Pilot Plant Experiment And Simulation Research On No_x In Oxy-fuel Combustion Technology

The emission amount of CO₂ increases year by year in world-wide, and the results brought by it are becoming more and more serious, which are green-house effect, global extreme climate, land flood. As the world's second-largest country in CO₂ emissions, china gets more pressure in Post-Kyoto era. Oxy-fuel technology is a new kind of technology to reduce the CO₂ discharge amount. Meanwhile, It can achieve the removal ofmultipollutants synchronization,such as NOx,SOx and so on. A pilot plant test rack of oxy-fuel first inland is set up in the paper, and NOx discharge behavior is researched in the oxy-fuel condition. Experiments in four conditions, which is air, O2+CO₂, O2+RFG(cold) and O2+RFG(hot), are carried out in the pilot plant test rack, by burning a lean coal. The temperature, O2, CO, NOX distribution field in furnace hearth are measured and compared for two conditions of air and O2+CO₂. It indicates that, CO₂ concentration in flue gas is up to 90% in the oxy–fuel technology with micro positive pressure furnace. As the combustion fume emission decreases largely, the NOx volumetric concentration in furnace outlet is higher than air condition, but when translated into mg per kg coal, the concentration will be slashed. In the O2+RFG(h) condition NOx discharge amount is 2450.37 mg per kg coal, which is 53.47% lower than in air condition. It mainly owing to the high CO concentration in the furnace, and the loop decomposition of NOx. The denitrification rate and desulfurzation percent is 83.56% and 93.36% respectively by sprinkling calcium in the furnace in the O2+RFG(h) condition.The numerous simulations are carried out in the commercial software FLUENT to simulate the combustion in the pilot plant test rack. Through by mesh generation and model choosing, two conditions of air and 30%O2+70%CO₂ are studied, and the excess coefficients are both 1.2. It indicates that, the maximum temperature in furnace in oxy-fuel condition is a little higher, and the CO concentration is 40% higher than in air condition. The maximum and average concentration of NOx in the furnace is higher in Oxy-fuel condition than in air. The results of simulation and experimental is compared, it turns out that the result of numerical simulation is confirm to the experimental measurement values. It indicates that the model and analogue method used in numerical simulation is appropriate. The simulation study shows that, by adopting oxy-fuel technology the NOx discharge is evidently low. The concentration of CO in combustion is much higher than in air atmosphere. That is also the main reason. And the thermal field is similar to the one in the air atmosphere. It means that it is feasible to use oxy-fuel technological to reform the existing coal combustion boiler.