The influence of gasification reactions on char consumption under oxy-combustion conditions: Effects of particle trajectory and conversion

Singer, Simcha L.; Chen, Lei; Ghoniem, Ahmed F.

doi:10.1016/j.proci.2012.07.042

Cited by 23 publications

(10 citation statements)

References 27 publications

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“…In oxy-coal combustion, the char-CO 2 and char-H 2 O gasification reactions may also contribute to the higher CO in the fuel-rich region of the diffusion flame where oxygen concentration is low and the temperature is high. This heterogeneous pathway is not discussed in the present study, and the reader is referred to other relevant studies Ghoniem 2012, Singer, Chen and.…”

Section: Introductionmentioning

confidence: 95%

Modeling CO₂Chemical Effects on CO Formation in Oxy-Fuel Diffusion Flames Using Detailed, Quasi-Global, and Global Reaction Mechanisms

Chen

Ghoniem

2014

Combustion Science and Technology

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Interest in oxy-fuel combustion as one of the leading carbon capture technologies has grown significantly in the past two decades. Experimental studies have shown higher CO concentration in oxy-fuel diffusion flames than in traditional air-fuel flames of both gaseous and solid fuels. The higher CO concentration changes the flame profiles, and it may have impacts on pollutants formation. This paper presents a numerical study regarding the chemical effects of CO 2 on CO formation in the flame region, and their modeling approaches in CFD simulations. Equilibrium calculation confirms higher CO concentration associated with fuel-rich stoichiometry in CO 2 diluted combustion environment.One-dimensional counter flow diffusion flame simulation using detailed reaction mechanisms reveals

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Section: Introductionmentioning

confidence: 95%

Modeling CO₂Chemical Effects on CO Formation in Oxy-Fuel Diffusion Flames Using Detailed, Quasi-Global, and Global Reaction Mechanisms

Chen

Ghoniem

2014

Combustion Science and Technology

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“…However, despite the large number of publications that have been devoted to oxy-fuel combustion in recent years (Maffei et al, 2013;Molina & Shaddix, 2007;Murphy & Shaddix, 2006;Rathnam et al, 2009;Singer, Chen, & Ghoniem, 2013), the quantitative information about the evolution of char chemical structure in the initial stage of oxy-fuel combustion (i.e. non-pure pyrolysis in CO 2 ) is scarce and limited to particle sizes of a few micrometers (Angeles G. Borrego & Alvarez, 2007;Su et al, 2015;B.…”

Section: Introductionmentioning

confidence: 99%

Effects of pyrolysis atmosphere on the porous structure and reactivity of chars from middle and high rank coals

Valdés¹,

Guerrero²,

López³

et al. 2018

Ing. Inv.

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The influence of a CO 2 or N 2 -based atmosphere on the porous structure and microstructure of the chars obtained from the nonisothermal slow devolatilization (10 °C/min), from room temperature to 900 °C, of two coals of different rank (Semi-Anthracite (SA) and High Volatile Bituminous type C (HVBC)) and different particle size distribution was studied. Physicochemical characterization (ultimate and proximate analysis), structural and morphological characterization by Raman spectroscopy, FE-SEM, BET surface area, and volume and diameter microporous by CO 2 adsorption measurements were carried out for all the chars. It was found that the kinetic parameters, the physicochemical properties, and reactivity of the chars are different, depending on the pyrolysis atmosphere. It was also determined that for the char from SA coal with particle size greater than 0.7 mm, the BET surface area increases when the atmosphere is enriched with CO 2 . This effect appears to be promoted by the interaction of different processes such as intraparticle side reactions (softening, nucleation and coalescence of bubbles, crosslinking, among others), differences in the thermal diffusivity of N 2 and CO 2 , and the reactive effects of the latter. Additionally, tests of oxidative reactivity of chars showed that the char formed in a CO 2 atmosphere is more reactive than that formed in N 2 . With the results of Raman analysis and kinetic parameters quantified, it was concluded that the reaction atmosphere determined the degree of ordering achieved by the char structure and that the thermodiffusive properties of the reaction atmosphere promoted structural differences in the char even at low heating rates.Keywords: Slow pyrolysis, Pore size distribution, large coal particles, Oxy-combustion, reactivity. RESUMENSe estudió la influencia de una atmósfera basada en CO 2 o N 2 sobre la estructura porosa y la microestructura de carbonizados de carbón obtenidos de la pirólisis lenta no isotérmica desde temperatura ambiente hasta 900 °C de dos carbones de diferente rango (Semi-Antracita (SA) y Bituminosos Alto en Volátiles tipo C (BAVC)), y de diferentes distribuciones de tamaño de partícula. Para todos los carbonizados se realizó la caracterización fisicoquímica (Análisis ultimo y próximo), la caracterización morfológica y estructural por combinación de técnicas como espectroscopia Rama, Microscopia electrónica de barrido por emisión de campo (FE-SEM), área superficial (BET -Brunauer-Emmett-Teller) y volumen y diámetro de microporos por mediciones de adsorción en CO 2 (Horvath-Kawazoe (HK) method). Se encontró que los parámetros cinéticos, las propiedades fisicoquímicas y la reactividad de los carbonizados de carbón son diferentes dependiendo de la atmósfera de pirólisis. También se determinó que para el carbonizado de carbón de SA, con un tamaño de partícula mayor de 0,7 mm, la superficie BET aumenta cuando la atmósfera se enriquece en CO 2 . Este efecto parece ser promovido por la interacción de diferentes procesos como las reacciones secund...

