Article
Thermodynamics
Cheng Ma, Yuzhen Zhao, Tingting Lang, Chong Zou, Junxue Zhao, Zongcheng Miao
Summary: A low-nitrogen pyrolysis atmosphere is important for the clean and efficient use of low rank coal. The characteristics of low-rank coal pyrolyzed in a low-nitrogen atmosphere were studied using thermogravimetry-mass spectrometry. The results showed that low-nitrogen atmosphere promoted weight loss and increased the release of gas products compared to a nitrogen atmosphere. Physicochemical micro-structure analysis revealed that low-nitrogen atmosphere promoted the formation of dense, aromatic structures and ordered carbon structures. The combustion and CO2 gasification reactivity of char were reduced in the low-nitrogen atmosphere.
Article
Engineering, Environmental
Shuai Cheng, Yang Zhou, Kok Hoong Wong, Nai Yeen Gavin Lai, Zhennan Han
Summary: Pyrolysis of low-rank coal can improve coal quality, chemical feedstock and fuel production. The research shows that a novel reactor can produce char with more desirable combustion quality and lower ignition temperature compared to a conventional reactor. The chars derived from the novel reactor have a higher order of carbonaceous structure and active sites. The results indicate the potential to upgrade and utilize more low-rank coal effectively as a fuel source for energy sustainability.
JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING
(2023)
Article
Energy & Fuels
Changsheng Bu, Xu Zhao, Bo Leckner, Alberto Gomez-Barea, Daoyin Liu, Junguang Meng, Changqi Liu, Xinye Wang, Jubing Zhang, Guilin Piao
Summary: Adding active oxygen carriers to the inert bed material improves oxygen distribution in fluidized bed combustors. This method, known as Oxygen-carrier-aided combustion (OCAC), has been used in air combustion in FB boilers and shows potential for oxy-fuel combustion. Experimental analysis of OCAC in oxy-fuel combustion was conducted using different coals and oxygen carriers. The results demonstrate that the burnout temperature decreases with oxygen carriers, while ignition temperature remains stable. The effect of oxygen carriers on char combustion rate follows the sequence: steel slag < hematite < AR-Fe2O3, with stronger effects observed for lower rank fuels. Combustion kinetics of chars using oxygen carriers exhibit higher activation energy and pre-exponential factor compared to pure char, indicating enhanced oxygen transport to the carbon surface.
Article
Energy & Fuels
Lei Pang, Wenqi Zhong, Yingjuan Shao
Summary: This study experimentally and numerically investigated the combustion characteristics of char particles under pressurized oxy-fuel combustion conditions. The experimental results showed that higher devolatilization pressure led to larger mean pore sizes and specific surface areas of char particles. The simulation results further confirmed that using char samples prepared under atmospheric N2 conditions underestimated char combustion reactivity and peak temperature.
Article
Engineering, Environmental
Lei Pang, Yingjuan Shao, Wenqi Zhong, Hao Liu
Summary: Pressurized oxy-coal combustion has potential for high efficiency and low cost CO2 capture. Increased pressure and oxygen concentration reduce burnout time of char particles and improve their reactivity and temperature. A combustion model shows pressure's impact on char burnout time.
CHEMICAL ENGINEERING JOURNAL
(2021)
Article
Energy & Fuels
Xin Zhang, Jun Zhang, Rui Guo, Qiang Xiao, Yawei Feng, Huan Cheng
Summary: Utilization of high-reactivity coke is effective in achieving low carbon blast furnace. A method for preparing high-reactivity metallurgical coke using low-rank coal is proposed. The coke prepared has high compressive strength and exhibits high reaction rate and strength after iso-solution loss. Various characteristics of the coke were investigated, such as reaction rate, microcrystalline structure, optical structure, porosity, pore distribution, and mineral composition.
Article
Chemistry, Multidisciplinary
Yang Geng, Jinfeng Bai, Yang Liu, Xiangyun Zhong, Chao Li, Yang Liu, Zhihua Zhang, Yaru Zhang
Summary: The experimental study focused on the thermochemical reaction characteristics of different concentrations of phenol water and gasification-coke at 1000 degrees C. Results showed that increasing phenol water concentration enhanced the reactivity of gasification-coke, leading to higher syngas yield and heating value, but also causing damage to the carbon structure of gasification-coke.
