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Kinetic modeling of gasification reactions of CO2 and H2O for Thar lignite char at elevated pressures

Imran Nazir Unar, Abdul Ghani Pathan, Rasool Bux Mahar, Ghulamullah Maitlo, and M. Aslam Uqaili

Department of Chemical Engineering, Mehran University of Engineering and Technology, Jamshoro, Pakistan

 

E-mail: imran.nazir@facutly.muet.edu.pk

Received: 4 May 2020  Accepted: 9 July 2020

Abstract:

Gasification reactions of Thar coal chars with CO2 and H2O have been investigated, using pressurized thermo-gravimetric analyzer (PTGA). A quartz fixed-bed reactor was used to prepare coal char at 900 °C with a nitrogen environment. Dynamic heating segments were maintained with a constant heating rate during all experiments. The temperature was raised from room temperature to 1000 °C, at different pressures 1 atm., 5 atm., and 10 atm. using pure reacting gases (CO2 and H2O). The weight loss data obtained from PTGA results were used to study the kinetic behavior of Thar lignite char for gasification reactions with CO2 and H2O as gasifying reacting species. It was observed that gasification reactions of char with reacting gas CO2 and char with reacting gas steam (H2O) initiated at 750 °C and completed after reaching 950 °C, at atmospheric pressure, but the occurrence of reactions was slightly delayed at high pressures. Volumetric Model and Grain Model were used to develop a kinetic model for Thar lignite. The direct plot and integral methods were used to calculate Arrhenius parameters such as the pre-exponential factor (A) and activation energy (E). An increase of A and E was also observed in increasing pressures. The activation energy (E) was investigated from 244.64 to 317.6 kJ/mol at atmospheric pressure; whereas, it is lying in the range of 286.13–356.67 kJ/mol at a pressure of 10 atm.

Keywords: Coal; Gasification; Kinetic modeling; Thar lignite; PTGA

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-020-01284-1

 

Chemical Papers 75 (1) 169–190 (2021)

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