CO2 gasification of Thai coal chars: Kinetics and reactivity studies

Sawettaporn, Supaporn; Bunyakiat, Kunchana; Kitiyanan, Boonyarach

doi:10.1007/s11814-009-0168-9

Cited by 18 publications

(11 citation statements)

References 16 publications

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“…The reactivity index (R) of the char was calculated from eq 4. 25,26 This definition is widely used in the literature for comparison of reactivity of different coals…”

Section: Char Combustion Reactivitymentioning

confidence: 99%

Characteristics of Chars from Low-Temperature Pyrolysis of Lignite

et al. 2013

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Low-temperature pyrolysis offers a potential way of upgrading lignite and producing chars to replace thermal or pulverized coal injection (PCI) coals in combustion or being used as inert components in a blend for coking. In this study, the characteristics of chars from low-temperature pyrolysis of two lignite coals have been investigated. The changes in char morphology and chemical structures were investigated using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The combustion reactivity of chars was analyzed in a thermogravimetric analyer (TGA) using non-isothermal techniques. The results show that chars from low-temperature pyrolysis of lignite coal below 450 °C were more reactive than higher temperature chars. Higher reactivity of low-temperature chars was attributed to the higher concentration of active sites and lower degree of structural order compared to that of high-temperature chars. Indonesian (YN) lignite showed a higher weight loss rate compared to Hulunbeier (HL) coal, which was attributed to a higher concentration of liptinite and vitrinite in YN coal. FTIR analysis indicated that the aliphatic structures and oxygen-containing functional groups decreased with an increasing pyrolysis temperature. The intensity of tightly bound cyclic OH tetramers and OH−ether O hydrogen bonds were higher than other hydrogen bonds in the 3700−3600 cm −1 region of infrared (IR) spectra. The density of alkyl chains and crosslinking reactions affected the yield of tar. The aromaticity of char increased with an increasing pyrolysis temperature. The abundance of CO and COOH structures decreased drastically with increasing temperature. A lower concentration of active sites on high-temperature chars resulted in lower combustion reactivity compared to low-temperature chars. The C−O and C C groups decreased as the temperature increased possibly because of the aromatic condensation. The extent of aromatic substitution decreased up to 650 °C. At temperatures above 650 °C, the degree of aromaticity was strengthened and larger condensed aromatic nuclei were formed. Brunauer−Emmett−Teller (BET) surface area analysis revealed that high-temperature chars have significantly higher surface area compared to chars produced at low temperatures. However, the concentration of active sites was lower in high-temperature chars. Therefore, it can be concluded that diffusion was the main reaction mechanism in high-temperature chars.

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“…The reactivity index (R) of the char was calculated from eq 4. 25,26 This definition is widely used in the literature for comparison of reactivity of different coals…”

Section: Char Combustion Reactivitymentioning

confidence: 99%

Characteristics of Chars from Low-Temperature Pyrolysis of Lignite

et al. 2013

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“…The reactivity of char produced at the lowest pyrolysis temperature was found to be the highest, and the chars produced at the same pyrolysis temperature showed higher conversion at a given time with increasing gasification temperature. However, Wu et al contradicted the effect of pyrolysis temperature on the gasification reactivity of coal char in a CO 2 atmosphere as observed by Sawettaporn et al Li et al investigated experimentally Chinese bituminous coal char of particle size of less than 150 μm at a temperature range of 970–1150 °C in CO 2 . They reported that an increase in gasification temperature significantly increases carbon conversion and reduces the complete conversion time.…”

Section: Introductionmentioning

confidence: 99%

“…Varying physicochemical properties of different carbonaceous materials affect the gasification reactivity in the presence of CO 2 . Sawettaporn et al 7 carried out the experimental investigation on the gasification of two different types of coal chars (Ban Pu lignite A and Lampang sub-bituminous B) in the size range of 75−250 μm in a pure CO 2 atmosphere at the temperature range of 900−1100 °C. The char was prepared in the drop tube fixed-bed reactor under nitrogen flow in the temperature range of 500−900 °C.…”

