Numerical simulation of coal particle size (fineness) effect to combustion characteristics of sub-critical pulverized coal boiler 600 MW capacity

Abstract

The use of coal with a lower quality than the coal design resulting in the un-optimation of the combustion process so that it will affect the unit performance or efficiency. Coal quality problems are not solely from the calorific value parameter but also on Hardgroove Grindability Index (HGI), this HGI value will affect to coal particle size (fineness) that goes into the furnace. Some of the impacts of the particle size bigger than standard size are the more unburn carbon, increasing the slagging fouling potential, and increasing the residence time of coal that will affect the furnace exit gas temperature is higher. Simulation with CFD is an effective and efficient solution to determine the effect of fineness on the boiler combustion characteristics. In modeling the gas phase combustion process, a mixed fraction approach is used with the probability density function (PDF) method. The input and boundary condition data are determined based on data collected when operating 600 MWe and for calculating coal particle size distribution using Rosin-Rammler law. The simulation is carried out by varying the three sizes of fineness, namely those that pass the 200 mesh sieve with 70%, 60% and 50%. The results obtained in the form of temperature and velocity distribution of combustion products to find out in any area in the boiler that potentially high level of erosion and where intensive particle deposition can occur, and to show the impact of particle size on un-burned carbon (UBC).The use of coal with a lower quality than the coal design resulting in the un-optimation of the combustion process so that it will affect the unit performance or efficiency. Coal quality problems are not solely from the calorific value parameter but also on Hardgroove Grindability Index (HGI), this HGI value will affect to coal particle size (fineness) that goes into the furnace. Some of the impacts of the particle size bigger than standard size are the more unburn carbon, increasing the slagging fouling potential, and increasing the residence time of coal that will affect the furnace exit gas temperature is higher. Simulation with CFD is an effective and efficient solution to determine the effect of fineness on the boiler combustion characteristics. In modeling the gas phase combustion process, a mixed fraction approach is used with the probability density function (PDF) method. The input and boundary condition data are determined based on data collected when operating 600 MWe and for calculating coal pa...