Low NOx heavy fuel oil combustion with high temperature air

For an industrial-scale test furnace, the development and investigation of a heavy-oil-fired burner in a highly preheated air combustion system are discussed. The 1200 °C highly preheated combustion air was achieved by burners equipped with regenerators in high-cycle reciprocal firing. It was observed that the high-cycle reciprocal firing enhanced convective heat transfer to the furnace wall. Reduction of nitric oxide emissions was achieved by fuel directly injected into furnace (F2 mode) and mixed with combustion products. In previous studies of natural gas combustion in reciprocal firing, two injectors located at the burner quarl have been utilized to achieve low nitric oxide combustion. In this study, reduction of nitric oxide was investigated using single or paired atomizers located in the upper and lower position of burner quarl. It was found that buoyant forces were important for the mixing of fuel oil with high temperature air and for the resultant nitric oxide emission. Nitric oxide emission was found to be low with the paired atomizers in the F2 firing mode. Nitric oxide emission can be further reduced by use of a single atomizer rather than using paired atomizers.