Influence of Liquid and Vapourized Solvents on Explosibility of Pharmaceutical Excipient Dusts - Summary

Influence of Liquid and Vapourized Solvents on Explosibility of Pharmaceutical Excipient Dusts – Summary

1-Sentence-Summary: Explosion risk of hybrid dust/solvent mixtures in the pharmaceutical industry depends on both the nature of the two fuels and the method of admixture.

Authors: M. Hossain, P. Amyotte, M. Abuswer, A. Dastidar, F. Khan, R. Eckhoff, and Y. Chunmiao

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Influence of Liquid and Vapourized Solvents on Explosibility of Pharmaceutical Excipient Dusts - Summary

These authors complete experimental explosion testing of dust/solvent mixtures from the pharmaceutical industry. Specifically they test the excipient dusts microcrystalline cellulose and lactose, and solvent vapours methanol, ethanol, and isopropanol. In this context excipient means the inactive or non-medical ingredient in the pharmaceutical drug.

The dust are tested “as-received” from pharmaceutical manufactures. The particles sizes of the excipient dusts are characterized by the measurements 50% < 27 µm and 10% < 9 µm for the cellulose, and 62% < 89 µm and 18% < 75 µm for the lactose. In all hybrid tests the concentration of the solvent is held at 80% of the lower flammability limit. The solvent and dust are mixed using two approaches: prewetting where the dust is soaked with the solvent prior to the test being completed, and atmospheric mixing where the solvent is injected as a vapour into the dispersed dust cloud.

Results are presented for maximum pressure (Pmax), maximum rate of pressure rise (KSt), and Minimum Explosible Concentration (MEC) as mearsured in the 20-L explosion chamber. 10 kJ ignition energy is used for the explosion parameter testing, and 5 kJ for the MEC testing. Results are also presented for Minimum Ignition Energy (MIE) and Minimum Ignition Temperature (MIT) using the MIKE 3 apparatus and BAM oven, respectively.

Three of the main findings from this paper are:

  1. Both prewetted and atmospheric mixing of dust with solvents resulted in enhanced explosion severity.
  2. The degree of enhancement from the two mixing approaches depends on the dust and solvent being tested.
  3. Explosion likelihood as measured by MEC, MIE, and MIT increased with the addition of solvent vapour

The following sections outline the main findings in more detail. The interested reader is encouraged to view the complete article at the link provided below.

Finding #1: Explosion severity was increased by the addition of solvent vapour

In almost all cases Pmax and KSt of the excipient dust increased with the addition of solvent vapour. For example Pmax for lactose increased from 7.1 to 8.0 bar and KSt increased from 65 to 155 bar-m/s with the addition of methanol vapour. The worst case dust concentration also shifted downward with solvent addition moving from 2250 to 1000 g/m3 for these two fuels.

Finding #2: The more severe of the two mixing approaches could not be determined

Mixed results were seen from comparing the dust and solvent mixing approaches. Focusing on the maximum rate of pressure rise, both mixture approaches resulted in almost identical values throughout the dust concentration range for lactose and methanol mixtures. For lactose and isopropanol, prewetted mixing resulted in a KSt of 144 bar-m/s compared to 102 bar-m/s for atmospheric mixing and 65 bar-m/s for the lactose alone. On the other hand, for mixtures of cellulose and methanol, atmospheric mixing resulted in a KSt of 168 bar-m/s compared to 144 bar-m/s for prewetted mixing and 103 bar-m/s for the dust alone.

These results demonstrate the complexity of hybrid explosion of solid dusts mixed with solvent vapours. From the current results, a comment cannot be made on which method of admixture has the higher explosion severity and it appears that both can result in hybrid explosion enhancement.

Finding #3: Explosion likelihood as measured by MEC, MIE, and MIT increased with the addition of solvent vapour

The current authors found that all three measures of explosion likelihood decreased under the hybrid explosion conditions. The MEC of both dusts fell below 10 g/m3 with solvent admixture using the atmospheric approach. The MIE with inductance dropped between 30-75% with solvent prewetting of the dust, while the MIE without inductance dropped between 10-70%. Lastly, the MIT of all hybrid mixtures dropped between 10 and 50 degrees Celsius from solvent prewetting.

My Personal Take-Aways From
“Influence of Liquid and Vapourized Solvents on Explosibility of Pharmaceutical Excipient Dusts”

This paper is useful to those in the pharmaceutical industries as the dusts were selected with the help of industry members and tested “as-received”. Furthermore, the inclusion of both explosion consequence and likelihood parameters allows for a more complete assessment of the explosion risk in this industry. Other works by these authors have further extended this pragmatic approach to analyzing non-tradition dust explosion hazards in the processing industries (e.g., see Worsfold et al., 2012). Other authors such as Dastidar et al., 2005 and Glor 2010 and also completed research on the process safety implications of hybrid mixtures.

From a research perspective it is interesting to see that different methods of admixture effect the explosion severity, and that the degree of enhancement depends on the specific fuels. This illustrates the complex interactions occurring between multiphase flow, vaporization, and combustion. Further research in this area may be beneficial for both the pharmaceutical industry, as well as the wider hybrid explosion community, as the phenomenological processes occurring may help understand hybrid explosion enhancement for other fuels (e.g., see Denkevits, 2007, Garcia-Agreda et al., 2011, and Kosinski et al., 2013).

Full Citation:

  • N. Hossain, P. Amyotte, M. Abuswer, A. Dastidar, F. Khan, R. Eckhoff, and Y. Chunmiao, “Influence of liquid and vapourized solvents on explosibility of pharmaceutical excipient dusts,” Process safety progress, vol. 33, pp. 374-379, 2014.
    [Bibtex]
    @ARTICLE{Hossain2104,
    title={Influence of liquid and vapourized solvents on explosibility of pharmaceutical excipient dusts},
    author={Hossain, N. and Amyotte, P. and Abuswer, M. and Dastidar, A. and Khan, F. and Eckhoff, R. and Chunmiao, Y.},
    journal={Process Safety Progress},
    volume={33},
    pages={374--379},
    year={2014},
    link ={http://onlinelibrary.wiley.com/doi/10.1002/prs.11673/abstract},
    summary = {http://www.mydustexplosionresearch.com/influence-of-liquid-and-vapourized-solvents-on-explosibility-of-pharmaceutical-excipient-dusts-summary},
    }

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