Master of Science
Abstract Power plant generates electricity as well as high temperature waste heat. NOx is main pollutant in power plant flue gas. NOx reduction reaction is expected to happen in given duct section. Selective non-catalytic reduction (SNCR) method is selected to control NOx level. SNCR requires no modification on duct geometry and this method is more cost-effective compared to other NOx reduction systems. Computational fluid dynamics (CFD) technique is employed to simulate flue gas flow and mass and heat transports with an injection of droplets. One tenth scaled duct model is adapted to decrease calculation time span. Water is injected into duct instead of ammonia because water does not need special treatment before spraying. Injection locations are varied, results are compared and the optimum location of injection is identified. The effects of parameters including Re number (580, 5800,58000), mass flow rate of injected water (1kg/s, 0.1kg/s, 0.001kg/s), and particle concentrations (12,000, 120,000 particles) are studied. A set of operating parameter promoting a good mixing in the waste duct is determined. Average temperature is kept at 1290K for all simulations. Mass flow rate of 5x10-5 kg/s and inject diameter of 4.9 x10-5 m together with the injection location coordinate of (-0.05, 0.165,0) provide favorable mixing for reduction of NOx. This study aims in designing and optimizing NOx reduction in flue gas using Ansys software.
Shen, Ze, "Simulation of Nox reduction in power plant flue gas" (2017). Theses and Dissertations. 2930.