TY - JOUR A1 - Abbas, Z. A1 - Gabel, D. A1 - Krietsch, Arne A1 - Krause, U. T1 - Quasi-static dispersion of dusts for the determination of lower explosion limits of hybrid mixtures JF - Jounal of Loss Prevention in the Process Industries N2 - Knowledge of explosion limiting concentration of explosible materials is necessary forthe design of explosion protection measures. Currently employed methods of testing MEC of a dust cloud or LEL of a hybrid mixture are based on arbitrary assumptionsand possess technical limitations that often lead to values of MEC/LEL, which are unrealistically low or poorly reproducible. This contribution presents an improved method for experimental determination of MEC of a combustible dust cloud or LEL of a flammable gas or hybrid mixture. The new setup operates under laminar conditions and allows a uniform suspension of dust particles in an open top acrylic glass tube. Dust concentration is measured with the help of infrared sensors installed a few centimeters above and below the ignition source. In order to evaluate the dependence of MEC on flow front velocity, MEC of lycopodium was determined at four flow velocities. The results show that the flow field intensity does not significantly influence the MEC of lycopodium for the flow ranges tested in this work. Moreover, LEL of hybrid mixtures of lycopodium and methane was also tested at flow velocities of 4.7 cm/s, 5.8 cm/s, 7 cm/s and 11 cm/s and compared with the values obtained from other sources. The results suggest that the requirement of high energy pyrotechnical igniter may be relinquished, provided that a truly homogeneous suspension of dust particles could be achieved. Moreover, the effect of relative amount of dust and gas, on the course of ignition and flame propagation in hybrid mixtures at their LEL, was studied by the help of high speed videos. For hybrid mixtures of carbonaceous dusts (like lycopodium) at their LEL, ignition occurs in the gas phase, however, flame propagation is only possible through a two-way interaction of dust and gas during the course of combustion. KW - Dust explosions KW - Gas explosions KW - Lower explosion limit KW - Hybrid mixtures PY - 2022 DO - https://doi.org/10.1016/j.jlp.2021.104640 SN - 0950-4230 VL - 74 SP - 1 EP - 18 PB - Elsevier Ltd. AN - OPUS4-54077 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bouillard, J. A1 - Krietsch, Arne A1 - Vignes, A A1 - Janes, A. A1 - Carson, D. A1 - Holzschuh, O. T1 - CEN/TC 352/WG 3/PG 3 – Guidelines for Determining Protocols for the Explosivity and Flammability of Powders containing Nano-objects (for Transport, Handling and Storage) N2 - The European Committee for Standardization (CEN) set up the Technical Committee 352 (CEN/TC 352) in 2006 to develop and maintain up to date standards in the field of nanotechnologies. Part of the work group (WG 3) dedicated to Health, Safety and Environment, the CEN/TC 352/WG 3/PG 3 led by INERIS was constituted to develop a Technical Specification (TS) for the determination of explosivity and flammability properties of manufactured nano-objects in powder form (2013-2018). T2 - 2nd Open Meeting - European Conference on Standardization for Nanotechnologies and Nanomaterials: Reliable data for an effective management of nanomaterials CY - Valletta, Malta DA - 10.06.2017 KW - Dust explosions KW - Nanomaterials KW - Combustible dust PY - 2017 AN - OPUS4-43076 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Klippel, Alexander A1 - Scheid, Marc A1 - Krause, U. ED - Makhviladze, G. ED - Molkov, V. ED - Bradley, D. ED - Sunderland, P. ED - Tamanini, F. T1 - Progress on the research into the influence of dustiness on dust explosions T2 - ISFEH7 - 7th International seminar on fire & explosion hazards (Proceedings) N2 - In practice, occurring explosive dust/air mixtures are usually not homogeneous and in many cases do not spread over the whole enclosure. For the safety measure explosion venting, a smaller venting area might be sufficient as calculated according to venting standards (EN 14491 'Dust Explosion Venting Protective Systems'). The tendency of bulk materials to form dust clouds is not taken into account so far. To optimize the design of explosion protection measures, a new safety characteristic the so-called 'dustiness' (see VDI 2263 part 9 'Determination of Dustiness of Bulk Materials'.) could be useful. Dustiness means the tendency of dust to form dust clouds. There are six dustiness groups (DG) from one to six (one means little tendency to stay airborne, six the opposite). The