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Dewatering Studies on the Low Rank China Lignite Using N2, CO2 and Air

[+] Author Affiliations
Wei Chen, Yunlei Wang

China University of Mining and Technology, Xuzhou, China

Kalyan Annamalai, Jiafeng Sun

Texas A&M University, College Station, TX

Zhimin Xie

Global Engineering and Materials, Inc., Princeton, NJ

Paper No. GT2015-44035, pp. V003T03A013; 8 pages
  • ASME Turbo Expo 2015: Turbine Technical Conference and Exposition
  • Volume 3: Coal, Biomass and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration
  • Montreal, Quebec, Canada, June 15–19, 2015
  • Conference Sponsors: International Gas Turbine Institute
  • ISBN: 978-0-7918-5667-3
  • Copyright © 2015 by ASME


The integrated gasification and combined cycle (IGCC), uses low rank coal (higher moisture and volatile contents and lower heating value) as fuel for gasification (e.g Texaco gasifier of Tampa electric with low ash coal) and convert the solid fuel into synthetic gas mainly consisting of CO and H2. During the storage of fresh low rank but highly reactive coals near the IGCC plants, the coals undergo drying and low temperature atmospheric oxidation which raises the temperature, reduces the moisture and eventually causes spontaneous ignition if the temperature rises above about 800 °C in the coal piles for bituminous and 500 °C for lignite coals. Thus it is of interest to understand the dewatering mechanism of the low rank lignite by drying samples using N2, CO2 and air (which represents partial oxidation) as drying mediums. Fundamental experiments were performed on dewatering of coal samples using thermo-gravimetric analysis (TGA) with different particle sizes and drying mediums. A wide range of drying temperatures from 100 to 225 °C with a step of 25 °C was investigated at a residence time of about 30 minutes. There are no significant differences among moisture weight loss curves for the three drying mediums. It was found that the lignite lost only 5% mass at about 100 °C. With further increase in temperatures most of the mass loss occurred within the temperature range of 120 to 170 °C. The maximum moisture release rate occurred for the temperatures between 125 °C and 140 °C and hence serves as the optimal temperature range for removing the moisture. When drying temperature was below 140 °C, highest moisture release rate occurred in N2 environment while for CO2 environment, optimal temperature rose beyond 140 °C. The structure of the dewatered lignite samples were further investigated through Scanning Electron Microscopy (SEM) studies. When experiments were repeated in air, ignition occurred and corresponding ignition temperatures were obtained. The larger particles reveal lower ignition temperatures.

Copyright © 2015 by ASME



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