Ultra-low NOx emissions from catalytic hydrogen combustion

The objective of this work is to determine the nitrogen oxide emission in the flue gas of a catalytic hydrogen combustion process, operating without premixed hydrogen and air supply. The study was investigated on a novel designed gas under glass stove top burner, suitable for domestic kitchen applications. The basic catalytic burner assembly consists of two platinum coated silicon carbide (SiC) foam disks with a diameter of 150 mm, a thickness of 10 mm and a porosity of 60 and 80 pores per inch (ppi) respectively. The two catalytic SiC disks are stacked with 10 mm space between for a uniform air feeding and distribution. Hydrogen is supplied from below the assembly and air is blown in between the two Pt coated catalytic SiC disks, leading to a homogeneous air distribution and thus a uniform catalytic reaction of hydrogen and air. Tests are performed at hydrogen flow rates of 5, 10 and 15 Nl/min, equivalent to 0.9, 1.8, 2.7 kW power, the hydrogen to oxygen ratios (φ) were fixed to 0.66, 0.5 and 0.33 respectively. Ultra-low nitrogen oxide emissions of 0.09 ppmv to 9.49 ppmv, equivalent to 0.007 to 0.37 mg/kWh are achieved with this novel developed catalytic combustion design. These values are significantly lower than the present EU regulation of 56 mg/kWh for combustion processes of gaseous fuels for heating applications. This result shows the very high potential of converting hydrogen to heat without harmful exhaust gases for a broad domestic application in decarbonised gas grids or stationary power to gas applications.