Production of amorphous silica from rice husk in fluidised bed system

Conventional methods for the preparation of amorphous silica (SiO2) are very energy-intensive and expensive. Amorphous silica has wide industrial applications, with annual world consumption in the excess of 1 million tonnes valued at RM4,500 per tonne. Rice husk ash contains amorphous silica in the...

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Main Author:	Ngo, Saik Peng
Format:	Thesis
Language:	English
Published:	2006
Subjects:	TP Chemical technology
Online Access:	http://eprints.utm.my/id/eprint/1395/1/NgoSaikPengPFKK2006.pdf
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id	my-utm-ep.1395
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spelling	my-utm-ep.13952018-02-20T04:28:12Z Production of amorphous silica from rice husk in fluidised bed system 2006-02 Ngo, Saik Peng TP Chemical technology Conventional methods for the preparation of amorphous silica (SiO2) are very energy-intensive and expensive. Amorphous silica has wide industrial applications, with annual world consumption in the excess of 1 million tonnes valued at RM4,500 per tonne. Rice husk ash contains amorphous silica in the excess of 95 wt%. Thermal treatment of rice husk is deemed the most economical method to recover this amorphous silica from the readily available rice husk (approximately 0.5 million tonnes per annum in Malaysia). Hence, the purpose of this research was to recover amorphous silica from rice husk through thermal treatment in fluidised bed system. Experimental works were conducted in fluidised bed combustor systems to determine the optimum mixing parameters (sand size, fluidising velocity, static bed height) and combustion parameters (temperature, air supply, rice husk moisture content, feeding design) to produce amorphous, carbon-free silica from rice husk. The fly and bottom ashes were analysed for their residual carbon contents and silica structures through loss on ignition (LOI) tests and X-Ray Diffraction (XRD) analyses, respectively. Computational fluid dynamics (CFD) modelling using FLUENT was also conducted to optimise the fluidised bed design and to overcome problems encountered in experimental works. Experimental results showed that amorphous, siliceous ash with residual carbon content of down to 1.0 wt% could be obtained by burning water-washed rice husk that was free from alkali metal compounds (potassium oxide and sodium oxide). The short freeboard height of the experimental fluidised bed resulted in the incomplete oxidation of carbon and sand contamination in the ash. Modelling results showed that both problems could be overcome by increasing the height of the fluidised bed to 5000mm. In addition, the induction of swirling flows at the freeboard region was found to be beneficial in increasing the residence time of ash in the combustor, leading to higher carbon burnout 2006-02 Thesis http://eprints.utm.my/id/eprint/1395/ http://eprints.utm.my/id/eprint/1395/1/NgoSaikPengPFKK2006.pdf application/pdf en public phd doctoral Universiti Teknologi Malaysia, Faculty of Chemical and Natural Resources Engineering Faculty of Chemical and Natural Resources Engineering
institution	Universiti Teknologi Malaysia
collection	UTM Institutional Repository
language	English
topic	TP Chemical technology
spellingShingle	TP Chemical technology Ngo, Saik Peng Production of amorphous silica from rice husk in fluidised bed system
description	Conventional methods for the preparation of amorphous silica (SiO2) are very energy-intensive and expensive. Amorphous silica has wide industrial applications, with annual world consumption in the excess of 1 million tonnes valued at RM4,500 per tonne. Rice husk ash contains amorphous silica in the excess of 95 wt%. Thermal treatment of rice husk is deemed the most economical method to recover this amorphous silica from the readily available rice husk (approximately 0.5 million tonnes per annum in Malaysia). Hence, the purpose of this research was to recover amorphous silica from rice husk through thermal treatment in fluidised bed system. Experimental works were conducted in fluidised bed combustor systems to determine the optimum mixing parameters (sand size, fluidising velocity, static bed height) and combustion parameters (temperature, air supply, rice husk moisture content, feeding design) to produce amorphous, carbon-free silica from rice husk. The fly and bottom ashes were analysed for their residual carbon contents and silica structures through loss on ignition (LOI) tests and X-Ray Diffraction (XRD) analyses, respectively. Computational fluid dynamics (CFD) modelling using FLUENT was also conducted to optimise the fluidised bed design and to overcome problems encountered in experimental works. Experimental results showed that amorphous, siliceous ash with residual carbon content of down to 1.0 wt% could be obtained by burning water-washed rice husk that was free from alkali metal compounds (potassium oxide and sodium oxide). The short freeboard height of the experimental fluidised bed resulted in the incomplete oxidation of carbon and sand contamination in the ash. Modelling results showed that both problems could be overcome by increasing the height of the fluidised bed to 5000mm. In addition, the induction of swirling flows at the freeboard region was found to be beneficial in increasing the residence time of ash in the combustor, leading to higher carbon burnout
format	Thesis
qualification_name	Doctor of Philosophy (PhD.)
qualification_level	Doctorate
author	Ngo, Saik Peng
author_facet	Ngo, Saik Peng
author_sort	Ngo, Saik Peng
title	Production of amorphous silica from rice husk in fluidised bed system
title_short	Production of amorphous silica from rice husk in fluidised bed system
title_full	Production of amorphous silica from rice husk in fluidised bed system
title_fullStr	Production of amorphous silica from rice husk in fluidised bed system
title_full_unstemmed	Production of amorphous silica from rice husk in fluidised bed system
title_sort	production of amorphous silica from rice husk in fluidised bed system
granting_institution	Universiti Teknologi Malaysia, Faculty of Chemical and Natural Resources Engineering
granting_department	Faculty of Chemical and Natural Resources Engineering
publishDate	2006
url	http://eprints.utm.my/id/eprint/1395/1/NgoSaikPengPFKK2006.pdf
_version_	1747814375922597888

Production of amorphous silica from rice husk in fluidised bed system

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