Design and development of a SPMB (self-aspirating, porous medium burner) with a submerged flame

This work reports design and development of a SPMB (self-aspirating porous medium burner) for replacing the self-aspirating, CB (conventional gaseous fuel, free flame burners), which are widely used in heating process of SMEs (small and medium scale enterprises) in Thailand but they have relatively low thermal efficiency of about 30 percent. Design of the SPMB relies on the same important characteristics of the CB, i.e. using the same mixing tube and the same fuel nozzle. The SPMB is formed by a packed bed of alumina spheres. The pressure drop across the packed bed, diameter of particles and a combustion chamber diameter are estimated by Ergun’s equation in combination with Pe (Peclet number). The SPMB yields a submerged flame with an intense thermal radiation emitted downstream. An output radiation efficiency as high as 23 percent can be achieved at relatively high turn-down ratio of 2.65 and firing rate ranging from 23 to 61 kW. The SPMB shows a more complete combustion with relatively low CO emission of less than 200 ppm and acceptably high NOx emission of less than 98 ppm as compared with the CB throughout the range of firing rate studied, suggesting the possibility of the SPMB in replacing the CB.