碱(土)金属改性赤铁矿载氧体的化学链气化实验研究

Hematite Oxygen Carriers Modified Using Alkali(Earth)Metals for Chemical Looping Gasification

本文以竹子为原料,使用天然赤铁矿作为载氧体,在固定床反应器开展化学链气化实验,探究不同工况下的气化表现.在确定最优工况后,掺杂碱(土)金属离子对载氧体进行改性,探究改性载氧体的化学链气化表现.结果表明:在反应温度为850℃、蒸汽流速为0.1 mL/min、等效系数Φ为0.204时,竹子气化效果最佳,此时合成气产量为0.99 m^(3)/kg,气化效率为63.96%.对载氧体进行改性后,3种载氧体的碳转化率、气体产量和气化效率均得到提升.掺杂碱(土)金属离子后的载氧体中检测到能够增强赤铁矿晶格氧活性的K_(2)Fe_(22)O_(3)4、Na_(3)Fe_(5)O_(9)、CaFe_(2)O_(4)和Ca_(2)Fe_(2)O_(5)等双金属氧化物矿物质,载氧体的比表面积和总孔体积也有一定程度的改善.钾改性的载氧体气化性能最佳,碳转化率、气体产量和气化效率分别提升至84.30%、1.13 m^(3)/kg和72.02%.多次循环后载氧体表面均出现了不同程度的烧结现象,其中钙改性载氧体中低熔点硅铝酸盐的含量较高,且用于改性的CaCl_(2)的熔点也较低,烧结现象最为严重.

Bamboo was used as the raw material and natural hematite as the oxygen carrier,chemical looping gasification experiments were carried out in a fixed-bed reactor to study the gasification performance of hematite under different working conditions.The gasification performance of the oxygen carrier modified with AAEMs was explored when the optimal conditions had been determined.The results showed that the optimal bamboo gasification was achieved at a reaction temperature of 850℃,a steam flow rate of 0.1 mL/min,and an equivalence coefficientΦof 0.204,with a syngas yield of 0.99 m^(3)/kg and a gasification efficiency of 63.96%.The carbon conversion,gas yield,and gasification efficiency of the three oxygen carriers after modification were all improved.Bimetallic oxide minerals such asK_(2)Fe_(22)O_(3)4、Na_(3)Fe_(5)O_(9)、CaFe_(2)O_(4),and Ca_(2)Fe_(2)O_(5),which can enhance the oxygen activity of hematite lattice,were detected in the doped alkali(earth)metal ions,and the specific surface area and total pore volume of the oxygen carriers were improved to some extent.The potassium-modified oxygen carrier had the best gasification performance,with the carbon conversion,gas yield,and gasification efficiency improved to 84.30%,1.13 m^(3)/kg,and 72.02%,respectively.Different degrees of sintering were observed on the surface of the oxygen carriers after several cycles,in which the calcium-modified carriers,with a higher content of low melting point silica-aluminate and a lower melting point of CaCl_(2) used for modification,showed the most serious sintering.