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Show generation capability. The combined effect, however, produces a time-concentration profile which is essentially constant from less than a microsecond up to and including the desired millisecond The treatment of radical chemistry in such an idealistic environment provides an indication of secondary gas effects and suggests experimental measurements to validate the modeling. EXPERIMENT AL EVALUATION A series of tests have been performed in the Radical Injection (RI) Test Facility at the DoE - Pittsburgh Energy Technology Center. These tests were intended to evaluate the viability of molecular radical injection as a technique for reducing pollutant emissions from combustion. Molecular radicals of ammonia, methane, and hydrogen were studied to detennine their effect on concentrations of nitric oxide in typical combustion gases. Tests were completed to evaluate the extent of ammonia discharge. Experimental Facility Figure 4 is a schematic of the PETC RI Test Facility. Fuel Oil #2 was burned in the 1.44 MW combustor and the exhaust gases were doped with up to 1000 ppm NO. There are two cooling sections prior to the test section which may be configured as refractory lined or water cooled. Variation of the cooling sections employed and adjustment of total combustor load make it possible to vary the flue gas temperature at the test section where the radicals are injected. Flow in the test section at approximately 4700 standard cubic feet per hour - [scfb] (5500 g-mole/hr) and a cross sectional area of 7.6 cm passes over a 2.5 cm diameter ceramic cylinder placed across the flow. At 1000 K, this corresponds to a flow of 30 m/s. This causes a significant low-pressure turbulent wake into which the radical stream enters, see Figure 5. Radicals (e.g. NH2, CHx, OH· ) are created by passing either nitrogen or argon gas through the annular region between the cathode and the anode of the plasma generator, see Figure 6. The plasma generator is the PETC Model 90, 40 kW DC Plasma Torch designed in cooperation with TAPA Inc. The torch was initially designed for surface coating applications and has not been optimized for radical generation. Plasma gas flow is limited to about 120 scfb (140 g-mole/hr), or 2.6 % of the total flow and about forty times that of the total NO flow. This makes it theoretically possible to saturate the flow with radicals without significantly effecting the ambient flow temperature when operated at low power. Although local temperatures in the flow will be effected, there is a virtual decoupling of the torch power and the flue gas temperature. Before the plasma stream is injected into the flue gases, additional chemical species may be added to enhance any desired effects such as radical production and performance. This addition is positioned to impart swirl which will enhance the mixing of these secondary species. Results of Ammonia Radical In jectjon Tests were completed using argon as the hot carrier gas with secondary injection of ammonia. Argon and ammonia flow rates through the PETC plasma torch were varied to assess the effect of changes on NOx reduction and ammonia breakthrough or slip. Power to the plasma torch was varied between zero and a maximum of 10 kW. The initial NOx concentration was approximately 600 ppm. At 1030 K, effective NOx reduction was achieved at a torch power of 1.5 kW. This surprisingly low power consumption, only 1 % of the power available to the combustor, was at the fringe of torch operation and was therefore difficult to control. Experimental data, shown in Figures 7 and 8, is bounded by 10% error bars which represent typical variations in performance. 4 |