OCR Text |
Show 6 is possible to keep the bed temperature within a required range by controlling the primary air. 3.2.3 Relationship between pyrolysis-gas composition and bed temperature Fig.6 shows the relationship between the pyrolytic gas composition at the exit of the pyrolysis furnace and the bed temperature when the heating value of the simulated refuse is 9.2 MJ/kg. As mentioned above, if the heating value of the simulated refuse is determined once, the bed temperature will be determined by the air ratio, and the composition of the pyrolytic gas to be generated will be determined by the bed temperature. The major components of the gas generated are CO, H2, C02, and CH4, and the oxygen content is almost zero. The combustible components among them are CO, H2, and CH4. While both CO and H2 content are around 10 % when the bed temperature is around 700°C, the contents of the combustible components are found to decrease with the decrease in the bed temperature. However, the CH4 content is almost constant irrespective of the bed temperature. 3.2.4 Behavior of metals in the fluidized-bed Steel and aluminum specimens were thrown into the furnace during pyrolysis operation with a bed temperature of below 600°C, and extracted together with sand. The bed temperature was almost uniform and the metallic specimens were not observed to have been visibly oxidized. No sand attached to the metal surface was observed (See Photo.2). A similar experiment was also made using steel cans, and the degree of oxidation was compared with that of the steel cans collected from a conventional incinerator. The results are shown in Fig.7. In steel cans collected from an incinerator, nearly 30 % of the total iron has been oxidized, compared to only about 2 % as for the steel cans extracted from the pyrolysis furnace. This observation shows that the present process is very effective in recovering resources. 3.3 Pyrolysis and melting experiment An investigation of the temperature distribution in the melting furnace and measurement of the exhaust gas composition under each experimental condition of the pyrolysis furnace was carried out. In addition, a leaching test on the discharged slag was performed. |