Abstract Selective non-catalytic reduction (SNCR) has become an important technique for reducing NOx emissions in industrial furnaces. The occurrence of convective recirculation can cause significant changes in SNCR performance. This paper presents the results of a study performed by Computational Fluid Dynamics (CFD) considering: (i) changes of initial NOX; (ii) injection plan and (iii) NH3/NO molar ratio. The simulations have demonstrated that the convective recirculation (resultant from different injection plans and high temperature gradients) of flue gas assumes a role of vital importance for performance analysis of existing plants and the potential NOX reduction in furnaces during the design phase.

Cyclone models have been used without relevant modifications for more than a century. Most of the attention has been focused on finding new methods to improve performance parameters. Recently, some studies were conducted to improve equipment performance by evaluating geometric effects on projects. In this work, the effect of cyclone geometry was studied through the creation of a symmetrical inlet and a volute scroll outlet section in an experimental cyclone and comparison to an ordinary single tangential inlet. The study was performed for gas-solid flow, based on an experimental study available in the literature, where a conventional cyclone model was used. Numerical experiments were performed by using CFX 5.7.1. The axial and tangential velocity components were evaluated using RSM and LES turbulence models. Results showed that these new designs can improve the cyclone performance parameters significantly and very interesting details were found on cyclone fluid dynamics properties using RSM and LES.