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Formation mechanism of solid product produced from co-pyrolysis of Pingdingshan lean coal with organic

Xiangchun Liu, Jun Hu, Ruilun Xie, Bin Fang, Ping Cui

《化学科学与工程前沿（英文）》 2021年第15卷第2期页码 363-372 doi: 10.1007/s11705-020-1944-7

摘要： A mixture of Pingdingshan lean coal and acid-treated Huadian oil shale was co-pyrolyzed in a drop-tube fixed-bed reactor in the temperature range of 300 °C–450 °C. To reveal the formation mechanism of the solid co-pyrolysis product, changes in some physicochemical properties were investigated, using analysis by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, pore analysis, thermogravimetry, and electron spin resonance. X-ray diffraction showed that the lattice plane spacing for the co-pyrolyzed mixture decreased from 0.357 nm to 0.346 nm and the average stacking height increased from 1.509 nm to 1.980 nm in the temperature range of 300 °C–450 °C, suggesting that pyrolysis treatment increased its degree of metamorphism. The amount of oxygen-containing functional groups and pore volume decreased with increasing temperature. Thermogravimetry and electron spin resonance results showed that synergistic effects occurred during the co-pyrolysis process. A formation mechanism for the solid product was proposed. Hydrogen-rich radicals generated from the pyrolysis of the oil shale were trapped by hydrogen-poor macromolecular radicals of the intermediate metaplast produced from coal pyrolysis, thereby increasing the yield of solid product.

关键词： co-pyrolysis coal oil shale electron spin resonance mechanism

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Preliminary study of trace element emissions and control during coal combustion

ZHANG Junying, ZHAO Yongchun, DING Feng, ZENG Hancai, ZHENG Chuguang

《能源前沿（英文）》 2007年第1卷第3期页码 273-279 doi: 10.1007/s11708-007-0038-2

摘要： Hazardous trace element emissions have caused serious harm to human health in China. Several typical high-toxic trace element coals were collected from different districts and were used to investigate the emission characteristics of toxic trace elements (As, Se, Cr, Hg) and to explore preliminary control methods. Coal combustion tests were conducted in several bench-scale furnaces including drop tube furnace (DTF), circulating fluidized bed (CFB) combustion furnace, and fixed-bed combustion furnace. Calcium oxide was used to control the emission of arsenic and selenium. The granular activated carbons (AC) and activated-carbon fibers (ACF) were used to remove mercury in the flue gas from coal combustion. The chemical composition and trace element contents of ash and particulate matter (PM) were determined by X-ray fluorescence (XRF) spectrometry and inductively coupled plasma-atomic emission spectrometry (ICP-AES), respectively. The speciation and concentration of mercury were investigated using the Ontario-Hydro method. X-ray diffraction spectrometry (XRD) was used to determine the mineral composition of production during combustion experiments. With the addition of a calcium-based sorbent, arsenic concentration in PM sharply decreased from 0.25–0.11 mg/m. In fixed-bed combustion of coal, the retention rates of selenium volatiles were between 11.6% and 50.7% using lime. In the circulating fluidized-bed combustion of coal, the content of selenium in ash from the chimney was reduced to one-fourth of its original value and that in leaching water from the chimney decreased by two orders of magnitude using lime. Calcium-based sorbent is an effective additive to control the emission of As and Se during coal combustion. The emission of chromium is influenced by the occurrence mode of Cr in coal. Chromium emission in PM during coal combustion is 55.5 and 34.7 μg/m for Shenbei coal and mixed Pingdingshan coal, respectively. The adsorptive capacity of granular activated carbon for Hg is significantly enhanced through ZnCl-impregnation. The activated carbon fibers showed decent efficiency in mercury adsorption, on which surface oxygen complex showed positive effects on mercury adsorption.

关键词： Pingdingshan occurrence plasma-atomic emission chemical composition Several typical