生物质灰对铁矿石载氧体性能的影响
Effect of biomass ash on performance of iron ore as oxygen carrier in chemical looping combustion

在小型固定床上以铁矿石为载氧体、CO为燃料,进行了化学链燃烧试验.通过在铁矿石中加入生物质灰,探讨了生物质灰的种类(玉米秆灰、油菜秆灰和稻草灰)、灰的添加量(5%~20%)及灰中碱金属对铁矿石载氧体反应活性的影响.试验结果表明:生物质灰中无机组分不同,对铁矿石载氧体反应活性的影响也不同.由于玉米秆灰和油菜秆灰中碱金属K含量较高,高温下K以气态形式迁移到铁矿石表面,生成了K3FeO2,从而提高了铁矿石的还原反应活性.稻草灰中Si含量很高,高温下碱金属K及FeO与铁矿石反应,生成低熔点共晶体,加剧了铁矿石表面的烧结,减少了气固反应的接触面积,导致CO总转化率急剧下降.
Experiment on chemical looping combustion was conducted in a fixed bed reactor with iron ore as oxygen carrier and CO as fuel. The effect of biomass ash addition on the performance of the iron ore oxygen carrier was investigated. Several key factors were discussed, including the biomass ash type(corn stalk ash, rape stalk ash, straw ash), the ash ratio(5% to 20%)and the alkali metal in the ash. The results indicate that the effect of the biomass ash on the reactivity of iron ore depends on the chemical composition of the ash. The alkali metal K abundant in corn ash and rape ash is released in gaseous state and captured by iron ore through complicated reactions, forming K3FeO2 which enhances the reduction reactivity of the iron ore. However, the high content of Si in the straw ash leads to a reaction of Si with K and FeO under high temperature to form low melting point compounds which causes serious sintering on the surface of the iron ore. The decrease of contact surface causes the decrease of the total CO conversion