| Pulverized coal firing boilers account for mostly in our electric power industry, but the large amount of NOx emission from the pulverized coal firing boilers do great harm to our environment.To strictly limit the pollutant gas emission, our country have issued the emission standard for the pulverized coal firing power plant.The new standard and charging for the pollutant have put the pulverized coal firing plants into a servere environment protection situation. Great efforts have to be taken to reduce the NOx in most of the pulverized coal firing power plants.At Present, there are two ways to decrease the NOx emission: the Low NOx Firing Technology and the Flue Gas Cleaning technology. Flue Gas Cleaning (SCR, i.e. selective catalytic reduction) are expensive to build and maintain comparing to the low NOx Firing Technology. Advanced low NOx firing technology can cut down the NOx concentration to 450-650mg/Nm3(O2=6%),450mg/Nm3 for bituminous coal.We have never rebuilt the low NOx firings system in the sub-critical unit ,so it is very meaningful to rebuilt the project.By analyzing the designed coal (shenfu dongshen coal) of the 600MW sub-critical unit and the performance parameters of the project, this paper aim to exploit a LNCFS (Low NOx Concentric Firing System) which will be suitable to the project.The main tasks of the thesis are as follows:Firstly: the design of the improved firing system;Secondly: the design of the improved distributed mode of the secondary air;Thirdly: the design of the improved primary and secondary air nozzle.Fourthly: forcasting the NOx emission of the project and giving proposals for the coming operation of the unit. On the basis of finishing the scheme of the project, numerical simulation is used to validate the amout of NOx ,And by the numerical simulation to test how the fineness of the coal,air distribution and other factors influence the performance of the boiler and then guide the operation of the boiler.
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