Numerical investigation of adding water vapor to air of combustion in an industrial boiler

Environmental issues and air pollution have attracted a lot of attention in recent years. Thermal power plants are among the air pollutants. One of the solutions used for better combustion and less pollution in other combustion systems, including gas turbines, is the idea of ​​water vapor injection. In this study, it was considered that with the idea of ​​adding water vapor to the gas turbine, a similar work would be done in the boilers, for which in this research, a 11 Megawatts single axisymmetric burner in the form of two dimension is modeled using the open source software OpenFoam and the ReactingFoam solver. For simulation, the equations for mass, momentum, energy, and species conservation were solved together as a coupling, and the pressure corrections in the momentum equations was performed according to the PIMPLE algorithm. The model used for the turbulence is the  model, the radiation model fvDOM, the combustion model used PaSR model and the reaction mechanism GRI-3, which includes 53 species and 325 reactions. To validate the solver and the models used, a standard problem was used which is a simple burner and its experimental results are available. After proving the correctness of the solution, the mentioned problem was simulated. It was observed that in the dry air combustion chamber, the temperature and, consequently, the NOx output are high. The flame temperature decreased after the steam injection in three proportions by 5, 10, and 15% of the total inlet air, so that the temperature in the axisymmetric boiler decreased by 370 Kelvin. Also, in the axisymmetric boiler, the amount of NO output decreased 81 % and the amount of output decreased 76%. However, carbon pollutants, specifically for CO which was important in this studyincreased by 58% to 17 ppm but was still much lower than national and European standards.