Flame propagation behaviours and overpressure characteristics of LDPE dust / ethylene hybrid mixture explosions

ABSTRACT

It studied the explosion propagation of the hybrid mixture of LDPE dust and a small amount of ethylene (below its LEL) in a closed duct, to examine the impacts of dust concentration, dust particle size, and ethylene concentration on flame propagation behavior and overpressure characteristics. The dust concentration affected the explosion behavior of the LDPE dust/ethylene hybrid mixture in two ways. The flame gradually became discrete and unstable as the dust concentration increased, while the maximum and average flame propagation velocity, P_max, and (dp/dt)_max increased first and then decreased. The dust particle size and ethylene concentration had a significant effect on the hybrid mixture explosion. As the particle size decreased or the ethylene concentration increased, the discrete flames quickly merged into a bright continuous flame. Further, the maximum and average flame propagation velocity, P_max, and (dp/dt)_max increased, whereas the fluctuation degree of the flame propagation velocity with time showed a decreasing trend. There was no obvious agglomeration phenomenon among small LDPE particles. The explosion overpressure and flame propagation showed a strong synergistic effect. Compared with the semi-open duct, the closed duct with a more uniform dust/gas hybrid mixture showed a more continuous flame structure, a shorter flame propagation distance, and a lower flame propagation velocity. These conclusions can provide a scientific basis for explosion risk analyses and process safety designs involving the production of LDPE powder.

KEYWORDS:

• Dust explosion
• low density polyethylene
• Ethylene
• hybrid mixture
• flame propagation
• overpressure

Acknowledgments

The authors thank Elsevier for their English translation service. They also appreciate the financial support from the Beijing Science and Technology Nova Program (No. Z181100006218092), and the Training Funded Project of the Beijing Youth Top-Notch Talents of China (No. 2016000026833ZK05).

Declarations of interest

none.

Additional information

Funding

This work was supported by the Beijing Municipal Excellent Talents Foundation [No. 2016000026833ZK05]; Beijing Nova Program [No. Z181100006218092].