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Norman F.,Adinex NV | Berghmans J.,Catholic University of Leuven | Verplaetsen F.,Adinex NV
Procedia Engineering | Year: 2012

The ability to mix pulverised coal with oxygen at concentrations greater than the currently applied 21% may well provide advantages for burner design in oxy/coal fired systems. However the risk of dust explosions increases significantly with increasing oxygen concentration and temperature. In this study the influence of enriched oxygen concentrations is researched on the dust explosion characteristics of Indonesian (Sebuku) high volatile bituminous coal dust and on Pittsburgh Coal n°8. Both ignition sensitivity characteristics (minimum ignition energy and minimum ignition temperatures) and explosion severity characteristics (maximum explosion pressure, Pmax, and maximum rate of pressure rise, Kst ) are investigated. © 2012 The Authors. Published by Elsevier Ltd. Source


Norman F.,Adinex NV | Berghmans J.,Catholic University of Leuven | Verplaetsen F.,Adinex NV
Chemical Engineering Transactions | Year: 2013

In oxy/fuel combustion of coal, the pulverised coal is burned with oxygen at concentrations greater than the currently allowed value of 21 %. This may well provide advantages in carbon sequestration against other technologies such as pre- and post-combustion capture. However the risk of dust explosions increases significantly with increasing oxygen concentration and temperature. In this study the influence of enriched oxygen concentrations is researched on the dust explosion characteristics of Indonesian (Sebuku) coal dust and of Pittsburgh coal n8. First the ignition sensitivity characteristics (minimum ignition energy and minimum ignition temperatures) and explosion severity characteristics (maximum explosion pressure, Pmax, and maximum rate of pressure rise, Kst) are determined in air. Thereafter the minimum ignition energy is determined of both coals in an oxygen enriched CO2 atmosphere. The minimum ignition energy in air of the Sebuku coal was equal to 55 mJ, while the minimum ignition energy of the Pittsburgh coal was higher than 1000 mJ. The ignition sensitivity in a 30 vol% O2 in CO2 mixture was in good agreement to the ignition sensitivity in air. In a 50 vol% O2 in CO2 mixture the ignition energy decreased significantly to a value of 1.4 mJ for the Sebuku coal and 4.7 mJ for the Pittsburgh coal n̊8. © 2013, AIDIC Servizi S.r.l. Source


Wu D.,Catholic University of Leuven | Huang X.,Imperial College London | Norman F.,Adinex NV | Verplaetsen F.,Adinex NV | And 2 more authors.
Fuel | Year: 2015

For the oxy-coal combustion, the accumulation of coal dust in the system has a fire risk of self-ignition. Therefore, understanding the ignition dynamics of coal dust deposits in oxygen-enriched environment is essential for the prevention of fire and dust explosion. In this work, both hot-oven and hot-plate tests were conducted to study the self-ignition behaviour of coal dusts in O2/CO2 ambient with O2 mole fraction from 21% to 50%. Three coal dusts: Indonesian Sebuku coal, Pittsburgh No. 8 coal and South African coal were tested with different sizes. Experimental results revealed that the self-ignition risk increased significantly with the increasing O2 mole fraction: reducing both the critical ignition temperature (10°C in hot-oven test and 40°C in hot-plate test) and the ignition delay time. Comparatively, the inhibiting effect of CO2 was found to be small for self-ignition. In addition, a modified Frank-Kamenetzkii analysis was proposed to explain all measured critical ignition temperatures, and the genetic algorithm was used to determine kinetic parameters of the one-step global reaction. The analysis showed that as the coal maturity/rank increased, both the self-ignition risk and the sensitivity to oxidation decreased, along with the decreasing apparent activation energy and pre-exponential factor. Such trend did not change with the ambient oxygen condition for all three coal dusts. These results improve our understanding of the self-ignition behaviour and the fire risk of coal dust in the oxy-fuel combustion system. © 2015 Published by Elsevier Ltd. Source


Wu D.,Catholic University of Leuven | Norman F.,Adinex NV | Verplaetsen F.,Adinex NV | Van den Bulck E.,Catholic University of Leuven
Journal of Hazardous Materials | Year: 2016

BAM furnace apparatus tests were conducted to investigate the minimum ignition temperature of coal dusts (MITC) in O2/CO2 atmospheres with an O2 mole fraction from 20 to 50%. Three coal dusts: Indonesian Sebuku coal, Pittsburgh No.8 coal and South African coal were tested. Experimental results showed that the dust explosion risk increases significantly with increasing O2 mole fraction by reducing the minimum ignition temperature for the three tested coal dust clouds dramatically (even by 100°C). Compared with conventional combustion, the inhibiting effect of CO2 was found to be comparatively large in dust clouds, particularly for the coal dusts with high volatile content. The retardation effect of the moisture content on the ignition of dust clouds was also found to be pronounced. In addition, a modified steady-state mathematical model based on heterogeneous reaction was proposed to interpret the observed experimental phenomena and to estimate the ignition mechanism of coal dust clouds under minimum ignition temperature conditions. The analysis revealed that heterogeneous ignition dominates the ignition mechanism for sub-/bituminous coal dusts under minimum ignition temperature conditions, but the decrease of coal maturity facilitates homogeneous ignition. These results improve our understanding of the ignition behaviour and the explosion risk of coal dust clouds in oxy-fuel combustion atmospheres. © 2015 Elsevier B.V. Source


Hosseinzadeh S.,Catholic University of Leuven | Norman F.,Adinex NV | Verplaetsen F.,Adinex NV | Berghmans J.,Catholic University of Leuven | Van den Bulck E.,Catholic University of Leuven
Journal of Loss Prevention in the Process Industries | Year: 2016

In this study, the explosion characteristics of coal powder in O2CO2 atmospheres are studied. All experiments are performed in a 20 L spherical vessel. The maximum explosion pressure and the maximum rate of pressure rise are derived from the pressure time evolutions. A three-zone theoretical model has been applied to calculate the flame speed. To overcome the drawbacks of the non-spherical flames generated by pyrotechnical igniters, a continuous ignition spark is used as an alternative ignition source. The experimental results show that maximum explosion pressures are similar when different ignition sources are used. The maximum rate of pressure rise and the flame velocity are very sensitive to the ignition source. © 2016 . Source

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