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Show chamber. All testing was conducted in ambient air. Chamber pressures and temperatures were traversed (two directions) to determine entrainment. The last series of lab experiments compared measured flame lengths in ambient air. the kiln remained firing (nozzle only was retrofitted). The customer provided detailed product temperature data using a traveling thermocouple system for the baseline and retrofit cases. In addition, the customer provided record of product quality in each of the above cases. ff m High Velocity £ Burner 500,000 Btuh -" ^ Insulated Barrel & Entrained Air 16' I.D. P itot & Temperature Traverse Figure 4 Entrainment Test Rig Several brick plants participated in field testing slotted nozzles; one kiln will be presented in this report. The brick tunnel kiln investigated is primarily coal fired with burners mounted in the crown. There are 16 high velocity, gas-fired burners (also in the crown) located in the preheat zone. All of the preheat burners were retrofitted with slotted nozzles. The retrofit to all 16 burners was made while Burner nozzles used through most of the lab experiments, and all of the field tests, were constructed of a lightweight, composite ceramic material. The material can be made into a variety of shapes (see Figure 5), and can withstand furnace temperatures in excess of 2000°F. A woven ceramic fibrous material forms its base making the material very flexible. This mechanical characteristic is important in the design of the slotted nozzle, since the comers of the slotted shape give rise to stress concentrations. Monolithic refractories commonly crack at sharp comers. The aspect ratio (AR) of the slotted nozzles tested varied from 2.5 to 5.0. Nozzle mix, high velocity burners were used in all the test work. There were principle versions: a long 4" diameter burner especially designed for insertion into thick kiln crowns, and shorter burner that typically fits into a kiln side wall. The burners have different flameholder designs and can operate in excess of 8 0 0 % excess air. Outlet velocities, based on estimated flame temperatures, are between 200 and 300 fps. Generally, less than one third of the combustion takes place within the nozzle at capacity. This is done intentionally so as not to overheat the tile. Figure 5 Shaped Burner Tiles using Lightweight Composite Ceramics |
