Fig. 18 The nitrogen oxides, carbon oxide, sulfur oxides and smoke emissions
The brake mean effective pressure (BMEP) and indicated mean effective pressures (IMEP) for 5% PE2 fuel, which had the highest viscosity of the three tested polymer fuels, are almost identical to those of heavy oil A, as shown in Fig. 16. The thermal efficiency of the polymer fuel is almost same as that of heavy oil A (Fig. 17).
Figure 18 shows the nitrogen oxide, carbon oxide, sulfur oxide and smoke emissions in the exhaust gas. The results show that the nitrogen oxide emission of the polymer fuels is lower than that of heavy oil A. Since heavy oil A contains a small amount of sulfur, sulfur oxide is formed in combustion.
Carbon oxide and smoke emissions were higher from the 5% PE2 and 5% PP2 fuels. However, these emissions from the 25% PP1 polymer fuel were the almost the same as those from heavy oil A. In this system, the injection timing of the diesel engine was adjusted in order to obtain the maximum thermal efficiency for heavy oil A operation. Therefore, it is possible to reduce the emissions of polymer fuel by adjusting the injection timing for each polymer fuel.
5. SUMMARY
A new thermal recycling system of waste plastics was proposed. In this study, polymer fuels that are mixtures of heavy oil A and plastics were produced at temperatures below those required for thermal cracking. The physical and chemical properties of the polymer fuels were measured. The results showed that the viscosity of the polymer fuels increases with not only polymer content but also mean molecular weight of the mixed polymers, and also that viscosity decreases at elevated temperatures. The thermal properties of the polymer fuels were found to be similar to those of heavy oil A. As a consequence, 10% PE (MW = 60,000) fuel, 10% PP (MW = 120,000) fuel and the fuel with more than 40% PP (MW = 12,000) are perhaps applicable to large heavy-duty diesel engines in practical systems. The fuels tested in the light-duty high-speed diesel engine used in this study were 50% PE (MW = 60,000) fuel, 25% PP (MW = 12,000) fuel and 50% PP (MW = 120,000) fuel. The results of the engine tests suggested that desirable cylinder pressure histories can be achieved and that the thermal efficiency of the polymer fuels is almost identical to that of heavy oil A. These results indicate that the present technique may be an efficient thermal recycling.
6. ACKNOWLEDGMENT
This study was supported by the Proposal-Based New Industry Creative Type Technology R&D Promotion Program (Project ID 97Eal3-005-1) from the New Energy and Industrial Technology Development Organization (NEDO) of Japan. Gratitude is extended to Mr. Osamu Sato, a graduate student at Ritsumeikan university, who assisted in this project.
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