Please join us for a special BAE seminar
FRIDAY, January 17, 2014
1:30 2:30 pm, 2045 BAINER HALL
Ignition, combustion and emissions of various pulverized coals and biomasses under different oxy-fuel O2/N2 and O2/CO2 Environments
Presenter: Reza Khatami
This work studied the ignition, combustion and emissions of burning pulverized coals and biomasses particles under either conventional combustion in air or oxy-fuel combustion conditions. Oxy-fuel combustion is a clean technology that takes place in O2/CO2 environments, which are achieved by removing nitrogen from the intake gases and recirculating large amounts of flue gases to the combustor. Removal of nitrogen from the combustion gases generates a high CO2-content, sequestration-ready gas at the combustor effluent. Flue gas recirculation moderates the high temperatures caused by the elevated oxygen partial pressure in the boiler. In this study, combustion of the solid fuels took place in a laboratory laminar-flow drop-tube furnace (DTF), electrically-heated to 1400 K, in environments containing various mole fractions of oxygen in either nitrogen or carbon-dioxide background gases. The experiments were conducted at two different gas conditions inside the furnace: (a) quiescent gas condition (i.e., no flow or inactive flow) and, (b) an active gas flow condition in both the injector and furnace. Eight coals from different ranks (anthracite, semi-snthracite, three bituminous, sub-bituminous and two lignites) and four biomasses from different sources (Sugarcane bagasse, olive residue, pine sawdust and torrefied pine sawdust) were utilized in this work.
The main objective was: (1) to experimentally study the effect of replacing background N2 with CO2, increasing O2 mole fraction and identifying the effect of fuel type/rank on a number of qualitative and quantitative parameters such as ignition/combustion mode, ignition temperature, ignition delay time, combustion temperatures, burnout times (reactivity), soot volume fractions and gaseous/particulate (ash) emissions. (2) to computationally predict the temperature and burnout times (reactivity) of different fuels with a comprehensive multi-scale, multi-phase and multi-component model of coal pyrolysis and combustion. The main characteristics of the model lie in a detailed description both of the kinetic mechanisms (pyrolysis, secondary gas phase and heterogeneous char reactions) involved in coal combustion processes and of the heat and mass transport resistances. A sensitivity analysis was performed to investigate the effects of uncertain parameters in the model such as gas heat capacity, binary molecular diffusivity, gasification reaction (C+CO22CO), particle size, fuel porosity, pore diameter and tortuosity on the predicted results.
Reza Khatami obtained his BSc in Mechanical Engineering (Thermal Fluid Sciences) from Tehran Polytechnique in 2001 and his MSc degree in Mechanical Engineering in Energy Conversion Systems from Sharif University of Technology in Tehran, Iran at 2005. He worked for NRI research institute in Tehran for one year and computationally (CFD) simulated the diffusion combustion in a pilot scale natural gas porous medium burner for residential and industrial applications. He also worked in HVAC design and energy simulations in private sector Oil, Natural Gas and Metal production industries (IRITEC, ITOK) before joining Northeastern University in Boston at 2008 to pursue his PhD. His research focused on the ignition and combustion of different coal ranks and biomasses in oxy-fuel environments. He is the writer of more than 12 peer reviewed journal publication in several prestigious journals such as Combustion and Flame, Energy and Fuels, Fuel, Proceeding of Combustion Institute, and Biomass and Bioenergy, 20 conference papers and 2 book chapters. He also served as a reviewer for more than 10 Journals and two international conferences. He is the recipient of several Awards including Yamamura Fellowship and he had the experience of writing several Grant Proposals for NSF as a co-PI.
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