Characterizing pulverized coal combustion for high-ash content Indian coal

ABSTRACT

The present study performs three-dimensional (3D) numerical simulations of coal combustion of four samples with varying ash content in a drop tube furnace (DTF) to mimic the particle heating rates observed in industrial furnaces. The numerical framework adopted is validated with prior experimental and simulation results using a 3D cylindrical geometry and a very good match is obtained for the axial temperature distribution and particle burnout rate. The combustion performance of coal samples with varying ash contents of 2.3, 16.6, 24.1, and 37.2 wt%, is explored through temperature profiles, burnout rates, particle tracking, and mass fractions of various products of combustion. A user-defined function is used to specify the 14 species, 10-step solid particle combustion with a modified eddy dissipation concept model for volatile combustion. The range of ash content considered is for Indian coal which has a high degree of heterogeneity, making the evaluation of its combustion performance, a challenge. The present work aims to provide benchmark set of results showing the evolution of the evaporated, charred, and volatile mass for the three ash contents, which has not been attempted before. It is found that the high-ash content Indian coal samples have a tendency to produce less $N{O}_x$. A $9.52\mathrm{\%}$ reduction in the $N{O}_x$ is obtained for the coal sample with $37.2\mathrm{\%}$ ash compared to that with $16.6\mathrm{\%}$ ash. The results suggest that the combustion performance is enhanced when the ash content falls within an optimum range of $20-35\mathrm{\%}$.

KEYWORDS:

• Coal combustion
• high ash coal
• drop tube furnace
• particle dynamics
• computational fluid dynamics

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Additional information

Notes on contributors

Aditi Sengupta

Aditi Sengupta is an Assistant Professor in the Department of Mechanical Engineering at IIT Dhanbad. She holds a PhD in Engineering from the University of Cambridge, UK. Her current research interests are in high performance computing, computational combustion, hydrogen and flow control.

Sandipan Kumar Das

Sandipan Kumar Das is a Professor in the Department of Mechanical Engineering at IIT(ISM) Dhanbad. He holds a PhD in Mechanical Engineering from Stanford University, USA and his current research interests are in Turbulence Modeling theory, Population Balance models in multiphase flows, Boundary Integral Methods and Green Energy.

Barun Kumar Nandi

Barun Kumar Nandi is currently working as Associate Professor at the Department of Fuel and Mineral Engineering, IIT Dhanbad. He holds a PhD in Chemical Engineering from IIT Guwahati. His current research interests include thermochemical conversion, coal and biomass processing, membrane separation process, wastewater treatment, fuel processing technology.

Piyush Sharma

Piyush Sharma is currently affiliated with SRM Institute of Science and Technology Chennai as Assistant Professor in the Department of Mechanical Engineering. He holds a Ph.D from I.I.T Kanpur in the Department of Materials Science and Engineering with specialization in Concentrated Solar Power and his current research interests are in experimental evaluation of high temperature thermal energy storage and volumetric absorbers for power production and metallurgical applications.