The composite agglomeration process (CAP) aims at sintering a pelletized feed and a matrix feed together to produce a high-quality burden for a blast furnace. The pelletized feed is balled from fine iron concentrate or refractory iron-bearing resources, while the matrix feed is granulated from iron ore fines, fuels, fluxes and so on. Through mathematical calculation, heat accumulation regularity and heat-homogenizing of the sinter bed are acquired in CAP when pelletized feed is uniformly distributed. Then they are studied in the composite agglomeration process with optimized pelletized feed distribution, which is a novel and perfect sinter bed structure. Results show that large heat input gaps exist in the sinter bed under condition of even sinter mixture distribution, and it is very difficult to realize bed heat-homogenization by directly varying the solid fuel dosage among each layer. An optimized pelletized feed distribution realizes more heat in the upper layer together with heat-homogenization of the middle-lower layer when the proportions of pellets increase first in the middle-upper layer and then decrease in the middle-lower layer of the sinter bed. Under these circumstances, the sinter bed has much better available accumulation ratios with a maximum value of 78.29%, and possesses a greater total heat input of 6754.27 MJ when the coke breeze remains at the original dosage. To make full use of the available heat accumulation and adjust the pellet distribution, a good energy saving effect is obtained because the coke breeze mass declines by 13.91 kg/t-sinter. The current gross heat inputs of each unit are reduced remarkably, leading to a total heat input decrease of 25.95%. In pot tests of CAP, the differences of thermal parameters in whole bed are obviously reduced with the optimized pelletized feed distribution, which contributes to sinter homogeneity and energy savings.

Pyrolysis and combustion behaviors of three coals (A, B, and C coals) were investigated and their combustion kinetics were calculated by the Freeman–Carroll method to obtain quantitative insight into their combustion behaviors. Moreover, the effects of coal size, air flow, oxygen content, and heating rate on coal combustion behaviors were analyzed. Results showed that the three coals have a similar trend of pyrolysis that occurs at about 670 K and this process continuously proceeds along with their combustion. Combustion characteristics and kinetic parameters can be applied to analyze coal combustion behaviors. Three coals having combustion characteristics of suitable ignition temperature (745–761 K), DTG_max (14.20–15.72%/min), and burnout time (7.45–8.10 min) were analyzed in a rotary kiln. Combustion kinetic parameters provide quantitative insights into coal combustion behavior. The suitable particle size for coal combustion in a kiln is that the content of less than 74 μm is 60% to 80%. Low activation energy and reaction order make coal, especially C coal, have a simple combustion mechanism, great reactivity, be easily ignited, and a low peak temperature in the combustion state. Oxygen-enrichment and high heating rates enhance coal combustion, increasing combustion intensity and peak value, thus shortening burnout time.