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• Industrial experiments of down-fired boiler with bituminous coal under various loads are taken. • The ignition heat of coal/air flow under different coal varieties and loads is given. • Burning bituminous coal has a large furnace flame fullness under the low-load. • Strong combustion stability is determined by the low ignition heat and high furnace temperature under the low-load. • The combustion performances of bituminous coal and anthracite under the low-load are analyzed and compared. The new energy generating capacity is increasing year by year in the electric industry structure, but it is greatly influenced by the natural conditions. Coal-fired power generation unit boilers connected to the grid have the ability of flexible peak-load regulation and long-term low-load operation is required. However, the combustion stability is weak under the low-load when the coal-fired boiler burning anthracite. Down-fired boiler fueled with bituminous coal gradually attract the attention. Ignition and combustion stability, burnout, and NO x emissions are experimentally studied under the various loads on a 300 MW down-fired boiler fueled with bituminous coal, and the results compared with anthracite under the low-load. The ignition distance of the coal/air flow burning bituminous coal is gradually advanced with the reduction of load. And under the corresponding load, the ignition heat of the coal/air flow when burning bituminous coal is more than 37% lower than that burning anthracite. With the reduction of load, the decreasing rate of the overall furnace temperature and the cross-sectional heat load in the primary combustion zone decreases, and the furnace temperature in the primary combustion zone is high under the low-load when bituminous coal is burned. Short ignition distance, low ignition heat and high furnace temperature ensures the strong combustion stability of burning bituminous coal under the low-load. Moreover, under three various loads with burning bituminous coal, the carbon in the fly ash are all less than 1.1%, and the NO x emissions at the furnace exit are 410, 397 and 288 mg/m3 @ 6% O 2 , respectively. [ABSTRACT FROM AUTHOR]

• The combustion and gas emission characteristics of CGFA were studied. • The CGFA lacks fixed carbon secondary combustion stage. • The model-free method and the model method estimate the kinetics parameters. • Determine the best combustion model of the samples. The activation energy of samples was calculated using the model-free method and the model method (typically 46 mechanism functions). The model method is suitable for water scrubbing ash (WSA), and the model-free method is suitable for raw coal (RC), dry ash (DA) and WSA. In the model-free method, the Kissinger method not only guarantees the accuracy of the reduction activation energy E value, but also takes into account the calculation amount of the replacement. The Kissinger method is the better method for the replacement activation energy E value. The average estimated value of DA's E of Kissinger method is 107.89 kJ/mol, which is lower than 143.30 kJ/mol of Yangquan anthracite. The average estimated value of WSA's E is 82.10 kJ/mol, which is slightly higher than that of lean coal (77.54 kJ/mol). It shows that the combustion performance of DA is better than that of Yangquan anthracite, and the combustion performance of WSA is equivalent to that of lean coal. Comprehensive combustion characteristics and gas emission results show that the CGFA has combustibility and utilization value. [ABSTRACT FROM AUTHOR]