Degree of NOx Reduction in a Gas-fired Cylindrical Furnace via Air Staging

Furnaces have many practical applications such as heating and steam generation in industrial units, buildings, etc. Increasingly stringent standards for NOx emission necessitate carrying out more research on furnaces and employing the available techniques for NOx reduction. In this paper, methane combustion in a horizontal furnace with circular cross-section is simulated to study the effect of air staging on NOx emission from the furnace. The governing equations of flow, turbulence, energy, combustion, and radiation model are solved numerically using the flow solver Fluent 6.2. Combustion in a natural gas-fired furnace is simulated to verify the simulation methodology and the solution algorithm. Results are compared with existing experimental and numerical data and reasonably good agreement is observed. According to the results, air staging reduces NO formation by about 11.1% in the furnace of the present study. In addition, a 10.6% increase in thermal efficiency of the furnace is obtained through air staging, while CO emission does not change significantly and increases only about 2.9%.

Keywords:

NOx reduction , Air staging , Gas-fired furnace , Diffusion combustion , CFD