Numerical modelling of pollutant formation in a lifted methane–air vertical diffusion flame

Alechenu Audu Aboje,Ambali Saka Abdulkareem,Edison Muzenda,Aisha Abubakar Faruq,Mohammed Umar Garba,Geun Young Yun

doi:10.1080/23311843.2017.1302543

Alechenu Audu Aboje, Ambali Saka Abdulkareem + Show 4 more

Open Access

https://doi.org/10.1080/23311843.2017.1302543

Copy DOI

Abstract

AbstractA comparison of turbulence and combustion models have been performed for predicting CO2 and NOx formation from a methane diffusion flame firing vertically upwards. The flow field has been modeled using the Reynolds-Averaged Navier–Stokes equation incorporating the k-e realizable turbulence closure model, the k-ω shear-stress transport (SST) turbulence model and the transitional SST turbulence model and the three models have been compared. Combustion was modeled using the unsteady Stationary Laminar Flamelet Model (SLFM), the Eulerian Particle Flamelet Model (EPFM), and the Pollutant Model (PM) and the three models have also been compared. Numerical predictions show good agreement with experimental data. Furthermore, the experimental data showed that the k-e realizable turbulence model and the k-ω SST turbulence model performed better than transitional SST model in predicting the pollutant species from the flame. The result also shows that the PM performed better than flamelet models in predicting ...

Highlights

Gas flaring is the controlled combustion of waste hydrocarbon gases from oil field and oil refinery activities due to lack of infrastructure to harness the gases
The chemistry of the flame is strongly coupled with the turbulence and a higher turbulent kinetic energy or turbulence intensity will increase mixing in the flame, leading to a faster consumption of the fuel
This can be observed in a radial plot of the mixture fraction at three axial locations (Figure 5(a–c)) where the transitional stress transport (SST) severely under-predicted the concentration of methane at the flame axis when compared with the experimental data

Summary

Introduction

Gas flaring is the controlled combustion of waste hydrocarbon gases from oil field and oil refinery activities due to lack of infrastructure to harness the gases This process is associated with the undesirable formation of pollutants, such as CO, NOx, unburned hydrocarbons, smoke as well as CO2. Previous experiments (Brookes & Moss, 1999) have shown that that very low concentrations of soot are present in lifted methane jet diffusion flames at atmospheric pressure. This accounts for the non-luminous appearance and higher temperature in these flames as observed by Bandaru and Turns (2000). NOx emissions have been observed to be higher in methane–air flames than in propane–air flames due to the higher flame temperatures as well as the greater entrainment of air in methane flames compared to propane flames (Lyle, Tseng, Gore, & Laurendeau, 1999; Wang, Endrud, Turns, D’Agostini, & Slavejkov, 2002)

Objectives

Results

Conclusion