Crystalline silica in compressed rice hull coke ash
Keywords:Rice hull coke, Ash, Potassium Cristobalite, Respirable crystalline silica, Combustion
AbstractCompressed rice hull coke was produced by compressing rice hulls ground to less than 200 Âµm diameter at 1.22x106 N/m2 and 310ËšC 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 kJÂ·kg-1. In this study, 2 kg coke was combusted at the average temperature of 850ËšC for 104 min with a maximum temperature of 860ËšC. 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 Âµm 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.
B. O. Juliano, “Chapter 19: Rice Hull and Rice Straw,” in Rice: Chemistry and Technology, B.O. Juliano (Ed.), St. Paul (Minesota): The American Association of Cereal Chemists Incorporated, 1985, pp. 689-755.
J. James, and M. S. Rao, “Characterization of Silica in Rice Husk Ash,” American Ceramic Society Bulletin, vol. 65, pp. 1177-80, 1986.
Y. Nakata, M. Suzuki, T. Okutani, M. Kikuchi, and T. Akiyama, “Preparation and properties of SiO2 from rice hulls,” The Journal of the Ceramic Society of Japan International edition, vol. 97, pp. 830-836, 1989.
C. Real, M. D. Alcalá, and J. M. Criado, “Preparation of Silica from Rice Husks,” The Journal of the American Ceramic Society, vol. 79, pp. 2012-2016, 1996.
R. V. Krishnarao, J. Subrahmanyam, and T. J. Kumar, “Studies on the formation of black particles in rice husk silica ash,” The Journal of the European Ceramic Society, vol. 21, pp. 99-104, 2001.
A. Proctor, “X-ray diffraction and scanning electron microscope studies of processed rice hull silica,” Journal of the American Oil Chemists' Society, vol. 67, pp. 576-584, 1990.
L. Sun and K. Gong, “Silicon-Based Materials from Rice Husks and Their Applications,” Industrial & Engineering Chemistry Researh, vol. 40, pp. 5861-5877, 2001.
T. Okutani, T. Utsumi, and M. Ohnishi, “Synthesis of Conjunctive Zeolite-Activated Carbon Composite Adsorbent from Rice Hulls for Simultaneous Adsorption of CO2 and H2O,”in 42nd International Conference on Environmental System, San Diego,2012, pp.2012-3429.
E. Natarjan, A. Nordin, and A. N. Rao, “Overview of Combustion and Gasfication of Rice Husk in Fluidized Bed Reactors,” Biomass and Bioenergy, vol. 14, pp. 533-546, 1998.
Air quality-particle size fraction definitions for health-related sampling, ISO Standard 7708: 1995.
International Chemical Safty Cards: 0809 (cristobalite), 0808 (quartz), 0807 (tridymite).
Japan Society of Occupational Health, “Statement of reason for provisional value of permission level of dust,” The Journal of Occupational Health, vol. 53, pp. 204-209, 2011.
S. Liu, N. Liu, and J. Li, “Silicosis Caused by Rice Husk Ashes,” The Journal of Occupational Health, vol. 38, pp. 57-62, 1996.
M. K. Sharma, W. S. Williams, and A. Zangvil, “Formation and Structure of Silicaon Carbide Wiskers from Rice Hulls,” The Journal of the American Ceramic Society, vol. 67, pp. 715-720, 1984.
Takada Engineering Ltd., “Multi-fluidized bed combustor of rice hulls,” Japan Patent 4396843, Jan. 13, 2010.
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