含氧/蒸汽气氛中煤高温分解产物分布及反应性

在流化床反应器中考察了含氧/水蒸气气氛中煤在850 ℃下的热解特性,包括产物分布特性及生成的半焦与焦油的反应性,研究了温度、过量空气比(Equivalence ratio: ER)和水蒸气/煤比(S/C, 质量比)的影响。结果表明,随热解温度、ER和S/C质量比的增加,气体产率增加,而半焦和焦油产率减少。O₂的加入使CO₂、CO含量明显增加,H₂含量降低。O₂和水蒸气的加入使半焦的比表面积显著增加,半焦气化活性增强,但半焦在900 ℃和 ER 为0.22的条件下出现轻微石墨化,降低了其气化活性。同时,反应气氛中含有O₂和水蒸气对焦油的性质有显著影响,与单纯的N₂气氛相比,O₂和水蒸气的存在使热解焦油中单环芳烃、酮类、酚类、脂肪烃都明显减少,这对于焦油的进一步裂解及重整更加有利。

Product distribution and reactivity of coal pyrolysis at high temperature and in atmospheres containing O2/steam

The product distribution and reactivity of coal pyrolysis at temperatures up to 850 ℃ and in atmospheres containing O₂ and steam were studied. The effects of reaction temperature, equivalent air ratio (ER) and the mass ratio of steam to coal (S/C) were examined. The gas yield increased with the increases of the temperature, ER and S/C, whereas the yields of char and tar correspondingly decreased. When O₂ was present in the atmosphere, the CO₂ and CO productions obviously increased, while that of H₂ decreased. The simultaneous presence of O₂ and steam in the atmosphere improved the specific surface area and reactivity of the resultant char. However, the gasification reactivity of char produced at 900 ℃ in N₂ and/or in an atmosphere with an ER 0.22 at 850 ℃ was low because of occurrence of carbon graphitization. The inclusion of O₂ and steam into the atmosphere had a great effect on the tar properties. Compared with pyrolysis in pure N₂, the tar produced in O₂ and steam contained fewer single-ring aromatics and phenolic, ketonic and aliphatic hydrocarbons, which made the tar more reactive for cracking and reforming.