Research On Oxygen-enriched Combustion Characteristics Of 670t/h Pulverized Coal Boiler

The oxygen-enriched combustion technology is an effective energy saving one and gradually becomes the popular spot researched in the world. Compared with the use of ordinary air for combustion, the coxygen-enriched gas stream could effort to reduce the ignition temperature, accelerate burning speed, raise the flame temperature, reduced excess air coefficient and so on. Currently, the rapid development of membrane science and technology has solved the cost problem, so the oxygen-enriched combustion technologies in power plant boilers would be of a practical value.In this thesis, a boiler in capacity of 670 t/h is taken as the object. Before and after using the oxygen-enriched air combustion equipment, the tests of the boiler are carried involved in the balance coal consumption, coal consumption for power supply and anti-equilibrium efficiency. The author uses FLUENT software for numerical simulation to the actual boiler combustion process. In the numerical simulation the total oxygen-containing substances are constant. When the boiler load is 210 MW, the oxygen concentration of the primary air is respectively 27%,29%,31%,33%. The affect of the primary air and secondary air on combustion conditions is studied.The test results show that the carbon contents in fly ash and ash carbon, the supply coal consumption and coal consumption are decreased, and the thermal efficiency of the boiler improved after using the oxygen-enriched air combustion equipment. When the boiler operates under high loads, increasing the oxygen volume fraction in combustion air may strong the burning process.The numerical results show that the furnace average temperature increased from 1413.2 K to 1447.1 K with the oxygen concentration increase. The flame becomes longer and the flame temperature becomes higher. With the change of the secondary air volume, the upper and lower flame temperatures become higher significantly, and the flames become thinner and shorter. The furnace average temperature increases from 1413.2 K to 1439 K.When the oxygen concentration increases, NOx emission concentration at the furnace outlet increases firstly and then decreases. NOx emission concentration is highest when the oxygen concentration was 29%. It is 1.64 times compared with 21% oxygen concentration. On the other hand NOx emission concentration at the furnace outlet fluctuates, and the highest emission concentration is under the 33% oxygen concentration.For changing primary air volume, the best oxygen concentration should be 27%～29%. For Changing secondary air volume, the oxygen concentration should not be exceed 29%.