Numerical simulation of co-firing oil palm fronds and lignite coal injected at different burning rates in tangential pulverized coal burner

Reducing CO₂ emissions and utilizing biomass, particularly palm oil mill waste, is crucial for addressing climate change, enhancing air quality, and advancing environmentally sustainable clean technology innovations. Palm fronds can serve as a renewable fuel source with minimal emissions, providing a viable co-firing option for coal in coal-fired power plants (PLTU). Although previous studies have shown promising CO₂ emission reductions through co-combustion of oil palm fronds and coal, there is still no comprehensive analysis of the combustion characteristics and emission behavior when varying the burner injection zone, thus further research is required. This study performs a numerical analysis using three-dimensional computational-fluid dynamics (CFD) to examine the co-burning process of palm fronds alongside low-calorie coal (LRC) at the Pacitan PLTU, which has a capacity of 315 megawatts. The co-burning simulation, incorporating a 5% substitution of palm fronds in each burner, was conducted to differentiate between burners A and D, aiming to determine the optimum injection area. The findings of the simulation reveal inconsistencies in combustion properties, particularly regarding temperature allocation. The primary results demonstrate a temperature rise when palm fronds are used as a co-firing fuel, attributed to their greater volatility and oxygen content compared to coal. The most notable decrease in CO₂ emissions was observed with the substitution of 5% oil palm fronds in burner B; however, the reduction was not substantial, as indicated by a mass fraction value of 0.128 at the boiler discharge. An increase in NOx mass fraction was also observed due to the organic nitrogen in palm frond biomass, which decomposes rapidly during combustion at high temperatures. This co-firing technology is expected to provide a means for lowering emissions and improving the use of alternative fuels as a substitution for fossil fuels in a time to come.