Coprocessing for Fuel from Mixed Plastic Waste

6 COPROCESSING FOR FUEL FROM MIXED PLASTIC WASTE 

Coprocessing refers to the combined processing of petroleum residue with other hydrocarbon feedstocks. The petroleum residue contains chiefly 75 wt% materials boiling above 

500° C. The waste plastics are petroleum derived and therefore, provide a hydrocarbon source that can be used for chemical feedstocks. The feedstocks are mixed and processed simultaneously with the dual objective of liquefying the solid waste and upgrading the heavy residue from either the liquefied solid wastes or petroleum oil to the premium fuel oils boiling lower than 500°C. 

The effects of catalyst on the product distribution for selected plastic/residue doublecomponent systems are shown in Table 14.2. The results show that the presence of residue increased the overall conversion in the double-component coprocessing reactions compared to the single-component reactions except in the case of polystyrene [14]. 

The effect of different temperatures and time durations on the product distribution of LDPE, residue and LDPE/residue are given in Table 14.3. The conversions from LDPE ranged from 50.0 to 57.3% at 430°C, 60 min and from 11.5 to 17.0% at 400°C 60 min. When the time was reduced to 30 min the conversions were 21.5-23.7% at 430°C. At the higher reaction temperature (430°C) the amount of hexane solubles (HXs) was high and the THFs were low. At 400°C the amount of HXs produced from the LDPE reaction was very low and recovery was high, indicating that low-boiling compounds were not formed. The LDPE/resid system also produced less HXs at 400°C than at 430°C. 

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