Crystalline silica in compressed rice hull coke ash

Authors

  • Takeshi Okutani Rice Hulls Research Center https://orcid.org/0000-0003-2263-3231
  • Eri Ichikawa Yokohama National University
  • Hedeaki Nagai National Institute of Advanced Industrial Science and Technology
  • Toshitaka Hashimoto Tromso Co., Ltd.
  • Tsuyoshi Makihata Tromso Co., Ltd.

Keywords:

Rice hull coke, Ash, Potassium Cristobalite, Respirable crystalline silica, Combustion

Abstract

Compressed rice hull coke was produced by compressing rice hulls ground to less than 200 µm diameter at 1.22x106 N/m2 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-1. 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/m3; 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.

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Author Biography

Eri Ichikawa, Yokohama National University

Graduate School of Environment & Information Sciences

References

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Published

2018-06-27

How to Cite

[1]
T. Okutani, E. Ichikawa, H. Nagai, T. Hashimoto, and T. Makihata, “Crystalline silica in compressed rice hull coke ash”, J Met Mater Miner, vol. 28, no. 1, Jun. 2018.

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Original Research Articles