Article
Energy & Fuels
Pu Hong, Lin Li, Yuanqiang Duan, Yueming Wang, Lunbo Duan
Summary: Oxy-fuel combustion is an important means of reducing CO2 emissions in coal-fired power plants. This study explores the influence of the gasification reaction on oxy-fuel combustion and decouples the contribution ratio of the gasification reaction. The results show that increasing pressure, temperature, and oxygen concentration promotes the combustion process and increases the combustion rate. The problem of low combustion rate in oxy-fuel combustion can be solved by increasing the O2 concentration.
Article
Thermodynamics
Christopher R. Shaddix, Ethan S. Hecht, Cristina Gonzalo-Tirado, Brian S. Haynes
Summary: Previous research has shown that CO2 and H2O gasification reactions play a significant role in the combustion of pulverized coal (pc) char, especially in oxy-fuel environments. This study aims to quantify the influence of CO2 gasification reaction by combining experimental measurements and simulations. The results demonstrate a consistent relationship between the gasification reaction rate and the char particle temperatures and burnout rates in oxy-fuel combustion environments.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(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
Ming Lei, Yanchao Zhang, Dikun Hong, Bin Ye
Summary: In this study, pressurized coal pyrolysis and oxy-fuel combustion experiments were conducted to investigate the migration and transformation characteristics of nitrogen and sulfur. The results showed that high pressure inhibited the release of nitrogen and sulfur, while elevated temperature promoted their decomposition and conversion. CO2 gasification facilitated the release of volatiles and decomposition of nitrogen and sulfur-containing functional groups in coal. Pressurized oxy-fuel combustion resulted in lower emissions of NO, NO2, and SO2 compared to air combustion.
Article
Thermodynamics
Yongbo Du, Pengfei Yu, Junxiong Wang, Jinping Zhang, Chang'an Wang, Defu Che
Summary: The study investigated the competitive behavior of O-2 and CO2 reactions on char active sites, revealing that in an O-2/CO2 environment, the contribution of O-2 to char consumption is equal to that of the CO2 reaction. However, with increasing temperature and O-2 fraction, the CO2 reaction is further inhibited.
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
(2021)
Article
Energy & Fuels
Jianan Qi, Cuigang Fan, Songgeng Li
Summary: The impacts of temperature and oxygen concentration on char structure evolution during pyrolysis were revealed using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and BET characterization techniques. Char prepared under oxygen atmosphere showed higher reactivity compared to that under inert (N2) atmosphere, with the presence of oxygen reducing char graphitization at high temperatures. The presence of oxygen in pyrolysis improved pore volume and specific surface area, with a critical oxygen concentration observed at high pyrolysis temperatures.
Article
Chemistry, Applied
Yi Chen, Zhongyang Luo, Mengxiang Fang, Kejian Lv, Jiansheng Zhou
Summary: The study found that under high-temperature pyrolysis conditions, controlling the heating rate, volatile-char interaction, and CH4 atmosphere can effectively enhance alkali metal pretreatment and eliminate carbon engulfment issues.
FUEL PROCESSING TECHNOLOGY
(2022)
Article
Engineering, Environmental
Kagiso Bikane, Jie Yu, Ravi Shankar, Xiangyi Long, Nigel Paterson, Marcos Millan
Summary: This study investigates the gasification kinetics of Morupule coal in atmospheric pressure CO2 and the structural evolution of residual chars. The research shows that gasification reaction rates are high, with little impact on the bulk chemical structure of chars but significant changes in surface chemistry. Residual chars from gasification experiments exhibit lower combustion reactivity compared to chars produced under inert pyrolysis conditions.
CHEMICAL ENGINEERING JOURNAL
(2021)
Article
Thermodynamics
Sandile Fakudze, Yu Zhang, Yingyuan Wei, Yueh-Heng Li, Jianqiang Chen, Jiaxin Wang, Jiangang Han
Summary: The optimization of oxycombustion conditions for pomelo peel derived hydrochar (PPH) and coal blends was performed using the Taguchi method. The results showed that the best performances were achieved with a blending ratio of 5:5 (coal:PPH). Experimental results also indicated that these conditions were optimal for the best combustibility. Additionally, the blended coal/hydrochar fuel exhibited reduced CO2 peak intensity compared to unblended coal.
Article
Energy & Fuels
Shyamal Bhunia, Anup Kumar Sadhukhan, Rohit Kumar Singh, Parthapratim Gupta
Summary: The study focuses on the combustion kinetics of devolatilized coal char fines in oxy-fuel environments, showing that oxygen concentration has a strong influence on kinetic parameters. Different kinetic models were used to estimate the activation energy for three types of coal char, indicating that combustion behavior varies depending on the oxygen concentration and coal type. SEM images and BET surface area analysis were conducted to justify the different reaction mechanisms followed by various coal chars.
ENERGY SOURCES PART A-RECOVERY UTILIZATION AND ENVIRONMENTAL EFFECTS
(2021)
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
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
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
Energy & Fuels
Dikun Hong, Liang Liu, Chunbo Wang, Ting Si, Xin Guo
Summary: An atomistic coal char representation was constructed via ReaxFF MD simulation, investigating the combustion and gasification characteristics of the char. The activation energies obtained for various reactions were in good agreement with experimental data, revealing the generation of large amounts of C2 species during char-H2O gasification.
Article
Thermodynamics
Xiaohong Huang, Fan Hu, Xuhui Liu, Zhaohui Liu
Summary: Accurate assessment of the structural characteristics and reactivity of coal char is crucial for burner design. In this study, the physical-chemical structures and reactivities of low-volatile coal chars were investigated under different conditions. It was found that the CO2 content affected the char yield and specific surface area, and the chemical structures were influenced by different conditions. Moreover, the physical structure characteristics of coal char played a leading role in the apparent reactivity.
Article
Chemistry, Analytical
Guanshuai Zhang, Shanjian Liu, Dongmei Bi, Zhisen He, Jia Liu, Yinjiao Liu
Summary: Hydrogen peroxide pretreatment was applied for fast pyrolysis of corn stalks, and it was found that the pretreatment effectively promoted lignin depolymerization and decreased the reaction activation energy. The pretreatment also increased the cellulose content and removed alkali and alkaline earth metals from the biomass. The pH of the hydrogen peroxide solution affected the removal of lignin and ash by the pretreatment, and the composition of bio-oil changed significantly, with a significant increase in the relative content of levoglucosan after pretreatment.
JOURNAL OF ANALYTICAL AND APPLIED PYROLYSIS
(2024)
