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Vacuum pyrolysis has been widely used to decompose plastic wastes for obtaining purity chemicals or remove hazardous organic pollutants. The pyrolysis temperature determined the variety of pyrolysis products. The final (highest) temperature was the most investigated factor. However, temperatures used in vacuum pyrolysis were not equally distributed. The lowest temperature also determined the variety of the products. Regrettably, this vital factor has not been researched and reported. In this paper, the heat transfer process of vacuum pyrolysis was fully analyzed. The models for computing the lowest temperature were constructed. The models were certified by the vacuum pyrolysis of novolac epoxy particles collected from crushed waste printed circuit boards. According to the models, we found the heat transfer coefficient of the crucible and the inner diameters of the crucible and alundum tube were the key factors for controlling the lowest temperature. The models can help us to modify and adjust the lowest and highest (final) temperatures in vacuum pyrolysis. This contributed to recovering pure chemicals or removing pollutants from plastic wastes by vacuum pyrolysis.

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As a major part of municipal waste, the amount of waste glass has greatly increased. Due to its stable physical and chemical properties, glass can be effectively recycled with very little loss of quality. Meanwhile, recovery of waste glass is considered to be meaningful for saving resources and energy for sustainable development. However, remanufacturing processes always need a higher level of cleaning of waste glass. Traditionally, the combination technology of hydraulic cleaning and semimanual sorting is used to clean the organic and metallic impurities of waste glass. This combination technology has the disadvantages of low efficiency and producing lots of organic wastewater, which causes heavy environmental pollution. This study proposed an environmental-friendly combined recycling system of waste glass. Waterless cleaning, iron removing, eddy current separation, and optical separation were combined to realize the cleaning and sorting of waste glass. The operation parameters of each process of this new system were discussed and optimized. This system contributed to a high-efficiency and environmental-friendly way for the recovering of waste glass in municipal wastes, and it is an engineering practice to upgrade the urban solid waste recycling technology.

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