Laminar Burning Velocity and Markstein Length Characterisation of Compositionally Dynamic Blast Furnace Gas

Abstract

Blast Furnace Gas is a poor quality process gas comprising proportions of CO, H2, CO2, and N2, with a low energy density typically in the order of 3 MJ·kg−1. Produced in large quantities as a by-product of blast furnace iron making, it is one of the process gases indigenous to integrated steelworks worldwide. The inherently dynamic nature of furnace operation causes compositional variation and therefore leads to fluctuation in the fuel characteristics, often dissuading engineers from fully utilising the gas in increasingly complex and efficient technologies such as gas turbines. Characterisation studies were undertaken in a new constant volume bomb to determine the sensitivity to change in laminar burning velocity and Markstein length experienced as a result of increasing the volumetric H2 fraction in the range of 1–7%. Experiments were performed by measuring outwardly propagating spherical flame evolution, recorded using a Schlieren flame visualisation technique for a range of equivalence ratios, and processed using nonlinear data analysis. The relative performance of the experimental technique was benchmarked against other works using well-investigated CH4 and yielded results in good agreement with published values. Peak laminar burning velocity was shown to increase by a factor of approximately 3.5 over the tested range, with H2 concentration and equivalence ratio shown to greatly influence the effect of flame stretch. Comparisons of results were also made with values obtained from different reaction mechanisms employed using the PREMIX code developed by Sandia National Laboratories.