抄録
Most of waste plaster board, which contains gypsum has been buried in the landfill. However, this treatment of waste gypsum board is becoming a serious problem due to lack of landfill capacity, and secondary pollution by toxic substance. In this study, we focused a recycle of calcium resources as CaO or CaS from the waste gypsum, and developed a reduction process of the gypsum using plastics at high temperature. Reduction behavior of CaSO4 by Polyethylene at temperature from 1273 to 1573K was studied with gravimetry and X-ray diffraction analysis. From the experimental results, we found that increasing CaSO4-CH2 gas interface tend to advance the reduction of CaSO4. Furthermore, direct formation of CaS from CaSO4 was observed only at temperature of 1273K without an intermediate compounds stage, and the reduction sequence was CaSO4→CaO→CaS at temperatures higher than 1373K. Finally, the sequence of reduction process for CaSO4 was discussed on the potential diagram of the Ca-S2-O2 system.