REACTION CHEMISTRY & ENGINEERING
(2021)
Article
Energy & Fuels
Siqi Liu, Guangqing Zhu, Yanqing Niu, Liping Wen, Yu Lei, Denghui Wang, Shi'en Hui
Summary: This study investigates the relationship between char fragmentation/mineral coalescence and PM formation, finding that char fragmentation significantly increases the number of fine ash particles while dense char structure disadvantages char fragmentation but enhances mineral coalescence. The distribution of fly ash at different temperatures is influenced by the percolation theory, with particles at higher temperatures mainly undergoing perimeter fragmentation. The effect of ash content is more related to the distribution of mineral grains within char particles.
Article
Energy & Fuels
Xiaoqian Liu, Yinhe Liu, Qiang Lv, Bo Wang, Yandi Zhang, Yao Zhou
Summary: Oxy-fuel combustion is a promising carbon capture technology that can alleviate the slagging and fouling issues in high alkali Zhundong coal-fired boilers. However, the existing kinetic models often neglect the gasification reactions by CO2 and H2O, leading to insufficient prediction accuracy. This study established a co-gasification reaction model and proposed a novel method considering the chemical cooling effect to calculate the char-O-2 reaction rate under high temperature and complex atmosphere. A comprehensive high temperature gasification reaction model was successfully developed.
Article
Energy & Fuels
Meng Ma, Jiaofei Wang, Yonghui Bai, Peng Lv, Xudong Song, Weiguang Su, Lu Ding, Juntao Wei, Guangsuo Yu
Summary: Volatile-char interactions affect the chemical structure and reactivity of coal char, with O-containing functional groups playing an important role in char reactivity. The decrease in gasification reactivity due to volatile-char interactions is attributed to the decrease in aromatic C-O and C=O, and the increase in graphite carbon structures.
Article
Energy & Fuels
Yaxin Ge, Saiman Ding, Xiangrui Kong, Efthymios Kantarelis, Klas Engvall, Jan B. C. Pettersson
Summary: This study characterizes the alkali release during CO2 gasification of biochar using a surface ionization method combined with thermogravimetric analysis. The results show that alkali release rate from wood char decreases as char conversion proceeds, but increases significantly when conversion approaches completion. On the other hand, alkali release from straw char is much higher and decreases continuously during gasification. High temperature and high CO2 concentration enhance alkali release and char reactivity.
Article
Chemistry, Analytical
He Yang, Yahui Yang, Sarma V. Pisupati, Lijun Jin, Yang Li, Haoquan Hu
Summary: The trend of changing N-2 adsorption specific surface area during pyrolysis is significantly affected by coal rank and the arrangement of planar polycyclic aromatic structures in char. Two exponents introduced in the model can predict the specific surface area of various coals and a correlation between the fraction ratio of crosslinked metaplast to volatile yield and the order degree of aromatic structure arrangement is proposed. The model can also predict transition characteristics of subbituminous coal based on temperature and heating rates.
JOURNAL OF ANALYTICAL AND APPLIED PYROLYSIS
(2021)
Article
Thermodynamics
Samar Das, Pranay Kumar Sarkar, Sadhan Mahapatra
Summary: The study investigated single particle combustion behaviors of coal-biomass fuel mixtures, showing that rice husk had the longest burning time due to its higher ash content and particle density. Sawdust had a higher ignition mass flux compared to rice husk and wood particles, attributed to its higher volatile content. The primary controlling parameters for fuel conversion in co-combustion systems were found to be particle size, surface area/volume, and particle density.
Article
Engineering, Environmental
Guo-chang Song, Wen-ting Xu, Xing-yu Yang, Qiang Song
Summary: The retention of arsenic during coal combustion is important for controlling its emissions. Both devolatilization and char combustion processes contribute to the release of arsenic, with a portion being retained as gaseous form and another portion being retained by minerals in solid products.
PROCESS SAFETY AND ENVIRONMENTAL PROTECTION
(2022)
Article
Energy & Fuels
Wenda Zhang, Shaozeng Sun, Hanlin Zhu, Linyao Zhang, Yijun Zhao, Pengxiang Wang
Summary: The study reports the formation rules of gas products and evolution characteristics of physicochemical structure during the pyrolysis of Shenhua bituminous coal under different pressures, temperatures, and residence times. Increasing pressure, temperature, and residence time promote the release of carbon and nitrogen-containing gases, affecting the physicochemical structure of the char products.