi-char is strengthened, i.e., C char + NO → N 2 + products.…”

Section: Fuel-no Conversionmentioning

confidence: 99%

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MILD-Oxy Combustion Characteristics of Pulverized Coal Affected by Oxidizer O₂ Concentrations under Dry and Wet Recycle Modes

et al. 2023

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Moderate or intense low-oxy dilution oxy-fuel (MILD-oxy) combustion can synergistically reduce the emissions of CO 2 and NO x , and its industrial implementation is carried out under dry and wet recycle modes. In this work, a series of numerical simulations on pulverized coal MILD-oxy combustion under the typical dry and wet recycle modes are performed, aiming at fully evaluating the combustion behaviors affected by the oxidizer O 2 concentration (21−30%) under different recycle modes. The results show that increasing O 2 concentration weakens the in-furnace flue gas recirculation and promotes the combustion intensity, while a more uniform temperature distribution is obtained under dry recycle mode than under wet recycle mode. The diffusion/kinetics-controlled MILD regime is realized as the O 2 concentration increases. Nevertheless, the diffusion effect is enhanced due to the accelerated reaction rate under a high O 2 level. The gasification reaction is strengthened with the increased O 2 concentration. Compared with wet recycle mode, the burnout of coal char is slowed down under dry recycle mode because of the lower burnout rate. The fuel-NO conversion ratio is significantly reduced with the increased O 2 concentration, while wet recycle mode shows more potential in achieving low NO x emission than dry recycle mode. This work is expected to provide new insights into the comprehensive understanding of MILD-oxy combustion.

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Section: Resultsmentioning

confidence: 99%

Section: Fuel-no Conversionmentioning

confidence: 99%

MILD-Oxy Combustion Characteristics of Pulverized Coal Affected by Oxidizer O₂ Concentrations under Dry and Wet Recycle Modes

et al. 2023

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“…This may be because AAEMs in the char promoted the decomposition of residual tar on the char (tar → H 2 , CO; R(1) and R(2), see Table 3) [38]. In addition, the CO 2 generated inside the carbon matrix reacted with the char to expand the pores, while the light volatiles reacted with the char on the surface of the char, and consumed the carbon matrix (R( 4)) [39]. Moreover, methane reforming (R( 7)) and methane decomposition (R( 8))…”

Section: Factors Leading To Synergies During Co-pyrolysis Of Coal and Biomassmentioning

confidence: 99%

Progress on the Co-Pyrolysis of Coal and Biomass

Chen¹,

Zhang²,

Liu³

et al. 2022

Biorefineries - Selected Processes

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In this chapter, the synergistic mechanism and the resulting influence during co-pyrolysis of coal and biomass, are summarized. The properties of coal and biomass, the release and migration of alkali and alkaline earth metals (AAEMs), the interaction between volatile and char, the characteristics of the resulting volatiles, and the physicochemical structure and reactivity of co-pyrolysis char, are also analyzed. In addition, the influence of AAEMs on the properties of the co-pyrolysis products is reviewed. Moreover, the analysis of the co-pyrolysis industry demonstration is also mentioned. Finally, this chapter also proposes some additional possibilities, based on further literature research.

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“…In the past several decades, circulating fluidized bed (CFB) boilers have been rapidly developed . Thus, 600 MW supercritical CFB boilers have come into service, and a 660 MW ultra-supercritical CFB is under construction in China and is planned to be put into operation in 2022. , CFB boilers have higher combustion stability and are more flexible for a wider range of fuels, especially for poor quality fuels, like coal gangue, lean coal, and refuse-derived fuels …”

Section: Introductionmentioning

confidence: 97%

“…2,3 CFB boilers have higher combustion stability and are more flexible for a wider range of fuels, especially for poor quality fuels, like coal gangue, lean coal, and refuse-derived fuels. 4 Limestone is widely used to in situ capture SO 2 in CFB boilers. In-furnace sulfur capture is easy to employ because no additional reactor is needed, and this greatly saves the construction and operation costs.…”

Section: Introductionmentioning

confidence: 99%

Insight into the Mechanism and Effect of H₂O on CaO Sulfation by Density Functional Theory

et al. 2022

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The CaO sulfation is the main reaction to capture SO2 by limestone in circulating fluidized boilers. The mechanism and effects of H2O on CaO sulfation were investigated by density functional theory and experiments. The reaction paths and energy barriers for SO4 2– forming on CaO and CaSO4 surfaces as well as the outward diffusion of Ca2+/O2– in CaO and CaSO4 crystals were examined. Under conditions without H2O, the outward diffusion of Ca2+ on the CaSO4 surface is the rate-determining step for CaO sulfation because it has the largest energy barrier (3.63 eV) of all steps in the sulfation reaction. Under conditions with H2O, X-ray diffraction analysis indicates that H2O cannot directly accelerate the diffusion of Ca2+ in the CaSO4 layer. However, with the assistance of H2O, the interactions between Ca2+ and SO4 2– on the CaSO4 surface become weaker, the energy barrier for the diffusion of Ca2+ decreases from 3.63 to 1.62 eV, and thus the outward diffusion of Ca2+ on the CaSO4 surface is enhanced. The rate-determining step of the sulfation reaction under conditions with H2O became O2– diffusion in the CaSO4 layer with an energy barrier of 3.42 eV, which means that H2O decreases the largest energy barrier for sulfation by 0.21 eV. In addition, H2O can also enhance the adsorption of SO2 on a CaSO4 surface.

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Effect of CO2 and H2O on lignite char structure and reactivity in a fluidized bed reactor

Cited by 25 publications

References 34 publications

MILD-Oxy Combustion Characteristics of Pulverized Coal Affected by Oxidizer O₂ Concentrations under Dry and Wet Recycle Modes

MILD-Oxy Combustion Characteristics of Pulverized Coal Affected by Oxidizer O₂ Concentrations under Dry and Wet Recycle Modes

Progress on the Co-Pyrolysis of Coal and Biomass

Insight into the Mechanism and Effect of H₂O on CaO Sulfation by Density Functional Theory

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Effect of CO2 and H2O on lignite char structure and reactivity in a fluidized bed reactor

Cited by 25 publications

References 34 publications

MILD-Oxy Combustion Characteristics of Pulverized Coal Affected by Oxidizer O2 Concentrations under Dry and Wet Recycle Modes

MILD-Oxy Combustion Characteristics of Pulverized Coal Affected by Oxidizer O2 Concentrations under Dry and Wet Recycle Modes

Progress on the Co-Pyrolysis of Coal and Biomass

Insight into the Mechanism and Effect of H2O on CaO Sulfation by Density Functional Theory

Contact Info

Product

Resources

About

MILD-Oxy Combustion Characteristics of Pulverized Coal Affected by Oxidizer O₂ Concentrations under Dry and Wet Recycle Modes

MILD-Oxy Combustion Characteristics of Pulverized Coal Affected by Oxidizer O₂ Concentrations under Dry and Wet Recycle Modes

Insight into the Mechanism and Effect of H₂O on CaO Sulfation by Density Functional Theory