Section: Introductionmentioning

confidence: 99%

Modeling and Experimental Studies on CO₂ Gasification of Coarse Coal Char Particle

et al. 2017

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Gasification study of a single Indian sub-bituminous coal char particle is carried out in the temperature range of 880−910 °C in a pure CO 2 atmosphere. Two temperatures, 900 and 800 °C, are used for char preparation, and the char obtained at higher temperature is found to be more reactive. A fully transient nonisothermal model is developed incorporating the reaction kinetics along with transport limitations. Spatial and temporal variation of thermo-physical properties like thermal conductivity, diffusivity, and density of the gas mixture and variable specific pore surface area and accessible porosity are included in the model. The model computation shows that the combined kinetics and heat transfer model is more effective to predict the experimental findings of the present authors and that reported in the literature. The simulation study is carried out to assess the effect of reaction temperature, particle size, and char reactivity on the particle temperature, conversion, gasification rate, and CO and CO 2 mass fractions within the porous volume of the particle.

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“…Thus, the investigation of coal gasification and combustion reactivity with a CO 2 atmosphere will be an essential feature to allow the understanding of the reaction mechanism and kinetics for the development of the gasification technology. The CO 2 gasification study on coal, biomass and other carbonaceous materials has been extensively investigated using thermogravimetric analysis (TGA) (Ergun 1956;Zhang et al 2006;Sawettaporn et al 2009;Kim et al 2011;Ng et al 2011;Yuan et al 2011;Lahijani et al 2012;Jing et al 2013;Kuznetsov et al 2013;Skodras 2013;Wei et al 2014). However, the CO 2 gasification data of Indian coals is found to be limited and in need of urgent attention (Saha et al 2012;Sahu 2013;Mishra et al 2014;Aranda et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Thermogravimetric and model-free kinetic studies on CO2 gasification of low-quality, high-sulphur Indian coals

et al. 2016

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Coal gasification with CO 2 has emerged as a cleaner and more efficient way for the production of energy, and it offers the advantages of CO 2 mitigation policies through simultaneous CO 2 sequestration. In the present investigation, a feasibility study on the gasification of three low-quality, high-sulphur coals from the northeastern region (NER) of India in a CO 2 atmosphere using thermogravimetric analysis (TGA-DTA) has been made in order to have a better understanding of the physical and chemical characteristics in the process of gasification of coal. Model-free kinetics was applied to determine the activation energies (E) and pre-exponential factors (A) of the CO 2 gasification process of the coals. Multivariate nonlinear regression analyses were performed to find out the formal mechanisms, kinetic model, and the corresponding kinetic triplets. The results revealed that coal gasification with CO 2 mainly occurs in the temperature range of 800 •-1400 • C and a maximum of at around 1100 • C. The reaction mechanisms responsible for CO 2 gasification of the coals were observed to be of the 'nth order with autocatalysis (CnB)' and 'nth order (Fn) mechanism'. The activation energy of the CO 2 gasification was found to be in the range 129.07-146.81 kJ mol −1. Keywords. Low-quality coal; Indian coal; CO 2-gasification; thermogravimetric analysis; model-free kinetics.

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CO2 gasification of Thai coal chars: Kinetics and reactivity studies

Cited by 18 publications

References 16 publications

Characteristics of Chars from Low-Temperature Pyrolysis of Lignite

Characteristics of Chars from Low-Temperature Pyrolysis of Lignite

Modeling and Experimental Studies on CO₂ Gasification of Coarse Coal Char Particle

Thermogravimetric and model-free kinetic studies on CO2 gasification of low-quality, high-sulphur Indian coals

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CO2 gasification of Thai coal chars: Kinetics and reactivity studies

Cited by 18 publications

References 16 publications

Characteristics of Chars from Low-Temperature Pyrolysis of Lignite

Characteristics of Chars from Low-Temperature Pyrolysis of Lignite

Modeling and Experimental Studies on CO2 Gasification of Coarse Coal Char Particle

Thermogravimetric and model-free kinetic studies on CO2 gasification of low-quality, high-sulphur Indian coals

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Modeling and Experimental Studies on CO₂ Gasification of Coarse Coal Char Particle