Mechanical/thermal dewatering of lignite. Part 4: Physico-chemical properties and pore structure during an acid treatment within the MTE process

► Mechanical Thermal Expression (MTE) dewatering of lignite. ► Alkali cation removal by acid treatment. ► Pore volume reduction with increasing MTE process severity. ► Moisture holding capacity correlates with pore volume in MTE products. ► Physical properties of MTE products are not differently inf...

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Bibliographic Details
Published in:Fuel (Guildford) 2012-03, Vol.93, p.433-442
Main Authors: Vogt, Christian, Wild, Thomas, Bergins, Christian, Strauß, Karl, Hulston, Janine, Chaffee, Alan L.
Format: Article
Language:English
Subjects:
Acid treatment
Applied sciences
Carbon
Dewatering
Energy
Energy. Thermal use of fuels
Exact sciences and technology
Fuels
Lignite
Mechanical Thermal Expression
Mercury intrusion porosimetry
Moisture
Physico-chemical properties
Porosity
Pycnometry
Sodium
Waste water
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Summary:► Mechanical Thermal Expression (MTE) dewatering of lignite. ► Alkali cation removal by acid treatment. ► Pore volume reduction with increasing MTE process severity. ► Moisture holding capacity correlates with pore volume in MTE products. ► Physical properties of MTE products are not differently influenced by acid versus water treatment. The Mechanical Thermal Expression (MTE) process is a dewatering process carried out at moderately elevated temperatures and pressures. In this study, the MTE dewatering behaviour of lignite/water and lignite/acid slurries of six coal samples from Australia, Germany and Greece were compared. The extent of alkali cation removal was also studied, along with the COD of the wastewater, as an indicator of the amount of organic carbon loss. Furthermore, the physical changes that the lignite experiences at different MTE process temperatures and acid concentrations were evaluated using mercury porosimetry, helium pycnometry, moisture holding capacity and CO2 adsorption methods. Total pore volume, residual water content, and sodium and potassium content were significantly reduced with increasing severity of the MTE process. Acid treatment improves the removal of inorganics but has less significant effects on the water removal and the physical properties of the dewatered lignite. Furthermore, a decrease in moisture holding capacity at high dewatering temperatures correlates with a reduction of the pore volume.
ISSN:0016-2361
1873-7153
DOI:10.1016/j.fuel.2011.08.049