Estimation of synergetic effects of CO2 in high ash coal-char steam gasification

Jayaraman, K.; Gökalp, İskender; Jeyakumar, S.

doi:10.1016/j.applthermaleng.2016.09.011

Cited by 39 publications

(23 citation statements)

References 44 publications

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“…The slopes of the relationships calculated for the VM and the RPM models are an almost parallel line which indicates that almost similar activation energy values are calculated from these models. The activation energy of the steam gasification is varying from 129 to 177 kJmol −1 using GM model, and around 110 kJmol −1 using RPM model, and the reaction rate constants from 4 × 10 3 to 3 × 10 6 min −1 which are similar to values obtained in previous studies [33,35,36,43,44,47,64,71] . It can be observed that the activation energy of VM model is always higher irrespective of the char generation method.…”

Section: Indian Coalssupporting

confidence: 79%

“…Investigations concerning the reactions of H 2 O and CO 2 with high ash chars during gasification are quite limited. According to reported results [29,43,47,[58][59][60][61][62][63][64], possiblility of two surface reaction mechanisms to be emerged. First approach claims that C─H 2 O and C─CO 2 reactions takes place in common active sites, whereas the another approach asserts that the reaction of CO 2 and steam happen in separate active sites.…”

Section: Figure 13amentioning

confidence: 99%

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Pyrolysis and Gasification Characteristics of High Ash Indian and Turkish Coals

Kandasamy¹,

Gökalp²

2018

Gasification for Low-Grade Feedstock

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Pyrolysis and gasification studies of Indian and Turkish high ash coal samples have been performed using coupled TGA-MS method. Coal samples were heated in the TGA apparatus in an argon, steam, CO 2 and blended mixtures of CO2 and steam in a temperature range from 25-1250°C with heating rates from 35 to 1000 K/min. Gas evolution measurements is performed using the mass spectrometry system. During the devolatilisation stage (350-700°C), the maximum mass loss has observed in which O 2 , CO 2 , CO, H 2 and small amount of hydrocarbon compounds are released. Char gasification is mainly influenced by operating conditions such as heating rate and reaction temperature and also the char production method, its physical structure and size and chemical composition of the char. The steam and CO 2 gasification rates of the chars are carried out at the temperatures of 850, 900, 950, and 1000°C. Three kinetic models are applied to describe the char conversion rates: volumetric model, grain model, and random pore model. The activation energy of Indian coal-char is varying from 122 to 177 kJ mol-1 under steam gasification and from 130 to 214 kJ mol-1 for CO 2 gasification. The activation energy for char-steam gasification is 156-173 kJ/ mol, whereas in the steam blended with CO 2 gasification, it ranges between 162 and 196 kJ/ mol for 3 mm particles. Similar trends are observed for the Arrhenius constant values for both sized particles.

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Section: Indian Coalssupporting

confidence: 79%

Section: Figure 13amentioning

confidence: 99%

Pyrolysis and Gasification Characteristics of High Ash Indian and Turkish Coals

Kandasamy¹,

Gökalp²

2018

Gasification for Low-Grade Feedstock

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“…The activation energies in this study (around 162 and 66 kJ/mol) are different from each other for the same kind of chars, which may be caused by the different ash contents in chars. Also, Jayaraman and his colleagues' study about estimation of synergetic effects of steam gasification for a similar type of Turkish coal [26]. In a different study about steam gasification of Victorian brown coal chars, activation energies are very similar to Zonguldak char while the compositions of the chars are very similar [27].…”

Section: Figure 6 Rate Expression With Arrhenius Plotsmentioning

confidence: 98%

Experimental Analysis and Kinetic Modelling for Steam Gasification of the Turkish Lignites

Güney

Koyun

2020

Journal of Thermal Engineering

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During the last decades, the importance of structural parameters has been increased because the models which have been developed using structural parameter can define the gasification process effectively. In this study, structural parameters, rates of conversion and activation energies of Zonguldak coal and Beypazari lignite have obtained. The samples of Zonguldak coal and Beypazari lignite used in this study have different characteristics. Pore dimensions, distribution of pores and surface areas were used as structural parameters. Suitable kinetic parameters were determined by fitting the gasification model to experimental data. The random pore model was used to define these kinetic parameters. The data were taken from experiments of Balci and Durusoy and the results obtained from Zonguldak coal and Beypazarı lignite pyrolysed in a vertical tube heated from outside by an inert gas and gasified with steam at elevated temperatures (between 700 °C and 1000 °C) were used in the model.

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“…Many researchers [21][22][23][24] have devised reaction models of char-carbon dioxide (CO 2 ) and char-water vapor (H 2 O) separately to explore the coal gasification reaction mechanism. The kinetics of both char-CO 2 and char-H 2 O gasification have also been studied in detail [25][26][27][28]. However, these studies, carried out in systems with a sole gasifying agent, could hardly be applied in systems where the mixtures of carbon dioxide, water vapor, carbon monoxide (CO), and hydrogen (H 2 ) usually serve as gasifying agents in actual industry.…”

Section: Introductionmentioning

confidence: 99%

Gasification Kinetics of Bituminous Coal Char in the Mixture of CO2, H2O, CO, and H2

2019

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The gasification kinetics of bituminous coal char was investigated in a mixture of CO2, H2O, CO, H2, and N2 under isothermal conditions. In addition, the impacts of gasification temperature, gasification time, and gas composition on the gasification process were analyzed. As the experimental results suggest, there is a significant increase of the carbon conversion degree of bituminous coal char not just when gasification temperature and time increase, but also when H2 and CO concentration decreases. The kinetics of bituminous coal char in the gasification process was successfully modeled as a shrinking unreacted core. It is concluded that the gasification of bituminous coal char is controlled by an internal chemical reaction in the early stage and diffusion in the later stage. The activation energies of bituminous coal char gasification for different stages were studied. Moreover, it is proposed for the first time, to our knowledge, that the diffusion-control step is significantly shortened with the decrease of the CO2/H2O ratio. As scanning-electron-microscopy results suggest, bituminous coal char gasified in CO2/H2O = 1/3 atmosphere has numerous inner pores (0–5 m). Therefore, in the process of gasification, the inner pores provide a gas channel that reduces the gas diffusion resistance and thus shortens the diffusion-control step. These results can serve as a reference for industrialized application of the technology of coal gasification direct reduced iron.

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Estimation of synergetic effects of CO2 in high ash coal-char steam gasification

Cited by 39 publications

References 44 publications

Pyrolysis and Gasification Characteristics of High Ash Indian and Turkish Coals

Pyrolysis and Gasification Characteristics of High Ash Indian and Turkish Coals

Experimental Analysis and Kinetic Modelling for Steam Gasification of the Turkish Lignites

Gasification Kinetics of Bituminous Coal Char in the Mixture of CO2, H2O, CO, and H2

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