Laboratory investigation of an ultralow NO_x premixed combustion concept for industrial boilers

A combustion concept to achieve ultralow emissions (NO_x<=2 ppm and CO<=20 ppm) was tested on a 18 kW low-swirl burner (LSB). It is based on lean premixed combustion combusned with flue gas recirculation (FGR) and partially reformed natural gas (PRNG). Flame stability and emissions were assessed as a function of , FGR, and PRNG. The results show that PRNG improves flame stability and reduces CO, with no impact on NOx at =0.8. A one-dimensional flame simulation satisfactorily predicted prompt NOx under lean conditions with high FGR. Two catalysts were tested in a prototype steam reformer, and the results were used to estimate reactor volume and steam requirements in a practical system. An advanced Sud Chemie catalyst displayed good conversion efficiency at relatively low temperatures and high space velocities, which indicates that the reformer can be small and will track load changes. Tests conducted on the LSB with FGR and 0.05 PRNG show that boilers using a LSB with PRNG and high FGR andclose to stoichiometry can operate with low emissions and high efficiency.