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Hydrothermal Conversion of Neutral Sulfite Semi-Chemical Red Liquor into Hydrochar

School of Engineering, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
School of Applied Chemical and Environmental Sciences, Sheridan Institute of Technology, 7899 McLaughlin Road, Brampton, ON L6Y 5H9, Canada
Author to whom correspondence should be addressed.
Academic Editor: Kent Hoekman
Energies 2016, 9(6), 435;
Received: 27 March 2016 / Revised: 25 May 2016 / Accepted: 30 May 2016 / Published: 3 June 2016
(This article belongs to the Special Issue Organic Waste/Resources to Energy and Value added Product)
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Hydrochar was produced from neutral sulfite semi-chemical (NSSC) red liquor as a possible bio-based solid fuel for use in power generation facilities. Hydrothermal conversion (HTC) experiments were conducted using a fixed liquor-to-water volume ratio of 1:8 and reaction time of 3 h. Solutions were processed using different chemical additives, pH and temperature conditions to determine the optimum conditions required for producing a high energy content solid fuel. The hydrochar samples produced were analyzed by ultimate, thermogravimetric (TGA) and Fourier transform infrared spectroscopy (FTIR) analyses to determine physicochemical properties that are important for utilization as a fuel. The residual process liquids were also analyzed to better understand the effect of HTC process conditions on their properties. It was determined that the optimum conditions for producing a solid fuel was at a reaction temperature of 250 °C, in the presence of acetic acid at pH 3. The maximum energy content (HHV) of the hydrochar produced from red liquor at this condition was 29.87 MJ/kg, and its ash content was 1.12 wt.%. This result reflects the effect of increasing reaction temperature on the physicochemical characteristics of the hydrochar. The increase of HTC temperature significantly reduces the ash content of the hydrochar, leads to a significant increase in the carbon content of the hydrochar, and a reduction in both the oxygen and hydrogen content. These effects suggests an increase in the degree of condensation of the hydrochar products, and consequently the formation of a high energy content material. Based on TGA and FTIR analyses, hydrochars prepared at high HTC temperature showed lower adsorbed moisture, hemicellulose and cellulose contents, with enrichment in content of higher temperature volatiles, such as lignin. View Full-Text
Keywords: red liquor; hydrothermal conversion; hydrochar; higher heating value; ash content; thermogravimetric analysis red liquor; hydrothermal conversion; hydrochar; higher heating value; ash content; thermogravimetric analysis

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Gamgoum, R.; Dutta, A.; Santos, R.M.; Chiang, Y.W. Hydrothermal Conversion of Neutral Sulfite Semi-Chemical Red Liquor into Hydrochar. Energies 2016, 9, 435.

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