Preheating and combustion characteristics of anthracite under O2/N2, O2/CO2 and O2/CO2/H2O atmospheres

Zhang, Xiaoyu; Zhu, Shujun; Zhu, Jianguo; Liu, Yuhua; Zhang, Jiahang; Hui, Jicheng; Ding, Hanfeng; Cao, Xiaoyang; Lyu, Qinggang

doi:10.1016/j.energy.2023.127419

Cited by 12 publications

(4 citation statements)

References 48 publications

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“…The reason was that during the process of fuel preheating in the CFB, some gases were released from the inside of the particles, which also made the structure of the inner pores develop with a large specific surface area. Zhang et al [24] preheated anthracite with a specific surface area of 3.53 m 2 /g in a CFB and found that the specific surface area of the preheated char was enlarged to 67.1 m 2 /g, increasing by 19 times. The developed inner pores could facilitate the progress of the reactions, such as combustion or gasification.…”

Section: Kinetic Analysis Of the Semi-coke And Preheated Charmentioning

confidence: 99%

Preheating Analysis of Semi-Coke in a Circulating Fluidized Bed and Its Kinetic Characteristics

2023

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Semi-coke has difficulties with stable ignition and high-efficiency combustion due to its low volatile content. Preheating in a circulating fluidized bed before combustion offers a novel method for the improvement of fuel properties. During preheating, the semi-coke was converted to preheated fuel composed of coal gas and preheated char. When increasing the preheating temperature, the ratio of CO/CO2 in the coal gas significantly increased, while the ratio of CH4/CO2 remained almost unchanged. After preheating, the release ratios for different species from the semi-coke followed the order C >H > N > S. Thermogravimetric analysis was used to evaluate the kinetic characteristics. We found that the ignition and burnout temperatures of the preheated char decreased compared to those of the semi-coke, and the reaction rate constant for the preheated char increased by 20 times. Three models were used to predict the variations in the conversion ratio with time, and the modified volumetric reaction model showed good agreement with the experiment. This investigation provides support for better developing preheating combustion technology in the future.

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Section: Kinetic Analysis Of the Semi-coke And Preheated Charmentioning

confidence: 99%

Preheating Analysis of Semi-Coke in a Circulating Fluidized Bed and Its Kinetic Characteristics

2023

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“…The increase in the chemical reactivity of solid carbon can be achieved through the partial gasification process, which includes pyrolysis reactions, combustion reactions, and gasification reactions, in the circulating fluidized bed (CFB) reactor. , Activated char obtained from the CFB partial gasification process exhibits notable improvements compared to raw materials, including a larger specific surface area, better pore structure development, reduced graphitization, and a higher concentration of defective carbon site. − These changes contribute to a higher CO 2 reduction capability of the char. Su et al demonstrated that the specific surface area, pore volume, and pore diameter of char were larger than those of raw coal, suggesting that the partial gasification process in CFB optimizes the pore structure.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on the Improvement of Char Physicochemical Properties and Reactivity by Activation Process in CFB

Zhang,

Wang,

Liang

et al. 2024

ACS Omega

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Solid carbon can be transformed into activated char with higher reactivity through the activation process in a circulating fluidized bed (CFB) to improve the Boudouard reaction. A new technology for reducing CO 2 , the activated-reduction technology, was proposed. In order to investigate the influence of relevant parameters (carbon dioxide addition, oxygen concentration, and O 2 /C) of the activation process on the physicochemical properties and reactivity of activated char, the experiments were carried out on a bench-scale CFB. The relationship between the parameters and the reactivity of activated char is explored. The result shows that compared with the raw coal, the pore structure of activated char is developed, the number of active sites increases, the degree of graphitization decreases, and higher reactivity is possessed. For the activation process, less of the O 2 /C and moderate oxygen concentration promote the increase in activated char reactivity, which is conducive to the reduction of CO 2 . The results of the correlation discussion show that the reactivity is difficult to be characterized by a single simple parameter. The reactive specific surface area (RSSA) obtained by multiplying the mesoporous specific surface area and I D3+D4 /I all has a good effect on describing the reactivity.

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“…They have indicated that, in comparison to surface area, the impact of the active site is more significant on reactivity. The active sites or carbon structure in char is commonly characterized using Raman spectra [14][15][16]. Guizani et al [17] observed the relationship between carbon structure and the reactivity of char and found that the reactivity index (R index ) has a good linear relationship with I V /I D .…”

Section: Introductionmentioning

confidence: 99%

“…During the gasification process in the circulating fluidized bed (CFB), the specific surface area of the raw material increases, and the concentration of stable graphite structure decreases [19][20][21]. In this study, a CFB was used as the activation unit, which enhances the reactivity of carbon-based materials and preheats carbon-based materials and gases [14,22]. The downdraft reactor (DR) was used as the reduction unit, providing a high-temperature zone for the occurrence of the Boudouard reaction.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on the Thermal Reduction of CO2 by Activated Solid Carbon-Based Fuels

Zhang,

Liang,

Zhu

et al. 2024

Energies

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For achieving CO2 thermal reduction, a technology combining solid carbon activation and high-temperature CO2 reduction was proposed, named as activated-reduction technology. In this study, this technology is realized by using a circulating fluidized bed and downdraft reactor. Reduced agent parameters (O2/C and CO2 concentration) greatly affect the reduction effect of CO2. In addition, the effect of the activation process on different carbon-based materials can help to broaden the range of carbon-based materials used for CO2 reduction, which is also an important issue. The following three points have been studied through experiments: (1) the influence of the characteristics of the reduced agent (CO2 concentration and O2/C) on CO2 reduction; (2) the performance of different chars in CO2 reduction; and (3) the activation effect of solid carbon. The activation process can develop the pore structure of coal gasification char and transform it into activated char with higher reactivity. The CO concentration in the tail gas is a crucial factor limiting the effectiveness of CO2 reduction, with an experimentally determined upper limit of around 55% at 1200 °C. If CO concentration is far from the upper limit, temperature becomes the significant influencing factor. When the reduced agent O2/C is 0.18, the highest net CO2 reduction of 0.021 Nm3/kg is achieved at 60% CO2 concentration. When the reduced agent CO2 concentration is 50%, the highest net CO2 reduction of 0.065 Nm3/kg is achieved at 0.22 O2/C. Compared with CPGC, YHGC has higher reactivity and is more suitable for CO2 reduction. The activation process helps to reduce the differences between raw materials.

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Preheating and combustion characteristics of anthracite under O2/N2, O2/CO2 and O2/CO2/H2O atmospheres

Cited by 12 publications

References 48 publications

Preheating Analysis of Semi-Coke in a Circulating Fluidized Bed and Its Kinetic Characteristics

Preheating Analysis of Semi-Coke in a Circulating Fluidized Bed and Its Kinetic Characteristics

Experimental Study on the Improvement of Char Physicochemical Properties and Reactivity by Activation Process in CFB

Experimental Study on the Thermal Reduction of CO2 by Activated Solid Carbon-Based Fuels

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