Thermal Runaway in Large ANFO Charges
Abstract
The purpose of this work was to determine the potential thermal hazards from self-heating of large ANFO charges. To accomplish this objective, the thermal stability of ANFO was determined from measurements of the critical temperature (i.e., the minimum temperature at which thermal runaway occurs) at three sample sizes: 40 mg, 25 g, and 25 kg. The effective thermal conductivity of solid ANFO at density 0.85 g/cm3 was measured as 0.11 W/(m K) using a specific heat value of 1.5 J/(g K). The cook-off data were used to determine the decomposition rate coefficient from 168 to 297 deg. C-a range covering over five decades in reaction rate. The resulting Arrhenius rate constant expression was k = 5.3 x 10(15) exp(-46.04/RT) s(-1), with the activation energy in kcal/mol units. The experimentally- determined ANFO parameters were incorporated into two models to investigate the potential for thermal runaway of ANFO charges of various sizes and for various initial conditions. If the initial temperature of ANFO loaded into a large container [for example, a hemisphere of 2,400 tons (20 meters (70 feet) in diameter)] is near ambient, the models indicate that no credible external heating is likely to bring the material to a homogeneous runaway condition.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1994
- Accession Number
- ADA526791
Entities
People
- Douglas Olson
- Marvin Banks
Organizations
- New Mexico Institute of Mining and Technology