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“…The influence of gasification reactions on the temperature profiles, burnout time and consumption rates during the oxy-combustion process have been studied by simulating the gas atmospheres employed in oxy-combustion process (O 2 /CO 2 ) [6][7][8] . The obtained results revealed that char gasification by CO 2 should not be neglected under oxy-combustion process because of the accelerated carbon consumption when CO 2 is present.…”

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confidence: 99%

“…The obtained results revealed that char gasification by CO 2 should not be neglected under oxy-combustion process because of the accelerated carbon consumption when CO 2 is present. This can be attributed to the CO 2 ability to penetrate the particles during the process, thus CO 2 reacts uniformly throughout the char particle, leading to structural changes 8 .…”

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confidence: 99%

Potassium Catalytic Effect on Gasification Reactions of Coal and Coal/Biomass Blends under Oxy-combustion Conditions. An Isotopic Study Using ¹³C¹⁸O₂

et al. 2018

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In the present study, 20 wt % K 2 CO 3 was added to coal and coal/biomass blends in 20:80 wt % ratio and subsequently were heating-treated at 600 °C using CO 2 or N 2 atmospheres.The reactivity under oxy-combustion conditions (21 % O 2 + 79 % CO 2 ) was studied by thermogravimetry, and characterization of chars was carried out by N 2 adsorption, scanning electron microscopy, Raman and X-ray photoelectron spectroscopy. It was observed higher activation energy for impregnated coal/biomass blends compared to impregnated coal, likewise, for materials thermally treated with CO 2 . It is demonstrated that CO 2 gasification takes place together with O 2 combustion under oxy-combustion conditions. Isotopic labelled 13 C 18 O 2 was used to confirm the participation of CO 2 gasification reactions at 450, 500, 550 and 600 ᵒ C in both catalyzed and uncatalyzed systems under O 2 + CO 2 . The catalytic effect of potassium promotes CO 2 gasification, and highest CO ( 12 C 18 O) desorption was obtained with impregnated samples. It is possible to suggest that CO 2 gasification reactions follow different reaction pathways in presence or absence of potassium. The catalytic gasification reaction proceeded preferentially through a molecular CO 2 ( 13 C 18 O 2 ) adsorption route while the non-catalyzed systems advanced using a dissociative adsorption pathway.

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The influence of gasification reactions on char consumption under oxy-combustion conditions: Effects of particle trajectory and conversion

Cited by 23 publications

References 27 publications

Modeling CO₂Chemical Effects on CO Formation in Oxy-Fuel Diffusion Flames Using Detailed, Quasi-Global, and Global Reaction Mechanisms

Modeling CO₂Chemical Effects on CO Formation in Oxy-Fuel Diffusion Flames Using Detailed, Quasi-Global, and Global Reaction Mechanisms

Effects of pyrolysis atmosphere on the porous structure and reactivity of chars from middle and high rank coals

Potassium Catalytic Effect on Gasification Reactions of Coal and Coal/Biomass Blends under Oxy-combustion Conditions. An Isotopic Study Using ¹³C¹⁸O₂

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The influence of gasification reactions on char consumption under oxy-combustion conditions: Effects of particle trajectory and conversion

Cited by 23 publications

References 27 publications

Modeling CO2Chemical Effects on CO Formation in Oxy-Fuel Diffusion Flames Using Detailed, Quasi-Global, and Global Reaction Mechanisms

Modeling CO2Chemical Effects on CO Formation in Oxy-Fuel Diffusion Flames Using Detailed, Quasi-Global, and Global Reaction Mechanisms

Effects of pyrolysis atmosphere on the porous structure and reactivity of chars from middle and high rank coals

Potassium Catalytic Effect on Gasification Reactions of Coal and Coal/Biomass Blends under Oxy-combustion Conditions. An Isotopic Study Using 13C18O2

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Modeling CO₂Chemical Effects on CO Formation in Oxy-Fuel Diffusion Flames Using Detailed, Quasi-Global, and Global Reaction Mechanisms

Modeling CO₂Chemical Effects on CO Formation in Oxy-Fuel Diffusion Flames Using Detailed, Quasi-Global, and Global Reaction Mechanisms

Potassium Catalytic Effect on Gasification Reactions of Coal and Coal/Biomass Blends under Oxy-combustion Conditions. An Isotopic Study Using ¹³C¹⁸O₂