Simulation of combustion and thermal flow in an industrial boiler with NOx predictions

Disposal of municipal solid waste (MSW) is one of the major problems in many urban areas and can be considered a serious global environmental issue. Incineration has become the most environmental-friendly method of disposing waste and it is important for recovery of energy from waste which reduces the net release of carbon dioxide to the atmosphere and eliminates the production of methane from landfill. Computational fluid dynamics (CFD) modelling is used in the development phase and very useful tool for simulation modelling of the complex geometry and flow conditions in incinerators. CFD modelling and flow simulation with detailed parametric variations of design variables of an industrial scale MSW incinerator was done using ANSYS FLUENT to simulate the combustion and thermal flow and to determine velocity profiles, temperatures, and NOx distributions. In order to minimize the pollutants emission from the MSW incinerators, an improved mixing of air is formulated to increase oxidative destruction of incomplete combustion by secondary air injection into the combustion chamber. The results predicted that the NOx formation in the boiler is highly depended on the combustion processes along with the temperature and species concentrations. It has shown that over-fire air (OFA) operation is a good way to reduce the NOx emissions from the boiler