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A Victorian brown coal (68.5% C), a Chinese high-volatile Shenmu bituminous coal (82.3% C) and a Chinese low-volatile Dongshan bituminous coal (90% C) were gasified in a fluidised-bed/fixed-bed reactor at 800°C in atmospheres containing 15% H 2 O, 2000ppm O 2 or 15% H 2 O+2000ppm O 2 . While the gasification of these coals in 2000ppm O 2 converted less than...
In a coal gasifier interactions between volatiles and char are significant. The partly reducing conditions in a gasifier would mean the presence of high concentration of partial oxidation products and radicals surrounding the char particles. Currently, little is known about the effects of in situ volatile–char interactions on the conversion of char-N. This study examines the effect of in situ volatile–char...
Ash interacts strongly with char and volatiles in a gasifier, especially in a fluidised-bed gasifier. This study aims to investigate the effects of ash or ash-forming species on the conversion of fuel-N during gasification. A Victorian (Loy Yang) brown coal and a sugar cane trash were gasified in two novel fluidised-bed/fixed-bed reactors where the interactions of ash with char and/or volatiles could...
Effects of pressure on the formation of HCN and NH 3 during the pyrolysis and gasification of Loy Yang brown coal in steam were investigated using a pressurised drop-tube/fixed-bed reactor. The NH 3 yield increased with increasing pressure during both pyrolysis and gasification. Increasing pressure selectively favours the formation of NH 3 at the expenses of other N-containing...
Biomass-nitrogen conversion during the pyrolysis and gasification of a cane trash in steam was investigated using a fluidised-bed/fixed-bed reactor and a fluidised-bed/tubular reactor. Our results indicate that the thermal cracking of volatile-N is the main route of HCN formation although the thermal cracking of char-N also contributes to the formation of HCN. There are three major routes of NH ...
Formation of NH 3 , HCN, NO and NO 2 from the gasification of a Chinese coal (Shenmu) in a fluidised-bed/fixed-bed reactor in 4.1% O 2 in argon was investigated. The presence of O 2 even at 673 or 773 K could lead to the gradual gasification of char to form HCN and NH 3 . The yields of NH 3 and HCN showed maxima at about 773 K, amounting to 40% of coal-N...
Our results indicate that the gas atmosphere surrounding coal/char particles can greatly affect the formation of NH 3 and HCN through its influence on the availability of H radicals. Based on our results, it is believed that the chemisorption of CO 2 on the nascent char surface can consume H radicals or block the access of N-sites by H radicals for the formation of NH 3 and...
A sewage sludge sample from a wastewater treatment plant in China was pyrolysed in a fluidised-bed/fixed-bed reactor and in a fluidised-bed/tubular reactor. HCN was found to be the main NO x precursor, representing up to about 80% of the nitrogen present in the sludge. The thermal cracking of volatiles is the main route of HCN formation. NH 3 was also an important NO x precursor...
The formation of HCN and NH 3 from the pyrolysis of a small set of Chinese and Australian coals were studied using a novel fluidised-bed/fixed-bed reactor and a fluidised-bed/tubular reactor. The fluidised-bed/fixed-bed reactor has some features of a fluidised-bed reactor and of a fixed-bed reactor, allowing the evaluation of the effects of coal properties on the formation of HCN and NH ...
The formation of HCN and NH 3 from the pyrolysis of coal (and biomass) is discussed based on our experimental data as well as the data in the literature, including the pyrolysis of N-containing pyrrolic and pyridinic model compounds reported in the literature. The pyrolysis of the model compounds and the thermal cracking of coal pyrolysis volatiles appear to be in good qualitative agreement...
The formation of HCN and NH 3 during the pyrolysis of a biomass (bagasse) and a set of rank-ordered coal samples has been studied in a novel reactor. The reactor has some features of both a drop-tube reactor and a fixed-bed reactor: the reactor allows the coal/biomass particles to be heated up rapidly as well as to be held for a pre-specified period of time at peak temperature. The experimental...
A Victorian brown coal was pyrolysed in a quartz reactor. The reactor has some features of a drop-tube reactor and of a fixed-bed reactor, capable of operating at fast and slow heating rates. The yield of HCN was found to change with gas flow rate and coal feeding rate, indicating that HCN and/or its precursors could interact significantly with the nascent char to be incorporated into char as soot...
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