Določanje eksplozijskih parametrov pri prašnih eksplozijah

Stovanje, Nastja (author), Novosel, Barbara (mentor)

Eksplozija prahu lahko pusti hude posledice za človeka, množico, infrastrukturo in okolje. Z razumevanjem temeljnega vzroka nastanka prašne eksplozije in dejavnikov, ki vplivajo na njeno napredovanje, lahko obvladujemo tveganje njenega nastanka. Na nastanek in napredovanje prašne eksplozije predvsem vpliva velikost delcev, koncentracija prahu in termične lastnosti prahu. Trem komercialno dostopnim izomerom gorljivega prahu (ftalna, izoftalna, tereftalna) ter velikostnim frakcijam delcev med 56 in 80 µm, 80 in 100 µm ter 100 µm in 125 µm sem eksperimentalno določila velikost in porazdelitev velikosti delcev, termične lastnosti in minimalno vžigno energijo. Najnižje območje MVE imajo velikostne frakcije delcev 56 µm – 80 µm, ta je v območju med 10 mJ in 30 mJ. Enako območje MVE imata tudi originalna vzorca IPA in TPA. Vrednost Es je pri obeh enaka in znaša 18,7 mJ. Originalni vzorec PA ima naj-višje območje MVE in sicer nad 1000 mJ. Pri povečanju velikostnih frakcij delcev pride do povečanja MVE. Največji porast območja MVE je pri TPA, ko med najmanjšo in največjo velikostno frakcijo, območje MVE naraste iz 10 mJ – 30 mJ na 300 mJ – 600 mJ. PA ima najnižje območje MVE, v kolikor so delci veliki med 80 µm in 125 µm . V primerjavi z IPA in TPA je to območje približno 100-krat nižje. Najnižjo vrednost Es doseže PA, najvišjo pa TPA. Do nižjega območja MVE pride zaradi slabe termične stabilnosti spojine, ki razpade pri 190 °C na novo spojino, ftalni anhidrid. Medtem ko sta IPA in TPA bolj stabilni spojini, razpadeta namreč pri 240 °C oziroma 260 °C. Največji vpliv na MVE ima velikost in porazdelitev velikosti delcev. Originalna vzorca IPA in TPA imata v primerjavi z originalnim vzorcem PA nizka območja MVE. To povzroči dovolj velik delež manjših delcev v vzorcu in ožja porazdelitev velikosti delcev. Porazdelitev velikosti delcev je pri PA med nekaj 10 µm in 2000 µm, medtem ko je pri originalnima vzorcema IPA in TPA med nekaj 10 µm in 500 µm. Vsebnost vlage v vzorcih sicer igra pomembno vlogo pri nastanku prašne eksplozije, vendar pri nobeni izmed spojin vlaga ne preseže 0,1 %, zato ta dejavnik ni imel bistvenega pomena na rezultate. Dejavnik, ki najbolj vpliva na MVE, je velikost delcev. Manjši delci so tisti, ki povzročijo vžige in so najbolj nevarni.

• Language: Slovenian
• Keywords: Prašna eksplozija, minimalna vžigna energija, ftalna kislina, tereftalna kislina, izoftalna kislina.
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2021
• PID: 20.500.12556/RUL-129961
• COBISS.SI-ID: 81948419
• Publication date in RUL: 09.09.2021

Secondary language

• Language: English
• Title: Explosive limits of dust explosions

Abstract

A dust explosion can have serious consequences for humans, the crowd, infrastructure and the environment. By understanding the root cause of a dust explosion and the fac-tors that influence its progression, we can manage the risk of its occurrence. The formation and progression of a dust explosion are mainly influenced by the particle size, dust concentration and thermal properties of the dust. I experimentally determined the size and distribution of particle size, thermal proper-ties and minimum ignition energy for three commercially available isomers of com-bustible dust (phthalic, isophthalic, terephthalic) and particle size fractions between 56 and 80 μm, 80 and 100 μm, 100 μm and 125 μm. Particle size fractions of 56 µm - 80 µm have the lowest MVE range, which is in the range between 10 mJ and 30 mJ. The original IPA and TPA samples have the same MVE range. The value of Es is the same in both and is 18.7 mJ. The original PA sample has the highest MVE range above 1000 mJ. As the particle size fractions increase, the MVE range increases. The largest increase in the MVE area is in TPA, when between the smallest and largest size fraction, the MVE area increases from 10 mJ - 30 mJ to 300 mJ - 600 mJ. PA has the lowest MVE range if the particles are between 80 µm and 125 µm in size. Compared to IPA and TPA, this range is about 100x lower. The lowest value of Es is reached by PA and the highest by TPA. The lower MVE range occurs due to the poor thermal stability of the compound, which decomposes at 190 ° C to a new compound, phthalic anhydride. While IPA and TPA are more stable compounds, they decompose at 240 ° C and 260 ° C, respectively. Particle size and particle size distribution have the greatest impact on MVE. The original IPA and TPA samples have low MVE ranges compared to the original PA sample due to the suffi-ciently large proportion of smaller particles in the sample and due to the narrower par-ticle size distribution. The particle size distribution is between a few 10 µm and 2000 µm for PA, while it is between a few 10 µm and 500 µm for the original IPA and TPA samples. The moisture content of the samples plays an important role in the formation of the dust explosion, but for none of the compounds does the moisture exceed 0.1%, so this factor was not essential for the results. The factor that most affects MVE is particle size. Smaller particles are the ones that cause ignition and are the most dangerous.

• Keywords: Dust explosion, phthalic acid, isophthalic acid, terephthalic acid, minimum ignition energy.