OCR Text |
Show ton of oxygen used, the breakeven oxygen cost is $275 per ton oxygen. The cost of oxygen depends on methods of oxygen generation, size of plant, and location. For example, it ranges from about $50 per ton of oxygen produced by a large on-site facility to about $120 per ton for delivered liquid . N9.x Emissions As previously stated, the Linde "A" Burner design overcomes the problems associated with conventional oxygen combustion, such as high flame temperature and high NOx emissions. A recent study sponsored by the Department of Energy (DOE)[8] obtained extensive NOx data on various oxygen-enriched combustion conditions using natural gas. The burners tested represent both conventional air-fired designs and oxygen/fuel burners designed primarily for very high oxygen levels. As shown in Figure 4, the NOx emissions peak between 35 and 50~ 02 levels for all test conditions. The absolute levels of the NOx emissions also depended on both the furnace temperature and burner design. With pure oxygen, the "A" Burner produced its lowest NOx emissions: less than 0.05 Ib NOx/MMBTU. This compares to 0 . 10 Ib NOx/MMBTU for air burners . In the Denney Fa~ field demonstration, NOx level was continuously monitored and recorded. Due to the air infiltration which is discussed in a later section, the effective 02 enrichment level was about 40 to 45~ 02 in the rotary kiln. The NOx emission level was about 100 to 120 ppm at 15~ C02 (or 0.15 to 0.18 Ib NOx/MMBTU), which was slightly higher than the previous air system levels (at about 50 PPM at 10~ C02 or 0.11 Ib NOx/MMBTU) . This NOx emission level using diesel fuel was twice as high as comparable data in the above DOE study using natural gas. However, since the specific fuel consumption of the modified MIS was reduced by 60~, the NOx emission per ton of contaminated soil was in effect reduced. It is anticipated that further NOx reduction cao be achieved by (1) reducing air into the kiln, (2) using steam instead of 'air as an oil atomization fluid for the oxygen burner and (3) reducing excess oxygen level in the rotary kiln . Flame Stability and Operational Flexibility During operation of the EPA/MIS, good flame stability and operational flexibility were also achieved with the Linde Oxygen Combustion System. A number of system stability tests were conducted with various feed materials at different feed rates. Disturbances were generated to test the dynamic response of the burner system, such as by cycling liquid waste feed and water spray. Satisfactory system response and flame stability were demonstrated in all the tests conducted[l). It has also been demonstrated that very light ve~iculite can be processed through the system with very little particulate carryover. Tests with mixtures of brominated sludge, soil and sodium sulfate have also been successful. During the entire 14-week demonstration period, no system downtime was attributed to the Linde System. COMPUTER MODELING Different types of industrial furnaces have been successfully modeled in the past. A mathematical model for a rotary kiln based incineration system was developed in this case to aid the design and optimization of oxygen firing. This model perfo~s both heat and mass balances and heat transfer analyses. - 6 - |