循环流化床工业气化炉高钠煤配煤气化

摘要

印尼煤具有良好的气化反应活性,但煤灰分中的Na2O质量分数较高,容易导致系统产生黏结、积灰和腐蚀等问题.利用Na2O-SiO2-Al2O3三元体系相图分析了印尼煤灰的相图特征,选择了掺配煤种并优化了配煤比例,进而在设计给煤量为350 t/d的循环流化床工业气化炉上,以印尼煤质量分数为75％的配煤为原料进行了168 h气化试验,考察了装置的运行特性和配煤的气化特性,并采用扫描电子显微镜和X射线衍射仪分析了气化灰渣的微观形貌和晶相组成.配煤气化试验过程中,炉膛底部温度和密相区压差稳定、无大幅波动,飞灰和底渣无明显变形或熔融现象发生,实现了高钠煤配煤气化的连续稳定运行.冷煤气效率为70.75％,碳转化率为89.49％,煤气热值为5.30 MJ/Nm3.飞灰和底渣中钠长石的衍射峰均较弱,表明钠长石的生成量较少,可有效抑制低温共熔反应的发生.工业气化炉试验验证与三元相图理论分析基本一致.%Indonesia coal shows a good gasification reactivity.However,the high Na2O content in coal ash can induce some serious problems,such as agglomeration,deposition and fouling.SiO2-Al2O3-Na2O ternary phase diagram was used to study the phase diagram characteristics of Indonesia coal ash.The blending coal was selected and the blending ratio was optimized.Blended coal gasification experiment,with 75％ mass percentage of Indonesia coal,was carried out in a 350 t/d circulating fluidized bed industrial gasifier for 168 h.The operation characteristics and gasification performance were investigated.The surface morphologies and phase compositions of bottom char and fly ash were investigated via scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses,respectively.During the gasification process,the temperature and pressure drop for the dense phase of gasifier are very stable,and there are no deforming or melting phenomenon for fly ash and bottom char.Long-term stable operation is achieved by blended coal gasification.The cold gas efficiency is 71.96％,the carbon conversion is 86.90％ and the gas heat value is 5.59 MJ/Nm3.XRD patterns show that the peak intensity of albite is very weak for fly ash and bottom char,indicating the formed albite is quite few and helpful to inhibit the low temperature eutectic reaction.The ternary phase diagram prediction is consistent with the industrial gasification experiment.