准东煤半焦赤铁矿载氧体化学链燃烧及碱(土)金属迁移特性  

Chemical-looping combustion characteristics of Zhundong coal semicoke with hematite oxygen carrier and transformation of alkali and alkaline earth metals

作　　者：刘银河[1,2] 王儒儒 关昱 林啸龙 王博 王园园 LIU Yinhe;WANG Ruru;GUAN Yu;LIN Xiaolong;WANG Bo;WANG Yuanyuan(State Key Laboratory of Multiphase Flow in Power Engineering,Xi’an Jiaotong University,Xi’an 710049,China;School of Energy and Power Engin-eering,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]西安交通大学动力工程多相流国家重点实验室,陕西西安710049 [2]西安交通大学能源与动力工程学院,陕西西安710049

出　　处：《煤炭学报》2024年第2期1148-1160,共13页Journal of China Coal Society

基　　金：陕西省重点研发计划资助项目(2021GXLH-Z-088)。

摘　　要：准东煤在常规燃烧利用过程中出现严重的积灰结渣和CO_(2)排放等问题,极大地限制了其低碳清洁高效利用。采用中低温热解低阶煤生产半焦、焦油和热解气是煤炭分质分级利用的龙头技术,准东高碱煤热解半焦气化活性高,采用化学链燃烧方式有利于实现其低碳清洁高效转化。以CO_(2)为气化介质,赤铁矿石为载氧体,在固定床上开展准东煤半焦原位气化化学链燃烧特性研究,并探究了准东煤半焦中碱(土)金属(AAEMs)的迁移转化规律。研究表明,赤铁矿载氧体能够显著提高固定床反应器出口烟气中CO_(2)体积分数,然而随着载氧体与半焦质量比(mOC/mC)不断增加,CO_(2)体积分数先急剧增加而后趋于不变,最佳的mOC/mC为50:1,而700℃热解制取的准东煤半焦经酸洗脱灰处理后固定床反应器出口相应烟气中CO_(2)的选择性降低了8.95%,这表明准东煤半焦中具有催化活性的AAEMs显著影响其化学链燃烧性能。赤铁矿载氧体对准东煤半焦表面AAEMs的分布也有显著影响,与未加入时相比,Na、K元素在半焦表面呈现较为明显的团簇富集,Ca、Mg元素在空间分布上呈更为明显的依赖关系。采用原位气化化学链燃烧方式后准东煤半焦中的AAEMs向赤铁矿载氧体中发生迁移与转化,并生成霞石(NaAlSiO_(4))、钾长石(KAlSi_(3)O_(8))、钙铝黄长石(Ca_(2)Al_(2)SiO_(7))、镁橄榄石(Mg_(2)SiO_(4))等高熔点矿物质,有效抑制了准东煤半焦中AAEMs向气相的挥发。The low-carbon,clean,and efficient utilization of the Zhundong coal is greatly limited by some severe problems such as ash accumulation,slagging,and CO_(2) emissions in the conventional combustion and utilization processes.The adoption of low-rank coal pyrolysis at low and moderate temperatures to produce semicoke,tar,and pyrolysis gas is a leading technology for the utilization of classified coal.Based on the characteristic of high alkali gasification activity of pyrolysis semicoke,the chemical-looping combustion technology is adopted to achieve a low-carbon,clean,and efficient conversion of the Zhundong coal semicoke.The in-situ gasification chemical-looping combustion characteristics of the Zhundong coal semicoke are studied in a fixed bed,in which CO_(2) is selected as the gasification agent and hematite is con-sidered as the oxygen carrier.The study of migration and transformation laws of alkali and alkaline earth metals(AAEMs)in the Zhundong coal semicoke also is performed.The experimental result indicates that the addition of the hematite oxy-gen carrier can significantly improve the CO_(2) concentration of the flue gas at the outlet of the fixed bed reactor.However,CO_(2) concentration increases first and then remains constant with the increase in the mass ratio of the oxygen carrier and semicoke(mOC/mC).The optimal mOC/mC is determined as 50∶1.In this case,the CO_(2) selectivity of the flue gas at the out-let of the fixed-bed reactor is decreased by 8.95 percentage points at the pyrolysis temperature of 700℃after acid wash-ing and deashing treatment,indicating that the chemical-looping combustion performance of the Zhundong coal semicoke can be significantly affected by the catalytic activity of AAEMs in the semicoke.The distribution of AAEMs on the sur-face of the Zhundong coal semicoke is affected by the hematite oxygen carrier.Compared with the absence of the hemat-ite oxygen carrier,more obvious cluster enrichment on the surface of semicoke for Na and K elements is found.An obvi-ous dependency re

关 键 词：准东煤半焦 赤铁矿载氧体 碱(土)金属 化学链燃烧 分质分级利用 

分 类 号：TQ534.9[化学工程—煤化学工程]