Study On Pyrolysis Kinetics Of Polyethylene In The Ethylene

Polyethylene is widely used due to its good performance. The production scale of polyethylene is expanding with the gradual increase of demand for polyethylene, which brings new safety issues. The fire and explosion of polyethylene dust in the process of production is the common accident. The frequent fire and explosion accident of polyethylene dust seriously threats to people’s life and property safety and affects the normal production of polyethylene. Therefore, it is very necessary to study the pyrolysis behavior of polyethylene for the determination of the polyethylene production process conditions and providing a scientific basis for the prevention of polyethylene dust explosion.The pyrolysis of linear low density polyethylene(LLDPE) and high density polyethylene(HDPE) in N2 and C2H4 was studied in this paper. The character of polyethylene pyrolysis affected by different heating rate and ethylene concentration using TG-DSC and the gaseous product distribution of polyethylene pyrolysis affected by different heating rate in N2 using GCMS were researched. Finally, pyrolysis kinetics of polyethylene was studied by using the Li Chung-Hsiung thermal analysis method, the most suitable mechanism function was selected, and the rate constant, frequency factor and activation energy were obtained based on the right mechanism function. Then the affection on activation energy by heating rate and ethylene concentration was gotten.The results show that pyrolysis temperature range of LLDPE and HDPE is moving to high temperature side, the temperature reaching the highest pyrolysis rate increases linearly and pyrolysis index is more and more big with the growing of heating rate. But the final pyrolysis rate of polyethylene changes little. When ethylene concentration is between 5% and 10%, the increase of ethylene concentration has little effect on pyrolysis at the pyrolysis temperature range, but it has a great influence on the polyethylene pyrolysis rate. With the increase of heating rate, polyethylene molecular chains are more likely to fracture, and the gaseous product increase gradually. The pyrolysis mechanism functions of LLDPE and HDPE at the pyrolysis temperature range with different heating rate and ethylene concentration are consistent with random nucleation model, f(α)= ? ? ? ?2 33 1 ?? ??ln 1 ?? ?? ?. The activation energy of HDPE is larger than LLDPE in N2. The addition of ethylene has an influence on activation energy of polyethylene pyrolysis, which makes the activation energy of LLDPE is larger than HDPE in the same condition. The activation energy of LLDPE in the C2H4 is larger than N2, which demonstrates the addition of ethylene inhibits the pyrolysis of LLDPE in a certain extent.