Redesign of combustion system in tangentially coal fired boiler of Limhamn district heating plant

摘要

The comprehensive methodology of industrial complete system redesigning towards reduction of combustion pollutants emission has been used at Division of Heat Technology. The methodology used to reduce emissions of CO, NO_x and particulates in complex industrial combustion system is based on complementary use of physical modeling and numerical simulation. Physical modeling is an easy way to simulate combustion and flow patterns by visualisation in cold, isothermal models. This is done in steps beginning with a burner model to investigate the flame and continuing with a boiler model to visualise the flow pattern and combustion process. These models must be used with certain similarity criteria to visualise real industrial process properly. This method is used to select the most efficient design for clean and efficient combustion process. The best result obtained from physical modeling experiments is then studied by using numerical simulations under the commercial CFD code Fluent. The Fluent code used in this work is a steady state/transient, finite volume, computational fluid dynamics program that can solve three-dimensional fields of pressure, velocity, temperature, kinetic energy of turbulence, dissipation rate of turbulence, and several chemical species. It operates by solving the governing differential equations of the flow physics by numerical means on a computational mesh and is able to predict gas velocity, temperature profile and concentration fields. Numerical modeling results are then used to analyze the performance of industrial boiler.