Numerical study of the effect of primary air velocity of pulverizer output on NOx formation in the boiler of Labuan steam power plant, Indonesia

The challenges faced by the electricity industry in Indonesia at present with a considerable generating capacity. One of them is the problem of variations in coal calories and fuel prices. Besides that, it also relates to the amount of generating capacity which has an impact on the amount of NOx gas release which has the potential to disturb the environment. By understanding the mechanism of optimization and setting of the pulverizer in this case the primary air velocity settings that coming out of each pulverizer output line can improve the performance of the generator itself and reduce NOx gas. By setting the primary air velocity at the outlet the process of forming fireball is more perfect which influences a better combustion process. Thus, the purpose of this research is to obtain the condition of setting the primary air velocity so that it causes the combustion process to produce exhaust gas with NOx content that meets the applicable criteria. In this study the Computational Fluid Dynamics (CFD) method is used. The boiler geometries are made using Gambit software and for numerical simulations using ANSYS Fluent software 19.2. For validation, the initial simulation results for the current boiler conditions are compared with actual measurement data. Furthermore, it will be simulated by varying the primary air velocity. The simulation results show that the effect of increasing in velocity outlet of pulverizer on the combustion temperature in the furnace (without changing secondary water) is inversely proportional. The greater the velocity outlet pulverizer, the lower the combustion temperature in the furnace. So that the recommended model design is a variation of the velocity outlet of pulverizer with a speed of 28 m/s because it has a superheater inlet temperature slightly above the existing model, so that the use of superheater and reheat spray only slightly adds to the existing model while for NOx mass fraction boiler output is around 65% of the existing model.