Effect of combustion temperature on the unburnt carbon during ammonia co-firing with coal combustion

Ammonia co-firing with coal seems to be the preferred approach to reduce unburnt carbon in existing pulverized coal-fired power plants. However, some operational conditions such as combustion temperature need to be carefully considered. As such, this study investigated the effect of combustion temperature on the unburnt carbon during ammonia co-firing with pulverized coal. Horizontal tube furnace with ammonia injection was employed and operating at different combustion temperature (800 to 1200 ^oC). Proximate analysis results showed that the raw coal sample contained 64.2 wt% fixed carbon. Additionally, based on the several analyses employed to assess the effect of combustion temperature efficacy on the unburnt carbon reduction, an effective combustion efficiency was achieved with ammonia co-firing with coal. X-ray fluorescence results revealed that SiO₂ for the co-firing experiment decreased from 56.7476 wt% (800 ^oC) to 45.9423 wt% (1200 ^oC) while carbon decreased from 20.06 to 18.32 wt%, at the same combustion temperature respectively. X-ray diffraction also revealed a well-defined peak at 2θ = 25^o, a graphite characteristic, which decreased significantly with increasing temperature, signifying unburnt carbon reduction. Thus, it can be confirmed that ammonia co-firing with coal can be used to improve the combustion efficiency coal fired power plants.