Oxy-fuel combustion needs recycled flue gas to reduce furnace temperature for material protection. The enhanced CO₂ alters coal devolatilization behavior. Devolatilization (albeit very quick) determines the whole life of coal in furnace, and thus it is essential to clarify the effects of CO₂ gas media on coal devolatilization behavior. However, previous works achieved conflicting results due to operation condition and coal nature differences. The present work attempts to investigate this issue and explore the influence of devolatilization temperature and alkali/alkaline earth metal. For this purpose, five coals with three coal ranks and different mineral compositions were devolatilized within N₂ or CO₂ by using a drop tube furnace under 800−1200 °C. Char produced in CO₂ has much more mesopores and as much as 2.8–8.1 times (depending on coal type) specific surface area than char produced in N₂, but the combustion reactivity is slightly lower. These differences are due to the additional CO₂ gasification contribution. With increasing devolatilization temperature or inherent Ca content, the impact of CO₂ on devolatilization behavior is more pronounced. Difference in char surface morphology was observed only for high-Ca coal.

含氧燃料燃烧需要再循环烟道气以降低炉温，以保护材料。增强的CO ₂改变了煤的脱挥发分行为。脱挥发分（尽管非常快）决定了煤在炉中的整个寿命，因此有必要弄清楚CO ₂气体介质对煤脱挥发分行为的影响。然而，由于工作条件和煤性质的不同，以前的工作取得了矛盾的结果。目前的工作试图调查这个问题，并探讨脱挥发分温度和碱金属/碱土金属的影响。为此，在N ₂或CO ₂中将具有三种煤等级和不同矿物组成的五种煤脱挥发分。通过在800-1200°C下使用滴管炉。与N _2中产生的炭相比，CO _2中产生的炭具有更多的中孔，比表面积最多是N _2中产生的炭的2.8-8.1倍（取决于煤类型）。这些差异归因于额外的CO ₂气化作用。随着脱挥发分温度或固有Ca含量的升高，CO ₂对脱挥发分行为的影响更加明显。仅在高钙煤中观察到炭表面形态的差异。