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.

In the sintering of iron ores, the partial substitution of anthracite for coke breeze has been considered to be an effective way of reducing pollutant emissions and production cost. In this study, the basic characteristics of anthracite and coke breeze were compared and the sintering performance at different substitution ratios of anthracite for coke breeze was investigated. The porosity of anthracite is lower than that of coke breeze, but its density and combustion reactivity are higher. The substitution of anthracite for coke breeze has no influence on the granulation effect of the sintering blend. As the anthracite proportion increased, the sintering speed and productivity increased and the sintering yield and tumbler index decreased. As the substitution ratio increased from 0 to 60%, the melting temperature duration and the melt quantity index decreased from 2.59 to 2.03 min and from 3218.28 to 2405.75 °C·min, respectively, leading to insufficient sintering mineralization and bad sintering indexes. For an anthracite substitution ratio of 40%, the sintering speed, sintering productivity, sintering yield and tumbler index were 22.34 mm min⁻¹, 1.49 t·(m² h)⁻¹, 71.65% and 63.59%, respectively, which entirely satisfies the production requirements. Furthermore, hematite (Fe₂O₃), calcium ferrite (CaO–Fe₂O₃), and compound calcium ferrite (CaO–SiO₂–Fe₂O₃) were the major mineral phases, which were embedded with an interwoven structure.

During the iron ore sintering process, its SiO₂ content considerably affects the sinter quality. In this study, the effect of SiO₂ content on iron ore sintering indexes was studied, with mineral composition and microstructure analyses. It was shown that the strength and reducibility of sintering products improved when SiO₂ content increased. The sinter yield and tumbler index increased from 69.57% and 58.67% to 74.02% and 62.32%, respectively, with SiO₂ content increasing from 3.92% to 5.12%. Moreover, the reduction disintegration index (RDI_+3.15) increased from 66.50% to 68.28%. There was a quadratic function relationship between SiO₂ content (x) and RDI_+3.15 (y): y = −0.4841x² + 5.8932x + 50.8189. Maintaining the SiO₂ content in the range of 4.52% to 5.12% would promote the formation of compound calcium ferrite (SFCA) and silicate as the main binding phase which determined the quality of sintering products.