OCR Text |
Show adequate to reduce NOx with minimal by-product emissions. Prior to chemical injection, gas temperature was measured in the calciner. For a typical operating condition, gas temperature was about 1530°F at the top of the calciner. When the natural gas feedrate to the calciner was increased from 5% to 10% of the total heat input, this temperature increased to 1540°F. Temperature traverse in three foot increments showed a flat profile with less than 15°F variation indicating a good mixing inside the calciner. Temperature measured through bottom ports was 2070°F. This hot gas cools to 1550°F as it calcines the solids introduced from cyclone #4. Testing proceeded with a baseline test where NOx, O2, CO, and S02 at the stack were established for about 20 minutes. Chemical was then injected to compare the results with that of the baseline condition. However, fluctuations in kiln condition made it difficult to discern a response from the chemical injection or from fluctuations in kiln operating condition. To overcome this uncertainty, the measured NOx emission at the kiln exit was used as a baseline NOx value instead of NOx at the stack. Since all injection occurred in the calciner, NOx exiting the kiln is the untreated NOx or baseline NOx. In Figure 3, NOx emissions in pounds per hour at the stack without injection are compared with NOx emissions exiting the kiln. Data points are shown as square symbols and the solid line is a 45 degree line. If a correlation was linear and ideal, then all the squares would line up on the solid line. Although the points do not line up, the plot shows a reasonable correlation between the two, and thus, the kiln NOx was used as baseline NOx to calculate NSR and reductions. NOx NOx was efficiently and effectively reduced by the NOxOUT Process during all test conditions. NOx reductions as a function of NSR for all tests are shown in Figure 4. The reduction increased rapidly at a low NSR and reached a plateau of about 90% reduction at NSR of 2. Chemical utilizations, the ratio of NOx reduction and NSR, were greater than 70% at NSR 0.5 and 60% at NSR 1. These utilizations are higher than typically achieved in other NOxOUT applications (a typical utilization range between 30 and 50%). NOx emission rates in pounds per hour (pph) versus NOxOUT-A flowrate in gallons per hour (gph) are plotted in Figure 5. As shown, the NOx emission limit of 422 pph was reached between 20 and 40 gph or NSR of about 0.5. At higher flowrates, NOx was reduced to less than 100 pph. Injection location and baseline NOx had a negligible effect on NOx reduction while oxygen content slightly decreased the reduction. Comparison of the results .c. a. a. 600 ~----------------------------------~ o a a 550 ..................................................................................................................................... .. a a a 500 .......................................................................................................................................................... . ~M 450 .......................................................... 0' ............. . a a a 400 ......... 350 ......... 300 ~----~----~----~----~----~----~ 300 350 400 450 500 550 600 Kiln exit NO •• pph Figure 3 - Comparison of kiln exit NOx and stack NOx 100 80 <ft-c 60 .Q t5 :J U ~ OK 40 Z 20 0 0 0.5 1.0 1.5 NSR 0 2.0 2.5 3.0 Figure 4 - NOx reduction under various operating conditions 700 600 .c. 500 aa.. <Ii c: 400 0 iii III E 300 Cl) OK Z 200 100 0 0 40 NO. emissions limit = 422 pph 60 NOxOUT-A. gph 80 o o o 100 Figure 5 - Control of NOx emissions 120 |