Compound materials consisting of plastic and metal have been com-ing into wide use in industrial products, and wastes of compound material are also in-creasing. For establishing the material recycle system, it is desired to develop an useful technology of plastic separation from metal. In this study, we developed a new separa-tion technique of plastics from compound wastes. In this technique, a high temperature molten salt (KNO₃-NaNO₃-NaNO₂) was used as a separation medium. The compound wastes were immersed directory into the molten salt bath. Plastics was heated and flui-dized in the molten salt bath. Fluidized plastics were separated from the metal by the buoyancy effect. Five major plastics; policarbonate, polypropyrene, polystyrene, polyacetal and polyvinylchloride were tested by this technique, and the following results were obtained.(1) The separation of plastics from metal was observed when plastics were heated up to their fluidized temperatures.(2) The time of separation becomesshorter and the ratio of separation becomes larger with the molten salt temperature rise.(3) The “melting separation technique” developed here was usefulfor the separation of plastics from the compound wastes such as a F-cable.

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Floatability of three kinds of coal, Datong, Ensham and Illinois No.6, was investigated with various superficial gas velocities and additive concentrations in a small-scale flotation column. The orders of both carbonaceous materials recovery and ash rejection were found to be Datong > Ensham > Illinois No.6. Distribution of hyd-rophobicity of coal particles was evaluated by means of the film flotation method. The order of the strength of hydrophobicity determined by the film floatation method was in consistent with that of carbonaceous materials recovery and thereby it was confirmed that this method is useful for evaluating floatability of coal qualitatively. It was found that inorganic sulfur can be rejected by column flotation, indicating that a column floata-tion process can be applied for simultaneous demineralization and desulphurization of coal. The order of pyrite rejection was Ensham > Datong > Illinois No.6, being different from that of ash rejection.

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Iron catalysts have generally been used as a one through catalyst for coal liquefaction. However, in some cases, scale formation phenomenon on to the inner wall of the preheater and pipes has been reported.
In this study, the conditions and mechanisms of scale formation, and possible method of prevention were investigated.
Remarkable scale formation was not found in the experimental tests using pyrite catalyst, on the contrary, iron oxide catalyst system caused scale formation within some limited conditions.
The scale formation mechanisms in the iron oxide catalyst system were inferred as follows:
Fine iron compound is sulfurized by hydrogen sulfide in the preheating process, then becomes fine and active crystalline pyrrhotite.
Fine pyrrhotite crystals combine into coarse crystal on the high temperature pipe wall (over 400°C) of the preheater and form the scale with inclusions of fine coal and inorganic particles.
To prevent the scale formation in the iron oxide catalyst system, following measures are proposed ;
·Maximum temperature of preheater wall has to keep under 400°C .
·By surrounding an active pyrrhotite crystal with enough amount of coal molecules, coal molecules are adsorbed to the surface of fine pyrrhotite. Such condition arrests the growth to the coarse crystal of fine pyrrhotite crystal, and finally, the scale forma- tion is prevented.
To achieve such condition, for example, the method of coal impregnated with fine iron oxide is considered to be effective.

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