Coal quality is essential for the optimum functioning of coal-fired power plants. One of the issues associated with coal quality deterioration is poor combustion behaviour which could result in ash deposition and environmental issues. This paper presents a CFD investigation of flow and combustion process in a full-scale furnace. Three different sub-bituminous coals with different properties were tested namely Coal A, B and C. The aim is to predict the combustion performance of these coals by observing its flow, temperature and species concentration inside the furnace. The exact boiler furnace geometry obtained from boiler operator was translated into CFD model with very little modification made for optimizing mesh. Grid dependency test carried out prior to the work shows the current mesh scheme is sufficient to accurately resolve the flow field. The results of the study show that combustion temperature for Coal B is the highest at approximately 1400°C. Coal C is predicted to give the highest velocity peak at certain regions of the furnace and interestingly enough, the same coal shows the shortest flame length and thus requiring additional flow to achieve the same penetration compared to other coals. Tracing of oxygen concentration inside the furnace show minimum oxygen left in the rear pass given by Coal A, indicating optimum combustion.

This paper presents a thermogravimetric analysis and combustion test for different coals used in a coal-fired power plant in Malaysia. The main objective is to investigate the suitability of adopting a newly-introduced sub-bituminuous coal in an existing boiler furnace commonly firing standard design coals. In order to ensure that the new coal will not give an adverse effect to the boiler, detail analytical and thermal performance of the new coal is investigated, together with design and other limiting coals. The combustion test was performed in a scaled down, 150kW, single swirl burner combustion test facility available in TNB Research Sdn. Bhd. In the study, combustion gas temperature at different sectors downstream of burner region is measured to determine the peak temperature for all tested coals. Based on the investigation, it was noted that coal with the highest fixed carbon content gives the highest temperature measure at all sectors. Similarly, coal with the lowest fixed carbon gives the lowest temperature. The temperature profile for the newly tested coal was found to be comparable to the design and limiting value coals. Even though it was observed that the temperature given by the new coal is the highest slightly downstream of the burner, the temperature was observed to be decreases as combustion gas flow downstream of the combustor rig. Based on the observation it can be said that the new coal is suitable to be used by the existing boiler furnace.

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