paper describes first results on the reasons for different dustiness and on dust explosion venting for several dusts of different dustiness. A 75 L vertical tube apparatus for vented dust explosion experiments was created. Pressure, pressure rises and flame speeds were measured to evaluate the course of the dust explosions. In addition the paper includes CFD simulations (ANSYS CFX) about the possibilities to model the dust/air mixtures with the Euler/Lagrange approach. In order to simulate the settling of dust clouds more realistic the particle surface area was adjusted and the particle size distribution was taken into account. Results were compared to experimentally determined terminal velocities. T2 - ISFEH7 - 7th International seminar on fire & explosion hazards CY - Providence, RI, USA DA - 05.05.2013 KW - CFD KW - Dust explosions KW - Dustiness KW - Venting PY - 2013 SN - 978-981-07-5936-0 SN - 978-981-07-5940-7 DO - https://doi.org/10.3850/978-981-07-5936-0_13-01 SP - 781 EP - 790 PB - Research Publishing AN - OPUS4-28502 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krause, Ulrich A1 - Wappler, Mike A1 - Radzewitz, S. A1 - Ferrero, Fabio T1 - On the minimum ignition temperature of dust clouds T2 - 6th International Symposium on hazards, prevention, and mitigation of industrial explosions - VI ISHPMIE (Proceedings) T2 - 6th International Symposium on hazards, prevention, and mitigation of industrial explosions CY - Halifax, Canada DA - 2006-08-27 KW - Dust explosions KW - Ignition KW - Hot surfaces KW - Minimum ignition temperature PY - 2006 VL - 1 SP - 68 EP - 76 PB - Dalhousie University CY - Halifax AN - OPUS4-12787 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krietsch, Arne A1 - Krause, U. A1 - Gabel, D. A1 - Abbas, Z. A1 - Dufaud, O. T1 - Quasi-static dispersion of dusts for the determination of lower explosion limits of hybrid mixtures T2 - Proceedings of the 13th Symposium International Symposium on Hazards, Prevention and Mitigation of Industrial Explosions N2 - Knowledge of explosion limiting concentration of explosible materials is necessary for the design of explosion protection measures. Currently employed methods of testing MEC of a dust cloud or LEL of a hybrid mixture are based on arbitrary assumptions and possess technical limitations that often lead to values of MEC/LEL, which are unrealistically low or poorly reproducible. This contribution presents an improved method for experimental determination of MEC of a combustible dust cloud or LEL of a flammable gas or hybrid mixture. The new set-up operates under laminar conditions and allows a uniform suspension of dust particles in an open top acrylic glass tube. Dust concentration is measured with the help of infrared sensors installed a few centimeters above and below the ignition source. In order to evaluate the dependence of MEC on flow front velocity, MEC of lycopodium was determined at four flow velocities. The results show that the flow field intensity does not significantly influence the MEC of lycopodium for the flow ranges tested in this work. Moreover, LEL of hybrid mixtures of lycopodium and methane was also tested at flow velocities of 4.7 cm/s, 5.8 cm/s, 7 cm/s and 11 cm/s and compared with the values obtained from other sources. The results suggest that the requirement of high energy pyrotechnical igniter may be relinquished, provided that a truly homogeneous suspension of dust particles could be achieved. Moreover, the effect of relative amount of dust and gas, on the course of ignition and flame propagation in hybrid mixtures at their LEL, was studied by the help of high speed videos. For hybrid mixtures of carbonaceous dusts (like lycopodium) at their LEL, ignition occurs in the gas phase, however, flame propagation is only possible through a two-way interaction of dust and gas during the course of combustion. T2 - 13th Symposium International Symposium on Hazards, Prevention and Mitigation of Industrial Explosions (ISHPMIE) CY - Online meeting DA - 27.07.2020 KW - Dust explosions KW - Gas explosions KW - Lower explosion limit KW - Hybrid mixtures PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-540955 DO - https://doi.org/10.7795/810.20200724 SP - 750 EP - 764 PB - Physikalisch-Technische Bundesanstalt AN - OPUS4-54095 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krietsch, Arne A1 - Reyes Rodriguez, M. A1 - Kristen, A. A1 - Kadoke, D. A1 - Abbas, Z. A1 - Krause, U. T1 - Ignition temperatures and flame velocities of metallic nanomaterials JF - Jounal of