Simulation of industrial boiler firing metallurgical gases
Abstract
Boiler units are widely used to generate heat and electrical power supply. At the integrated steel mill of interest, several industrial boilers combust a variable mixture of metallurgical and fuel gas to generate superheated high pressure steam suitable to be used in the station's expander turbine generators. In the context of firing metallurgical and fuel gases, the focus on thermodynamics and flow characteristics of gas phase combustion are placed in a prominent position. These boilers have experienced water-wall tube failures in the combustion zone, which thought to be caused by some deficiency in the combustion process. The challenge faced in this present process is that there are very limited means to observe the boiler operation thus identify the cause of the existing problems. A Computational Fluid Dynamics (CFD) combustion model has been developed, teaming up with Virtual Reality (VR) visualization, to investigate thermo-fluid characteristics under various operating and boundary conditions. CFD and VR visualization provide a compelling, non-intrusive and insightful modeling techniques in a cost-effective fashion. A quick comparison of the flame shape from the simulation results to the actual flame profile in the boiler showed a good agreement. Additionally, analysis of detailed flow patterns and system reactions to key variables (fuel ratio, flue gas oxygen percentage, etc.) have been conducted in order to address issues of low efficiency, static and thermal behaviors, inlet nozzle configurations, and water-wall tube failure. The goal is to solve the fire impingement problem to relieve the sidewall overheating as well as to improve the energy efficiency so that less fuel would be needed (especially natural gas which has to be purchased instead of self-produced). Parametric studies of operating parameters and/or possibility of reconstruction/adopting remedies like over-fire air (OFA) have also been conducted to improve fuel efficiency and prevent tube rupture; meanwhile explore the correlation between efficiency and NOx emission in order to meet the demand on both of efficiency and environmental restriction.
Degree
M.S.E.
Advisors
Zhou, Purdue University.
Subject Area
Mechanical engineering
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