OCR Text |
Show 10 burner radiant efficiency, but very little difference was seen in the overall radiant section efficiency of the test facility (surface radiation, gas phase radiation and convection). More significant differences were seen in the measured NOx emissions. With natural gas as fuel and 3 to 5 percent stack O2, the Pyrocore HT burner produced sub- 25 ppm NOx (corrected to 3 percent O2) over the range of test conditions. NOx emissions of less than 6 ppm were measured when operating over the same range of conditions with the purge gas fuel. These results are shown at 250°F and 500°F combustion air preheat levels in Figures 3 and 4. It is also important to note that no combustion stability problems were encountered when operating with the low Btu gas. REFORMER MODELING Reformer modeling was performed during the first year of the ARCS project by Kinetics Technology International, Inc. (KTI) for a downfired cabin-heater design. The goal of the ARCS project is to develop multiple-burner cabin heater combustion systems, but the initial field demonstration has targeted a smaller system as will be described in the following section. The reformer to be used for this demonstration is owned and operated by Air Products and Chemicals, Incorporated (APCI). A typical "small" reformer has a vertical cylindrical heater, and operates with floor mounted burners in an upfired configuration. After the selection of the field demonstration site, additional heater modeling was performed to select appropriate burner dimensions. This host site heater modeling was performed with assistance from APCI as part of their support of the ARCS project. APCI could use a commercially available code to model conventional flame burner performance in a heater, but no comparable code was available to model radiant burner performance. A zone model was developed by Alzeta that could predict surface-to-surface radiation, gas phase radiation, and convection. The surface-to-surface radiation model used burner surface temperature and emissivity data determined empirically from previous experimental data. Gas phase radiation is calculated using the method developed by Hottel, and convection was calculated using an empirical convective heat transfer coefficient. The code also assumed non-constant |