Abstract
The risks associated with dust explosions still exist in industries that either process or handle combustible dust. This explosion risk could be prevented or mitigated by applying the principle of inherent safety. One effective principle is to add an inert material to a highly combustible material in order to decrease its ignition sensitivity. This paper deals with an experimental investigation of the influence of inert dust on the minimum ignition temperature and the minimum explosion energy of combustible dust. The experiments detailed here were performed in a Godbert–Greenwald (GG) furnace and a 1.2 L Hartmann tube. The combustible dust (polyethylene—PE; 800 mesh) and four inert powders (NaHCO3, Na2C2O4, KHCO3, and K2C2O4) were used. The suppression effects of the four inert powders on the minimum ignition temperature and the minimum explosion energy of the PE dust have been evaluated and compared with each other. The results show that all of the four different inert dusts have an effective suppression effect on the minimum ignition temperature and the minimum explosion energy of PE dust. However, the comparison of the results indicates that the suppression effect of bicarbonate dusts is better than that of oxalate dust. For the same kind of bicarbonate dusts, the suppression effects of potassium salt dusts are better than those of the sodium salt. The possible mechanisms for the better suppression effects of bicarbonate dusts and potassium salt dusts have been analyzed here.
Highlights
Polyethylene (PE) is a type of thermoplastic resin made from polymerized ethylene
The results showed that the inert powder had a significant inerting effect on the minimum ignition energy (MIE) of acrylate copolymer (ACR) dust, and when the ammonium polyphosphate (APP)-II concentration reached 40%, the minimum MIE value of 960 mg for ACR dust increased to 990 mJ
The conclusions of this work are summarized as follows: All four inert powders of same particle size showed a significant suppression effect on the minimum ignition temperature (MIT) and MIE of PE dust. Both the MIT and MIE increased with an increase in the inert powder concentration
Summary
Polyethylene (PE) is a type of thermoplastic resin made from polymerized ethylene. It is one of the top five major synthetic resins in the world. During the process of producing PE particles, high concentrations of dust clouds can be formed in the process of granulation, drying, pneumatic transportation, and unloading This dust can be ignited by ignition sources such as static electricity or hot mechanical surfaces [1]. When the CO2 concentration reached 40% of the volume, the MIT and MIE of ACR dusts increased by 50 ◦ C and 257 mJ, respectively They investigated the inerting effects of ammonium polyphosphate (APP) on the MIT and MIE of polypropylene (PP) dusts. Addai et al [4] investigated the effects of adding inert powders (magnesium oxide, ammonium sulphate, and sand) on the ignition sensitivity (MIT and MIE) of combustible dust (brown coal, lycopodium, toner, niacin, corn starch, and high density polyethylene) mixtures. According to the experimental results and by comparing the inhibitory effects of four inert powders, the suppression effects and mechanisms of alkali metal ions (sodium ion and potassium ion) and acid radical ions on the MIT and MIE of PE dusts (bicarbonate ion and oxalate ion) are analyzed here
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