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- Title
Water-in-Oil Emulsion Foaming by Thiourea Nitrosation: Reaction and Mass Transfer.
- Authors
Da Silva, Gabriel; Dlugogorski, Bogdan Z.; Kennedy, Eric M.
- Abstract
A study has been undertaken into the chemical production of gas bubbles within a concentrated water-in-oil emulsion, typical of those used as emulsion explosives. Chemical foaming was initiated by the introduction of a concentrated sodium nitrite solution to the emulsion, and the measurement of the decreasing emulsion density with time served to estimate the rate of nitrogen production. A conversion of emulsion density to nitrite ion concentration facilitated a kinetic analysis of the data. The change in nitrite ion concentration follows a rate equation which indicates that the rate-limiting reaction step corresponds to the N-nitrosation of thiourea by ON+, with an apparent rate constant of 0.22 M-1 s-1 at 25 °C. Tests over a temperature range of 25 to 50 °C yielded an activation energy of 59 kJ mol-1. A mass-transfer model describing the rate of diffusion between aqueous droplets is presented. This model suggests that chemical kinetics, rather than molecular diffusion, is the rate-limiting phenomenon in the foaming of emulsions. Supporting this finding, the kinetic experiments in emulsion returned very similar results to previous experiments performed in aqueous media under similar conditions.
- Subjects
CHEMICAL reactions; EMULSIONS; EXPLOSIVES; NITRITES; NITROSATION
- Publication
AIChE Journal, 2006, Vol 52, Issue 4, p1558
- ISSN
0001-1541
- Publication type
Article
- DOI
10.1002/aic.10752