To study the influence of fluidized-bed reactor scale-up on coal gasification characteristics, a model of the ash agglomerating fluidized-bed reactor has been developed using an equivalent reactor network method. With the reactor network model, the scale-up effects of a gasifier were studied in terms of the characteristics of the chemical reactions in the jet zone, the annulus dense-phase zone and the freeboard zone. Results showed that the changes occurred in the inequality proportion of the volume of the jet zone during the reactor scale-up. Taking into consideration the utilization of a portion of the backflow gas, the expansion of the jet zone volume and the coal particle residence time, the temperature of the jet zone was increased from 1592 to 1662 K. Also, both the annulus dense-phase zone temperature and the freeboard zone temperature decreased, causing subsequent decrease in the carbon conversion efficiency. (c) 2014 American Institute of Chemical Engineers AIChE J, 60: 1821-1829, 2014