The extent of coal combustion within the tuyere and raceway region is one key factor affecting the maximum pulverized coal injection (PCI) rate. Coal burnout strongly depends on the availability of oxygen. In this paper, a three-dimensional model is developed to simulate the lance-blowpipe-tuyere-raceway of a blast furnace. This model aims to describe the coal flow and combustion behaviors along the coal plume under different local oxygen enrichment ways. Room-temperature oxygen has two effects on coal combustion. On one hand, the cooling effect of oxygen delays the coal combustion. On the other hand, the oxygen content around the coal particles significantly increases, benefiting coal combustion. Therefore, aiming at different local oxygen enrichment ways, three different lance configurations, including a single coaxial oxygen-coal lance, a double oxygen-coal lance, and an oxygen-coal double lance, are designed. Under the single coaxial oxygen-coal lance, the burnout has the maximum increase of 4.05%. Under the double oxygen-coal lance, the burnout has the maximum increase of 12.51%. Under the oxygen-coal double lance, the burnout has the maximum increase of 12.84%. Therefore, the effect of different local oxygen enrichment ways should not be neglected.

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In this work, an improved comprehensive model was developed for large coal particles to predict temperature variation and volatile component yields. The kinetics model of volatile component yields, where the volatile matters were assumed to comprise nine species, was combined with heat transfer model. The interaction between volatile yield and heat transfer during pyrolysis of large Maltby coal particles was investigated. An apparent temperature difference has been observed between the surface and core of particles at the initial heating stage. The non-uniform temperature distribution inside coal particles causes non-simultaneous volatile yields release from the surface and core area. The volatile release occurs after the coal temperature rises higher than 350 °C, and its yield steeply increases within the temperature range of 450–520 °C. The peak of volatile release rate corresponds to about 485 °C due to the rapid release of tar and H2O. The tar is almost completely released at around 550 °C. With the increasing particle size, the difference in temperature and volatile yield between the surface and core increases at the end of heating. The results are expected to provide insights into the interaction between heat transfer and volatile yields during pyrolysis of large coal particles.

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