The influence of biomass fuel replacing coke breeze on flame front and combustion efficiency were studied. The results show that when coke breeze is replaced, the flame front is accelerated since biomass has superior combustion characteristics. Combustion efficiency is decreased, however, as biomass is of excessively high reactivity, which can both lower the maximum temperature and reduce the time at high temperature of the sinter bed. The proportion of biomass fuel replacing coke breeze should, therefore, not exceed 40%, otherwise, the mineralisation of sinter material is insufficient and the yield and tumbler index of sinter significantly deteriorate. By increasing the size of biomass fuel, sinter indices are improved since the burning velocity of biomass fuel is optimised. When the proportion of biomass fuels is 40%, the emissions of SO₂ and NO can be decreased by 40 and 28% respectively.

The structure of granules has been investigated and a model of granulation determined. The results show that a granule consists of an adhesive layer and a nucleus. Particles with diameter under 0.5 mm act as adhesive fines, while the remainders act as nuclei. By studying the influencing factors of granulation, two significant particle characteristics assessing granulation performance were determined. One is the relative proportion of adhesive fines and nucleus particles, and the other is the specific surface area of adhesive fines. The method of optimising granulation of sinter mixtures is proposed as follows: the proportion of adhesive fines should be 40–50% and the specific surface area should exceed 1000 cm² g⁻¹, which contributes to achieving a better bed permeability, a faster sintering speed and higher productivity.

SiO₂ and Al₂O₃ are two important minerals that can affect the mechanical and metallurgical properties of sinter. This investigation systematically studied the influences of these minerals and revealed their functional mechanisms on sinter quality. Results showed that with an increasing Al₂O₃ content in sinter, the sintering indexes presented an improvement before the content exceeded 1.80%, while the quality decreased obviously after the content exceeded 1.80%. With an increasing SiO₂ content, the sinter quality presented a decreasing tendency, especially when the content exceeded 4.80%. Consequently, the optimal content of Al₂O₃ was ≤1.80% and that of SiO₂ was ≤4.80%. The evolution of the microstructure and minerals in sinter showed that enhancing the Al₂O₃ content increased the proportion of SFCA generated, which improved the sinter’s mechanical strength, while excessive Al₂O₃ led to the formation of sheet-like SFCA with weak mechanical strength. Increasing the content of SiO₂ strained the formation of SFCA and promoted the formation of calcium silicate, the mechanical strength of which is lower than that of SFCA. The research findings will be useful in guiding practical sintering processes.