赤铁矿作用下煤化学链气化过程碳氮元素转化机理

Carbon and Nitrogen Conversion Mechanism During Coal Chemical Looping Gasification by Using Hematite as an Oxygen Carrier

以赤铁矿为载氧体,利用流化床反应装置比较传统煤气化与化学链煤气化的不同特性,同时研究气化温度、水蒸气流量、赤铁矿/煤比(即氧/碳摩尔比)、燃料种类等反应条件对化学链气化特性的影响,并分析气化反应后载氧体基本特性的变化。结果表明,化学链气化呈现2个不同的反应阶段。在初始的挥发分析出阶段,还原性气体与载氧体、NO x的氧化还原反应对碳、氮元素的转化具有重要影响,NO和N 2O均明显析出;在煤焦气化阶段,载氧体能够提高半焦反应活性、促进半焦气化和N 2O生成,N 2O是主要的NO x产物。赤铁矿载氧体中的Fe 2O 3在气化过程被还原、部分转化为Fe 3O 4,未发现载氧体烧结现象。

Hematite was used as an oxygen carrier to conduct coal chemical looping gasification in a fluidized bed reactor in order to investigate the different characteristics between conventional coal gasification and chemical looping gasification,and the influences of gasification temperature,steam flow rate,oxygen carrier to coal ratio(oxygen/carbon molar ratio)and fuel type on the performance of coal chemical looping gasification,and the changes in basic characteristics of oxygen carrier after gasification reaction.The results show that there are two different reaction stages during chemical looping gasification.In the initial volatilization stage,the redox reactions of reducing gas with oxygen carrier and NO x have a key effect on the conversion of carbon and nitrogen,during which both NO and N 2O are obviously released.In the following stage of coal char gasification,oxygen carrier improves the char reactivity,promotes char gasification and N 2O formation,when N 2O becomes main NO x product.In addition,the Fe 2O 3 component in hematite is partially reduced to be Fe 3O 4 and no sintering of oxygen carrier is observed during gasification.