@article{Okutani_Ichikawa_Nagai_Hashimoto_Makihata_2018, place={Bangkok, Thailand}, title={Crystalline silica in compressed rice hull coke ash}, volume={28}, url={https://jmmm.material.chula.ac.th/index.php/jmmm/article/view/355}, abstractNote={Compressed rice hull coke was produced by compressing rice hulls ground to less than 200 µm diameter at 1.22x10<sup>6</sup> N/m<sup>2</sup> and 310˚C with an oxygen deficient atmosphere. The compressed rice hull coke had a 5 cm outer diameter, a 1.5 cm inner diameter and 35 cm length. The density of the coke is 1.2, and, the heat value is 16570 kJ·kg<sup>-1</sup>. In this study, 2 kg coke was combusted at the average temperature of 850˚C for 104 min with a maximum temperature of 860˚C. The ash was colored black-grey, and the form remained coke. The ash contained 95.4% silica with 9.2% cristobalite and 86.2% amorphous silica. The occupational exposure limits of respirable fraction of crystalline silica such as cristobalite and quartz in floating dust less than the diameter of 7 µm is 0.025 mg/m<sup>3</sup>; however, no respirable cristobalite was detected during combustion of the compressed rice hull coke. Cristobalite was not present in floating dust because it melted during the crystallization of amorphous silica to cristobalite.}, number={1}, journal={Journal of Metals, Materials and Minerals}, author={Okutani, Takeshi and Ichikawa, Eri and Nagai, Hedeaki and Hashimoto, Toshitaka and Makihata, Tsuyoshi}, year={2018}, month={Jun.} }