Abstract
Pyrolysis is a thermochemical decomposition of organic compounds such as High-density polyethylene (HDPE) plastics. The product of the HDPE pyrolysis is usually diesel with other wastes (such as carbon black, etc.). A pyrolysis reaction is essentially a decomposition reaction performed at elevated temperatures in the absence of oxygen. There are many other complex reactions taking place in pyrolysis, however, in this paper, the focus has been on three main reactions of HDPE pyrolysis, namely: 𝛽−scission, hydrogen abstraction and chain fission. Of these, 𝛽−scission is known to be most dominant reaction in HDPE pyrolysis reactions. In this work, the reaction equations and reaction constants were defined and solved in MATLAB® using the in-built ordinary differential equation (ODE) solver. The solution represents the rate of the reaction and the product yield.
Highlights
A good source of the raw materials for pyrolysis is industrial waste
The results show that High-density polyethylene (HDPE) is broken down relatively quickly and after about 20 minutes very little of the HDPE is left
The production of oil and gas is rapid in the initial phases of the process and begins to level-off as the light and heavy wax produced in the early phase of the process is used-up
Summary
A good source of the raw materials for pyrolysis is industrial waste. Examples of industrial waste that can be treated in this way include tyres and the HDPE cages used in the fish farm industry. A great deal of HDPE plastic waste is ground to small pellets and disposed of in landfills. The pellets are heated in a chamber to around 400°C – 500°C to begin the pyrolysis process using an external source of fuel. Once this temperature is reached, the gasses that are being produced by the pyrolysis reaction form the primary fuel for the external burners and the process is more or less self-sustainable. In addition to the conventional process of pyrolysis, researchers have considered other ways of treating plastic wastes. (c) Figure 2: (a) the chemical formula of polyethylene, (b) illustrates a space fill model of the HPDE. (c) illustrates a potential branching structure of polyethylene
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