Numerical Modelling of Waste Incineration and the Effect of Flue Gas Recirculation on Pollutant Reduction

Abstract

The operation of an incinerator inevitably results in the release of greenhouse gases and nitrogen oxides (NOx), which are detrimental to human health. To minimize pollutant gas emissions and maximize energy efficiency, it is essential to thoroughly study combustion properties. Optimizing operational conditions, such as temperature and oxygen levels within the combustion chamber, is crucial for reducing pollutant release and enhancing the combustion performance of an incinerator freeboard. Achieving this optimization requires the development of reliable approaches based on computational fluid dynamics (CFD) modeling. ANSYS FLUENT is used to study and optimize the combustion behavior of a community incinerator of size 250 kg/hr. Results are obtained under considered cases i.e. different mass flow rates (50%, 75% & 100%) of the waste. The effect and prospects of exhaust gas recirculation with different rates on the NOx gas emission levels after combustion is also shown. For the case 1 (Air fired), the mass fraction percentage of oxygen was 23% and nitrogen was 77% in inlet air. For the case 2 (O2 fired), the mass fraction percentage of oxygen was 23% and CO2 was 77% in inlet air. For the case 3 (O2 fired), the mass fraction percentage of oxygen was 25% and CO2 was 75% in inlet air. And it is seen that the temperature and NOx emission increase gradually with increase of mass flow rate. For the 100% loading, it is also evident that NOx formation has reduced by 57.35% and 41.4% for the O2 fired cases 1 and 2 respectively