Loss Prevention in the Process Industries N2 - The production of materials with dimensions in the nanometre range has continued to increase in recent years. In order to ensure safety when handling these products, the hazard potential of such innovative materials must be known. While several studies have already investigated the effects of explosions (such as maximum explosion pressure and maximum pressure rise) of powders with primary particles in the nanometre range, little is known about the ignition temperatures and flame velocities. Therefore, the minimum ignition temperature (MIT) of metallic nano powders (aluminium, iron, copper and zinc) was determined experimentally in a so called Godbert-Greenwald (GG) oven. Furthermore, the flame velocities were determined in a vertical tube. In order to better classify the test results, the tested samples were characterised in detail and the lower explosion limits of the tested dust samples were determined. Values for the burning velocity of aluminium nano powders are higher compared to values of micrometre powd ers (from literature). While MIT of nanometre aluminium powders is within the range of micrometre samples, MIT of zinc and copper nano powders is lower than values reported in literature for respective micrometre samples. KW - Dust explosions KW - Nanomaterial KW - Flame propagation KW - Minimum ignition temperature PY - 2021 DO - https://doi.org/10.1016/j.jlp.2021.104482 SN - 0950-4230 VL - 2021 IS - 71 SP - 1 EP - 9 PB - Elsevier Ltd. AN - OPUS4-54076 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krietsch, Arne A1 - Reyes Rodriguez, M. A1 - Kristen, A. A1 - Kadoke, D. A1 - Abbas, Z. A1 - Krause, U. T1 - Ignition temperatures and flame velocities of metallic nanomaterials T2 - Proceedings of the 13th Symposium International Symposium on Hazards, Prevention and Mitigation of Industrial Explosions N2 - The production of materials with dimensions in the nanometre range has continued to increase in recent years. In order to ensure safety when handling these products, the hazard potential of such innovative materials must be known. While several studies have already investigated the effects of explosions (such as maximum explosion pressure and maximum pressure rise) of powders with primary particles in the nanometre range, little is known about the ignition temperatures and flame velocities. Therefore, the minimum ignition temperature (MIT) of metallic nano powders (aluminium, iron, copper and zinc) was determined experimentally in a so called Godbert-Greenwald (GG) oven. Furthermore, the flame velocities were determined in a vertical tube. In order to better classify the test results, the tested samples were characterised in detail and the lower explosion limits of the tested dust samples were determined. Values for the burning velocity of aluminium nano powders are higher compared to values of micrometre powders (from literature). While MIT of nanometre aluminium powders is within the range of micrometre samples, MIT of zinc and copper nano powders is lower than values reported in literature for respective micrometre samples. T2 - 13th Symposium International Symposium on Hazards, Prevention and Mitigation of Industrial Explosions (ISHPMIE) CY - Online meeting DA - 27.07.2021 KW - Dust explosions KW - Nanomaterial KW - Flame propagation KW - Minimum ignition temperature PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-540930 DO - https://doi.org/10.7795/810.20200724 SP - 591 EP - 605 PB - Physikalisch-Technische Bundesanstalt AN - OPUS4-54093 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Santandrea, A. A1 - Vignes, A. A1 - Krietsch, Arne A1 - Brunello, D. A1 - Perrin, L. A1 - Laurent, A. A1 - Dufaud, O. T1 - Evaluating the explosion severity of nanopowders: International standards versus reality JF - Process Safety and Environmental Protection N2 - The maximum explosion overpressure and the maximum rate of pressure rise, which characterize thedust explosion severity, are commonly measured in apparatuses and under specific conditions defined byinternational standards. However, those standards conditions, designed for micropowders, may not befully adapted to nanoparticles. Investigations were conducted on different nanopowders (nanocellulose,carbon black, aluminum) to illustrate their specific behaviors and highlight the potential inadequacyof the standards. The influence of the sample preparation was explored. Various testing procedureswere compared, focusing on the dust cloud turbulence and homogeneity. Dust