Related Experiment Videos
Evaluation on thermal explosion induced by slightly exothermic interface reaction.
Ma-Hong Yu1, Yong-Fu Li, Jin-Hua Sun
1School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, PR China. yumahong@mail.njust.edu.cn
Journal of Hazardous Materials
|September 15, 2004
Summary
Investigating asphalt-salt mixtures (ASM) revealed that exothermic reactions below 250°C intensify above this temperature due to salt melting. Runaway reactions are unlikely below 162°C, suggesting self-heating caused past explosions.
Area of Science:
- Chemical Engineering
- Materials Science
- Nuclear Safety
Background:
- Asphalt-salt mixtures (ASM) pose significant thermal hazards, as evidenced by past incidents in reprocessing plants.
- Understanding the thermal behavior of ASM is crucial for safe waste management and reprocessing operations.
Purpose of the Study:
- To experimentally evaluate the thermal hazards of a simulated asphalt-salt mixture (ASM) prepared at a lab scale.
- To determine the kinetic parameters governing the exothermic reactions within ASM.
- To simulate the thermal behavior of ASM in a drum and identify conditions leading to runaway reactions.
Main Methods:
- Preparation of a simulated ASM using a lab-scale bituminization process.
- Heat flux reaction calorimetry to measure heat release under constant heating rate and temperature.
- Formulation of reaction rates based on a proposed model and determination of kinetic parameters.
- Numerical simulation of temperature changes in an ASM-filled drum using a one-dimensional infinite cylinder model.
Main Results:
- The reaction in ASM below approximately 250°C is a mild exothermic interface reaction.
- Heat release rate sharply increases above 250°C due to salt particle melting.
- The minimum filling temperature for a runaway reaction (MFTRR) in the simulated ASM is approximately 194°C.
- A strong linear correlation was found between MFTRR and the initial salt particle radius.
- The critical filling temperature for runaway reaction is approximately 162°C for ASM with zero-size salt particles.
Conclusions:
- Runaway reactions in ASM are unlikely below a filling temperature of 162°C under the simulated conditions.
- Past explosions in reprocessing plants were likely caused by exothermic reactions and self-heating.
- Safe filling temperatures for ASM drums can be established based on particle size and ambient conditions.