Filtern
Erscheinungsjahr
- 2013 (23) (entfernen)
Dokumenttyp
- Beitrag zu einem Tagungsband (11)
- Vortrag (7)
- Zeitschriftenartikel (4)
- Buchkapitel (1)
Schlagworte
Eingeladener Vortrag
- nein (7)
Flammable gases and vapors
(2013)
ULLMANN'S Encyclopedia of Industrial Chemistry is the benchmark reference in chemistry and chemical and life science engineering, covering inorganic and organic chemicals, advanced materials, pharmaceuticals, polymers and plastics, metals and alloys, biotechnology and biotechnological products, food chemistry, process engineering and unit operations, analytical methods, environmental protection, and much more.
According to international standards several safety characteristics of dusts are determined in the 20-Lsphere (also known as SIWEK Chamber). Dust cloud ignition is carried out using pyrotechnical igniters.
Due to various disadvantages of such igniters the need for alternative ignition sources arises again and again. An alternative ignition source could be the so called 'exploding wire' or 'fuse wire'. The paper presents test results of a comparative study between both ignition sources for the determination of the safety characteristics Maximum Explosion Pressure and Maximum Explosion Pressure Rise of five selected dusts in the 20-L-sphere. In addition to that the ignition mechanisms of both ignition sources were analysed by high speed camera recordings and the ignition energy was determined with electric and calorimetric recordings.
The Ignition Temperature (IT) of stoichiometric tetrafluoroethylene–air mixtures on hot walls was determined in a 3-dm³-reactor. Tests at elevated pressure conditions were performed, namely at 5, 15 and 25 bar(a), showing a decrease of the IT with the initial pressure. Furthermore, the measured ignition temperatures of stoichiometric tetrafluoroethylene–air mixtures were lower than the ignition temperatures required for the decomposition pure tetrafluoroethylene (Minimum Ignition Temperature of Decomposition, MITD) reported in previous works.
Equations from the Semenov thermal explosion theory on spontaneous ignition were used to identify approximate combustion kinetics of tetrafluoroethylene from the experimental results. The determined kinetics was used for the prediction of the IT of stoichiometric tetrafluoroethylene-air by simplified calculation methods. A very good agreement with the experimental results was observed.
There is a lack of data on the self-ignition behaviour of tetrafluoroethylene (TFE) in industrial sized
equipment. In order to assess the tendency of TFE for
decomposition in large scale vessels, , a facility was
designed and constructed. Tests were
carried out in a cylindrical reactor with a volume of 100 L with initial
pressures of 5 and 10 bar(a). The effect of the reacto
r adjustment (vertical or horizontal) was taken into
account. The current work describes the test set
up and summarizes the experimental results achieved.
Furthermore, this paper reports on a numerical model for
the prediction of the self
-heating of TFE in closed
vessels, which was previously developed for small scale reactors and has been here validated for larger
dimensions with the experiments performed in the new facility.
According to international Standards several safety characteristics of dusts are determined in the 20-L-sphere (also known as SIWEK-Chamber). Dust cloud ignition is carried out using pyrotechnical igniters. Due to various disadvantages of pyrotechnical igniters the need for alternative ignition sources arises again and again. An alternative ignition source could be the socalled “exploding wire” or “fuse wire". The paper presents test results of a comparative study between both ignition sources for the determination of the safety characteristics Maximum Explosion Pressure and Maximum Rate of Explosion Pressure Rise of selected dusts in the 20-Lsphere.
In addition to that the flame/arc propagation of both ignition sources was analysed by high speed and IR camera recordings. Tests in a windowed autoclave were performed to get information on the influence of turbulence generated due to dispersion of the dust on the shape of the generated flame and its propagation. Turbulence measurements in the windowed autoclave as well as in the 20-L-sphere with a LDA System allowed investigation if the igniter led to turbulence increase at the moment of ignition in comparison to tests without ignition.
According to international standards several safety characteristics of dusts are determined in the 20-L sphere (also known as SIWEK-Chamber). Dust cloud ignition is carried out using pyrotechnical igniters. Due to various disadvantages of pyrotechnical igniters the need for alternative ignition sources arises again and again. An alternative ignition source could be the so-called 'exploding wire' or 'fuse wire'. The paper presents test results of a comparative study between both ignition sources for the determination of the safety characteristics Maximum Explosion Pressure and Maximum Rate of Explosion Pressure Rise of selected dusts in the 20-L sphere. In addition the propagation of flame and electrical arc was analysed by high speed camera recordings. Tests in a windowed autoclave were performed to get information on the influence of turbulence during ignition on the shape of the generated flame (electrical arc) and its propagation. Turbulence measurements with a LDA system in the windowed autoclave as well as in the 20-L sphere allowed investigation if the ignition sources led to an additional turbulence increase at the moment of ignition in comparison to tests without ignition.
Es werden die Untersuchungsergebnisse für ein geeignetes Zündkriterium zur Bestimmung von Explosionsgrenzen bei nichtatmosphärischen Bedingungen vorgestellt. Dazu wurden für Anfangsdrücke bis 20 bar Zündversuche an den Explosionsgrenzen von CHL/Luft-, CaHg/Luft-, H2/Luft- und NHs/Luft-Gemischen in einem Autoklav mit Sichtscheibe durchgeführt. In der Auswertung wurden visuelle Zündkriterien und ein Druckschwellenkriterium miteinander verglichen. Weiterhin wurden Untersuchungen zum erforderlichen Mindesvolumen des Explosionsgefäßes in Abhängigkeit des Anfangsdrucks durchgeführt. Dazu wurden jeweils Zündversuche mit demselben Gemisch aus CH4 und Luft bei Anfangsdrücken bis 50 bar in Volumina zwischen 0,2 dm3 und 6,0 dm3 durchgeführt.