dispersion experimentsevidenced the importance of the characterization of the dust cloud after dispersion, due to the frag-mentation of agglomerates, using metrics relevant with nanoparticles reactivity (e.g. surface diameterinstead of volume diameter). Moreover, the overdriving phenomenon (when the experimental resultsbecome dependent of the ignition energy), already identified for micropowders, can be exacerbated fornanoparticles due to their low minimum ignition energy and to the high energy used under standardconditions. It was evidenced that for highly sensitive nanopowders, pre-ignition phenomenon can occur.Finally, during severe explosions and due to a too long opening delay of the ‘fast acting valve’, the flamecan go back to the dust container. KW - Dust explosions KW - Gas explosions KW - Minimum ignition temperature KW - Hybrid mixtures PY - 2020 DO - https://doi.org/10.1016/j.psep.2020.04.011 VL - 138 SP - 279 EP - 291 PB - Elsevier B.V. AN - OPUS4-50944 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scheid, Marc A1 - Geißler, Andreas A1 - Krause, Ulrich T1 - Experiments on the influence of pre-ignition turbulence on vented gas and dust explosions JF - Journal of loss prevention in the process industries N2 - Experiments were performed on the influence of pre-ignition turbulence on the course of vented gas and dust explosions. A vertical cylindrical explosion chamber of approximately 100 l volume and a length-to-diameter ratio (l/d) of 4.7 consisting of a steel bottom segment and three glass sections connected by steel flanges was used to perform the experiments. Sixteen small fans evenly distributed within the chamber produced turbulent fluctuations from 0 to 0.45 m/s. A Laser-Doppler-anemometer (LDA) was used to measure the flow and turbulence fields. During the experiments the pressure and in the case of dust explosions the dust concentration were measured. In addition, the flame propagation was observed by a high-speed video camera. A propane/nitrogen/oxygen mixture was used for the gas explosion experiments, while the dust explosions were produced by a cornstarch/air mixture. It turned out that the reduced explosion pressure increased with increasing turbulence intensity. This effect was most pronounced for small vents with low activation pressures, e.g. for bursting disks made from polyethylene foil. In this case, the overpressure at an initial turbulence of 0.45 m/s was twice that for zero initial turbulence. KW - Gas explosions KW - Dust explosions KW - Turbulence KW - Venting PY - 2006 DO - https://doi.org/10.1016/j.jlp.2007.03.001 SN - 0950-4230 SN - 1873-3352 VL - 19 IS - 2-3 SP - 194 EP - 199 PB - Butterworth CY - Guildford, Surrey AN - OPUS4-11833 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Martin A1 - Wu, Dejian A1 - Zhao, P. A1 - Tan, X. A1 - Huang, W. A1 - Qianc, X. T1 - Minimum explosion concentrations of coal dusts with CH4/H2/CO below the gas lower explosion limit JF - Fuel N2 - A 20-L spherical explosion chamber was used to investigate the explosion characteristics of dust clouds in air with the presence of flammable gas which is lower than its lower explosion limit (LEL). including minimum explosion concentration (MEC) of dust. Explosion pressure (Pex) and explosion pressure rise (dp/dt)ex). Two dust samples (anthracite coal, bituminous coal) and were three flammable gases (CH4, H2 and CO) were tested. Experimental results showed that the explosion of hybrid mixtures occurs when both dust and gas concentrations are lower than the LEL/MEC of the single substances. Meanwhile. all flammable gases with different volume fractions have distinct effects on the MEC. Pex and (dp/dt)ex of the dust samples. With the increase of the flammable gas concentration. either the Pex and (dp/dt)ex increase or the MEC decreases for all the hybrid mixtures of both two dust samples. At the same concentration of coal dusts. the addition of CH4 promotes higher explosion risks than the other two flammable gases. The distribution of (dp/dt)ex is quite different with the restricted area defined by empirical formulas. These results improve our understanding of the explosion behaviour and the explosion risk of hybrid dust-gas mixtures in air. KW - Dust explosions KW - Gas explosions KW - Minimum explosible concentration KW - Lower explosion limit KW - Hybrid mixtures PY - 2020 DO - https://doi.org/10.1016/j.fuel.2019.116401 SN - 0032-5910 VL - 260 SP - UNSP 116401 PB - Elsevier Sci. Ltd. AN - OPUS4-49956 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -