| OCR Text |
Show Measurement and Interpretation - 14 - of Flames Issued from a Generic Multi-Fuel Burner excess oxygen fuel spray angle combined firing combustion air staging : 0.5 to 5.0 % : from 50 to 900 : from 0 to 100 % : from 0 to 50 % IFRF-~ In addition, the effect of flue gas addition, atomizer design and natural gas rebuming were tested. 4.1. Baseline Oil Burner. The baseline oil burner is defined as the burner operating without fuel or air staging and without flue gas addition with a mass flow rate of heavy fuel oil set to 176 kg/h giving a thermal input of 2 MW from the fuel. The combustion air was preheated to 320°C with an excess air level of 10 %. The baseline burner was operated at a swirl number of 0.68. The atomizing steam flow rate was set to 10% w/woil. The oil was atomized with a standard, IFRF-designed, SOo Y-jet atomizer. A heat extraction of 1.3 MW was achieved using six cooling loops which gave a flue gas temperature in the exhaust of 983°C. The baseline flame had NOx emissions of 578 mg/Nm3 (dry, 3% 02,) with negligible amounts of CO. The particulate emissions for the baseline flame were 41 mg/Nm3 (dry, 3% 02). Detailed in-flame measurements of gas temperature, composition and velocities were carried out for these two flames which allow validation of mathematical models. The oil was supplied to the oil lance at a pressure of 6.4 bar and was atomized with 10 weight percent steam. The steam was introduced into the olllance at 162°C and S.9 bar and reached the saturation temperature at the tip of IS8°C. The oil entered the lance at 109°C and reached 114°C at the atomizer tip. 4.2. Parametric Measurements. 4.2.1. Combustion Air Staging. External air-staging as implemented utilizes design fundamentals determined in experiments in the Air Pollution (AP5-AP8) series demonstrated the potential for NOx reductions achievable in PC and heavy fuel oil firing as a result of externally staging the combustion air on the circumference of the burner head (see reports [4 -7] for further details). The results of Akiyama, (AP6), showed a NOx reduction of about 45% at 30% tertiary air staging. Fig. 4.1 shows the current results of external air staging expressed as the amount of tertiary air relative to the total flow rate of air. |
